ee ha SB ES tt oN a te a BA ko Ae dl fall i inne Si es Ie it tate a BR RL Rh eee ee EEA A eK Re one Dei eee +o 8 aS! * ‘ ‘uk >t peer “ i > t a 4 Tales! / <, Sie Perak | ; f r Ne She 8 , h - y . ” ” iJ 2 : ¥ wre . i ’ . ‘ 4 t : oh . r Fi r i f a + ‘ + . uA : f + ‘ : ‘ * 4 * ? ‘ t y ad Beanies ‘ 7 : ead f iy pl ye 1 Mia iv Midis yah oud i, “7 i i | Gr ites rata tale a3 He f eat Bui ie Pie : pitas Wa inn nt a‘ ’ he!) Wee) ‘cw RE Ps Se — ee a a 2 “CANE SUGAR. BOURBON. CANE SUGAR A TEXTBOOK ON THE AGRICULTURE OF THE SUGAR CANE, THE MANUFACTURE OF CANE SUGAR, AND THE ANALYSIS OF SUGAR-HoOUSE PRODUCTS BY NOEL DEERR DEE SECOND (REVISED AND ENLARGED) EDITION ; LIBRARY NEW YORK BOTANICAL «. GARDEN LONDON : NORMAN RODGER 2 St. DuNSTAN’s HILL zG.3 1921 ALL RIGHTS RESERVED, INCLUDING THE RIGHT OF TRANSLATION INTO SPANISH PREFACE ? The present edition of “CANE SUGAR ”’ now offered to the public has been completely rewritten, preserving at the same time the general arrange- ment followed in the first edition. During the ten years that have passed between the issue of the two editions the writer has had the benefit of extensive experience in Cuba and in a New York refinery. The period he spent in America has been of special value, since it afforded the opportunity of systematically examining the collections of technical literature to be found in the great libraries of the western republic. While these may be no more complete than those accumulated by the elder civilization, the facilities afforded for research in the way of accessibility, card catalogues and cross-references add very much to their value. In preparation for the present edition, the writer made a survey of patent specifications dealing with sugar and sugar machinery, and much material thus found has been included ; and, although objection may be made to the inclusion of bygone matters in a textbook intended for present- day use, an account of the development of the train of thought in invention is not without an immediately utilitarian value. Of the patent files con- sulted, those of the British Patent Office have been the most adopted, as the system of arrangement and of, indexing there employed is far superior to that used by the Patent Offices either of France or of the United States of America. My thanks are due to many friends for help and criticism. In addition to those whose services have already been acknowledged in the first edition, I have now to thank Mr. Jas. HAMILL, who read in manuscript those chapters more especially dealing with machinery ; Dr. C. A. BRowneE for criticism of those parts bearing on sugar analysis; Dr. C. A. BARBER, C.I.E., whose specialized knowledge of the cane in its botanical aspect has saved me from sundry errors; Dr. E. J. Butier, C.I.E., who checked the proofs of Chapter IX on the Pests and Diseases of the Sugar Cane; and Mr. JAmeEs P. Ocitvie, A.I.C., who read through the last ten chapters and made some suggestions in the text. NOEL DEERR. Bombay, April, 1921. iil CONTENTS PAGE CHAPTER [| (he Gane on a0. 02 > Sens ea eh 1 CHAPTER II The Composition of. the Sugan: Cane je j= 40-09 ees eo eee 12 CHAPTER III Rangevand. Chmate.< <.8" =: teeta ete eee ee 19 CHAPTER IV Variation: in, the. Cane“and Gane. Varieties’: = ..-) 4. =o 4.342 ae 31 CHAPTER V The Soils of the Cane-Growing Regions eh ie 3 = 7 ae ri 64 CHAPTER VI The ‘Manuring’ of- the “Came* ** 0) = Se5 Sek ieee 79 CHAPTER VII The Irrigation of the Cane a Ce a te ES Se CHAPTER VIII The, Husbandry: of the Gane 9-) ~-=.-°-" 7-9 (=). (=) == CHAPTER IX The. Pests and Diseases. of ‘the Cane. "=" - =9 “ss ie CHAPTER X The Harvestme,ol-the:Cane = 9- +. - 9 -). =.= 22" ee CHAPTER XI The Extraction of the Juice by Mills - - - - - - = 385 CHAPTER XII The Diffusion Process Oe ag 2 - - - - - = aed 251 CHAPTER XIII ‘ The Action of Heat, Alkalies and Acids on Sugars and Cane Juices - 257 iV CONTENTS CHAPTER XIV The Defecation of Cane Juice aa Nee CHAPTER XV Carbonation Processes = = = = s CHAPTER XVI Selpartation j= (tis) =e Se CHAPTER XVII Filtration € z 2 = 4 % x e CHAPTER XVIII EipaporsiuGi=- <= 9 sty = 2 Se en SS ; CHAPTER XIX Sugar Boiling and Crystallization-in-Motion - CHAPTER XX The Separation of the Crystals = oh a eS CHAPTER XXI Ieaweoupar i = = 6 Se Se CHAPTER XXII Molasses = - = Ee & 2 : h CHAPTER XXIII Bagasse as Fuel and the Steam Generating Plant of the Cane Sugar ee ee ee CHAPTER XXIV ii Pe oldrineter << = = st SK CHAPTER XXV The Determination of Cane Sugar and the Assay of Sugar-House Prg@duets; 2-5 nr aad ee ge =. ol CHAPTER XXVI The Determination of Reducing Sugars - CHAPTER XXVII The Control of the Factory - 2 = 2 CHAPTER XXVIII Fermentation with special Reference to the Sugar House Js TEPES BUS DUD on saat CAEP es ta ee el Ie ac eee Geen oie Cee, ee RG fa EN Bb a 454 473 Ces es ae sr 4e aS sae 1 i G . - ‘S tae NY ae a Tr. rv owe Ce ELISE OF PLATES Frontispiece : Bourbon Cane. I. IT. III. XV. XVI. XVII. XVIII. XIX. XXI. XXII. XXIII. XXIV. XXYV. XXVI. XXVII. XXVIII. XXIX. Creole: Cane apace ft AS us Alok eslese.. = Rose Bamboo Cane Purple Bamboo Cane Striped Bamboo Cane White Tanna Cane Se ee aig Be Sees Stuped Bus distisek-= Cooling Tower for Water in Cuba - - - Spraying System for cooling Water in Cuba - Appeatimte of Measisn:5 iis. spsdlisiveitN + Sporulation of Yeasts - - - - - = Vii ' i} i) ' ‘ ' TO FACE PAGE ) 17 ABBREVIATIONS USED IN THE REFERENCES IN THIS VOLUME Agric. Agriculture, Agricultural. Ann. Bot. Annals of Botany. Ann. Chim. Phys. Annales de Chimie et Physique. Ber. Berichte der deutschen chemischen Gesellschaft. Bull. Bulletin. é Bull. Assoc. Chim. Suc. Bulletin de l’Association des Chimistes de Sucrerie et de Distillerie. C.R. Comptes rendus hebdomadaires des Seances de l’Academie des Sciences. Chem. News. The Chemical News and Journal of Physical Science. Deut. Zuck. Die deutsche Zuckerindustrie. Ent. Entomological. H.S.P.A. Ex. Sta. Hawaiian Sugar Planters’ Association Experiment Station. Haw. Pi. Mon. Hawaiian Planters’ Monthly. Int. Sug. Jour. International Sugar Journal. Java Archief. Archief voor de Suikerindustrie in Nederlandsche Indié. Jour. Agric. Sc. Journal of Agricultural Science. Jour. Am. Chem. Soc. Journal of the American Chemical Society. Jour. Chem. Soc. Journal of the Chemical Society. Jour. Econ. Ent. Journal of Economic Entomology. Jour. Fab. Suc. Journal des Fabricants de Sucre. Jour. Ind. Eng. Chem. Journal of Industrial and Engineering Chemistry. Jour. prak. Chem. Journal fiir praktische Chemie. La. Ex. Sta. Louisiana State University Experiment Station. La. Plant. The Louisiana Planter and Sugar Manufacturer. Phil. Mag. The London, Edinburgh and Dublin Philosophical Magazine. | Proc. Proceedings. S.C. The Sugar Cane. Siew enies: Soe. »society. Trans. Transactions, U.S. Dept. Agric. United States Department of Agriculture. W. Ind. Bull ‘The West Indian Bulletin Zeit. fuy Instr. Zeitschrift fir Instrumenkunde. Zeit. phys. Chem. Zeitschrift fiir physikalische Chemie. Zeit. Riben. Zeitschrift fiir Riibenzuckerindustrie. Zeit. Ver. deut. Zuck. Zeitschrift des Vereins der deutschen Zuckerindustrie. Zeit. Zuck. Bohm. Zeitschrift fiir Zuckerindustrie in B6hmen, vill Pam e.(l, CREOLE: ee FPF Fe er PE er, MAY 1¢ lev LIBRARY NEW YORK BOTANICAL GARDEN CANE. SUGAR CEA EER < THE CANE THE sugar cane is a perennial grass, the cultivation of which is confined to the warmer regions of the earth. In all probability it is of palzo-tropical origin, and Eastern Asia is usually assigned as its home by economic botanists. Nevertheless the cane was found growing in Polynesia by the first European visitors, and also in the Hawaiian Islands. Ethnologists assert that these islands were settled from the South Pacific at a very early date, the native legends confirming this assumption. As it is probable that these early voyagers brought the sugar cane along with them, the presence of the plant in the South Pacific at a very remote time would be indicated, and it would then appear that the cane is indigenous equally to the South Pacific as to Eastern Asia. This suggestion is made more probable when the very marked difference in habit between the Indian canes and those of Otaheite and other Polynesian islands is remembered. That the sugar cane is indigenous to Polynesia was probably first suggested by Sagot and Raoul in their ‘‘ Manuel pratique des Cultures Tropicales,” Paris, 1893. Their conclusion is based on observation in that locality, on Maori legend, and on the presence of a Saccharum violaceum in the island of Rurutu near Otaheite, this last island receiving its name from the name of the cane. The cane plant is made up of the root.and root stock, the stalk, the leaf, and the inflorescence. The structure and function of these different parts are described below. The Stalk.—The stalk of the cane is roughly cylindrical, and in some varieties is swollen between the joints, giving the internodes a barrel shape. Its size differs not only with variety, but also with conditions of growth. The diameter lies between a minimum of 0°5 inch to a maximum of 3 inches. The smallest diameter is found in the reed-like canes grown by the ryots of British India and classed by Hadi! as Ukh canes. Of the canes cultivated elsewhere, that with the smallest diameter is the Uba cane, itself probably of Indian origin. The greatest diameter is found in the Elephant cane of Cochin China, which is not, however, a commercial variety. Of the older cultivated varieties, the Tanna canes are of greater and the Java or Batavian f less diameter, the Otaheite cane being intermediate between these two. The length of the stalk under the most favourable conditions may exception- ally attain to as much as thirty feet, but an average length of twelve feet is z B 2 CHAPTER! typical of a well-grown crop. Similarly, the weight of an individual stalk will reach a maximum of fifteen pounds, the average weight in a well-grown crop being six to seven pounds. In the early stages of the cane’s growth it is erect, and in some varieties, as for instance the Tanna canes, it remains so throughout the whole period of its growth ; in others, as the Otaheite, its habit is recumbent, and in such cases the cane is said to “ lodge.”’ The stalk is made up of a series of joints or internodes, f (Fig. 1), separated from each other by the nodes e. Generally the internodes grow in a continu- ous line, but occasionally they are more or less zigzag. The node is usually of somewhat greater diameter than the internode and in some varieties is notably swollen. The length of the internode will exceptionally reach 10 inches, but a length of 6 inches is typical of Otaheite cane grown under favourable conditions. The Tanna canes are an example of a cane short-jointed in proportion to diameter, the Uba cane and the seedlings B 147 and P.O.J. 100 being types where the length is great compared with the diameter. The length of the joint is, however, influenced by leaf development, by drought or by cold weather, by soil conditions or by disease. The number of joints may be as few as twenty or as manyas eighty. Ateach node and alternately OWN ins 1 : N\ at opposite sides is an embryo cane known as the eye or bud, b (Fig. 1). It is the size of a pea or larger, and may be triangular, pointed, oval or hemispherical in shape. In some varieties the eye is very swollen and prominent. From the eye and running upwards appears a channel in the stalk ; this channel may be well marked, or in some cases may tend to disappear. Immediately above each joint appear from one to three rings of semi- opaque whitish spots (7) ; here is the zone of adventitious roots, each spot being an embryonic root. The bloomband is shown at DJ, the leaf-scar at J, and the growth ring at gr. The eyes or buds serve to reproduce the cane by means of asexual propagation. Simultaneously the adventitious roots develop and serve to feed the plant until it has developed a root system of its own. In some varieties the eyes have a tendency to sprout while still attached to the parent plant, and the sprouting will always occur when the top of the cane or the vegetative point is removed or destroyed by insects or by disease. Similarly the adventitious roots may develop, forming a mass of aerial roots; this development is one of the symptoms of the “sereh ”’ disease. Self-coloured canes are green, yellow or some shade of red, varying from pink to deep purple. Where sun-exposed, the colour may be so developed as to give a blotched or marbled appearance. Striped or ribbon canes are THE CANE 3 due to the development or absence of colouring matter in streaks running lengthwise with the stalk. Thus with a diminution of chlorophyll in stripes in a yellow cane, a green and yellow ribbon cane results; similarly, green and red, and yellow and red canes are known, and also varieties striped in two shades of red. The last case may occur in a cane with an even dis- tribution of the red colouring matter, anthocyan, overlying strips of chloro- phyll the colour of which is masked. Perhaps all arrangements possible from every combination of the three colours may occur. From striped canes self-coloured sports frequently occur, and this subject, which is of considerable economic interest, is discussed more fully in Chapter IV. Structure of the Stalk.—On cutting across a cane it will be seen that it consists roughly of three parts, a hard outer rind, and a mass of softer tissue in the interior, interspersed with fibres, the latter being more frequent about the periphery of the stalk. The rind is made up of a thick epidermis with a strong outer cuticle, often with a thick layer of wax outside, impervious to water, and a layer of thick-walled cells; the function of the cuticle is to prevent evaporation of water from the stem of the cane, and to protect the softer interior parts from mechanical injuries; the layer of thick-walled cells gives ngidity and strength to the stem. These thick-walled cells gradually pass into the thin-walled cells of the ground tissue, or parenchyma, which serve to store up the sweet juice of the cane. The fibres are known as the fibro- vascular bundles; they consist of the wood vessels, sieve tubes and companion cells, surrounded by thick- walled fibres. A cross-section of the cane, after Cobb?, as seen under the low power of a microscope, is shown in Fig. 2. It consists of :—z. The epidermis, with thick cuticularized walls. 2. Thick-walled ground tissue of the rind. 3. A small vascular bundle; these are found mainly in the outer portion of the stem, and their function is chiefly mechanical. 4. An inter- mediate bundle with two vessels and a few thin-walled phloem elements. 5. Thick-walled fibres; these are the mechanical elements of the bundles, and are more numerous in the bundles towards the outside. 6. Thin-walled cells of the ground tissue or paren- chyma. 7. A large vascular bundle found toward the centre of the stem. 4, i i oa: = In Fig. 3 is shown more highly magnified a bundle corresponding to 7 in Fig. 2. I is a vessel with unbordered pits; 2, an annular vessel; 3, a sieve tube with the companion elements making up the phloem; 4, an intercellular air space; 5 and 7, thick-walled mechanical elements, the fibres, or sclerenchyma, forming a sheath around the bundle; and 6, ground tissue or parenchyma. When seen in longitudinal section the cells of the parenchyma are found to be rather longer than wide. 4 CHAPTER I The sieve tubes seen in longitudinal section are observed to be very elongated vessels, with perforated partition walls at intervals in their length ; the vessels are continuous throughout their length. In the internodes the fibro-vascular bundles run parallel, but at the nodes they freely branch and communicate with each other, and pass on into the leafbud and next internode, descending right into the roots of the cane. Function of the Stalk.—The stalk serves in the economy of the plant in three ways. First of all, as a mechanical structure it supports the leaves and inflorescence ; secondly, the fibrovascular system is charged with the duty of transporting water and food material from the roots to the leaves and carrying back to the stem the products of metabolic change formed in the leaf; thirdly, the parenchymatous cells receive the material so elaborated, which is there stored, or else used up as a source of energy by the growing plant. Physiology of the Stalk.—In the life history of the stalk the following phases are distinguished :— I. In very young parts of the stalk only starch or albumen is present, which is con- sumed little by little in the formation of cellulose. 2. In young, rapidly growing parts of the stalk, the cane sugar brought down by the leaf is inverted, and whereas in the leaf the proportions of sucrose, glucose, and fructose were as 4:2:1, in the young joints the proportions are 0°8:1:1. A part of the invert sugar is used up in the for- mation of fibre, a part unites with the amides to form albumen, and a part is deposited as starch. In consequence of the inversion, the osmotic pressure is raised and this tends to favour the absorption of plant food. 3. In older joints the sucrose formed in the leaf remains unchanged when it reaches the joint, and the reducing sugars are used up, partly in respiration, or, perhaps, are partly converted by a reverted enzyme action into sucrose. 4. When the stalks are developed, the accumulated invert sugar is converted into sucrose; of the reducing sugars remaining the glucose is generally in excess. 5. When the stalks are ripe the leaves die and the accumulation of sugar gradually ceases; the remainder of the reducing sugars is changed to sucrose, eventually only traces remaining. 6. When the stalks are over-ripe the sucrose in the older joints is partly inverted, but this change does not prevent the younger parts of the cane accumulating sugar. The Leaf.—The leaves of the cane are alternate and opposite, one at each joint ; actually, the Jeaf consists of two parts, the leaf sheath and the leaf blade. The leaf sheath springs from the node. It completely embraces, at its base, the stalk, and gradually recedes from it ; the sheath is colourless THE CANE 5 or pale green, and about 12 inches long at maturity. The blade is from 3 to 4 feet long, and 2 to 3 inches wide; in colour the leaves are varying shades of green; in some varieties variegated or entirely white leaves are often developed. Some canes (S. violaceum) have purple leaves. The leaves taper towards the top, and are delicately serrated along the margin; in many varieties sete or hairs abound at their base. The leaf is traversed longitudinally by a number of veins. The midrib is generally white, but sometimes reddish or purple, and is formed with a channel-like depression in its upper surface. Leaves at maturity fall away from the stalk, and in some varieties separate themselves entirely. Structure of the Leaf—In Fig. 4 is shown a cross section of a leaf of the cane, to which must be added Dr. Cobb’s explanation of the plate.? “‘ Cross-section of a portion of healthy cane leaf taken half-way between the midrib and the margin near the middle of a full-grown but not yet fully lignified leaf. The upper side of the figure, 1 to 18, represents the top surface of the leaf. The fructifications of the leaf-splitting disease occur in positions corresponding to 3,4, 5. The green chlorophyll bodies are here shown black. It is owing to the destruction of these green bodies in portions of the leaf such as here represented, namely, between the largest vascular bundles, that the leaf takes on a striped appearance. The part of the leaf to be examined was fixed with the vapour of osmic acid while still attached to the cane plant. The fixed portion was differenti- ated into glycerime and cut in that condition. The drawing was projected from a photograph and sketched. The details were drawn in from the examination of sections either unstained or stained with aniline safranin. The section shows five fibro-vascular bundles, the largest of which is indicated at 6 to 11, the smallest at 23 and 32. Portions of the other two, which are intermediate in size, are shown at 19 and 36. None of these bundles are of the largest size. Bundles fully twice the size of the larger here shown occur in the cane leaf, and such large bundles are characterized by the possession of annular vessels, none of which occur in these smaller bundles. Throughout the illustration structures of the same class are indicated by a similarity in the draughtsmanship ; thus the woody cells indicated 6 CHAPTER I at 9 are repeated in various parts of the figure, more particularly next to the epider- mis of the lower surface. ‘“t, a set of so-called motor cells, in this instance composed of two cells, whose nuclei are pointed out at 2 and 3; 4, an internal cell of somewhat similar character to that pointed out at 1, 2, and 3; 5, another cell of the same class cut in such a way that the nucleus has been removed ; 6, sclerenchymatous cells imparting strength to the fibro-vascular bundle ; 7, one of the layer of parenchymatous cells rich in chloroplasts and immediately surrounding each fibro-vascular bundle ; 8, one of the stomata, found more rarely on the upper than on the lower surface of the leaf ; 9, woody cells imparting strength to the cane leaf, and occurring on the dorsal and ventral side of each fibro-vascular bundle ; 10, one of the celis constituting the sheath of the vascular bundle—these cells contain chloroplasts arranged along the outsides of their walls; 11, tracheal vessel; 12, one of the cells of the upper epidermis ; 13, nucleus of a similar cell ; 14, upper cuticle at its usual thickness ; 15, a two-celled hair on the surface of the leaf; 16, thinner cuticle of the upper surface of the leaf as it occurs over the so- -called motor cells; 17-18, group of so-called motor cells, consisting in this case of four cells ; I9, fibro-vascular bendle- of intermediate size; 20, chloroplast in one of the cells of the lower epidermis ; 21, one of the stomatic openings that are abundant on the lower surface of the leaf ; Le y) al this one is closed—-an open one may be seen at 25-26; 22, accessory (?) cell ot the stomatic opening ; 23, one of the smallest fibro-vascular bundles ; 24, one ofa group of cells very rich in protoplasm, which extends between the vascular bundles——the nearer these cells are to the lower epidermis the denser their protoplasmic contents ; 25-26, protoplasts in the guard cells of the stomatic opening ; 27, one of the sieve tubes—among these sieve tubes may be seen the smaller contpanion cells and their protoplasts ; 28, extra chlorophyl!-bearing cells outside the single layer surrounding the vascular bundle ; 29, lip of one of the stomatic guard cells; 30, cell rich in protoplasm, of the same class as 24 ; 31, nucleus of one of the companion (?) guard cells ; 32, fibro-vascular bundle of small size; 33, apparently a locule in the thickened portion of the wall of the stomatic euard cell; 34, entrance between the guard cells of the stomatic opening ; 35, cuticle of the lower surface of the leat ; 36, fibro-vascular bundle of intermediate Size } 37, 37, 37, air chambers immediately above the stomatic ea a Throughout the illustration the nuclei are shown grey, and the nucleoli black. The tissue represented at 24 and 30 is probably primary leaf-tissue, from which during the growth of the leaf the various tissues represented have been differentiated.” In Figs. 5 and 6 are shown, after Dickoff,? the upper and under side of the leaf highly magnified, the legend being as under :—1, long cell; kz, silica cell; kr, cork tissue cell; hm, stoma; be, air cell; h, hair; st, spine. THE CANE ; Function of the Leaf—The leaf is the manufactory of the plant in which the processes of metabolism mainly take place. To begin with, the green tissues of the leaf take up carbon dioxide from the air through the stomata, which in combination with the water transported by the roots and vascular system forms carbohydrates, oxygen being returned to the atmosphere. At the same time nitrogenous bodies are formed through the union of the carbohydrates with the nitrates brought up dissolved in the soil water. The compounds so formed are also transported to other parts of the plant, mainly the stalk. A third function of the leaf is the transpiration of water which takes place through the stomata. Physiology of the Leaf—The physiology of the cane leaf has been studied mainly by Went* and by Kamerling® in Java, the latter extending and modifying some of the conclusions reached by the first named. It appears that cane sugar is the first product of metabolism occurring in the leaf, jg Ne LG Balt ; ‘ (a but if more carbohydrate is formed than can be transported to the stem, then the excess appears as starch, which is stored during the daytime in the chlorophyll granules. During the night, or even on a cloudy day, the starch is converted into reducing sugars, and in this form is transported to the stem. The presence of large quantities of starch can be demonstrated in leaves cut just before sundown, and, conversely, its almost complete absence can be shown in leaves cut just before sunrise. At the same time an increase amounting to 13 per cent. takes place in the weight of the leat during the daytime, this increase being lost during the night. Similarly the greater part of the growth of the stem takes place during the night. The Root System of the Cane.—On planting an eye of the cane, germina- tion takes place and a single mother stalk forms. The underground portion of the stalk forms itself into a rhizome or woody short-jointed prolongation of the stalk containing at each node a dormant eye. As growth proceeds 8 CHAPTER I new shoots form from this rhizome until the whole stool of cane is formed. ao It is possible, too, that in the first year’s | Ly growth the shoots formed from the first WA original rhizome may send out shoots meh Dares from the rhizomes that they themselves form. On cutting down the stalks at harvest the underground portion of the plant is stimulated to send out shoots from the dormant eyes and the first vatoon crop begins. This process may be repeated indefinitely, the limit of successive crops from one planting being very great. In this process, the original Pi ae thizome does not necessarily die when lic. 7 wa i Ze the first stalk is cut, and third, fourth R2. R? or even later ratoon crops may contain 2na Rut Lg ed every 7 days: stalks still springing from the rhizome formed trom the original cutting, but the tendency is for the older parts to die away. Fig. 7 shows, after Auchinleck,® a combination of rhizomes as found in a ratoon crop. The roots of the cane spring from the nodes of the stem ; they are fibrous, lateral, and very deli- cate; they ramify in all directions, generally ex- tending from 18 inches to 3 feet from the stem. Stubbs’ says that the roots do not penetrate very deeply, but Ling Roth® mentions roots extending as far downwards as 43 feet, THE CANE 9 and Liversedge® states that he has seen roots as far down as 8 or Io feet. The depth to which roots penetrate, however, depends largely on the nature of the soil; they extend furthest in light porous soil. In seasons of drought the roots extend downwards following the water level; on the other hand, in fields with a sour, ill-drained subsoil, the roots after penetrating downwards turn back on themselves to the upper surface soil. The cane has no tap root, and its roots have comparatively little held on the soil. Fig. 8, after Agee, shows the development of the rect system as found on irrigated soil in the Experiment Station at Honolulu. WA wai Vynin ii Fic, Io Structure of the Root.—In Fig. g is shown to a scale of 14 the end of one of the roots growing in that part of the stem of the cane below ground. Towards the end of the root are seen numerous very fine hairs, and at the extreme end is seen the root cap. In Figs. 10 and 11 are given longitudinal and cross-sectional views of the root, the longitudinal view being taken through the apical point ; rc is the root cap, m is the layer of meristematic tissue, rh root hairs formed from the piliferous layer on the extreme outer layer of the root ; cor is the cortex, st the central cylinder, v a developing wood vessel, and x a larger wood vessel. The root cap on the exterior consists of dead cells, and is continually being renewed from the interior by the layer of meristematic tissue from 10 CHAPTER I ay 4 which also arise by a con- i! tinual process of cell sub- nS Hees Ph division all the other oo E tissues of the root. yO WAR a Function of the Root.— eee pee The functions of the root r are two-fold: the root hairs closely envelop par- ticles of soil, thereby maintaining the hold of the plant on the soil, and, secondly, the root < f gj hairs absorb water and tee Te44—_ plant food from the soil and transmit it to the other parts of the grow- ing plant. Soe. IF Roe ¢ My »y res It % D aes SEY OU ro D Xm The Flower.—The in- florescence of the cane is Sy a panicle of soft silky Ny spikelets, borne on the end of an elongated ped- uncle, called the arrow, arising from the terminal vegetative point of the cane. \ \ : 2 : : In Fig. 12 is given a drawing after Cobb,? enlarged 30 diameters, of a single flower of Lahaina cane. At I is the ovary, the growth of which produces the seed ; it is ovoid and sessile. From the ovary pro- ceed two styles of a reddish colour, bearing the plumose stigmas, 2. At 3 are the three anthers which pro- duce the pollen, that serves to fer- tilize the stigmas ; at 4 are the two lodicules, the function of which is, by swelling at the proper time, to open the cane blossom; at 5 is the innermost palet of the cane flower, and at 7, 6 and 8 the remaining palet and the glumes; at g are the Say bristles that surround the base of the flower. It is only exceptionally that the cane forms fertile seed. Some varieties never flower, and others do so only in the tropics. The age at which the cane flowers varies from eight to fifteen months, and is de- pendent on variety and climate and also on the time of planting. Flower- ing takes place at certain definite THE CANE II times of the year, varying in the different cane-growing regions, and if thecane is not sufficiently mature at the flowering time in its first year, no formation - of flowers occurs until the second year. In this way a delay of a few weeks in planting will retard flowering for twelve months. The pollen grains magnified 360 times are shown in Fg. 13, after Will- brink and Ledeboer®; @ isa ripe pollen » grain, shown also germinating at b; ¢ and d are young unripe pollen grains ; k is the germ pore; the exine is shown at e and the intine at 7. The pollen grains are small yellow, nearly spheri- cal bodies ; the outer wall, the exine, is of cork tissue and has an opening, k, the germ pore. The inner wall, the intine, is of pure cellulose and has no opening. When ripe the interior of the pollen grains are filled with starch: and are opaque, but when unripe the interior is bright and transparent. REFERENCES IN CHAPTER I ‘The Sugar Industry in the United Provinces of Agra and Oude.” BS Peay Bx, Sta.) Path? Ser, Bull. 2. Van Deventer’s ‘‘ De Cultuur van het Suikerriet op Java.” Java Arch., 1896, 4, 525. Java Arch., 1904, 12, 772; 1905, 13, 306. Agric. News, 1914, 13, 231. Stubbs’ ‘‘ Sugar Cane.” Newlands’ “ Sugar.” Van Deventer’s ‘‘ De Cultuur van het Suikerriet op Java,” p. 62. CHITA YD A CHAPTER IT THE COMPOSITION OF THE SUGAR CANE In writing of the composition of the cane, distinction must be made between the stalks and the whole plant, including therein the leaves, tops and underground system. The composition of the former is of major interest to the manufacturer, while the agriculturist is more concerned with the composition of the whole crop. Distribution of the Crop as between Stalks and Leaves.—A very complete account of the distribution of the crop as between stalks on the one hand ~ and tops, leaves, and dead cane on the other, was made by Maxwell" in Hawaii in connection with a number of varieties. Excluding certain abnormal figures, the dry matter in the stalks amounted to 45 per cent. of the entire crop, the leaves, etc., accounting for 55 per cent. This analysis of the crop did not take into consideration the root system, which Kobus has estimated at two to three tons of dry matter per acre, whereby the pro- portion of dry matter in the stalks would be reduced to the neighbourhood of 40 per cent. of the entire product. Composition of Different Parts of the Cane.—Analyses due to Agee and Halligan? of Louisiana cane gave the results below :— STALKS Roots SEEDS LEAVES percent. percent. percent. percent. Water s< see ae 74°96 68-79 II*03 74°38 Ash as ae oF 0: 64 1°87 5°22 2°23 Fat and Wax .. bs 0: 38 O° 54 2°O1 0-69 Nitrogenous bodies 0:58 1°59 8°47 I*70 j Crude cellulose 4°86 9°58 25°51 9°18 Fibre Pentosans 3°04 7°04 26°26 5°49 Ligneous bodies 2°14 4°25 21°50 4°13 Sugars, etc. oe 13°40 6°34 — 2°20 Combining these results with those quoted in the preceding section, it is easy to see that the very great part of the material removed from the soil is contained in that part of the crop which remains on the land. The Quantity of Sugar in the Cane Stalks.—The sugar in the stalks varies between very wide limits and is affected by variety and by conditions of growth. The earliest analyses made were those of Casaseca* in Cuba, and the classical analysis is that due to Payen,* who, working on material sent to France from the West Indies, and in the absence of a polariscope, found the percentage of sugar to be 18. Other early French workers obtained similar results, the maximum recorded being 26 per cent. It is unfortunate 12 THE COMPOSITION OF THE SUGAR CANE 13 that these results have been copied from book to book right down to the immediate present as general averages. In respect to single canes, the composition will be found to lie within the limits :—Water, 69 to 75 per cent.; Cane sugar, 7 to 20 per cent.; Reducing sugars, o to 2 per cent.; Fibre, 8 to 17 per cent.; Ash, 0-3 to 0-8 per cent. ; Organic non- sugar, 0-5 to I per cent. The upper limit of 20 per cent. for cane sugar is only reached in exceptional cases, and has but once been found by the writer in the analysis of stalks selected for special purposes. Taking crop averages, very great differences between different districts are to be observed. In the Hawaiian Islands for the years 1g08 to IgI5 the average sugar content of the whole crop was 14-18 per cent. On the island of Maui, where the crop is almost exclusively irrigated Lahaina cane, the sugar content over the same period was 15°49 per cent., the extremes being 14-94 per cent. and 16-00 per cent. The highest plantation crop average was 16-61 per cent., and the highest weekly average on a plantation was 18-24 per cent. On the island of Hawaii, where the crop is almost entirely Yellow Caledonia cane grown under natural conditions, the average for the stated period was 13-26 per cent., with extremes of 13-92 per cent. and 12-72 per cent. Statistics from Java are very complete. The figures for the years 1906 to I9gI2 gave 12-50 per cent. as the crop average over the whole of Java, with extremes of 12°16 per cent. and 13°1I percent. Individual plantations show extremes varying from under Io per cent. to over 15 per cent. For the year 1914-15 the average sugar content of the cane harvested at 151 mills in Cuba was 12-98 per cent., the extremes recorded being 10-0 per cent. and 15-3 per cent., both occurring on very small plantations. Statistics from 34 Mauritius factories for the year IgI4 gave an average of 13-36 per cent., with extremes of 12-73 per cent. and 14-97 per cent. Of the other large cane-growing districts, the occasional records that appear from Peru indicate that the cane grown there under irrigation equals that in the most favoured parts of the Hawaiian Islands. Australia is another country where cane of high sugar content is found. At the other extreme may be placed the widely separated districts of Argentina, Louisiana, and Demerara, where a sugar content of 11-5 per cent. is probably above the crop average. The percentage of sugar in the cane though to a great extent dependent on variety is also affected by conditions of soil and climate. Accepting the identity of the varieties known as Bourbon, Lahaina, etc. (cf. Chapter IV), attention may be directed to the very great differences in composition observed between these canes as grown in Hawaii and Mauritius, and in Demerara. As varietal differences when conditions of growth are constant, the case of the Lahaina and Yellow Caledonia canes in Hawaii may be cited, the former containing at least a percentage more of sugar than the latter. Among older canes of repute as of high sugar content may be quoted the Otaheite and the light and dark coloured varieties of the Java or Cheribon canes. To these may be added the recently introduced Badilla cane grown to some extent in Australasia. At the other extreme come such canes as the Cavengerie, the Salangore and the Elephant cane. Of the seedlings, many have been selected on a sugar-rich basis, and of these there are D74 ; P.O.J.100; B208; Hio. Others, such as D625, D1135 and Bouricius 274, though not of high sugar content, remain in cultivation because of other desirable characteristics. 14 CHAPTER II Distribution of Sugar in the Cane.—By far the most detailed analyses of the cane, joint by joint, are those that have been made by Went® in Java. One series of his analyses of ripe twelve-months old plant cane is given below :— COMPOSITION OF THE CANE JOINT By JOINT (WENT). Number | Weight | Sucrose |Reducing| Number | Weight | Sucrose | Reducing of the Sugars of the Sugars Joint. Grams. | per cent. | per cent. Joint. Grams. | per cent. | per cent. I 72°0 I2°1 0:6 17 78+5 17°3 0°25 2 gI-O 13-0 0-5 18 74°0 I7°5 0+ 26 3 110-0 137, 0-6 19 65°5 D7A) OFi27 4 120:0 I4°0 Or5 20 61:0 17°8 0+ 26 5 118-0 14°8 Or5 21 62°5 17°4 0+24 6 IT4*5 TAS 0°45 22 58-0 L720 0°23 i 104°5 15°2 O-4 2 S5y9 I7°*I 0°24 8 102-0 I5°4 O*4 24 43°0 16:8 0:28 9 81°5 15°8 0° 33 25-26 64:0 15°7 0*29 10 73°0 16:3 0° 33 27-28 44°0 13°5 0°27 II 84°5 16°2 0°35 29-30 37°5 13°0 0*29 12 81°5 I6+5 O° 34 31-33 43°5 II*6 O*4 13 82-0 16° 4 0+ 30 34-36 37°0 9:9 0-6 14 76-0 17° O-2 37-45 43°5 5: % 0:8 15 82°5 72 0-29 || Average 74°77 15°31 0: 38 16 84°5 17°2 0°24 || The variation in composition of the juice in the nodes and internodes is shown in the following analyses due to Boname’ :— Sugar, per cent. rie 13°34 12°74 16°73 Nodes Reducing Sugars, per cent, ae 0:29 0-28 0°31 : Sugar, per cent. “ic I16*51 16:80 19°72 EE Reducing Sugars, per cent. .. 0:60 0:84 0 48 Stubbs® gives the following as the result of analyses of twenty stalks of purple cane :— Reducing Brix. Sugar. Sugars. Non-Sugar. Fibre. per cent per cent. per cent. per cent. Nodes Fics 1n}oreyr I2°6 0°13 3°21 16°5 Internodes .. 17°40 15°5 0°94 0:96 8-0 The great variation in composition of the juice at nodes and internodes is well shown in the examples quoted above, whereby an explanation is given of the decreased sugar content of the juice afforded by the later mills in a train, the more woody parts only yielding their juice at higher pressures. The matter is further discussed in Chapter XI. The Proportion of Sugar to Solids in the Cane.—The juice extracted in hand mills from selected individual canes sometimes shows a purity as high as 97. This juice comes, however, almost entirely from the pith cells and does not represent an average. In the case of crop averages, the purity of the “‘ mixed juice”’ in the Hawaiian mills for the years IgII to 1914 was 84°9, with an extraction of 96°4 per cent. of the sugar in the cane. The highest recorded figures for these years were over 90, and came from irrigated Lahaina cane. In Java, for the years 1906 to 1911, with an extraction of go'g, the purity averaged 83°9 in the mixed juice, with many examples THE COMPOSITION OF THE SUGAR CANE 15 under 80. In Mauritius for the year I914 the mixed juice was of 84:6 purity, with an extraction of 90°8. Not dissimilar results are to be found in Peru and in Cuba. At the other extreme are the results obtained in Louisiana, Argentina, Egypt, and Demerara, where, with lower extractions, average purities but little over 80 are found. In the last-named district the writer has experienced purities at the beginning of the crop of less than 70. The Reducing Sugars of the Cane.—The reducing sugars present in the cane consist almost wholly of glucose and fructose. Both of these are present as intermediate bodies used in the formation of cane sugar, and in damaged and overripe cane as degradation products of the cane sugar. At different stages of the plant’s growth the relative quantities vary. Geer- ligs,? and Browne and Blouin? have both shown that fructose is used up more rapidly than glucose, and that it therefore tends to disappear. In exceptional cases it may be entirely absent leaving only glucose, as was observed by Went.® In still rarer instances the glucose in turn is com- pletely assimilated, so that very occasionally canes are found with no reducing sugars ; such a case has been recorded by Wiley.1° As the cane arrives at the mill the percentage of reducing sugars will be found to vary from a minimum of 0°3 to a maximum of 2. The former is found with very ripe irrigated Lahaina cane, while the latter occurs in Louisiana, where the cane never becomes ripe, and in equatorial districts, such as Demerara, where the crop contains material in all stages of growth. The Uba cane grown in Natal is a variety characterized by a very high percentage of reducing sugars. The Fibre of the Cane.—By fibre is understood that portion of the cane insoluble in water. The term corresponds to the “ marc’ of beet sugar- houses. Browne and Blouin? found the fibre of Louisiana cane to be made up of :— PITH. BUNDLES. RInNv. per cent. per cent. per cent. Ash ee = aie o- 1°68 3°58 I*64 Fat and Wax .. aif Se O41 O72 0-98 Cellulose (Cross and Bevan) .. 49:00 50:00 51°00 Pentosans (Furfuroids) eae SS2l04 28°67 26°93 Lignin (by difference) .. 5: 14°93 15°03 E7017 Protein .. a =i : I*94 2°00 2°19 The quantity of fibre in the cane as it reaches the mill is distinctly a varietal characteristic, and is also affected by age and conditions of growth. In Hawaii, for the years 1908 to 1917, the average percentage of fibre was 12'58, herein being included that of the trash accompanying the cane. This average refers to both Lahaina and Yellow Caledonia cane, the per- centages in these being respectively about 11°5 and 13°5._ In Cuba, where the crop is almost entirely Crystalina cane, the crop average seldom reaches II per cent., and at the beginning of the season is generally below Io per cent. In Java, fer the years 1904 to 1912, the average was II-95 per cent., and here as in Hawaii the harvest is divided between two varieties, one P.O.J.100, with a low percentage, and one Bouricius 247, with a high percentage of fibre. In Mauritius, for the year 1914, the average of 34 mills was 12°04 per cent. The cane grown in sub-tropical Louisiana contains a very low 16 CHAPTER II percentage of fibre. The highest figure is reached in the Uba cane, which normally contains from 16 to 17 per cent. of fibre. The Nitrogenous Constituents of the Cane.—Nitrogen is found in the cane as albuminoids, including herein albumen, nuclein, albumoses and peptones, amido acids, amides, nitrogenous bases, and nitrates and ammonia salts. Following on investigations of German origin on the beet, the five last- mentioned constituents have received the rather inappropriate qualification of ‘‘ objectionable,” indicating thereby that they are not removed in the processes of purification, and hence increase the quantity of molasses. Referred to dry matter, Maxwell found the total nitrogen in leaves, tops, and dead cane to be 0:521 per cent. as an average over a large number of varieties, the extreme values being 0:427 per cent. and 0°599 per cent. Taking the stalks alone, he found an average of 0°461 per cent., with extremes of 0207 per cent. and 0°530 per cent. Combination of these results with those quoted above would indicate that about 65 per cent. of the nitrogen is to be found in the waste products, and 35 per cent. only in the stalks. In the cane stalks themselves, Browne and Blouin? found the distribution of the nitrogenous bodies as shown below :— Per cent. of Cane. Albumen (coaguable and soluble in pepsin) . 0*059 Nuclein (coaguable and insoluble in pepsin) .. 0: 040 Albumoses and peptones (not coaguable) 0:033 Amido acids as aspartic acid ae 0°45 Amido acid amides, as asparagine 0° 232 Ammonia as NH3 ss Ba 0:008 Nitric acid as N205 0*°071 Total nitrogenous bodies 0°588 The identity of the nitrogenous bodies remains open to question. Shorey" isolated a body which he identified as glycocoll ; but Zerban!*? with a similar procedure found only asparagine. After removal of the albuminoids, and -by precipitation with phosphotungstic acid, Shorey obtained a mixture of lecithins, the alkaloidal bases of which he identified as betaine and choline. The only xanthine base he found was guanine. In addition to asparagine, Zerban also isolated glutamine and tyrosine, these two bodies being present in much smaller quantity than asparagine. The Ash of the Cane.—As with the other constituents, distinction must be made between the ash of the stalks and that of the leaves, roots, etc. Maxwell’s analyses of Hawaiian cane already referred to gave 3'2 per cent. of ash in the stalks and g'5 per cent. in the leaves, etc., both calculated on dry matter; and Popp!’ in some very early work found 4°05 per cent. ash in. the stalks and 8°25 per cent. in the leaves. The earliest analyses on record are those due to Stenhouse,* and since then very many have been made. Some analyses are vitiated since it is not stated to what basis the analysis refers, stalks, leaves or whole plant. A selection from the very large number on record is given below and covering the extreme variations in composition. This variation will be controlled by variety, the composition of the soil, and by the manures used. The only features of constancy are the preponderance of silica in the ash of the leaves and of potash in the stalks. PLATECHE ROSE BAMBOO. THE COMPOSITION OF THE SUGAR CANE 17 COMPOSITION OF SUGAR CANE ASH. | | / ts [2 3 4 5 6 7 8 ree he Ar 43} \) 43 267 1h hte Pee ae Gee ee Te faked | aes me 7 ere Lee ' Silica ee [560° -o9|18- "09)53°38/28°69)78'5 52°8 56°76/53°54/65°78|43°75|30°32,15°70.49°52 Titanic Acid.. I-14 .. | 0°69) * AG eee Sty epic ue Me Phosphoric Acid | x'59 g°I2} 1°28) 7°46 ro 4-7 10°63/10°78| I 25) 5°45| 7°25) 5°27) 3°99 Sulphuric Acid | 5°34 5°64) 5°50) 4°15\2°4 | 274) 2°60) 0°53) 2°18/16°53/11-29 18-47) g°15 Chlorine 2°59) 5°45} 4°03) 8°67\0°3 | 073) 0°20) 0°92) 1°65} O-21| 3°08) 4°55] 0-98 Ferric Oxide.. 6-47) 7°43) 4°04! 3°25|0°7 | O75] .. 0 ' 0°85] 0°56) 1°45 1°13) 3°60 Alumina : SOE EZ SEE - OTH SG5tl ye -[) 2 |) sere BW GS ++ | 1°03, 0°25) 4°70 Manganese Oxide 0°27 a OO rah oe fal, Sap eieotsl ee 55 Pes boast acu Lime 5°62) 3°85) 6°02) 4°08)4°7 | 2-7 6°50) 3°24) 8-19/12°53) 5°90) 5-19) 3°45 Magnesia 45 6°06) 4°42) 5°91|2°3 | 2°I) 5°08) 3°22) 2-45] 6°61) 5°11] 5°76) 2°61 Potash 43°44\28- 99, 17°11)/32°26|8°5 |23°0\22°56 25°63\/10° 69] 7°66)31°25/38-23/17°390 Soda 1°66) 3°40, 1°37) 2°70|1-7 | 1°75) 5°67) 2°56) 3°26) 6°45) 1-17) 1°30) 0°85 Carbon : ie tae ae SS Cee | Fi ad (eye se | 716 0°54, 2°30 i. Lahaina cane, leaves, tops and dead cane. 2. Lahaina cane, stalks. 3. Yellow Caiedonia cane, leaves, topsanddeadcane. 4. Yellow Caledonia cane, stalks. Analyses due to Maxwell! in Hawaii. 5. Cheribon cane, leaves. 6. Cheribon cane, stalks. Analyses due to Van Lookeren Campagne?® in Java. 7and 8. Stalks of Mauritius canes. Analyses due to Bonadme.*® 9. Leaves of Egyptian canes. 10. Stalks of Egyptian canes. Analyses due to Popp.** 11. Leavesof D74cane. 12. Stalks of D 74 cane. 13. Roots of D74 cane. Analyses due to Hall? in Louisiana. Organic Acids of the Cane.—In earlier researches a great number of organic acids have been stated to be present in the cane, many of which have not been found by later workers. The most detailed investigation is due to Yoder,1” who, in Louisiana, found per I00 c.c. of cane juice 0°05 gram aconitic acid, 0:00077 gram malic acid, and 0-00004 gram oxalic acid. He did not find tartaric, citric or succinic acids. On the other hand, citric acid was positively identified and isolated in quantity by Shorey!’ from the deposit on the tubes of an evaporator working up juice from canes in Hawaii which had been damaged by a long drought. Acetic acid is a constituent of damaged cane. The original recognition of aconitic as the dominant acid is due to Behr,}® in 1877. Gums.—These bodies, also referred to as pectin and alcoholic precipitate, are of uncertain composition. They occur in the cane up to o-2 per cent., and are present in largest proportion in unripe cane. They are insoluble in acidified alcohol, and are absorbed by animal and vegetable carbons. They are derived from the hemicelluloses of the fibre’ and consist chiefly of xylan, araban and galactan. Part are precipitated in manufacture and part find their way to the molasses. Wax.—This mixture of bodies, first observed by Avequin,?® occurs on the exterior of the cane. It may amount to 0°05 per cent. of the cane, and in some varieties is almost absent. It has been exhaustively studied by Wijnberg™*, who finds that 70 per cent. of the crude body consists of glycerides of oleic, linolic, palmitic, and stearic acids, together with hydroxy- acids, resin acids, lecithins, phylosterol, aromatic and colouring matters. The remaining 30 per cent. contains about 45 per cent. of myricyl alcohol and 35 per cent. of a non-primary crystalline alcohol. These data refer to the benzene soluble bodies. Cane wax has now become an article of commerce. Cc 18 CHAPTER II Other Constituents.—Other constituents present in very small quantities but of technical importance are colouring matters, of which chlorophyll, anthocyan, the blue or red pigment in coloured canes, and saccharetin are the chief. Amongst these should also be included the tannins or polyphenols, mainly resident in the tops and eyes ; these were first observed by Szyman- ski,22 and have since been studied by Narain?? and Zerban*4. The latter finds that the cane tannin or polyphenol is a derivative of pyrocatechin allied to the oak tannins, and to be placed in Class 1a of Proctor’s classi- fication.?® k Various enzymes are also known to exist in the cane. Browne? found an invertase mainly resident in the tops, and Raciborski?® identified a laccase and peroxidase, to which Zerban?? has added a tyrosinase. REFERENCES IN CHAPTER II i. 3.5.P:A. Ex, Sta.; Agric., Ser. Bullo: 2. thaskxs Stas Bulleor 3. Ann. Chim. Phys., 1844, I1, 39. 4. Memoires de l’Academie des Sciences, 1850, 22, 509 5. Quoted from Experiment Station and Government publications 6. Java Arch., 1896, 4, 525. 7. In “ Cultur de la Canne a Sucre ”’ 8. Stubbs’ “‘ Sugar Cane.” QO: FS.1G581807,1208/207. ro. S. C., 1889, 21, 484 11. Jour. Am, Chem. Soc., 1897, 19, 881; 1898, 20, 113; 1899, 21, 809. 12. International Congress of Applied Chemistry, 1912 13. Z. ftir Chem., 1870, 6, 329. 14. Phil. Mag., 1845, 27, 533- 15. fava Arch., 1804, 2, 113. TOW S.C. 1804, 201622. 17.. Jour. Ind. Eng. Chem., 1912, 3, 643. LOO LOO4,. 20.9072 19. Proc. Am. Chem. Soc., 1876, 1, 220. 20. Ann. Chim. Phys., 1840, 75, 214. 21. Jour. Soc. Chem. Ind., 1912, 28, got. 22. Berichte des Vereins Station fiir Zuckerrohr in West Java 2 13 23. Agric. Jour. of India, 1918. Science Congress issue. 24. jour. Ind. Eng. Chem., totg, II, 1034. 25. jour. Soc. Chem. Ind., 1894, 13, 487. 26, Java Arch., 1906, 14, 857. | 27. La. Plant., 1919, 61, 299: CITLACPAT ER ETE RANGE AND CLIMATE THE influence of climate on cane culture was probably first discussed by the Marquis de Cazaud in his “‘ Précis sur la Canne,’’ published in 1776. This work deals with Grenada, and, besides discussing climate and giving statistics of rainfall, is valuable as presenting a very detailed account of the agricultural operations as then carried out. A second publication is that of Sir W. R. Rawson! sometime Governor of Barbados, who collated the rainfalls of that island for the years 1842-71, and showed the dependence of the cane crop thereon. The latest study on this matter is that of Walter,? who has collected the very detailed records of the Royal Alfred Observatory in Mauritius, and shown the connection between temperature, rainfall and its distribution with the return per acre. Some of his work, which should be studied in the original, is referred to below. The Geographical Range of the Sugar Cane.—The cane is essentially a plant that requires a high temperature and large quantities of water. The limits of its cultivation are perhaps best defined as lying between the isotherms of 68° F., which, independently of the tropics, are taken as defining the torrid zone. North of the equator and at o° longitude this line starts at 36° N., and follows the North African coast, gradually falling to 28° N. as it leaves the continent and reaching this latitude at 80° E. It then runs parallel to the equator to 120° W., when it again rises to 36° N. as it meets the North American coast, and remains on this parallel until it meets the longitude of Greenwich. The southern isotherm of 68° F. at 0° longitude lies at 18° S., whence it rises to meet the extreme west point of Africa at 14° S., and then abruptly falls as it crosses the continent, roughly paralleling the coast line until it reaches 25° S. It then crosses Africa in a line parallel to the equator, and, rising very slightly over the Indian Ocean, meets the Australian continent at 25° S., and, again running parallel to the equator, meets the Pacific Ocean at 100° W. It then rises sharply to strike the South American coast at 16° S., and then, receding from the equator, roughly follows the coast line to 28° S. in the centre of the continent, and rises again to meet longitude Oo: at 16° S. All the cane-producing areas lie within these limits except those of Spain, Southern Japan, and Northern New South Wales, which are located just on their fringes. The localities where the cane forms a staple commercial product are :— In Asia—British India (10°-30° N.), Java (6°-8° S.), the Philippines (5°-18° N.), Formosa (21°-25° N.), Southern China (22°-30° N.), and the more southerly islands of the Japanese Archipelago (30°—32° N.). Se, 20 CHAPTER IIT In Africa—Madeira (33° N.), Egypt (4°-30° N.), Natal and Zululand (28°-30° S.), Portuguese East Africa (10°-28° S.), and Mauritius and Réunion (19°-21° S.). In America—Louisiana, with isolated instances in Arizona, Texas and Georgia (30°-32° N.), the whole of the West Indian Islands (8°-22° N.), including therein Cuba, Porto Rico, Santo Domingo and Hayti, Jamaica, Martinique and Guadeloupe, St. Vincent, St. Kitts, St. Lucia, St. Thomas, Virgin Islands, Barbados, Antigua and Trinidad; British and Dutch Guiana (6°-8° N.), Mexico and the Central American republics (8°-25° N.), Brazil (0°-23° S.), Argentina (22°-28° S.), Paraguay (20°-22° S.), Venezuela . (0°-8° N.), and Peru (3°-18° S.). In Australasia—New South Wales and Queensland (16°-30° S.), Fiji (15°-21° S.), and the Hawaiian Islands (18°-21° N.). In Europe—Spain, in the extreme south-east (36°-37° N.). Apart from these commercial centres the cane may be found growing as a garden plant in the Bahamas, Bermuda, Cape Colony, Mesopotamia, Persia and Arabia. In the middle ages Sicily, Malta, Cyprus and the Levant were the centres of a considerable industry, and the seventeenth century saw an attempt to grow the cane in the south of France. It still survives in these localities. As a matter of curiosity it may be recorded that at the Great Exhibition of 1851, Dr. Evans showed sugar made from.canes grown in Surrey, England, by Mr. BH. Perkins. The Temperature of Cane-growing Districts—As the cane is grown in countries widely differentiated, both as regards latitude and altitude, there is a wide variation in the conditions under which it is produced. The hottest localities are not those which lie at or near to the equator; such have a temperature distinctly lower than many a number of degrees remote. therefrom. Actually the heat equator at 0° longitude lies close to 20° N. latitude. Passing east it leaves Africa at its most easterly point, 13° N., and then runs parallel to the equator, crossing southern India, whence it turns south and crosses the equator at 80° E. It remains south of the line to 120° W., when it rises abruptly to meet the American continent at 25° N. Crossing the continent it runs S.E. closely following the east coast of Central and South America, and leaves the most westerly point of the continent at 2° S. It then runs in a north-easterly direction till it again meets the parallel of Greenwich at 20° N. The mean annual temperature in degrees Fahrenheit and that of the hot- test and coldest months for each five degrees of latitude are thus given by Spitaler.* NortH LatitupDE. SoutH LATITUDE. BO? (e255 po ZO et Tao aanS O° 5° 10°” 15°. )20°ke 2a aeesas January = 58-3 65*1 71°1 74°9 78°3 79°2 79°2 79°0 78-6 78°3 77°4 76°5 73°0 July .. 81-1 82*4 82°6 82:2 79°5 79:0 77:9 76°8 75°2 72°7 68:9 64°6 58°3 Year .. 68°5 74°7 78°3 79°3 79°5 79° 78-6 77°9 77°° 75°6 72°9 69°6 65°3 These figures refer to the parallel as a whole, and generally continental areas exhibit greater extremes than do the maritime regions. The hottest localities occur in Africa, India, Central America and Northern Australia, where mean annual temperatures of 85° F. are recorded. *These temperatures refer to sea level. The U.S. Dept. of Agric., Weather Bureau, assumes a fall of 1° Ffor each 325 feet rise in altitude. RANGE AND CLIMATE 21 Rainfall—tThe two great climatic divisions as regards rainfall are the marine and the continental. The marine, which also extends inland, is characterized by heavy periodic rainfalls and by a high degree of cloudiness. The continental, on the other hand, possesses the feature of long periods of drought, with infrequent rainfall. Here belong the great desert areas of Africa, Asia and northern Australia. As belonging to this type should be placed the sugar-producing areas of Egypt, Peru, the lee side of the Hawaiian Islands and the small area in south-eastern Spain. In all these the industry is dependent on irrigation. In the marine climate lies the belt of equatorial rains, within which are included the land areas of the north of South America. The maximum fall here follows the sun as it moves across the zenith, and hence there are two wet seasons and two dry seasons. This distribution of rainfall is exemplified by the figures of the average precipitation at Georgetown (Demerara) for a period of 32 years. The dry season extends from mid-August to mid-November, and again from February to April, the maximum rainfall occurring during the hottest months of the year. AVERAGE RAINFALL AT GEORGETOWN, DEMERARA. Month. Inches. Month. Inches. Month. Inches. aril .5-. 6+90 May .. 10°94 Sept << 2+80 Hebi. 4206 jane” .2 22-88 Octiahi..5 2236 a 5°41 jaly..:: 9:02 Novis 505° 65 Apr... 6:40 AMES 44 6°98 Dec. .. 10°86 Monsoon Tract.—A very important climatic zone is that of the monsoons embracing the sugar-growing areas of Java, India and northern Australia. During the period May to October in regions south of the equator the south-east monsoon prevails, and this period forms the dry season. From November to April the north-west monsoon blows, and in these months the rainfall is heavy. North of the equator the seasons are reversed, and more remote from the equator in British India the monsoons give rise to three distinct seasons, a cool dry winter followed by a hot dry spell, which in turn gives way to a hot wet season lasting until the cool dry winter period arrives. Java.—tin Java, which lies within this climatic zone, there is a great difference in the precipitation experienced in the different sugar areas, as indicated in the following table (the mean of many years®), which also demonstrates the seasonal regularity of the fall. RAINFALL IN THE SUGAR AREAS OF JAVA—INCHES. Station. Jan. | Feb. |Mar. | Apr. |May|June July Aug.|/Sept, Oct. Nov. | Dec. | Year Cheribon .. 17°13/14*°65,14"69 7°95|5° 28/4° 33 2° 72\0° 87|1- 18) 2:44 6-06|14*80) 92*10 Semarang ../14-6114°13| 8-90) 7°36|5-04 3°35 3° 11|2- 563-70) 5°39) 7°28)10-47, 85-90 Soerabaya ..|12-09/10-98)10- 390] 6: 58]4° 45 3° 50.2°01 0: 83/0°55, 1°57) 4°57) 9°65| 67°17 Pasoeroan ..| 9*06/10°39 7-95] 5*12|3*03/2-44 1-10 0-24/0-16, 0-51) 2-24) 6-61) 48°85 Probolinggo | 9°25) 9°69) 6-10] 3-98|2-52,1-77 0° 790° 39|0°16| 0-47) 2°44) 6°46) 44°02 Beznoeki_ ..|12*Soj11-81, 7-00] 3°30|2°17,1-54 0°980-24\0°12| 0-28) 2°24) 7-60) 50-26 Banjoemas [13+ 35|/11* 5013+ 35]10- 04|7- 68 5+55 4°06 2° 99|3° 66)12- 17/17° 13|17° 95/119° 43 Djokdjakarta |13-78,12-48|/12-91| 8-15|5- 393-90 I-89 1- 22/1: 50) 3°74) 9°57\13°90| 88-43 Soerakarta .. 12-87|12-95 11-81} 8-03]4-88)3-86)2-24/1-85|/1- 81) 4°06) 8-78)10-51| 83°65 Madioen . -/I2*44/T0- QI|T0- 12 8- 82/5: 08/2: 99 1° 61|/1- 06|1-22| 2°64) 7°87) 9°91) 74°37 Djember . 14°65 15*24|14-37| 8-98|6-22'4° 37/2: 952° 17|3°07) 6+ 30\11* 26 14° 17|103°75 Sitobondo ..|/10-67| 8-66) 6-30) 2-36|1-97/I-14.c-630-16|o-16) 0-75) 2°05, 5°79) 40°63 22 CHAPTER. LY West Indies.—A second great sugar-producing region, the West Indies, also has its climate divided into a wet and a dry season, the former as in the East Indies coinciding with the hot weather. Thus in Cuba the rains usually begin in May and continue to November, the period December to April being one of comparatively little fall. This whole area is not one of relatively heavy rain, as is shown by the statistics quoted below.® RAINFALL IN CUBA FOR THE YEARS 1907—-I11.—INCHES. Province. 1907 1a08 I9C9 I91o IQII Pinar del Rio .. 39°75 75°39 84°96 82°55 78:61 Havana .. ae 25°05 49°10 52°44 46:60 41°76 Matanzas .. ic 43°85 53°12 SOG 45°60 58-36 Santa Clara 35 41°37 Sc 57°48 50°37 55°91 Camaguey aE — 44°62 62:28 41°50 36°02 Onientew eer Me 34°31 57°34 55°91 21°75 36-88 In Barbados’ the rainfall for the years 1898-1907 was as shown in the table below. RAINFALL IN BARBADOS—INCHES. Year. Fall. Year. Fall. 1897 ac 72 1903 ee 66 1898 ae 68 1904 se 58 1899 be 50 1905 at 54 I900 3% 60 1906 we 70 IQOE Fc go 1907 3c 47 1902 e% 55 1908 are 44 In other of the West Indian Islands, notably Antigua and St. Croix, the precipitation is normally much less and often does not exceed 30 inches in the whole year. Trinidad, on the other hand, belongs to the equatorial rainbelt type. Hawai and Mauritius —tThe climates of the Hawaiian Islands and of Mauritius and Réunion, lying equal distances respectively north and south of the equator, present certain points of interest and similarity. The windward side of Hawaii lies in a zone of nearly constant rainfall, the average at Hilo (40 feet) being 139 inches per annum,’ with a remarkably even distribution ; even more than this is registered at plantations in the same rain belt that lie at higher elevations. Thus the average fall at Onomea at 250 feet elevation is 189 inches, and for that very wet year, 1918, it reached 308 inches. At Olaa mill, 225 feet, the average fall is 153 inches, rising on the same plantation to 207 inches at 1530 feet elevation. At Hakalau, at the 1,200 foot elevation, it is 276 inches. These two last places, which lie on the extreme upper limits of cane cultivation, are probably the wettest where the cane is grown. On the lee side of Hawaii and on the littoral of the other islands, Maui, Kauai and Oahu, the climate passes to the continental desert type, with an average fall of about 20 inches per annum at sea level. In the mountainous interiors of all the islands the fall is very heavy. This distribution is the effect of the moisture-charged north-east trade winds meeting the cold surfaces of the mountains. Similarly, the north and east of Mauritius belong to the continental desert type, the interior and south-west being in a zone of heavy precipitation. Averaged all over Mauritius® for the 4o years, 1863-1902, the fall was 79 inches, with extremes as in Hawaii all the way from 20 inches to 150 inches or more. In contradistinction to the general tropical rule in these islands, it is the cold season that coincides with the period of maximum precipitation. RANGE AND CLIMATE | 23 Philippines.—In the Philippine Islands!° the average over the whole archipelago is 74 inches per year. The west side presents the usual tropical phenomenon of a wet season, May to October, and a dry season, November to April. In the eastern half of the islands the rainfall is fairly evenly distributed, the least rain falling in the period February to April. In Formosa the distribution is very irregular ; at Keeling, in the extreme north of the island, the fall amounts to 200 inches, but in other parts cane can only be grown under irrigation. In Tucuman, in Argentina, the fall -for the years 1855-96 averaged only 36°8 inches. In Australia, in the northern limit of cane cultivation, the fall is about 80 inches, decreasing to 40 inches at Bundaberg, near thesouthern limit. Fijiis a locality with a very heavy fall on the windward side, that at Suva averaging 130 inches; the climate there resembles that of the wet Hilo zone of the Hawaiian Islands. Of districts outside the tropics, Madeira has an average fall of but 28 inches , Louisiana resembles the tropic type ; at New Orleans" for the years 1887-96 the fall averaged 59°8 inches, the extremes being 46:0 and 75:3 inches. Over the sugar belt the fall is rather greater, the maximum precipitation occuring in the summer months. Failure of Rains.—Although, when averaged over a number of years, the fall in the tropics is very even, both as regards periodicity and quantity, the seasonal rains sometimes fail, leading to prolonged periods of drought. It is in India that the failure of the wet monsoon has become most notorious, as there it causes the occurrence of periodic famines. In the belt of equatorial rains similar seasonal irregularities are also known; thus at Paramaribo (Dutch Guiana) the fall in 1899 was only 48°8 inches, the average for the period 1897-1908 being 92°3 inches ; the next lowest fall was 76-4 inches, in 1906. The whole island of Cuba is liable to prolonged droughts, such having happened in 1900 and 1908, and from the immensity of its production a very disturbing influence on the sugar market follows; in fact, almost every sugar-producing district is liable to suffer in this way. The island of Java seems to be most favoured in this respect if the relatively small areas of Hawaii near Hilo, and the windward side of the Fiji Islands be excepted. As a paradox it may be remarked that those localities that suffer least are the very arid regions which have developed systems of irrigation, as in Peru and the leeward sides of the Hawaiian Islands. On the other hand a great excess of rainfall may fall in a short time. Falls of ro inches in a day do - not excite comment in many parts of the tropics, and falls of as much as 20 inches in the same time are not uncommon ; what is one of the greatest falls on record occurred at Suva in Fiji, on August 8th, 1906, when 41 inches fell in 13 hours. Prolonged spells of wet weather are also common, but the damage they occasion is but small compared with what is due to a prolonged drought. Rainfall and Altitude.—Besides latitude, altitude has a great effect on rainfall, which invariably increases with elevation. The effect of altitude is shown in the following statistics dealing with the widely separated localities of Barbados, Java, and Oahu in the Hawaiian Islands. BARBADOS—AVERAGE OF YEARS 1841-72. Altitude, feet .. .. 6200 200-400 400-600 600-800 800-1,000 Over 1,000 Rainfall, inches me eas FEES, 46:0 52°0 58°5 58°6 70°3 Number of Stations .. 22 22 9 14 4 2 24 CHAPTER. Tf HONOLULU, FOLLOWING THE NUUANU VALLEY. Altitude, feet .. he on 20 400 860 Rainfall, inches Sa .. 24-36 90 143 RAINFALL AND ALTITUDE IN JAVA. Meester Posen Bodjong Buitzen Locality Batavia Cornelis Mongo Depak Geelis borg Distance from coast, miles 4 7 ett 21 2G 36 Altitude, feet 52 oe 23 46 I16 304 429 874 Rainfall, inches... eee y pi GE 96 120 146 174 Percentage of Moisture-——Connected with the rainfall is the humidity, and it naturally follows that places with heavy rainfall also have a humid atmosphere. Proximity to the sea is another important factor. At Honolulu, in a dry locality and near the sea, the average relative humidity for the year I9g0I was 700, with extremes of 67:2 and 76°6. At Batavia, both wet and near the sea, the average for the years 1866-1900 was 82:8, with monthly extremes of 77-5 and 87-5. The percentage of sunshine is another climatic factor of influence. It is least in the marine type of climate, and over the belt of equatorial rains only amounts to 45 per cent. of the possible, rising to 80 per cent. in localities, such as Egypt, that belong to the continental type. Wind.—A climatic factor of a different type is that of wind. Generally the trade winds typical of the tropics blow with a steady velocity of about to to 20 miles per hour. When the wind reaches a steady velocity of 30 miles per hour a cyclone is officially recorded in Mauritius, and this island and the near-by one of Réunion are those which are most subject to these disturbances, the centres of forty-three cyclones having passed within one hundred miles of Mauritius during the years 1857-1908. Some cyclone damage obtains in Mauritius about one year in three, the cyclone of May 2gth, 1892, being one of the most destructive ever recorded. All of the West Indies, with the exception of Trinidad, lie in the hurricane belt of the Caribbean Sea, while Formosa is exposed to the typhoons of the China seas. The Philippines just come within this region, and the crops there are occas- sionally damaged. The Effect of Climate on the Cane.—The influence of temperature on the physiology of the cane is very complex. The rate of growth, the time to maturity, and the composition are all affected. In the more equatorial areas the temperature variation is so small that differences in the rate of growth are hard to detect. In the districts more remote from the equator the influence of the cold season is pronounced. Measurements made in Hawaii by Eckart!? on a large number of varieties indicated that during the cold season the length of internodes was generally more than 30 per cent. and less than 50 per cent. of those formed in the hot season ; the diameter of the stem was also less. The period taken for the cane to ripen is also depend- ent on temperature. In Demerara, Bourbon canes planted in December will arrow in the following September; in places lying near the tropic thirteen months is a common time. Walter!® has observed that in Mauritius canes planted near to sea level reach maturity in thirteen months, whereas those planted at the I100-foot level require twenty-one. From a zero of 70° F. he has calculated that in these periods the canes receive the same quantity of heat; that is to say, the product, “ days x excess daily mean over 70° F.,”’ is the same, and in this case has a numerical value of 1350. RANGE AND CLIMATE 25 The temperature range has a very important bearing on the composition of the cane. In those places that have a uniformly high temperature and no cool season, an impure cane of lowsugar content and high in reducing sugars is almost invariably harvested. In such a case there is opportunity for continuous vegetative growth, and the crop as it reaches the mill will consist of canes in full vegetative vigour, of ripe, and of over-ripe canes. The non-sugars present will consist of products in process of metabolic change, and of degradation products formed from the breaking down of the cane sugar. In extra-tropical climates, such as in Louisiana, the limited period of growth affords a cane that does not have an opportunity to reach maturity. A juice low in solids, sugar and purity, and high in reduc- ing sugars, results, the latter bodies representing material in course of trans- formation to cane sugar. A sweet and pure cane is found in those regions where a longer period is taken to maturity, combined with a season sufficiently cold to check the vegetative vigour of the plant, whereby its energy is directed towards the elaboration into cane sugar of material already in the process of transformation. Those localities lying on the confines of the tropics present these conditions, and when, as in the arid districts of the Hawaiian Islands and of Peru, water can be withheld from the plant and that in the plant can be transpired, the sweetest and purest material results. The writer is aware of only one attempt to correlate temperature and composition, and this was made by Michaud! in Costa Rica. With due regard to the elimination of experimental and of personal error, he caused ripe canes of the Red Ribbon variety to be collected at various altitudes, the temperatures of which were known or could be interpolated. The latitude of Costa Rica is 8°-11° N., its coast line lying on the heat equator, and though the influence of rainfall is not included, the results tabulated below, with one exception obviously abnormal, agree with the remarks made immediately above, regarding the effect of temperature as controlled by latitude. EFFECT OF TEMPERATURE ON THE COMPOSITION OF THE CANE (MICHAUD). Temper- Sugar Water Sugar Solids Altitude ature per cent. per cent, per cent. per cent. Purity feet Be cane cane juice juice 5,937 62°5 15*60 72°43 18:76 22°0 84°99 5,379 64°5 15°59 73°24 18-71 20-80 89°98 4,547 66:0 16+ 38 71-96 19°84 22°21 89:36 4,195 68-0 16°45 71°34 20°IT 21°21 94° 83 3,641 70:0 16:63 71*20 20° 32 22°10 91°95 2,844 72°5 17:00 71°34 20° 42 24°60 82-99 2,301 74°5 17°38 73°94 20°50 21-98 93°29 1,148 78°0 16:80 74°00 19°88 20:98 04°77 718 79°0 16°06 74°60 18+92 20° 86 90: 68 33 80°5 14°45 75°38 17°08 18-60 91°85 The effect of rainfall on the crop is more than a matter of the total fall, its distribution being of equal importance. It is at once patent that a fall of ro inches in 24 hours is less beneficial than five precipitations of 2 inches separated by weekly intervals. Walter!® in discussing this subject intro- duces the terms “ inefficient rainfall ’’ and “ degree of wetness.’ The latter he defines as R#/¢ where R is the rainfall, ¢ is the days in a month and # is the number of rainy days in that month. The Mauritius statistics as collated by him for the period 1892-1905 are given below, as they serve to demonstrate the combined effect of rain and temperature on the crop harvested. 26 CHAPTER III INFLUENCE OF CLIMATE ON MAURITIUS CANE CROP (WALTER). Metric tons Rainfall, Degree | Number Temper- of cane per Year. Oct.-May. of of rainy ature arpent inches. wetness. days. F° (1°043 acre). 1892 43°97 27°45. | 133 76:8 14°85 1893 45°21 32°13 | 163 75°5 25°28 1894 | 38-76 22°31 137 74°7 16°27 1895 44°00 31°53 | 132 76-0 22°15 1896 69:78 41°26 126 75°6 21627 1897 E5*AGHS i'l 7°62 | 94 75°9 6-63 1898 37°67 24° 33 | 146 76°5 25°93 1899 35°43 22° 53 I19g 76-2 20°99 1900 27°54 16°40 127 79°7 22—2n I9OI 40°05 20* 49 122 76-0 16-38 1902 4118 262870) a “6537 75°4 17°99 1903 43°89 29°2 | i394 76°6 26-19 1904 34°26 | 23°01 148 74°8 14°34 1905 | 51°60 42°63 | 150 tad | 23°99 The question is, however, more complicated than this, and is controlled by other factors, which are also discussed by Walter. The effect of rain or drought in one year may continue into the next, and there is also a ten- dency for small crops to follow heavy ones. . This is not so much a question of temporary soil exhaustion as that a large crop means a long period for harvest, with a reduction in the time available for the next growing season, when the crop consists mainly of ratoons. Other observations on record are those of Rawson! in Barbados, who, from a study of rainfall statistics, showed that it was possible to foretell the return of sugar per acre within an error of 6°6 per cent., when the rainfall for the preceding twelve months was known. Similarly, Maxwell Hall in Jamaica observed relative productions per acre of 14°41 and 15°59 as corresponding to rainfalls of 56 and 76 inches respectively. It would not be unreasonable to suppose that those areas lying in a zone of nearly constant rainfall would afford a cane of low sugar content. Such, however, is not the case. The average precipitation on seven plantations in the Hilo rain zone is 173 inches ; that on six plantations adjacent to, but outside the zone, is 84 inches. Averaged over ten years the sugar content of the cane grown on plantations in this rain zone was 13°05 per cent., that of the plantations in the comparatively dry area being 13°22 per cent. The soil conditions and varieties of cane grown were nearly identical, and at the same time the drainage was very rapid. On the other hand, the effect of heavy rains during the crop season is seen in a diluted juice for several days after the fall. If there is no decrease in the purity, no loss of sugar but only a dilution is indicated ; anew growth starting will cause the consumption of sugar in metabolic processes. Connected with the question of heavy rainfall is the possibility of larger quantities of combined nitrogen being afforded to the crop. The most detailed statistics on this matter are those of Lawes and Gilbert made at Rothamsted in England, where they found on an average 4°92 lbs. of com- bined nitrogen in the yearly precipitation. Elsewhere most varied results have been found. The greatest quantity of nitrogen as ammonia recorded in a year has been found in Venezuela!® and in Tonkin!’, where 14°05 and 13:60 lbs. nitrogen respectively have been observed. The greatest quantity of nitric nitrogen recorded was also in Tonkin and equalled 14°70 lbs. nitrogen RANGE AND CLIMATE 27 per acre; the next highest figure is from Réunion!* and only amounts to 6-24lbs. per acre. In great contrast to these figures are the minima recorded from East Java!® and amounting to only 1°13 lbs. of ammoniacal and 0°75 Ib. of nitric nitrogen. In one and the same place also there are large yearly variations. Thus, in Tonkin during the years 1902-08 the ammoniacal nitrogen varied from 3°25 to 14°70 lbs., and the nitric nitrogen from 3°95 to 13°60 Ibs. It follows, then, that no definite figure can be given, as the quantity received may vary from 2 to nearly 30 lbs., the probable amount being in the neighbourhood of 10 lbs. Whereas the ammoniacal nitrogen is derived from the degradation of organic matter, notably that contained in the sea, that which occurs as nitric may be largely the result of atmospheric electrical discharges ; this connection, after having once been accepted and then discounted, has received support by Capus?? following on a study of results obtained by Aubray?§ in Tonkin. The main effect of drought on the cane crop is, of course, reduction in tonnage; what crop is harvested will contain a high percentage of fibre due to the restricted length of the internodes, and to the evaporation of water from the cane by increased transpiration. The humidity of the atmosphere is another factor that bears on crop production, and as it grows less the greater becomes the quantity of water that is transpired from the leaves, and the greater becomes the demand on the soil supply. Early writers observing that the bulk of the cane culti- vation was near the coast attributed a specific effect on the cane to the saline breezes and maritime climate. Thus Wray!® writes :— “The climate most congenial to the cane is of a warm and moist character, with moderate intervals of hot, dry weather, attempered by the refreshing sea breezes. It has been found to grow most luxuriantly on islands and along the sea coasts of the mainland, which leads us to conclude that the saline particles borne on the sea breeze exercise a powerful effect on the growth of the cane.”’ Delteil!4 expresses himself in terms similar to those used by Wray :— “The sugar cane originating from India and Eastern Asia demands a warm. moderately moist climate, with intervals of dry heat ; it loves sea breezes because of the particles of salt which are carried to the fields and increase their fertility.” According to Boname :—! ‘‘ A warm and moist climate is most favourable to the growth of the cane, and it is on islands and the sea coast that the most luxuriant plantations are to be seen, for it is here that are found together the conditions of heat and moisture demanded for its greatest development.”’ Stubbs, in commenting on this idea, is most certainly right in attributing the maritime position of many sugar plantations to economic reasons. An inland sugar estate in most tropical countries would be deprived of means of access to the world’s markets. Where a local market exists, the cane is grown successfully in districts remote from the sea, as in Queensland, Argen- tina, Brazil and India. Some insular districts, such as the arid parts of the Hawaiian Islands, have a climate of low humidity, and the same is also the case in the dry parts of Peru, both of these places producing, under irrigation, the largest crops on record. A factor that has influence on the composition of the cane is that of direct sunshine as bearing on the process of change known as photosynthesis. The experiments of Went in Java are referred to in Chapter I, and the factor may reasonably be of some moment in the wetter districts, and may account 28 CHAPTER: Tit in part for the low percentage of sugar in canes grown in the equatorial rainbelt. The remaining climatic factor to be considered is that of the winds, the chief effect of which is concerned with the removal of soil water. The more frequently the stratum of air over the soil is removed the greater is the evaporation. The point of the compass from which the wind blows is also of consequence. When the wind blows from the sea to the land air heavily laden with moisture is conveyed thereto, whereby the soil evaporation is lessened. It is probably for this reason that the surface evaporation from shallow exposed vessels is smaller in Demerara than would be expected from temperature conditions alone. Here it reaches 35:21 inches per annum, compared with 31:04 at Oxford and 88-28 at Bombay.” In Demerara the prevailing winds are the north-east trades blowing from the Atlantic Ocean, with no mountains to intervene and cause a deposit of the air-borne water as rain. Maxwell?? in Hawaii found that 120 sq. ins. of exposed area evaporated in 270 days 33,480 grams of water, the relative humidity being 79°5, and the average temperature 79°5° F. Under equal conditions, but with the water protected from the wind, the evaporation was equal to I2‘r inches perannum. Toa certain extent the evil effects of winds may be mitigated by the judicious planting of windbreaks. Crop and Planting Time.—The combined influence of rainfall and tem- perature determines the harvest and planting seasons. The harvest takes place in the dry season, and mainly after the cane has reached maturity. In those localities that have a cool season, the harvest time is coincident therewith, and its duration is limited by the commencement of the rains, which not only mark the beginning of the period of vegetative activity, but also render haulage operations impossible. Conversely, the rainy season is selected for planting, and the amount of rain falling in a period also determines the possibility or not of ploughing operations. The harvest time of the principal cane-growing districts is as follows :— Cuba and the West Indies—December or January to June. Java—May to November. Mauritius and Réunion—August to December. Louisiana—October to January. Hawaiian Islands—December to September. Peru—October to February. Brazil—October to February. Argentina—June to October. Egypt—December to March. Queensland—June to November. Mexico—December to May. Philippines—December to March. British India—January to April. Spain—March to May. Formosa—January to May. Fiji—June to November. Madeira—February to May. Natal and Portuguese East Africa—May to November. British Guiana has two and sometimes three crop seasons; the main harvest is from September to December,.with a short season in May and June and an occasional one in March. RANGE AND CLIMATE 29 The harvest season generally extends over a period of four to six months and exceptionally in the arid localities may be continued over the whole year with such stops only as are required for overhaul and repairs. At the beginning of the crop an unripe cane of lower sugar content is harvested ; the percentage of sugar gradually increases and is usually at a maximum in the third and fourth months of harvest, after which it decreases as the cane becomes over-ripe. Taking Cuba as an example, in December the cane will contain from Io per cent. to 11 per cent. of sugar, the maximum of 14-15 per cent. being obtained in March and April, after which a fall occurs, which is very rapid if the crop is prolonged after the seasonal mid-year rains fall. It is easy to see that the combined questions of factory capacity, capital cost, duration of harvest, and yield per cent. on cane form a most important economic problem, which is usually further complicated by a deficiency in the labour supply. The ideal distribution of rainfall and temperature for an annual cane crop in the northern hemisphere would be somewhat as follows. During the crop period, for example from December to April, a cold dry season should prevail with showers of sufficient frequency to maintain the vitality of the cane without interfering with the harvest operations. During the next six months, or from May to October, there should be a high temperature combined with a heavy and well distributed precipitation. The rains should fall at the rate of about two to three inches per week with absence of excessive falls or of prolonged periods of drought. For one month prior to harvest the rainfall and temperature should both decrease in order to stop: the vegetative growth and allow the cane to ripen, but complete absence of water is not desirable. Finally, it may be mentioned that early rains after harvest give a cane that itself ripens early. Variety and Climate.—Most varieties of cane attain their maximum growth in the more essentially tropical districts. Some varieties, on the other hand, fail entirely when removed from these latter districts, and others, such as those peculiar to northern India, do not succeed in the tropics. It seems probable that adaptability to a colder climate is a characteristic of the red and purple canes. In a subsequent chapter it will be shown that the light and dark Cheribon (Transparent, Bamboo, &c.) canes in all pro- bability originated from striped canes. Stubbs*4 states that in the relatively cold climate of Louisiana a plantation of striped canes if not renewed tends to pass into one of all purple canes, and he classes this phenomenon as a case of the “‘survival of the fittest,” attributing to the purple colour a greater capacity to absorb heat. The cane known as Cavengerie, Port Mackay (in Mauritius), Louzier (in Argentina), Po-a-ole (in the West Indies), is also another instance of a dark- coloured cane being adapted to a cold climate. In the less tropical portions of South America this variety is one of the canes most widely grown. In the Hawaiian Islands, the Lahaina cane forms the bulk of the crop on the irrigated plantations in the arid districts, chiefly at a low altitude ; it is replaced by the Yellow Caledonia on the rainfall plantations situated mainly at a higher level, and hence with a colder climate. . Nitrogen% Pinar del Rio 66 0+ 48 C+ 44 0+ 40 0°25 Havana Be 30 1°57 0°37 O*51 On277 Matanzas... 13 1°62 0*30 oO: 71 0:21 StaiClarayy. ts 35 1.66 0° 33 O° 34 0°33 Camaguey .. 26 - 2°57 0°52 0+ 40 0:21 Oriente 5s 38 2°31 0*59 O42 0°22 CoMPosITION OF TyPICAL RED AND BLAcK CUBAN SOILS (CRAWLEY). PER CENT. RED SOILS. BLACK SOILS. Water 9°75 3°87 4:68 10°55 | 15°88 16°18 20°00 10°98 15°71 Insoluble 43°98 .62°46 37°79 42:00 | 51°69 57°13 57°96 51°93 48°92 Volatile 19°73 ==". 26°79. A297 | 15280) 10245 12:44) (On4Ameorae Humus — 0:63 — 5°63 4°82 2° 86. \\.2*. 42). 2% 6O™—emaay Ferric oxide TAs082 Lhe37 -12572) 613551) O792); lO: TL 16: 34-512. 6Cmeieeee Alumina 18°80 “13806 ~25°30 (27°00 |" 12988 15°70 (16°34 ~(S/O5eeeaamne Manganese O22 ic)? (Orne As2 2 Ore ostS 0:28 . 0°33. Os: TOgeoeuee Lime Oooh. .O-s 7a O15 Omit Onno 3-102) 2-108 1°76. 200 amon Magnesia 0:48 0:22 0°43 0°98 2°44 PITA) I-16 23'76) 2°45 Potash OWhS! OV OG OLS O25 07330 0° 1G) 0-72 | Ose aOene Soda OnLO O° 690 eT 700) 12:30 0-09 O-15 0748 0°86 0-80 Sulphuric acid OVO ae tO LO e427 0*1I0 OFnO! OWT Ov 15 7) O-20emOune Phosphoric acid ON5 Sia O20) OO OOF 0278 O72 A Ordg — Oa7 Or15 Nitrogen OVO. sO 7-5 60125) a Orme G34" > 0+ 35) * “O'20)) SOG RmOnAG Egyptian Soils——The Egyptian soils upon which the cane is culti- vated are in Upper Egypt, and lie in a narrow strip on both banks of the Nile ; the soil is all an alluvial deposit of great depth, overlying a basis of sand, and has been formed, and is continually renewed, by the overflow of the Nile. Numerous analyses have been made of these soils, many of which have been collected by Pellet and Roche.!? They remark :— “The soil of this district is very uniform in its general composition; the percentage of calcium carbonate is from 5 to 7, of sand from 20 to 60, of clay from 20 to 60, of humus 0-8 to 1:3. The very compact nature of the greater part of the soils attracts attention, and certainly influences to a greater or less extent the *Occasional samples testing over 20 per cent. of lime perhaps tend to make the average percentage of this material too high.—(N.D.). ———_—— THE SOILS OF THE CANE-GROWING REGIONS a3 availability of the fertilizing elements. Very remarkable is the presence, rare in arable soils, of a large quantity of magnesia, from 1 per cent. to 3 per cent. The fertilizing elements, properly so called, were found per kilogram :— Phosphoric acid [96,558 ~ -[°° 28,363 576 60°4 37°3 Twelve months a | 65,377. | 16,505 467 | 55°2 36°7 Thirteen months | 79,15¢ ' 17,750 468 | 39:8 29°0 ; { ; a] | Age of Cane. | Seca Potash. | Soda. | Lime. | Magnesia. | Silica. . / ere Means eal Obata aan Six months .. - 14°I 36-0 | 2:2 | 71 I3‘I 139°I Seven months ee Gactane 44°4 8-6 23°8 ES"5\i | 268- Eight months Se 18°7 79°0 7°9 26°1 24°6 200°5 Nine months as 20:0 79°7 0°7 28-4 25°7 245°3 Ten months = 21°9 97°3 21-4 46°7 26-2 322-0 Eleven months... I9*4 7 Aa eed ee Sa 58°4 36°7 =| +293°3 Twelve months .. | 14°3 G2<0;>|~=.8<8 33°70 25°Q;) | --23274 Thirteen months .. | = 17°3 62°6.-| — 7-0 38-0 27°5 | 210°5 A number of experiments have been made with the view to determining the effect of dividing the applications cf manure. In these experiments the manure has been applied at an early stage of the cane’s growth and generally within three months of planting. Nearly all these experiments show very little difference in the effect, and as typical of them the following, due to Ledeboer?* in Java, are quoted :— Lbs., sulphate of Cane, Yield ammonia per acre. Tons per acre. per cent. on cane. 0-308-154-0-0 aa 57°8 II*54 0-15 4-308-0-0 = -- 56°7 11°58 0-78-231I-154-0 .. ac 56-0 II-64 39-116-154-154-0.. = 59°0 II°57 39-39-154-I16-116 a7 58-2 11-48 Somewhat different conditions obtain in the Hawaiian Islands, where the cane is allowed in many cases a two years’ growth. There it has been found that considerable benefit arises from applications of nitrate of soda immediately before the second growing season. The Choice of Nitrogenous Manures.—Nitrogen can be applied to the soil as nitrates, as ammonia salts, as organic compounds and in the form of cyanamide. For the special purposes for which readily available nitrogen is used in cane cultivation choice is confined to nitrate of soda and to sulphate of ammonia. Nitrate of lime and cyanamide are not available in sufficient quantity, and the organic forms of nitrogen, such as oil-seed cakes and dried blood, have been found to have a much lower efficiency in regard to the cane than have the two first-mentioned materials. On general principles sulphate of ammonia is indicated as applicabie to soils containing a good 90 CHAPTER VI proportion of calcium carbonate, as in such soils nitrification proceeds rapidly. This argument, however, loses much force, as it has been shown in recent years by a long series of experiments, initiated by Pitsch in 1887, and completed by Miller and Hutchinson in 1909, that plants can utilize ammonia salts without their conversion into nitrates. On the other hand, when there is a very large quantity of calcium carbonate in the soil there is danger of loss of ammonia by volatilization. Another objection which is often raised against the use of ammonia salts is that their long-continued use may result in an acid reaction and consequent infertility in the soil. This action has been specially observed at the Woburn Experiment Station on light sandy soils, and has also been studied at several Experiment Stations in the United States. In Java and in Demerara, many years’ use has not resulted in this condition being cbserved, and Harrison!’ inclines to the belief that the Demerara scils have benefited thereby, an action he attributes to the alkaline nature of the subsoil water. In both these districts the results of experiments indicate the superiority of ammonia over nitrate, and a further reason for this may be found in the deflocculating action of nitrate of soda on the clay soils common to both localities. The use of nitrate is most extensive in the Hawaiian Islands, and it is also used to a considerable extent in Egypt and in Mauritius. The soil tvpe of the Hawaiian Islands is radically distinct from that of either Java or Demerara, and the deflocculating action on clays would be largely absent. Recently, however, some evidence has arisen that the long-continued use of nitrate there has resulted in the formation of “ black alkali”’ in certain soils, and to this cause is attributed the falling off in productivity of the Lahaina cane on certain plantations. An objection to the use of nitrate of soda in the tropics lies in its extremely deliquescent nature, an objection that loses much weight when the locality where it is used is an arid one, as is the case in many parts of the Hawaiian Islands. Where there is reason to suppose that either form is objectionable when long continued, a natural suggestion would be to use the two forms mixed or separately in alternate years. The use of oil-seed cake is almost entirely confined to those districts where it is produced, such as Louisiana, where large quantities of cotton seed cake are employed in cane culture. Choice of Phosphatie Manures.—All phosphates when applied to soils are fixed, and rendered insoluble; the rationale of the use of a soluble superphosphate, as opposed to the use of an insoluble phosphate, is that the solution of phosphoric acid is precipitated within the soil in a much finer state of division than can be obtained by grinding an insoluble phosphate, and mechanically ploughing it into the soil. Dependent on the type of the soil, the phosphoric acid will be precipitated within the soil as phosphate of lime, or iron or alumina. The former of these bodies is available to the plant, the latter is not; hence it is an axiom in manuring that superphos- phates are suitable for calcareous soils or such as contain a considerable proportion of lime carbonate. On heavy clays such as constitute the cane lands of British Guiana superphosphates are contraindicated. On such soils basic slag is the form of phosphatic manure from which benefit is to be ex- pected. It has been shown by many experiments that on clayey and peaty soils, where an alkaline base is required to neutralize the nitric acid formed by soil organisms, this form of phosphoric acid gives the best results. THE MANURING OF THE CANE oI Lime in Connection with Cane Growing.—A study of the analyses of the ash of the cane cannot lead to the conclusion that the cane is a calciophile plant, and Harrison® in his résumé of twenty-five years’ experimental study of the manurial requirements of the cane has come to the same conclusion. The benefits that follow the application of lime in many districts where the cane forms the staple crop must not then be considered as due to specific action of this material on the cane, but as due to its general effect in ameliora- tion of the soil. The action of lime may be briefly summarized :— 1. Correction of acidity in the soil, whether due to an excess of organic matter or due to long-continued application of ammonia salts. 2. Amelioration of the physical condition of heavy clays. 3. Rendering potash available. It is now generally considered better practice to apply moderate doses of lime, say 1,000 lbs. per acre, every five or six years, than to put on heavier applications less frequently. This is the general rule in the Hawaiian Islands, larger applications being only made on a few plantations possessing a distinctly sour soil with much organic matter. However, some heavy clay adobe soils have been treated there with success with as much as fifty tons of coral sand to the acre; this procedure recalls the system of marling once so prevalent in English agricultural practice. The form in which lime is applied is either as the carbonate or as quick- lime. Recent practice inclines very strongly to the use of the carbonate, to the exclusion of the caustic form. In addition, the fineness of division of the lime has been shown to have a very great bearing on its efficiency. The very extensive literature on this important point has been collated by Kopeloff,18 whose experiments point to ground limestone sifted through mesh 200 to the linear inch as being the most efficient form in which to make the application. A point of very great interest in connection with cane growing and one which has not, so far as the writer is aware, been thoroughly investigated, is the ‘‘ lime : magnesia’”’ ratio best suited for the cane. For cereal crops gener- ally, for rice, and for such as have a large leaf development, evidence has been brought forward by Loew!® and his pupils that the lime should be in excess of the magnesia in proportion from 1-5 to 2 times as great. In the absence of any evidence to the contrary it may perhaps be taken that a similar ratio holds for the cane. That an excess of magnesia has a deleterious effect on the cane has been shown by Eckart,?° who irrigated cane in tubs with both lime and magnesia chlorides, and found a much better growth when the lime was in excess of the magnesia than when the quantity of these two bodies was nearly the same. Quite recently Loew! in Porto Rico has gone further into the subject in special reference to the cane ; in that island he has found the soils containing an excess of magnesia over lime. He quotes an instance of a cane soil suffering from acidity, stiffness and an excess of magnesia over lime where an application of 3,000 lbs. lime per acre increased the yield of cane 57 per cent. He also writes: ‘‘ The most favourable ratio of lime to magnesia in the soil for cane will very probably be as 2 to I, if both are present in an equal state of availability. This can be inferred from experiments with maize by Bernadini.” 92 CHAPTER VI The hypothesis of Loew, though carefully elaborated, is not accepted by many agronomists; it has been followed up chiefly in Japan by Aso and others. The lime-magnesia ratio must apply to the soil water or to readily soluble forms in the soil ; a hydrochloric acid soil extract showing an excess of magnesia over lime would not be sufficient to condemn a soil on Loew's hypothesis. It is of interest to note that in some Demerara soil waters Harrison" has found that with sulphate of ammonia manuring, the molecular ratio of calcium-magnesium was I : 0-77; with nitrate of soda manuring it was I : 1°52, and with no manuring I : 2-40, and with no cultivation Toe S76 Yields of cane had become very deficient in the second and third cases, but Harrison does not commit himself to attach any special significance to these ratios. Effect of Manuring on the Composition of the Cane.—There is a wide-spread belief that heavy manuring adversely affects the quality of the juice of the cane, and under certain conditions this may be correct ; thus in a district such as Demerara, where a short period of growth obtains, a late manuring results in an impure juice. Possibly in such a case not only is the maturity of the crop delayed, but a second growth of young cane is stimulated and the comparison may become one of mature and of immature cane. Again, with heavy manuring, there is a consequent increase in the size of the crop with less access of direct sunshine, and a delayed ripening is the result. That judicious heavy manuring has no harmful effect is shown from the results regularly obtained in Hawaii; nowhere is a sweeter and purer juice obtained, and nowhere is the manuring more intense. Here, however, owing to climatic conditions peculiarly favourable, a great part of the harvest consists of fully matured cane cut at the period of maximum sweetness. Actual experiments on this point lead to somewhat contradictory results. Thus Eckart® found in Hawaii with unmanured cane a sucrose content in the juice of 18-26 and purity of 90-69, manured canes affording a juice containing from 16-40 per cent. to 17-85 per cent. sucrose, and of purity 89-16 to 90-60 Conversely, however, the same authority has supplied data of an experiment where, in three instances, an application of 1,200 lbs. of high grade mixed fertilizer and 300 lbs. of nitrate per acre not only enormously increased the yield, but gave a sweeter and purer juice. Of the specific effect of manures, many ideas, supported or not by experi- ment, may be met with. Lime is credited with producing a sweet and pure juice in the West Indian adage: ‘‘ The more lime in the field the less in the factory,” and this idea is reflected in the quotations in Chapter V. Phosphates are also believed to affect beneficially the sugar content of the cane, and potash is reputed to have the reverse effect ; Harrison’s ex- periments already quoted fail however to countenance this idea. There is a certain amount of evidence that canes heavily manured with readily available nitrogen are more susceptible to. fungus attacks than are others ; this may be due to the production of a soft-rinded cane due to rapid growth, and possibly in the presence of infected soil or material the nitro- genous matter may also benefit the development of the fungus. In Egypt, it may be mentioned, on lands controlled by the Daria Sanieh manuring of cane was not allowed. On the whole, the writer thinks that the bulk of the evidence points to weight of cane only as being affected ; differences which may from time to THE MANURING OF THE CANE 93 time be observed are probably due to different degrees of maturity or to other uncontrollable factors vitiating the comparison. The Ash of a Plant in Relation to Manuring.—It has been thought that the analysis of the ash of a plant and the agricultural balance sheet would give information as to the proper combination of manures to apply; this idea demands that for any plant there is one particular ash analysis which is most suited for it. The variation, however, is so great that no “ best ash ”’ for the cane can be obtained, and this captivating hypothesis breaks down on subjection to scrutiny, or rather is not supported, as regards the cane, by sufficient evidence. It is conceivable, however, that an ash analysis showing a low proportion of, say, lime might point to a deficiency of available lime in the soil; on the other hand, a deficiency of lime in the soil might be reflected in small crops rather than in a low percentage of lime in the ash. Connected with this subject is the “‘ Analysis of the Soil by means of the Ash’”’ ; this point has been recently studied by Hall,?? who thus summarizes his results, obtained, of course, in a temperate climate (England), but none the less generally applicable :— I. The proportion of phosphoric acid and of potash in the ash of any given plant varies with the amount of these substances available in the soil, as measured by the response of the crops to phosphatic or potassic manures respectively. 2. The extent of the variation due to this cause is limited, and is often no greater than the variations due to season, or than the other variations induced by differences in the supply of non-essential ash constituents—soda, lime, &c. 3. The fluctuations in the composition of the ash are reduced to a minimum in the case of organs of plants, which, like the grain of cereals or the tubers of potatoes, are manufactured by the plant from material previously assimilated. The composition of the ash of the cereals is less affected by changes in the composition of the soil than is that of root crops like swedes and mangels. 5. Thecomposition of the ash of mangels grown without manure on a particu- lar soil gives a valuable indication of the requirements of the soil for potash manur- ing. Similarly, the phosphoric acid requirements are well indicated by the compo- sition of the ash of unmanured swedes, though in this case determination of the citric acid soluble phosphoric acid in the soil gives even more decisive information. 6. Pending the determination of phosphoric acid and potash “‘ constants ”’ for some test plant occurring naturally on unmanured land, the interpretation of soil conditions from analyses of plant ashes is not a practicable method by which chemical analysis of the soil can be displaced. The effect of the soil on the composition of the ash of the cane is well shown in some observations of Burgess*® dealing with Hawaiian soils quoted below :— CORRELATION BETWEEN POTASH IN SOIL AND POTASH IN MoLAssEs, {BURGESS). Puna-Hilo. Hamakua- Kohala. Kaui. Hilo. Per cent. Per cent. _ Percent. . Per cent: Potash sol. in hot hydrochloric acid 0-060 0*220 0° 442 0-208 Potash sol. in 1% citricacid .. O*OIII 0*0257 0-0266 0*0533 Potash in molasses Se oe I*575 2°*749 4° 224 3°877 Potash in ash of molasses... r7°8 26:4 35°1 38°3 Burgess considers that potash manuring is indicated as advisable for the soils of the Puna-Hilo district, where there is a very distinct correlation between the potash in the soil as indicated by analysis and that found in the molasses afforded by canes there grown. 94 CHAPTER: VI THE MANURES EMPLOYED IN SUGAR CULTIVATION. Artificial Manures.—This term is employed to denote manufactured products as opposed to farmyard or pen manure considered as a “ natural ”’ manure. For convenience of reference their properties and composition are briefly mentioned here. Sulphate of Ammonia.—The pure body contains 21°21 per cent. nitrogen and as found on the market contains about 20 per cent. nitrogen. Nitrate of Soda.—This material is extremely hygroscopic. The pure body contains 16°5 per cent. nitrogen, the commercial body containing about 4 per cent. of impurities ; these impurities are in English commerce grouped together under the peculiar term of refraction. Nitrate of Potash—The pure body contains 13-8 per cent. nitrogen, and 46°5 per cent. of potash ; it is but seldom used as a manure, the supply being devoted to other purposes ; in an impure form it however finds its way to Mauritius from India, and being of local occurrence is used to a certain extent in Egypt. Seed Cake Manures.—The refuse of seeds, etc., that have been crushed for oil, comes into the market in large quantities as manure. The plants that most largely contribute are cotton, flax, castor oil, coconut ; their composition of course varies with the origin. In general these manures can be used only in the country of their origin, drawbacks of freight prohibiting their more extended use. Some analyses of these materials, collected from various sources, are given below :— Nitrogen per cent. Ground nut (Avachis hypogea) bec -+ 4*06—7°94 Kapok meal (Eviodendron anfractuosum) 4° 40 Castor cake (Ricinus communis) 4°20 Coconut meal (Cocos nucifera) 3°62 Cotton-seed meal (Gossypium sp.) 7°00 ots (So 3 Soja cake (Soja hispida) Dried blood, as it comes on the market, contains from. Io per cent. to 16 per cent. of nitrogen. Fish scrap is of very variable composition, containing from 5 per cent. to 8 per cent. nitrogen, and from 5 per cent. to 7 per cent. phosphoric acid. Tankage is the residue from meat packing houses, and is of variable composition; as it contains considerable quantities of bone it is also a phosphatic manure. It is similar in action and composition to fish scrap. Guano.—The original Peruvian guano has long been exhausted, and the guanos now on the market are of recent origin. They differ much in com- position from those of long accumulation. Some bat guanos contain an extraordinarily high amount of nitrogen, reaching up to 30 per cent. Cyanamide is a synthetic compound of the formula CaCN, ; it is sold under the name lime nitrogen, German nitrate, or even as lime nitrate, from which it must be carefully distinguished ; as it appears in commerce it con- tains about 20 per cent. of nitrogen. Nitrate of lime is manufactured and put on the market as a basic nitrate of composition Ca (OH) NO,. It contains about 12 per cent. of nitrogen. THE MANURING OF THE CANE 95 Gypsum.—tThis material is sulphate of lime, and, in a sense, can not be regarded as a manure; it acts indirectly as a source of potash, which it sets free in soils ; it is also used as a corrective of soil alkalinity. Bone manures contain from 4 per cent. to 6 per cent. of nitrogen, and from 40 per cent. to 50 per cent. of phosphate of lime; this form of manure is sold as half-inch, quarter-inch, or as bone meal or dust, and is frequently steamed to remove the fats. The nitrogen is of little availability, and the phosphates, unless the bones are finely ground, are but slowly assimilated. Mineral phosphates contain from 25 per cent. to 35 per cent. of phosphoric acid, and are occasionally used without previous treatment intended to render the phosphoric acid soluble. Superphosphates usually contain about 20 per cent. soluble phosphoric acid, and in the form known to the trade as “‘ double superphosphate ”’ up to 40 to 50 per cent. They are prepared from mineral phosphates by the action of sulphuric acid. . Basic slag is the material obtained as a waste product in the “ basic ”’ process of steel manufacture; it usually contains from 15 to 20 per cent. phosphoric acid, and from 40 to 50 per cent. of lime, a portion of which exists as free lime. Reverted phosphate is the name given to a form of phosphate insoluble in water but soluble in ammonium citrate solution, and which is valued at the same figure as water-soluble phosphate. Superphosphates have a tendency on storage to pass into reverted phosphate, and this form is also manufactured and sold as precipitated phosphate, containing from 35 to 40 per cent. phosphoric acid soluble in ammonium citrate. Potash.—Potash is applied in cane-growing countries as pure sulphate containing about 48 per cent. potash. The chloride is occasionally used, and kainit and other crude salts appear occasionally in mixed manures. Green Manuring.—Green soiling or green manuring is a practice which has been carried on for generations past. In Europe the method employed is to sow a catch crop of some quickly growing plant between the harvest of the one and the seed time of the succeeding crop; the catch crop is ploughed into the soil and acts as a green manure to the following crop. The principles of this practice are as follows. It had been known for a large number of years that leguminous crops (beans, peas, clover, etc.), although they contained large amounts of nitrogen, did not respond to nitrogenous manurings, and even frequently gave a smaller crop when manured with nitrogen than when unmanured. It was eventually established by Hellriegel and Wilfarth in Germany, about 1886, that leguminous plants are able to absorb nitrogen from the air. The absorption is not made directly by the plant, but by the agency of bacteria. If the roots of a leguminous plant be examined, there will be found attached to its rootlets a number of wart-like excrescences the size of a pin’s head and upwards. These bodies, which are termed nodules, on being crushed and examined under the microscope, are found to consist of countless numbers of bacteria; these bacteria, living in symbiosis or commensalism with the host plant, supply it with, at any rate, a part of its nitrogen. If then leguminous plants be sown and allowed to reach maturity, and 96 - CHAPTER VI then be ploughed into the soil, there is placed in the soil a large amount of nitrogen obtained from the air. Green manuring is practised most extensively in Mauritius and in Louisiana, and also to an increasing extent in Hawaii and Cuba. In Louisiana, after plant cane and first ratoons have been grown, the land is sown with cow peas (Vigna unguiculata), using from one to three bushels per acre ; in August or September the peas are ploughed in and cane planted in October. According to Stubbs, the crop of cow peas above ground is often removed as fodder for cattle, planters who do this holding that the roots supply sufficient nitrogen for the crop, but Stubbs states that when the green crop is ploughed in, an average increase over plant and first ratoon cane of 7-42 tons per acre is obtained over that secured when the green crop is removed for fodder ; the amount of nitrogen afforded by a crop of cow peas is, according to Stubbs, about Ioo lbs. per acre. In Mauritius there are four crops used as green manures :—1. The Pois d’Achéry (Phaseolus lunatus). 2. The Pois Muscat.* 3. Pigeon Pea (Cajanus indicus). 4. Indigo sauvage (Tephrosia candida). The first two are pea vines growing in dense thick matted masses. The pigeon pea is a shrub growing to a height of four or six feet ; the indigo sauvage is also a shrub, but of rather more robust habit. Thesystem generally followed is to grow cane up to third ratoons ; the land is then planted with one or other of the above crops, the time during which it is rested under the leguminous crop being from one to three years, dependent on the iand available. Where land sufficient for one year’s rest only is available, the pois muscat is generally grown; the pois d’ Achéry is generally allowed to grow for two years, and the pigeon pea and indigo for three or four. All four crops are planted from seed, which is sown about 15 to 18 inches apart. Where no land can be spared to rest, one or other of the above crops is occa- sionally sown between the rows of cane, and after a few months’ growth cut down and buried. Although the benefits of green manuring are undoubted, it must be remembered that the expenses connected with it are not small, and very possibly where virgin soil can be had in abundance it may for a time be more economical continually to take in new land than to renew the fertility of old. The benefits of green manuring are most pronounced on estates which have continually to plant on the same soil; such estates are found in Mauritius, Barbados, and other small islands. Besides placing in the soil a supply of readily available nitrogen, green manuring has other advantages. I. The advantages of a rotation are obtained. 2. The deep tap-roots of leguminous plants bring available plant food from the subsoil to the surface soil. 3. The ill effects of a naked fallow are avoided. 4. The interposition of a crop other than cane will act as a prophylactic towards fungus diseases and attacks of insects, for if the habitat of these parasites be removed for any length of time it must result in their diminution or disappearance from lack of food. *The legumes known generally as “‘ velvet beans’’ and in various parts of the world as Mauritius beans Bengal beans or Florida beans, were formerly putin the genus Mucuna. Following Bort, Bulletin 141, U.S. Dept. of Agric. Bur. of Plant Indus., they are to be placed in the genus Stizolobium. The Florida bean is classe as S. deeringianum and has small marbled seeds ; the Mauritius bean, S. aterrimum, has black seeds; tie Lyon velvet bean, S. nivewm, has ashy seeds, and the Brazilian velvet bean, S. pachylobium, has black and white seeds, Some systematists would not admit these distinctions as being specific, and the beans as grown in Mauritius have black, white and marbled seeds, to the writer’s knowledge. THE MANURING OF THE CANE 97 In certain quarters, notably in Mauritius, after land has been under ieguminosz for a time, it is prepared for cane cultivation again by burning off the green above-ground crop. This process would seem to destroy the very benefits to obtain which the green manure was planted. Planters who follow this system claim as good a result as when the green crop is buried, and point to the saving in expense. To obtain definite information as to this process the writer once grew on small plots equal to =}, of an acre crops of the Phaszolus lunatus and Stizolobium sp. The results calculated out to an acre were as below. The crop in both cases was six months between planting and harvesting, which was done when the seeds were ripe. Phaseolus Stizo- lunatus. lobium sp. Kilog. Kilog. Weight, dry matter, in green crop 1621 “ease & (x beans 2 132 -= 466 =i is roots =. 123 x 80 Nitrogen ,, im green crop 30°3 54°0 - e roots Ae I°2 O-7 x beans 5°6 16°7 Potash .» im green crop 42:0 46°5 = - troots = 4°4 2 a5 # beans I-2 9°5 Phosphoric acid in green crop II*4 I4°4 Bs P roots : ras O°4 53 be beans a O-7 4°2 It will be seen that about 80 per cent. of the eal value of the crop was contained in the green crop ; if this is burnt off the nitrogen is lost, but the potash and phosphoric acid remain in a form readily available for the coming crop of cane. The economy of burning off the green crop and losing the nitrogen is comparable with the practice of burning off trash; in any case there is obtained a large amount of mineral plant-food brought up from the subsoil. The high nitrogen content of the bean straw, and the possi- bility of using this material as bedding for plantation stock, and thus both conserving it and obtaining a pen manure rich in nitrogen, is worthy of notice. Among other plants grown in tropical countries as green manure are Sesbania egyptiaca, Crotalaria juncea and C. laburnifolia, Phaseolus semterec- tus, Arachis hypogea (the earth nut), Soja hispida (the soy bean), Dolichos lablab (the bonavist bean), Phascolus mungo (woolly pyrol), Indigo tinctorta (the indigo of commerce), and, in Hawaii, Italian lupines, the plant which was used by the ancient Romans for the same purpose. De Sornay,”* who has made a most detailed study of green manuring under tropical conditions, has given the following crop results obtained experimentally in Mauritius :— WEIGHT OF CROP OF GREEN MANURES (DE SORNAY). Weight of Green Crop. Nitrogen in Green Crop, Plant. Ibs. per acre. Ibs. per acre. Cow peas (yellow) oe =. 50,200 ore 190 Cow peas (grey} == 2 51,000 = 219 Jack bean* : ee 22 28,000 a 210 Pois Muscat (black) ara a 42,000 ot 210 Pois Muscat (white) .. a 34,700 x 187 Pois Muscat (marbled) =e 34,500 RF 248 Pois d’Achéry .. a ae 23,100 tc 83 Pois amberiquef zs : 42,600 226 When grown between the rows or ae eee th with the cane, the crop amounts to about one quarter that recorded above. *Canavalia eusiformis. 7Phaseolus helvolutus. 98 CHAPTER VI Pen Manure.—In those countries which employ animal traction very large numbers of cattle and mules are kept for transport purposes, and large quantities of pen manure are produced annually, and it is remunerative to stall the cattle at night with sufficient litter, such as dry cane trash, to absorb their urine. In Mauritius and the British West Indies great attention is paid to this source of manure. The method adopted in Mauritius is as follows :— The live stock of the estate, which may number from two to three hundred, are in great part kept in “ parcs,” which may be from fifty to a hundred yards square ; a portion of the parc is often covered in to provide shelter in inclement weather. The whole area is covered with cane trash transported from the fields and used as bedding. During the whole year if the supply of labour is sufficient, the soiled litter is in a continual process of renewal and removal, the bedding being replaced throughout on an average once a week ; on removal it is placed on stone platforms or in basins ten feet deep, both platforms and basins generally being about fifty feet square. The whole mass when completed is continually watered with fermented molasses and water or distillery refuse, and sometimes with dilute sulphuric acid; the drainings collect in stone pits and are continually repumped over the heap of manure; the object of this is to rot the manure and at the same time to fix any volatile ammonia given off. In from six to twelve months the manure is considered sufficiently rotten to place on the fields, where it is applied at the rate of from ten to twenty tons per acre to plant canes only, generally at an age of three months ; or occasionally the cane holes are filled with the manure and the tops planted on it. The amount of manure made per animal per year is from fifteen to twenty tons where bedding is. used, and, where the dry dung only is collected, from two to three tons. With the introduction of mechanical traction the quantity of pen manure available has decreased. At first sight it would appear to be false economy to attempt to force the production of manure by bringing in more material than is necessary to absorb the urine and to contribute to the comfort of the animal as bedding. Watts?>, however, advised a contrary procedure, and is inclined to believe that the raw material rotted by the action of bacteria becomes much more efficacious. The composition of the manure varies within considerable limits ; where a reasonable amount of bedding has been used, the percentage of nitrogen generally, in the writer’s experience, lies between 0°6 and 0°8 per cent., falling to 0°3 to 0°5 per cent. where an excess of trash has been brought to the stables or pens ; the potash and phosphoric acid do not seem to show any variation dependent on the amount of bedding used, both lying between the values 0°2 to 0°7 per cent.; these figures refer to manure with from 70 to 80 per cent. of moisture. The expense of making pen manure is very considerable ; the cost in Mauritius before the Great War varied from two to five shillings per ton, a portion of which expense would be incurred in any case; the carting and application cost about one shilling per ton, making the total outlay from three to six shillings per ton. Pen manure is almost exclusively applied to the plant crop. In Mauritius the holes in which the canes are planted are some- times filled with material, and otherwise it may be distributed round the base of the stools of cane when a few months old. In other districts where mechanical tillage is in operation, pen manure and similar material is broad- THE MANURING OF THE CANE 99 casted by manure distributors and incorporated in the soil by harrows in the operations previous to planting. The experiments with pen manure in the British West Indies point to the conclusion that applications to plant canes followed by the use of readily available nitrogen on ratoon crops give the best financial returns. With the general increase in the size of estates and consequent necessity for mechanical traction, pen manure is losing its importance, and its place is being taken by artificial fertilizers. The fertility of soils in districts such as Barbados and Mauritius over many generations is, the writer believes, to be largely attributed to the extensive and well-ordered use of the pen manure manufactured on the estates. The modern tendency is to grow crops with the aid of irrigation and of the more concentrated artificial manures, and it largely becomes a question of the cost of the labour required to make and to apply the pen manure compared with that required for the purchase and application of the artificial manure. It is not yet known what will be the final effect on the soil in several generations of the modern practice. The Return of Plant Residues.—Considered as a principle in agriculture, everything produced from the soil, except that portion which forms the commodity which is marketed, should be returned to the soil. Generations of experience have established this principle in the older civilization, and to its observance is to be attributed the long-continued productivity of the soils of Europe and of Asia. To its neglect is to be assigned the continued march westward of American farming. The very many analyses which have been made of the cane afford means to construct a balance sheet of the demands made by the cane on the soil, and of the distribution of the plant food re- moved. The analyses quoted in Chapter II, however, show that from analysis to analysis very great difference results. Reviewing, however, a great mass of data the following balance sheet can be presented, as giving an average of the essential features, with the proviso attached that individual analyses can be found showing very different results :— AGRICULTURAL BALANCE SHEET OF A CANE CROP. LBs. PER I,000 TONS OF STALKS, Phosphoric Lime. Potash. acid. Nitrogen. Leaves, Tops, Roots 2000 7500 I1I0oO 2500 Stalks .. ie aa 500 3000 1000 1000 Sugars .. zie be 50 550 15 50 Molasses =e rc 250 2150 95 250 Bagasse at se 50 300 100 100 Press cake Sr ae 750 a 790 600 In the construction of this balance sheet the manufacture of 96° test sugar is assumed together with a high extraction at the mill. It is at once ‘apparent that the distribution of the elements brought to the factory with the stalks will vary with the ‘“‘ extraction”’ and by the distribution of the output between sugar and molasses. This in turn will be controlled by the purity of the juice. In constructing the table, allowance is made for the quantity of lime used in defecation. Inspection of the tabulated statement shows that the greater proportion of the material removed from the soil by the crop is contained in the residue 100 Le Ae CHAPTER VI of leaves, tops and roots, which normally remain on the land. In the case of the phosphoric acid, however, the division between stalks and residues is approximately equal. As regards the material entering the factory, 70 per cent. of the potash is found in the molasses, 20 per cent. in the sugars and 10 per cent. in the bagasse. Of the phosphoric acid, 80 per cent. appears in the press cake, Io per cent. in both bagasse and molasses, and only a very small quantity in the sugars. Of the nitrogen, 60 per cent. is accounted for in the press cake, 25 per cent. passes to the molasses, Io per cent. is found in the bagasse and 5 per cent. in the sugars. That quantity which appears in the molasses is mainly in amide form, the albuminoid nitrogen being pre- cipitated in the defecation process. Of the lime the press cake contains 50 per cent. more than is introduced with the stalks, most of the balance going to the molasses. Based, however, on the whole amount of matter taken from the soil, only 20 per cent. of the potash is found in the molasses, 5 per cent. in the sugars, 3 per cent. in the bagasse, the balance, approximately 70 per cent., appearing in the leaves, etc. Of the total amount of phosphoric acid, half remains in the leaves and half is found in the factory products, the press cake accounting for the major portion. Similarly, the leaves, etc., contain 70 per cent. of the nitrogen, 60 per cent. of the remainder being found in the press cake, with most of the remainder in the molasses. It follows, then, that the sugar cane cannot be considered an exhaustive crop since so much of the material removed from the soil issactually returned or capable of being returned thereto. The agricultural economy of a plantation is influenced by the way these crop residues are treated. . Considering first the material contained in the stalks, the greatest possible source of loss is in the molasses. Practice differs as to its disposal. In Cuba nearly always, in Java and in Hawaii very often, the molasses are sold as a part of the crop, or failing to find a mar- ket are run to waste. Prior to 1914, the price of molasses in Cuba at the plantation was about 24 cents per U.S. gallon, or $4.00 per short ton, and equivalent prices prevailed elsewhere. A short ton of molasses will contain on an average 8o lbs. of potash, which at 5 cents per Ib., the then price for a lb. of potash in high-grade material, exactly equals the price paid for the molasses sold nominally on its content of sugars. Considered, then, from the point of view of the agricultural economist, the sale of molasses off the plantation should be condemned. The value of the potash thus annually removed is very great. The world’s production of cane sugar now (1919) amounts to about 13,000,000 tons, and the molasses corresponding to this quantity will contain about 130,000 tons of potash of value $13,000,000 at pre-war prices for the potash alone, together with another $4,000,000 on account of the nitrogen. The most natural method of its utilization would be in the production of alcohol, with the recovery and return to the soil of the distillery ‘“‘ slop ” or at least with the recovery of the potash, as is often done in beet distilleries on the continent of Europe. In some districts, notably Demerara, Peru and Natal, the distillery often forms an integral part of the plantation, - but generally only the manufacture of alcohol is considered, the waste product being neglected. Many years ago, however, a Demerara plantation, ‘‘ Montrose,” installed a ‘“‘lees”’ irrigation plant, which unfortunately only operated a short time prior to the destruction by fire of the distillery. Some attempt is, however, made there to dig out periodically the “lees ” pond, and return the bulky evil-smelling material to the fields. Possibly THE MANURING OF THE CANE Ior in the future the development of the internal combustion engine using alcohol may stimulate each plantation to thus provide its own source of power for ploughs and locomotives, together with the retention of the material removed from the soil. Tnterest in the return of the molasses to the soil as manure was stimulated by the results obtained in 1908 by Ebbels and Fauque?® in Mauritius, and since then numerous experiments have given rather discordant results. Harrison,?’ for example, in Demerara found no increased yield following on the application of molasses, but the results in Java,!* quoted below, indicate a real benefit, probably, as pointed to by the returns, due to the sugars and not to the potash or nitrogen. ACTION OF MOLASSES ON THE YIELD OF SUGAR CANE. Cane. Sugar. Cane. Sugar. Tons Tons Tons Tons Application per acre. per acre. peracre. per acre. per acre. I. 545]bs.ammonia sulphate .. 69 6-6 61 7:0 2. Asin 1, with 2350 lbs. molasses 81 6:8 74 7°6 3. As in I, with the nitrogen in the molasses as ammonia.. 71 6°7 65 7°4 4. As int, with the sites in the molasses 72 6-6 66 7°4 5. As int, with the sugar in the molasses 75 6:8 68 7°6 Very similar results were obtained by Boname?® in Mauritius with an application of one litre (3 Ibs.) of molasses per hole (3,000 holes to the acre). The action of molasses on soils has been examined by Peck,?® who found that following its application there is first a decrease in the nitrogen in the soil due to denitrification followed by an eventual increase over and above the quantity originally present. He therefore recommends that when molasses are returned to the soil an interval should elapse between the time of application and planting. The bagasse ashes contain a considerable quantity of potash and phos- phoric acid, and that proportion of this material which is recoverable is usually taken back to the fields alone, or else mixed with press cake or other material. Much of the potash, however, appears in the form of a potash glass or slag, and much is also carried forward in a volatile state into the flues and is lost. The press cake is particularly rich in nitrogen and in phosphates. Analyses on record show much variation. Expressed as a percentage on dry matter, Harrison®® found in three samples 1°67, 2°44, and-1-o8 per cent. _Geerligs*! in Java found from 2 to 4 per cent., and expressed on actual material Ledeboer® found from 0°66 to 1°59 per cent. The percentage of phosphoric acid averages about 3 per cent. on dry weight. Press cake is a material of the same nature as pen manure, and its effects are dispropor- tionate to the quantity of nitrogen and phosphoric acid it contains. It is usually applied at the rate of five tons per acre, and is indicated as being most suitable for light, sandy soils. By far the greater quantity of plant food removed from the soil is con- tained in the leaves and other waste matter. Estimating that 1,000 tons of cane contain 2,500 lbs. of nitrogen, and that the world’s output of cane is now 130,000,000 tons, the value of the nitrogen therein contained at pre-war prices amounts to about $100,000,000, and a very great proportion of this is annually wasted in the combustion of the trash. This custom obtains 102 CHAPTER VI generally in the Hawaiian Islands, in Demerara, and in Java where the fields after the cane harvest are turned over to the native Javanese for rice culture. In Mauritius, however, much of the trash is used as bedding for the plantation stock, and thus finds its way back to the soil as pen manure, and a similar routine obtains in the British West Indies. In Cuba it is the almost invariable custom to let the trash rot on the fields, where it remains as a blanket. It thus not only is returned to the soil, but equally acts as a mulch preventing surface evaporation, and to this custom the long-continued fertility of much of the Cuban cane lands is to be attributed. In those districts where the trash is burned off either before cutting or afterwards, it is not ignorance that causes the custom to obtain, but rather lack of labour or absence of means of satisfactorily burying or turning under the very bulky mass of material. Apart from the value of the nitrogen, the presence of decaying vegetable matter in the soil has an important bearing on its fertility in regard to the formation of humus and in increasing the water-holding capacity of the soil, and in this connection it may be remarked that those plantations on the island of Hawaii that have made a practice of turning under the trash always suffer less during a drought than do those which habitually burn it off. During the period 1go1-13 extensive experiments were made on a Hawaiian plantation, in all 109,990 tons of trash being buried. The effect of this procedure is thus described :—** ““ Where two ratoons were formerly the maximum, four are now becoming the rule. The yields, instead of decreasing with each subsequent ratoon, have in- creased. The 1908 crop was the first to have trash left over its entire ratoon area. That and the succeeding crops show an average yield of 4-102 tons of sugai per acre ; the seven preceding crops gave 3+ 329 tons of sugar per acre. The 1914 crop to date has yielded 5-2 tons per acre and is expected to go still higher. While all the credit cannot be given to trash, there is no doubt whatsoever that leaving the trash has been the principal factor.”’ The actual operations there followed on a rainfall plantation are described by Larsen? :— “ After the cane is cut the trash is hoed away from the stools into the furrow. This work requires about two men per acre per day and is called “ palipali-ing.”” This is followed by offbarring, which consists cf ploughing off or away from the stools. The soil by this operation is thrown against and partly over the trash and assists. materially in hastening itsdecay. A 10, 12, or 14-inch plough is used for offbarring. A revolving knife or sharp coulter is attached to the plough-beam to make a clean cut ahead of the plough. One man with two mules can offbar 2 to 24 acres per day. After offbarring hoeingis done in the cane lines. In the furrow, that is, between the lines of cane, the weeds in most cases are kept down effectively by the trash. Cultivation between the rows begins from one to two months after pali-pali- ing. After two or three mcre hoeings in the cane rows as occasion demands and as many more cultivations the trash will have become so thoroughly broken up and disintegrated that the furrow can be small-ploughed without trouble. A small 8-inch plough is run usually four times through the furrow to loosen up the soil and to mix in the trash. After small-ploughing the cane is hilled. This is done with hoes, ploughs, double mould-boards, or discs. With this operation the rotted and partly rotted trash is thrown toward the cane and is more thoroughly buried and mixed with the soil.”’ In certain soils in Demerara the presence of decaying trash has according to Harrison* a specific function in neutralizing the effect of the large quantity of alkaline soil water there present. On this point he writes :— “In experiments in which (1) soil water was allowed to evaporate into the air and (2) caused to evaporate in an atmosphere consisting almost entirely of free carbon dioxide, it was observed that when the evaporation takes place in air, THE MANURING OF THE CANE 103 nearly free from carbon dioxide gas, practically the whole of the lime salts are deposited as calcium carbonate, while the water is being concentrated to one-third of its original bulk, and the remaining water becomes a saline one, containing large quantities of magnesium salts as chlorides, sulphates and caibonates in soiution. The calcium salts, which are known to exercise a profound influence in reducing the highly toxic action of the magnesium chloride and carbonate on plants, are almost wholly removed from solution and the soil water becomes in a condition which is poisonous to vegetation ; this is probably what takes place during pro- longed periods of dry weather on more or less worn-out cane soils, in which by injudicious cultivation and especially by long-continued destruction of the trash by burning the normal proportion of organic matter has been largely reduced. When, on the other hand, the evaporation takes place in an atmosphere heavily charged with carbon dioxide, as in the air present in soils containing the proportion of organic matter normal to good soils, the calcium salts remain for a long time in solution until the fiquid commences to become a saturated brine, and this for a prolonged period continues to modify the toxic action of the magnesium salts. It is possible on such land that the soil water during drought may become con- centrated in the upper layers of the soil, without any material injury to the plant, until by concentration of the soil water the toxic action of the magnesium salts exerts itself.” It used to be one of the boasts of German agricultural economists that, in exchanging white sugar for cereals, they robbed America of much of its potential fertility, while offering nothing in exchange, since the sugar was composed entirely of materials supplied by water and carbon dioxide. There is much truth in this boast, and it is to be noted that the policy of the German Empire was to retain the molasses at home, and use it as one of the means to build up a great alcohol industry. If such a policy were to _be followed in the tropics there should be no such thing as exhausted soils, and on the contrary the lands should with continued cultivation become more and more fertile, and it should even be possible to grow heavy crops continuously without resort to supplies of readily available nitrogen, although with this additional stimulus there is nothing to indicate that the profits might not be ever yet increased. It is finally to be noted that white sugar manufacture alone in place of raw does not result in the retention of the greater part of the plant food unless the molasses also are reserved, for the manufacture of white sugar only results in transferring a small proportion of the plant food from the raw sugar to the molasses, and if these are removed the total loss remains the same. Rotations.— Different crops have a predilection for different forms of mineral matter, and thus remove from the soil very different amounts of the different constituents of plant food, so much so that the ash of a crop may consist in general of one predominant constituent. By growing continually one and the same crop on the same piece of land there is then a tendency to exhaust one particular constituent. If, however, different crops be grown in rotation, an element of plant food which was removed in large quantities in one year is not absorbed to such an extent by the succeeding crop, and by the time the crop first in rotation is planted a second time a sufficiency of the particular material exhausted by this crop will have become available, due to the natural process of disintegration which soils are continually under- going. Asan example of such a rotation, the Norfolk system may be quoted. This is wheat, roots, barley, clover; the roots are consumers of potash, the wheat takes up phosphates, the barley absorbs silica, and the clover feeds largely on lime and magnesia. Tt is especially to be noted in this rotation that the wheat follows the leguminous crop of clover; wheat is a crop that responds to a supply of | Dec. a= 1976 fle AGT eames | - =/ 978 ng) 7 = lees tl cee In | | 104 CHAPTER. VI nitrogen, in this case in part provided by the root residues of the clover ; the cane, too,-demands, as is shown in the manurial trials quoted above, for its successful growth a supply of readily available nitrogen, and in certain districts a leguminous crop precedes the cane crop. : Cane-growing districts may be divided into those where the cane forms the sole output of the soil, and those where it is alternated with other crops. Into the first category fall the districts of Cuba, the Hawaiian Islands, British Guiana, Trinidad, Fiji and Peru. In Java, Egypt and British India, a complete rotation is practised, and in Louisiana and Mauritius the cane fields are rotated with leguminous c crops which are.ploughed in. 7: Fe RRR In Egypt, on the lands controlled E\ by the Daria Sanieh Co., cane was Yo une NS ete x) grown for two years, preceded by a ® 7 RRR oer | SN\ year’s fallow ; following on the cane Nea _ crop, corn and clover were grown ; REE | the cane itself was not manured, with -.j the object of obtaining a sweet cane. <8:| Private owners follow a rotation of ~ | clover, wheat, cane (no ratoonage), and manure the cane heavily. In Louisiana the general rotation er] is plant cane, ratoons, and cow peas SS (Vigna unguiculata) ploughed in as a green manure. In Mauritius it is general to grow \\ cane up to third ratoons, after which 2 a green leguminous crop occupies the i; land for from one to four years. In Java the system of land tenure =~ enforces a rotation. Land suitable for rice cultivation (sawah) is leased by the native Javanese in perpetuity, | and may not be rented by Europeans eet ees! fora period exceeding eighteen months, ine. NEES NNW 2) after which the native is obliged to RSENS cultivate it for an equal period. Dur- = aoe pao ee eee ing this period the native takes off ! two rice and two dry land crops; the Fic. 19 rice crops eccupy the land for six months each, the dry land crops only taking three months apiece. Almost alwaysa dry land crop follows a cane crop, and cane follows rice, the commonest rotation being :—Cane, ground provisions (dry crop), rice (wet crop), ground provisions, rice, cane. In ground provisions are included ground nuts, beans, maize, cassava and yams, so that not infrequently legumes enter into the rotation. The diagram in Fig. 19 indicates the sequence of crops and the way an area of land is subdivided at any period.* Lands not suited to rice cultivation may be alienated to Europeans, and on them a continuous crop of cane may be grown. These lands, however, form only a small part of the cane fields of Java. *For this diagram, and for other information concerning Tava methods, I am indebted to Dr. H. L. Lyon. THE MANURING OF THE CANE 105 ~~ Where the sugar cane forms the main crop in India, the following typical rotations, amongst others, are given by Mukerji :—* Bengal.—High and light soils. Rice (May to September) ; pulse or oil seed (October to March); jute (April to September); pulse or oil seed (October to March); rice (May to September); potatoes (October to February) ; sugar cane (February to February) ; rice (May to September) ; pulse (Octéber to March), &c. Punjab.—Dhaincha (Sesbania aculeata )or sunn hemp (Crotalaria juncea), or cow peas (Vigna unguiculata) cut in bloom in August ;_ potatoes (October to February) ; sugar cane (February to February) ; pigeon pea (Cajanus qndicus) or rice; potatoes; sugar cane. Whenever practised the absence of a rotation is a weak point in sugar cane culture; the rich fertile soils which are often met with in the tropics for a number of years support a continuous unvaried crop, but eventually _ they tend to become barren. Im certain countries, as Demerara, where abundance of virgin soil awaits cultivation, proprietors can continually empolder new lands and allow that which has become barren to lie fallow, and after a space of time, during which by the continued disintegration of the soil plant food has become available, again plant the old abandoned land. The effect of continuously growing cane on the same soil has not been, so far as the writer is aware, distinctly studied, but the following quotation from A. D. Hall®® with reference to the Rothamsted wheat experiments seems broadly applicable also to cane culture :— “Plot ro has received an annual dressing of nitrogen only, in the shape of ammonium salts since the earliest dates of the experiments. It will be evident from the curve showing the crop production that, despite this long-continued use of a manure supplying but one element of plant nutrition, the crop has been wonderfully - maintained. Whereas the average production over the whole period is increased by the supply of minerals to the extent of 1-8 bushels, the nitrogen alone has produced an average increase of 7:6 bushels, the unmanured plot being taken as the standard in each case. The curve, however, shows that the production on this Plot ro is declining, notwithstanding the great reserves of mineral plant food with which the soil started. At the present time also the crop on this plot presents a very unhealthy appearance, is very slow to mature, and is extremely liable to rust. We thus see that it is possible to grow a cereal crop like wheat, year after year, on the same land for at least sixty years without any decline in the produc- tiveness of the soil, provided an appropriate manure be supplied to replace the nitrogen, phosphoric acid and potash removed by the crops. There is no evidence, in fact, that the wheat gives a smaller yield when following a long succession of previous wheat crops than when grown in rotation, although the vigour of the plant does not appear to be so great. The real difficulty in continuous corn growing is to keep the land clean ; certain weeds are favoured by the wheat and tend to accumu- late, so that the land can only be maintained clean by an excessive expenditure in tepeated land hoeing. Notwithstanding all the labour that is put on the plots, the ‘ Black Bent’ grass, Alopecurus agrestis, has from time to time become so trouble- some that special measures have had to be taken to eradicate it and to restore the plots to a reasonable degree of cleanliness.” It does not seem then altogether unreasonable to attribute in part the damage done by fungus and insect pests to the continual growth of cane on the same soil, as in this way the pests have a continuous habitat. In discussing rotations it may not be out of place to refer to the toxic excretion theory: it was originally suggested by De Candolle that plants excreted a toxic substance which prevented the continual growth on the same soil, and in this way explained the benefits of rotation. After definite abandonment this idea has been revived, mainly by Whitney and Cameron, but its discussion lies altogether without the limits of the present textbook. 106 CHAPTER: VI Micro-organisms in Relation to the Soil.—This subject, while only indirectly connected with manuting, may be touched on here in some special connections with the sugar cane. The flora of the soil is made up of bacteria, protozoa, fungi and imoulds. The fertility of the soil is largely controlled by the organic life therein, and it is the first-named class of its inhabitants that have been most studied. Following on Stoklasa,3? soil bacteria in re- t. Bacteria which decompose organic nitrogen and produce ammonia. Bacteria which oxidize ammonia to nitrates. Bacteria which oxidize nitrites to nitrates. Bacteria which reduce nitrates to nitrites and then to ammonia. Bacteria which reduce nitrates to nitrites and eventually to nitrogen. Bacteria which change nitrates, nitrites and ammonia to protein compounds. This type includes members of all groups. 7. Bacteria which fix atmospheric nitrogen. Of these forms those connected with the production of nitrates have been most studied and the elucidation of the problem forms one of the world’s classics of research. Briefly, the formation of nitrates, whence plants mainly obtain their nitrogen, takes place in a number of stages. First of all organic nitrogen is broken down into ammonia salts. The ammonia salts are then converted to nitrites by organisms, of which two types are known, one, Nitrosomonas, peculiar to the Old, and the other, Nitrosococcus, occurring in the New World. Following on the activities of these organisms, the nitrites are converted into nitrates by an organism, Nitrobacter, of which one type only isknown. Conversely, a reverse process takes place whereby the nitrates are reduced to nitrite and finally to gaseous nitrogen. The conditions re- quired for the development of the maximum activity of the nitrifying organisms are :— I. The limits of activity are 5°-55° C, with an optimum of 37° C. 2. Absence of a great excess of organic matter, of alkaline chlorides or carbonates. 3. 1897, 29, 453- W. Ind. Buil., 1904, 2, 6. S. C., 1887, 19, 509. fos pH Ole A} Bx.Sta. Agric. Ser’, Bull- 16: Pee oo PLAY Ex Sta., Agric. ser., Bully 20: 12. Proc. Hawaiian Chemists’ Assoc., 1917. 13. De Cultuur van het Suikerriet op Java. 14. Imp. Dept. of Agric. for the West Indies, Pamphlet 30. 15. Annales Agronomiques, 1879, 5, 283- 16. Java Arch., 1912, 20, 1441. 17. W. Ind. Bull., 1911, 9, 35. 18. Soil Science, 1917, 4, 19. I9. U.S. Dept. of Agric., Bur. of Soils, Bull. 1. Bordo EAs Sta NeriG scr, sbull: 3: 21. Porto Rico Ex. Sta. Circular 12. 22. Jour. Agric. Sc., 1904, I, 87. Sa... bon. x - Sta. Agmc, ser., Bull. 45. 24. Green Manures and Green Manuring. 25. Int. Sug. four., 1919, 21, 53- 26. Jour. Fab. Suc., 1909, 30, 63. 27, Int.-Sug. four.; 1913, 15, 427. 28. Annual Report, Station Agronomique, Mauritius, 1909. 29. H.S.P.A. Ex: Stat, Agric. Ser:, Bull: 24. BO. ees, 18875410 1tO 2: 31. Java Arch., 1893, I, 175. 32. De Cultuur van het Suikerriet op Java. 33. U.S. Dept. of Commerce, Miscellaneous Series, 30. 34. Report, Agricultural and Experimental Work, Dept. of Sc. and Agric., British Guiana, 1908-9. 35. Cyclopedia of American Agriculture, 3, 108. 36. An Account of the Rothamsted Experiments. 37. U.S. Dept. of Agric., Office of Ex. Sta., Bull. 94. OO AVEY DH CHAPTER: YLT THE IRRIGATION OF THE CANE ALTHOUGH the greater part of the sugar cane crop of the world is produced under natural conditions, no inconsiderable proportion is grown under irrigation. The districts where irrigation forms an obligatory feature of cane cultivation are the islands of Oahu, Maui, and Kauai, in the Hawaiian Archipelago, Peru, Egypt, British India, the small area in the south of Spain, and a few plantations in the Black River district of Mauritius. The combined production of these areas now (IgIg) amounts to about 3,500,000 tons of sugar or about 25 per cent. of the world’s production. Partial irrigation is also practised in Java to a considerable extent, but the conditions here are such that crops can be and are grown under natural conditions, and irrigation is a minor rather than a major part of the economy of a planta- tion. Limited areas are also irrigated in Cuba in the Guines district, in Guantanamo, at Nipe Bay and at Constancia (Cienfuegos), and some irrigated cane is produced also in Jamaica, Porto Rico, Formosa’ and Portuguese East Africa. Water used in irrigation is measured in a number of systems :—As a flow per unit of time, or as a depth per unit of area. The British flow unit is the cubic foot-second, or ‘ cusec’ usually referred to the acre. The metric system uses the litre-second referred to the hectare (1 c. ft. = 28-2 litres and 1 hectare = 2-47 acres). The British depth measurement is the acre inch equal to 101-5 long tons, 3,652 c. ft., 22,736 imperial gallons, 27,294 U.S. gallons and 103,130 litres. Hawaiian practice reckons in so many tillion gallons per day. Methods of Irrigation.—Hilgard! distinguishes the following methods :-— 1. Surface sprinkling. 2. Flooding—(a) By lateral overflow from furrows and ditches; (b) by the check system. 3. Furrow irrigation. 4. Lateral seepage from ditches. 5. Basin irrigation. 6. Irrigation from underground pipes. Of these methods, the first, second, third and fourth find application in one or other of the cane-producing areas. These methods are described under the regional headings. Hawatian Islands.2—The privately owned irrigation works in this locality are unparalleled in other districts, and at December 31st, 1914, represented a depreciated investment of $12,818,512, though the actual capital expendi- ture has been very much greater. From actual capital expenditures that have been published may be quoted :— Ewa.—Total cost of pumps delivering 22,000,000 gallons daily, £375,000. Koolau ditch in Maui, 10 miles long and delivering 80,000,000 gallons daily, £91,000. Olokele ditch in Kauai, 13 miles long and delivering 60,000,000 gallons daily, £75,000. 108 THE IRRIGATION OF THE CANE 109 Kohala ditch in Hawaii, 14 miles long, 12 feet wide at top, 74 feet wide at bottom, and 44 feet deep, £83,000. Waiahole ditch in Oahu, 143 miles long, with 10 miles of tunnel, 31 miles of concrete ditch, and 14 miles of steel syphon pipe and delivering 80,000,000 gallons daily, £500,000. Two methods of obtaining water are in use: (1) Pumping from sub- terranean sources, and (2) interruption of upland sources and conveyance to the plantations by systems of canals, tunnels, syphons and flumes. Both of these methods are combined with systems of reservoirs, whereby an excess flow may be conserved, and where often the night flow from the ditches is also stored. The pumping plants are located at or near sea level, and it has been found less expensive to elevate the water through long pipe lines than to sink shafts at a high level and to install mining pattern pumps. In 1909 | I ! I H ut Nan Ditch 8 » ME Mi = am ee ~ ae = te: ——— a =, > =— a L—— a“ —— = —— = Ditch = iS wes eT 2 Levé 2 aS 45> | AN t f I i —— = -— ae -_—- _———— _— Ra = =--—-. — it was estimated that the water pumped daily with an average lift of 200 feet was 595,000,000 gallons, of which 360,000,000 gallons were pumped in the Pearl Harbour district in Oahu, 150,000,000 in Central Maui, and the balance mainly in Kauai. Since then the quantity of water pumped has tended to decrease, following on some extension in the ditch systems leading to the mountain areas, which now (191g) deliver some 800,000,000 gallons daily. These ditches, which are mainly concrete-lined so as to prevent seepage, and which in all aggregate several hundred miles in length, have been constructed with great engineering skill; they have entailed tunnelling through mountains and the passage of deep ravines, the system here generally followed being the use of inverted steel syphon pipes reaching to a diameter of eight feet. The largest reservoir built is that at Wahiawa, on the island of Oahu, with a capacity of 2,750,000,000 gallons, the total capacity of all the reservoirs approaching 10,000,000,000 gallons. The system of applying water used is always one of furrow irrigation, illustrated in Fig. 20 in plan, 110 2 GH APTER Vit and in perspective on Plate XI. The supply ditch is indicated at the left, and from this water is fed to the level ditches, laid out at intervals of 150 to 200 feet, and with a fall of from } to ? per cent. grade. From the level ditches lead the water-courses, laid out at distances varying from 30 to 75 feet, the distance depending on the nature of the soil and on the grade. Paralleling the level ditches and at right angles to the water-courses are the cane rows, from 5 to 6 feet apart, down which the water flows. The furrows in which the cane is planted are laid out with the level, and on their accuracy depends much of the efficiency obtained in the application of the water. On very level land it is pos- sible, and on porous soils advisable, to allow the water delivered from the water-courses to flow both ways in the furrow, thus halving the length of travel. From the time of planting up to about three months before Fic. 21 harvest it is the object of the plantations to irrigate the whole area once every week, though frequently the available supply of water is insufficient. During the three months preceding harvest only enough water is supplied to main- tain the vitality of the cane, and during this time it actually evaporates its own water. Peru.?—In Peru the cane is entirely dependent on irrigation, the melted snow from the Andes being the source of water. The arrangement of the ditches generally followed is shown in Fig. 21. The vegadora, or main canal, leads across the higher part of the field ; from this, by means of a temporary opening, water is brought to the cavesera, and is allowed to flow out and run over the ciutas or beds of five rows. The fields are all on the slope, and the water is seldom pumped back, but is allowed to flow to the fields at a lower level. This method of using the water may be compared with the system of water-courses and furrows at right angles to each other used in Hawaii, whereby a long travel for the water is avoided. Where water is scarce, the system shown in Fig. 22 ; is used, aa being dividing ridges made with the hoe, and which cause the water to run in a zigzag fashion over the field. At the time of planting the fields are | irrigated every five to eight days, water being cut off three months before the harvest. Mauritius.—On the few plantations where irriga- tion is practised a system essentially similar to that described as in use in Hawaii is followed. The water Fie, 22 is obtained entirely from streams and reservoirs, no pumping plants being yet installed. The potentiality of irrigation here is equal to that already obtained in the Hawaiian Islands. Egvpt.s—The source of water is the Nile, and cane is watered as soon as it is planted in February; thence irrigations follow every ten days till the end of August, after which the cane is watered every fifteen or twenty days till the end of October, at which time irrigation is stopped. Demerara.—The method by means of which fields may be irrigated will be readily understood on referring to Figs. 40 and 41; a drain, indicated by the line g, is dug parallel to the cross canal c and connected to it. Down the centres of the beds irrigation drains 15 inches wide and g inches deep THE IRRIGATION OF THE CANE III are dug, along which the water runs into the main drain f and thence to the drainage trench e. In the “ English”’ fields the main drainage trench is dammed at the proper points, and the navigation water is cut into the field, which by these means may be flooded. Although the water available in the rivers is very great, irrigation is very little practised, and its results are often harmful ; the best ever accom- plished is the prevention of the entire loss of crop. The only large-scale irrigation that the writer saw here was in English fields flooded as described above, whereby a system of lateral seepage obtains. Harrison has demon- strated the toxic nature of the subsoil waters in this colony ; such a system would bring these waters to the surface, and herein may lie the cause of the poor results obtained. Java.°—Irrigation in Java is controlled by the Government in the interests of the native land-holders and of the culture of rice; the irrigation of the sugar cane is a matter of secondary importance. During the dry monsoon, usually reckoned to last from June 15th to November 15th, the water avail- able is divided between cane culture and rice culture, the cane planters being allowed the use of the water from 6 a.m. to 3 p.m., and the native rice cultivators receiving it for the rest of the day. During this period it is young cane almost exclusively which is irrigated. In the wet monsoon, which lasts the rest of the year, the water is given to the native cultivator entirely. In cases of prolonged failure of the rains, however, some portion may be allotted to the sugar cane. The cane planter, however, benefits indirectly from the water used in the rice culture, since on taking over the land he has the benefit of the large quantity of water retained by the soil after it has been inundated during the rice crop. A second benefit is obtained from the large amount of silt thus deposited on the land, whereby the use of mineral manures is avoided. Following on De Meijier,® the Solo river carries on an average I kg. of silt per cubic metre, the silt of the Brantas river containing from 0-43 per cent. to 0-60 per cent. of potash, from 0-35 per cent. to 0-65 per cent. of phosphoric acid, and from 0-25 per cent. to 0°27 per cent. of nitrogen. In laying out fields in Java, the main ditches into which water is led from a river or canal are usually 75 metres apart. They are usually about 3 ft. wide at top, 1 ft. at bottom, and 3 ft. deep. The laterals run at right angles to the main ditches and are 10 metres apart, 18 ins. wide at top, 8 ins. at bottom and 16 ins. deep. The cane rows run parallel to the main ditches, and are usually 5 ft. centre to centre. From the laterals water is thrown on the stools of cane by hand from buckets or long-handled dippers, and less frequently the water is caused to back up in the laterals and then to flow down the rows, or again, after the laterals are filled, water may be allowed to reach the roots by means of seepage. At planting the cane is irrigated every three or four days fora month. In the second month an irrigation is given every five to six days, every ten days in the third month, and every fifteen days for the next two or three months, when irrigation stops, and drains are laid out across the fields. British India.7—Irrigation is general wherever the cane is grown in India. The land is usually watered before planting, after which irrigations follow at first every five days and afterwards every eight days. The water is ob- tained from wells or from the State-controlled schemes. The system used II2 CHAPTER VII is one of furrow irrigation, differing in method in no way from those already described. Quantity of Water used in Irrigation.—In experiments made in Java, Van der Heide® concluded that 0-360 litre per second per bouw, or 0:0072 cubic foot per acre per second was required for cane irrigation. This quan- tity is equivalent to a flow of 560,000 gallons per day per 100 acres, or to 62 inches per year, but, as irrigation only obtains from April to November, the actual quantity of water used is about 36 inches. For an actual irrigation at planting in Java, Mussenbroek® estimates that 524 cubic metres are required for a bouw, and for a watering afterwards 105 cubic metres. These quantities are equivalent to 10,570 and 214 c. ft. per acre, or to 2-9 and 0-6 inches respectively. As compared with these quantities, O’Shaughnessy® gives 1,000,000 U.S. gallons per day as required for the complete irrigation of I0o acres in Hawaii. This quantity is equivalent to 134 inches, and does not include the 50 inches of rain that may be expected to fall in a season of eighteen months during which the cane will receive 22,800 tons of water and will produce from 50 to 80 tons of cane. Of this quantity O’Shaughnessy estimates that only one-third reaches the area of the cane roots, due to leaky reservoirs, ditches, and careless application, but since this estimate was made much more careful conservation is practised. In Egypt, Tiemann? estimates that for each irrigation 1,000 cubic metres are required for a hectare, equivalent to 14,300 c. ft. per acre, or to 3-6 inches. At Poona, in British India, Mollison!® estimates that the cane over a crop season receives 75 to 80 inches of water in twenty-eight applications, together with some 30 inches of rain. The data fo lowing are based on a report by Maxwell" dealing with experimental work on the irrigation of the cane in Hawaii. During a period of growth of about 17 months the total water supplied to the crop averages about 100 inches. Reference to the table below will show that the young cane received less water than when more mature, but not so much less as might be thought proportionate considering the different states of young and of mature cane. The causes at work are twofold: when the cane is young the whole ground is exposed to the direct rays of the sun and to the action of winds ; when the cane is older the foliage shades the ground and lessens loss due to evaporation, and to a large extent conserves water in the soil. At twelve months of age the crop actually consumes in its economy ten times as much water as a crop one month old, but owing to the causes mentioned above the apparent consumption is much less dis- proportionate. It was found by experiment in Hawaii that the best results were obtained when the young cane received 0-5 inch per week; less favourable results were obtained when the water supplied was one inch per week, and when the furrows were filled with water the cane came up yellow and sickly. As the cane comes away it requires about one inch weekly up to three or four months, after which 1-5 inches are necessary until the crop is in full vigour, when three inches and never more are required. These figures refer to natural and artificial supplies combined. The reports quoted above give as a general figure that 1,000 lbs. of water are required per lb. of sugar produced, and mention that certain plantations in Hawaii use much more water than the quantities cited with less favourable results. PLATE JAE ‘TIVMVE, NI GaaS ANVD AVOAS ONILVOINN] tity ~ ‘ J THE IRRIGATION OF THE CANE 113 TABLE GIVING WATER USED IN PRODUCTION OF A CANE Crop. Monthly Irrigation Water Period of Application. Rainfall. Monthly. inches. inches. July 0°94 Se 4°0 August 1°58 = 4°0 September 0:88 4°0 October I*75 3°0 November T° 32 3:0 December. . 1-86 2°0 January I-00 4°0 February .. 3°75 I°5 March 3°98 3°0 April 0-85 4°0 May 2°01 4°0 June o- 88 7:0 July 0:17 7°0 August I-90 9°0 September 0°75 8-0 October 2°92 6:0 November 0°47 3°0 27°O1 76:5 The consumption of water per lb. of sugar produced was :— Crop. Water per acre. Sugar per acre. Water per Ib. lbs. lbs. of sugar. 1897-98 -2 25,333,000 Sc 24,725 <2 1023 1898-99 <5 27,885,900 Be 29,059 or 959 Water transpired by Cane.—Maxwell" found as the result of experiment that, when cane was grown in tubs, in seven months 79,310 grms., or 174°5 Ibs. of water, were transpired by the plant, there being formed 568-9 grms. of water-free material, consisting of 31-8 grms roots, 53-9 grms. stems, and 483-2 grms. leaves, or 147:8 lbs. water per lb. of water-free plant material. The amount of water transpired in each month of growth was found to be as in the annexed table :— Age of Age ot Time of Cane. Transpiration. Time of Cane. Transpiration. Observation. Months. Grms. Observation. Months. Grms. May aie ti = 860 August .. 4 -. 19,800 June 2 6,500 | September 5 .. 20,050 July Se TD he, GET LOOO October .. 6 ~19.215kOO Experiments due to Kammerling!” in Java showed that on an average one stalk of cane by its leaves transpired over its whole period of growth 250 c.c. per day; this he estimates as equal to 3,500,000 litres per bouw over the whole vegetative period, or equal to about 1,600 tons per acre. During the first month of drought in Java, Kammerling estimates the transpiration per stalk as 500 c.c. per day, and using this as a basis he reckons that the replacing of the soil water thus transpired in a month requires 720,000 litres per bouw, or about 330 tons per acre. Kammerling also observed that the transpiration of the Manila, Cheribon and Muntok canes was as 5: 4: 3; ie., the latter will remain in vegetative vigour on the soil water longer than the former, and will be drought-resisting. Optimum Quantity of Water in Soil——Water exists in soils in three conditions: as hygroscopic water, as capillary water, and as gravitational I II4 CHAPTER VII water, that is to say as water in excess of that which can be absorbed by capillarity. Hygroscopic water is not usually available for plant use, and gravitational water is injurious to all except a few specialized plants. Generally normal vegetative growth occurs between the limits where the hygroscopic water ends and the gravitational water begins, that is to say when a soil contains only hygroscopical water and a little capillary water the plant will wilt, and when gravitational water is present normal growth is checked. Experiment has shown that usually plants will make, their maximum growth when the maximum quantity of water is present that can be absorbed by capillary attraction. The actual percentage of water in a soil corresponding to this condition varies within wide limits; thus in sandy soils the hygroscopic water is about 2 per cent., rising to Io per cent. in clays, and to 40 per cent. in peats; the actual water content for the best results will be least in sandy and most in peaty soils. This feature of irriga- tion has been studied to some extent by Eckart!® and more recently by Burgess.14 The latter calls attention to the very hygroscopic nature of Hawaiian soils due to the presence in large amounts of colloidal silica, ferric oxide, alumina and humus, and he estimates that soils such as these are in the optimum condition when they contain about 45 per cent. of water. Eckart, experimenting on the soils of the Experiment Station in Honolulu, found that the best results were obtained with an irrigation of three inches per week, the soil then containing on an average 31-38 per cent. of water. As this soil could absorb 40-74 per cent. of water, the optimum percentage would occur when it was saturated to 77 per cent. of its capacity, a figure higher than is found with most crops. Quality of Irrigation Water—Maxwell™ arbitrarily fixed the “ danger point ”’ of irrigation water at 100 grains of salt per imperial gallon ; Hilgard!® states that 40 grains is the usual limit. Eckart!® found cane in lysimeters grew unchecked when the soil water contained 195 grains chlorine, as sodium chloride, per U.S. gallon, and obtained in lysimeters a normal growth when irrigation water containing 200 grains of salt per gallon was used in ex- cess, at the same time permitting good drainage from the porous soil em- ployed in the tests. He also found that gypsum and coral sand mitigated the harmful effect of saline irrigation waters.1” The nature of the salt in the water has a profound effect ; sulphates or carbonates of lime and magnesia are not harmful; it is in the chlorides of the alkalis that danger lies. The danger of such water lies in their abuse rather than in their use ; if the soils to which they are applied are ill-drained so that the salt can accumulate, the quantity soon becomes toxic ; combined with natural rainfall, applications of a purer supply or heavy applications of the saline water, together with good drainage so as to wash out the accumulated salt, permit their safe use. Conservation of Soil Water—After the water has arrived in the soil a great part is always lost by evaporation, and this is capable of control within certain limits. A protective layer of soil in fine tilth prevents the upward movement of the water by capillary attraction to the surface, and is highly efficient in retaining water in the soil. Not less important is the nature of soil; soils containing much humus are especially water-retentive, and this is capable of control by burying the trash of the cane and by ploughing in green manure; to a certain extent the benefits of these THE IRRIGATION OF THE CANE 115 practices may be attributed to the increased water-holding capacity of soils treated in this way. The velocity and flow of the wind are also of importance in determining the evaporation from the soil, and loss in this way may be controlled by planting wind-breaks or belts of trees. Another factor of very great importance is the humidity; Eckart4 has shown that this entirely masks the effect of temperature, so much so that a rise in humidity of 12-5 per cent. decreased the evaporation 50 per cent., although the temperature rose 1:5° Fahrenheit. Cost of Irrigation.—The cost of irrigation as practised in the Hawaiian Islands is very great, and at the same time very variable with varying local conditions. The cost divides itself naturally into two parts, the cost of furnishing water and the cost of applying it to the field. On those plantations which have irrigation schemes tapping upland supplies the level of the field does not affect the cost, but where the water is pumped the cost rises pro- portionately to the height to which the water has to be elevated. The cost of lifting 1,000,000 U.S. gallons one foot is roughly 0°09 cent, with fuel oil costing 0-8 cent per lb., included herein being interest, depreciation and labour. This amounts to $24-56 for 100 acre-inches lifted to a height of 100 feet. The cost of water from ditch systems is considerably less; one ditch company there supplies water at the rate of $2,500 per year per I,000,000 gallons per day, a figure amounting to $18-79 per I00 acre-inches. A very similar figure is charged in Porto Rico by a Government-owned scheme supplying water in the southern portion of the territory. Here the cost is $2:50 to $3-00 per acre-foot, or $20-82 to $25-00 per 100 acre-inches. The actual recorded costs of irrigation in the Hawaiian Islands for the year I9gI4 are given below.1® These data refer to plantations entirely dependent on irrigation, each field receiving water on an average probably never less than once in every ten days. The variations in cost are due to differences in level, and to the difference between pumping and gravity supplies. IRRIGATION CosT PER ACRE AND PER TON OF CANE, CROP OF IQI4. Planta- Cost Cost per | Per cent. Items. tions per ton | labour included. acre. ofcane. | of total $ | cost. Pump expense ors | 12 2t-31 00-3984 =| 20+ 62 Pump repairs oe 3h) Io 2:81 00529} 49° OL Pipe-line expense af a5) 13 0+ 36 0+ 0075 57°40 Reservoir expense... ae 16 0*50 O: 0104 68-94 Irrigation-flume expense | 12 0°51 0+ 0090 46°65 Ditch expense 2 .| -I4 6:2 0° 1317... -| 64°74 Water purchased | 16 7°89 o-1706— | O° 33 Irrigating ae sic aes, 24 40°Ir ! 0-8388 87:78 Average (24 plantations) 24 67°91 I+ 4198 62°97 I16 CHAPTER VII Cost oF IRRIGATION PER ACRE, PER TON OF CANE, AND PER TON OF SUGAR, AND PRODUCTION PER ACRE, BY PLANTATIONS. Cost of Irrigation. Production per acre. Plantation. 4 Per Per ton Per ton Tons of | Tons of acre. of cane. | of sugar. cane. sugar. $ $ No. I 22°44 0-49 4°16 45:6 5°4 No. 2 ‘ 99:89 Wey II°75 58-2 85 No. 3 69°83 I°35 IO-Oo1 51°7 6:9 No. 4 34°13 0°57 Some 59°4 | 6°7 No. 5 63°77 Tci2 2a Q: II 52°2 7°0 No. 6 46:06 0-99 | 8-14 49°8 6:0 No. 7 100: 28 Rb Ae kas 602356.) . some No. 8 26°23 Opslaan 7°O1 2078 - || eaaea No. 9 74°28 1°55 | 10°94 48-1 |. 6:8 No. 10 I13°15 2°18 14°90 51°9 7°5 No. 11 71°37 LS eg PA | IR ACh 48-6 5°6 No. 12 86°85 TRO See oes MS niger 64°2 7°4 No. 13 : 85°27 L-30 II* 32 65:8 7°5 No. 14 30 88-65 2°03 15°28 AS Fit | wna Average 7O*15 £33 10+ 32 52°3 6:6 REFERENCES IN CHAPTER VII I. ‘*Soils,’? New York, 1906. 2. U.S. Dept. of Commerce, Miscellaneous Series, 53. 3. From a copy of an unpublished report. 4. Int. Sug. Jour., 1903, 5, 64. 5. De Cultuur van het Suikerriet op Java. 6. Trans. Am. Soc. Civ. Eng., 19095, 54C, 40. 7. Dictionary of the Commercial Products of India. 8. Java Arch., 1894, 2, 833. 9. Trans. Am. Soc. Civ. Eng., 1905, 54C, 129. 10. Agricultural Ledger, 1808, 8. 11. U.S. Dept..of Agric., Office of Ex. Sta., Bull. go. 12. Proceedings, Fourth Congress, United Syndicate of Java Sugar Manufacturers, 1904. £3) Sve Ae Exwotd AGC. Set. poull no: 14. H.S:P.A., Ex.Sta., Agric» Ser.; Bull. 48. eee or SOllsse 16. H.S.P.A. Ex. Sta. Agric. Ser., Bull. 8. T7e. HS PAG, se eota eA SIC mOcr wut. 18. U.S. Dept. of Commerce, Miscellaneous Series, 53. PLATE XI. FOWLER STEAM PLOUGH OUTFIT. Ox PLOUGH AT WoRK IN CUBA. Puare ’ eth ‘NVINOQOAT NI HHO LY SYOLOVUT YOLOJY NOSANOS CHAPTER «VIET THE HUSBANDRY OF THE CANE THE cane is grown under so many diverse conditions that no general sketch of its husbandry is possible. An attempt is made in this chapter to give some short notice of the implements employed and the routine of operation in the more im- portant districts. Broadly speaking, the dis- tricts where the cane forms a staple fall into two classes: those where the cultivation is chiefly manual, and those where animal or power-operated implements are used. The former methods are mainly employed in the presence of a cheap supply of labour of Asiatic or African origin, but the physical conditions of the district have also a large influence. The manual implements used in the cultivation of the cane are the hoe, the fork, the shovel, and the cutlass. The cutlass, two forms of which are shown in Fig. 23, is used in the British West Indies as a weeding tool. In other districts this work is done with the hoe, two forms of which are shown in Fig. 24; the short-handled hoe is used in Mauritius, and the long-handled form in Demerara. Besides being used to cut dewn weeds, it is employed to hoe earth over the rows of cane and to make the cane furrow, while in Mauritius it is also employed in making the holes in which the cane is 2 planted. The native Javanese hoe or patjol Fic. 23 is a short-handled tool with long and narrow blade, intermediate between a pick and a hoe. The fork, Fig. 25, is employed in Demerara in the cultivation of the cane when forking banks, i.e., turning over with the fork the soil between the rows of cane. The shovel, Fig. 26, is used in Demerara in preparing the seed bed, and in digging drains. With few exceptions the same implements that are employed in the hus- bandry of other plants find use with the cane; these include steam, gang ploughs, turn or mould-board, shovel, and disc ploughs, harrows, tongue and disc cultivators. In this connection it is of interest to note that so long ago as 1848 Wray in the “ Practical Sugar Planter ’’ advocated the use of steam ploughs and of cultivators ; he illustrated a turn plough operated by 117 118 CHAPTER VIII one engine on the cable and anchor system ; the horse hoes and cultivators that he showed (and the use of which he strongly advocated) differed but in detail from those in use at the present time. His remarks on the use of these instruments are as true to-day as they were three generations back, and are therefore quoted below :— “The hoe plough is the next instrument particularly deserving of attention ; it is one of the most useful that the planter can em- ploy. This plough is used for the purpose of hoeing up weeds and loosening the earth between the growing plants. It is provided with two wheels, one in front of, and one behind the hoes, by means ot which the depth of the hoeing is regulated. It may be used with three triangular hoes, each cutting 134 inches wide, extending over 3 feet 6 inches of ground, or con- tracted toa smaller width ; or the two hind hoes may be replaced by two curved knives for cutting the weeds up on the sides of the ridges. Itisanimplement of very Fic. 24 Fic. 25 Fic. 26 simple construction and in great use in England ; itis also one that will be found of very great advantage on sugarestates, in cleaning between the cane rows, and in loosening the soil about the plants. The expanding horse hoe is an imple- ment designed and manufactured expressly for the colonies, and is already beginning to establish for itself a very sure reputation amongst sugar planters. By means of a very simple contrivance, it can be extended and contracted at pleasure ; so that the planter can have it made to expand even to 54 or 6 feet, if he requires it, as he will in all cases where he plants his canes at six feet apart ; whilst at the same time, by having spare tines or shares of peculiar form, he can vary the nature of the work to be performed by it. For instance, the instrument is suited for rooting up weeds and loosening the soil between the rows of canes ; by taking off the tines and hoes and replacing them with light moulding shares, the instrument is at once converted into a mou!ding machine, whereby the young canes may receive two of three successive mouldings as lightly and neatly as by hand labour. I consider this machine to be so valuable to the planter that no sugar estate should be unpro- vided with it; it enables him to perform at a very inconsiderable cost an amount of work which, when executed by hand labour, is well known to be very tiresome and expensive.” Systems of Mechanical Tillage.——In mechanical tillage two distinct sys- tems are in use. In one, invented by John Fowler, in the first half of the nineteenth century, the implement employed is drawn across the field by means of acable. Usually two engines located on opposite sides of the field are used; on each engine is a winding drum, which alternately pays out or winds in cable, thus drawing the implement across the field. With this system balanced ploughs with a double gang of shares are used, one set being tilted in the air while the other is buried in the ground. This system, which is illustrated in Plate XII, has been, and continues to.be, very largely used in the Hawaiian Islands, in Peru, and to a less extent in Cuba. In the second system, the implement is hitched behind the tractor and drawn across the field. Steam tractors have been used for this work, but the system has only become extensively used with the development of the gasoline or petrol tractor. Two types of tractors are found, the wheel THE HUSBANDRY OF THE CANE 11g tractor and the caterpillar or track-laying tractor. An illustration of the former type is shown on Plate XIII. At the other extreme is to be found the animal-drawn implement still in general use in Cuba, Java, and the Philippines, and in other localities occasionally where peculiarities of certain fields may prohibit the use of the more economical power plants. Plate XII shows a yoke of oxen at work in Cuba in the preparation of land for planting BiG? 2 The area of land ploughed by these devices in a given time varies both with the nature of the soil and with the depth ploughed. Cable-drawn steam ploughs operated at a depth of 14-16 inches will, in lands of normal stiffness, take one hour to plough an acre, the area increasing as the depth decreases. The motor-drawn paraffin tractors, ploughing only to a depth of 4-6 inches, will, under similar conditions, plough an acre an hour. At the other extreme is the ox-drawn Cuban plough which has a capacity of only one acre in nine hours ploughed to a depth of not more than four inches. The Implements used.—Generally the implements used in cane culture differ in no ways from those employed in other agricultural industries. Some of these, together with types specialized for use with the sugar cane, are described below. Ploughs.—The primitive type of plough which has come down from very early times still survives in use in Java, in the Philippines, and in Cuba, in all of which countries, however, it is fast disappearing. 120 CHAPTER VIII Turn, or Mould-Board Ploughs—Turn, or mould-board ploughs are so called because they cut from the soil a clean slice and turn it over top side down, through the action of the mould-board; the single mould-board plough is shown in Fig. 27; a is the share, b the landslide, c the coulter, and d the mould-board or breast. The coulter shown is of the knife type ; it may be replaced by a rolling coulter, consisting of a revolving steel disc, and, instead of being hung from the beam it may be bolted on to the share or may be entirely absent. This type of plough is the instrument that is almost always used in the preparation of land for planting crops of any kind Fic. 30 the plough may be a single unit, or there may be a number of units forming a gang plough. The double mould-board plough is shown in Fig. 28, the lettering being as for the single mould-board plough. This plough throws a slice of earth on either side of the share, and finds an extended use in the THE HUSBANDRY OF THE CANE 121 sugar industry in forming the furrows in which the cane is planted, in opening irrigation channels, in “ bursting out ”’ the middle of the cane rows, and in turning over weeds between the rows in young canes. Disc Ploughs——The essential part of the disc plough (Fig. 29) is the revolving discs ; these are of concave shape and revolve about their centre, the slice of soil being turned over by the action of the concavity of the disc. Fic. 32 The disc principle was originally devised to lessen the draft on the plough, and these ploughs find use in tenacious soils, where the mould-board plough will not scour properly, and in very hard lands where it is not possible to 122 CHAPTER VIII use the latter plough. In open loose soils the disc ploughs are inferior to the other type. By the use of two discs inclined towards each other, they may be used for furrowing, and they also find one of their most extended uses in turning over and burying the pea vines grown as a green manure. » Knife Plough.—Fig. 30 shows an implement used to some extent in the Hawaiian Islands as a substitute for the ordinary turn plough. It is used in connection with steam tackles in preparing the land for planting, and does not turn over the soil or make a furrow. Its action is to break up and loosen the soil to a depth of about two feet. The Cultivator —The cultivator, which has developed from the shovel plough or horse hoe, is shown in Fig. 31. Incane fields this instrument is drawn by animal power between the rows of cane, breaking up the soil and destroying the weeds. The disc cultivator is shown in Fig. 32. It is built to straddle the row, the discs being set to throw dirt on the row. These instruments can only be used on young cane, and when the crop is too far advanced to permit their use it is said to be laid by. Fic. 33 The Harrow.—This implement, a form of which is shown in Fig. 33, is used after ploughing and before making the furrow to break up the clods of earth. The action of the harrow may be supplemented by the use of rollers. The principle of the disc has also been applied to the harrow, and a form of disc harrow is shown on Plate XIV. This appliance is used in the Hawaiian Islands to cut up cane trash and green manures before turning them under with the plough. Special Cane Implements.—In Figs. 34, 35 and 36 is shown the Benicia- Horner No. r Ratoon and Cane Disc plough, which has found an extended use in the Hawaiian Islands. It contains in detachable parts a double mould-board plough, a revolving knife, right and left-hand discs, and a sub- soil plough ; it may be used as a furrower, either for planting or for irrigation, for bursting out middles, as a cultivator for throwing soil on to the cane row or with the object of hilling up the latter, for trimming and subsoiling the sides of the cane row, and slicing and cutting the ratoon row. When used as a furrower (Fig. 36) for planting or irrigation, the imple- ment is equipped with both right and left-hand discs, with the double mould plough and with the subsoiler; when used to slice up ratoon cane (Fig. 35) the plough is replaced by a revolving knife ; when used for THE HUSBANDRY OF THE CANE 123 hilling up rows of cane (Fig. 34) the revolving knives and discs alone are used, the subsoiler being detached. In Fig. 37 is shown the Horner combined weeder, cultivator and harrow, intended to be used where the growth of grass is very rank. It was originally designed to be used with the hona-hona (Commelina nudiflora) grass of the Hawaiian Islands ; the semicircular teeth tear up the weeds and at the same time cultivate the soil. The load of weeds gathered in the cradle can be discharged by lifting up the handles of the implement. Spaulding Deep-tilling Plough—tThis implement (Plate XIV) is used to an increasing extent in the Hawaiian Islands in turning under cane trash. In operation the front disc takes off a slice of soil, turning it into the bottom of the previous furrow. The second disc operating about four inches inside the track of the other on a space cleared of cane stumps and grass by the first disc has no difficulty in effectively turning over and burying a slice of the soil along with the cane trash. Stubble Digger —This implement, Fig. 38, is mainly confined to Louisiana: It consists of a rotary shaft, on which are fitted blades arranged about a helix. When the carriage is drawn along the rows of ratoon cane, the knives revolve and break up and pulverize the soil. Stubble Shaver.—This instrument, Fig. 39, the use of which is also con- fined to Louisiana, is used to cut down cane stumps flush with the ground. Its essential mechanism is a horizontal circular knife, which rotates as the carriage is drawn along. _ 124 CHAPTER VIII Preparation of the Land.—Although the greater part of the cane sugar yearly produced is manufactured from cane grown on land that has been in cultivation for a number of years, and in many sugar-producing countries all available land is under cultivation, in some other countries virgin land is EE Fic. 35 still taken in, or old abandoned land that has fallowed for a number of years and returned to its primitive condition is again put under cultivation. In general, the operations to be undertaken in putting in new land may be briefly described as under :—The land is cleared of all trees and bush, the Fic. 36 heavy wood is put on one side to be used as fuel, or, if valuable, for export, the small branches, leaves and bushes being burnt im situ. Very generally all this work is done by hand, and the cost, espécially if heavy stones (as is often the case in volcanic countries) have to be moved, is very great. The more modern and economical method is to employ steam power; engines capable of use either as traction or stationary units are employed in many PLATE XIV. Disc HARROW SPAULDING DrFre TILILING PLOUGH. PLATE * AV. ‘ONIINVIg wOd AGVAN ATA ANVD VAV[ VY THE HUSBANDRY OF THE CANE 125 countries for the purpose of hauling the heavy timber and large stones off the land ; when new districts are opened up or when new land is continually taken in, such a process is almost essential. The combustion of the vegetation on new land is from one point of view entirely wrong, for the practice robs the soil of most of the nitrogen that has been accumulating for ages past ; but the expense of burying the vegetable matter, the slowness of its decomposition, and the harbouring places it affords for noxious insects are the reasons brought forward for maintaining this 126 CHAPTER. VIII practice ; in addition, the burning of the vegetable matter places in the soil a large amount of readily available mineral plant food. After the land has been cleared in those countries which employ land carriage, roads wide enough for carts to pass are made through the new sections, and the area divided up into convenient fields ; the land is prepared for cultivation by ploughing, either by manual, animal or steam power. When hand labour is employed, the soil is merely turned over by forks or shovels ; in other cases the whole area is ploughed, cross-ploughed and horse- hoed, and the soil properly broken up and aerated. British Guiana.—In British Guiana and the Straits Settlements, which are flat alluvial countries, a somewhat more complicated procedure is necessary. The area of the new plantation being decided, three dams formed by the excavation of three trenches are thrown * up; these dams are known as the navigation or middle walk, sideline or drainage, and back dams; and they enclose the piece of land which is to be put into cultivation. More frequently, however, a double section is formed with two sideline dams and a Fic. 39 back dam as empoldering dams, a navigation dam running in the centre of the two half-sections, and serving equally for both. In Figs. 40 and 41 are given plans of the arrangements of field customary in British Guiana; ais the navigation dam formed by the excavation of the navigation trench b; the navigation trench continues up to the factory, and is used for the transport of cane and produce, and also to supply water for irrigation and other purposes. This canal is connected with a river, creek or lake ; or, where this is impossible, a large canal capable of supplying a batch of estates carries water from a river. Many estates have pumping stations situated on a river, so that they are nearly independent of drought; on other estates a drought may cause the level of water in the river or creek to fall so much that it is necessary to take sea water into the trenches. At e are shown cross canals communicat- ing with the navigation trench, and terminating about 20 to 25 feet from the sideline or drainage canal c; the cross canals are used for the purpose of bringing the punts or barges used for transport within access of the canes ; the main drainage canal runs out to the sea or river. Drainage is either forced or natural ; in the former case centrifugal or sluice wheel pumps are employed, the first-named being by far the most economical ; in the latter THE HUSBANDRY OF THE CANE 127 case the sideline discharges at low tide into the sea or river. Between the cross canals lie the fields, usually of area Io to 20 acres, the distance from cross canal to cross canal being about 500 feet. In Demerara two kinds of fields are distinguished: Dutch fields, Fig. 40, and English fields, Fug. 41. In the Dutch form the fields are divided into beds 35 feet wide, running parallel to the navigation trench ; running down the centre of each field is the drain f Fic. 41 known as a tracker or four-foot, which communicates with the main drainage trench ; between each bed are small drains i, which discharge into the four-foot. In the English fields the beds d run at right angles to the naviga- tion trench. There is usually one bed g, called the dam bed, running parallel. In front of the dam bed is a cross tracker #, and between the beds are the small drainsi. Through the centre of the field runs, as before, the four-foot f. The drainsi discharge both into the cross tracker, and thence by f into the main drainage trench, and also directly into the main drainage trench ; 128 CHAPTER VIII very often a centre cross tracker is also provided. The dam, called the back dam, is not shown in the sketches. It is the last dam on the estate, and serves to keep out savannah water. Approximate dimensions customary in Demerara are :—Navigation trench: 16 feet to 20 feet top; 12 feet to 16 feet bottom; 4 feet to 5 feet deep. Cross canals: 12 feet top, 9 feet bottom, 4 feet to 5 feet deep. Small drains: 2 feet to 3 feet top; 14 feet to 2 feet bottom ; 3 feet deep. Larger drains (trackers): 5 feet top, 3 feet bottom, 4 feet deep. No furrow is formed in the soil, but a seed bed three to four feet wide is made with the shovel, into which the seed cane is pushed in a sloping direction. Between the cane rows is a space about four feet wide called the bank ; often on very stiff clayey soils a shallow drain known as a drill, running parallel with the cane row, is made in this bank. Louisiana.—1n Louisiana, where the sugar lands are flat and alluvial, little, if any, new land is now taken in for sugar-raising purposes. The pre- paration of the old land is as follows. The soil generally bears a plant and ratoon crop of cane followed by corn ; at the last cultivation of the corn the land is sown with cow peas at the rate of from one to three bushels per acre ; an immense mass of vegetation is produced which is ploughed in with disc ploughs asa green manure. When the vines have rotted sufficiently, the ridges on which the cane is to be planted are formed with the turn plough ; drains are made at right angles to the ridges, these quarter drains leading into larger ditches, and these latter into the main drainage canals. Cuba.—The sugar lands of Cuba are divided into the older lands of the western half, which have been in cultivation for many years, and the newer lands of the eastern half, where quite recently plantations have been carved out of the virgin forest. In putting new land into cultivation, the larger trees are cut down, hauled off the land and sold for timber if a market can be found. The stumps are left im situ. After a dry spell fire is set to the undergrowth and the land thus cleared. No ploughing is at- tempted, and indeed this would be quite impossible until the tree stumps have rotted away. Cane is planted without any preparation of the soil, holes being formed in the ground with a pick or crowbar. No attempt is made to line out the rows, and the tops are planted as the stumps of the trees best allow. Such land will often afford as many as twenty cuttings from one planting, after which the tree stumps are sufficiently rotted to allow of ploughing and of the ordinary agricultural processes. _On the older lands the ground is ploughed after the last crop of ratoons have been taken off, and the cane is planted in furrows in the usual way. The ox-drawn plough is being fast superseded by power-drawn implements. Hawait—Deep and thorough ploughing and good preparation of the soil is a characteristic of this district. A typical routine is as follows :—After the land has carried its last ratoon crop, a plough is run down the middle of the row bursting out and shattering the ratoon rootstocks ; the land is then harrowed, ploughed and, perhaps, cross-ploughed. Where the contour of the land permits, steam ploughs, generally Fowler cable-operated balanced ploughs, as shown on Plate XII are used; after ploughing, a second harrowing is done, following on which the furrows, and water-courses on irrigated plan- tations, are made with a double mould-board plough. Fertilizer may then be scattered on the bottom of the furrow and mixed with a subsoil tine THE HUSBANDRY OF THE CANE 129 cultivator ; usually the application of fertilizer is delayed until after plant- ing. Plate XI (page 112) shows a Hawaiian cane field ready for planting. Mauritius —For very many years past no new land has been available for cane growing in Mauritius; an essential feature of the system of cane growing there followed is the well-advised green manuring given the land after the last (generally third) ratoon crop has been taken off. After the land has been for a variable period under the green crop, this is cut down and buried or burnt off ; after lining off the field the holes in which the cane is planted are made with the hoe. The entire preparation of the land is done with very cheap manual labour of East Indian origin. Java.—tThe imperative needs of the large native population of Java demand a carefully regulated system of land tenure, and the self-contained plantations found elsewhere are absent from Java. Cane is only planted one year in every three, the land at other times being in the hands of native cultivators ; cane generally follows rice, and a number of small separated areas of rice are united into one cane field, the area of which is from one bouw (I-97 acres) to 100 bouws, with an average of from Io to 20 bouws. The first operation is to level the small embankments that have been made in the rice fields, and to separate the terraces and fields belonging to different owners. The rest of the operations are thus described by Prinsen Geerligst : “‘ As soon as the rice is reaped, and sometimes during that operation, a deep ditch is dug round the field in order to drain off superfluous water. Owing to the wet rice cultivation the soil has been saturated with water during the previous two or three months, all kinds of reduction processes have taken place and oxygen fails entirely. In order then to render the land fit for cultivation the soil must be exposed to the action of sun and wind. To this end the field is divided by trans- verse ditches into plots of one-quarter or one-fifth of an acre, and between these ditches the rows in which the cane is to be planted afterwards are dug. Ordinarily these rows are 30 feet long, 1 foot wide, a little over 1 foot deep, and 4 or 5 feet apart. The excavated soil is heaped up between the rows. In some places where the nature of the soil so allows, the land is ploughed first and afterwards the rows are dug with the native spade. When the field is thus prepared it has the aspect of a large number of trenches, which remain exposed to the sun’s rays for about six weeks. It is still unknown what chemical action takes place during the drying of the soil, but experience has taught us that this period of lying fallow is indispensable in obtaining a good crop. The wet lumps of soil dry up during this operation, crumble to pieces and assume a lighter colour, causing the mass of moist cold hard lumps to change into a loose greyish powdery soil. During the weathering all grass is carefully weeded out, and this is continued after planting until the cane has grown so high that it keeps down the weeds by its own shadow. At the end of the drying time the soil in the rows is loosened a little and the cane tops are then planted in them.” A ground plan of a Java cane field will then appear as in Fig. 42; at a is a ditch surrounding the field, into which drain the cross ditches, which are in turn fed by the small drains c separating the cane beds ¢; the cane rows are at 5 running across the beds. Plate XV (page 125) shows a Javanese field ready for planting. In the literature of the cane as it relates to Java reference is often made to the Rey- noso system. Reynoso was an eminent Cuban agronomist, who published in 1865 a treatise on the agriculture of the sugar 130 CHAPTER VIII cane. This work was translated into Dutch and attracted much attention in Java. Reynoso advocated deep cultivation, thorough tillage, and planting in furrows, as opposed to pushing the cane top in a slanting direction into a level field. The system of deep trenches described above is directly due to Reynoso’s influence, and is known in Java as the “‘ Reynoso system,” as opposed to the “‘ plough system,” in which the land is ploughed to a depth of about six inches with the native plough. Reynoso, however, nowhere writes of planting in deep trenches, and what is now indicated in Java as the “‘ Reynoso system ” goes much further than anything advocated by the learned Cuban agriculturist. Planting.—The seed cane is usually planted in furrows, made either with the double mould-board plough or with the hoe. These are spaced from four to six feet from centre to centre, and are about two feet deep from top of ridge to bottom of furrow. In Java, as explained above, a deep trench generally takes the place of the furrow, and in Cuba in forest-cleared land no furrow or seed bed is attempted. Usually the cane top is planted at the bottom of the furrow, but in clayey or badly drained soil it may be placed on the top of the ridge, the furrow then acting asadrain. In Demerara no furrow is formed, but the cane is planted in a seed bed formed with the shovel in the centre of the row. In many districts the old method of planting in holes still obtains and is mainly followed in Barbados, Mauritius, and Réunion. Hole planting is also sometimes used in connection with the deep trenches used in Java. The holes are from 15 to 18 inches long and from 8 to 12 inches deep. It is customary to count 3,000 of such holes to an acre. Amount of Seed Cane required per Acre.—This is, of course, dependent on the number of rows per acre, and whether the seed cane is planted in single or in double lines in the row. In an acre with rows five, six or seven feet from centre to centre, the length of the rows is approximately 8,740, 7,280 and 6,270 feet; taking the cane as weighing eight ounces to the running foot, there will be required 4,370, 3,640 and 3,135 Ibs. of cane respectively if the latter is laid in single rows. Width of Row.—In general it is the fertility of the soil that determines the most economical width of row ; in very fertile soil, the rows are placed comparatively far apart to allow freedom of growth to the luxuriant crop, and, conversely, as the soil becomes less productive a narrow row gives more economical results. In practice the cane rows are from 3 to 7 feet wide ; “in Cuba, according to Reynoso, the standard width is 1-70 metre (5 ft. 6 in.), the rows being the same distance apart. Boname gives the average width of the cane row in Guadeloupe as I-30 to I-50 metre (4 ft. 2 in. to 4ft. gin.). The most economical width of row was the subject of enquiry at Audubon Park Experiment Station, where it was found that the narrower the row the greater was the purity of the juice and the yield of cane, but that in very narrow rows the increased yield of cane was barely sufficient to pay for the extra amount of cane required to plant up a field with narrow rows. Stubbs? suggests that that width of row which best admits of proper cultivation should be selected, and, following on this argument, five-foot rows have been adopted at Audubon Park. ee | en THE HUSBANDRY OF THE CANE I3E Source of Seed Cane.—Generally it is the young immature top of the cane that is used as a cutting or as “‘seed.’’ This scheme is defensible in that this part is of small value in the factory and that it contains besides a large proportion of salts and nitrogenous matter that serve as food for the growing plant until it has developed a root system of its own. This viewis supported by a large number of somewhat contradictory experiments made in Java dealing with the effect of manuring on the germination of the eye. The results of these tests in general point to a benefit when the older joints are used as seed and to no effect when the tops are used. The maximum quantity of manure ever necessary appears to be 5 grams of sulphate of ammonia per plant, or about 35 lbs. per acre. When the harvest and planting take place at the same period there will always be a supply of seed cane available, but when, as is often the case, these periods are separated, special means must be taken to obtain cuttings. In Cuba it is customary to leave a certain portion of the crop uncut to supply seed for the planting that takes place after the termination of the harvest at the mid-year. In this case the whole stalk of mature cane is utilized. A second scheme to obtain a supply of tops independent of the harvest is to “draw down”’ young cane of about six months’ age, and also in this case to use the whole stalk. In Java the growing of cane for seed has developed into an industry independent of the plantations proper. There it has been found that mountain-grown seed is less liable to attacks of seveh than is seed obtained from cane grown on the lowland plantations. Accordingly cane is first planted at an elevation of 5,000 to 6,000 feet in “‘ grandmother fields.” After six months’ growth selected disease-free stools are dug up and trans- planted to “‘ mother fields,” at an elevation of 2,000 to 2,500 feet. This process is repeated, and selected stools are next transplanted to “‘ daughter ”’ or “export fields’ at I,000 to 1,200 feet elevation. After seven or eight months’ growth here the crop is cut down and used for seed on the planta- tions, either directly for cane or in the establishment of a lowland nursery. In the Hawaiian Islands the formation of seed from growing cane is often forced during the harvest time. If, after flowering, the top of the cane be cut off, the upper joints sprout and grow into short-jointed, very woody pieces of cane containing numerous eyes. This abnormal growth, known locally as a “ lala,” is used as a cutting. A similar scheme obtains in Java, where, however, each joint as it puts forth a shoot is removed from the parent stalk, and planted separately as a one-eyed cutting. In this way nearly all the eyes of the cane can be induced to sprout. When planted, the leaves already formed are cut off, so as to reduce transpiration, until the cutting has developed a root system of its own, but experiments made there do not show that any benefit results from this practice. In Louisiana, where it is necessary to carry over seed from the harvest at the end of the year to the time of the spring planting, seed cane is preserved buried in the ground as a protection from frost. This process is known as “windrowing.”’ It is also in use in those islands of the Japanese Empire where a cane sugar industry is established. A peculiar method of obtaining seed in use at Ganjam, in British India, is described by Subra Rao.? In June the seed cane is planted in a seed bed so close as to leave no space between the individual cuttings, which are of three joints each. In the middle of August the cuttings that have by then sprouted are transplanted to a nursery about five times the size of the seed bed. The nursery is laid out in furrows about 18 inches apart. In the following May the crop is cut 132 CHAPTER VIII down and used to supply seed for the plantation or is sold to cultivators. The same method is in use in Java. Cultivation.—By cultivation is here meant the working of the soil and the keeping down of grass and weeds during the period between the planting of the cane (or spring of the ratoons) and the harvest of the crop. British Guiana.—In British Guiana and in other places dependent on manual labour a typical routine is as follows :—Shortly after a crop of cane has been taken off, the soil in between the rows of cane is turned over with agricultural forks ; this process is known as “ forking banks”’ ; in about a month the weeds and grass that have sprung up are cut down with the cutlass, the machéte, or the hoe, a process which will have to be repeated every one or two months until the canes are of such a height as to keep down the growth of weeds. Simultaneously with the weeding, earth is hoed over the cane row, the process being known as “ moulding’’; in some parts, especially in Eastern Asia, this moulding is carried to an extreme pitch, the cane rows being earthed up to a great extent. In some places, as in Cuba, the keeping down of the weeds often forms the only cultivation that the cane receives. Louisiana.—Stubbs* thus describes the routine followed at Audubon Park in Louisiana :— ** The land is broken flush with a large plough, pulverized with a harrow, and bedded with two-horse ploughs. The rows are opened with a double mould-board plough, cane planted and covered, and middles broken out with the double mould- board plough. The quarter drains are opened six inches between the middle of the rows and the ditches are cleaned. At the proper time the cane is off-barred with the two-horse ploughs, scraped with hoes, and when large enough is fertilized by scattering the mixture across the open furrows and narrow ridge of cane. The dirt is returned as soon as fertilizer is applied, the middles broken out deep and clean, and the turn ploughs sent to the barn to remain until the next season. The disc cultivator, with the three small discs on either side, is used for throwing dirt to the cane at the first working, and the middle or diamond cultivator for breaking out the middles. In the second and third cultivations two middle discs replace the three used in the first, and are set to such an angle as to throw the desired amount of dirt to the cane, and are followed each time by the middle cultivator, thus completing the work with the twoimplements. At“ lay-by,’’ the large or“ lay-by ”’ discs are used, followed by the middle cultivator with its two front shovels removed. By proper adjustment of the two instruments, ridges of any desired height can be made and the cane properly laid by.’’* Hawaii.—On the irrigated plantations mechanical cultivation is not possible and weeds have to be kept down by hand ; on a rainfall plantation the grass is mainly kept down by the use of disc cultivators run astraddle the row and turning the soil away from the cane ; this leaves only a small area to be hand hoed. After the first hoeing, fertilizer is scattered between the rows and incorporated with a tine cultivator or other implement, the soil being stirred as much as possible. On ratoon fields, the first operation after taking off the crop is usually slicing the row; manuring follows at once, after which the soil is thrown back to the row by a disc cultivator run astraddle the row. A stubble digger (an appliance consisting essentially of a series of small tines revolving on an axle as the carriage is drawn along?) is then *To those familiar with hand husbandry only, this description requires some amplification. In the Hawaiian Islands off-barring is termed slicing the ratoon row, and this term conveys a better impression of the process; the instrument used is a disc plough of the type shown in Fig. 29; itis drawn alongside the ratoon row, cutting through the old roots, throwing the dirt away from the row and leaving an open furrow alongside the cane; after the furrow has been exposed for two or three days the dirt is thrown back to the row by the aid of disc implements. It should be noticed that animal power cultivation does not altogether dispense with manual labour ; in all cases the weeds and grass in the row itself have to be cut down by hand tools. +See Fig. 38. THE HUSBANDRY OF THE CANE 133 passed over the row so as to mix the manure and soil and loosen up the latter ; weeds between the rows are kept down as described above. Cuba.—F. S. Earle® gives the following account of a method of cultiva- tion advocated by the Cuban Experiment Station as the most practical under the conditions there :— “The system recently advocated by the Cuban experiment station, while it has not yet stood the test of long-continued use, promises to solve satisfactorily the question of continued production of profitable stubble crops. Itis as follows :— Plough the land intended for fall cane in the winter or spring. Plant to velvet beans in April or May. Plough these under with a disc plough in August and September. Harrow two or three times with the disc harrow. In October open deep planting furrows with the sulky double mould-board plough, spacing them about seven feet apart. Scatter tankage and potash or some similar complete fertilizer carrying about equal parts of nitrogen, phosphoric acid, and potash in the bottom of the furrow, at the rate of 500 ]bs. peracre. This is best done with a two- horse fertilizer drill. A small cultivator shovel attached at the rear of the drill will serve to mix the fertilizer at the bottom of the furrow. Nowdropa continuous row of seed cane in the bottom ofthe furrow. Itis best to select plant cane or vigorously growing stubble for seed. Using that from old worn-out stubble fields is inadvis- able, as it will make a weaker, less satisfactory growth. Cover with the disc cultivator, setting the gang to throw more or less dirt, according to the condition of moisture. If the ground is moist, germination will be prompter if the cane is not covered more than two or three inches. If it is dry, it is necessary to cover six or eight inches deep to prevent the drying of the seed canes. In from one to two weeks, or just as the canes are peeping through the ground, harrow the field thoroughly with the smoothing harrow running lengthwise of the rows. This will kill any small weeds that may be starting, and will freshen the surface of the soil and greatly aid germination. When the young plants are well up so that they show from one end of the row to the other, begin cultivating with the ordinary riding two-horse corn cultivator, of course straddling the row so as to cultivate two rows at once. The seven-foot rows are so wide that there will be a strip in the middle not reached by the cultivator. This can be finished by the ordinary walking cultivator of the Planet Junior type, or the narrow cultivator blades may be removed from the regular cultivator, and eight-inch cut-away sweeps be bolted on instead. These will have a wide-enough cut to meet in the centre, and as thus rigged the same implement makes a good middle cultivator. Cultivation should be repeated throughout the winter as often as is needed to keep down all weeds and maintain a dust mulch. Before spring the growth of the cane will be so great that the row can no longer be straddled, and the middles only can be cultivated. In April or the first part of May sow cow peas broadcast in the middles, cover them with the cultivator and the work is finished. Up to this point the plan does not differ materially from the ordinary system except that the use of the riding corn cultivator, which works so close to the row, makes it possible to almost dispense with the expensive hoe. It is only the few weeds and bunches of grass that come up directly in the row that have to be cut with the hoe, or better still be pulled by hand. The line of cultivation thus outlined will leave the land practically level. This is right for the red lands, since they have natural under-drainage, but in the wetter black it should be modified by using disc cultivators which ridge up the row as in Louisiana. ** As soon as the cane is cut, take an ordinary horse rake and drive so as to cross the cane rows, raking the trash from one middle and dumping it in the next one. This quickly and cheaply clears half the ground so that it can be ploughed and cultivated, and it provides a double mulch of trash for the other half which makes it so thick and heavy that practically no grass or weeds can come through, and these middles will require no further attention for the season. Now plough the cleared middles with a two-horse turning plough, throwing the dirt away from the cane. Run the last furrow up as close to the cane stubble as possible. You will not hurt the roots. They all died when the cane was cut, and the new ones will form as the new shoots of cane begin to grow. If fertilizer is needed, it can now be applied in this open furrow next the cane. On most lands, however, it will only be necessary to use fertilizer every third or fourth year. Do not leave the furrow next the cane open any longer than is necessary, but work the dirt back with the cultivator, using some implement that will throw a little dirt back over the stubble. Keep these alternate middles well cultivated until the beginning of the rainy season and then sow them down to cow peas. This will be found much cheaper than the ordinary plan of going over all the surface of the ground two or three times with 134 CHAPTER VIII hoes, and it leaves the stubble cane in even better cultural condition than the plant cane, for one side of each row is thoroughly cultivated, while the other side is protected by a heavy mulch of trash, which serves perfectly to retain moisture. The next year, of course, the middles are reversed so that all the soil is thoroughly aerated, and pulverized every twe years. And yet only half of it is exposed to the depleting influence of tillage, while all the trash is retained on the land and is ultimately incorporated with it to add to its supply of humus, a substance so necessary for successful tropical agriculture.” Generally, however, cultivation in Cuba is restricted to weeding with the hoe and the cutlass. A few plantations in the western half, it is true, use small ploughs to cut down the weeds on ratoon crops, but generally in no other cane-growing district is cultivation so neglected. . A system of cultivation due to Zayas was proposed for use in Cuba about 1908. It was suggested to plant the canes in rows about twelve feet apart and combine this with continuous cultivation. A selective harvest was also proposed, immature stalks being left over so that a contin- uous crop would result. The system was tried on a number of plantations in Cuba, but none of the results served as an incentive to the general adoption of the scheme. Java.—After the cane has been planted in the carefully prepared fields of Java, cultivation is confined to weeding by hand and to earthing up the young cane. Usually the continued turning over of the soil itself destroys the weeds, which never have a chance to become established. As already described, in Java the canes are planted in deep trenches, and the cultivation consists in first of all loosening the soil in the trench with the patjol, and then as the cane grows gradually working down the banks until the field becomes level. In this way some foot or more of the cane stalk becomes buried in the soil. Asit is exceptional in Java to grow ratoon cane, the methods of ratoon cultivation in vogue elsewhere find no place there. Trashing.—By this term is meant the removal of the dead leaves, which normally remain attached to the cane stalks. The alleged reasons for the process are :-— I. The removal of the leaves exposes the cane to the effect of light and air, and thereby hastens its maturity. 2. The dead leaves afford harbouring places for obnoxious insects, especially plant lice and mealy bugs. 3. Water lodging in the leaf axils promotes the development of the eyes and aerial roots, to the detriment of the cane. 4. The dry leaves being placed on the ground act as a mulch and help to conserve soil water. On the other hand it may be claimed that the ripening effect is small, and that the damage done by the labourers passing through the fields more than offsets any possible advantage. This will be particularly likely to happen when other than quite dead leaves are removed, as then the way may be prepared for the attacks of fungi. The question has been frequently put to experimental test. Bon&ame,* who writes strongly in favour of the process found :— A. Only completely dry leaves removed. y B. Canes trashed @ blanc, i.e., a certain number of green leaves removed. C. No trashing. Jal: B. C. Degree Baume .. ate 8-10 cc 7 Ou eres 7°70 Susar iper-cent.. «2. * J). S832 40) ae ea OOUn tty miele eo Glucose, per cent. 56 is Ont 15 Oise 1°20 . THE HUSBANDRY OF THE CANE 135 No weight of cane was recorded. But other experiments, on record elsewhere, give invariably very different results. In very detailed experiments in the Hawaiian Islands under a variety of conditions Eckart? found that untrashed cane gave both a higher yield and a sweeter and purer juice. Wrapping.&—This process, the reverse of trashing, seems to be confined to certain portions of southern India, where in some parts the dead leaves are wrapped round the cane. It is intended partly as a protection against jackals and partly to diminish rooting and sprouting habits. Tying up.—In Java it is customary to tie together the upper parts of the canes in different rows to keep them from “ lodging ”’ or lying down on the ground. Weed Destruction by Spraying.°—Eckart, at the suggestion of Agee, has put into operation at the Olaa plantation in the Hawaiian Islands a system of weed destruction based on the use of arsenicalsprays. The material used is thus prepared :—2o Ibs. of arsenious acid, 4—5 lbs. of caustic soda, and ro U.S. gallons of water are boiled for 10-15 minutes; 15 gallons of this stock solution are diluted to 600 gallons, which is used as the spraying mixture. Of this material from 50 to 75 gallons are required to destroy the weeds on one acre, the total cost for labour and chemicals amounting to 65 cents per acre. In applying the spray the cane itself is protected from damage by its coating of wax, and the small quantity, six to seven lbs., of arsenic that finds its way to the soil is believed to be negligible and to be fixed in an insoluble state by the ferric oxide normally present. The pro- cess does not appear to have extended. Paper Mulches.1°—Eckart has also introduced a second radical departure in cane agriculture. He uses surplus bagasse as a source of paper which is made on the plantation. The paper is laid in strips both on the cane row and on the space between the cane row, and is intended to serve two purposes : 1. The prevention of the growth of weeds, which cannot penetrate the paper, the cane shoots being able todoso. 2. The formation of nitrate beds between the rows where, owing to the increased temperature and to the absence of light, nitrogenous organic matter in the soil will be rapidly converted into nitrates by the action of the soil bacteria. Cutting Back.—The flowering season in the Hawaiian Islands is during the months of November and December. Cane that has been cut early in the year will flower that same year and will have to be harvested after a twelve months’ growth ; such cane is termed short ratoons. By allowing such cane to grow till June and then cutting it back, it can be carried over the flowering season of that year and will flower in the November of the following year, thus giving a 17 to 18 months’ period of growth from the time it was cut back till it flowers, and a total period of growth of not less than two years by the time it is harvested. Such cane is called long ratoons. Influence of Arrowing on the Cane.—Arrowing marks the end of the vegetative period of the growing cane. It has been thought that arrowing has an influence on the sugar content of the cane; but definite experiments 136 CHAPTER VIII by Harrison and by Prinsen Geerligs!*? have shown that this belief is unfounded. After the cane has arrowed no further formation of sugar takes place, but an elaboration of that already formed obtains with an increase in the cane sugar content and in the purity; eventually, however, the cane - dies down and then a breaking down of the cane sugar occurs. The time to which cane can be left standing after arrowing is very variable and is dependent on variety and climate. In the Hawaiian Islands cane may re- main as long as six months after arrowing, before deterioration sets in. Selective Harvesting.—In healthy cane there is a point at which the cane contains a minimum of, or even no, reducing sugars and where it is at its maximum purity; after this point there is a breaking down of the cane sugar into reducing sugars and the cane is over-ripe. In some varieties this reversion is very rapid and it is also influenced by climatic conditions ; it is then a matter of great importance to harvest a field of cane at the time of its maximum purity. The system under which this selective reaping is pursued is thus described by Prinsen Geerligs!® :— “The cane fields are divided into plots which have been planted and manured at the same time and in the same way. After ten months of growth take from each plot 40 normally grown cane stalks, and mark and number them. Every fortnight one cane stalk is cut from each one of the stools and the bundle carried to the laboratory, where the green top end is removed and the canes are measured, weighed, and crushed in a Small test mill, after which the juice is analysed. The analytical data from each analysis of the test plot are entered down, so that an increase of sucrose content or purity, or a falling in them, can be detected at once. As soon as the sucrose content or purity ceases to augment, the cane of the plot under review has attained its point of maturity, and should be cut in order to prevent deteriora- tion by too long standing in the field.”’ In some instances this process is followed in conjunction with a portable travelling field laboratory. Period of Ratoonage.—The number of crops that may be taken off an area with one planting varies very greatly as between different districts, and has an important bearing on the economy of a plantation. Generally, the more crops of reasonable magnitude that can be obtained from one planting, the greater is the benefit to the plantation, and indeed in some localities the plant crop results in a loss, the profits being entirely due to the ratoon crops. It is often stated that the yield per acre progressively falls with each crop of ratoons, and, although over long periods there is a gradual falling off, very often it will be found that first and second ratoons give a harvest equal to that afforded by the plant crop. The period of profitable ratoonage depends both on soil and variety. As long ago as the very early years of the eighteenth century Rumpf!* observed and regretted that canes in the East Indies did not afford the same long period of ratoonage as was given in the New World. Similarly Humboldt!’ has recorded that at the introduction of the Otaheite cane to Cuba the planters were fearful that it would not be found to have good ratooning qualities. It has also been observed that many of the newer seedling canes are bad ratooners, and some even degenerate into reed-like stalks after a few years’ continuous growth. Practice in different countries varies very greatly. In Java the crop is almost entirely “‘ plant cane.” This follows on the system of land tenure there, which does not allow Europeans to rent the same area of sawah land for more than eighteen consecutive months. In Louisiana it is customary THE HUSBANDRY OF THE CANE 137 to take off plant cane and first ratoons. In Mauritius the fields are allowed to grow up to third ratoons as a general rule. In Cuba, the West Indies and in British Guiana fifth ratoons are not uncommon, and fields that have not been replanted for a generation may be found. Much of this land has, however, been supplied with tops from time to time, so that little of the original stock may remain. In Hawaii canes are seldom allowed to grow beyond third ratoons. Generally speaking, it is only those familiar with local conditions who can determine the profitable period of ratoonage. Long-continued ratoonage has been connected with the prevalence of various diseases, particularly those affecting the root and root stock, as in in this case the causal fungus has a continuous habitat. Yield of Sugar per Acre.—The return of cane and of sugar per acre is determined by the soil, the climate, including herein temperature, rainfall and its distribution, the use or not of irrigation and of manures, the efficiency of the cultivation, and the degree of ratoonage practised. The highest yields are those which are obtained on the irrigated plantations of the Hawaiian Islands, where the canes are often allowed a period of growth of twenty months. Yields nearly equal in magnitude are obtained on the irrigated lands of Peru, but probably the greatest return per acre per year is to be found on the plantations of Java where the crop is almost entirely plant cane. Outside of these favoured areas the yields are much smaller and probably do not average much over twenty short tons of cane, or two short tons of sugar per acre. The maximum yields that have ever been reported are in the Hawaiian Islands, where crop averages on large planta- tions of more than 20,000 lbs. of sugar per acre have been recorded, and where a single field of over 300 acres has been known to yield at the rate of just Over 100 short tons of cane and 15 short tons of sugar per acre. Some actual records, all in short tons per acre, are given below. Java.1*—For the years stated the returns have been :— Year. Cane. Sugar. Year. Cane. Sugar. 1894... za* 29°0 3°14 1899 _.. ca BGs a 3°97 ESOQS5u-, =i Paes 6 ke, 3°29 Ig0o0 .. Scie 7 ME 3°68 1896... Shales De 3°19 FQOR Te Pees ta: 3°47 ESOT Soe ata B24 3°47 EQO2y) i Yass rk 3°81 1898 _ .. Teneaote 3°97 E909)". ; » Oe oe 3°97 Later results have shown a distinct increase, the return of sugar for the years 1906, 1907, 1909, IQII, IgI2, being 4-49, 4°55, 4°77, 4°49 and 4-47 tons respectively, corresponding to a yield of from 40 to 45 tons of cane per acre. This regular and progressive increase is to be attributed to the appli- cation of the results of technical research. Hawau.17—For the period 1895-1910 the return of sugar per acre has been as below expressed in short tons per acre. On the irrigated plantations a distinct rise in production (equally, as in Java, to be attributed to the teachings of applied science) is seen, and this is actually more than the figures indicate, since it was only the more favoured areas which were planted in the earlier years. The rainfall plantations show the effect of climate. The yield from cane is, when averaged over a long period, a little under I4 per cent. from irrigated and a little over 11 per cent. from rainfall cane. 138 CHAPTER VIII Irrigated. Rainfall. Irrigated. Rainfall. 1895 3°83 2°65 1903 ate 6:19 3°86 1896 4°52 3°68 1904 ae 5°60 2°60 1897 5°08 4°35 I905 6:08 2°81 1898 5°03 2°97 1906 5°76 3°07 1899 6-08 3°53 1907 5257 3°02 Ig00 Oni 3°13 1908 6:33 3°83 IQOI 6:19 3°28 I909 6-48 3°48 1902 5°84 3:00 IgIo 62277 3°06 Mauritius.18—Over the years 1892-1905 the average yield of cane was 20-6 tons per acre, with extremes of 27:6 and 7-0, the result last quoted being obtained in a year of great drought. The corresponding return of sugar would be in the neighbourhood of 2-25 tons per acre. Cula.1®—For the year 1909 the average over the whole island was 18-6 tons of cane per acre, corresponding to a little over 2 tons of sugar. With the increased acreage of virgin land that has since been planted in eastern Cuba the return now (1920) will tend to be higher, and is probably a little over 20 tons. Queensland.1®—-For the years 1909 and Iogio the yield of cane was 16-0 and 20:3 tons, the return of sugar being 1-77 and 2:32 tons per acre. British India.1°—For the years 1898-9 to 1905-6 the average production from the reported acreage was 0-96 ton of very crude sugar per acre. Peru.—The occasional statements that appear indicate that here the irrigated plantations give a very high yield, little if anv less than that obtained under similar circumstances in the Hawaiian Islands. For all the other districts engaged in growing cane, it is safe to con- clude from the occasional statements that appear that the average production of sugar lies in the neighbourhood of two short tons per acre. REFERENCES IN CHAPTER VIII 1. Int. Sug. Jour., 1904, 6, 277; 336. 2. Stubbs’ “‘ Sugar Cane.”’ 3. Dept. of Lands, Records and Agric., Madras, 2, 102. 4. Stubbs’ “ Sugar Cane.”’ 5. Southern Agriculture. 6. Culture de la Canne a Sucre 4 Guadeloupe. 70 Elo. beAn Ex, Sta. Agric. Ser, Bulle 2s. 8. Department of Lands, Records and Agric., Madras, 2, fo. 9. H.S.P.A. Ex. Sta., Agric. Ser., Bull. 44. to. U.S. Patents 1,227,989; 1,249,355; 1,274,527. Dts p OG lso4. 2On223° 12... S$. G., 1895, 27, 70s (1898, 30, 258- 13. Int. Sug. Jour., 1904, 6, 381. 14. Journey to the Equinoctial Regions of South America. 15. Herbarium Amboinense. 16. From occasional statements and consular reports. 17. Int. Sug. Jour., 1910, 12, 326; Cyclopedia of American Agriculture, 1, 106. 18. The Sugar Industry of Mauritius. 1g. Dictionary of the Economic Products of India. Ce PR noe THE PESTS AND DISEASES OF THE CANE THE cultivation of the cane in all districts is one continuous struggle against its pests and diseases, and the study of methods for their control is one of the chief occupations of the experiment stations connected with the industry, and of the Departments of Agriculture in tropical colonies. No incon- siderable literature has arisen in the past thirty years, and only the fringe of the subject can be touched on here. Abnormalities in Canes.—Peculiar canes with aborted joints, with a superabundance of eyes, with excessive development of woody tissue, with albino leaves, and with other peculiarities, are not infrequently en- countered. A peculiar case was observed in the Hawaiian Islands when a seedling, H 10, with otherwise very desirable qualities, was found to have developed the habit of regularly forming its upper joints without eyes. Generally these peculiarities, known to botanists as chimeras or unicums, have only an academic interest. Weeds.—The majority of the weeds that appear in cane fields also belong to the grasses. Amongst the more frequent members may be mentioned Bermuda grass (Cynodon dactylon), various species of Paspalum, Andropogon, Panicum, Agropyron (Couch grass) and Sorghum (Johnson grass). Certain other specialized inhabitants of cane-growing districts have been put on record. Thus in Trinidad! the plant Alectra brasiliensis is known as the “cane killer,’’ the roots of the weed being parasitic on the roots of the cane. In India Striga lutea is common on cane lands, an allied plant, Arginetia brassica, being similarly known in the Philippines. A third frequent pest of the eastern tropics is the “ ilang ilang”’ grass, Avundinacea imperata. The most widely distributed and most obnoxious tropical weed is the “ nut grass’’ or “ coco grass,”’ Cyperus sp., of which three varieties are known in Java, where its local name is “ teki.”” This sedge is an in- habitant of Southern Europe, and was recognised as an introduced pest in Barbados by Hughes? in 1750, and a few years later by Aublet® in Maur- itius. In the former case it arrived in a pot of ornamental plants imported by a Mr. Lillington. A similar pest, “‘ knot grass,”’ Scirpus hydra, is recorded by Peterkin* in 1790 in St. Kitts, and is believed by him to be a visitor from the Carolinas. According to Dewey,° the most efficacious way to eradi- cate this weed is not to attack the underground tuber but to cut down the stems before they set seed. The introduction of plants of any nature to an agricultural district is attended with danger, and classical instances of the damage that can be done are those connected with the Scotch thistle in Canada and the water hyacinth 139 140 CHAPTER IX in Florida. In special connection with the cane sugar industry may be mentioned a woody shrub, Lantana camara, known as Lantana in Hawaii, and as “ vielle fille’’ in Mauritius. This was brought as an ornamental plant to Hawaii and rapidly became a serious pest, taking over pastures and abandoned or fallowing cane fields. This plant is an inhabitant of Mexico and the West Indies. Koebele,* knowing of its presence there, but not as a pest, was led to investigate the cause. He found that it was controlled by a fly, Agromyza sp, which oviposited in the seed, and by two moths, Platypstilia rusellidactyla and Crocidosema lantana, which attacked the flower heads. The introduction of these insects into Hawaii resulted in a very short time in the almost complete disappearance of the weed. A similar introduction into Cuba of an ornamental plant, Dichrostachys nutans, of habitat Northern Africa, has resulted in the covering of many acres of pasture land with dense thickets. In Cuba this plant is known as “aroma.” It is an acacia-like shrub, with showy violet and yellow flowers. The eradication of weeds should not, however, be confined to the fields alone, but should extend to the roads and vicinity of the fields, since such places may act as foci of infection whence seeds may be continually carried by natural agencies to the cultivation. In addition, as pointed out at greater length elsewhere in this chapter, such weeds may serve as breeding places for obnoxious insects, and as host plants for fungi that also attack the cane. In certain British Colonies the destruction of weeds on road-sides has been made compulsory on the owners of lands abutting thereon. The usual method of destruction of weeds is by the use of the plough or by the hoe and cutlass, and forms a part of the regular routine of any farming ndustry. The use of plant poisons has been experimented with for many years past, and considerable interest has attached to the use of sodium arsenate as developed by Eckart at the Olaa plantation in the Hawaiian Islands. (Cf. Chapter VIII.) Mammalian Pests.—The most important mammalian pest of the cane is the rat; it is of cosmopolitan distribution and was observed as a cane enemy by Captain Cook in the eighteenth century in even so isolated a part of the world as the Island of Tanna.? At times, in British Guiana for example, rats appear in enormous numbers, and not only destroy cane, but also do damage to dams and parapets. Hares are known as a cane pest in Mauritius, where they do no inconsiderable damage. Elephants, bears, jackals and wild pigs must be regarded as cane pests in India. It is not perhaps altogether wrong to include the labouring population as an occasional enemy. This is particularly true in Cuba, where incendiary fires are of frequent occurrence. These fires are often set so as to force the administration to raise the price of cane cutting in order to harvest the burnt areas before the cane has quite spoiled. Insect Pests.—The cane, in common with other crops, is attacked by a large number of insects. The majority of these pests attack the cane in common with other plants in search of food, but some have become almost specialized in their habits in regard to the cane. As regards their systematic position, the most serious pests are included in the lepidoptera (moths and butterflies), the coleoptera (beetles) and the rhyncota or hemiptera (bugs in its technical sense). The damage is done by the larve of the first two classes, the perfect insect being the destructive agent in the case of the third class. THE PESTS AND DISEASES OF THE CANE I4I Classified according to mode of attack, the major pests may be distinguished as :— 1. “Borers,” or the larve of certain lepidoptera and coleoptera, which bore tunnels into and destroy the stalk. 2. Root-eating larve (grubs) of many coleoptera, which pass their larval existence in the soil. 3. Leaf-eating larve of numerous lepidoptera. 4. Leaf and stem puncturing insects belonging to the hemiptera. Lepidopterous Borers ——The moth borers have been associated with the sugar cane almost from the time that its growth became an organized industry. The earliest description is due to Hamilton® (1734). They were established as a pest in Guadeloupe in 1758, and are described by Beckford® and Peterkin® in 1790. In systematic entomology the earliest descriptions are those of Fabricius!® (1789), who described the West Indian borer as Phalena and of Guilding! (1829), who made the genus Diairea. Of the pests catalogued below, Nonagria and Sesamia are Noctuids, Grapholitha is a Tortricid, Diatrea, Chilo, Polyocha, Scirpophaga, and Anerastia are Pyralids. All these are very closely related genera. Castnia licus is, however, a Castnid and has little affinity to the other genera; the moths in this genus possess clubbed antenne and thus form a link between the Rhaplocera (moths) and the Heterocera (butterflies). The borers that have been observed are catalogued below :— Top Borers.—Scirpophaga aurifiua. The white borer of India. Sc. monostigma. The black-spotted borer of India. Sc. tniacta. The white borer of Java. Sc. chrysorrhea, India. Chilo infuscatellus. The yellow borer of Java. Grapholitha schistaceana. The grey borer of Java. STEM BorERS.—Diatrea saccharvalis. The West Indian borer. D. canelia. Demerara. D. tncohati. Demerara. D. striatalis. The grey stem borer of the East Indies and Australia. Chilo auricilia. The gold-fringed borer of India. C. simplex. India. Nonagria uniformis. The pink borer of India, Anerastia albutella. The green borer of India. Sesamia nonagrioides. The purple borer of Java, East Indies, Madeira, Maur- itius, Spain, North Africa, Madagascar. Casinia licus. The large or giant borer of tropical America. Root Borer.—Polyocha saccharella. India. As will be seen from the above list, the borers have a very wide distri- bution, the only considerable district free from them being the Hawaiian Islands. All the borers have a very similar mode of attack. The female oviposits on the leaf whence the caterpillar on emergence penetrates the cane usually near an eye (stem borer) or near the vegetative point (top borer). In the latter case the shoot is killed, but in the former the damage is confined to destruction of sugar, to impure juices, and to liability to fungus attacks, particularly of red rot (Colletotrichum falcatum) as a wound parasite. Figs. 43 and 44 illustrate the different modes of attack of the stem and top borers. The large or giant borer or cane sucker, Casinia licus, has different habits. The eggs are laid near the ground and the caterpillar penetrates the lower portion of the stem and also the underground system of the cane. The larva and moth of Diatrea striatalis and of Sesamta nonagrioides are shown in Plate XVI, Nos. 1 and 2, 3 and 4. 142 CHAPTER IX Because of theit economic importance the borers have been studied in great detail. As they occur in Java reference may be made to Kruger and Van Deventer. Maxwell Lefroy has described the West Indian borer!” and the borers of British India.1% That of Mauritius has been described by Bojer!* as Proceras saccharifagus, and by Delteil as Tortrix saccharifaga, and that of New South Wales by Oliff.* A full description of Diatrea in the southern part of the United States has been given by Howard. Here it also appears as a corn stalk borer. The following life history of the West Indian borer is due to Maxwell Lefroy :— “.... the eggs are flattened, oval and slightly convex, about 1 /25th inch in length; they are laid in clusters on the leaf of the cane, the number being very variable, lying between 4 and 57, and being generally from 10 to 30. The eggs when fresh are light yellow ; in 36 hours a tinge of orange appears, and eventually they turn orange brown; in the final stage the centre of the egg becomes black. If the eggs are laid on young cane, the part attacked is the axil of the leat or the leaf itself ; in the case of older cane, the part attacked is the joint, the caterpillar eating its way into the cane from which it eventually emerges in from 30 to 35 days. The period of pupation which takes place inside the cane is six days, after which the perfect insect emerges. The moth is inactive by day, and, only living 4 days, lays in that time from 100 to 300 eggs.”’ Pei Fie 44 Leaf-eating Caterpillars —Occasionally cane-growing districts are visited by great numbers of leaf-eating caterpillars, which appear suddenly and as suddenly disappear. Most of these are the larve of noctuid moths, the most notorious being the “army worm,” Cuirphis (Leucania) unipuncta, the “grass army worm,” Spodoptera mauritia, and various cut worms belonging to Agrotis and allied genera. Very many of these pests are known, Swezey!® having observed thirty-five species in the Hawaiian Islands alone. THE PESTS AND DISEASES OF THE CANE 143 The causes of the epidemics are obscure; in some cases local conditions, such as floods, may have caused them to desert their usual feeding places. Minor Lepidopt-rous Pests ——Of the lesser lepidopterous pests may be mentioned various ‘“‘ bud worms,” or the larve of Tineid moths belonging to the microlepidoptera, and mostly included in the genera Eveunetis and Opogona. Normally these larve feed on the dried leaf sheaths, but they also penetrate and destroy the eye of the cane. They are of very wide distri- bution. Another minor pest is the “leaf roller,’ Omoides accepta, which does a certain amount of damage in the Hawaiian Islands. The life history of both of these classes has been worked out by Swezey.?’ Coleopterous Pests——The coleoptera are equally destructive with the lepidoptera, but with one notable exception their method of attack is different. Nearly all the coleoptera which have been observed as cane pests pass their larval stage underground as root eaters. They are popu- larly known as grubs. The chief species of the root borers that have been studied are :— Apogonia destructor,18 the Wawalan beetle of Java, illustrated in Plate XVI, Nos. 5, 6, 7: Many species of Lachnosterna (May beetles), Diaprepes, Prepodes, and Ligyrus 1*(hardbacks) in the West Indies. Lepidiota albohirta®® (cane grub or grey back beetle) in Australia. Anomala sp.*1 in Hawaii. Phytalus smithi** in Mauritius. Of these species, Anomala, Apogonia, Phytalus, and Ligyrus are lamelli- corn beetles, Lachnosterna and Lepidiota are scarabids, and Diaprepes is a curculionid or snout beetles The damage done by these insects is very great, but, as the destruction is not so patent, they have not become so notorious as have the lepidopterous pests. Of all of them, that which causes most harm seems to be Lepidiota albohiria in Australia, which, in spite of the efforts of skilful entomologists, still remains an imperfectly controlled pest, sometimes causing the aban- donment of otherwise suitable areas. The life history of a West Indian root borer, Diapr:pes abbreviatus, © is thus given by Watson.?% “In August and September the perfect insect lays its eggs on the upper surface of the leaves, and after 10 days the grub emerges and falls on to ground, immediately burrowing into the ground in search of food. The grub remains in the soil for 312 days, eating the root of cane, sweet potato, etc., and then pupates, the perfect insect emerging in fifteen days to repeat the same cycle. The grub at first is only 1/18th inch long, reaching at maturity a length of one inch.”’ The-most dangerous coleopterous pest other than the root borers is the Hawaiian weevil borer, Rhabdocnemis obscurus. This insect occurs as a pest all over the Australasian region. It is illustrated together with a piece of damaged cane in Plate XVI, Nos. 8 and g. The life history as given by Koebele** follows :— ““ The female beetle is easily separated from the male by its longer, smoother and more slender beak, and its pointed terminal segment. She lays her eggs consecutively, probably 4 to 8 each day, but less than this toward the end of the period of eight months during which she continues to lay. When the egg is laid in the cane from the outside this is done from under the sheath, which the beetle 144 CHAPTER IX can brace against; with the saw-like movable teeth laterally she first begins to eat out the hole until softer ground is struck, so to speak, when she will force the work, moving the head up and down as well as sideways, until the whole length of the beak is buried. “Upon soft parts of split cane this operation takes from 13 to 2 minutes ; no doubt much longer in boring through the hard epidermis, probably hours. After the hole is completed, the beetle walks up and inserts the ovipositor, remain- ing in this position from 4 to 6 minutes. The bone-coloured egg is found embedded parallel to the fibres. Itis about 2mm. long by 1 mm. in thickness, and slightly bent. The holeclose to this is filled in with mucous matter intermixed with par- ticles of fibre. Repeated observations show that these eggs hatch in six days. The newly hatched larva is at first transparent as the eggs of the latter production, the first being of a more opaque colour as also the young larve, with the head of a dark yellow colour. We found that the young larve went out in the same direction as fibres about one-eighth of an inch deeper, having made a hole one inch long in from four to five hours. As the larva increases in size, its power of boring becomes more rapid. A half-grown specimen traversed a piece of cane six inches in length, from end to end in three days.”’ A closely allied species, Matamarsius hemipterus,* is also known as a minor pest of similar habits in the West Indies.?° Of minor coleopterous pests there may be recorded the “ bibit keever,” or cane-top beetle, Holonaria pisescens,?® the perfect insect attacking the eyes of the cane; and several ‘‘ leaf miners,” such as Aphanisticus krugert and Hispella sacchari,2” which feed on the leaves. The two last-mentioned insects are only reported from Java. Hemipterous or Rhyncotous Pests-The Hemiptera are a great order of insects, characterized by the development of the mouth parts into an organ known as the beak or rostrum and adapted to the purpose of sucking animal or vegetable juices. The phases of insect life known as lice, blights, blast, scale, bugs (in its technical sense), are included in this order. The damage done is material through the destruction of tissue in stem and leaf, and this is then followed by fungi that gain entrance through the wounds thus made. Although these insects are very small, and though the actual damage done by each individual is almost inappreciable, yet the enormous numbers in which they occur, due to their great prolificness, make them one of the major dangers to agriculture. Of those that have become the most notorious may be cited the asciracids, Delphax saccharivora*® (the ‘“‘ cane fly”’ or “ spittle fly’’ of the West Indies), Perkinsiellia saccharicida”® (an Australian species), the ‘‘ leaf hopper”’ of Hawaii, and Dicranotropis vastatrix®® of Java; the coccid, Icerya seychellarum, (pou a poche blanche of Mauritius),*! and the cercopid, Tomaspis posticata, the frog hopper of Central America and Trinidad. Of minor pests that have been recorded may be mentioned various coccids, such as Tvechocorys (dactylopius) calceolarie,* the ‘‘mealy bug,” of very wide distribution; certain aphids, such as the black and yellow “blast ’’ in the West Indies, Aphis setarie and Sipha flava ;*4 the white and the green louse of Java, Oregma (Ceratovacuna) lanigera, and Aphis sacchari. This last species is illustrated in Plate XVI, No. Io, and shows the enormous number of these insects that may occur in a limited area. Orthopterous Pests.—The orthoptera do not include any major pests of the cane. The one of most interest is the “mole cricket,” Scapteriscus didactylus, of the West Indies. While a general feeder, this insect only attacks the cane incidentally. During the day it feeds on roots underground *The two insects discussed above were formerly known as Sphenophorus obscurus and S. sericeus, and it is under these names that they are described in all but the more recent literature. PLATE XVI. y reed HT cn * Ta) 1 ete yo PEP es ~ oo Seek + @igcesrce SAF ph me Y ai og THE PESTS AND DISEASES OF THE CANE 145 and emerges at night to attack the crop above ground. It only becomes dangerous when for some reason the natural balance has been disturbed. Another widely distributed cricket, Gryllotalpa africana, in addition to feeding on the cane, does damage to irrigation ditches in the Hawaiian Islands by means of its tunnels. White ants, Termes taprobanes, have been recorded in India by Hadi’? as attacking seed cane and the young shoots after germination, and are to be regarded as a major pest of that country. In Java the “ thrips” or “bladder feet,’’ sometimes included in the orthoptera, have been observed ~ as a minor pest. Acarid Pests.—Mites are a form of life frequently found on cane, but the damage done is usually trifling. A serious amount of harm was done in Queensland in 1876 by a mite, Tarsonvmus bancroftit.38 The disease was then known as “‘cane rust.’’ These mites are also present in Java and in Barbados. To a certain extent they are to be considered beneficial, since Ormerod has observed the parasitization of the eggs of the West Indian borer by this form of life. Worms.—Certain nematode worms have been recorded as attacking cane. Of these there are Heterodera radicicola*® and Tylenchus sacchari in Java.‘ At one time these worms were thought to be connected with the Sereh disease. More lately Cobb** has described a nematode, Tylenchus similis, which he has observed as parasitic on the roots of sugar cane and banana in both Hawaii and Jamaica. Insect Epidemies.—In the history of the sugar cane are to be found numerous instances of insect epidemics. In most of these there has been a short period in which the presence of the insect was casually observed. This has been followed by a period over which the damage occasioned has been intense. Eventually the pest reaches a permanent endemic stage, with irregular outbreaks of the epidemic phase. This course of events follows on certain “‘ natural Jaws,’’ discussed in another section. Of insect epidemics of greater interest, there may be recorded :— 1. In 1760 an extraordinary plague of ants, which has been described by Castle’, appeared in the West Indies. Both Castle and Hughes* seem to think that the ants were attracted as predators to the “ blast ’’ due to aphides at that time prevalent on the cane. This “ blast”’ is frequently referred to by the early writers on the West Indies; a yellow blast, probably due to the aphis, Sipha flava, and a black blast, probably due to a second aphis, Aphis setariz, were distinguished. 2. In the early part of the nineteenth century much damage was done by an asciracid, Delphax saccharivora. This insect had been present for many years, and reached the epidemic stage about 1830, the destruction of cane being particularly great in Grenada.®® It still remains as a major pest in Jamaica. 3. The “ pou-a-poche blanche’’ became exceedingly destructive in Mauritius about 1860.31. This epidemic was caused by a coccid, I[cerya seychellarum, a second coccid, Pulvinaria iceryi, being also present. Although a definite statement is impossible, it is highly probable that this insect arrived in Mauritius with canes imported from Australasia. 4. About 1850 a very serious outbreak of “‘ moth borer”’ occurred in Mauritius.14 It is almost certain that the pest in this case was introduced L 146 CHAPTER IX in a consignment of cane from Ceylon. The infection of the canes was observed, and orders were given for their destruction. It is believed that some ill-advised planter surreptitiously obtained cuttings and planted them in the Flacq district. 5. In Porto Rico in 1876, consequent on the destruction of the avian population by a hurricane, the mole cricket, Scapteriscus didactylus, caused great damage not only to cane but to all crops.*° 6. Early in the twentieth century the “leaf hopper,” an asciracid, ' Perkinsiellia saccharicida, appeared in Hawaii,?* and for three or four years did great damage. Undoubtedly this pest arrived from Australasia. The story of this epidemic and its control forms a classic in economic entomology, ‘and is discussed at length elsewhere. 7. About 1910 serious damage was observed in certain parts of Mauritius, the cause being ascertained to be due to the larva of a root-eating lamellicorn - beetle, Phytalus smithi.22 This pest had been introduced with cane from Barbados, and in the latter island its presence was barely known owing to efficient parasitization. 8. At the same time the observation recorded in (7) was paralleled in Hawaii by the appearance of another lamellicorn root-eater, Anomala sp. In this case the introduction was from Japan, and was not connected with cane importations. Similarly also, the pest was barely recognised as present in Japan.?2 g. About 1901 a long-continued borer epidemic began in Brittsh Guiana.“ This was caused by the “large” or “ giant’”’ moth borer, Castnia licus. In distinction to some of the other epidemics recorded, this was caused by an indigenous pest. The habitat of this insect is from Central America to the Amazon, and previously it had only been recorded as feeding on the roots of certain orchids near the upper Orinoco. For some obscure reason it suddenly developed the habit of attacking cane. THE ‘“‘ NATURAL CAUSES” AND ‘‘ NATURAL CONTROL ”’ OF INSECT EPIDEMICS. The rate at which insects multiply is very great, a single female producing several hundred eggs. Unless there were some controlling factor limiting the increase of insects agriculture would be impossible. The most important one is to be found in parasitism, whereby one insect, a crop predator for example, acts as the host for a parasite which lives on and destroys its host. In this way a “ natural balance ”’ is maintained. This observation offers an explanation of the cause and course of insect epidemics. In the first place an insect with predaceous habits is introduced into a district and arrives there unaccompanied by the parasites which restrain its developments in its original habitat. Its multiplication now be- comes so rapid that in a short time an intense insect epidemic occurs. Gener- ally when discussing introductions two distinct conditions may be recognised. The locality of introduction may be continental, in which case there is likely to be a very ample local fauna, which may contain insects parasitic on the introduced species, or insects which in a short period of time may develop the faculty of parasitization. In this case a severe epidemic is unlikely, or the introduction may even pass unnoticed. This statement is not, however, to be construed as implying that insect damage may not be great in a continental area. In British THE PESTS AND DISEASES OF THE CANE 147 « Guiana, for example, the “ moth borer,” though severely parasitized, an- nually causes great damage, and up to the present no parasite has been re- corded as controlling the “large moth borer”’ there present and an indigenous species. Similarly, the island of Trinidad, which from its proximity to the mainland is rather of the continental than the insular type, has suffered very severely from an epidemic of the cercopid “ frog hopper,” Tomaspis posticata, The second condition obtains in islands remote from the mainland which generally possess a very restricted fauna. As instances of such dis- tricts may be cited the Hawaiian Archipelago and the islands of Mauritius -and Bourbon. The more remote West Indian islands would also fall into this category, while the islands of Cuba and Java, from their proximity to the mainland, would be more of the continental type. Under the second condition the introduction of predatory insects is likely to cause a severe epidemic and several such have been quoted in a previous section. These epidemics may be regarded as caused by the disturbance of the “ natural balance.” When a crop becomes subjected to insect damage, periods of greater and of less incidence are observed. This observation also follows a natural cycle. At one period the pest may be present in great numbers. The parasite, if present, then has unrestricted opportunity to carry out its life work, and the epidemic period is followed by the partial disappearance of the pest. The parasite now has less material on which to work so that its numbers tend to decrease, and consequently the pest again appears in quantity. The incidence of the pest will also be controlled by seasonal variation, some seasons being favourable to the development of the pest and some to that of the parasite. The matter is further complicated by the presence of hyperparasites, which have the same relation to the parasite that the parasite has to its host. As instances of parasitization and of hyperparasitization, the observations of Ulrich*® in Mexico may be quoted. He there found that the frog hopper, Tomaspis posticata, was attacked by a reduviid bug, Castolus plagiaticollis, the eggs of the bug being parasitized by a hymenopteron, Telenomus sp. Similarly in Fiji the efficiency of the introduced tachinid parasite of the beetle borer was found by Illingworth*é to be depreciated by the presence of an ant, Pheidole megacephala, which acted as a predator on the fly. Occasionally instances are observed where a factor is inimical to both host and parasite ; such a combination is recorded by Ritchie,*” who, in the West Indies, observed ants preying both on the “ cane fly,”’ Delphax saccharivora, and on its syrphid parasite. In addition to the parasitization of insect by insect, various fungi have been observed to attack and thus to control insects. The effectiveness of this control does not yet seem to have been worked out. Speare*® has made a study of parasitic fungi affecting various pests, and has recorded the presence of Entomophthora pseudococci and Aspergillus parasiticus on the mealy bug, Pseudococcus sp.; of the green muscardine fungus, Metarrhizium anisoplia on the Hawaiian beetle borer; and of Cordyceps sp. on the leat hopper. The green muscardine fungus appears to be of very wide distribution, and it has been specially studied by Rorer*® in connection with the frog hopper in Trinidad, where it has been artificially grown on the large scale and distributed over infected areas. Similarly Cordyceps is also widely distributed, and it has been recorded on the caterpillar of the West Indian 148 CHAPTER IX moth borer. A species of Botrytis is known to cause the death of the cater- pillars of Psalis securus in Java, and a scale louse, Aleyrodes longicornis, attacking fruit trees in Florida and also known as a cane pest, is attacked by a fungus, Aschersonta aleyrodis.°° Ritchie also records the very effective control exerted by Fusarium sp. on the cane fly in Jamaica.4” The recognition of the natural balance suggested the means whereby insect epidemics can be placed under control by the introduction and en- couragement of the parasite or natural enemies of the pest. The credit for the recognition of this means, and also for its successful operation is due in the first place to Koebele,>4 who used it with pronounced success in controlling scale insects on fruit trees in California. In this instance the chief pests were various coccids, one of the most dangerous being the white scale, Icerva purchast. This was brought under control by the intro- duction from Australia of a lady-bird predator, Vedalia cardinalis. Koebele- afterwards became connected with the Hawaiian Sugar Planters’ Association and associated with Perkins, Craw, Swezey, Kirkaldy and Muir, who were also employed by the Association. About 1900 a serious epidemic of leaf hopper broke out in Hawaii. It was recognised that the introduction was from Australia, and expeditions were soon despatched there. The parasites of the leaf hopper were found, collected, and imported to Hawaii under careful control. The result was that in a short period the leaf hopper was very materially diminished in number. Of the numerous parasites imported, the most effective were egg parasites, amongst these being three myramids, Paranagrus optabilis, P. perforator and Anagrus frequens. A chalcid, Oote- trastichus beatus, and a dryinid, Ecthrodelphax fairchildu, belonging to the local fauna, were also useful.?° The success which attended the natural control of the leaf hopper stimu- lated the Hawaiian Sugar Planters’ Association to attempt a similar control over the borer beetle, Rhabdocnemis (Sphenophorus) obscurus. This insect had been introduced into Hawaii, probably in 1854 along with the consign- ment of cane that had formed the parent stock of the Lahaina cane. By that time (1905) it had come to be looked upon as a necessary evil. Certain districts were more severely affected than others, the amount of damage done varying with season. The problem was to locate the original habitat of the borer, to ascertain its natural enemies, and to transport them to Hawaii unaccompanied by any hyperparasites which might be present. This task was assigned to Muir, who, starting his search in Southern China, finally located the borer beetle in Amboina (Lat. 8° S., Long. 125° E.) in 1908, and afterwards in New Guinea, where he established himself. As anticipated, the borer was found to be efficiently controlled, the parasite being a tachinid fly, Ceromasia sphenophori. The introduction of this parasite presented unexpected difficulties, and it was only after the establishment of intermediate breeding stations at Brisbane and Fiji that it reached Hawaii; once there it became rapidly established, and succeeded in effectively controlling its host, reducing the annual destruction of cane to a small figure.5? The two instances quoted above are those to which most attention has been attracted ; some others may, however, be noticed. In Ig10 an epidemic due to a beetle root-borer, Phytalus smithi, appeared in Mauritius.22 It was ascertained that the insect had existed almost unnoticed in the British West Indies, where it was effectively controlled by a scolid wasp, Tiphta parallela, which was then introduced into Mauritius. In this instance the importation had undoubtedly occurred along with some canes coming from Barbados. THE PESTS AND DISEASES OF THE CANE 149 A little Jater this observation was almost exactly paralleled in Hawaii, where a sudden localized epidemic due to the larva of another root-eating beetle, Anomala sp., broke out. In this case the importation was from Japan, but was not in cane consignments. An investigation in Japan located its parasite, Tiphia sp., which was successfully introduced into Hawaii. In this case again the presence of the pest was hardly known in its natural habitat. The introduction of the parasites of pests is not unattended by a certain amount of danger, as in some cases the parasite may itself become a pest, or it may attach itself to a new host, and in any case to obtain the maximum of effectiveness the parasite must be introduced without its hyperparasites if any such exist. In most of the cases recorded above the parasites were obligatory, that is to say they were so highly specialised that they depended for their life cycle on the host and on the host alone. Their introduction then was attended with no danger of the disturbance of the natural balance, but rather tended to re-establish it. The classical instance of the disturbance of the natural balance with lamentable effects is the introduction of the mungoose into Jamaica. This animal was so effective that not only did it destroy rats, but also attacked other animals, as well as poultry and birds. The result was a great increase in the number of ticks. The control agents mentioned above fall into two main classes, predators and egg-laying parasites. In the former class are to be included such controls as the lady-birds that devour the scale insects of Californian fruit trees. Birds are very useful in controlling the various “‘army”’ and “ grass ’’ worms, and the control of these in Hawaii is largely due to the importation of the “mynah”’ bird from India. In the West Indies swallows have been re- corded as keeping down the numbers of the cane fly, Delphax saccharivora. Amongst insect predators an elaterid has been observed preying on the larva of the moth borer in Cuba, and Muir also observed an elaterid destroying the grubs of the Hawaiian beetle borer. Ants also are valuable predators, but they have such a wide range of food habits that often they live on both pest and parasite. Generally predators fall far short of egg-laying parasites in effectiveness. These fall into two groups, egg parasites, and larval parasites. In the former class are to be found many minute hymenoptera, chiefly represented by chalcidids and myramids. In the latter class are to be found both hymenop- tera and diptera. The former are represented by small wasps, of which the scolids afford many examples. The latter contain many species of tachinid flies, which appear to be amongst the most valuable control factors. The egg parasites oviposit directly in the egg masses of their hosts. The scolid wasps usually sting their host in such a way as to paralyse, but not to kill it ; at the same time an egg is deposited in the body of the host, which forms the source of food of the parasite until it emerges as the perfect insect. The method of parasitization pursued by the tachinid fly, which controls the Hawaiian beetle borer is very remarkable. The fly, which is both oviparous and viviparous, oviposits at the entrance to a borer tunnel, and apparently locates the presence of a borer grub by the sense of smell, since it seldom oviposits at the entrance to an empty tunnel. The maggots on emergence find their way to the grub, the body of which they enter. The grub is not killed until it has finished completing its puparium, which is then used for the purpose of pupation by the parasite.*? 150 CHAPTER IX Equally remarkable is the method of parasitization observed by Swezey*® as followed by another tachinid, Chetogedia monticola, a control agent of the “ grass’ worms in Hawaii. This fly deposits on the leaves of the plant which forms the caterpillars’ food. The eggs thus laid are eaten by the host, and in their passage through its mandibles are cracked, permitting the escape of the maggots, which live in and on the body of the host, and eventually destroy it. Swezey also observed that if more than one egg was eaten by a caterpillar neither host nor parasite survived. The instinct of the fly seemed to recog- nise this, since it was observed to deposit but one egg on each leaf. In Plate XVI, No. 11, are shown the egg masses of Diatrea striatalis , the upper masses show freshly laid eggs and their appearance just before the emergence of the caterpillar ; below is indicated on the right their appear- ance when parasitized by the proctotrypid, Ceraphron beneficiens, and on the left when attacked by the chalcid, Chetosticha nana. The last-named. parasite is illustrated in Plate XVI, No. 12, and a highly enlarged view of a parasitized egg mass with the parasite fully developed is shown in No. 13. The very different egg mass of Scivpophaga intacta is shown in No. 14. All of these are after Van Deventer.*® The efficiency of the natural method of control has not passed unchal- lenged, and in particular the work of Koebele, Perkins and their associates in Hawaii has been criticised by Froggatt.54 He was inclined to attribute the diminution of the hopper to the burning of trash, a practice, however, that had been in use for many years before the advent of the hopper. In addition, the burning of trash is not advised by Perkins, since the hopper can escape by flight, while its parasites are unable to do so. Froggatt’s criticism was hypercriticised by Silvestri,®°° who wrote in the highest terms of the work of Koebele and of Perkins. Since then the control of the beetle borer by its natural enemies has been accomplished, and this feat reflects. equal credit on the entomologists who conceived the plan, on the explorer who executed it, and on the association which had sufficient faith in applied science to finance it. The Principal Pests and their Parasites——The number of insects attacking the cane and their parasites is very great, and the list is continually being added to. Below are catalogued a few of the more important pests and their parasites. Moth Borers (not including Castnia licus)—In Java hymenopterous egg parasites, Ceraphron beneficiens and Chetosticha nana. In British Guiana egg parasites, Chetosticha sp., Trichogamma nuinutum, Telenomus sp., and as a larval parasite a tachinid fly, Hypostema sp., a braconid wasp, Iphiaulax sp., and the fungus, Cordyceps barbert. Army Worms, Cut Worms, etc.—e.g., Spodoptera mauritia, Cirphis unt- puncta in Hawaii by birds, by tachinid flies as Chetogedia moniicola and by an ichneumon Ichnzumon koebeli. Lamphygma frugiperda in the West Indies by tachinid flies. All these are larval parasites. Root-eating Beetle Larve.—In Porto Rico, Lachnosterna sp. (May beetles) by a scolid wasp Tiphia inornata, by a tachinid fly Cryptomerigenta auri- facies, and by the green muscardine fungus Metarrhiziwm anisoplia. Inthe West Indies Phytalus smithi by a scolid Tiphia parallela ; Ligyrus rugiceps. (hardback) by a scolid Campsomeris dorsata ; Prepodes vittatus by a scolid THE PESTS AND DISEASES OF THE CANE “151 Elis atrata. In Hawaii Anomala sp. by a scolid Tiphia sp. In Australia Lepidiota albohirta (cane grub) by a scolid Dielis formosus. All the above are larval parasites except the fungus, which attacks the perfect insect. Beetle Borer —Rhabdocnemis obscurus by a tachinid Ceromasia sphe- nophort and by the green muscardine fungus. Hemiptera.-In Mauritius, Icerva seychellarum (pou-a-poche blanche) by a chalcidid. In Hawaii, Perkinstellia saccharicida (leaf hopper) by the myramid egg parasites, Paranagrus perforator, P. optabtlis and Anagrus frequens ; and in the perfect stage by a dryinid, Ecthrodelphax fairchildit, and by a chalcidid, Ootetrastichus beatus. In the West Indies, Delphax saccharivora (cane fly) by a myramid egg parasite Anagrus armaius, and in the perfect stage by a dryinid Strepstptera sp., by a fungus Fusarium sp., by ants, and by swallows. In Trinidad, Thomaspis posticata (frog-hopper) by a reduviid bug, Castolus plagiaticollis, by a chalcidid Oligosita giraultt, and by the green muscardine fungus. In Hawaii, Trechocorys calceolaria (mealy bug) by lady-bird predators and by the fungi Entomophthora pseudo- cocci and Aspergillus parasiticus. Other Methods of Control.—1. Use of Poisons.—The use of poisons is largely confined to the destruction of rats. The poisons that are most commonly employed are preparations of strychnine, arsenic, squills, phos- phorus, and barium. Bread grains, banana, and molasses are food media used to distribute the poisons. Leaf-eating caterpillars are to some extent controlled by the use of arsenicals, sold under the trade names of “ Paris Green” and “ London Purple.” These materials have been used in the campaign against the “giant”? moth borer in British Guiana. In Australia the injection of cyanide of potassium into the soil has been used to destroy the grub of the ““ srey back ”’ beetle Lepidiota albohirta. 2. Collection by Hand.—In districts where labour is cheap and plentiful, a diminution of insects is obtained by means of hand collection. In regard to the moth borer this collection takes the form of cutting out the “ dead hearts ”’ of the injured cane and the collection of the eggs laid on the leaves. The children of the Asiatic and negro labourers forming the bulk of the population of many estates can be easily trained to perform this task. It . is important that they be taught to recognise the difference between para- sitized and sound eggs, and this they readily do. Further, when paid by results they have been known to collect and substitute the egg masses of other insects. Zehntner in Java recommended that the collected. eggs should be placed on trays surrounded by a layer of molasses, which would prevent the escape of the caterpillar, but allow the parasite, which emerges as a perfect insect, to fly away. The night-flying coleoptera and lepidoptera may be captured by exposing lamps in infected areas. For the capture of the wawalan beetles, A pogonia destructor, Zehntner devised the trap shown in Fig. 45, which is exposed under a lamp during the period of their nuptial flights. Exceptionally, as in the case of the slow-flying diurnal, Castnia cus, the perfect insect may be caught in quantity in nets. The employment of bait as a means of attracting insects was once used in the Hawaiian Islands, and Koebele*! has recorded that with sour cane and with the help of seven little Indian girls in Fiji he has collected 16,000 beetles in four hours, and 152 CHAPTER IX that by means of systematic collection over three years the pest nearly disappeared. Similarly, S. M. Hadi%’ has recorded that in India the white ant is attracted by dung, which is purposely placed on the canefields. 3. Rotation of Crops——This is recommended by Watson as likely to diminish the prevalence of the root borer, Diaprepes abbreviatus, and amongst crops not attacked he mentions ochra, yams, eddoes, woolly pyrrol, pigeon pea, bonavist bean, and rouncival beans. 4. Use of Insecticide Washes.—The great area of plantations prevents the utilization of this means, which is necessarily confined to orchards and similar industries where the crop is produced under intensive rather than under extensive conditions. 5. Flooding.—The flooding of fields has been used to destroy such insects as are of subterranean habit in part of their existence, such as the “large? moth borer, Castnia licus. 6. Destruction of Breeding Places —Whenever possible this method is cne of great effectiveness, and it is applied on an extensive scale in the campaigns carried out against the mosquito and other disease carriers. In the Hawaiian Islands, also, systematic measures are taken to destroy the eggs of the sarcophagid flies which breed in latrines, and which are associated with the spread of typhoid and other intestinal diseases. While not directly connected with growing cane, attention to such matters has an important economic bearing as affecting the health and efficiency of the population of an estate. In regard to sugar cane insects, the matter is complicated by a number of factors. Guilding,4! whose remarks are quoted below, in 1834 advised trashing as a means of reducing the numbers of the moth borer, but other factors have to be considered, and often the limited labour supply will prevent anything of this nature. Uncontrollable local conditions may also be a factor aiding the unre- stricted development of a pest. Such a condition is discussed by Walcott*® as obtaining in British Guiana, where, owing to climatic conditions, cane in all stages of growth is to be found in juxtaposition. There is thus a constant habitat of young cane, which is preferred by the borer for ovi- positing. Quelch®* has made suggestion that this state of affairs might be remedied by planting areas of large units separated by distances greater than the normal range of flight of the borer. we THE PESTS AND DISEASES OF THE CANE 153 Of a different nature are the conditions observed by Walcott** in Trinidad in connection with the froghopper. He noted the ill-kept conditions of the fields and the large areas of grass-grown land in close proximity to the canefields. Regarding the froghopper as originally feeding on grass he considers these areas as foci of infection. These observations recall the comments made by Guilding™ in 1834 in reference to the moth borer :— “Those animals which the Creator has thought fit to form and preserve for ages man will not be permitted to exterminate; we may, however, with propriety, strive, and by all means in our power, to lessen the number of those creatures which injure or destroy our property. Those animals, when they assail us in moderate numbers, act only as a stimulus, wisely sent to arouse the inattentive planter to cleaner and more careful modes of husbandry. When they swarm so as to deprive him of his crops, the loss must be in future attributed either to his obstinacy or to his negligence.”’ A number of years ago the advice was very frequently given that the burning of trash would destroy the breeding places and at the same time the pests themselves. It is now recognised that this advice is bad. Perkins?® in particular has shown that the leaf hopper is able to escape by flight, but that many of its parasites fail to do so. Similarly, and for the same reason, Van Dine*’ attributes the comparative freedom of Cuba from insect damage to the practice of cutting without burning, and of leaving the trash to rot on the land, as compared with the opposite custom in Porto Rico, where the damage is much greater. 7. Culttvation.—In the case of root eating grubs, ploughing at the appro- priate season will result in bringing many to the surface, where they may be eaten by birds, including domestic poultry. Such a scheme is followed in the control of the cane grub in Australia, and in India in connection with a grasshopper, Hieroglyphus frucifer. 8. Quarantine of Imported Plant Material—rThe instances already quoted show how great may be the danger of an unrestricted importation of cane. The Territorial Government of Hawaii established a system of inspection a number of years ago, and the Federal Government of the United States has absolutely prohibited the importation of cane. To a certain extent so stringent a ruling is to be deprecated since a district may wish to obtain a new and valuable variety. While the uncontrolled im- portation of cane is to be unreservedly condemned, the danger of importing, under rigid inspection and isolated and protected propagation, the single cutting necessary to establish a variety reaches the vanishing point. 9. Infection with Disease —A number of years ago it was proposed to destroy rats by means of cultures of organisms producing specific rat diseases. One of the most widely used preparations was Dansyz virus, but the results have been contradictory. 1o. Encouragement of Natural Enemtes.—This heading is really included under the term “ natural control,’’ which is, however, restricted more or Jess to specialized parasitization. The natural enemies of insect life include birds, lizards, toads, newts, lady-birds and spiders. Amongst the natural enemies of rats should be included snakes, and their beneficial action on a sugar plantation was noted by Dutréne as early as 1790. 154 CHAPTER IX CANE DISEASES. The sugar cane, in common with other cultivated plants, is subject to a number of diseases. The great majority of these are known to be due to certain specific fungi, but in one case, the gumming disease, the causal organism is a bacillus. In a number of cases the causal organism is specific to the cane, that is to say it has been observed as parasitic on the cane and on no other plant. In other cases, as in the pineapple disease and the root disease, other plants may act as hosts. An interesting point in regard to cane diseases is the very wide distri- bution of one and the same organism, as instanced by the red rot of the stem (Colletotrichum falcatum) known to occur in Java, British India, the West Indies, Louisiana and Hawaii, and in the gumming disease known to occur in Brazil, Argentina, Madeira, Mauritius and Australia. This wide distribution can best be attributed to the uncontrolled importa- tion which has taken place in past times. In the case of the gumming disease, certain facts on record are suggestive, though not positive. This disease was first described by Dranert®* in 1869 as prevalent ‘in Brazil. At this very time importations of Brazilian canes were made to Mauritius, and from Mauritius there have been frequent exportations to Australia. It is in these three widely separated localities that gumming is known as a dangerous disease. On the other hand it is sometimes possible to specify the period of in- fection, as instanced by the introduction of Iliau to Louisiana®® along with canes sent from Hawaii, and of the Australian leaf-splitting disease to For- mosa.®® But perhaps the most suggestive illustration is that connected with the outbreak of the yellow stripe disease in Porto Rico in 1916. Pre- viously yellow stripe had been known as a pathological condition in Java and in Hawaii, but had not been recognised as an infectious disease. About IgIo certain approved Java seedlings were imported into Egypt, thence they went to Argentina, and from there they were brought to Porto Rico in 1gr4. In no one of these localities had yellow stripe been recorded before, but in each, shortly after the introduction, the disease was recognised, and in 1916 it assumed a dangerous epidemic form in Porto Rico, becoming also known there as the Mosaic or Mottling disease. The history of the sugar cane is associated ath a number of epidemics of disease. The earliest of which any record exists is that which occurred in Mauritius and Réunion in the years 1848-51,®! and which forms one of the links made use of by Darwin in building up his theory. The cane affected was the original stock introduced by Bougainville from Otaheite, and the disease was characterized by a “‘ corkscrewing’”’ of the top and a yellowing off. At the time it was attributed to degenerescence, and it was observed that the degenerescence had been noticeable for fifteen years before the fulminant outbreak. Second in sequence is the epidemic of gumming, which appeared in Brazil as early as 1857, and was very prevalent in 1865 ; the variety mainly affected was the Cayenne or Otaheite cane. Gumming was also responsible for an epidemic in Madeira in 1885, and again appeared in a fulminant form in Mauritius in the ’nineties. Here again the cane most affected was the Louzier, which probably represents a second establishment of the Otaheite stock. Third in chronological order is the epidemic which became serious in Porto Rico in 1872, causing the THE PESTS AND DISEASES OF THE CANE 155 elimination of the Cana blanca, or Otaheite cane. An extant account of the disease by Stahl describes what appears to be top rot as a dominant symptom. In 1876 an epidemic described as ‘‘rust’ did great damage in Australia and Natal in the eighties also suffered severely from some undescribed disease. The two epidemics most often referred to are the sereh disease of Java, which appeared about 1890, and resulted in the nearly complete disappear- ance of the Cheribon cane ; and the rind fungus of the British West Indies, prevalent at the same time, and which, as in many other cases, selected for attack the Otaheite (Bourbon) cane. These last two epidemics had some good effect, as they afforded great stimulus to the propagation of seedling canes. Yet another instance of the susceptibility of the Otaheite cane to disease may be found in its early disappearance from the Island of Hawaii, and to its present sickness in the other islands of that archipelago. The latest instance of an epidemic is to be found in Porto Rico, where in 1916 the Yellow Stripe disease but recently imported there assumed a fulminant form. / Degenerescence is often given as a cause of these epidemics, but the writer in the position of a layman regards the explanation as unrational. What is in all probability one and the same cane (Otaheite) has been the subject of most of the epidemics referred to above. During the time 1848-51 that the first Mauritius epidemic occurred, this cane was flourishing in the West Indies, and a few years later was introduced to the Hawaiian Islands with remarkable success. Excepting the possible presence of adventitious seedling descendants, each and every cane then growing must have been the progeny in unbroken asexual descent of one cane, which probably originated as a seedling in some island of Polynesia, probably Otaheite, and, to go further, all the then existing canes may be regarded strictly as one and the same individual. Looked at in this light, degeneration as the result of age, or as the result of continued propagation from cuttings, appears ill-founded, and the epidemics were more likely to have been due to improper agriculture leading to harmful soil conditions, combined possibly with the development of an organism or organisms of a virulent strain due to long-continued access when the cane once formed the sole crop of a locality. Leaf and Leat-Sheath Diseases.—No one of the fungi that attack the leaf is to be considered as a major disease. Notwithstanding, the sum total of the damage done by the immobilization of some portion of leaf surface must annually reach avery large sum. Most of the diseases that have been described in the literature are referred to below. Yellow Spot.®"—Cercospora Kopkei (Kriiger) ; Maculis amphigenis, sinuosis, confiuentibus, purpureo brunneis, infra pallidioribus, margine concolori ; hyphis plerum- que hypophyllis fasciculatis, septatis, apice nodulosis, denticulatisque fumoso brunneis, 40-50X7, conidits fusoideis, subrectis, 20-30 X 5-8 medie 40 X 6 utrinque obtusiusculis, 3-4 septatis, non constrictis, passim guttulatis, subhyalinis. The disease appears as dirty yellow spots, often meeting to form one irregular blotch. A brown mycelium is found on the leaf, the branches of which, sometimes isolated, sometimes united in bundles, carry colourless spores (Fig. 46) ; the appearance of the underside of the leaf is as if covered with a white dust. It is only reported from Java. 156 CHAPTER IX Eve Spot.8® Cercospora sacchari (Van Breda de Haan).—Hab. in foliis, que maculantur, sacchari officinarum. Hyphe pluriseptate, brune@, 120-60; conidia 60-80 X 9-12, vermicularia, 5-8 septata, brunea. The spores of this fungus, after Cobb, are shown in Fig. 47. The presence of this disease is indicated by small red dots, which grow into long elliptical dark red spots, with a light yellow margin; at a later stage the centre be- comes a dull dead yellow, surrounded by a dark red area, and this is circum- scribed by a bright yellow border ; the elongated elliptical shape a of the spots, which may grow Fo up to 1} to 2 inches in length, is retained; the appearance They identified the organism on these canes as Comniothyrium melasporum, attributing the disease to the most prominent characteristic. Another description is due to Ellis and Everhard®® in Jamaica, who named the organism Trullula sacchari. About 1890, the cane known in the British West Indies as Bourbon became very sick, and this sickness received the name of Rind Disease. It is thus described in the Kew Bulletin :—1°° “Canes infected with rind fungus are first noticed by dark red or brown patches in one or two joints toward the middle or base of the cane. The red patch, having made its appearance, rapidly spreads upwards and downwards, the infected area darkens in appearance, and is evidently rotten. Little black specks make their appearance between the joints, breaking from the inside to the surface.” Another feature of the disease was that it only manifested itself in ripe cane shortly before harvest. Large areas ready for the cutlass would die and dry up in a few weeks, presenting the peculiar lesions. This condition was investigated at Kew by Massee, who ascribed the sickness to the most prominent characteristic, naming the fungus T7ichospheria sacchari” After the establishment of the Imperial Department of Agriculture for the West Indies, the cause of the sickness was examined on the spot by Howard.1° He found two fungi on diseased cane, both of which he grew in pure culture. One of these was the Colletotrichum falcatum, associated with the red rot of the stem, and the other was a fungus to which the black erumpent hyphz were due. This was only observed in the melanconium stage, and has since become known as Melanconium sacchari, By means THE PESTS AND DISEASES OF THE CANE 165 of inoculation experiments made in hot-houses in England with pure cultures of the Colletotrichum, Howard obtained lesions characteristic of some phases of the disease, with the absence, of course, of the black hyphe. In no case, however, did he obtain disease lesions or growth with inoculations of the Melanconium into healthy cane. When, however, the Melanconium was inoculated into canes already attacked by the Colletotrichum, growth followed with the appearance of the hyphe. Very shortly afterwards an outbreak of rind disease occurred at the Georgetown Botanical Gardens. Specimens of these canes were sent by Harrison and Jenman to Howard,1% and on them he found one fungus only, which he identified as Diplodia cacaotcola, known already as a parasite of the cacao tree. He showed that this fungus is an actual parasite capable of producing all the outward symptoms of rind disease when inoculated into healthy cane in pure culture. In his publication on this subject he also brings forward evidence to show that Darlucca melasporum = Strumella sacchart = Coniothyrium melas- porum = Diplodia cacaoicola, and that the fungus on the Mauritian canes suffering from the Maladie de la Gomme was actually the Melanconium fungus. More recently the perfect stage of the Diplodia has been obtained by Bancroft and named by him Thyridaria tarda.%” On the other hand Johnston considers the Darlucca, Strumella and Contothyrium as the same as the Melanconium. Butler has also studied the D. cacaoicola in India as the cause of dry rot of the sugar cane. He regards the organism there as only mildly parasitic. A third rind fungus, Cytospora sacchari™ has been observed by Butle1 as parasitic on the cane in India, and later was found to be present also in the West Indies. Two other fungi, Melanconium saccharinum®’* and Nectria laurentiana®® are known to occur on the rind. Finally it may be mentioned that the macroscopic appearance of canes affected by Gnomonia iliau sometimes somewhat simulates that of rind disease. Whether the Melanconium fungus is to be regarded as strictly sapro- phytic still remains in doubt. Cobb*! in Australia took the view expressed injthe following quotation :— “TI believe that it is true in most cases, if not in ali, this fungus requires the cane to be injured. Perhaps the frost so injures the arrow of the cane as to cause it to decay or die; perhaps a borer makes its way into the cane, and thus breaks the rind; or again perhaps the wind twists the stalk and cracks it, or the cane gets injured in any of the numerous possible ways; then the fungus stands ever ready to take advantage of the accident, and in a few weeks’ time makes such inroads as to send the whole cane well on the way to decay. ... . - The amount of damage done by spume is very difficult to estimate, There is no doubt that through its agency much cane, which otherwise would be saleable, is soon rendered worthless.”’ Afterwards, in Hawaii, he considered the organisms as distinctly parasitic, and to it he ascribed the frequent non-germination of cuttings. Lewton- Brain! also treats the fungus as parasitic, and indicates that although the hard outer rind is protective the fungus may enter through a wound, and in the case of a susceptible variety may bring about the death of the stalk. 166 CHAPTER IX The latest observations have been made by Stevenson in Porto Rico, and he seems to consider it parasitic under certain conditions, such as when the cane is weakened by drought or by excessive rainfall. He also observed the continual presence of the fungus on the leaf sheath, and a greater Daye eros incidence on old cane and on young cane in : > fields of old ratoons. é Summing up these apparently contradic- tory observations, it may be said: x. Rind fungus is a condition associated with diseased, dying and dead cane, characterized by the appearance on the stalk of black erumpent hyphe. 2. This condition inay be caused (a) by a single fungus, Diplodia cacaoicola, also described under various other names: (3) by the conjoint action of the Colletotrichum fal- catum and the Melanconium sacchari. In this case the Colletotrichum lives in the interior pith, its action being localized by the protective action of the nodes to the infected joint. The Melanconium fungus entering the infected joint subsequently attacks the fibrovascular system, and shutting off the water supply causes the rapid death of the cane. 3. The mass of evidence indicates the non- parasitic nature of the Melanconium, though perhaps under certain con- ditions it may become an active parasite. 4. The exact causal agent of the past historic epidemics cannot now be exactly determined. The technical descriptions of these fungi follow :— Melanconium sacchari (Massee).—Conidia produced in pycnidia formed under the epidermis, unicellular, pale brown, cylindrical, straight or slightly curved. 14-15 < 3*5-4 microns. Figs. 64 and 65 show a cane affected by this fungus, and the appearance of the spores. Melanconium saccharinum (Penzig and Saccardo).—-100 X I2 microns ; para- physes 100-130 microns long, abundant, filiform ; ascospores monostichous, oblong, fuliginous, triseptate, slightly constricted at the septa, 19-20 X 6—7 microns. Figs. 66 and 67 show, after Butler, a piece of cane infected with this disease and also the Diplodia spores. Cytospora sacchari (Butler).—Stromatibus verruciformibus, seriatim ordinatis subcutaneo-erumpentibus, pluri-locularibus, nigris, osteolo elongato, singulo, rarius duobus preditis; sporulis minutissimis, cylindraceis curvulis, utrinque obtusis ; 3°5X1I:5 microns; basidiis ramosis, septatis, 12-18 microns. Hab. in culmis vaginisque sacchari officinarum India. THE PESTS AND DISEASES OF THE CANE 167 Figs. 68 and 69 show, after Butler, a piece of cane infected with this disease and also the-spores. Nectria laurentiana (Marchal) —Stroma somewhat broad, convex, superficial I-2 m.m. diam. seated on a hyaline slender cottony, evanescent, at first free, later confluent white parenchyma ; perithecia densely cespitose, globose or ovoid, 2 50-350 microns diam., strongly rugulose, even subsquamulate, ferruginous, glabrous, ostiole slightly dark, somewhat broad, membranaceous ; asci, 8-spored, oblong cylindrical, at lower end subsessile 60—70 x 7-8 microns ; aparaphysate ; spores in one series, oblong, equal-sided straight, at bottom end obtuse acute, 2-celled, constricted in the middle, rarely the lower end somewhat narrower; 12-13 X4*5—-5 microns, epispore rarely subasperulate. Diseases classed as Pathological Conditions—Specific organisms have not been connected with two of the most important of cane diseases, as is Fic. 67 244, o%e x 580. Fic. 68 Natural Size Natural Size Fic. 66 Fic. 69 also the case with “top rot,’ already described. The two conditions described below are known as “sereh”’ and as the “‘ yellow stripe disease.” Sereh.—This disease was first recognised as such in 1882 in Java, where it has done much harm. In the typical form of sereh the stool of cane consists of a number of short stalks with very short joints; the buds, especially those below, sprout, whereby results a bundle of short stems hidden in a mass of leaves. The whole stool bears a resemblance to lemon grass ‘Andropogon schenanthus), the Javanese term for which is “‘sereh.”’ In a second type one or two stalks may grow to a fair size, with very many short joints in the upper part. Above all is a fan-shaped crown. Many of the eyes, especially those below, sprout and form small branches. Benecke?® has given the following symptoms of the disease :— 1. A low, shrubby growth, often only from 3—4 centimetres. 2. A fan-shaped arrangement of the leaves arising from a shortening of the internodes. 3. The internodes are only from a half to two-thirds of an inch Jong. 4. The nodes are tinted red. 5. Numerous aerial roots are formed, 168 CHAPTER IX 6. The fibrovascular bundles are tinted red. 7. Subterraneous outbranchings are formed, 8. The sheath and root buds turn vermilion. g. In some cases there is no formation of wax on the stem. 10. The growing part of the stalk is frequently dyed red. Iz. The leaf sheath and stalk stick together. 12. There is an accumulation of secondary organisms. The presence of gum in sereh is a point about which much has been written. The major portion of opinion seems to be that the presence of gum is a consequence of and not directly connected with the disease, since, if the gum is of bacterial origin, the growth of the bacteria might only take place in cane already weakened by disease. A red coloration of the fibrovascular bundles is a characteristic of sereh. This coloration is most pronounced at the node, but often ap- pears in the internode as a red stripe.* This appearance is quite distinct from the red patch with white centre characteristic of the red rot of the stem. The very large amount of work that has been done on sereh has up to the present failed to elucidate the cause of the disease, unless the identification by Wolzogen-Kithr with gumming is confirmed. Opinion is divided in ascribing the cause to physiological and to pathological causes. Amongst the first named have been suggested bad drainage, injudicious manuring, late planting, excessive ratoonage, an insufficiency of silica in the soil and degenerescence. As regards parasites, Treub!°* ascribed the disease to the attacks of a nematode worm, which he named Heterodera javanica. Coinciding with the attacks of the worm he observed the presence of a fungus of the genus Pythium. Treub believed that the nematode penetrated the bark of the root at places of accidental injury or at the growing point, After having arrived within the root the worm worked its way parallel to the central axis until it arrived at the point of growth of a lateral root. Soltwedel!®’ also attributed the damage to attacks of a worm, which he named Tylenchus sacchari, stating that the parasite passed its existence in the root, which it destroyed. The connection between sereh and nematode worms is not now accepted. Janse!°8 ascribed the cause of sereh to two organisms, Bacillus sacchart and Bacillus glange, and stated that these organisms attack plants other than the cane. He considered that the seat of the disease lay in the red- coloured fibrovascular bundles. The dependency of sereh on these organ- isms is not now accepted. Went?°9 considered sereh as a combined leaf sheath and root disease caused by an organism Hypochrea sacchari, the description of which is as follows :— Pulvinata, deinde depressa, carnosa, pallide fusca, stromatibus 2-4 m.m. lat. I m.m. crassis, saepe leviter collascentibus, intus pallentibus vel albidis, peritheciis fuscis, ostiolis vix prominulis, 200-500 X 150-200, ascis linearibus breve pedicellatis, 100 X 5, sporidiis monostichis 8, e cellulis duabus inzwqualibus, mox decedentibus compositis, cellula superiori globosa 4 diam., cellula inferiori cuboidea oblonga 6 x 4, fumose olivaceis. Conidiis = Verticillium sacchari. In Fig. 70 is shown, after Went, an ascus of the Hypocrea containing eight spores. * A red striping of the sugar cane associated with the presence of gum has also been described by Greig Smith in Australia. This he ascribed to the association of an unidentified ascomycete with a slime-producing bacillus, to which he gave the name of Bacillus pseudarabinus, THE PESTS AND DISEASES OF THE CANE 169 As with the cther causes the connection of this fungus is not accepted, and the general opinion seems to be that sereh is the manifestation of peculiar soil and cultural conditions, the organisms which have been observed only becoming prominent after the health of the cane has been affected. However, the very latest Java studies indicate that a connection may exist between sereh, gumming and yellow stripe. The infectious nature of the condition is uncertain. The disease spreads from district to district in Java, and on the other hand healthy stalks planted in an infected field remained healthy. Whether infectious or not the disease was found to be passed on from plant to plant, that is to say sound seed gave sound canes, while seed from sereh-infected canes gave sereh-infected stalks. The lccalization of the disease or not in Java is of great interest. It has been recognised definitely in Malacca, Bangkok and Borneo, and references to canes with the appearance of sereh in India, Australia, Mauritius, Porto Rico, Hawaii and Trinidad are to be found in the literature. Went observed canes in Surinam with all the symptoms of sereh, and noticed at the same time the presence of the Hypocrea, but in no instance outside of Java have the manifestations reached the epidemic stage, re- maining rather as isolated instances in individual canes. Yellow Stripe, Mottling Disease, or Mosaic Disease.—This is a condition which was first studied in Java. Lately (1916) the condition has reached the epidemic stage in Porto Rico,"° and it is not unknown in Hawaii, Louisiana and Argentina. Canes presenting all the symptoms of yellow stripe may also be found in Cuba. The manifestations present themselves most con- spicuously in the leaf, which, when viewed by transmitted light, presents a peculiar mosaic 01 mottled appearance due to spots of yellow colour. In cases of severe attack the spots coalesce to give the appearance of a yellow stripe. At the same time the joints of the cane exhibit a shrinkage, with the eventual] ap- pearance of graycankers. Accompanying the manifestation is a diminution of the weight of the crop, but there is no decrease in the sugar in the affected portions. These results naturally follow on the immobilization of a portion of the leaf surface. The disease is progressive in that ratoon cane is more infected than is plant cane, and it is also hereditary, cuttings from infected cane transmitting the condition, and in this observation lies one of the means of control. Although no or- ganism has yet been associated with the condition, it has been established that the disease is infectious. The latest view is that Mosaic is transmitted by sucking insects. Chlorosis.—Under certain conditions canes develop yellow stripes in the leaves due to absence of chlorophyll, and as a condition quite distinct from that described above. This condition occurs in soils containing a large quantity of calcium carbonate, and has been observed in Antigua, Barbados, Jamaica, Cuba and Porto Rico, where it has been studied as a serious con- dition by Giles and Ageton.4! The condition is due to disturbance of the physiological functions of the plant, and may be temporarily remedied by applications of sulphate of iron to the leaf or to the soil. Areas in which it occurs are known in Antigua as. gall patches or moonstruck canes, and 170 CHAPTER IX Tempany!? has brought forward evidence to show that the condition is due to the combined action of chalk in the soil with sodium chloride carried to the surface from deep-level waters. This observation explains the dependence of the condition on season and the lack of correlation between quantity of limestone present and severity of attack. The Control of Fungus Diseases.—The various methods by means of which fungous diseases may be controlled are discussed below. 1. By the Selection of Immune Varieties —Of all the means available this is the most elegant, and, since the recognition of the fertility of the cane seed, a great part of the time of experiment stations has been devoted to this end. Organized cane breeding had its inception in Java, where the appearance of the sereh disease provided the stimulus. The pioneer in this work was Kobus, and he succeeded in obtaining a number of varieties which showed a high degree of resistance. In the British West Indies and in British Guiana also, Harrison and other workers have obtained canes that served to replace the older standard variety (Bourbon or Otaheite), which before 1890 had become subject to the rind disease. In cases of other epidemics, varieties already existing have served as substitutes for the infected variety. A complete survey of immunity as it affects the cane remains to be made, but certain isolated observations may be put on record. The Otaheite cane (q.v.), one of the most desirable of all varieties, is also one which is very susceptible to disease, and has been the subject of several epidemics. From the time of its introduction into Mauritius by Bou- gainville till 1840 it formed the principal cane grown. It then became subject to an epidemic which at this space of time it is impossible to identify. Relief in this case was obtained by growing the Black Java cane, known in Mauritius as Belouguet. What is probably the same cane as the Otaheite was again extensively grown in Mauritius twenty years later as Louzier, and about 1890 this cane suffered from some disease. In this case relief was obtained by planting the White Tanna variety. In the British West Indies the Otaheite cane was grown almost exclusively from 1800 onwards, and about 1880 the first symptoms of the epidemic that became known as the rind disease (q.v.) were noticed. Resource was had to the White Transparent cane, and to seedlings as they were developed, and, though still grown, the Otaheite or Bourbon cane has never recovered its former position. Again in Pernam- buco this cane suffered very severely in the ’sixties and the ’nineties from the gumming disease, which also attacked it in Cayenne in 1859. This variety has also been grown and attacked by disease in Madeira, Natal, and the island of Hawaii. More recently it has begun to fail in the other islands of the Hawaiian archipelago, where as Lahaina it had such a wonderful record. This failure seems, however, due to soil conditions rather than to a definite disease. Erwin Smith®? failed to infect the variety D 74 with inoculations of Pseudomonas vascularum to which gumming in other varieties is due. The variety B208 has been observed in the West Indies to be very susceptible to root disease. Butler has observed that the reed-like canes of India are more susceptible to “‘smut’’ and more resistant to “‘ red rot’ than are the Paunda canes. The cane H 333 possessed of otherwise very desirable qualities was found in Hawaii to be so susceptible to the leaf-disease ‘‘ eye spot,’’ caused by Cercospora sacchari, that the stem was affected, and the whole cane killed. THE PESTS AND DISEASES OF THE CANE 171 The Uba (Kavangire) cane in Porto Rico has been found to be quite immune to yellow stripe. The reed-like canes of British India, e.g., Chunnee, were found to be immune to sereh, and were hence used as a parent in the early seedling work of Kobus. 2. Plant Hygiene—Employ on the plantation only those methods of agriculture that tend to give a healthy condition to the plant. It is highly probable that many of the organisms connected with cane diseases are only weakly parasitic, and only become active when the plant is weakened by negligent agriculture. The remarks of Harrison!® on this point are well - worth quoting :— ‘““T have personally never favoured the readiness so apparent of late years to refer almost every instance of decreased yield in cultivated plants to the noxious action of microbes or fungi. It appears to me for a long time back we have in the tropics rather neglected what I may call the physical and chemical hygiene of our cultivated soils, and have not paid sufficient attention to the soil conditions which may have materially reduced the naturally resistant powers of plants to the attacks of bacteria and fungi. And, further, I think that the susceptibility of certain kinds of plants, for instance the Bourbon cane, to injury by drought and fungus attacks is due in part at least to the defective conditions of soil hygiene, under which in places they are now cultivated.”’ 3. Rotation of Crops.—It is highly probable that many of the cane epidemics have been aided by the wide-spread custom of growing cane continuously on the same soil. In this way the causal organism has a con- tinuous habitat, and, being afforded opportunity for indefinite increase, may in time develop a strain of intensified virulence. When other plants are grown in rotation there is a period over which there is an absence of the host plant, when the fungus must tend to disappear in quantity, and more especially when it is an obligatory parasite of the host. It would appear that it is the fungi causing the various “ root ’’ diseases that would be most affected by this method of control, since in this case the soil itself becomes infected. As bearing on this is the observation that in the West Indies ratoon crops are known to be more liable to root disease than are plant crops. Apart from a rotation of crops a rotation of varieties might be utilised since the susceptibility of different varieties towards diseases varies widely. It may also be called to mind that wheat grown continuously at Rothamsted has shown itself much more liable to disease than when rota- tions were practised. 4. Use of Healthy Seed —This end can be obtained by careful selection, by growing seed cane in nurseries remote from infected areas, or by using, as seed, cane from parts of a plantation not affected. In Java, for example, it was found that cane grown in mountain districts and used as seed gave a certain degree of immunity to sereh, and an industry independent oi the plantations proper has developed. It has also been found that the yellow stripe disease is hereditary, and may be controlled by the use of selected disease-free cuttings. As this disease is more of the nature of a pathological condition than a disease due toa specific organism, the method in this case would amount more to the selection of an immune strain. It would also be reasonable to hope that the continued selection of cuttings free from the causal organism ofany disease might give an immune strain, as the healthiness of the particular cutting might in itself be due to immunity. 172 CHAPTER IX 5. Use of Fungicide Washes on the Seed.—The exposed ends of cane cuttings form a most convenient point of entry for fungus spores, particularly for those of Thielaviopsis paradoxa causing the pineapple disease, and it is this organism more than any other which is responsible for the non-germina- tion of cuttings. It has been shown by the experiments of Howard"4 in Barbados, and of Cobb in Hawaii, that soaking the cuttings in Bordeaux mixture preparatory to planting is a very efficient prophylaxis. Bordeaux mixture is prepared as follows :— Dissolve 6 lbs. crystallized copper sulphate in 25 gallons of water. Slake 4 Ibs. of quicklime in 25 gallons of water. Gradually add the quicklime to the copper solution, with constant stir- ring ; when completely added test the mixture by immersing in it for a few seconds a bright steel blade. If the blade becomes coated with a red deposit of copper more lime must be added. The time over which the cuttings should be left to soak is half an hour. In addition to the use of Bordeaux mixture, the protection of the cut ends with tar has been proposed. 6. Destruction of Disease Organisms.—This method is broadly included as an underlying cause for the benefits to be obtained from a crop rotation. As applied more directly, the recommendations of Howard, Lewton-Brain, and Cobb for the destruction of the various root fungi by the application of heavy dressings of quicklime may be quoted. A second widely recom- mended procedure is the destruction of dead cane and trash. This procedure is, however, economically unsound as a principle in agricultural economics, and may even be obnoxious, considered in relation to insect control. 7. Avoid all practices such as high trashing that tend to injure the cane. This advice has been made with regard to such organisms as obtain an entrance to the stem through wounds. 8. Inspect and quarantine all cane received from foreign countries, and if such are allowed to enter, restrict the importation to one or two cut- tings which may be subjected to a rigid inspection. For more detailed accounts of the pests and diseases of the cane, reference should be made to the following :— Van Deventer. ‘‘ Die dierlijke Vijanden van het Suikerriet op Java,” Went & Wakker. “‘ Die Ziekten van het Suikerriet op Java.” Prillieux & Delacroix. ‘‘ Maladies des Plantes cultivées en Pays chauds.” Butler. ‘‘ Fungi aud Disease in Plants.“ Archtef voor die Java Suikervindusirie. (Soerabaya). The West Indian Bulletin. (Barbados). Memoirs of the Department of Agriculture in India. Bulletins of the Hawaiian Sugar Planters’ Association. (Honolulu), The Agricultural News. (Barbados). International Sugar Journal. (London), Journal of Economic Entomology. (Washington D.C.) d Departmental Reports and Journals published in British Guiana, Trinidad, Queensland, Mauritius, Porto Rico, etc. REFERENCES IN CHAPTER IX Three Prize Essays on Cane Cultivation. Histoire des Plantes de la Guyane Frangaise. A Treatise on Planting. Natural History of Barbados. In a publication of the U.S. Dept. of Agric. Qe YH THE PESTS AND DISEASES OF THE CANE Haw, Pl. Mon., 1903, 22, 159. The Voyages of Captain Cook. Descriptio vermium in insulis Antillis, qui cannis sacchariferis damnum intulerunt. A Descriptive Account of the Island of Jamaica. Bulletin de la Société Philomathique, 1792, 1, 28. Trans. Soc. Arts, 46, 143; 47, 192. W. Ind. Bull., 1899, 1, 327. Agric. Jour. of India, 1908. S. C., 1873, 5, 477, 534- Agric. Gazette, New South Wales, 1893, 373. HS: PA. -Ex. Sta., Ent. Ser., Bull. 7. ES PAS Ex, (Sta, Ent)-Ser.); Bull.5; 6. Java Arch., 1894, 2, 4; 1895, 3, 697. Insect Life, 1888, 1, 11; W. Ind. Bull., 1904, 5, 37. Insect Life, 1892, 5, 45. Annals of the Entomological Society of America, 1917, 10, 207; IgI9, 12, EV iis Station Agronomique, Mauritius, Bull. 2. W. Ind. Buil., 1903, 4, 37. Haw. Pl. Mon., Nov., 1900. W. Ind. Bull., 1904, 5, 37. Java Arch., 1904, 12, 225. Java Arch., 1894, 2, 794. Magazine of Natural History, 1833, 6, 407. EES PAS Ex: Stas bnt. Ser Bull. 2: Deuische Entomologische Zeitung, 1896, 40, 105. Proc. Entomological Soc. of London, 1864, 51. Jour. Econ. Ent., 6. 247. W. Ind. Bull., 1902, 3, 240. Porto Rico Ex. Sta., Bull. 1. Java Arch., 1900, 7, 1013. Porto Rico Ex. Sta., Bull. 2. ’ The Sugar Industry of the United Provinces of Agra and Oude. SG ES925, 245,253: S.C., 1881, 13, 434. Mededeelingen uits’ Lands plantentuin, 1885. Mededeelingen van het Proefstation voor Mid Java, July, 1897. Jour. Agric. Research, 4, 461. Proc. Roc. Soc., 1790, 80, 346. U.S. Dept. Agric., Entomological Bull. 54 Jour. Econ. Ent. 6, 245. Jour. Econ. Ent. 7, 444. Annual Report, Dept. of Agric., Jamaica, 1915. ES PVA bx Sta... Path: Ser: Bull: 12. Phytopathology, 1913, 3, 88. U.S. Dept. Agric. Div. Plant Path., Bull. 16. U.S. Dept. Agric., Year Book, 1gor. Jour. Econ. Ent., 7, 455- Java Arch., 1896. 3. 487. Report on parasites and injurious insects, Dept. of Agric, New South Wales, 1909. Boletin de Sociedad de Agricoltura, 1909, 148. Jour. -Econ. Ent., 6, 445. Porto Rico Sugar Planters Ex. Sta., Progress Report, 1. Zeitschrift fir Parasitenkunde, 1869, I, 13. Phytopathology, 1913, 3, 363- 173 174 CHAPTER IX In a Bulletin (by Miyake) of the Formosa Experiment Station. Anonymous Article, Revue Agricole de Réunion, 1901. S2Gu5 ESO4s -2Ones 2: Bull. Soc. Mycologique, 11, 80. S.C., 1886, 18, 384. ROO 7 ONO. 2008 From various Spanish publications. Mededeelingen van het Proefstation voor West Java, 1890, 113. 3 os M; 1890, 574. Memoirs, Dept. of Agric. in India, 1913, 6, 6. Mededeelingen van het Proefstation voor West Java, 1890, 64. Java Arch., 1901, 9, 1015. Memoirs, Dept. of Agric. in India, 1906, 1, 3. Mededeelingen van het Proefstation voor West Java, 1893, 25 if PP Be “¥ & 1893, 22. Java Arch., 1894, 2, 954. Mededeelingen van het Proefstation voor West Java, 1890, 252. af 1890, 13. ” a? ES PAT Ex wota. bathe ser, Bull. 6. Trans. Royal Soc. Arts and Science, Mauritius, 1849, 1, 20. Mededeelingen van het Proefstation voor West Java, 1890, 252. Agricultural Gazette, New South Wales, 1893, 777. Centralblatt fiiv Bakteriologie, 13, 729. S.C., 1894, 26, 589. Java Arch., 1919, 26, 527. La Gangrena humida, Tucuman, 1895. Java Arch., 1893, I, 178; 1895, 3, 674. An. Bot., 1903, 17, 373- AS -ReAL Ex: otas. Patheeser, bulls: Memoirs Dept. Agric. in India, 1913, 6, 6. Java Arch, 1893, I, 372. HS. PAs sex.) Sta. (Path: Ser. bulleae Java Arch., 1893, 3, 597. Mycologia, 1896, 8, I15. W. Ind. Bull., 1918, 16, 289. Jour. Dept. Agric. Porto Rico, 1917, 1. FPS sevAl Es (Sta. eeathe oem, ssi W. Ind. Buil., 1918, 16, 283. Int. Sug. Jour., 1903, 5, 215. Jour. Jamaica Institute, 1892, 159. Kew Bulletin of Miscellaneous Information, 1895, 81. An. Bot., 1893, 7, 515- AMP bOL atOOs se Limo 73. An. Bot., 1901, 15, 683. lelysplewal, 1d5<, ashe, JEGHHo Stere, Jeyollly a7 SEG. LOO2) 245. 200; Mededeelingen uits’ Lands Plantentuin, 1885. Tijdschrift voor Land en Tuinbouwen Boschcultur, 1887, 1888. Mededeelingen uits’ Lands Plantentuin, r8o1. Java Avych:, 1893, 2, 23. Porto Rico Ex. Sta., Circular 11. eF 3 eee ull atne W. Ind. Bull., 1918, 16, 137. W. Ind. Bull., 1911, 9, 36. W. Ind. Bull., 1902, 3, 73. Gardener’s Chronicle, 1869, 447. J. Dept. Agr. Porto Rico, Jan. 1920. CERA-PT ERX THE HARVESTING OF THE CANE AT the present day almost the whole world’s production of sugar cane is cut by manual labour. The tool used is the cutlass or machete, a heavy, broad-bladed knife, shown in Fig. 23. An expert cane cutter will cut, top, and throw a thousand pounds of cane per hour, or perhaps four tons in a working day. The cutting of the crop forms an important item in the cost ot production, and uses up a large proportion of the visible supply of labour, besides placing the owners at the mercy of an irresponsible population. Efforts to devise some mechanical means of cutting the sugar cane, such as is done with grain crops, have not been wanting, but up to the present definite success has not been obtained. The means put forward fall into two classes—portable devices carried by the operator, and horse or power drawn and operated machines. Amongst the first class may be instanced that of Paul, (U.S. patent 712843, 1902), consisting of a pneumatically operated reciprocating chisel- shaped knife, which is strapped to the arm of the cutter. The same method of cutting is used by Paxton (U.S. patent 1028486, Ig12) ; in this case, however, the knife and its motor is mounted on a light-wheeled carriage propelled by the operator. In place of a reciprocating knife a circular saw mounted on a long handle and driven electrically through a flexible shaft is used in the Hylton-Bravo device (U.S. patent 733587, 1902). Two circular saws rotating in opposite directions are found in Hustace and Smiddy’s patent (U.S. 1021605, Ig12); in this apparatus the device is secured to one operator by means of a breastplate, a second operator directing the saws against the stalks of cane. No one of these devices has come into commercial use. The larger types of cane cutters all seem to be based on the grain harvester invented by McCormack, which is an apparatus of world-wide use. In designing a sugar cane harvester, however, the following points add difficulty to the problem. 1. The material to be cut offers very great resistance compared with a grain crop. 2. The most valuable part of the crop is next to the ground level, and hence the crop should be cut level with the ground. But unless some margin is allowed there is continual risk of damage to the knives employed. 3. The crop of sugar cane is found not growing upright, but lying down in all directions. Before actually cutting, the stalks have to be raised from the ground. 4. In addition to cutting the stalk the cane has to be topped, and as the length of the stalks varies within wide limits a difficult problem is introduced. 175 176 CHAPTER X 5. A successful harvester would include means for stripping off the dry leaves and for cutting the cane into convenient lengths for loading into cars. 6. Long periods of ratoonage are often economically necessary in sugar cane cultivation. The transit of heavy machines over the fields may result in damage to the subsequent crop. With irrigated cane the damage to the water furrows would be excessive, and often the nature of the ground is such as would prohibit the use of heavy moving machinery. The difficulties mentioned above have been considered and attacked by inventors, but up to the present no real success has been obtained. The | cited machines are therefore not described here, but reference may be made to the following British and American patents :—British Henwood, 3023, 1868 ; Dollens and Zschech, 4456, 1882 ; Tomlinson, 4889 and 17289, 1887 ; Stickings, 18301, 1902. American.—Wilson, 415234, 1889 ; Le Blanc, 610069, 1898; Sloane, 724345, 1903; Dupuy, 753558, 1904; Gaussiran, 775168, 1904; Bolden, 813943, 1906; Ginaca, 853967 and 854208, 1907 ; Bercerra, 903666, 1908 ; Luce, 754788 and 762073, 1904; 788270, 1905. Cane Loading.—After the cane has been felled, the next step is to load it on to the means used to transport it to the mill. Two distinct problems arise, first the loading of the cane into carts or small cars, running on a port- able track in the cane fields, and second, the transfer of the load of cane from the cart to cars, which in Cuba, Mauritius and elsewhere run on public standard gauge railroads, and have a capacity up to 20 tons. This second operation is usually known as transferring rather than loading. At the present day the greater portion of the world’s sugar cane crop continues to be loaded by hand, and the mechanical devices which are in use are mainly confined to Louisiana. Only an indifferent measure of success considered economically has attended them in Hawaii. In Cuba the pre- liminary loading into bullock carts is always performed manually. In countries where labour is very cheap, such as Java, there does not appear to be any prospect of saving from mechanical loading. A point in favour of hand loading lies in the increased capacity obtained by the closer packing of the material when hand loaded. With a per diem charge for carts and railway wagons irrespective of the load this item is of importance. The main device employed consists of a portable derrick operating in combination with a system of chain slings, into which the cane is bundled, elevated over the car, and dumped therein by means of tripping devices. The earliest patent on this system seems to be that of Bennet (U.S. 506967, 1893). This system, as used in the Wheeler-Wilson loader in Hawaii, is shown from a photograph in Plate XIX. There are numerous other American patents dealing with details based on this method. A second device consists of the grab, which is also operated from the end of a boom mounted on a portable carrier. This apparatus lifts up the cane from the heaps into which it is thrown by the cutters. The earliest patent on this scheme seems to be that of Lotz (U.S. 731923, 1903) ; but there are a number of other and later patents using this principle. A third scheme found in a number of patents, of which the earliest seems to be that of Herbert (U.S. 645851, I900), comprises the use of portable inclined endless belt conveyors, on which the cane is laid, carried upwards, and discharged into the trucks. A variant of this scheme is seen in Crozier’s patent (U.S. 1025379, 1912), which employs an inclined run-way, up which is hoisted a small car sledge, which dumps its load into the railway truck. PEATE (XE THE WHEELER-WILSON CANE LOADER. DUMPING FROM CART TO RAILROAD CAR IN CUBA. PiEArE 2X Ox TEAM WITH CANE Loan. TRACTION ENGINE TRANSPORTING CANE. A TypicAL CANE TRAIN IN THE HAWAIIAN ISLANDS. THE HARVESTING OF THE CANE 177 Although the direct loading of the cane has not been successfully accom- plished, the transfer of the cart load to standard gauge railroad wagons is readily performed. In Plate XIX is shown, from a photograph taken in Cuba, a cartload of cane in the act of being dumped into a railroad wagon. A full load for a cart drawn by three yoke of oxen is 7,500 lbs., six of which loads go to fill the capacity of a standard gauge wagon. In order to obtain these capacities the cane is cut into six-foot lengths and carefully packed in the cart by hand. Transport of Cane.—The methods adopted for the transport of cane from the field to the factory may be summarized thus :— 1. Animal power on roads. 5. Mechanical traction on light railways. 2. Animal power on tramways. 6. Mechanical traction on public railways. 3. Animal power on canals. 7. Aerial .ropeways. 4. Mechanical traction onroads. 8. Fluming. Animal Road Traction.—This method is now only used on small properties or on larger ones as a means of bringing the cane-to a central loading station. The capacity of a mule on the roads usually to be found on plantations is about half a ton of cane at a speed of two miles per hour; oxen are frequently used, and a typical team and load is shown in Plate XX. Animal Tramway Traction.—The following data comparing the cost of mule transport on roads and on tramways! may be usefully given. A tramway was constiucted two miles long of 2-ft. gauge with rails weighing 14 lbs. per yard; the average load in each car was I,g00 lbs., the train load averaging I1-25 tons ; this was drawn by two mules at a little over 3 miles per hour ; the capacity of a mule on a tramway may then be taken at from 15 to 20 times its capacity on a road. Animal Canal Transport——This method of transporting cane is used to the exclusion of other methods in Demerara and the Straits Settlements, where the estates are intersected with canals dug for this purpose. The punts used in Demerara are flat-bottomed receptacles, constructed out of wrought-iron plates with heavy wooden bottoms; they are about 25 feet long by 8 feet wide and 3 feet deep, and hold from 2-5 to 3 tons of cane ; a-mule will haul four of these punts at a rate of from 2 to 3 miles per hour. Water carriage is also employed in parts of Louisiana and of Australia. Mechanical Road Transport—Where good roads exist traction engines forma cheap and efficient means of transporting cane. In Plate XX is shown a view of such a scheme. An engine weighing 6 tons and of 20 h.p. will haul 20 tons of cane at a rate of three miles per hour. Mechanical Railroad——Undoubtedly the most important and efficient means of transport is a system of railways. The gauge adopted generally lies between 2 and 3 feet ; one of 2 feet 6 inches is wery commonly employed, but for large properties it is more advantageous to have a gauge of not less than 3 feet, as otherwise the number of wagons required becomes excessive. With such a gauge wagons having a platform area of 50 square feet can be used ; such vehicles will hold from 2} to 3 tons of cane, a perfectly safe rule being to allow half a ton of cane to every Io square feet of platform area. A locomotive weighing approximately 15 tons will haul, at a rate of Io to 12 miles per hour, twelve to fifteen wagons, each holding about 3 tons of cane. N 178 CHAPTER X The following data were obtained in Mauritius in 1904* :—The cost of laying down a system of railways to feed a factory is very considerable. The lowest cost per mile for a gauge of 2 ft. 6 in. is not less than £300, with rails weighing 18 to 20 lbs. per yard. For a 3-foot gauge, with rails 25 lbs. to the yard, an initial cost of £450 is the lowest which can be expected. These figures do not, of course, include the cost of locomotives and rolling stock. The cost of laying down the rails is entirely dependent on local conditions ; where these are favourable, and no expensive cuttings or bridges have to be made, a minimum cost of {100 per mile may be sufficient, an esti- mate to be greatly increased with unfavourable local conditions. The following figures, taken from actual practice, will give much informa- tion regarding light railway transport :— Acreage served ye oe 20 oe 56 <> 720503 Miles of permanent track .. 52 a: dic 5 its). Gauge sn oe as 3 ft. 1, in. Number of locomotives ot “6 a0 see Os Weight of locomotive se 36 a2 ote .= ) 5a tonss Number of wagons a ee oe ae Me Le Size of wagons ia: A hs Sc B6 +. Slo it byssaite Load of wagon Pr ae 4a 2°75 tons. Number of wagons per train ae ae ie aos Cane tianspoited per 24 hours .. a ae 2. 900) tons; Average distance of transport =; O6 se ego antlese Cane transported during crop Se a as .. 100,000 tons Coal burned per ton-mile a5 oe Se ae a7e. lbss Maintenance of line and rolling stock per ton-mile .. 0+772d. Fuel per ton-mile .. ate on Bo ais «3 56d. Stores per ton-mile .. or 5¢ ie dc -. ©: 260d. Labour per ton-mile Me 36 0 ae O40. Total cost of transport per ton mile ae ae nO 2 OGLE On all the larger plantations in the Hawaiian Islands 30-ton locomotives are used, capable of drawing a load of 300 tons of cane ; a typical cane train is shown in Plate XX. Transport on Public Railroads.—In certain districts, notably Cuba and Mauritius, much of the crop is transported on the public railroads. This system is used very successfully in connection with cane farming, and allows of a large number of farms or colonias existing a considerable distance from the centrals. In Cuba the rates charged are expressed per metric ton per kilometre: o-I0 kms., I-10 cents; 11-25 kms., 0:6 cent; 26-50 kms., 0:45 cent ; 51 and upwards, 0-30 cent. There is also a charge of 3-75 cents per day per ton capacity of the car. In Mauritius the rates were (1904) ro cents of a rupee per ton per mile for the first, 8 cents for the second, and 6 cents for the third and following miles. Aerial Ropeways.—As a means of transport in hilly or broken districts, notably in Mauritius, ropeways find some use. The following description of the ropeways often used in Mauritius is after Wallis-Tayler® :-— “The arrangement consists of a driving gear at one end or terminal of the line fitted with a driving drum suitably geared to receive rotary motion which, in this instance, is provided by the power of the cane mill, and a similar wheel at the other end fitted with tightening gear, an endless band of wire rope being mounted on these wheels. At intervals of about 200 ft. intermediately between these terminals the rope is supported on pulleys mounted on posts at a suit- able height to enable the carriers to clear all intervening obstacles, and to a certain extent also to regulate the genera] level of the line. The carriers hang from the rope and are enabled to pass the supporting pulleys by means of *Present-day figures will be very different from what obtained then, but this section is included as it appeared in the first edition of this work, since some of the unaffected data are contained herein. 179 THE HARVESTING OF THE CANE DNINFLHOIL s PED Wy BSA, eC NAL er Bert hort Tin an Bree, 180 are CHAPTER X curved hangers. These curved hangers are pivoted on V-shaped saddles resting on the rope, the saddles having malleable cast-iron frames fitted with friction blocks to enable the requisite friction on the rope to be obtained, and allow the carriers to pass with the rope up steep inclines, and over the pulleys, wings at each end of the saddle frames embracing and passing over the pulley rims. The saddle frames are besides each fitted with two small wheels mounted on pins which admit of the carrier being removed from the rope at the terminals, and at curves, on to shunt rails held in such a position that when the carrier approaches the terminal the small wheels will engage on it, and running up a slight incline lift the friction clip saddle from the rope and enable it to pass to the loading or unloading station or round the curve wheels, the impetus derived from the speed of the rope being sufficient for the purpose of enabling the carriers to free themselves automatically from the rope.” Views of this scheme are shown in Fig. 71, and a view of the cradle in Fig. 72. In some cases the configuration of the land will allow of a gravity system ; in the simplest arrangement the loaded cradles run down a fixed rope and afterwards packed back to the fields ; in another system the descending load works an endless rope which also carries back the empty cradles. Fluming.—Fluming is a method of transport used to a very considerable extent in the Hawaiian Islands. A flume consists of a wooden gutter of V-section. The material used is pine lumber, I in. x 14 in., and for ease of transport is made in 12 ft. lengths ; vertical boards, 6 in. high, are fixed above the sides of the gutter. It is supported on light wooden frame- work, and ends directly over the end of the conveyor carrying the cane to the crushers. The canes are carried down the flume by means of a stream of water. In Fig. 73 is shown a view of such a flume. Approximately 1,000,000 gallons in 24 hours will flume 10 tons of cane per hour. Fluming is a most expensive method of trans- portation, and has been developed solely on account of some conditions peculiar to the Hawaiian Islands. These include factories located at or near sea level, steep gradients and the presence of ravines or gullies making railroading difficult, combined with an abundance of water. The weakest feature of a flume system is that it only oper- ates in one direction, and separate means have to be adopted to carry supplies to the fields. THE HARVESTING OF THE CANE 181 Cane Unloading.—The cane after arrival at the factory is transferred by one or other of the means described below on to an endless belt slat conveyor, or is dumped into a hopper and elevated to the mill by an endless belt con- veyor set atasteepangle. Theconveyor is provided with broad curved teeth, which catch the tangled mass of material and prevent it slipping backwards. The endless belt conveyor, usually called a carrier, as opposed to the elevator, is claimed in Patent 8731, 1840, granted to Robinson on behalf of unnamed parties. This patent includes means for cutting off steam from the engine when the thickness of the feed of canes is too great. The hopper and elevator appear first in Kiely’s patent (U.S. 675222, Igor), and are indicated in Plate XXT. \ \ - A oer eS Sp - The methods actually used are :—r. The hoist and dump. 2. The car dump. 3. The endless belt rake. 4. The reciprocating mechanical finger. The first patent on the hoist and dump is that of Carr (U.S. 517730, 1893), but that of Kiely (U.S. 675222, Igo1) has been very extensively used in Cuba. This method, which is similar to the cart transfer, is indicated in Plate XXII. In using the hoisting device, chain slings are laid on the car previously to loading. In Cuba the car dump is superseding the hoist and dump. This method is claimed in Sanchez’ patent (U.S. 520271, 1894). In this device the cane is dumped into a revolving cylinder, which distributes the material to the carrier. This latter appliance has not come into use, and when the dump is installed the load is dropped directly into a hopper of the type shown in Fig. 74. The cane cars are provided with doors, swinging from the top. Alongside the hopper is arranged a platform, which pivots about a fulcrum, as indicated in the figure ; at a certain angle the whole contents of the car 182 CHAPTER X slide into the hopper. This apparatus is usually found arranged as a side dump, but is also installed as an end dump. The power used may be hydraulic, a cable hoist being usually operated by an electric motor or spur and pinion gearing. The endless belt rake was first patented by Mallon (U.S. 583408, 1897), and has been developed by other inventors. The form shown in Fig. 75 is that due to Gregg (U.S. patent 670176, 1901). In this device, which has been largely used in Hawaii, the triangular frame carrying the rakes is allowed to fall on to and to follow the load of cane. One side of the car has a drop side swinging from below and forming a bridge from car to carrier. The reciprocating mechanical finger was patented originally by Walsh (U.S. 628877, 18a9), and is indicated in Fig. 76. The mechanism allows a reciprocating motion, and one around the point of suspension of the beam. This appliance, which has also been developed by other inventors, is very extensively used in Hawaii. The Detericration of Cut Cane.—After sugar cane has been cut it begins to lose in weight through evaporation, and simultaneously a loss of sugar occurs through inversion. Evidently the rate of loss of weight will depend on the prevailing temperature and humidity. The rate of loss of sugar will also depend on the temperature, and will most certainly obey the laws of chemical change referred to in subsequent chapters, as is indeed indicated by combining the results of the experiments quoted below. The initial agent causing inversion of sugar is, as was shown by Browne and Blouin, an enzyme that resides in the green top of the cane, and which after the stalk has been cut diffuses into the body of the cane. Experiments made by them in Louisiana gave the following results on canes that were “‘ windrowed ”’ or preserved for subsequent planting by burying in the ground. The dura- tion of the test was one month. THE HARVESTING OF THE CANE 183 PURITY OF JUICE. Topscuto#f 82-6 81-0 82-8 84°5 80°5 Tops left on 76:1 74°6 77°90 74°6 71*3 These results were confirmed in Argentina by Cross and Bielle,4 who found after four days’ keeping a purity of 62-81 in canes with tops cut off, as opposed to 48-77 in canes with the tops left on. Pellet® in the winter months in Egypt obtained the following results on storing canes :— Loss in Purity of Less in Purity of Days. weight juice. Days. weight. juice, per cent. per cent. fo) fe) 88-5 20 9:0 87:8 4 2°5 89:2 2a I2°5 86°5 7 4°3 88-1 25 I5°0 87°1 II 10-0 89:6 2 18-0 85°3 15 8-7 87-0 Von Czernicky® in Java found the results tabulated below :— CANES ONE DAY IN OPEN, BALANCE N go- 15° 18- I2: 69: se Weight of Wud 0 + HH GOW mI On Curve conmecting pressure 17 128. per sai & height ofa column of bagas. ; se SIlbs tiber F26% bagasse pase 2 “ 6 8 Height Inches Fic. 78 TEC O77G Aarizonta exis. OF COMTI TE S66 SPU? F Tess) a5 Height of Colin alere } | (2 the extraction of juice is largely {one of exposing cane fibre to great pressure, the writer made an experimental study? of the behaviour under pressure of cane fibre, represented by chopped cane and by bagasse. The experiments were made in the following manner:—The material was placed in a cylindrical iron pot with a perforated bottom. By means of a tightly fitting plunger known pressures were applied to the 188 CHAPTER XI material, the weight and composition of which was known. For each pressure observations of the volume occupied by the material, or, in certain experi- ments, of the volume of juice expressed, were made. Certain of the results are given below, the connection between quantity of material used and the quantity of cane milled in a given time being found as follows :—A 78-in. mill worked at a peripheral speed of 25 ft. per minute describes 23,400 sq. in. in one minute. If in one hour 100,000 Ibs. of cane with 12 per cent. fibre are milled, 200 lbs. of fibre correspond to 23,400 sq. ins. of roller surface. In certain of the experiments the area of the material exposed to pressure was 8-43 sq. ins., so that the quantity to correspond with the milling of 8-43 X 200 100,000 lbs. of cane with 12 per cent. of fibre per hour would be a3AGo = 0-072 lb. fibre. The results obtained showed :— I. The quantity of juice expressed increased with the degree of fineness to which the material was divided. 2. Material which had been once pressed up to a certain pressure was allowed to expand and then repressed to the same pressure ; four pressings were required before all the juice capable of extraction at the selected pressure was obtained. The experimental data connecting the above two observations aie given below. The material used was chopped cane, varying in fineness from 0-25 inch cube to a fine meal. The tables are arranged with the coarsest material at the left. All pressures at 4,740 !bs. per sq. in.; 0°882-lb. cane is used, cor- responding to 147,000 lbs. per hour, in 78-in. mill at 25 ft. per min. These results may be interpreted as indicating that fineness of division and re- peated pressings are of more importance than a smaller number of pressings at largely increased pressures. so hen koh B=lt= so hen} a eae Oo wise = o .|o8 Os oe eee Sm ah | © . f= fies OLS el Sy—, Wry Sie Wry S.2nao Wry “3 Bp rs “4 60.8 ise "3 00.@ @ "SOD CM es OSes egy lees ag CMa la SO] SMA aS 0] co =a B.4 ~p SP EeIsH PHRHISEARAI/PRE| SE SIPERC Sa RBiPRHISSEHEloaos|Sa& QOSIS oS s|SOL/SG SQM Sa slQ°Klos aio Moa | 4 ) ¢ — oF k slog Sle slog s/Frolog gH kalegsinga OT ERs. | ee per Seer eee | nae ae eas A, ° mak — — | os es apa ae Ss ~ << — |__| —-_._- - — aa - First pressing] 58-3 | 58°3 | 59°0 | 59:0 | 62*3 | 62°3 | 64-0 | 64-0 | 64°4 | 64°4 SECON. eas 8-5 | 66°8 8: 67°8 Sse 7lol eeOlOn| | 73" k2"'O ih 7oag Third oi 5°8 26 | 6:0) 74:8 Zig) | 7501). 4s7 1) 78°90 2°6 | 79°6 Pourthy) 5; PI Xate |g /aioy \alene PZ ly |e 7laieoe | = aoten | agro) 1°6 | 80°2 2°0 | 81-0 3. The quantity of juice expressed increased as the quantity of material sed decreased, as indicated in the data given below. All Pressures 4,740 lbs. per Sq. Inch. Equivalent in lbs. per e ‘ : Weisner "2s nonten Se-eniitae ann) (erence Oh tice Oca Cane— lbs. | surface speed of 25 ft. —_—— per min. I 2 1763 244,000 63°40 62°90 ee 2s 184,000 65°75 65°75 o- 881 122,000 68+50 67:60 0*440 61,000 69°50 68-70 0-220 30,500 74°00 70:00 THE EXTRACTION OF THE JUICE BY MILLS © 189 The results may be interpreted as favouring a high speed and a thin blanket of material. 4. Under pressures up to 60 lbs. per sq. in. it was found that the volume occupied by bagasse varied inversely as the 2-5th root of the pressure, or symbolically V P’* = constant, where V is the volume of the bagasse and P is the pressure. If the bagasse be pressed in a cylinder, H, the height of the column of bagasse under pressure may be substituted for V. Data of an experiment are given below, the results being also expressed as a curve in Fig. 77. HEIGHT OF 0*22I LB. BAGASSE, CONTAINING 32°6 PER CENT. FIBRE, ON A SURFACE OF 8:43 Sg. INS., CORRESPONDING TO 100,000 LBS. CANE CONTAINING I2 PER CENT. FIBRE PER Hour, AT A SURFACE SPEED IN ROLLERS OF 25 FT. PER MINUTE IN A 78-IN. MILL, UP TO PRESSURES OF 60 LBS. PER SQ. IN. Pressure lbs Height. per sq: 18. =P: inches =H. Po 5 He soc 3°358 aay 4°90 6-1 2°238 x 4°51 IIel 1-889 ee 4°96 TO. = 1°658 — 5°01 Ze 7 1° 467 se 4°99 26°1 i333 ane 4°92 Sri 1-283 30: 5°09 360°1 I*183 aoe 4°96 41° I*I00 sb 4°85 46-1 I*039 as 4°80 51I°1 Bas 0-989 =e AS 77, 56°1 e's 0*944 os 4°74 5. At higher pressures, I,000 lbs. per sq. in. and upwards, the volume of bagasse varied inversely as the 5th root of the pressure, or symbolically H P-? =constant. Data of an experiment are given below, the results being also expressed as a curve in Fig. 78. 0.397 LBS. BAGASSE CORRESPONDING TO 120,000 LBS. OF I2 PER CENT. FIBRE CANE PER HOUR IN 78-IN. MILL, AT A SURFACE SPEED OF 25 FT. PER MIN. Pressure lbs. Height. per sq- das —P- inches =H. 1g H Eee HEP 31 oe I-79 3°97 983-0 83 I-10 2°65 I31I°O 162 ° 0-845 2°37, “os 7307 321 0+ 67 2°12 sie 43°0 480 : 0°53 1°85 se 29,7 640 0°52 I-90 ese 24°7 703 0+ 50 I-89 ale 24°2 1193 O: 465 I-90 24°7 1595 0°42 xe 1°84 2T-% 2390 0+39 = 1°85 25 ve 3137 0°37 1-86 22°3 3972 ; 0+ 36 1-82 I9°9 4778 O° 35 1°91 23°2 5574 . O° 34 : I-90 24°7 6369 0°33 I-9 25°2 7166 O* 32 I-89 24°2 7980 O° 315 I-90 24°7 8757 0-31 I*o1 25°2 10347 — 0+ 305 1°93 = 205 II940 aS 0:30 1°97 oe 29°7 At higher pressures the volume of juice expressed from chopped cane varied as the twentieth root of the pressure, or symbolically J P~” = con- stant, where J is the volume of the juice expressed.* *In my original publication I gave the volume as varying with the twelfth root. In commenting on these results Bolk? observed that the twentieth root gives a much more constant value. 190 CHAPTER XI Details of an experiment are given below, the results being also plotted as a curve in Fig. 79 :— 60 foie conn Ea mressure &percerila ; Ve COnRETINg ye of yyice obraped Fre 50 § u A ie ae eee Q 40 S 3 350 d #® 20 8 | N 310 1000 2000 3000 4000 5000 6000 ©7000 8000 9000 10000 4000 2070 Pressure /bs per sg Fic. 79 VoLUME_AND WEIGHT OF JUICE AND VOLUME OF RESIDUE OBTAINED ON PRESSING 3° 410 LBS. CHOPPED CANE UP TO II,940 LBS. PER SQUARE INCH. | Pressure {| | Volume of | Weight of | Volume of lbs. per Juice Juice Wf Residue J4+R (ie Wb geo sq.in. =P. | c. in. =f. | on Cane. | c. in. =R. | 68 13°2 14°8 75°5 88-7 176 83 13°r 20°3 70:0 88-1 169 104 23:7 26°5 63°4 87-1 r60 123 26:6 29°8 60-2 86:8 158 162 31°5 35°2 54°1 85:6 150 203 34°1 38-1 50°9 85:0 147 242 360°6 41-0 47°60 84°2 143 321 41-0 45°9 42°6 83°7 135 406 Aoe7 50°9 40°1 83°8 133 480 46:0 51°5 By k 83:0 130 640 49°6 55°9 33°5 83°2 122 800 51°3 57°4 20 T 83:3 122 Ba 1000 53°3 58:6 30:8 84:1 122 37°7 I193 B37 60-1 29:8 83°4 122 37°06 1595 54°9 61°4 28°6 83°5 125 37°8 1993 Sem 62-1 28-2 83°77, 129 3752 2390 50:2 62:9 27°6 83:8 13} 38:0 3187 56°5 63°3 27°1 83:6 136 Saw, 3972 57°2 64:0 26:6 83:8 140 3757, 4778 57°56 64°5 26°2 83°9 142 3775 5574 57°8 64°7 26°90 5377, 146 37°38 6369 58-0 64°9 25°7 83°7 148 373 7166 58°3 O523 25°5 83°8 150 37°2 7959 58°4 65°4 25°2 83°7 151 37°2 8757 58:9 65°9 24°9 83°7 153 37°2 9555 59°0 66-1 25°5 83°5 153 37° 10747 59°6 66-7 24°0 83°5 154 37°2 T1145 60°0 67°1 23°7 83°7 153 37°73 11940 60° 2 67°3 23°5 83°7 152 3753 THE EXTRACTION OF THE JUICE BY MILLS IgI In the table above is also given the volume of the residue, R, and values of R P-?. The curves given in Figs. 78 and 79 are the converse of each other; in both, the curve begins to bend from the horizontal or the vertical at about 500 lbs. per sq. in. pressure, and assumes the vertical or horizontal at about 2,000 Ibs. per sq. in. pressure. After this pressure has been reached, great increases in pressure are accompanied by relatively very small increases in the volume of juice expressed and by very small decreases in the volume of the bagasse or cane fibre. The writer does not wish to be understood as expressing the opinion that these relations are absolute ; they are rather of the nature of approxi- mations, and probably the real relation is of the form V P’'” = constant, the exponent increasing as P increases. Work done and Power absorbed in compressing Bagasse.—Allowing that the relation, H°P = constant, represents the behaviour of bagasse on pressure, the work done in passing from a volume V, to a volume V, is [Kae rae b Consider the case of a column of bagasse on a base of I sq. in. and 0-6 inch high, which is to be compressed to 0:25 inch high. Then the work done in compressing is : See cae Sees eee [KH = (0 6~4— 0°25 ) In the experiment quoted previously the value of H®P is about 9-5, so that the value of the integral in this particular instance is 590-1 inch-lbs. or 49:2 foot-lbs. A 78-in. mill describes 23,400 sq. in. in one minute, and grinds 100,000 Ibs. of cane with 12 per cent. fibre in one hour. The work done in one minute is then 49-2 X 23,400 = 1,151,280 ft.-Ibs., which 1,157,280 _ 35 HP. 33,000 This result, of course, refers to the actual work done in one compression according to the observed data, and does not include the work represented by friction, trans- mission of power, etc. See The work done in compressing fibre = under the equation, H°P =K, is independent of the way the pressure is applied. In Fig. 80 let ” = the specific normal pressure on a small particle of bagasse, and let ¢ be the Fic. 80 specific tangential pressure causing uniform : motion of the particle. Then the condition of equilibrium of the particle of bagasse is requires hb B 8B | tds cos a = nd s sin @ A A If a is small, cos a = r and B B : | tds -| n ds sin «. A A 192 CHAPTER XI But since ds sin « = dah h [i2as =| oe W. A i a If v is the peripheral speed of the roller, the work done in a unit of time B hy, isw=v| tds=o| n al A 3 ha ape! (oe 4 That is to say, the work done in the compression of cane fibre is independ- ent of such factors as the curvature of the rollers, the size of the mills, etc. The power required, however, will vary with the skill of the designers and of the operators. The work done in compressing bagasse is also independent of the method used ; for example, direct pressure in a cylinder by means of a plunger, or by means of rolling mills, as is the means adopted in practice for the application of power. Relation between Fibre per cent. in Bagasse (Efficiency) and Tonnage milled (Capacity and Power required).—In the immediately preceding section on certain experimental observations, the power required to compress 100,000 Ibs. of cane, with 12 per cent. fibre, in a 78-inch mill describing 23,400 Sq. in. per minute to a layer 0-25 inch high was estimated at 35 H.P. To compress the same quantity to 0-20 inch will, under this general oe THE EXTRACTION OF THE JUICE BY MILLS 193 law, and under exactly the same condition as in that computation, require . ag ORO ‘i 9-5 X 0:20 °° -2. (0:60-*-0-20-*) =1467 “20 inch-lbs., or 87 H.P., as compared with the 35 H.P. found before. Similarly, if the relation H®P = 9-5 hold to so high a limit, the ultimate = 23, pressure on the layer of bagasse will be P = = 29,687 Ibs. per sq. in., whereas when H = 0-25, P is only 10,000 Ibs. ie sq. in. Under the very high pressures it was found that each diminution in the volume of the bagasse was accompanied by an equal volume of juice expressed. Consider a column of bagasse on a base of I sq. in. and 0-25 inch high, and let this quantity of material contain 0-00855 Ib. fibre and 0-00855 Ib. juice, i.e., 50 per cent. fibre and 50 per cent. juice. Let the column of bagasse be compressed to a height of 0-20 inch, then it will contain 0-00855 Ib. fibre and 0-00670 Ib. juice, taking the 0-05 cu. in. of juice expressed as weighing 0-037 lb. That is to say, the bagasse will now contain 56-0 per cent. fibre and 44-0 per cent. juice. On this argument the following table may be constructed, referred to the same basis as before, namely 100,000 lbs. of cane, with 12 per cent. fibre per hour, in a 78-inch mill describing 23,400’ sq. in. in one minute. Height of column | Horse Power | Fibre % in of bagasse Pressure. | necessary for one | bagasse. inches, H. compression. 0*20 29700 87 56°70 O21 23200 71 54°6 0:22 18300 59 53°4 o°2 | 14700 49 52°2 0°24 I1g00 41 51°1 O52) 9700 3) I970 0*26 7999 30 49°0 0°27 6590 25 47°9 0:28 5500 22 | 46°9 0°29 4610 19 46:0 0-30 3g10 16 | 45°1 An idea of the variation in the composition of the bagasse with variation in the quantity of cane milled, the power remaining the same, may be obtained as under. In the preceding section it was estimated that 590-1 inch-pounds were required to compress a column of bagasse I sq. in. section and 0-6 inch high to a height of 0-25 inch, and on compression the bagasse was taken as containing 50 per cent. fibre and 50 percent. juice. Let twice the quantity of bagasse be compressed, the original height being 1-2 inches; let x be the height to which this quantity of bagasse can be compressed by 590-1 inch- 12 pounds : then | BP 2025. Hs? = 500+ 2 whence x = 0:602. This height of the column of bagasse plese 3x to a height of 0-301 inch, when the quantity of cane milled is 100,000 Ibs. per hour, and when in this case the column of bagasse was 0-25 inch high it contained 50 per cent. fibre, there being 0-00855 lb. fibre and 0:00855 Ib. juice. With a height P 194 CHAPTER XI of 0: 301, and remembering that for each decrease in the volume of the bagasse an equal volume of juice is expressed, there will be 0-00855 Ib. fibre and 0-01070 Ib. juice, making the percentage of fibre 45-1. Hence under the general equation H'P = k, as expressing the behaviour of bagasse on com- pression, it follows that doubling the quantity of material and expending the same work, the fibre in the compressed material falls from 50 per cent. to 45° per cent. The writer does not wish to be taken as meaning that the numerical values selected are necessarily accurate, though he believes they are of the general order of what occurs in practice. They are introduced chiefly to give a concrete expression to the formule deduced from experiment. Three points stand out, however, upon which reliance can be placed: First, great increases after a certain limit in the hydraulic load on mills will not be accom- panied by any but small differences in the composition of the bagasse ; secondly, after the fibre content of the bagasse reaches a certain figure. Paes it = Fic. 82 a very great! consumption of power is required to further reduce it; and, thirdly, very great increases in the quantity of cane milled are not accom- panied by very large differences in the composition of the bagasse. In - other words, the capacity of a milling plant, between the limits of what is considered reasonably good work and the very best work, is very great; that is to say, a milling plant is a very elastic machine. Power required to mill Cane.—With the results discussed above may be compared others giving the indicated horse-power developed by mill engines in actual operation, as found by the writer.” CANE CARRIER, CRUSHER AND MILL, 34-in. X 78-in., WORKING AT RATE OF 50 SHORT Tons CANE PER Hour WITH 12°7% FIBRE, WITH HYDRAULIC LOAD OF 400 TONS. EP. HAP: Indicated H.P. per ton-cane-hour. per ton-fibre-hour. Max. 218 Aa0 4°30 aes 34°? Min. 166 500 3°33 Sue 26°. Mean 184 S60 3°68 acs 28°9 THE EXTRACTION OF THE JUICE BY MILLS 195 THREE MILLS AS ABOVE (2ND, 3RD AND 4TH). 412 Hee: Indicated H. P. ton-cane-hour-mill. ton-fibre-hour-mill. Max. 443 sce 2°95 Ae 23°3 Min. 332 ace 2°25 eee I7°4 Mean 372 a 2°48 ase I9°5 The Cane Mill.—The machinery employed to express the juice of the cane by milling consists of a system of horizontal cylinders, any two co-acting units of the system being caused to rotate in opposite directions by means of suitable gearing. The mill proper has by this time been reduced to a standardized 3-roller pattern (shown in side and end elevation and in plan in Figs. 81, 82 and 83), characterized by the location of the centres of the three rollers a,, a, a3, at the angles of an isosceles triangle. ‘he rollers are carried on shafts, axles, or gudgeons, which are in turn sup- ported on brasses, hy, hg, hz, in frames, 6, placed at either end of the rollers. These frames are known as housings, headstocks, or cheeks, and rest on the sole plate g. The rollers are restrained in position by means of caps, ¢y, Cg, Cz, bearing on the brasses, directly or through distance pieces, the caps being secured te the housings by bolts. Those bolts, d, passing through the top cap are known as the king bolts, thoroughfare bolts, through-way bolts, or top-cap bolts; those, e, securing the side caps are known as the side-cap bolts. On one end of each shaft, and sometimes on both ends, is fitted a toothed wheel or pinion. The shaft carrying the roller, the centre of which corres- ponds with the apical angle of the isosceles triangle, receives motion through a train of gearing and connecting shaft from some prime mover. 196 CHAPTER XI The pinion on the end of this shaft co-acts and gears with the pinions on the shafts of the lower rollers. The lower rollers then will rotate in the same sense, and in a sense opposite to that in which the upper roller rotates ; the direction of rotation, clockwise or counter-clockwise, depending on the Fic. 84 direction in which the material being crushed travels. The upper roller, a, is known as the top roller; that lower roller, a,, which first receives the material is known as the front, feed or cane roller; the other roller, as, is known as the back, discharge or bagasse roller. Reference to Fig. 81 shows that there is formed a space between the lower rollers where it is necessary to define a passage for the material until it is gripped by the top and back rollers. This passage is defined by the lower Fic. 86 Fic. 85 Fic. 87 portion of the top roller and by a bar of varied shape and curvature sup- ported on the housings and running parallel to the axes of the rollers. This bar is known as the trash turner, returner bar, dumb returner, knife, bagasse bridge or bagasse guide, and, to avoid confusion, is not shown in Fig. 81. The exact arrangements employed by different firms show considerable THE EXTRACTION OF THE JUICE BY MILLS 197 variation, and designs derived from and different from the isosceles com- bination are found, as well as others with quite a different origin. These variations will be described presently, together with some account of the preparatory devices and the accessories to a milling plant. The Development of the Three-Roller Mill.—Pressure of some sort has been used from primitive times in order to extract juice from the cane. Perhaps the earliest method is that which is still used by the autocthons of South America, and until recently by the ryots of British India. This method is based on the pestle and mortar, the latter element being furnished with a hole in the bottom, whence the juice . drains. A hollowed tree stump is often utilized as the mortar. The earliest extant account of sugar manufacture is to be found in the Gesta Det per Francos, written in the twelfth Fic. 88 Fic. 89 century, and here is mentioned a screw press of some nature as being used by the Saracens in the Levant in the extraction of juice. Willughby,* in the seventeenth century, describes a cane mill, evidently developed from an early type of corn grinder as used in Spain. It consisted of a wheel rotating about its axis and also about the end of a shaft attached to itself. The path of the wheel was a circular perforated gutter, in which the cane was laid. He also saw mills of two horizontal wooden rollers covered with iron plates. The roller mill was used in India at a very early date. A report prepared by officials of the Hon. East India Co., of date 1822, shows two types. In one the rollers are vertical, and are provided with co-acting spiral gears carved out of hard wood; in the second the rollers are horizontal and each is rotated independently of the other by manual power through wheels 198 CHAPTER XI with long radial arms. The first mill of three rollers was made in Sicily in 1449 by Pietro Speciale. This type of mill was used by Gonsales de Velosa in 1506 in the first factory erected in the New World, at Rio Nigue, in San Domingo, and by old writers is often des- cribedas of his invention. It consisted of three rollers, either horizontal or vertical, with their centres co-linear. Simi- lar ends, and in the latter case upper ends, of the shafts carried co- acting pinions, the cen- tre roll being selected for receiving the drive, which was taken from an overshot water- wheel, a windmill, or from horse, cattle or slave power, moving in a circle at the} end or along beam. This type cf mill remained in use for many years; it is illustrated in Fleming’s patent (1057, 1773), which contains in addition (and forming the subject of the patent) a supplementary roller of smaller diameter and a wooden bar set oblique to the roller, the combination serving to direct the once crushed cane to the line of contact between the centre and discharge rollers. This patent contains the genesis of the trash turner. In the old West Indian houses the mill itself was often located below the ground level, as more con- venient for the application of animal drive. These mills were known as pit mills. Steam power was first applied to mills in 1769, this date being fixed by a reference in a paper® read before the Royal Society by the Marquis de Cazaux in 1780, stating that eleven years earlier a steam engine had been sent to Jamaica. Steam power did not become common, however, till much later; its introduction into Demerara and Surinam took place in 1815, due to the initiative of a Dutch Fic. 91 carpenter, Forster.” The first mill with the isosceles triangle combination was made in 1794 by Collinge, an axle-tree maker of Lambeth.® A design of this nature was also found amongst Smeaton’s papers at his death, with the notation that it was NSS es Ly Ze > THE EXTRACTION OF THE JUICE BY MILLS 199 designed in 1754 for a certain Gray in Jamaica, but not executed.? To the mill as arranged by Collinge the trash turner, as now understood, was added very early in the nineteenth century by Bell,a Barbados planter.® The original form of housing (which may be still seen in Brazil) was made of wood, the top cap of the modern mill being represented by the massive tripartite yoke, a, Fig. 84, king bolts being absent, so that the system in a way anticipates the boltless all-steel housing of recent introduction. The next development took the form indicated in Fig. 85. In this de- sign the rollers were re- moved by lifting after the removal of the dis- Fic. 92 tance piece. This type of housing is ill adapted for resistance to the horizontal component of the angular thrust, and fracture was frequent along that line, although some additional security was given by the tie-rod passing through the distance iece. 3 Another form of housing of early date is shown in Fig. 86. This type is found illustrated in early American patents, and has been made by French houses, but does not ever appear to have been tried by Scotch firms. It had the disadvantage that the removal of a roller necessitated the canting over of one of the housings. Buchanan’s patent (1574 of 1858) claims the form of headstock identical with that now generally employed. This type is shown in Fig. 81, and is referred to as the open-side gap type, one of the patent claims being for the removal of the rollers horizontally by sliding without the necessity of lifting. This patent also introduces the side caps, Fig. 81, bearing on the brasses of the lower rollers and serving to retain them in position. These side caps were recessed into the housing, and in Buchanan’s design were secured thereto by wrought-iron tie-rods or bolts running in a direction farallel to the direction of the axes of the rollers. Buchanan’s patent also claims the build- ing up of the housing from wrought-iron plates bolted together, but the different functions of wrought and cast-iron in tension and compression in a cane mill - housing had been previously described by Mirrlees, in his patent, 13689 of 1851. Rousselot (patent 790 of 1871) adopted Buchanan’s form of housing, 200 CHAPTER XI with the direction of the side cap tie-bars turned through a right angle, so that they pass into the housings in which they were secured by cottar pins, a method changed by Watson (patent 1606 of 1871) to T-headed bolts recessed into the housing, and indicated in Fig. 87. Fletcher’s patent (316 of 1877) shows the side-cap bolts as continuous from cap to cap, and this method is most generally employed. The Housing and Arrangement of the Rollers—There are many designs which, while retaining the isosceles triangle arrangement of the rollers, depart from the horizontal side gap or Buchanan type of housing. Walker (patent 1486 of 1860) cast the housing so that the rollers rested on surfaces perpendicular to the line joining the centres of the top roller and of a lower roller. This arrangement, which prevents any horizontal movement of the FIG. 95 lower rollers, is also found in the designs of Wilson (patent 2754 of 1861), of Bartlett (2656 of 1878), of Thoens (U.S. patent 615591, 1898), of Boyer (U.S. 976144, 1910), and of McNeil (patent 11727 of 1912). It also appears in the mill known as the Hamilton mill, shown in Fig. 88. This arrangement is also the type indicated in Stewart’s patent (3269 of 1871), dealing with the application of hydraulic pressure to cane mills. A mill with the king bolts following the lines joining the centres of the top and of a lower roller was patented by Fletcher (316 of 1877), Fig. 80. A somewhat similar design was patented by Buchanan and Keay (233 of 1884), and again many years later by Delbert (U.S.880332, 1905). Housings and roller arrangements very different from the standard pattern are illus- trated in the designs of Allan (patent 18800 of 1888), Fig. 90; of Hatton (11729 of 1889), Fig. 91; of Skekel (U.S. 480522, 1892), Fig. 92; and of Alliott and Paton (11524 of 1897), Fig. 93. Of these mills, those of Allan and Hatton dispense with the trash turner, that of Alliott and Paton reduces its width, and that of Skekel replaces it THE EXTRACTION OF THE JUICE BY MILLS 201 with a corrugated roller. The rotary trash turner applied to a standard form of housing also appears in a patent of Fletcher (14562 of 1891). As is explained in detail later, the pressure between the top and the back roller of a mill is much greater than that between the top and the front roller ; consequently the top roller is thrust against the jaw of the top gap on the feed side. The first attempt to compensate for this unequal strain is seen in Hall’s inclined housing, Fig. 94, the king bolts being arranged parallel to the supposed resultant of the forces acting on the top rolier. In Hedemann’s design (U.S. patent Io16301, 1914), Fig. 95, compensa- tion for the side thrust is also at- tempted, with the addition that a variable position of the resultant is allowed, this position being determined by trial and error. Bolk’s design == (13471 of 1912), Fig. 96, leaves the two lower rollers rigid and allows for Fic. 96 the adjustment of the top roller ina vertical and a horizontal direction by means of wedges above, below, and on the sides of the journal bearings. The king bolts pass outside the bearings, and the rollers are driven by an idler pinion. In Fig. 97 is shown Fogarty’s mill (U.S. 535577, 1895), which replaces the ordinary housing with a circular framing. Mill Rollers.—The mill rollers consist of a shaft, upon which is fixed a shell forming the roll proper. Fig. 98 shows in half section a common type of top and bottomrollers. In modern practice the shaft, a, is forced into the shell, 6, in an hydraulic press, permanency of attachment being secured by contact and bya key. To prevent juice entering between the shaft and the shell, juice rings seal the opening. The inner ring, ¢, is put on in halves, and over it is shrunk on an outer ring, d. The top roller > is supplied with flanges to prevent bagasse being extruded sideways. The flange may be a part of the roller as shown, but is better bolted to the shell, so that the upper and Fic. 97 lower rollers may be interchangeable. The wear and tear of the shells forms a large item in the upkeep of a mill. In place of renewing the whole shell, a common practice in Hawaii is to remove a four-inch ring from the shell, and to shrink on a new outer part, which is further secured to the remainder of the shell by dowel pins. As the new portion wears down it may again be renewed. 202 CHAPTER XI The size of rollers has become standardized in six-inch lengths, from 36 inches to 84 inches ; to 42 inches, but diameters over 36 inches are very exceptional. —— SS Fic. a the corresponding diameters extend from 24 inches A metric size which is very common in localities where French firms have been active is 800 mm. by 1600 mm. The King and Side Cap Bolts.—The arrangeinent of the king and side cap bolts varies in different patterns. To each top cap there may be four top cap bolts, between which pass the side cap bolts; or the positions may be reversed, there being four side cap bolts carried on either side of a hous- ing, between which pass two king bolts. All these arrangements are included in McOnie’s patent (2444 of 1877). Fletcher’s patent (13397 of 1893) ar- ranges either the king bolts or the side cap bolts with slots, so as to allow one to pass through the other. The arrangement adopted in the majority of mills as now built is to cause the king bolts to converge from above the bedplate, as indicated in Fig. 81. claimed in Chapman’s patent (10469 the width of the trash turner and accommodation for larger journals without in- A similar result is obtained by adopting the form shown in Fig. g9, and also by flattening the bolts, as claimed crease of the apical angle. in Aitken’s patent (14647 of 1897). Any influence of the king bolts on the trash turner is eliminated by the use of U-bolts re- cessed into the housing, as indicated in Fig. too. This arrangement is due to McOnie (patent 2444 of 1877), but it is usually know man’s, from his patent (10369 of Ig00). in its effect on the removal of interference with the trash turner is the use of T-headed bolts, the heads of which co-act with the housing and terminate at a location above the trash turner. These designs, which call for the use of steel housings, permit of the bolts being far apart as desired, whereby a ram of wide diameter can be accommodated in th ellowing a decreased intensity of pressure on the ram. so as to meet at a point a little below This arrangement is specifically of 1894), its object being to diminish to obtain n as Still- Similar placed as e top cap, hydraulic FIG. 99 Complete elimination of both king and side cap bolts is obtained by McNeil (patent 6228 of 1912), who forms the housings with projections, which engage with counterpart projections cast on the caps, as indicated in Fig. Ior. by sliding. The removal of the caps is effected THE EXTRACTION OF THE JUICE BY MILLS 203 The Trash Turner.—The object of the trash turner is to direct the material trom the top and the front rollers to the top and the back rollers. In per- forming this function it acts in combination with the top roller, the lower por- tion of which, in combination with the trash turner, defines a passage through Fic. 100 which the material is constrained to travel. A second duty of the trash turner is that it acts as a scraper for the front roller. Evidently the setting of the trash turner is controlled by the quantity of cane or rather the quantity of fibre which has to be passed in a unit of time. An increase in the quantity of fibre necessitates a deeper passage, unless an undue pressure is to be exerted by the bagasse. On the other hand, if the bagasse is not compressed to a certain limit, it will lack the cohesion and compactness necessary to make it “‘ flow.” In its passage over the bar, power is absorbed in friction, and this absorp- tion increases as the width of the trash turner increases, or as the apical angle of the mill becomes flatter. Various designs of mills intended to Fic. 101 Fic. 102 diminish the width or to eliminate the trash turner have already been re- ferred to. The proper curve for the trash turner has been the subject of much dis- cussion. The following analysis was given by Bergmanns?® in 1889. 204 CHAPTER XI The duty of the trash turner in sugar mills is to direct the crushed cane from the first cylinder pair (one and two) to the second (two and three). The crushed cane must be so guided that cylinder 3 can take the feed without 0 stopping the working of the plant. Let TJ, represent the speed with which the crushed cane leaves the first cylinder pair and 7, that of the bagasse leaving the second cylinder pair (see Fig. 102) ; then must always T, = T,, and it hence follows that the passage of the bagasse over the trash turner must be uniform. Consider the movement of a point p (Fig. 103) ; using a system of polar co-ordinates the point p will reach A in time ¢ with a velocity V ; this velocity can be divided into two components Fic. 103 c and w, of which c is in the direction 3 of the radius vector and w is perpen- dicular to it. The crushed cane must move over the trash turner in sucha way that these components are constant, a result to be obtained by the following conditions :— If y and w are the polar co-ordinates of the point #, then dr & er: Orns r= 6 at. Now, since C is constant, one obtains by integration 7 =ct + C,. The value of C, is obtained by considering that when ¢ = 0, y must be equal to R. Using these equalities it follows that "Che i= 6h of a es (I) Further w= ae or w.dt=7.dau. The value of 7 can be obtained by substitution from (1) whence it follows that w.dt = (ct + R) du or w.dt es gop ae On integration ee = log (R + ct) + Gy The constant C, can be obtained by putting ¢ = o and u = 0, whence C, =~ log R. c Substituting this value of C, it follows that u=— log (R + ct) - = log R Reet R ee ee (2) w or 4 ns log THE EXTRACTION OF THE JUICE BY MILLS 205 Whence from (1) and (2) it follows that ae | 4 2 ames l Y Cc a a aa If, for simplicity, m be written for <, and if R be put equal to (1), this equation reduces to log r= m.u or r= e™ ae e oe (3) The equation (3) is none other than that of the logarithmic spiral where é is the base of the natural system. This curve has the property that the radius vector always makes with the tangent a constant angle; thus the angle aisconstant. Now (see Fig. 104), Fic. 105 and g= 90°-a then m= cot @= constant. Draw ON perpendicular to OA, and AN perpendicular to T. Then ON =rcota=rm. In addition NA =r ——. = ~~. YIt+m sina which the point # describes as a logarithmic spiral ; for sugar mills this curve is of definite length. The path, then, which the point # and also the crushed cane describes is. a part of a logarithmic spiral ; in order to obtain this path for sugar mills the velocities w and c must be known. The velocity w, which is perpendicular to the radius vector, is always equal to 7, the velocity with which the bagasse leaves the first cylinder pair. The velocity c is to be determined experi- mentally, and depends on the elasticity of the crushed cane, and that the cylinder 3 must easily carry forward the bagasse. Before determining empirically the values of c and of the angle a, we will look first at the following considerations :— In Fig. 105, S is the opening between the cylinders 1 and 2, and d is the thickness of the crushed cane, and when the cane is not elastic d is equal to S: in this case the velocity c can be put equal to O, for there exists absolutely no. reason why the crushed cane should proceed with a velocity ¢ lying in the Equation (3) gives the path 206 CHAPTER XI direction of the radius vector in order that it should easily and without excessive friction pass over the trash turner. Whenc = 0, malso = 0, and a =o. It then follows (= 0 = T= Rote = oO tame: ; : : ; D ; In this case the trash turner is a circle of radiusy = R = = + s, where D is the diameter of the roller cylinder. In practice such a condition never Fic. 106 occurs, due to the pressure between the top cylinder and the trash turner following on the elasticity of the crushed cane. This is why c must always be greater than 1. If c becomes too great, then the cylinder 3 cannot take the feed and will cause a stoppage. The velocity c must be such that the angle A is somewhat less than go”. The trash turner curve following this argument of Bergmans can be found graphically with close approximation as follows :— Draw the positions of the rollers to scale, Fig. 106; join OB and OC; draw KT parallel to OC ; draw KN perpendicular to KT, cutting OC at N ; with N as centre and NK as radius draw an arc KM ; then KM is very close to the original logarithmic spiral. Fic. 108 The trash turner itself consists of two parts: the bar, which is a permanent feature of the plant, and the knife or plate, which is renewable. The knife, a, is attached securely to the bar, 0, as indicated in two forms in Fig. 107. The bar runs parallel to the rollers from housing to housing upon which it is supported. As the bar may be treated as a beam supported at both ends and uniformly loaded, its longitudinal section should be a parabola, as shown in Fig. 108. Vertical stiffening ribs are also generally included. THE EXTRACTION OF THE JUICE BY MILLS 207 In the earlier designs the bar was supported on windows or apertures cast in the housings. The ends of the bar were made with a rectangular section, and the vertical and horizontal adjustment necessary was effected by inserting shims or packing strips. In order that the bar might be with- drawn laterally, the window was made deep enough to accommodate the bar at its maximum depth, distance pieces being inserted in, and secured by bolts to, the housing. In most mills of recent construction the rocking trash bar is adopted. This form is indicated in Figs. 109 and 110. The lower surface, a, of the bar is shaped to receive a shaft or axle, b, to which it is secured by means of a U-clamp, c. The ends of the shaft are carried in counterpart recesses arranged in movable blocks carried on chairs or stools cast on or secured to the inside of the housing. The horizontal movement of the bar is sub- stituted by an approximately horizontal movement obtained by the rotation of the bar about the:shaft, b; motion is obtained by the threaded rod, e, passing through the lug, /, cast on the side cap of the mill. Vertical adjust- ment may be made by means of shims, or more effectively by the use of the sliding wedge blocks shown at d in Fig. 110. With the exception of the rocking combination all these devices are contained in Watson’s patent (1606 of 1871), which has determined the type most commonly used. Another method of adjustment very largely employed is included in Fisher’s patent (U.S. 738629, 1899). As shown in Fig. 111, the rec- tangular ends of the bar are supported on rest blocks in windows in the housing. An upper rest block is formed with a journal, a, which receives the upper end of a lever, 6, which also engages with projections, c, on the end of the bar. Horizontal screwed rods, d, attached to the end of the lever co-act with ears, e, cast on the housing, whence by means of nuts the lever is moved, and a horizontal movement of the bar ensues. The opening in 208 CHAPTER XI the lever which engages with the projection on the bar is elongated to afford a vertical adjustment by means of shims or packing strips. The Trash Turner and the Fibre Volume.—The writer attempted to obtain some analysis of the trash turner, based on the results obtained from the behaviour of cane fibre on compression. His treatment was as follows.? Under pressures up to 60 Ibs. per sq. in. he found that the volume of bagasse varied as the2-5throot of the pressure. In the experiment of which the results are given on page 189, 0-221 Ib. bagasse with 32-6 per cent. fibre was compressed on a base of 8-43 sq. ins. This quantity corresponds to 100,000 Ibs. of cane with 12 per cent. fibre per hour, ground in a 78-in. mill at a surface speed of 25 ft. per min. The average value of HP®*, where H is the height of the column of bagasse in inches, and P is the pressure in lbs. per sq. in., was 4-8, whence H?-°P may be rounded off at 50. Let the projected area of the trash plate be a square inches, and let the mean height of the column of bagasse be H inches: then solving H#**P = 50 Fic. 110 gives the average pressure per sq. in. on the projected area of the trash plate, whence the total pressure on the trash plate is aP lbs. With settings such as are found in practice, it is sufficient to take H as the vertical distance from the lowest point of the top roller to the trash plate. With a mill of this size at rest, H is seldom found less than tr inch or I+25 inches, allowing a lift cf 0-25 inch when grinding at the normal rate. With H = 1-25, P is found to be 28-6 lbs. persq.in. The projected area of the trash plate with this drop in a 78-inch mill will be from 1,100 to I,300 sq. ins., depending on the vertical angle, so that the total pressure on the bar will be 31,000 to 37,000 lbs. Now let the trash turner be lowered until the drop at rest is I-50 inches, corresponding to a drop, when working, of 1-75 inches. P now becomes 12°3 lbs. per sq. in. If the distance of the trash plate from the back roller be kept constant, lowering the trash plate will reduce the projected area, which will now be 1,000 to 1,200 sq. in., so that the total pressure is com- puted to be 12,300 to 14,800 lbs. If the fibre in the cane increase, or if the quantity of cane milled increase, the pressure on the trash plate may be maintained constant by increasing the speed of the mills in proportion to the increase in the fibre passing in a THE EXTRACTION OF THE JUICE BYgMILLS 209 unit of time. Conversely, with an increase in the speed, the fibre passing being constant, the pressure on the trash turner will decrease. If, however, the fibre increases and the speed remains constant, the pressure will increase in accordance with the relation H?°P = C; for H, the quantity of fibre passing may be substituted, and, if the quantity of cane is constant, the per- centage of fibreinthe cane. For example, if with 12 per cent. fibre a pressure on the trash plate of 15 Ibs. per sq. in. is computed, with 15 per cent. fibre 25 the pressure will be (2) X 15 = 26-2 lbs. per sq. in. The power absorbed by the passage of the bagasse over the trash plate may also be computed. Let the pressure of the bagasse on the trash plate be 28-6 Ibs. per sq. in., and let the area of the plate be 1,200 sq. ins. The total pressure on the plate is then 35,500 Ibs. The coefficient of friction of bagasse on iron is about 0-4; then, if the speed of the bagasse be 25 ft. per min., the foot-pounds necessary to draw the bagasse over the plate are 35,500 X 0°4 X 25 = 355,000, and the horse-power necessary is 10°7. These results obtained by the writer are open to criticism, and have been criticised by Bolk,? not unjustly, and it may be remarked :— 1. The numerical values obtained in the calculation will vary with every mill, and especially are controlled by the value taken for the vertical angle of the mill. 2. The use of one constant for the bagasse in all the mills after a varying number of pressings is too broad. 3. No account is taken of the slipping action of the top roll when moving over the layer of bagasse. 4. The occasional fracture of trash turners shows that pressures much greater than those computed do occur. 5. Any choking of the bagasse on the plate entirely invalidates any conclusions that can be drawn. Q 210 CHAPTER XI The conclusions drawn by the writer were intended to be only general, and to apply solely to a layer of bagasse flowing uniformly over the trash plate without interruption. In actual operation it is doubtful if such a condition ever obtains. Pressure Regulators.—In a rigid mill in which the position of all the rollers is fixed by means of caps and tie-rods, any variation in the quantity of cane, or more strictly of fibre, passing in a unit of time, is accompanied by a variation in the pressure to which the material is subjected. If the quantity of fibre is less than corresponds to the mini- mum opening or clearance, the pressure tends to vanish ; and if the quantity increase in- Fic. 112 definitely, the mill will either choke, or a fracture of some part will occur, provided that the engine develops sufficient power. In rigid mills it is then necessary to keep the quantity of fibre passing as constant as is possible, and to control the setting and speed in relation to the quantity of cane desired to be milled. When the volume occupied by a unit weight of bagasse with a pre-arranged water content is known, the opening and the speed of rotation can be arranged to suit. Only a first approximation can be made, however, since, in proportion to the actual opening, the volume occupied by the grooving and the inequalities of the shells forms a very con- siderable percentage. In order that the disadvantages referred to above may be overcome, rigid mills have become largely a thing of the past. At present one roller of the mill is arranged to lift under a predetermined pressure. When, as is general, the top roller which coacts with both the lower rollers is selected as the moving element, the sum total of the pressures exerted vertically on the top roller is a constant, whatever is the quan- tity of cane passing, provided sufficient is passed to cause the top roller to lift. As explained elsewhere, however, the distribu- tion of the load as between top and front rollers, and the top and back ones, will vary with every variation in the feed of cane. The necessity of this pressure regulation, which also acts as a safety device, was recognised at an early date. The first edition, 1855, of Richardson’s “Chemistry as applied to the Arts and Sciences” figures a mill invented by a Demerara engineer, Moore, and built by Pontifex & Woods, in which the front and back rollers were free to slide outwards, being maintained in position by a system of weights | and levers. This device appears in a number of early American patents and a PIG? 1b3 THE EXTRACTION OF THE JUICE BY MILLS 2x1 at a later date in Brullard’s U.S. patent (422289 of 1890), shown in Fig. 112. The writer knows of a mill operating over a whole crop with a makeshift arrangement similar to this, on the occasion of a locally irrepar- able accident to the hydraulic system. Hydraulic pressure, the system adopted in nearly all plants of recent date, was first suggested by Jeremiah Howard (U.S. patent 21340 of 1858). His design, of very considerable interest, is shown in Fig. 113. It is to be observed that the pressure was obtained by a pump, a, driven off a mill roll, and that a safety valve, 4, released the pressure at a predetermined point, no accumulator being employed. - The introduction of the hydraulic really dates from Stewart’s patent (3269 of 1871) and from McDonald’s patent (U.S. 128235 of 1872). As designed in both these inventions, the pressure is obtained from an “ ac- cumulator,”’ shown in section in Fig. 114. Se ee Puryp Hi ee Fic. Ir4 This device consists of an upright hollow rod, d, which communicates with a force pump. This rod also communicates with the cylinder, 6, which supports a number of removable weights, c, on the flange, &. When oil or other fluid is pumped into the cylinder from the pump, a, through the pipe, e, it will eventually raise the weights from the flange, and the pressure in the system will be that due to the weights. Ifthe pipe e is continued so as to communicate the pressure to rams bearing on the brasses area rams area cylinder supported. When the bagasse in its passage exerts a pressure equal to this, the roller will lift, and, when once the roller has lifted, the pressure exerted by the bagasse and on the bagasse is constant. The location of the rams varies. Stewart placed them preferably acting directly on the back roller, while McDonald arranged them underneath the mill and operating on the top cap through the king bolts, as shown in of the rollers, the pressure exerted on the roller is x weights 212 CHAPTER XI Fig. 115. This arrangement was followed by American firms until recently. At the present time the hydraulic is almost always placed in the top cap, and is designed with regard to accessibility. Such an arrangement is shown Fic. 115 stalled on one side only. in Fig. 116: A is the top cap of a mill, in which is formed the aperture B; the top of this aper- ture is closed by an easily removable “ plug cover ’’ ; the form shown employs an interrupted screw thread, and is known as the breech block type. By means of a quarter turn the cover may be lifted from the cap. C is the fluid chamber, filled by a pipe in communication with the accummulator. D is the ram bearing on the upper brass, F, of the top roller. FF shows the U-cup leathers forming the hydraulic joint. Various other devices are employed to make a _ A tight joint in the plug cover. Accessibility may also be obtained by inserting a distance piece longer than the ram between it and the top brass, so that if the distance piece be slid out the ram falls, and may also be removed by sliding. In modern practice the pressures exerted reach up to 500 tons in a seven-foot mill, and correspondingly less in smaller plants. An irregularity in the use of hydraulics is the unequal pressure on either side of the mill caused by the thrust of the pinions when these are in- This may be compensated for by making the rams of unequal size, or by employing independent accumulators for either side, less pressure being applied at the pinion end than at the other end. Another pressure-regulating device which has been and is very extensively employed is the “ Toggle gear ’’ of Hudson (13102 of 1887), shown in Fig. 117. The toggles act between the top roll cap and a yoke connecting the upper ends of the king bolts. The toggles are connected by hori- —S— zontal bars, upon which the su- perior or inferior ends of the toggles play. This bar also carries the con- volute spring, constrained and When at rest the toggles assume a vertical position, becoming forced out- wards against the pressure of the spring when the top roll lifts. The actual pressure exerted is con- trolled by the compression of the springs, and increases with the lift of the roller. This device eliminates trouble with the hy- controlled by the nuts. draulic leathers. 1EgKeguatids: THE EXTRACTION OF THE JUICE BY MILLS 213 Bagasse Conveyors.—The bagasse is usually conveyed from mill to mill by steel slat endless belts operated by a chain and sprocket drive off a lower roller of the mill. An alternative method employs a scraper conveyor operating in combination with a water-tight trough. Strainers.—The fine particles of fibre which are carried down with the Juice are separated therefrom by brass or copper strainers, the holes in which are usually about 1-32nd inch in diameter. The strainer, Fig. 118, is usually arranged as a narrow deep trough, a, parallel with the mill, and is partitioned so as to collect the juices from the various mills separately. Over the surface of the strainers run wooden or rubber-faced scrapers, 6, which finally elevate the ‘“‘ cush vat cush ”’ and discharge it to a screw conveyor, c,qq{7 i running parallel with the rollers, and behind the pit first mill. This method is indicated in Fig. 118. A different type of strainer, operated by the fall of the juice, is shown in Fig. II9. Roller Serapers.—The bagasse adheres te- naciously to the rollers, especially those of the later mills. They are kept clean by scrapers, a, arranged as indicated in Fig. 120 ; this method is includedin Flower’s patent (U.S. 389801, 1888). FIG. 117 The Gearing of Mills —The motion from the crankshaft of the cane engine is transmitted to the top roller of a mill, or of a series of mills, by spur and pinion gearing. The limits of the speed of the engines are 35 to 55 1.p.m., 45 r.p.m. being very general practice. The train of gearing reduces the number of revolutions in the ratio of from 20 to 25: I so as to cause the mill rollers to make about 2 revolutions per minute. The train of gearing is now always compound, and such was first used at the beginning of the 1gth century. There are still in operation, however, some single trains with the spur wheel as much as 3oft. in diameter. Fie. 118 When two or more mills are connected, the train of gearing may be open or compact. When open, as-shown in plan in Fig. 121 for a 6-roller mill, a greater distance is obtained between the units, opportunity thus being given for the application of “‘ bath’’ -maceration.. ‘Generally; however, the gearingis-arranged»as indicated. in, f7g. 122, as applied 40, a grroller: train. Incthese diagrams, 4 represents the first motion pinion ;~ 2, the first- motion 214 CHAPTER XI spur wheels ; 3, the second motion pinions ; and 4, the second motion spur wheels. A common modification of this train is to make of double width that second motion pinion coacting with two spur wheels, so that the double Strainer Screen Juice /nle* Trash Chute Hovs 171: oe e Sauned Juce Fit Juice Oultel Fic. I19 load may be distributed. When four or more mills.are laid out in one train, two engines are generally used, practice being divided between driving the mills three and one, or two and two. . In the earlier g-roller trains the second motion spur wheels were carried Fic. 120 on high pedestals, as indicated in elevation in Fig. 123, stability being aided by tying the pedestals together. As fracture of the pedestal was frequent, it is customary at present to arrange the centres of spur wheels and pinions THE EXTRACTION OF THE JUICE BY MILLS 215 in the same horizontal line, as in Fig. 124. Connection from the end of the main spur wheel shaft to the shafts of the top rollers is made by a distance piece and coupling boxes, as shown in Fig. 125. To allow play for the top roller, the coupling boxes only very loosely envelop the shafts and distance pieces. The top roller shaft carries a pinion, engaging with pinions on the shafts of the lower rollers. It is not generally customary at present to carry pinions on the end of the mill shafts remote from the engine. As a modi- fication the mill roll gearing may be carried on the reduction gear bedplate, oo to each roller being made by separate distance pieces and coupling xes. The train of gearing described above is almost universal. Various patents include internal-geared spur wheels; Robinson, 851 of 1853, 2065 of 1809; Caird and Robertson, 3066 of 1867: bevel gear, Wilson, 2754 of MO TT} TO S| 2 1861: worm and wheel drive, Halpin and Alliott, 2039 of 1873; Webb, 3747 of 1869: pitch chains, Rousselot, 5050 of 1876: helical teeth, Watson, 1324 of 1877. The Motive Power of Milling Plants.—Putting on one side the exceptional cases where water power is available, and neglecting those districts where cattle power is still used, steam power may be regarded as the only prime mover to be considered. The earlier British patents all show a vertical engine as the type employed. The beam engine is shown for the first time in Robinson’s patent (2065 of 1859), and this type was installed by Scotch firms as standard till about 1890, after which date horizontal engines are found. American practice introduced the Corliss engine, and the use of this type remains standard practice with U.S. firms. British firms, though building this type, seem to incline rather to the piston valve engine. The introduction of the steam turbine as a prime mover dates from 1913, when the ‘“‘ Amistad ’’ factory in Cuba was “ electrified.” Since then no inconsiderable preportion of new installations have adopted this method. 216 CHAPTER XI In these installations the prime mover has been a non-condensing steam turbine, making about 1,800 r.p.m., direct coupled to a dynamo the current from which drives a motor making 450 r.p.m. The motor in turn drives through herring-bone spur and pinion gearing, with a gear ratio of I: 10, what corresponds to the first motion pinion of the ordinary steam-driven train. It is easy to see that the combination of dynamo and motor forms nothing else than a reducing gear, to which has to be added the first motion spur and pinion gear before the system is reduced to the first motion pinion of the steam drive. Considered in this light the arrangement appears to be a rather expensive train of gearing. As regards the steam consumption, the latest tests give ie WN a ey He ET HL a Ge a TOC OT x aa NA as 111 NLDA AN ti TOT TU COCO WT Tr ITT Uh eT 0008 HI a distinctly higher rate to the non-condensing turbine than to the non-con- densing Corliss engine in units of the size installed. | The determinations approximate to 33 and 30 lbs. of steam per indicated horse-power-hour. To the difference between these figures is to be added the power lost in the electric reduction gear. This is taken as 8 per cent. in both dynamo and motor, and 2 per cent. in the wiring, so that only 83 per cent. of the power represented by the steam turbine reaches the second motion pinion of the train of gearing corresponding to the first motion pinion of the steam drive. Allowing for the increased consumption in the turbine, it would then follow that about 30 per cent. more steam must be delivered to the turbine than to the Corliss engine. Another factor tends to increase the steam,,con- sumption. The prime motor driving a milling plant must be capable; for a limited period of developing power much above the normal load. The regulation of the electric machinery is by means of an external resistance, THE EXTRACTION OF THE JUICE BY MILLS 217 and hence, except when running at the maximum capacity, some power is lost here. As opposed to this source of loss, the steam consumption per horse-power is in a Corliss engine sensibly constant over a wide variation in the power developed. However, if the house is able to take up all the exhaust steam produced, there need be no heat loss here except that repre- sented by “cylinder condensation,” a source of loss which is probably a little less (as a percentage of the steam used) in the turbine than in the reciprocating engine. There are, however, a number of advantages connected with electric drive, which may be briefly summarized :-— FIG. 123 1. Absence of all oil in the exhaust. 2. Compactness of plant and decreased cost of foundations. 3. More extended control by means of recording watt-meters, this being possible only with electric drive. In certain plants individual motor drive has been installed for each unit of a train of mills. The executive can detect at once any variation from the proper amount of power taken by any unit of a train, and by means of the recording instruments can reconstruct the operation of the plant over any period. It is this opportunity for a complete control that appeals to the writer as the great advantage of the electric reduction gear. Milling Trains.—Originally, and up to comparatively recent years, _ only one mill was employed, and the introduction of a second unit (double crushing) without the intermediate addition of water did not in any way alter the principle of the process, which remained one of dry crushing. In a sense, Robinson’s multiple roller mills (see below) form a train, and the first instance of a single engine double-crushing plant is probably that erected by Don Wenceslao Urrutia in Cuba in 1843," and condemned because. it spoilt both juice and bagasse. At about the same time a three- roller mill, followed -by.a two-roller with the.addition of water, was im use in Province. Wellesley, and. is illustrated. by Wray in the.“ Practical: Sugar, Planter.’’ (1848). : — 218 CHAPTER XI The first patent on a train of mills or “ tandem,” the term used in Cuba, appears to be found in Rousselot’s patent (5050 of 1876). His design con- sisted of a three-roller followed by two two-rollers, the first mill being driven off the engine and the two last by pitch chains. In his patent 2280 of 1878 the pitch chain drive is changed to spur and pinion gearing, one engine only being used ; this combination was also patented by Dale (92 of 1885). The modern multiple milling train driven by one engine dates from 1892, when a 9-roller single engine mill was erected by the Fulton Iron Works at the Cora plantation of the New Iberville Planting Co., in Louisiana. In districts where American influence was dominant, this rapidly became the standard type with new construction. In various places, especially where capital was scarce, g-roller trains compounded of already existing units, each unit being separately driven, were erected. These plants may be defined as g-roller trains in operation, but not in design. Perhaps the first 12-roller train was that installed at the Oahu Sugar Co.’s mill in Hawaii in 1906, and formed by the addition of a unit to an existing g-roller train. The success of this change was so very marked that other installations followed. In 1910 the Ewa Mill in the same locality converted two 9-roller trains into a 15-roller train, and eventually into an 18-roller one. FIG. 125 In recent practice the crusher and g-roller mill are regarded as ineffi- cient. The tendency in Hawaii has been towards the crusher, swing hammer shredder, with or without the use of knives, and 12-roller mill. In Cuba the later mills have adopted the double crusher, followed by fifteen or by eighteen rollers. The writer is inclined to attach importance to the dis- integration of the cane obtained with the swing hammer shredder, and be- lieves that the Hawaiian scheme is better as regards power required and ex- traction obtained, while it is not inferior as regards capacity. The Capacity of Mills.—By the capacity of a mill is indicated the quantity of material which can be treated in a given time. This is usually stated as so many tons of cane per hour, but the capacity should rather be expressed in tons of fibre per hour. The capacity of a mill or milling plant will also be affected by the efficiency which is demanded of it, and, given a certain quantity of power available in the engine, it is possible from the experimental results given earlier in this chapter to correlate tonnage ground with the percentage of fibre contained in the bagasse after milling. Again, the capacity of the plant will depend on the view point of the operator. In some districts a milling plant is regarded solely as a means of grinding cane, in others as a means of extracting sugar from the cane. If conditions exist such that the cultivation has outgrown the factory, relatively large capacities result due to the necessity of taking off the crop. Conditions THE EXTRACTION OF THE JUICE BY MILLS 219 such as these obtain in Cuba, and are naturally combined with a lower efficiency at the mills. The reverse condition, namely, a cultivation which has reached the limit of its extension, obtains in Hawaii, and here are found lower capacities combined with the maximum of efficiency. . In one and the same milling plant the means available to increase capacity is principally an increase in the speed of the mill, whereby the grinding surface developed in a unit of time is increased. This, of course, implies higher engine speed, and the development of more power, which is the ultimate factor controlling mill capacity. Other factors of influence are the roughness of the rollers as affecting slippage, the setting of the trash turner, the care taken in feeding the cane to the mill, and the means adopted in preparing it for milling. Minor factors are details such as the angle of the crusher, of the carriers, and of the feeding shoots. As regards the actual recorded capacities of milling trains, as dis- tinct from a mill, a study of a very large number of results on record of nine, twelve, fifteen and eighteen-roller plants, preceded by efficient crushers, has led the writer to the formula :—Capacity = 0-005 ” /? d* tons fibre per hour, where 2 is the number of mills in the train, / is the length, and d the diameter of a roller ex- pressed in feet. Values of this expression, which has no rational ‘basis, and is entirely empirical, are given below. If besides capacity the eco- nomics of high efficiency are considered, it will be reasonable Fic. 126 to obtain this end with longer trains, rather than with larger units, because of the opportunity afforded for compound maceration. VALUE OF 0°005 1/2? d? OR CAPACITY IN TONS FIBRE PER HOUR. l d Et: ft. = 3 4 5 6 5; 9 2°5 2°33 3°H1 3°87 4°65 5°0 2°67 2°65 3°56 4°45 5°34 535 2°67 3°21 4°28 5735 6:42 6-0 2°67 - 3°84 5°12 6-40 7°68 6-0 2°83 4°32 5°76 7°20 8-04 6°5 2°83 5°07 6:76 8°45 10-14 7°O 2°33 5°88 7°88 9g: 80 E1*76 7°O 3:0 6-61 8-82 II-02 13°23 The Stresses on the Three-Roller Mill.—In Fig. 126 let the three circles represent the three rollers of a standard three-roller mill, of which the ver- tical angle is a. Let the cane pass from left to right. Let the pressure exerted on the layer of bagasse in its passage between the top and front roller be #, and let that between the top and back roller be x f. Let these pressures act through the lines joining the centres of the rollers. Along B A produced lay off A D = p. Resolve A D into vertical and horizontal 220 CHAPTER XI components, namely A Fand AG. Along C A produced lay off A E =n, and resolve A E into vertical and horizontal components, namely A H and A K. Along A H lay off H L = A F, and along K A lay of K M =A G. Complete the parallelogram A M N L. Then AN is the resultant of the © forces p and f, 1n magnitude and direction; A L is the vertical com- ponent of forces # and 1p, and A M is the horizontal component. e bse © Geer s a ee Now AF = pcos aa p (a and AH = np COS npr tees whenceAL= AH+HL=AH+AF=(p + np) s[-+ cos ¢ If the hydraulic pressure act on the top roll and is V, = (p + mp4 +SS* or p + np = /2V (n+ I) Vr+ cosa whence, whatever the ratio of # to mp, or whatever the settings adopted, the sum total pressure exerted perpendicularly on the bagasse is constant when V and a are constant. As a decreases, i.e., when the vertical angle becomes steeper, cos 4 increases ; hence, with decrease of the vertical angle the hydraulic load or value of V must be increased to keep the value p + up the same. The problem which presents itself in this connection is :—What is the /2V VI + cos a be 50 tons, when up will be 450 tons and x = g. With a different setting p may be 100 tons when mf = 400 tons and m = 4. So far as the writer is aware, there is no very definite information on this point ; in other words, the problem resolves itself into the question whether the front roller is to be regarded as a feeding roller and the back roller as a crushing roller, or whether the front roller is to be regarded as a crushing roller also. In the latter case the values of # and zp tend to approach each other, but the maximum single pressure obtained decreases. This problem may also be expressed as the question :—-Will better results be obtained by two crushings at a lower intensity, or by one very light one and a second very heavy one? The ex- periments of the writer quoted earlier point to the obtaining of better results when # and up are equalized as far as possible. /2V VI + cosa + cos a and p= best value of ~? For example, let = 500 tons. Then p may Again AK =np sin = meee and AG = sin =p) am a. whence AM Ale Ae ga) ee and hence AES = p (n—1) and p= eau / I— cosa (n—1) V I— cosa But H is the horizontal component of the forces p and up pressing the top roller against the brasses on the feed side of the mill, often referred to as the side thrust. When x =1 or p = np there is _no.side thrust, and, the side thrust increases as ” increases and as increases; that is to say, as the vertical angle becomes flatter. THE EXTRACTION OF THE JUICE BY MILLS 221 A steep vertical angle, then, while calling for a narrow trash turner, and decreasing the intensity of the side thrust, calls for an increased intensity of the hydraulic pressure to maintain the same pressure on the bagasse as is obtained with a flatter vertical angle. The magnitude of the resultant AN or R and of the horizontal component H can be obtained in terms of V, the hydraulic pressure, thus :— (AN) =(AM)* +(AL)*=(p (2 —a)fF—8 *) 4. (p(w + a) pee =p? (pf? +1+2 n cos a) But AN = Rand} = ee a eA a a (n+1) V1r+cosa ee V2V V/n?+1+2nCos4 (n +1) V I+ cosa Also (A M)? = (A N)? —(A L)?, where AM=H, AN=R, and AL=VJ; whence ip? V? (n?+1-+2n cosa) _ yp (n+1? (I +-cos a) __ m—an+1—cos a (n*@—2n-+1) (n+1)? (I-+cos «@) _. (n—1)?—cos « (n—1)? ~~ (w—1)? (1-++cos a) __ (n—1)V1I—cos a (n+1) V1+cosa Finally, the resultant R makes an angle, ®, with the horizontal such that Vi n+IV1-+cos « H n—IV I—cos a The Actual Pressure on the Rollers.—In a mill controlled by hydraulic pressure, the actual pressure exerted on the rollers by the bagasse in its passage is, of course, controlled by the hydraulic load and by the vertical angle. = ie emergent from the top roller and Distance trom fine of nearest appr cach! = 2irnches the back roller. This material con- Frc. 129 sists of a solid residue, fibre, and a fluid residue, dilute guice. Thesolid material is unalterable as regards its abso- lute volume ; and hence the volume of the fluid residue must be that of the escribed volume Jess that of the fibre. This reasoning gives a preliminary basis upon which the necessary opening in rigid mills may be determined. [For example, let there be a rigid mill, 30-in. x 60-in., making two revolutions per minute, and let it be desired to mill 30 tons of cane containing Io per cent. of fibre per hour. The emergent bagasse is to con- tain 45 per cent. of fibre and 56 per cent. of juice, the densities of those materials being taken as I-35 and 1I-o respectively. The volume of fibre passing per hour is :— 224 CHAPTER XT 3 X 2000 62°25 °X) 1°35 and that of the juice is = 71°30 ¢. ft., 3°66 X 2000 62°25 X 1-07 In all, the total volume of residue passed out is 182-27 c. ft. per hour, or 3038 c. ft. per minute, and this must be equal to the escribed volume. At two revolutions per minute the area developed in one minute by a line on the roller equal to its length and parallel to its axesis™ X 2 X 2°5 X 5 = 78:56 sq. ft. Then if x be the opening necessary 78-56% = 3-038, whence x = 0:0387 ft. = 1% inch. This calculation assumes that the rollers are smooth; actually not only are they grooved, but also the cavities in the metal occupy an ap- preciable volume. Hence a setting closer than this will be adopted. It also follows that the setting will not increase in direct proportion to the quan- tity of material to be passed, but will partake of the relation a4: b= K + d,: K + dy where a and b are the quan- tities of material passed, d, and d, are the open- ings, and K is the con- stant volume of the groovings and cavities, In rigid mills, after the setting has once been made, in order to obtain uniform results, Fic. 130 the quantity of fibre passing in unit time should be unvariable. If the quantity of fibre offered to the mill increases, the rollers must be operated at a higher surface speed, in order that the necessary escribed volume be developed. If the bagasse is to remain of unchanged composition, the increase in speed must be directly proportional to the increase in fibre. This statement resolves itself into increased engine speed and increased consumption of power in direct proportion to the fibre operated on. If, however, the surface speed of the rollers remain unchanged, there must still be an increase in the power developed to reduce the greater quantity of material to the constant volume, and this power will be obtained by increase in the mean effective pressure on the piston. In this case, however, with the escribed volume constant and increased volume of fibre, there will remain a less volume for the juice to occupy, and there will be a less quantity of juice in the bagasse. Accepting the applicability of the experimental results discussed earlier in this chapter, this condition would only be obtained = I10:88. THE EXTRACTION OF THE JUICE BY MILLS 225 by the consumption of power much in excess of that computed proportionally to the quantity of fibre milled. : A different set of conditions obtains when the mill operates under a con- stant ioad, as af- forded by the hy- draulic gear. Evi- dently in this case the power consumed varies always in proportion to the quantity of fibre passing, since the opening between the top and back Fic. 131 roll adjusts itself automatically. In order that the mill should accommodate itself to the passage of an increased quantity of fibre, more power must be developed by an increased speed, or by an increase in the mean effective steam pressure. In the first case the thickness of the blanket of bagasse may be maintained constant, and in the latter it may increase in depth propor- tionate to the quantity of fibre passing. Eventually, when the engine has developed its maximum power, more cane capacity can be obtained by decreasing the hydraulic load. The above discussion has only treated of the compression of fibre as be- tween the top roll and the back roll, and has neglected the action of the top roll and front roll, the friction on the trash bar, the crushing effect between top roll and trash bar, and other minor influences. The results obtained in milling depend not onlyon the top and_ back roller setting, independently of each but on this acting in combination with the top and front roller setting, — other ; and for every alter- ation in the position of either front or back roller relative to the top roller there will be a different consumption of power. and, again, different con- ditions arise dependent In an hydraulic mill, however, the sum total pressure exerted on the bagasse is constant, and the problem the engineer has to consider is how rigid or is operating under a constant hydraulic load: In the former case, what has been said with refer- ence to top and back roll applies equally to top and front roll, and the power required to operate the mill will be the sum of that required to operate the top and front and top and back roller, considered Fic. 132 on whether the mill is R 226 CHAPTER XI to divide this pressure so as to obtain the best results. Evidently the greatest intensity of pressure will be obtained when top and back rolls are set metal to metal and when top and front rolls are set as far apart as possible. The converse arrangement would be to equalize the settings and obtain equal pressures as between top and front and top and back rollers. Practice in the Hawaiian Islands inclines to obtaining a greater intensity of pressure, treating the top and front roller as a feeding combination. In Java an opposite opinion holds, and it seems to be considered good practice to equalize the pressures as far as possible. Connected with the question of setting is the speed of opera- tion which determines the thick- ness of the blanket of bagasse. In a rigid mill given a constant Fic. 133 escribed volume, calculation would always indicate the same composition in the bagasse, independent of speed. The Java practice however, inclines to thicker blankets of bagasse and slower speeds, generally 14 to 15 feet per minute. Hawaiian and Cuban practice has adopted higher speeds, reaching up to a maximum of 30 feet per minute. Below are collected certain typical mill settings. The variation between them is so great that perhaps they reflect nothing more than the personal equation of the engineers responsible. HAWAITAN AND ONE JAVAN* MILLS, ALL 78-IN.X 34-IN. OPERATING ON CANE PREPARED BY ONE CRUSHER, AND WITH ALL MILLS UNDER AN HybDRAULIC LOAD OF CIRCA 450 TONS. Tons ROLLER SETTINGS, INCHES. ; SURFACE SPEED, FT. PER MIN. FIBRE If ete hae IV. iT iItip ITT. IV. Perhour Front. Back. Front. Back. Front. Back. Front. Back. 5°7 rt ts 3 1 3 oO 3 fo) 20 21 22 23 Fou 3 4 as is oO i fo) 21 18 20 22 Oy aera: a ade i Ber os a 7 see OTS 5°4 1} t = $ fe) 3 fo) 19 19 20 18 7550 I 3 z 3 3 t 3 is Tons TRASH TURNER SETTINGS. INCHES BELOW TOP ROLLER. FIBRE it IJ. III. Vis Per hour. Toe. Centre. Heel. Toe. Centre. Heel. Toe. Centre. Heel. Toe. Centre. Heel. OM. Tee es ane OS I ee eae eke wiemeee wake? eee eee | a ey Se? 2 i & 2 ohio ne ae ee oe en a ee ee i Mer can es oe a ee ee 5:0 2 2 1% ue Javan Ricip MILIs, 60-IN. X 30-IN. OPERATING ON CANE PREPARED BY ONE CRUSHER, AND AT A SURFACE SPEED OF CIRCA I4 FT. PER MIN. Tons ROLLER SETTINGS, INCHES. DISTANCE CENTRE OF TRASH TURNER FIBRE FROM ToP ROLLER, INCHES. 1 i Jig Te Tait ie 1B TE Perhour. Front. Back. Front. Back. Front. Back. 5 i t + i 3 3 t 24 2} 2 3°5 It 5 Ive 3 I 3b — == == 4°3 iF Iie I 4 = a= = THE EXTRACTION OF THE JUICE BYJMILLS ~ F 227 _ Multiple Roller Mills.—Robinson took out a patent (8731, 1840) for a 4-roller mill, with the three rollers arranged round the circumference of a fourth central roller, which was twice the diameter of any of the others, this central roller Z- U7) GN being the driven roller, which in Se pS ee turn drove the other three. The Hy Sa ae Same _ arrange- ment forms the ate essential part of eu SOS Le Blanc’s patent (5404 of 1883), Of f Pali : Fig. 130; anda 7 AN fy IES central or “ pri- Eee ee: 3a AY mal”’ roller, with ere ea if up to twelve , e a> y smaller rollers ar- ; ' (yy a ls ranged round it X das Re in various com- binations, forms 181 m the subject of patents granted = to Guy (7725 of a 1887; and 2416 |L_— of 1890). The addition of a fourth roller as a feeding roller appears in Guy’s patent (7745 of 1885) and Lateulade’s (12208 of 1892). Robinson’s patent (8731 of 1840) also claimed a 6-roller unit, the three upper rollers being vertically over the three lower rollers. In mills of this type, Fig. 131, the driven rollers are the two middle rollers, 3 and 4, the latter of which gears with and drives rollers 2 and 6, these driving rollers 1 and 5. The gears are mounted on opposite ends of the shafts. Patents for construction similar to this have been granted to Hosack (2316 ot 1869) and Cail (2212 of 1870). Amill of this type with eight rollers was erected in 1884 at Courcelles in Guadeloupe by Brissoneau and La Haye. Robertson and Hudson’s patent (602 of 1887) preferably included four rollers, Fig. 132. The driven pinions were carried on a separate shaft, 5, gear- ing on one end with roller 2, which drove roller 1, and on the other end with roller 4 driving roller 3. A multiple roller mill with an odd number of rollers was patented by Rousselot (2572 of 1887), by Deacon (15976 of 1888), by Guy (2796 of 1891), and by Hughes (U.S. 395837 of 18809). All these are essentially the same, and are indicated in F ig. 133. The drive was from the lower central roller, 1, which geared with the two upper rollers, 2 and 3, which in turn drove the two outer lower rollers, 4 and 5. This Fic, 134 228 CHAPTER XI arrangement is also seen in Payen’s mill, referred to in books of -date | about 1850. alae The De Mornay patent is 13709 of 1851; the improved form due. to Chapman (4209 of 1888) is shown in Fig.. 134, and of this a number have been built, some still remaining in operation. In most of these patents it is easy to see that the conception of the patentee was to improve the extraction of the mill, the idea of the train of mills not having then been conceived. The Two-Roller Mill—The 2-roller mill, as shown in Fig. 135, followed the 3-roller, and was brought out as a re- pressing or macerating mill, and also with the object of eliminating the trash turner. Chapman’s patent (4411 of 1875) claimed the 2-roller mill in con- nection with Russel’s maceration scheme (4094 of 1874), and a very similar patent was taken out by Rousselot (5050 of 1876). Inalater patent (2280 of 1878), Rousselot added a small feed roller to the 2-roller, as shown in Fig. 136. At the same time the 2-roller mill was developed by Alexander Young in the Hawaiian Islands. ' Difficulty in feeding whilst maintaining the pressure prevented the adoption of this type. To overcome this trouble the forced feed of Riley (patent 17776 of 1891) was tried, Fig. 137. In this device a reciprocating pusher. bar, a, is driven from an eccentric or crank through a rocking shaft 0, and forces the bagasse into the mill. Very similar arrangements were patented later by Fletcher (16118 of 1892) and Kidd (15301 of 1893). The 2-rolier mill has disappeared from modern practice, and a number which were installed are doing duty as crushers. Preparation of Cane for Milling.— ~ The cane may be considered as a hollow cylinder reinforced by trans- verse partitions (the nodes). Such a structure is well adapted to resist an external pressure. Rupture of the cylinder, combined with a ren- dering of the cane into a fine state of division, is the object of the de- vices used to prepare the cane for milling. These devices may be classed as saws, knives, shredders, Fic. 137 crushers, and hammers. The first- named class has never come into extended use, and at most has been applied only in isolated cases, The earliest British patent on this matter was issued to Blanchard ee ee THE EXTRACTION OF THE JUICE BY MILLS 229 (753 of 1858,) who claimed a system of saws on parallel rotating shafts, the saws on one shaft acting in the spaces between the saws on the other. A patent on a similar principle was granted to Easton and Hoyland (642 of 1888). Bonnefin’s apparatus (1185 of 1877) consisted of a gang of parallel saws alternately raised and drawn across the canes, which were presented to the action of the saws ina cradle. Another system of saws, patented by Reynoso Fic. 138 {1555 of 1875 and 1492 of 1877) included a drum, on which was mounted a series of staggered or drunken saws, set oblique to the axis, so that on rotation-the system. formed virtually a continuous circular saw. The first patent on knives as a preparatory device is that of De Coster (192i of 1854), who employed a rapidly rotating disc carrying knives or cutters, and this device in various forms remains in use. C S S Wy ATED HN é ( \\ Kc ey NW LIIWXW\\\ AM WU ‘\ Yi Tey = Gt wr eaeres), Bl). <7 SA AY Fic. Such asystem, shown in Fig. 138, consists of a horizontal shaft, on which curved knives are arranged spirally and rotate in a vertical plane. Besides slicing the cane, this appliance serves to beat down and to level the matted mass of material, thus aiding in maintaining an even feed. The shredder is a torsion machine, which actson the principle of passing the cane between two surfaces moving at different speeds. The effect of this is to 230 CHAPTER XI twist the wall of the cylinder, separating the fibro-vascular bundles which make up the wall and destroying the resistance to external pressure. The first patent of this type is due to Faure (3003 of 1879) who employed a rotat- ing drum, on which was cut a series of helicoidal teeth operating in com- bination with a fixed counter plate set eccentric on the drum. Shredders as actually used, however, have employed two drums, co-acting with each other, where the upper drum revolves at a higher rate of speed than the lower, the revolutions per minute usually being about 135 and 35 respectively. This system was patented by Cail and Ferron (379 of 1883), who formed on the drums helical threads, the section of which was a right-angled triangle, the threads on the upper cylinder running in the opposite direction to those on the lower. “8 on a 2 agg . aaa The form of shredder which has been most commonly used is indicated in Chapin’s patent (2553 of 1885) and in Hungerford’s patent (U.S. 346817 of 1886). This patent claims a shaft on which are arranged rings or annular discs, the peripheries of which are bevelled off on both sides at 45°. The rings are pitched so that the rings on one shaft intermesh, but do not meet, with the rings on the other. This type of shredder is shown in Fig. 139. The successful use of the shredder seems to be due to the housing patented by Fiske (13955 of 1887). This is shown in Fig. 140. It combined with adjustable upper and lower bearings a and } the control of the pressure by a spring, c, so that the upper roller was free to move if the feed became too heavy, or if a piece of iron or other foreign matter entered. A patent granted to Kidd (15297 of 1893) includes the above two devices with only small differences of detail. The crusher as a preparatory Fic. 140 device was distinctly introduced by Thomson and Black in their patent 2586 of 1882, and is often included in the term “ 5-roller mill.’”” They extended the housings of an ordinary 3-roller mill to receive an ad- ditional pair of rollers, on which were formed a series of circumferential deep grooves and ridges. The ridges in one roller operated in the grooves of the other. This type of crusher is often referred to as “ splitting rollers,’ and it remains a very extended design. A crusher which has been and is still very widely used is that due to Krajewski (patent 12012 of 1886), Fig. 141. It claims the combination of rollers with more or less sharp zigzag corrugations in the direction of the rollers, the teeth of one intermeshing, but not coming into contact, with the teeth of the other. The action of this device both crushes the cane and cuts it into small pieces. The cutting action is dependent on the setting of the rollers. Another type of crusher is that due to Marshall (U.S. 584183, 1897), shown in Fig. 142. Crushers of the above-mentioned types have come to be regarded as an THE EXTRACTION OF THE JUICE BY MILLS 231 essential part of the train of mills. Their object is not so much to extract juice as to prepare the matted mass of cane for subsequent milling, presenting an even, level, disintegrated blanket to the first mill of the train. Their introduction into Cuba was based on increase in capacity afforded to existing plants rather than on any increase in the quantity of juice extracted. It is for the same reason that the double and even the triple crusher has been very lately introduced into that island. The hammer was the original preparatory device, as shown in Curtis’s patent (13014 of 1850), which proposed the use of hammers falling vertically upon cane supported on an anvil. Searby’s patents (U.S. 1146464 and 11850093, I9g16) adapt the swing hammer to the disintegration of cane. This device, shown in Plate XXIII, includes a horizontal shaft, to which are attached a series of loose hammers arranged six in any vertical plane. The hammers are ;°,-in. or 3-in. by 2$-in., and the shaft makes 1,200 r.p.m., so that 7,200 blows are struck on the cane per minute. The result is to separate completely the fibro-vas- cular bundles, and to reduce the cane to a material of the nature of Eee=ceisior. This apparatus is preferably 'SNANGN used in conjunction with a crusher, ANT ANY A | and is installed with the view of ZrNZNZN increasing both capacity and ex- NANANZ ! traction. The independent results NAZNAZNA reported from its use in Hawaii in conjunction with 12-roller trains of mill are very superior to those ob- tained with any other combination. Crusher Rollers and Roll Groovings.—The question whether rollers should be smooth or grooved is discussed in Tomlinson’s “ En- cyclopedia of Arts and Sciences,”’ published in 1854. The object of grooving rollers is to increase the “ gripping”’ area, and thereby the capacity of the mill. The modern practice is to use tri- Fic. 141 angular circumferential grooves, three to the inch, the grooves being pitched so as to mesh. The combi- nation of the crusher and the mill in one unit seems to date from Aitken and Mackie’s patent (660 of 1907). This patent claims the surface of a roller formed with a series of short ridges arranged at substantially 45° to the axis, and each series at right angles to the adjacent series. The ridges form a series of figures with triangular ends and trapezoidal sides. This type has become well known as the “ Diamond top roll crusher.’”’ Since it appeared a large number of “ figured ”’ rollers, including a great variety of geometrical patterns, have been patented. The adoption of these devices has not become general. For an entirely different purpose are the drainage grooves introduced 232 CHAPTER XI by Messchaert (patent 8162 of 1914). These are deep circumferential grooves about 14-in. or 13-in. by 3;-in., spaced about 4 inches apart. They are placed on the feed roller, and serve to conduct away the juice expressed by top and feed roller. Otherwise this juice cannot freely escape, and diffi- culties in feeding occur which are often attributed to the setting of the trash turner. The introduction of this system has been attended with increased capacity, increased extraction, and remarkably low water content of the bagasse (especially when applied simultaneously to the back roller), and the possibility of using very large quantities of imbibition water without choking the mill. In many districts this system has become standard practice. That the full benefit may be obtained from these grooves, it is necessary that they be kept free from bagasse ; they are therefore operated in combination with scrapers usually attached to a bar bolted to the housings. Control of Mill Operations.—In the modern cane mill the only non-rigid element is the top roller, which lifts in proportion to the quantity of material passing. A record of this move- ment will then give a measure of the quantity of cane passing at any moment, of the regularity of the feed, of any change in the nature of the cane, of the sensi- tiveness of the movement (or freedom with which the hydraulic ram operates), and of the times at which the mill starts and stops. The apparatus of Deerr (patent 6574 of 1915), Plate XXIII, con- sists of a rod attached at £ to the top brass of the top roller, which moves with the movement of the latter. By means of a parallel motion similar to that employed on steam engine indicators, this | vertical movement is multiplied Fic. 142 and recorded on the chart on the drum 4A, eight inches in diameter, which makes one revolution in twenty-four hours. The recording apparatus is carried on the adjustable system, B, C, D, and the connecting rod passes through a stuffing box, F, designed to give if any undue strain is placed thereon. Algebraical Analysis of the Process of Miliing.—Consider the cane as porous material, the fibre, which has soaked up and holds by means of capillary attraction aliquid, the juice. On the application of pressure to this material the juice is expressed, and eventually a point is reached when pressure fails to afford any more juice. This operation will be referred to as the “ dry crushing,” and the resultant residue of bagasse as the “ dry crushed bagasse.” The second process consists of the addition of water to the dry crushed bagasse, which water mixes with and dilutes the residual juice. On again applying pressure a dilute juice is obtained, and by continuing the process eventually all the sugar present in the cane may be obtained. The bagasse resulting from such operations will be referred to as the ‘‘ wet crushed MET Oe eto | | A A a BAAN AN A Me MEL SEARBY SHREDDER. PLATE XXIII PLATE. XLV: THE DEERR MACERATOR. THE EXTRACTION OF THE JUICE BY MILLS 233 bagasse.’ This process is variously known as imbibition, maceration, lixiviation, saturation, or dilution.* The water used in imbibition may be applied in various ways, and of these there may be distinguished :—1. Simple Imbibition where water only is used at each of the wet crushing units, the process being classed as single, double, treble, etc., simple imbibition depending on the number of units ; and 2. Compound Imbibition, where water is only used at the last mill, the dilute juice therefrom being used as the diluent before the penultimate mill, that from this mill going to the antepenultimate mill, and so on. A single compound process indicates the use of only one wet crushing unit, and is hence the same as single simple imbibition. Double, treble, etc.. compound imbibition imply the use of two, three, etc., wet crushing units. It will be apparent that the number of units employed in the dry crushing has no effect in determining the type of process employed, the break in the continuity of the schemes occurring with the addition of water or other diluent. Experience has shown, however, that to obtain a satisfactory dry crushing not less than two three-roller units, acting in combination with some preparatory device, are necessary ; accordingly, a double coni- pound installation will often consist of a two-roll crusher, followed by four three-roller mills. Such a combination is usually referred to as a crusher and twelve-roller tandem; actually, however, the crusher and first six rollers may be regarded as but one unit. Let the weight of canes be unity, and let the fibre per unit weight of cane be f, whence the weight of juice is 1 —/f,. Let juice be expressed in the dry crushing until the fibre becomes m per unit weight of bagasse. Then = weight of bagasse per unit weight of cane. meee as eel = Weight of juice expressed per unit- weight of cane. m— f ni iges eed = mie Weight of juice expressed per unit of juice in cane. mee) = Weight of juice in bagasse per unit weight of cane. = oye ee whence @&@ =r(I +24) (I—r) +ea7. The third mill receives ¢, + (I + @) (I —7) — {r(I +4) (I —7) +57} = (1+ 4) (I —7)? +46 (I —7”). OF & =F (2-4) 2et fe, tee ae & (I + @) (i —7)*? + 4 (r —7) whence é =r(I +e) (I —7”? +e7 (I — 7). * For this solution I am indebted to Mr. Lewis Wachenberg of the Reserve Refinery, Louisiana. 236 CHAPTER XI But é&=r(ri +t’e) (i +7 +764. wherefore, substituting for e;, WMPt3zr+ar EE a TS PE 3? — 27 and B= (kr Re) id ity r —7+yPF—37—27 r+ (2-7 and, generally, the recovery in a system of compound imbibition is given by Y fet = 7)" # is the number of mills in series. As a numerical example, again let f = 0-I, w = 0:1 and m = 0:5 when whence e where 7 is the constant factor of recovery and the expression wm nd i a wm +f (I — m) Single compound : ___' __ = 0-500 = recovery, y+(I —7) r et) r Double compound : == OBO] x— sLECOYEr Ve Treble compound : ==1 07 G00: ==, TeCOVery. yr+(r —7)? r y+ (I —7)* Comparison of these results with those already obtained for the simple scheme indicates the superiority of the compound process, especially when the number of units increases, as in this case the simple scheme does not give much benefit as due to the subdivision of the water. It will be readily seen from inspection of the above analysis that the dry crushing has a very great effect in determining the total recovery, and that it is only by the use of excessive quantities of water that compensation for an inferior dry crushing can be obtained. Attention to this point has been a dominant factor in determining very high extractions, such as are those which are obtained in the Hawaiian Islands. A second important factor to be considered is the fibre in the cane, and as this increases so decreases the extraction due to the dry crushing. A greater quantity of sugar remains in the bagasse, but if this is operated upon efficiently very high extractions with a high fibre content in the cane can be economically obtained. For example, with f = 0-1 and m = 0:5 the dry crushing will recover 0:8889 of the sugar in cane, as compared with 08235 when frises to 0:15. With treble compound imbibition, and with w = f (i.e., added water Io per cent. in the one case and 15 per cent. in the Quadruple compound : = 0°889 = recovery. other) the value of 7 is 0°5 and of 3is 0:8. The total recoveries if a7) are then 0-8889 + 0:5 X O-:III =0-9777, and 0-8235 +0:5 X 0°1765 = 0: 9647. These results are.of the same order of magnitude; but if single simple imbibition be used the total extractions are reduced to 0-9444 and o-g117. This example indicates the greater importance of long trains and systematic imbibition when the fibre is high, and in this case also it is fortunate that the fuel is plentiful. Experimental results comparing trains of different numbers of units are THE EXTRACTION OF THE JUICE BY MILLS 237 hard to obtain, but the following from the writer’s notebook is of interest. The data were obtained following the breakdown of one unit of a four-mill and crusher train, reducing the combination to a three-mill and crusher installation. The periods compared are each of three weeks’ duration, and by a happy coincidence the tonnage ground and the fibre in the cane are nearly the same. Purity Purity Purity Tons Fibre Dilution first mill last mill mixed cane % % normal Extraction ; juice. juice. juice. per hour. cane. juice. Crusher and three mills 91-1 80-7 87-0 3I°5 13°8 27°0 92°35 Crusher and four mills 91-7 81-3 88-2 31°7 13°9 22-1 95°50 As affording a conspectus of the combined effect of fibre and methods, values of the recoveries under the above-developed expressions are given in the annexed table for values of f 0-10 to 0-15, of wo: 10 too-30 and mo-5o. This table is academic rather than representative of results of record, since in its construction complete admixture of the added water is assumed. Its object is to give a perspective view of the effect of the different controlling factors. It neglects two sources of error:—z. The recovery due to the dry crushing is always greater than the calculation implies due to the superior quality of the first-expressed juice. 2. Admixture of the added diluent with the residual juice is never complete. To a certain extent these influ- ences are compensatory. TABLE GIVING COMPUTED EXTRACTIONS IN DIFFERENT SYSTEMS OF MILLING FOR VALUES OF FIBRE IO TO I5 PER CENT. ON CANE, ADDED WATER IO TO 30 PER CENT. ON CANE, FIBRE IN BAGASSE 50 PER CENT. VALUES REFERRED TO SUGAR IN CANE AS UNITY. = FIBRE. 10% 11% 12% 13% 14% | 15% Dry crushing, water =o .-.| *889 -877 | +864 *850 -&38 | °823 WATER IO PER CENT. Single simple imbibition ---| *944 -936 | °925 -QI4 -905 | -&Q3 Deuble __,, 7 cok ese "O41 | +931 921 910 | +g00 Treble S - . 953 944 | *935 25 "913 904 Quadruple ,, ie | °954 945 | *936 926 “914 905 Single compound ,, 2-1) = O44 936 | °925 QI4 "905 | 893 Double __,, = -«-| *963 "954 *946 937 °927 "916 Treble i : ---| *978 °973 *968 963 7958 | +952 Quadruple ,, 2 ---| *987 -984 *98o +976 "972 | +968 WATER 20 PER CENT. / Single simple imbibition +996 "994 "992 "989 | +987 Quadruple ,, 3 ..-| *999 *999 998 997 | "997 | *996 238 CHAPTER XI The Economie Limit of Extraction—In schemes employing the addition of water, expense is frequently incurred in the evaporation thereof, though often the fuel afforded by the bagasse is sufficient to treat considerable quantities of water. In what follows the factory is supposed to be balanced when dry crushing is operated; that is to say, under these conditions the bagasse just suffices for the operation. All expenses then connected with imbibition are to be charged to the debit side of the ledger. Let there be unit quantity of juice (or of sugar) in the dry crushed bagasse to which w water is added. There is then obtained on crushing : oe wp Sugar per unit originally present. Substituting ; z = expressions already found, the quantity of sugar obtained in the different systems is :— for vy in the Single simple imbibition: ea rane : : Fei Sine : oe 2 2 Double simple imbibition: I E x =) ’ gee a ae og nN n n-fold simple imbibition : I G Te 5) w ; a eNotes w > MS ly Single compound imbibition : aa ice ( eer ie w Tie ) ee Double compound imbibition : 7 ad : 5 I+w oe (z arr = 3) w n-fold compound imbibition: = Liat? Duke it ea (: a ete nN I+ w I+w Now consider the case where the bagasse contains 50 per cent. fibre (f) and 50 per cent. juice. Let water (w) be added equal to f, 2f, etc. Then in all cases these expressions on computation give the sugar which can be recovered per unit present in the bagasse and independent of the quantity of fibre in the cane; that is to say, with canes containing Io per cent. fibre, 20 per cent. of added water will recover the same percentage of sugar from that present in the bagasse as 24 per cent. when the canes contain 12 per cent. of fibre. In the graphs in Figs. 143 and 144 are shown values of these expressions for the values of w = f, 2f, etc., j.e., water Io per cent., 20 per cent., etc., on cane when the fibre is Io per cent. on cane, and so on. The value of the additional sugar obtained will be any one of these expressions multiplied by a constant obtained from a knowledge of the selling price of sugar, cost of manipulation, of containers and of freight, etc. The cost of obtaining the sugar will be mainly the cost of evaporating the added water, together with the interest on the prime cost of the additional heating surface necessary. These two items may reasonably be regarded as a lineal function of the added water or briefly by K w, where K is constant. THE EXTRACTION OF THE JUICE BY MILLS 239 The net profit to the producer will therefore be given in the case of n+ w and K are constants and is the number of wet crushing mills. Similarly the corresponding expression for compound imbibition is simple imbibition by the expression C { I — £ "t — K w, where C @ i ecerew. <1 —Kw I-35 - ¢--y The economic limit of extraction will be obtained when w is chosen, so that these expressions are a maximum. Solutions of this problem are given for completeness. i The general formula when using simple imbibition may be written :-— G {2 = Li "| Kw = maximum, ori —” (n + w)-"— L w = maximum, where L = = constant. Differentiating and equating to zero n? (n + w)—”t+0 — L =zero fk n+ :) Solving, 0 eRe tA < ye +1 For example, the maximum value of the expression 2 aie —— 0/08 Cre) *U @+ up sa a a Fs $ will obtain when w= 7 ven = 4:84. 0-025 The general formula for compound imbibition may be written :— w sa — L w, where L apes as before. LSE (x aw Je C I+w I+w This expression reduces to w(ri+w)—'{w (1 +w)"-'+ 1}'—Lw. Differentiating and equating to zero {w (a+ w+ x} (z+ wh + (wn —) (x + wy} —w (i +w)"—{w (r+ w)"—" + 1} -7°{ (r+ w)"—-! + w (n—1) (I + w)"—?} — L= zero : (I-+w)”—' +w (»—1) (I+ wv)" (I + w)"—* (I + nw) ame wate tip fea tet zy If desired the roots of this equation may be found by Horner’s method, but generally the maximum value of w will be obtained with less labour by trial and error. Having now obtained the expressions indicating the economic limit, it remains to find some values relating to actual practice. LAGASSE Lor Si7g/e, gGuadrup/(e SIMp WwW = added waler Fic. 143 GAANT) artily ot 4 bre a F: Z Oo aA 950 and kor ur quantity of added warer (ta) = uni? quantity Of Fibre\in care. a Ss S 2 J W= GdadeaA warer. Fic. 144 n 242 CHAPTER XI Let the juice in the bagasse contain s sugar, of which # is recovered in the subsequent operations. Let the value of the sugar, after deducting all charges for containers, freight, overhead, etc., be v, and let the efficiency of the added water be e. For convenience of writing denote any one of the above expressions by f (w). Then the value of the sugar obtained is spvef (wv). The variable expense to be charged against the value of the sugar is the cost of evaporating the water, together with the interest on the prime cost of the larger heating surface required. Both of these may be regarded as a lineal function of w, so that the cost may be expressed as Kw where K is constant. Now the extreme values of s may be taken as Io per cent. and 16 per cent., of p as 70 per cent. to 85 per cent., of v as $30 to $60 per ton, and e, about which the literature of the cane affords little information, will be taken as 50 per cent. The lowest value of s p v e will then be 0-10 X 0°70 X 30 X 0:50 = $1-05, and its highest value will be 0-16 x 0°85 X 60 X 0:50 = $4:08. With quadruple effect evaporation it is permissible to accept an evapor- tion of 30 Ibs. water per Ib. of coal. If the coal costs $10 per ton, the cost of evaporating a ton of water will be 30 cents. On the other hand, some plantations are very favourably situated with regard to local supplies of cheap wood, and are able to evaporate water at a much cheaper rate. The cost of evaporating a ton of water will then be taken as lying between the limits of Io cents and 30 cents. In the case of single imbibition, simple or compound, with the lowest values of s, # and v, and with coal at $ro per ton, as representing unfavour- able conditions, the economic extraction curve expressed in cents per ton of cane will be found by plotting values of 1-05 x — —o-3w, the maximum point being determined as already indicated. In Figs. 145 and 146 are given twenty-four such graphs. They are calculated for f (w) — 0-3 w, 2 f (w) — 0° -2 wand 4 f (w) —o'! w, “f (w w) denoting any one of the expressions representing the effect of the added water. The values selected are intended to represent unfavourable, average and favourable conditions, and are numbered 1, 2, and 3 in this order. In calculating the numerical values to obtain points on the curve the canes have been accepted as having Io per cent. of fibre and the paeaee as con- taining 50 per cent. As abscisse are laid out values w == I, 2, 3, etc., the corresponding values of m f (w) being plotted as ordinates, and representing the profits as cents per ton of cane. Referring to the graphs in Figs. 143 and 144, the superior action of compound imbibition is very clearly shown, especially in the longer trains, where the curve rises very sharply from the origin. Similarly it will be seen that the subdivision of the water used in schemes of simple imbibition is not attended with any very great benefit, double compound imbibition, for example, showing better results than does the quadruple simple process. Inspection of the economic curves shows that generally they rise steeply from the origin, and that they do not present a “ peaked” but a “ flat ” maximum, that is to say, there is a region over which the profits due to imbibition are sensibly constant, and it should be over this region that the factory is operated. It is also worth while noticing that with the compound schemes the economic maximum is reached with a less quantity ee THE EXTRACTION OF THE JUICE BY MILLS 243 of water than in the single schemes. The position of the maximum is indicated by a dotted ordinate. In the case selected as unfavourable, the profits are very small, and it is easy to see that there will sometimes be occasions where any extraction beyond that obtained with the dry crushing will be attended with loss. The discussion above has purposely neglected two points, the mathematical treatment of which presents difficulty. In many cases the bagasse alone will of itself afford fuel for a substantial imbibition, in which case the only expense to be charged is the interest on the prime cost of additional heating surface in the evaporators. Ina case such as this, the theory given above is applicable, if and when it is possible to determine the point in the process where purchased fuel becomes necessary. In the second place no account has been taken of the cost of installing the additional mills required in the more completeschemes. This item can- not be expressed as a function of the added water, but will be a constant charge against the process. If such a constant be introduced into the econ- omic equations given above, its differential coefficient will be zero, and the position of the maximum point in the economic curve will not be affected. As has been shown elsewhere in this chapter, the installation of additional mills has a great effect in increasing capacity while maintaining efficiency, and this effect, combined with the superior advantage of long trains on the grounds of the economic use of the water, would still more accentuate the economic position of multiple milling when capacity and efficiency are jointly considered. This last point is only concerned with the economics of the installation of a new factory, or of the extension of an old one. It does not enter into the policy of an executive regarding the operation of the machinery as it actually exists. Composition of the Cane as affecting the Economic Extraction.—The juice of the cane contains from the engineering standpoint two distinct juices, one in the pith, of high sugar content, and the other in the rind and nodes of low. The pith juice is that first expressed, and it hence follows that there must be a continuous fall in the quality of the juice with the expression of each successive fraction. If, however, all the pith juice has been expressed there will be observed no further fall in quality, since the remaining fractions will consist of rind juice only. As has been shown by Savage’, such a condition does actually occur in the very high extractions obtained in the Hawaiian Islands, where he found that successive operations on last mill bagasse with an hydraulic press gave a juice of uniform com- position. The selective extraction of the pith juice may be traced in the following experiments due to the writer!® who separated mill bagasse into pith tissue and rind tissue, analysing each separately. The results given below show that the pith tissue, originally the sweeter, finally contains much less sugar than does the rind tissue, and that, while the extraction as regards the pith juice is nearly complete, the rind tissue is very imperfectly treated. Pith bagasse. Mill I. Mill TI. Mill III. Mill IV. Weight per Ioo bagasse 53°33 48 -62 50 -00 51°25 Sugar per cent. hi dihess 7°19 3°78 2-87 Fibre per cent. foe F3R.-55 41 +58 45 °63 46-91 Rind bagasse. Weight per 100 bagasse 46°67 51 -38 50 -00 48 +75 Sugar per cent. : Q-I2 7°13 4°34 4:06 Fibre per cent. =: 35°15 AE-5A 44°90 46 -67 244 aati ae tine pe ee, es ae Cae ae ce Ei SY Peres EZ) Ver percent ay Cae ee ee te oe OS ee ie ee Oe TL. ee AN RE AY NN CA NN LZconome Curves for Simple (imbibition M2 4 aes NS . gos. one fo Py, ee ea a D) Added Fic. 145 sea JO Ny 9 of Cane 8 = per tor & pre £7 20 BO Added warer percent of care Fic. 146 246 CHAPTER XI Whole bagasse. Mill I. Mill IT. Mill ITT. Mill IV. Weight per 100 bagasse 100-00 LOO :00 100 -0o IO00 :00 Sugar per cent. LOS) 7 +16 4°06 3°51 Fibre per cent. Sree SYD ie te 41°56 45°20 46 +87 These results were obtained from material resulting from a crusher and twelve-roller mill, but with more completely disintegrated material affording a homogeneous mass for the mills to treat this distinction vanishes. Such an effect is obtained with appliances like the Searby shredder The observed fall in purity of each successive fraction of juice has been responsible for much inferior work in the past, following on the idea that the material thus obtained might even decrease the total output of sugar. This could only happen if the later extracted juice was specifically “ melassigenic,” and of this there is not only no evidence, but there is strong evidence to the contrary in that the molasses obtained from the juices of high extraction are substantially of the same purity as those obtained from less efficient work. To illustrate this point, in the table below are given the average results of seven factories which for three years operated at a higher, and for three years at a lower extraction. The purities of the juices are referred to a polarization gravity basis, those of the molasses being absolute. Crusher Mixed Defecated Last Mill Molasses Mixed : juice juice juice juice purity. juice Extraction purity. purity. purity. purity. % cane. Low ... 89 °5 87-2 88 -6 TPs 43 °2 IOI +5 93°7 High... 89 °1 85 °9 87 +2 72:9 42 °8 I1i2°3 97 °O It will be seen that against the 3-3 units rise in extraction is to be placed a loss of 0-9 unit extra fall in purity as between crusher juice and mixed juice, while the rise in purity due to defecation and the purity of the waste molasses is substantially unaltered. The factories whose results are quoted were, however, fortunate in working with canes of more than average purity, and in cases of less than average purity the decreased purity of the later extracted juice may become a factor of greater importance. The actual composition of bagasse may be referred to here. Twenty-five years ago material containing 50 per cent. of water was regarded as well crushed. Such bagasse with the limited quantities of water then used could have contained but a little over 40 per cent. of fibre. There are mills now working in the Hawaiian Islands which obtain as a crop average bagasse with distinctly less than 40 per cent. of water, corresponding to nearly 60 per cent. of fibre. Elsewhere figures as high as these are not reported, and 46 to 47 per cent. of water would seem to represent good practice. It is not heavy pressure alone to which these results are due, efficient preparation and subdivision of the cane, combined with the adoption of Messchaert drainage grooves, being also contributing factors. Variety of cane also seems to have an influence, and those varieties classed as hard, and which have a larger proportion of rind tissue, afford a bagasse with more fibre than do the softer canes. This influence is well illustrated in statistics coming from the Hawaiian Islands, where the higher percentages of fibre in bagasse appear at those mills working up the Yellow Caledonia cane, which contains a higher percentage of rind tissue, THE EXTRACTION OF THE JUICE BY MILLS 247 The Actual Performances of Milling Plants.—In studying the actual performances of milling plants, besides the extraction there is required to be known the size and number of the mills, the preparatory appliances used, the tonnage of cane, or more exactly of fibre, treated per hour, the quantity of water added and its method of application, and, finally, the composition of the bagasse. As representative of modern practice, there are given below the crop averages for the Hawaiian Islands (1917), Java (1918), Mauritius (1918)—these being the only districts which have yet established a system of mutual control with the annual publication of collated results. Of these figures it may be remarked that the sugar percentage in cane is exceptionally low for Hawaii, and exceptionally high for Java (cf. Chapter II.) There do not seem to be available any but isolated statements regarding the work done in Cuban mills. Though there are some mills in Cuba which reach extractions of 95°-96°, in the majority capacity is of so much more importance than quality of work that over all Cuba the average extraction is probably not more than 90. The writer would estimate the average quantity of added water as about Io per cent., and of water in bagasse as but little under 50 per cent. As regards capacity of the mills, from data collected by the writer and obtained from many sources, such as correspondence, the reports of trav- ellers and occasional published statements, it would appear that in Hawaii a crusher and 12 roller 78-in. X 34-in. mill treats up to 8 tons of fibre per hour, a similar 66-in. train treating up to 5 tons. In Cuba a double crusher and 15 or 18-roller train (84 in. X 36 in.) will treat up to 13 tons of fibre per hour. In Java a crusher and g roller train (60-in. x 30-in.) treats 4 tons of fibre per hour, and a similar figure is obtained in Mauritius. Hawaii, 1917. Java, t918. Mauritius, 1918. Cane fibre % ae I2 -62 13-02 12°17 asugar %, 2 13-76 13°74 13 +32 Mixed juice % cane II6°5 87-9 90-9 Added water % cane 39°4 15-2 16-4 Water % bagasse ... 42 °3 47 °2 — Fibre % » ve 55°3 47°7 47°7 Sugar % a 1-8 4°3 4°2 Extraction Be 97:0 2°1 92:0 The Development and Conduct of Imbibition.—In 1840, Robinson as a com- munication from unnamed parties in Mauritius, obtained a patent (8731, 1840) for a process of imbibition. He claims the use of hot water sprayed on the bagasse from a perforated pipe in special connection with a six-roller mill, also claimed as novel. _ At very nearly the same time Daubrée! discussed the possibility of increasing the yield by this means, and at Payen’s sug- gestion there was constructed a five-roller mill in which steam enclosed in a hood was allowed to act on the crushed cane. The earliest description of the process in operation is perhaps that due to Wray, and appearing in his “ Practical Sugar Planter,’ 1848. He there describes as working in Province Wellesley, a three-roller mill, followed by a two-roller unit as the imbibition mill. A little later Dureau also records the exceptional use of imbibition in Louisiana. Dry crushing, however, seems to have remained standard practice. In 1874 Russel used an imbibition process successfully in Demerara, and con- temporary records show that the scheme was then considered very advanced practice. His patent (4094 of 1874) includes the use of two mills separated 248 CHAPTER XI by a long carrier, and the return of dilute juice and the separate defecation of the last mill juice. Other patents of this period are those of Cail (2212 of 1870) which is little more than a duplicate of Robinson’s, of Chapman (4411 of 1875) and of Rousselot (5050 of 1876). These last-named inven- tors preferred two-roller mills as the imbibition unit, and this scheme was largely developed not many years later in the Hawaiian Islands by Alexander Young. To this period also belongs Mallon’s U.S. Patent (182377, 1876) for the use of steam applied through a hollow trash bar, a device also to be found in connection with Le Blanc’s four-roller mill (patent 5494 of 1883). Compound imbibition is perhaps first distinctly described in 1884 in connection with the eight-roller mill of Brissoneau and La Haye. It also forms the subject of a patent (U.S. 787101, 1904) granted to Lorenz, but by this time the process was no longer novel. FIG. 147 In employing imbibition schemes, difference of opinion exists as to whether hot or cold water should be used. The natural answer would be that hot water is the more effective agent, but very detailed experiments made by Von Czernicky in Java show that no difference is to be found on tests, and this has been the experience of the writer. At the present time the standard method of operation comprises the use of a perforated pipe of a saw-cut trough, whence the diluent is delivered to the blanket of bagasse. This process is the same as that patented by Robinson eighty years ago. Some other more detailed schemes which do not seem to have come into extended use are mentioned below. Injectors.—As a means of obtaining a better distribution of the diluent, injectors arranged in a row parallel to the rollers may be used. Such a scheme is indicated in Fig. 147, which also indicates two methods of mechani- THE EXTRACTION OF THE JUICE BY MILLS 249 cally obtaining a more effective distribution of the water. These schemes as illustrated are due to Léon Pellet. Ramsay's Process—The “‘ macerating scrapers’? of Ramsay (patent 18515 of IgII) are indicated in Fig. 148. The scrapers bear tangentially on the upper and discharge rollers, and attached to the scrapers are the hollow boxes to which is admitted water under _ pressure. The system thus defines a _ passage through which the bagasse travels in close contact with water or other diluent. Deerr’s Process—Patent 126093 of 1918 is shown in Plate XXIV. It consists as to the upper portion of a complete perforated rotating cylinder, enclosing a stationary incomplete cylinder. To the interior of the latter, water under pres- sure is admitted through a hollow shaft, The liquid can only escape through the opening in the stationary cylinder, and Fic. 148 those perforations in the outer cylinder that come opposite to the opening as the outer cylinder rotates. The lower system is shown with the relative positions of the two cylinders reversed. Means are also provided to vary the pressure exerted on the layer of bagasse by the upper system, and also the speed of rotation of the cylinders. The object of the device is mainly to bring the diluent under pressure in inti- mate and distributed contact with the layer of bagasse which is itself under that pressure at which experience has shown the absorption of water to be at a maximum. Macerating Baths.—Instead of spraying the diluent on the bagasse, a system of “ bath maceration ”’ is in use, and to this system the term maceration is not altogether inappropriate. In this system the dilute juice expressed from a mill is returned to a tank through which it flows in an opposite direc- tion to the bagasse; the juice overflows at the end of the bath, and the water required is pumped on to the bagasse immediately before it enters the mill. This system is disclosed in Fryer’s patent 1073, of 1869, and since that date has formed the subject of a number of other patents with various modifications ; the form in which this process is generally applied is indicated in Gibson's patent (24206 of 1895), Fig. 149. 250 CHAPTER XI A variant of this system is seen in Kottmann’s patent 17092 of 1884, which employs a rotating watertight drum with counter-current flow of water. McNeil’s patent (5431 of rg1r) employs maceration with counter-current flow, and recognises in addition that the juice expressed by the top and front rollers is more dilute than that expressed by the top and back ; accord- ingly, the more dilute juice is collected separately and used in the bath, the more concentrated juice going direct to the boiling-house. Other Methods employing Pressure-—A number of patents have been taken out for the extraction of juice by means of direct pressure ; the first of these is that due to Crossley and Stevens (9574 of 1842). This may be the process that proved a failure when tried in St. Vincent about this time. The process of this nature that has attracted most attention is that due to Bessemer (patent 12578, 1849). He employed a reciprocating plunger operated by steam power ; the plunger worked in a horizontal cylinder into which the canes were fed vertically, without any previous preparation ; the pressure was applied on both strokes of the piston and exerted a con- tinually increasing pressure up to the end of the stroke. This machine was operated experimentally on canes brought from Madeira, but was not success- ful. Several other direct pressure patents have been taken out—most of them including some means for the preliminary disintegration of the cane, and the simultaneous action of water and of steam. The transmission of power is always hydraulically. Matthey’s patent (21021 of 188g) claims a principle only mentioned in this patent, namely, substitution or displacement extraction. He proposes to press the finely divided cane in vertical cylinders, after which water is introduced into the cylinder, and on to the surface of the crushed material. On again applying pressure, the water is forced through the cane, displacing the residual juice but not mixing with it; this patent is for a process and does not describe the machinery in any but the broadest terms. It was tried without success in the early days of the beet sugar industries. REFERENCES IN CHAPTER XI. iS, PAS Bx: (Sta.,- Agric. Ser., Bull) 30: do. do. - 7 ee Bulle 28: Verslag eener Studiereis naar de Sandwich eilanden. A Brief Account of Francis Willughby, his Journey through Spain. London, 1673. 5. East India Sugar, Papers relating to the Culture of the Sugar Cane, etc. London, 1822. 6s JPhilieiiranss Roy. (s0Cs, 11780; 70) 313, Hs Hepert of the Belgian Commissioners to the Universal Exhibition at Liverpool, 1539. The Sugar Planter’s Manual. London, 1842. Manuel du Fabricant du Sucre. Paris, 1833. 10. Java Arch., 1896, 4, 222. 11. U.S. Senatorial Document, No. 50, 1845. 12. Results circulated locally in Hawaii. 13) Heo Ee Ar IB Std, A Stic. Schull... 14. La Génie Industrielle, 1852, 2, 357. 15. Java Arch., 1899, 7, 174. ah WwW NHN AW CHAPTER XII THE DIFFUSION PROCESS In the early part of the nineteenth century a German professor, Goettling, proposed to extract the juice of the beetroot by systematic washing, and his scheme was operated at Karlsruhe, by Haber and Schutzenbach. In France the earliest pioneer of this process was Matthieu de Dombasle, whose French patent is 7981 of 1831. The earliest British patent and the first one mentioning the cane is that of Watson (7124, 1836) which describes a one-cell counter-current process. Constable’s British patent, communicated to him by Michel, is 10171, 1844, and it describes a process in which the cane is transferred in perforated baskets from cell to cell. This patent correctly describes the mechanism of diffusion through a permeable membrane, and is the one which was unsuccessfully operated in Guadeloupe by Bouscaren about this time. The actual introduction of diffusion as a commercial process is due to Robert, the manager of a beet sugar factory at Seelowitz, in Austria. His British patents are 594 and 3187 of 1866, taken out by Minchin, who operated diffusion successfully at Aska, in India. From the time of its first successful operation, the diffusion process became rapidly established in the beet sugar industry, and its operation remains now as originally executed. The only developments have been some attempts to put into operation continuous diffusion processes, such as those of Kessler (British patent 15355 of 1902) and of Rak (British patent 16905 of Igo1). The latter is in use in a few factories. In a diffusion process proper, the plant cell is not ruptured, and advantage is taken of the property possessed by crystalloids of passing through a cell wall, or membrane, when water or a solution more dilute than that contained in the cell is in contact with the exterior of the cell wall. In this way the bodies of a colloid nature which do not possess this property are retained within the cell. | Independently of diffusion through a cell wall, all solutions in contact tend to become of equal concentration, and the process is physi- cally of the same nature as diffusion, such an action obtaining when the cell wall is ruptured. This property occurred in the older processes, such as that of Dombasle, to which the term “‘ maceration ”’ was originally applied, and this term or some equivalent such as “ lixiviation,” should be applied to those processes which deal with comminuted material such as bagasse, since in the absence of a cell wall or other permeable membrane diffusion proper does not obtain. In the sugar cane industry numerous plants were erected in Spain, Egypt, Louisiana, Mauritius, Brazil, Demerara, Java, Hawaii, and the West Indies. Very few of them now remain, and most of those that were erected met with financial disaster. The causes which led to failure were both technical and economic, and may be briefly summarized :— 251 252 CHAPTER XII 1. Faulty design, especially in the earlier plants, and particularly in connection with the cane cutting machinery. 2. Difficulty in maintaining a continuous supply of cane, an essential to the economic conduct of the process. In the beet sugar industry the raw material may be stored over long periods, a proceeding impossible with the cane; and again the more highly developed social organization in beet growing districts, as opposed to the pioneer conditions in cane countries, tends to more regular working. 3. Greater elasticity of the milling process, whereas the diffusion scheme has to be operated at its designed capacity, or else at a loss of sugar or at an extreme dilution. In the case of poor cane in the milling process, all dilution can be stopped, while in diffusion dilution must always obtain. 4. Excessive fuel accounts, due however not so much to inherent faults in the process, but rather to the undeveloped state of steam utilization schemes at the time when the diffusion processes were installed. Diffusion Apparatus.— The apparatus peculiar to a diffusion plant are the vessels in which the diffusion takes place, and the devices used to cut the cane into slices or chips. Cane Cutter.—A type of cane cutter that has been largely used is shown in vertical section in Fig. 150; on a vertical spindle 5, belt-driven from the pulley d, by means of the bevel wheels c, is carried a disc e. The whole is enclosed in a sheet iron casing # and closed by a strong cover g; fastened on to the disc e are a number , of boxes varying from six to twelve, each of which carries a strong sharp knife. The | knives are fixed on the disc exactly similar - tothe cutting edge of a carpenter’s plane, and the knife boxes are arranged so that they may readily be removed from the disc and spare knives substituted when one set has become blunted. A plan of the disc with an arrangement of twelve knives is shown in /7g. 151. Securely fixed to the cover are one, two or more hoppers a into which are fed the canes, which descend on to the disc by their own weight. A high speed is given to the disc, from Io0o0 to 150 revolutions per minute, and the knives cut the cane into chips one-twentieth of an inch or more in thickness, dependent on the setting of the knives. The hoppers are made either vertical or at an angle—the former giving round and the latter oval chips. Thé chips fall into the receptacle formed by the sides of the apparatus below the disc, and thence pass on to the shoot. The cutter is variably placed above or below the diffusion battery. Cane cutters of this type differ in details. They are sometimes directly driven without the interposition of belt gearing, and are sometimes over instead of under-driven as shown in Fig. 150. The shoot 7 is also sometimes dispensed with and its place taken by a scraper actuated by the shaft 6. In this case the bottom of THE DIFFUSION PROCESS 253 the receptacle h is flat, or nearly so, and the chips are swept out through an opening in the bottom. To work up 300 tons of cane in 24 hours, a plant of this nature will be about 5 ft.in diameter. The capacity depends on the number of hoppers, and on the setting of the knives, whether to give thick or thin chips. More cane can be cut when thick chips are allowed, but the efficiency of the after- process of diffusion is diminished. Diffusion Cell—A section through a cell of a diffusion battery, along with its accompanying juice heater, is shown in Fig. 152. It consists of a cylindrical vertical shell, the bottom being made with a slight slope, and the top fitted with a head box ; the cell is closed by a door on the top, which is clamped tight by the screw and lever shown at 6; by slackening the screw the door can be slung on one side, to allow of a charge of chips being intro- duced. Round the bottom part of the cell is fixed a perforated false bottom, d, the object of which is to prevent pieces of cane being carried along the pipe c. In some designs the lower door itself carries the false bottom. The joint in the lower door is a hydraulic one, consisting of a _ hollow rubber tube provided with a pipe by means of which water is conducted to the tube, which is - placed ina circular groove contrived either in the door itself or in the bot- tom of the cell. The water which fills this tube is taken from a tank ata Fic. 051 high level, so that in all cases the pressure in the tube is greater than the pressure in the cell. In other cases the rubber tube is connected by a pipe with the main steam; the direct steam becomes condensed in the coil, and pressure is made in the rubber tube by the steam acting on the condensed water. Attached to each cell is the juice heater 6; this is of the verti- cal tube type, exhaust steam being admitted at 0, and the condensed water drawn off at 4. Communication between diffuser and juice heater may be made either.at top or bottom by the pipes k orc. The main juice-circulating pipe is shown at m, the controlling valves or cocks appearing at 7. The floor level on which the operator stands is at the line J, all valves and cocks being within easy reach ; gis a small pipe let into the cover of the diffuser to act as an air vent to allow the air to escape when the diffuser is being filled. Operation of a Diffusion Battery.—-A diffusion battery generally consists of from twelve to sixteen vessels, of which two are always out of commission, filling or discharging. In Fig. 153 is represented diagrammatically a six-cell 254 CHAPTER XII battery, of which four cells are effective, one, f, being filled, and one, e, being ready to be emptied. The cell r has been filled with fresh chips. By means of compressed air, water that has been admitted to cell e is forced out of that cell, and is transferred to cell 4 and an equal quantity of water or rather dilute juice in cell 4 passed on to cell 3, and soon. The material in cell 2 passes on to cell 1, which contains fresh cane chips which have not yet come into contact with water or dilute juice. Water pressure from an overhead tank is now applied to cell 4, and a similar forward movement obtains, and in this case material is withdrawn from cell 1; the quantity drawn being equal in volume to the water admitted to cell 4. Cell 4 is now treated as cell e in the first operation, and in the meantime cell e has been filled with fresh cane, and the above-described routine again takes place. By following out Mh] O | this process it is seen that when f A) | 4 TU there are m effective cells in opera- Ca tion, fresh cane comes into con- { ry tact with water or dilute juice 2n-1 times before it is finally dis- charged from the battery. For more detailed information on the operation of diffusion batteries, reference should be made to any standard work on beet sugar manufacture. Extraction in a Diffusion Bat- tery.—The general equation ob- tained for compound maceration in a milling plant gives also the extraction in a diffusion battery, that is to say, if there are diffu- sions ina round of the battery where the extraction in each operation is 7, then the total ex- eaves SS y —(I —7) FIG. 152 It is evident from this equa- . tion that the extraction increases as both vy and ” increase. The value of 7 increases with the completeness of the diffusion whereby a time factor is introduced, and also with the quantity of material passed from cell to cell in each operation. At the same time, however, increasing the “‘ draw” increases the dilution. At the time that diffusion plants were operated, the dilution was about 30 per cent., and the extraction from 95 per cent. and upwards of the sugar in the cane. Mixed Extraction Processes.—As early as 1850, experiments in the system- atic lixiviation,of bagasse were made in the French West Indies, and since that time several schemes have been prominent, and, as long ago as 1883, bagasse diffusion was successfully operated at Torre del Mar, in Spain.” The most recent attempts in this direction have been that of Kessler, U.K. patent 15355 of 1902, who proposed a U-tube through which the bagasse was THE DIFFUSION PROCESS 255 intended to travel in a direction opposite to a current of water. The Perichon system of bagasse extraction, U.K. patent 7337 of 1896, was operated in Egypt®. It included the systematic lixiviation of the bagasse in trucks with perforated bottoms, combined with the subsequent milling of the exhausted bagasse. That truck immediately before the final re-crushing mill received water which, after passing through the material, was pumped to the next truck in series. The Naudet system is a combination of milling and diffusion, and is covered by the patents of Naudet and Manoury, 25695 of 1g01; Naudet and Hinton, 27666 of 1903; and Naudet, 2928 of 1904. The patents deal with two entirely different features: (rz) the combination of milling and diffusion ; (2) the method of diffusion. As regards the first, cane is crushed in a mill and the bagasse conveyed to a diffusion cell, whither also goes, after separate heating and liming, the expressed juice which is circulated over its own bagasse. In this cell, dilution with juice which comes from the rext cell in series takes place. The addition of water takes place in the last cell in the series, after which the bagasse oe is milled. In the patent of Igor it is odes stated that the dilute juice expressed from the last mill is returned to the | é battery; and in the patent of I903 it is implied that this dilute juice is wasted, the extraction being completed in the battery. The raw juice being 3 limed, heated, and filtered over its ba- gasse, affords a juice which passes direct to the evaporator and eliminates de- a fecators and filter-presses. The diffusion process refers to the scheme of circulating the juice through a diffuser and heating it externally to the battery. Asecond pert of the process claimsraising the density of the drawn-off juice to the original density of the normal juice even by the addition of molasses, but does not claim the suppression of molasses. The Naudet process has not come into general use, though it remains in success- ful operation in Madeira. FIG. 153 Geerligs-Hamakers Process.—In 1903, Geerligs and Hamakers demonstra- ted by large-scale experiments in Java that, by diffusing bagasse from a six-roller mill and crusher, an extraction of 98 per cent. was obtainable, with a dilution of 19-6 per cent. on normal juice. This scheme has not been developed. Diffusion of Dried Cane.—The resuscitation of an old idea is seen in MacMullen’s proposal, patent 18237 of 1908, to shred and dry the cane, afterwards treating it by diffusion, with utilization of the fibre in paper- making. It was understood that this partially manufactured material would enter the United States duty free, and it is only under such advantages that the process could hope to be successful. This scheme is not new ; it is included in Crossley’s patent 7469 of 1837, and in that taken out by Newton for a foreigner 12033 of 1848. Such a process was operated by Daubrée in 256 CHAPTER XII Martinique, prior to 1850, but the material, on arrival in Paris, was found to have fermented. REFERENCES IN CHAPTER XII. Bulletin de Pharmacie, 191, 3, 371. U.S. Dept. of Agric., Div. of Chem., Bull. 8. S.C., 1898, 30, 491. Int. Sug. Jour., 1903, 5. Peps CHAPTER, XTi THE ACTION OF HEAT, ALKALIES AND ACIDS ON SUGARS AND CANE JUICES In the process of sugar manufacture the cane juice is subjected to the in- fluence of an elevated temperature, and to the action of lime. In some processes sulphurous and phosphoric acids are also employed. The action of these agents, together with some other connected points, is discussed in _ this chapter. Cane juice, as it leaves the mill, consists of a turbid solution of cane sugar, reducing sugars, bodies of unknown constitution known as “ gums,”’ salts of both organic and inorganic acids, mainly potash salts, colouring matters, albuminoids, matter in a colloid condition, suspended particles of fibre and dirt, and a variety of other bodies. The Colloids of Cane Juice.—When all the grosser particles of suspended matter in a cane juice have been removed by straining through glass wool, there remains a turbid liquid, the turbidity of which is due to matter in the colloid state. The following observations were made by the writer!. The colloids may be separated in the cold by filtration through asbestos. The | filtration is very slow and only 5 c.c. of juice can be filtered through an area of I sq. cm. before the asbestos mat is clogged. The filtrate obtained is quite bright, and on heating never gives more than a trace of precipitate, indicat- ing that filtration removes the same bodies as are coagulated by heat. The quantity of colloids thus separated by filtration amounts to from 0-15 ty 0-25 gram per 100 c.c. of juice. After coagulation by heat, the colloids do not revert to the colloid condition on cooling, but after coagulation by alkalies the colloid state again appears on neutralization. The colloids are not precipitated by electrolytes except by calcium chloride in very large quantity, and are hence to be classed as lyophilic. On passing a current of 8 amperes under a head of 10 volts through cane juice contained in a U-tube, there is a distinct migration of the colloids towards the anode, the juice becoming clarified near the cathode. The colloids are hence negatively charged. An observation well known in sugar-houses is the great increase in the rapidity of filtration that takes place after the juices have become alkaline. One of the major constituents of the defecation precipitate is “cane wax,” which, in turn, contains a large proportion of fatty acids. The action of lime on these bodies will result in the formation of a soap, and Kraffts? has shown that in neutral solution such bodies behave as colloids, becoming crystalloids in alkaline solution. Herein probably lies one, at least, of the causes of this phenomenon. 257 ¥ 258 CHAPTER XIII The Colouring Matter of Cane Juice.—The principal colouring matters in cane juices are chlorophyll, anthocyan, saccharetin, and bodies of a polyphe- nol nature (tannins), all of which occur naturally. Formed in the process of manufacture are caramel and lime-glucose decomposition products. Chloro- phyll is the substance to which the green colour of plants is due ; whatever quantity of this passes into the juice is removed in the press cake. Anthocyan is the term applied to the red and purple colouring matter to which the colour of some canes is due. Actually the term means nothing more than colouring matter. It is dark green in alkaline solution, and is precipitated by an excess of lime. Saccharetin is the term applied by Steuerwald? to an “ incrusting ’’ material obtained by cold alkaline digestion of bagasse. This body is probably a waste product of the plant metabolism and is found deposited on the fibre. It is an aromatic carbon compound, giving pyro- — gallol on dry distillation and catechol on fusion with potash. On heating with hydrochloric acid, vanillin is given off. This substance is colourless in acid, and deep yellow in alkaline solution, and is connected by Steuerwald with causing the dark colour of cane products in combination with iron salts. The incrusting material of lignified plant tissues have been identified by Tiemann and Harman with coniferin, but Czapek* regards it as an alde- hyde, closely related to coniferylic alcohol, to which he has given the name hadromal. Tannins were first observed in the cane by Szymanski® and were after- wards studied by Went®, by Browne’, and mcre recently by Schneller® and by Zerban®. These bodies are located mainly in the actively vegetative portions of the cane, especially the tops and the eyes. Schneller regards the incrusting material or saccharetin of Steuerwald as derived from these tannins or polyphenols, and deposited as waste matter on the parenchyma. These bodies have the property of forming, with ferric salts, dark-coloured bodies, which are nothing but inks, and to these inks the dark colour of cane juices, as - well as the greyish tint often seen in white sugars, may be attributed. This coloration is, however, also connected with the action of oxidizing enzymes occurring in the juice, the presence of which is first shown by Raciborski!®, and the action of which has been further studied by Zerban®. He shows that cane juices expressed in the absence of contact with iron are originally nearly colourless passing to brown, due mainly to the action of a laccase on the polyphenols, and also, but to a much smaller degree, of a tyrosinase on the tyrosin of the cane. In the presence of a ferrous salt, these oxidizing ferments rapidly convert the ferrous salt to the ferric state with the formation of a dark green colour. In juices where the enzyme has been destroyed by boiling or by precipitation with alcohol, the addition of a ferrous salt does not produce the dark green colour at once, but only after exposure to the air. In addition to the naturally occurring colouring matters, others are formed by the action of lime on the reducing sugars. Schneller thinks these decomposition bodies are allied to the polyphenols, and they also form dark-coloured ferric salts. A second artificially formed colour is caramel formed at the expense of the cane sugar, and due to the action of heat. Of its chemistry and composition little is known, and it is probe’ a mixture of bodies. Acidity and Alkalinity.—Under the generally accepted theory, acidity and the presence of free hydrogen ions are synonymous terms, and an acid THE ACTION OF HEAT, ALKALIES AND ACIDS 259 is a body which, on solution in water, splits up into free hydrogen ions, carrying a positive charge of electricity and into ions carrying a negative charge. Thus hydrochloric acid represented by the formula HCl on solution in water consists of H+ and Cl— together with undissociated HCl. The strength of an acid is believed under this conception to be due to the degree of dissociation or to the number of free hydrogen ions present. Conversely, an alkali is a body which splits up into hydroxyl ions, OH—, and into a base, caustic soda in solution being under this conception believed to consist of sodium ions, Na+ and hydroxyl ions, OH—, together with undissociated NaOH. The routine analytical process for the determination of acidity depends on the use of indicators, or of bodies which change their colour, depending on whether free hydrogen or free hydroxyl ions are present. Such a body very widely used in analysis is phenolphthalein which is colourless in acid and deep crimson in alkaline solution. A normal solution of an acid is one that contains in 1,000 c.c. the hydrogen equivalent of the acid expressed in grams. Thus anormal solution of hydro- chloric acid of the formula HCl contains in 1,000 c.c. 36-5 grams of acid ; a normal solution of sulphuric acid, H,SO,, contains 49 grams of sulphuric acid, and a normal solution of caustic soda, NaOH, contains 40 grams of caustic soda ; and equal quantities of norma! solutions of acids and of alkalies will exactly neutralize each other. This statement does not imply that the strength of all acids and alkalies is the same, for, as an acid is gradually neutralized by an alkali, dissociation of the undissociated portion con- tinually takes place until all is dissociated and the end point must in every case be the same.* If, then, a material is said to have an acidity of 3 c.c. normal acid per 100 c.c., all that is meant is that 3 c.c. of normal alkali are required to induce the colour change in the presence of some suitable indicator. In the case of different acids, the number of free hydrogen ions present originally before the addition of alkali and the effects due to acidity are very different, although the test shows the same acidity in the different cases. Determination of Acidity and Alkalinity. Where the expression “‘ an acidity of 3c.c. normal’’ occurs in this chapter it is to be understood that 100 c.c. of the material required the addition of 3 c.c. of normal alkali solution to induce the colour change with the selected indicator. Alkalinity is ex- pressed in a similar way. Elsewhere in the sugar industry it is often usual to express acidity in terms of milligrams of lime per 1,000 c.c. of juice, and an alkalinity of 280 milligrams of lime per 1,000 c.c. is the same as I c.c. normal alkalinity per 100 c.c. Similarly, an acidity of 410 milligrams of sul- phurous acid per 1,000 c.c. is the same as I c.c. normal acidity per I00 c.c. In the determination of acidity and of alkalinity, the end point is the term used to denote the colour change of the indicator when the point of exact neutrality is just passed. All indicators do not show the same end point, and it is also affected by the presence of neutral salts. For technical control in the sugar industry this difference has some importance, as is ex- plained later. The indicators most commonly used in the sugar industry are litmus and phenolphthalein. The analytical routine followed by the writer is as follows :—White filter paper is soakedin a neutral solution ot phenolphthalein * Except in so far as regards some finer points which do not affect the technical correctness of this statement, 260 CHAPTER XIII in 50 per cent. alcohol, allowed to dry and cut into strips. One end ot a strip is cut off, leaving a ragged edge; 100 c.c. or other convenient quantity of the juice is placed in a suitable vessel to which (if acid) decinormal alkali is allowed to flow from a burette. As the end point is approached, the ragged edge of the paper is dipped into the juice, and, after immersion, is examined by transmitted light; the end point or exact neutrality is taken as being when a delicate orange-red colour can be detected on the transparent torn edge of the paper. Determinations sensitive to 0.1 c.c. decinormal acid or alkali can be made by this method, and, when a juice is said to have an acidity of 3 c.c. normal acid, nothing more than the result of the execution of this or a similar test is intended. If litmus be used as an indicator, results different from those found with phenolphthalein obtain, the acidity being less and the alkalinity being greater. That is to say, on titrating an acid juice with alkali, the end point appears with litmus before it is seen with phenolphthalein. This difference is of especial importance in the control of sulphitation. Normal sulphites of the formula M,SO, are alkaline towards litmus and neutral towards phenolphthalein ; accordingly, if a juice containing free sulphurous acid be gradually neutralized with an alkali, a neutral reaction will be given to litmus when both normal sulphite and acid sulphite are present. The complete neutralization and disappearance of acid sulphite and presence of free alkali is shown by the appearance of a red colour with phenolphthalein ; when this body is colourless, free acid or acid sulphite may equally be present. The natural colouring matters of cane juice also to some extent serve as indicators, three colour phases being observed. At the point where phenol- phthalein becomes pink, cane juice changes to a golden yellow; with the - addition of acid the colour changes to an olive brown, which persists over 0-5 c.c. of normal acid per 100c.c. of juice, counting from the appearance of the golden yellow colour ; the addition of more acid gives an almost colourless juice; the change from olive brown to colourless takes place very nearly at the point where litmus becomes distinctly red. These changes are prob- ably due to the presence of several colouring matters in juice. The relative advantages of litmus and of phenolphthalein in technical sugar-house control have at times led to controversy. Without doubt litmus papers are superior for routine inspection and for supervision, and generally in defecation processes juices which afford a barely perceptible bluish tint settle well; when tested with phenolphthalein papers such juices give no change of colour, and hence afford no indication of a critical point as is given by litmus. For the definite expression of analytical results, however, the end point as afforded by phenolphthalein is much sharper and more distinct. In the carbonation process, moreover, the appearance of a very faint pink with phenolphthalein forms one of the critical points. The Action of Acids on Cane Sugar.—Cane sugar in acid solution is con- verted into equal parts of glucose and of fructose. This process is vulgarly called inversion, and is actually an hydrolysis, the acid acting as a catalyst. Symbolically, the process follows the equation :— C,25H2O), =e EO C.H 0, = C5H,205 The rate of inversion is dependent on the concentration of the hydrogen ions, or on the strength of the acid used, and actually the study of the hydrolysis of cane sugar is one of the classic methods by which the strengths of acids THE ACTION OF HEAT, ALKALIES AND ACIDS 261 were determined. The principal experimental observations connected with the inversion of cane sugar are given below :-— 1. Rate of Inversion.—When all other conditions are unchanged, the rate of inversion is proportional to the active mass, t.¢., when the temperature and the concentration of the acid are unchanged, a 20 per cent. solution of cane sugar inverts twice as fast as a Io per cent. solution. Developed mathematically, this statement becomes reduced to the following form :— In a sugar solution let there be a parts of sugar present ; in a small interval of time, f, let x parts be inverted. There are then present a—x parts of cane sugar. Since the rate of change is proportional to the active mass, ts = k (a—x) where & is a constant. Whence, by integration, log — =k Ss I a ass | ed or Fah seers Rk The constant & gives a means of comparing the strength of different acids, or, under the ionic hypothesis, the degree of dissociation. This law was found experimentally by Wilhelmy™ in 1850, and developed on a priori reasoning by Guldberg and Waage ! in 1867. It forms a typical instance of the universal law that rate of chemical change is proportional to the active mass. As definitely applied to a sugar solution in acid medium, let the total change in polarization due to inversion be a; then a is proportional to the amount of sugar originally present. Let the fall in polarization, 7.e., the algebraical difference between the initial reading and the reading after any time interval, #, be x ; then x is proportional to the amount of sugar inverted. The calculation of the constant will then appear as in the following example. Initial reading, 40°; reading after complete inversion, — 12°; total change = a = 52°; reading after 60 minutes, 30°; proportionate amount of sugar inverted = x = 40—30=10. Then Constant = — log ee 0001546. 60 52 — 10 2. Influence of Acid.—The constant k was determined by Ostwald?* in 1884 for a large number of acids; some values as found by him are given -below. These are referred to half normal strength, to 25° C. temperature, the time being expressed in minutes, and the logarithms being common ones. Acid. Constant. Acid. Constant. Hydrobromic 0-002187 | Sulphurous .... «-- 070006630 Hydrochloric 0: 002438 Oxalic ... 5 --. 0*0004000 Nitric ee 0-002187 | Phosphoric ... -. 0° 0001357 Sulphuric O* OOII72 Acetic... sce --. 070000088 3. Effect of Concentration of Acid—Within comparatively narrow limits the rate of inversion is nearly directly proportional to the concentration of the acid. With the stronger acids, however, the rate of inversion decreases more rapidly than does the decrease in concentration ; with weaker acids, the re- verse holds. 262 CHAPTER XIII 4. Effect of Temperature-—The following empirical equation, due to Urech?4, connects velocity of inversion and temperature :— A(T, —T)) Cy=Cye 7.7, where C, and C, are the rates of inversion at 7, and 7Jj, e is the base of the natural system of logarithms, and A is a constant, and equal to 12820. Putting the rate of inversion at 25° C.=1, this expression gives the following rates of inversion at the stated temperatures :—- 2G: Rate °C Rate oC: Rate 215 aaa I | (Bor Maasase 9g1°8 elghen HOSICo 1354 ZNO) tsoe ate 70) Obe erect 162 GOmecerser 2110 Tia ber oo 14°3 | fe) Goocor 282 OGiaiecosre 3573 OW neciciaie 26°7 TS. 6 2800K 483 TOO si sree 5659 55 aisens 57°7 S10). osdonc 814 The Effect of Neutral Salts—It was originally shown by Arrhenius that the rate of inversion by acids was accelerated by the presence of the halides and nitrates of the alkalies and alkaline earths. The writer!® has extended his observations, and has found :— 1. In concentration up to 0-02 N at 100° C., the halides and nitrates have an inappreciable effect on the rate of inversion with very dilute acids. 2. Under similar conditions the sulphates, sulphites, oxalates, and all alkali and alkaline earth salts of weaker acids retard inversion. 3. In concentration of acid and salt of the normal order, at ordinary temperatures, the halides and nitrates of the alkalies and alkaline earths accelerate the rate of inversion; the acceleration increases progressively from chloride to bromide, to iodide, the effect of nitrates being similar to that of chlorides. A difference in the base of the salt has very little, if any, effect ; thus, the acceleration due to the sodium chloride is substantially the same as that due to calcium chloride. 4. Under similar conditions, sulphates, sulphites, oxalates, etc., retard the rate of inversion. Effect of Invert Sugar.—The action of invert sugar on the inversion of cane sugar is a peculiar subject, some investigators finding that invert sugar of itself caused inversion, and others observing no effect. Geerligs!’, in investigating the subject, came to the conclusion that invert sugar of itself had no invertive action, but that in the presence of neutral Salts, such as chlorides, nitrates and sulphates of the alkalies and alkaline earths, inversion occurred at the temperature of boiling water, owing to a slight hydrolysis of the neutral salt under the influence of the invert sugar. The writer? in investigating the same subject, failed to obtain any trace of inversion due. to the combined influence of invert sugar and neutral salts, when the latter were present in normal concentration. Inversion under Acid Salts —Salts of the heavy metals, such as zinc sulphate, also cause the inversion of cane sugar. This has been chiefly studied by Long?® ; the inversion is ascribed to the partial hydrolysis of the salt, thereby affording free hydrogen ions in solution. Inversion under the Influence of Enzymes.—Besides chemical inversion under the influence of acids and acid salts, cane sugar is inverted by the action of certain ferments known collectively as enzymes. The enzyme most studied is that secreted by yeast, and known as invertase. The proper- ties of this body were first investigated by O’Sullivan and Thompson!9, who THE ACTION OF HEAT, ALKALIES AND ACIDS 263 found that the most favourable concentration of the sugar solution was 20 per cent., that the optimum temperature was 55° C. to 60° C., the enzyme being slowly destroyed at 65° C., and instantaneously at 75° C. The action of invertase is greatly accelerated by minute traces of acids. O’Sullivan and Thompson found that the law of mass action held for the action of invertase, a result not obtained by subsequent workers until C. S. Hudson?® showed that these had neglected to take into account the mutarotation of the invert sugar formed. Other instances of enzyme inversion that are of interest are the deteriora- tion of cut cane by an invertase which, as shown by Browne,’ is located chiefly in the upper portion of the stalk, and which diffuses into the lower portions of cut cane. The deterioration of stored sugars may also be properly ascribed to enzymes secreted by bacteria, moulds and yeasts. In another field Lewton Brain*' showed that the fungus causing red rot of the stem (Colletotrichum falcatum) also secreted an invertase causing the inversion of cane sugar. The processes of inversion due to enzymes obey the same laws as under acid inversion. In other similar biological changes this has been established by Arrhenius* and his pupils. Here, too, temperature is a factor of im- portance. The more rapid deterioration of cut cane in hot weather is well known, and Browne” also has called attention to an increase in the deteriora- tion of stored sugar in hot weather, and its almost complete cessation at 20° C. The Inversion of Sugar in Cane Juices.—The system in cane sugar manu- facture when acid juices are boiled consists of sugar, neutral salts of weak acids principally with a lime or potash base, and a certain amount of free acid generally either sulphurous or phosphoric. The amount of free acid present as indicated by analysis in a system consisting of sugar, water and acid only would at a temperature of 100° C. very rapidly invert all the cane sugar present. Owing, however, to the inhibitory effect of the neutral salts of weak acids, or, in the language of the ionic hypothesis, to the reduction in the number of hydrogen ions, very acid juices can be worked, provided the acidity is due to a weak acid, such as sulphurous or phosphoric. The actual acidity allowable will depend on the quantity of neutral salts, and this in turn will depend on the ash of the juice and on certain details followed in the course of manufacture. If a juice is heavily limed, and the excess of lime be then neutralized with sulphurous acid a neutral sulphite will be present in the juice, and its presence will permit of a high acidity without inversion ; or again, as in the carbonation process, in which some or all of the reducing sugars are con- verted into organic acids by an excess of lime, salts of weak acids are formed, which act in asimilar way. This property has been used by several genera- tions of Demerara and Mauritius sugar boilers in the manufacture of yellow and white consumption sugars. In the former district an acidity up to 2 c.c. normal acid per 100 c.c. is quite usual. As indicative of actual limits possible, the following experiments designed to simulate manufacturing conditions were made by the writer :—In the making of white and yellow sugars, the use of 5 lbs. of sulphur per 1,000 gallons of juice is excessive. This quantity corresponds to the presence of 0°03 normal sulphite salt in the juice. A juice was treated with lime until just alkaline to phenolphtha- lein, and sodium sulphite added in quantity to correspond with the presence 264 CHAPTER XIII of 0°01, 0:02 and 0-03 normal sulphite salt per 100 c.c. of juice. Phosphoric acid was then placed in the samples and the acidity determined by the routine methods of analysis. The prepared juices were then heated at a temperature of 97°-98° C for 30 minutes and examined, to determine when inversion occurred. Withconcentrations of sodium sulphite 0-o1, 0-02 and 0:03, normal inversion was detected when the concentration of the phos- phoric acid was 2:4, 4-2 and 6-8 normal per I00 c.c. of juice respectively. This experiment indicates that under the usual processes there is a very considerable margin of safety in boiling acid juices before any loss due to inversion occurs. The Effect of Higher Temperatures on Cane Sugar.—Cane sugar at tem- peratures as low as 40°C. suffers some change and caramelization, as has been shown by Bates and Jackson?! in their studies on the preparation of a pure sugar for a polariscopic standard. The destruction is, however, very small, and has no bearing on manufacturing losses. The original investigation on the effect of high temperatures was made by Pellet®5, and the results most often quoted are those of Herzfeld?*, and the subject has been studied later by Hazewinkel?’, Douschsky?’, Zu: ew?® Pokorny*® ,Deerr! and others, mainly in connection with the extended application of the pre-evaporator. Some of Herzfeld’s results in which sugar solutions with an alkalinity of 0-or to 0-05 per cent. were heated in metal containers are given below, the figures referring to the sugar destroyed in one hour as a percentage on the sugar originally present. The solutions were made alkaline to inhibit the secondary action of the acids formed from the sugar, which would be much greater than that due to heat alone. PERCENTAGE OF SUGAR IN SOLUTION. Tempy Ge Ke) I5 20 25 30 So 0*0444 0* 0373 0*0301 0*0229 O* 0157 go 0+0790 0+ 0667 0°0541 0: 0418 0+0290 100 O*I140 0: 0961 0:0781 0+ 0602 0* 0523 IIo 0* 1630 0+ 1362 0: 1083 0:0825 00557 120 0: 2823 0+ 2582 0+ 2341 0: 2098 00-1857 130 2°0553 I* 7582 I+ 4610 I+ 1638 0: 8667 Evidently between. 120°C and 130°C the rate of destruction increases very rapidly. It is to be noted that these results were obtained in the presence of small quantities of alkalies. The products of the decomposition of sugar are acid, and hence on continued heating two factors are at work, the con- tinued breakdown of the sugar molecule and the inversion of the sugar by the acid formed. This last factor becomes active only when the free alkali has been neutralized and even then the salt formed continues to exert its inhibitory action, as explained in a previous section. In experiments made by the writer it was found that the nitrates, halides, and sulphates of the alkalies and alkaline earths accelerated the rate of destruction of sugar at higher temperatures, salts of weaker acids retard- . ing the rate. In cane juices, as explained in a previous section, the quantity of neutral salts and acids is variable. To determine what should be the safe acidity at which juices could be heated in a pre-evaporator, the writer made the following experiment :—Defecated cane juice of an acidity 0-5 normal was reduced to the acidities shown in the annexed table by the addition of either caustic soda or of oxalic acid. Oxalic acid was selected for use, as a THE ACTION OF HEAT, ALKALIES AND ACIDS 265 precipitate of calcium oxalate would form and the system as regards the introduction of neutral salts would be unaffected. The prepared juices were then heated in an autoclave for thirty minutes at a temperature of 115°C corresponding to a pressure of ro Ibs. per square inch. The results were as below :— Acidity, Polarization gravity purity. Gravity purity. Onginal ae 83°51 iS 84-78 fe) 83-70 85-02 o-2 83°81 85-06 O*4 83-82 85°27 0-6 83°61 84°93 0-8 83-46 84:91 I-o 83:00 84-66 sy 82:53 I*4 82-08 I-6 80-16 1-8 79°71 2°0 77°10 The Action of Alkalies on Reducing Sugars.—-If a solution of reducing sugars, whether all dextrose or all levulose, or a mixture of these in any proportion, be left for a sufficiently long time in contact with even very dilute alkali, a material is eventually obtained which is almost optically inactive. At higher temperatures the change takes place very rapidly. On analysis it will be found that the reducing power has also slightly de- creased. This behaviour, which was first observed by Dubrunfaut*?, has been explained by Lobry de Bruyn and Van Ekenstein**, who have shown that it is due to an isomeric change, the final position of equilibrium being obtained with a mixture of glucose, fructose, mannose and glutose. Glutose which has not been obtained in a crystalline state is said to have only half the reducing power of the other sugars, and to its presence is due the major part of the reduction in reducing power. It is to be observed that with dilute alkali there is no actual destruction of sugar, but only an isomeric change. In cane juices the combination of reducing sugars present nearly always is levo-rotatory. In the process of manufacture part of this levo-rotation is destroyed so that the net dextro-rotation of the juice increases, and a fictitious and unreal rise in purity may often be observed under conditions where no purification is possible, and this change in rotation is accompanied by a fall in the reducing power poiting to a loss of “ glucose.” The extent of this rise in purity will depend on the alkalinity of the juice, the temperature, and the duration of exposure. It may easily reach one unit, and can be observed between defecated juice and syrup, under conditions where the only material removed is water. The following observations were made by the writer*? on juice with an acidity of about 0-5 c.c. normal per 100 c.c., referred to phenolphthalein as indicator. The juice was exposed in a pre-evaporator to a temperature of 110° -112° C. for from Io to 12 minutes. Each determination was made on a sample collected at intervals of 5 minutes over a period of half an hour. Polarization gravity purity before heating. Polarization gravity purity after heating. 85°22 = 85:86 84°97 oe 85°99 84°44 vee 85°33 85°41 ste 85:82 85°12 85°22 83°45 84°53 83°22 83-61 a°5 oes 5 Mean 84-55 nee 85-22 266 CHAPTER XIII In the presence of larger quantities of alkalies, the reducing sugars are actually destroyed. The products of decomposition are dependent on the temperature. At temperatures below 60° C. the chief products are saccharic and lactic acids, with only small quantities of glucinic acid. Above this temperature glucinic acid is formed in large quantity. This body forms a basic glucinate with lime, which is insoluble in alkaline solution and is of a dark brown colour. At temperatures near the boiling point, the whole of the reducing sugars are rapidly destroyed as well as these dark-coloured bodies, but the action has not been completely examined, Action of Lime on Cane Juice.—If lime either in a thin suspension or as saccharate be added to a cane juice, the first effect is the neutralization of any free acid present. The continued addition causes the appearance of a precipitate consisting in part of those bodies referred to in a previous chapter as colloids. There is also precipitated the phosphoric acid which is always present and some small quantity of aluminium and ferric oxides. In the precipitate is contained most of the nitrogen that is present in the albuminoid form, the chlorophyll, cane wax and some of the colouring matter. The actual weight of the precipitate due to the action of different quantities of lime was found to be as follows :— To a juice which had an acidity of 3-2 c.c. normal per Ioo c.c. with reference to phenolphthalein, lime in the quantities indicated below was added, and the weight of the precipitate determined. Acidity of juice Lime used as Weight of pre- Weight ot in normal c.c. CaO ; grams per cipitate per ash in per I00 c.c. 100 C.C. I0O C.C. precipitate. Bez fo) 0*242 0-012 2a 0° 013 0-248 0: O14 Pye. 0: 026 0+ 264 0: 024 1-8 0+ 039 0: 288 0+ 030 I°4 0*052 0+ 320 0*044 o°9 0*065 0+ 340 0: 070 Or5 0:079 0*370 0-088 o 0+ 092 0: 408 0+ 104 0-5 (alkaline) O* 104 0+ 406 O:112 The maximum quantity of precipitation is seen to be reached as soon as the juice becomes alkaline towards phenolphthalein. As explained in the previous chapter, heat or filtration alone removes the colloids from solution, ~ so that the action of lime and these agencies overlaps. The peculiarly specific action of the lime is the precipitation of the phosphoric acid. The figures given above refer to a juice which had been freed from the grosser particles of suspended matter by filtration through glass wool. The Fate of the Lime in Contact with Cane Juice.—A portion of the lime which is added to cane juice remains in solution, and a portion is found in the precipitate as shown in the following experiment :-—-To 100 c.c. of cane juice which contained 0-045 gram lime as CaO per 100 c.c., successive quantities of lime were added, and the quantity of lime remaining in solution determined, with the results shown below. THE ACTION OF HEAT, ALKALIES AND ACIDS 267 Acidity of juice Grams lime as CaO Lime added as CaO c.c. normal acid in solution per grams per I00 C.c. per 100 c.c. 100 C.c. fo) 3°2 0*045 0-013 2°7 0:050 0: 026 Zaz 0-066 0+ 039 1-8 0-078 0°052 BoA. 0-078 0-066 0-9 0-084 0-079 O°5 0-100 0+ 092 fo) O-112 Experiments by Cross®* gave the results tabulated below. In these experiments neutrality refers to the indication afforded by litmus. Juice limed to acidity Grams lime in of......c.c. normal per solution per 100 C.c. IOO C.c. Nowimes 6 Pa acces. 0+ 065 Ee yr ga Shahn WG ewes: 0-080 figs Oger sy penta ae rors 0-085 Onn ogra A a. ce 0-087 INGHGhALs< 532 Sik) pose 0+ 094 o-5* O-1I5 BOr <8" BE Less oO: IIg <= pari G2 0 elas ene eee 0-096 Sahl Gis CS Ue Pr oe 0-106 ie OM Te ee Ren. Sse 0-128 AETAS! S/o ha wie ed sen ee 0° 136 oO nar! potas 0-148 25 Ga'2 See Res bp Meek 0-179 aon 52 ONG SS Py Oa Foc ack o: 189 = Eel Die” Man ences 0-214 Hence as the quantity of lime used in defecation increases, so does the quantity of lime salts in solution. It was also demonstrated by Cross that the action of sodium carbonate of phosphates in removing the lime salts is very small. The Rise in Purity of Cane Juices due to the Combined Action of Heat and Lime,—A rise in purity in a cane juice can only be obtained by the removal of non-sugar from solution. Removal of suspended solids does not mean a rise in purity. In the experiment quoted above, the juice contained 16-0 per cent. of gravity solids, and polarized 13-12, being of polarization gravity purity 82:00. With the addition of 0-052 grams of lime, the gravity solids become 16-048, and the precipitate being 0-310 gram there are left in solution 15-738 gravity solids. The polarization gravity purity must now be 83:26. For other quantities of lime the calculated purity will be :— Lime added grams Polarization gravity per 100 c.c. of juice. purity. fe) aes 82:00 0° 013 Ve 83°25 0+026 ape 83°25 0*039 “isc 83°35 0*052 oe 83°41 0+ 065 se 83°47 0-079 sec 83°57 0-092 se 83-69 The weight of the material removed by filtration alone was determined for this juice, with the result that the purity of the filtered juice was found to be * Alkaline 268 CHAPTER XIII 83-29, arise of 1-29 units, or 76 per cent. ofthe most that can be obtained by the combined action of heat and lime. It follows, too, that processes which claim an abnormal rise in purity may be best examined by a demand that their advocates produce the non- sugars removed from solution. ee BOSS Se ee eaaty ieee oH O 12. db bD DO & S&S 4 HH SH HS HF DETR TORO E00 SI une WwWWwWWwWWwWWw DH DH KH KH NH ND HN AROH TOO HIAALY REFERENCES IN CHAPTER XIII Int. Sug. Jour., 1916, 17, 502. Ber., 1894, 27, 1747. Ini. Sug. Jour., 1912, 13, 53- Biochimie der Pflanzen, 1, 567; 2, 562, 965. ‘ Berichte de Vereins station fiir Zuckerrohr in West Java, 2, 13. Java Arch., 1896, 4, 532. La. Ex: Stat; Bull. ox. La. Plant., 1916, 57, 238. La. Plant., 1919, 61, 299; Jour. Ind. Eng. Chem., 1919, II, 1034. Java Arch., 1906, 14, 882. Poggendorf’s Annalen, 1850, 81, 413. Fortandlingen i Videnskats-Silksabet, 1865, 2, 35. Jour. prak. chem., 30, 95. Ber., 1887, 16, 765; 1888, 17, 2175. Zeit. Phys. Chem., 4, 226. H.S.P.A.; Ex. Sta., Agric. Ser., Bull. 35. 5G, 1895,.27> 404. Jour. Am. Chem. Soc., 18, 693. Jour. Chem. Soc., 1898, 57, 834. Jour. Am. Chem. Soc., 1910, 32, 889-894. Fes PVA: Ex. Sta.,, Path: Ser:, Bull. -7. “ Immuno-Chemistry : Applications of Physical Chemistry to the Study of Biological Antibodies.”’ Jour. Ind. Eng. Chem., 1918, 10, 3. Bureau of Standards, Bull. 268. Bull. Assoc. Chim. Suc., 1878. “Cane Sugar and its Manufacture.’’ Geerligs. TS] eLOUls 252) eLOu2, #212: Deut. Zuckerind., 1910, 35, 944-945. Bull. Assoc. Chim. Suc., 1910, 28, 406-407. Oest.-Ung. Zettsch. Zuckerind., 1908, 37, 359-380. H.S.P.A, Ex. Sta., Agr. & Chem. Ser., Bull. 36. Comptes Rendus, 42, 90l. Java Arch., 1896, 2, 224. Teel] ee OLO m5 Ox: Le) se tOEA) 2i7s CHAPTER XIV THE DEFECATION OF CANE JUICE By defecation* is understood the process by means of which a clear negotiable juice is obtained by the combined action of heat, lime, settling and decanta- tion. This simple process is that which is used in the manufacture of 96° test sugars, and in combination with sulphurous and phosphoric acids, in the manufacture of plantation white and yellow grocery sugars. The Mechanism of Settling —The general law under which bodies fall through a resistant medium was first given by Stokes!: p23 Gunde) 128 § B where v is the velocity of the falling body, d, and d, are the densities respect ively of the falling body, and of the resistant medium, 7 is the radius of the body, g is the acceleration due to gravity, and pu is the viscosity of the resistant medium. in a cane juice d, and y will not suffer much change from juice to juice; d, will vary . between the limits 1-05 and 1-08, and of the change in » nothing is known except that it will fall rapidly with rise in temperature, and that otherwise it will not vary greatly. However, d, will always be much larger than d,, so that change in the latter will not affect the value of d,— d, enough to be of importance in design. It follows then from these considerations that the settling of one cane juice should be typical of all, and that settling should, over a great part of the process, take place at a uniform rate. If the settling of a suspension such as alumina hydroxide, of concentration about 0-2 gram per I00 c.c. be studied in a tall, narrow tube, there will be seen a short preliminary phase lasting about two minutes, during which no individual particles can be recognised, and over which no settling occurs. After settling has begun, the system soon resolves itself into five zones. The uppermost zone, I (Fig. 154) is quite clear; next in order is zone 2, characterized by the presence of isolated falling particles which may be called stragglers. These stragglers terminate in a zone 3, about 0-5 c.m. deep, in which the particles have only a vertical downward movement. Below this is zone 4, in which at an early stage of settling is contained the great proportion of the suspended matter. In this zone there can be recognised a continuous downward and upward stream of particles, the boundaries of which are the contingent surfaces of zones 3 and 5. Zone 5 consists of those particles that have come to rest on the bottom of the tube, or later on the top of the column being built up. The upward and downward stream of particles in zone 4 will be seen to be continuous; as upward-moving particles approach zone 3 they turn 269 270 CHAPTER XIV through an angle of 180° and join the downward stream. These particles have also a gyratory motion, and particles may leave the upward stream and join the downward one and vice versa. As the particles in the down- ward stream approach the top of zone 5 many particles are seen to detach themselves from the current, and, falling vertically a short distance, join zone 5; these particles then become settled particles, and thenceforth gravitate slowly downwards, so that, while it is being built up, zone 5 is sim- ultaneously shrinking. During this stage of settling, there is, however, a net increase in the height of the column. Zone 4 during the process of settling is continually decreasing in depth both from above and below, and eventually there comes a time when the system is reduced to zones I, 3 and 5, as by this time nearly all the stragglers will have caught up with zone 3. Zone 3 now very rapidly passes into zone 5, and at this moment, which can be . recognised with great exactness, the suspension may be said to have settled. This position was termed by Coe and Clevenger? the critical position, and this term will be adopted here. At this moment there is a rapid decrease in the rate of settling, which now becomes progressively slower and slower. The following principles were found to hold in a study of the settling of suspensions of alumina hydroxide. Let c=concentration of the suspension, #=height of the column at the commencement of settling, d=height of the column of settled material at the critical position taking place at time 2. ; h=a I. When is constant, ae constant, and =< = constant. 2. For values of c up to 0-08 grams per 100 c.c. the value of (h—d) /t remains constant, i.e., the particles fall independently of each other, and. consequently the value of ¢ (h—d) /t is proportional to e. 3. For values of c 0-08 to 0-50 grams per 100 c.c. the value of (4—4) /t de- creases, but at the same time the value of c (i—d) /¢ increases until c reaches a value of about 0-2 gram per I00 c.c. From this value up to one of 0°5 grams per 100 c.c., the value of c (h—d) /t remains constant, that is to say, in unit time the same quantity of material is settled. 4. If d, be the height of the settled column at the critical position, and d, be the height when settling has become very slow, then “ = =constant, where d, is the height of the settled column at Pee act} i F log time 7. 5. If d, and d, be the heights of columns of settled material at the critical position obtained from columns of original height #, and /,, then if in time ¢ the column d, has settled to height d’, and d, has settled to d's, then d,/d', approximates in value to d,/d’,. The Settling of Cane Juice.—The mechanism of the settling of cane juice under the influence of heat and lime is essentially similar to that which has been described in detail as found for alumina hydroxide. It may be best examined in a tube of length about one metre, completely enveloped in a steam jacket. The apparatus used by the writer was developed out of a Liebig condenser, one end of which was blinded off. The results described below were obtained in such an apparatus, and before making an experiment, the juices were boiled gently for one minute in a flask fitted with a reflux condenser, so as to expel any air, the presence of which would have vitiated the experiment. THE DEFECATION OF CANE JUICE It must have been observed by anyone who has operated a cane sugar house that great variations occur in the rate of settling, and in the volume occupied by the mud. Prima facie these variations may be attributed to variation in the reaction of the juice as regards alkalinity and acidity, or, in other words, to the quantity of lime used. Accordingly, a juice which had an acidity of 1-75 c.c. normal per r00 c.c. (cf. Chapter XIII) was limed with 2-0, I-75, 1-5, 1-25, I-0,0-°75 ando-50 c.c. of normal lime suspension per oo c.c. of juice. The juices so treated were then heated to the boiling point, boiled for one minute under a reflux condenser, poured into a tube one metre long round which steam circulates, and allowed tosettle. The results obtained are tabulated below, the figures giving the depth of the clear supernatant column of juice in millimetres. The approximate position of the critical position is indicated by an asterisk. C.C. NoRMAL LIME PER I00 C.C. OF JUICE. Time mins, 2 +00 1°75 I +50 E25 I -00 0°75 0 +50 2 80 7O 100 120 160 320 570 4 190 160 240 280 450 700 700 6 320 300 400 580 760* 870 820 8 450 440 580 782* 840 888 870 10 590 580 755* $38 856 896 885 I2 742* 700* 817 856 867 goo 904 I4 787 77 841 862 874 902 gio 16 802 820 849 866 879 go2 gio 18 812 833 856 868 883 go02 gio 20 820 844 860 870 885 —- —- 22 825 850 863 872 887 - =. 24 830 855 866 874 888 — sos 26 834 858 869 876. 889 -— - = 28 839 861 871 878 890 -— — 30 843 863 873 880 Sor — = Of these juices the two with the lowest quantity of lime were ‘‘ muddy ” and distinctly underlimed ; the next in order was fairly bright, while the two following ones were bright and clear and could be taken as representative of satisfactory defecation. The two remaining juices, while quite bright and clear, were distinctly overlimed. A very great difference may be observed in the rate of settling, and also in the ultimate volume occupied by the mud. __In addition, the method of separation of the precipitate was different, the two juices with least lime affording a mud that separated in large “‘ flocks,’”’ while in the others the pre- cipitate was evenly distributed at the beginning of settling. Correlat- ing this experiment with those described in Chapter XIII, an acidity in the juice referred to phenolphthalein of from 0-25 to 0-50 c.c. normal per I00 c.c. of juice would appear to fulfi: all the conditions demanded for a good defeca- tion, 7.e., protection against inversion, a bright and clear juice and reasonably rapid settling. It is true that the maximum purification is only obtained when the juice just reaches alkalinity, but the advantages obtained by the use of less lime are to the writer’s mind of more moment. Determination of the Quantity of Lime required.—A method pursued by the writer in a certain factory was as follows :—An acidity of 0-5 c.c. normal per I00 c.c. juice was selected as standard. Lime-cream measuring vessels were prepared of volume one-thousandth that of the tanks in which the juice was received. A half-normal solution of caustic soda was prepared, and the 272 CHAPTER XIV number of c.c. necessary to make 100 c.c. of juice alkaline to phenolphthalein determined for each tank, using the method described in the previous chapter. If a lime-cream of strength 5 normal be used, then as many measuring vessels as c.c. used in the testing would make the juice just alkaline to phenolphthalein. All commercial limes are more or less impure, and it so happened that, in one case when working as above, and using the actual number of measuring vessels as indicated by the test, the desired aci- dity was obtained. The testing was done at the liming tanks, and, as each tank took six minutes to fill, there was ample time to make the test with due care. The chief difficulty was experienced in keeping the lime-cream at a uniform density. This source of trouble can be avoided by using two lime-cream agitators, each holding. about two hours’ supply of lime-cream. One container is prepared and kept well agitated by mechanical mixing; the attendant has then ample time to prepare the second tank while the first is emptying. A 5-normal lime- cream is of density 15° Baumé, and, if this is thought to be too heavy, a 2:5 normal lime-cream mixture may be used, the other solutions and containers being altered to correspond. The writer does not favour the use of automatic liming devices, since consider- able variation in acidity occurs from tank to tank, for which no automatic device can make allowance. A difficulty in operation of this scheme, and indeed of any scheme, occurs in this process in connection with the filtration of the scums. In order to obtain a rapid filtration it is necessary to lime the scums to very distinct alkalinity. If this very alkaline filtrate be then mixed with the clear defecated juice, a disturbance in the system obtains together with a second precipitation in the clear juice. To avoid this, the alkaline filtrate may be syste- matically returned to the raw juice (after the latter has been weighed or measured), when the excess of lime is neutralized, the control of the additional lime cream required being made as before. By the use of this method a clear defecated juice is obtained with a minimum of lime, and, at the same time, the advantages of the rapid filtration of the scums are retained. The Practice of Defecation.—After the juice has received the proper quantity of lime, it is necessary to raise its temperature to.a minimum of 190° F. in order to obtain a rapid settling and separation of the precipitate. The heating is done either in tubular heaters or in the tanks, which serve as. containers for the juice, or in a combination of these two apparatus. THE DEFECATION OF CANE JUICE 273 Juice Heating.—The usual type of juice heater consists of a cylindrical shell, in which are arranged tube plates at either end, the tubes passing from plate to plate. The juice circulates within the tubes, and the steam between the plates and without the tubes. By an arrangement of division plates the juice is constrained to travel in alternate directions through nests of tubes. The tubes vary in length from ten to thirty feet, the changes of direction being from three to forty in different designs. In the largest sizes in use the total length of travel of the juice may reach as much as 250 feet. In different designs the velocity of the juices will be found to vary from roo to 400 feet per minute. Latest practice seems to incline towards the adoption of a higher velocity, following on the generally accepted theory that the transmission of heat increases with the square root of the velocity. On the other hand, the higher velocity demands increased pump power. Fig. 155 shows a type of vertical heater with a three-way pass, and affording a low velocity to the juice in transit. A horizontal type designed for a high velocity with twelve changes of direction is shown in Fig. 156. The horizontal and vertical arrangement is interchangeable in these types. The diameter of tube in these heaters is usually from 1 to 1dinches. A type of heater common in Cuba consists of a steel cylindrical shell enclosing a steel spiral. The shell may be as long as forty feet, and be three feet in diameter. These heaters are used on unlimed juice, and are expected to operate a whole crop without cleaning, delivering juice at a temperature of 150° to 160° F. to defecators in which the heating is completed. The quantity of heating surface required will depend on the steam pressure used, on the liability to scale, and on the velocity of the juice in the heater. With freshly cleaned heaters, with a travel of 250 feet per minute, and with steam at 5 lbs. gauge, it is possible to heat one ton of juice per hour from 80° F. to 212° F. with Io sq. ft. of heating surface. The efficiency, however, falls very rapidly, and there should be installed 40 sq. ft. per ton-cane-hour. This heating surface may conveniently be divided into three units of 13 sq. ft. each, of which two operate while one is thrown out daily for cleaning. Instead of using tubular heaters, the juice may be heated in the vessels in which the settling takes place, and these vessels then become known as Defecators. Two styles of heating elements are used. One evidently derived from Taylor’s patent (4032, 1816) and shown in Fig. 157, consists of a system of straight tubes a, collected into a header 6, about which the system can rotate for purposes of cleaning. This system is used with rec- tangular vessels, and when provided with a gutter they are known as Elimina- tors in the British West Indies, and as Fletcher Pans in Java. They were, and still are, used to boil juices and to skim off the scums that rise into the U 274 CHAPTER XIV gutter c. They are usually provided with the syphon float discharge indicated at din Fig. 157. French practice changed the straight tubes in the Taylor system to a coil and adopted a circular vessel as shown in Fig. 158. This type is usually found provided with draw-off cocks at different levels, and is the form generally found in Cuba. In both designs, 1 sq. ft. heating surface is found per three cub. ft. of capacity. In place of either of these designs the very efficient Witcowitz heating device may be used; this, as ar- ranged in an evaporator, is shown in F2g. 205. When the heating is done entirely in tubular FIG. 157 heaters, the tanks which receive the hot juice serve merely as settling and storage tanks. In the defecator a system of flotation obtains. On applying heat the emulsioned air attaches itself to particles of the solid matter, and causes them to rise as a_ blanket to the surface. At the same time the particles of greater specific gravity fall to the bottom. Between these two layers lies the great bulk of the juice in a state of clarity. The operation of heating, once known as “‘cracking”’ requires to be carefully carried out, for, if the juice be allowed to boil, the floating blanket is broken up. Java practice in raw sugar manufacture combines the French defecator with discontinuous settling. Generally three defecators of the type shown in Fig. 157 are used, the passage of juice (together with the separation of the scum) through these being continuous ; afterwards the partially defecated juice passes to settling tanks, where the separation of suspended matter is completed. The literal translation of the term used for this operation is “troubled defecation.”’ The Design of Defecators.—If the defecator be considered as a settling tank, the fundamental factor in its design is the rate of settling. Based on the experiments described above, a rate to the critical position of 7 c.ms. per minute should be obtained, 74 the critical position being taken as 0:75h where h is the height of the tank. After the critical point is reached twenty minutes should be sufficient to so reduce the rate that further settling is uneconomical. Undersuch conditions the volume of the mud should lie between Io per cent. and 15 per cent. of the volume of the juice. A second factor in design is concerned with the conservation of heat. With circular tanks without a cover, the surface is a minimum for a stated volume, when the height is half the diameter and with square tanks when the height is half the length of one side. In addition, the exposed surface for a given volume decreases as the number of tanks decreases. There is a Fie 158 THE DEFECATION OF CANE JUICE 275 limit however to a decrease in the number of units since time for settling and decanting must be allowed, and the available time increases with the number of tanks. For example, with four units each holding a half-hour’s supply from the mills, and with each tank taking the same time to decant, only one hour’s settling is possible. With eight tanks holding fifteen minutes’ supply each, the available time for settling is increased to ninety minutes. In addition, an error in liming is more serious with the larger units, since it is generally not detected till the tank has begun to settle. With eight tanks it would be possible to cut out one tank for a round, but this could not be done with only four in the circuit. The settling tanks should be made with = the bottoms inclined at an angle of not less than 15° so that the deposit may gravitate readily to the discharge pipe. A cylinder standing on a cone forms a convenient pattern. An advantage, how- ever, in_ rectangular tanks is that every two tanks may have one common side. A useful accessory is the sight glass indicated in Fig. 159, which allows the rate of settling to be observed. The clear juice may be drawn off by a series of cocks located at different levels, or by a float and syphon discharge. This system was introduced by Sainthill in Jamaica about 1770. Although ~ some heat is thereby lost, it is perhaps better to allow the clear juice to empty into a gutter rather than into a closed pipe, as a better opportunity for inspection is afforded. Continuous Settling.—In place of the intermittent system, continuous arrangements have been installed in some factories. The form due to Pickering and Macgregor, (patent 4834, IgoI), is indicated in Fig. 160. The juice enters at a, fills the annular space }, and flows upward at a very slow velocity until it overflows into the gutter c, passing away at d. The dirt at the same time settles on to the side of the cone e, from which it is removed by the scraper f, eventually being discharged by the outlet g. When it is necessary to clean the vessel, the clear juice in the cylinder can be run out by the outlet h. 276 CHAPTER XIV The continuous settler known as the Colonial Sugar Co.’s type is shown in Fig. 161. The dirty juice enters at a, and is constrained to flow in a horizontal spiral by means of the baffle b. The deposit of dirt takes place in a direction at right angles to that of flow. The clear juice overflows at c. The mud deposited on the sides of the cane is removed by the scraper d, and finally passes out of the system at e. At the factory of the Hawaiian Commercial and Sugar Co. there are ten such settlers, each 18 feet in diameter at the top, and goo c. ft. in capacity. As they treat the juice from about 120 tons of cane per hour, the rate of flow at exit calculated over the whole capacity will be 1-5 feet per hour. The continuous settling tank of Corne and Burguiréres (U.S. patent 1,190,863) is shown in section in Fig. 162. The principle of this arrangement is the preliminary deposition of the dirt on the inclined planes, whence it gradually falls off and drops vertically to the bottom of the tank. In the last tank as the juice flows upwards it is strained through cloth. The Dorr continuous clarifier has recently been introduced into Cuba, where it has been operated at the ‘‘ Mercedita”’ Central of the Cuban-Ameri- canCo. In Fig. 163 is shown an installation designed to heat the juice from 2,500 tons cane per day. It consists of a tank 20 ft. in diameter, and divided into four compartments by the inclined trays a. Juice limed and heated as usual to 212° F. enters by the pipe 0 and fills the tank by the large cen- tral conduit c. That mud which does not at once fall to the bottom deposits on the tray of | \ each: compartment; 2 ana whence it is directed by the slowly rotating scra- pers d to the central conduit, down which it gravitates to the en- trance to the pipe line e, through which it is drawn by the diaphragm pump f, and sent to the : mud tanks. The clear Fic. 16% juice is drawn off from the upper surface of each compartment through the pipes g, all of which ter- minate in the inspection box h, whence the clear juice passes by way of & to the evaporators. The pipe shown at /serves as a circulating pipe, and those at m THE DEFECATION OF CANE JUICE 277 and are used to empty the apparatus. Air vents areshown at 0. The cen- ~ trally located box into which the juice is conducted is provided with an overflow 1 — = a VL LLL LLL SSLLLLLSLSSSLLL ELS STLELL LE OLELLEPLLPLEEL EEL SPLLLD Ko Koa = 5 0 Fic. 162 to mechanically remove foam and floating particles. The superstructure shown is for the purpose of carrying the gear required to operate the scraper and pumps, while manholes afford access to each compartment. Fic. 163 In Mauritius the clear juice obtained from the defecators is often allowed to flow in a slow current in an open shallow tank called a Bac Portal. In the 278 CHAPTER XIV tank are a number of deflecting plates by means of which the juice is made to change its direction. During its passage the juice is continually deposit- ing its suspended solids. Flotation of the scums has also been applied to continuous settling, as for example in Harvey and Scard’s patent 6093 of 1899. It also forms a part of Rillieux’s second patent on multiple effect evaporation. In the Hatton continuous defecator, Fig. 163a, the cold limed juice enters the vessel by the pipe C through the valve B and header A. As the vessel fills, juice flows into the interior vessel D, which is closed at the bottom, and thence FIG. 1634 upwards through the pipe C, and away by the pipe F to the clear juice conduit. The scums collect on the surface of the juice and are removed from time to time. Heavier particles which settle are distributed by occasional rotation of the scraper, and are then intended to be carried upwards to join the © floating layer. The temperature is controlled by a thermostat, consisting of a tube (shown below JD) filled with water, the expansion of which acting on the diaphragm fixed at the right hand side of the defecator (as shown in the figure) operates the balanced valve above it. ‘ The Williamson continuous defecator (U.S. patent 1,317,607) has been installed and successfully operated in one or two American refineries on THE DEFECATION OF CANE JUICE 279 sugar liquor of 60° Brix defecated with lime and phosphoric acid. It consists (Fig. 164) of an aerating vessel, air at 15 Ibs. gauge entering by the perforated pipe d. The aerated material then passes by the pipe 6 into the separating tank provided with steam coils and vertical baffle plates. The precipitate, to which the air bubbles have attached themselves, rises to the surface and continually passes off into the gutter 8, its motion being aided by two hori- zontal rollers not shown in the drawing. The clear liquor is also continuously removed by the pipe 7. After long intervals particles which escape aera- tion and deposit on the bottom are removed. At the time of writing, the author is unaware of the adaptation of this apparatus to juices. Although only indirectly connected with defecation, the Thomas-Petree process can be referred to here. As described for a three-mill combination in U.S. patent 1,266,882 the juice from the first mill is treated separately, the defecation mud there obtained being mixed with diluter juice coming from the second mill. A _ second defecation obtains here, the clear juice joining the first mill juice prior to defecation and the mud being pumped over the ba- Fic. 164 gasse on its way to the second mill. Imbibition water is applied before the third unit, and the juice here ex- pressed forms as usual the diluting agency for the imbibition at the second mill. This process, which eliminates the filter-press station, is at the time of writing in extensive use in Australia. Centrifugal Separation.—Bessemer’s patent (13202, 1850) contains the first notice of this means. He proposed to filter the juice through flannel in a centrifugal, and also aimed at making the process continuous by re- moving the matter intercepted by the flannel by scrapers moving a little faster than the basket. Possoz’ patent (1859 of 1861) introduces the double carbonation process, and includes the separation of the lime sludge in an imperforate centrifugal with continuous discharge of the clear effluent over the lip. This same means is found in the later patents of Laidlaw (1188 of 1897), of Herriot (29286 of 1897), of Hignette (28589 of 1897), of Kopke (29640 of 1913) and in various others. All these adhere closely to the sugar drying type, and none have come into general use, REFERENCES IN CHAPTER XIV. 1. Tvans. Cambridge Philosophical Soc., 1855, 9, 8. 2. Tvans. Amer. Inst. Min. Eng., 1916, 55, 336. COAPTER \XV THE CARBONATION PROCESSES In the carbonation processes a very great excess of lime is allowed to act on the juice, the excess of lime being eventually removed as carbonate through the action of carbon dioxide gas which is pumped through the material contained in special tanks. Actually the schemes would be more rationally termed ‘“‘ excess lime processes,’ as the effects produced are essentially due to the lime, the réle of the carbon dioxide being only secondary. The inception of these processes is to be found in the beet sugar industry, where an excess of lime was thus first removed by Scatter in Germany in 1843. He was followed by Kihlmann and by Rousseau, who described the single carbonation process in patent 14318, 1858. The double carbonation process is due to Possoz, Perrier and Cail in France, and to Jelinek and Frey in Austria. The three first-named inventors described the process in patents 1861 of 1859 and 28 of 1870. The system was first adapted to cane sugar manufacture by Pellet, and was first used in the cane sugar industry in Java at Wonopringo and Djattiwangi in 1878. It was used at an early period at Almeira in Spain, and as Boivin and Loiseau’s “‘ hydro-sucro-carbonate ’’ process in Australia in 1870. It has been sparingly used in the Hawaiian Islands. At the present time some twenty factories in Java, together with at least one each in Egypt and British India, operate the process. Carbonation processes are only used where a white sugar for direct con- sumption is made, and as now conducted carbonation is combined with sulphitation, the application of which is discussed in the next chapter. Chemistry of the Processes.1—In Chapter XIII it was stated that when a juice has been limed so far that it is just alkaline to phenolphthalein, no further precipitation takes place with the continued addition of lime, and it would therefore appear to be irrational to add more lime still. When, however, there is a great excess of lime, which is afterwards precipitated in the juice, the calcium carbonate formed carries down mechanically much of the colouring matter not yet precipitated, as well as much of those indefinite bodies referred to as ‘‘ gums.” A secondary, though very important, effect is the ease with which such a material can be filtered, due to the presence of the granular precipitate. Cane juices normally contain a considerable quantity of reducing sugars, and the action of lime on these bodies is of great importance. _At tempera- tures not above 50° C. the main product of the action of lime is lactic acid appearing in the juice as lactates. These salts are stable and colourless and do not form basic combinations. As the temperature of reaction rises, 280 THE CARBONATION PROCESSES 281 glucinic and saccharinic acids are formed. These bodies are unstable and form dark-coloured basic salts, which are insoluble only in alkaline solution. With a still continued rise in temperature a more profound decomposition obtains, with the formation of acetic, formic, and carbonic acids, the dark- coloured basic bodies being broken down to simpler colourless combinations. As a result of these reactions several methods of operating have been devised. Single Carbonation.—The raw juice is received in tanks, and is at once mixed with 7 to Io per cent. of its volume of milk-of-lime at 20° Baumé, corresponding to 1-5 to 2-0 per cent. of dry lime on the weight of the juice. Fic. 165 As described in the earlier Java publications, the temperature of reaction was 60° C., reduced later to 55° C., and now finally given as lying between 45° C. and 55° C., and as near as possible to 50°C. At this temperature very little destruction of reducing sugars takes place, and no darkening at all due to the formation of basic salts. After the addition of lime, carbon dioxide is pumped into the juice, causing the precipitation of the lime as carbonate. At a certain stage of the process the juice becomes very viscous, due to the formation of a complex body, hydro-sucro-carbonate of lime, C,,H5.04;, 2CaO(OH),, 3CaGO,. At this stage the juice froths violently, due to the very imperfect absorption of the gas. With continued gassing this complex body is broken up, and eventually a product with an alkalinity of about 60 mgrms. CaO} per litre, corresponding to 0-02 c.c. normal per 100 c.c., is 282 CHAPTER XV obtained. This point is indicated by a faint pink coloration on phenol- phthalein paper. The carbonated juice is now pumped to the filter presses. In the earlier applications of single carbonation, it was customary to raise the temperature to 90° C. before filtration, an operation no longer followed. Double Carbonation.—The double carbonation process is conducted similarly to the single one up to the breaking up of the sucro-carbonate. At this point the precipitate settles rapidly, the alkalinity being from 0-14 to 0:18 normal per Ioo c.c., corresponding with the presence in the juice of from 400 to 500 mgrms. of Cad per litre. At this alkalinity phenolphthalein papers are coloured bright red, and so do not afford a criterion. Resource is then had to “ Dupont” paper, made by soaking phenolphthalein papers in oxalic acid of such strength that at this alkalinity they are coloured a barely perceptible pink. This determination is checked by direct titrations as considered necessary. The material is now filtered and the clear filtrate received in tanks, where it undergoes the second carbonation. This is con- tinued up to saturation, when the juice is boiled for a few minutes to break up bicarbonates and again filtered. In the earlier descriptions of the process great stress was laid on the importance of the first filtration in alkaline medium, so as to eliminate the basic dark-coloured salts. These statements referred to a process in which the lime was allowed to act at 60° C. It appears that when operating at 50° C. these bodies are not formed, so that the advantages of double carbonation tend to disappear, and indeed Harloff and Schmidt? dis- tinctly state that the differences between the single and double processes are very small. The double pro- > cess is, however, safer, and opportunity is afforded to correct any error that arises in the first operation. De Haan’s Process.2—In this process the lime is added gradually while the carbon dioxide is being pumped into the juice, the other details being as already described with the exception of the quantity of lime used. Under these conditions the calcium Bic: 566 carbonate is formed in a very granular condition and the lime used is only 1 per cent. on the weight of juice, indicating a corresponding saving in coke, dilution, and filter cloths. There is also no formation of the sucro-carbonate, with consequent elimina- tion of the troublesome frothing. Battelle’s Process.*—Battelle’s process reverses the general trend of the carbonation schemes by allowing the lime to act at the boiling point, whereby the reducing sugars are entirely eliminated, affording the final colourless products of complete breakdown. In other respects the process follows the usual routine. This scheme, while giving means to obtain a superior planta- tion white sugar, affords a molasses from which the sugar may be extracted by the Steffen process of substitution, as is done in the beet sugar industry. Up to the present this process has not been worked on the large scale, but the truth of the inventor’s revolutionary proposals has been demonstrated in large-scale experiments made by the Hawaiian Sugar Planters’ Association. THE CARBONATION PROCESSES 283 Apparatus employed in Carbonation Processes.—The specialized apparatus employed in carbonation are described below. Carbonation Tanks.—The tanks used in the first carbonation are plain sheet-steel circular or rectangular tanks, of height up to 20 feet, and of dia- meter dependent on the capacity required. At the bottom is arranged a perforated coil or cross where is introduced the gas. A steam coil, or, more usually, a Witcowitz heater (see Fig. 205) is also provided. Other accessories are mechanical stirring gear, including a scraper following the slope of the bottom to remove precipitate settling thereon. The stirring gear may also carry blades to break up the froth that forms during a period in the carbona- tion or otherwise this may be dispelled by a jet of steam or of compressed air. The tanks are often provided with a chimney to carry away the un- absorbed gases. A section through a typical form is shown in Fig. 165. The second carbonation tanks are similar to the first, save that the appliances connected with the foam are dispensed with, and that the additional height required for this same purpose is avoided. Continuous carbonating tanks are also used to some extent, especially for the second carbon- ation. A type is indicated in Fig. 166. For first carbonation tanks it is customary to allow a gross volume of 40-50 cu. ft. per ton- cane-hour divided into four or five units. This refers to the gross capacity of the tanks, a height of 10-12 feet being left above the level of the juice to allow for ieee foam. For second carbonation a capacity of 15 cu. ft. per ton- cane-hour divided into three units =" is customary, a dead space of three feet being sufficient. The first carbonation occupies from Io to 15 minutes, from 3 to 5 minutes being required for the second. ill 0e00e00 eo 2 0e000 fle © 02800}! ||I! [ Gas Washer.—The carbon dioxide used in this process is, of course, generated on the spot by burning limestone; after being generated in the kiln, the gas is passed through a gas washer, a form of which is shown in Fig. 167. It consists of an upright cylindrical vessel, in which is placed a series of transverse horizontal partitions e; in each of these, and projecting a few inches, are fitted the funnels f; water is pumped into the vessel by the pipe c and flows over the partitions, down through the funnels and out through the pipe d. The gas from the kiln enters by the pipe a, the lower end of which is perforated, and flows upwards in the direction indicated by the arrows. In the passage of the gas the dust carried over is deposited and 284 CHAPTER XV the gas cooled down to a temperature of 40°C. Various other forms of gas washers are made ; in one, perforated plates take the place of the transverse partitions described above. Any of the forms of jet condensers described in connection with evaporation serve equally well as gas washers. In certain beet factories the gas evolved from the kiln is purified by being passed through closely packed carbonate of soda or through a solution of this substance ; the object of this procedure is to eliminate any sulphurous acid which may be present, as the coke employed contains sulphur. Lime Kilns.—The carbon dioxide requisite for the carbonation process is obtained by burning lime in kilns at the factory, which in this case makes its own temper lime from crude limestone. Lime kilns are of two types, continuous and intermittent, and the former, of course, is the type required for asugar factory. They may also be classed as long flame and short flame kilns. In the former the fuel is burnt on a hearth, and the products of combustion pass through the limestone in the kiln proper. In the latter the fuel and lime stone are mixed together and charged into the kiln from above. Externally fired kilns give a purer product, since no contamination with the ash of the fuel results. As, however, the ash of gas coke, the fuel usually employed, is in- soluble, this objection has for sugar work little weight. The external-fired kiln finds application when wood or lignite fuel is used. The early form of kiln consisted of a truncated cone, as shown in Fig. 168, of height up to 40 or 50 feet. The limestone and fuel were charged into the kiln from above and, as shown at a, supplementary external furnaces were sometimes provided. The burnt lime was discharged through doors, 8, = arranged around the base of the kiln, Fic. 168 the bottom of the kiln being built sloping downwards and outwards. The gas collected in the chambers, /, whence it passed by pipes g to the pumps. The present form of kiln is known as the Kern or Belgian kiln, and is shown in Fig. 169. It consists of two opposed truncated cones, the upper one being by far the longer. The mouth of the lower cone terminates about two feet from the ground and immediately over a conical surface. The action of the kiln is continuous, burnt lime gravitating on to the hearth, being continuously removed as further charges are dumped into the kiln. The height of the Belgian or other form of kiln varies from a minimum of 30 feet to a maximum of 70 feet. With less height decomposition of the limestone is incomplete, and with a greater one the weight of the column of limestone causes crushing of the lower strata. There is no limit, of course, to the diameter. In American beet sugar houses, continuous rotary gas and oil-fired kilns THE CARBONATION PROCESSES 285 have come into general use. These have developed from the cement kilns, the design of which they closely follow. The kiln consists of a rotary cylinder slightly inclined from the horizontal. The limestone and products of combustion travel in the same direction, the lime being removed at that end of the cylinder remote from the burners. Capacity of Lime Kilns.—Very widely variant capacities are given in standard works. Ware states that the Belgian kiln will readily afford 500 kilos burnt lime per day per cubic metre capacity. This reduces to 1-4 Ibs. per hour per cu. ft. Geerligs, however, referring to practice in Java, gives the capacity as 16 lbs. lime per day per cu. ft., or only 0-66 lbs. per hour per cu. ft. The maximum quantity of lime used in any form of carbonation process is 3 per cent. on cane, or 60 lbs. per ton. Following on which of the above two capa- cities is selected as a basis of design, the cubic contents of a kiln should be either 43 or gi cu. ft. per ton-cane-hour. Four factories in Java, of which the writer has data, had 55, 66, 75 and 108 cu. ft. per ton-cane-hour, or an average of 75 cubic feet. Fuel required in Lime Kilns.—For the decomposition of 100 lbs. of commercial limestone of 95 per cent. purity 6 lbs. of gas coke are required. Generally, in European beet practice g lbs. of coke are required, and under very good control this may be reduced to 7-5 Ibs. Reduced to volume measurements in actual work, from 3 to 4:5 volumes of limestone are used to 1 volume of coke. Action of the Lime Kiln.—In the lime kiln as usually operated, four zones are to be recognised. The upper zone is occupied entirely by the produced gases, and serves sss was 117 Y ) wae A ‘ RO ite ag iff Fi as a regulating zone and reservoir, whence Paki ated A // Y 2 the pump draws. Below this is the heating mamaee UL and drying zone, where water is removed Fic. 169 from the materials, which are also raised to the decomposition temperature. This temperature is of the order 1,000° C., and when the materials in their downward passage reach this temperature the decomposition zone is reached. Here the temperature varies from I,000° C. to 1,300° C., and below it is reached the fourth zone or zone of cooling extending to the lowest part of the kiln. Of these zones, that devoted to cooling occupies about half the total capacity of the kiln, the decomposition zone occupying one quarter, and the heating and regulating zones one-eighth each. In operating a kiln a high percentage of carbon dioxide in the gas is required, together with absence of carbon monoxide, which should not exceed 0-5 per cent. The absolute maximum of carbon dioxide is, with coke Io per cent. on limestone, 38 to 39 per cent., and a percentage of not less than 30 per cent. is considered satis- 286 CHAPTER XV factory. Accompanying this will be up to 2 per cent. of oxygen, the balance being nitrogen. The excess of oxygen is necessary, since in the upward passage of carbon dioxide and water through the incandescent coke some decomposition into carbon monoxide occurs, which has afterwards to be burnt to the dioxide in the upper portion of the kiln. The temperature at which calcium carbonate begins to dissociate is about 400° C., but the reaction is a balanced one, definite positions of equilibrium determined by the temperature and pressure obtaining. Accordingly, temperatures much higher than the dissociation temperature must be maintained, and experience has found that a temperature in the decomposition zone of 1,000°-1,200° C. is economically proper. Higher temperatures are inadvisable, since at about 1,300° C. the carbon dioxide decomposes into carbon monoxide and oxygen, which pass into the gas aspirate from the kiln. A second result of a too high temperature results in the formation of ‘‘ dead’”’ lime, which requires an abnormally long time to slake. This phenomenon is usually attributed to the formation of a skin of fused silica on the lime, but it is more probably due to the formation at high temperatures of an allotropic form of lime, which only slowly passes into the normal form. Choice of Limestone.—The objectionable constituents which occur in limestone are silica, alumina, magnesia and sulphate of lime. If either of the two former is present during the calcination, fusible silicates and alumin- ates of lime and magnesia are formed, giving rise to what is known as scaffold- ing in the kiln—i.e., a fused mass is formed preventing the descent of the lime. In addition, their presence may be a cause of slow slaking of the burnt lime. Silica also may dissolve in the juice and be precipitated both as scale in the evaporators, besides causing filtration difficulties. Magnesia and sulphate of lime are also likely to cause scale in the evaporators. Below are given analyses by Gallois and Dupont of different types of limestone :— Material. . Bad. Passable. Excellent. Moisture aoe “oe 4-10 6°25 1-20 Sand, clay, and insoluble matter 4°50 3°17 0°55 Organic matter I -20 Trove 0-41 Soluble silica ... 2 2-10 0 -64 0 +20 Oxides of iron and alumina 0°37 0°15 0:23 Calcium carbonate (limestone) 85 -86 87 -93 96 +58 Magnesium carbonate 0°95 0-53 0+50_ Soda and potash 0:05 — Ja Undetermined 0 -87 O +24 One The inefficient working of a kiln may arise from the following points :— I. Scaffolding, which may as already mentioned be caused by the presence of silica or alumina, and also by careless work in changing or in mixing the limestone and fuel. 2. Withdrawal of unburnt lime when too little fuel is used or when combustion is too rapid. 3. Presence of carbon monoxide, due to too little air being admitted for complete combustion, or to too low a temperature in the kiln.- 4. Presence of air due to leaks in the masonry or to air sucking back, or to working the pump too fast. The composition of the gas from the kilns varies within wide limits, the THE CARBONATION PROCESSES 287 theoretical maximum of carbon dioxide being 38-7 per cent.; in general practice the percentage lies between 25 and 30 per cent., with from I to 3 per cent. of oxygen and 65 to 70 per cent. of nitrogen. Traces of carbon monoxide may be present, but should not rise above I per cent. ; sulphur dioxide derived from sulphur in the coal may also occur. Carbon Dioxide Pumps.—The pumps used to aspirate the carbon dioxide are now slide-valve pumps similar in design and construction to those used in the dry vacuum process described in the chapter on Evaporation. A table of their capacities is given below, taken from a Continental maker’s catalogue. | Quantity of gas sucked per | | hour, cu.m. : 50 825 | 1050 | 1300 | 1800 2050 | 3375 | 4050 Diameter of steam cy ‘linder, mm. [275 35° | 375 | 400 470 | 500 600 700 Diameter of ‘carbonic acid cylinder, mm. ... ---| 500 550 600 | 650 750 800 | 1000 1100 Piston stroke, mm. Saale gO 550 550 630 700 | 70O 800 | 1000 Revolutions per minute ... 75 70 70 65 60 | 60 55 45 Steam inlet, mm. ... OO 80 80 QO) |) TOC CET O Ae sr40% [ar 70 Steam outlet, mm. : 7O go go 100 120 | I20 150 185 Diameter of suction pipe, mm. .| Io 125 | 135 150 175 | 190 240 270 Diameter of deliv ery pipe, mm. “ eae SOG IIo 125 140 160 | 170 220 250 Differences between Carbonation and Defecation.—In addition to the differences already noted, others, best observed in the following analyses of molasses quoted from Geerligs,® exist. They lie mainly in the greater quan- tity of lime salts, in the very small optical activity of the reducing sugars, and in the smaller quantity of “‘ gums.” + | = = ea . =| his r= $ | 8 a a (a a ON E = S 2 = 5 a am = ° ¥ PS = 3 Ba | 238 Su 5 . a Bs a ae § aks f= ae ss & A Az e | by ere ee oD n d — 5 | P= | i os | ©“Q, Pra = 2 p= | — | cD bi > < ‘(id 8 eae =| Ee Gps onl tea bee | | é@|& n Oo | Oo | = PALE GGA DIOGGE Sass SEER Soe Carbonation BE seth | 37 °1 | 39-8 | 27 -6 | 0-74 | 1-58 Defecation 8-8 | 33:9 33°7 | 42-4 | 23°6 | 1-95 | 0°53 t | } In the reports issued for the Mutual Control of Java factories for the year I912 the following averages can be deduced. Seventeen carbonation factories raised the purity of the raw juice from 82-2 to 84:9, or 2-7 units, whereas 114 defecation factories raised the purity from 80-1 to 82:4, or 2°3 units. A difference so small as this is without significance, and especially so since the purities referred to are on a polarization basis. The relative yields are still in the controversial stage in Java. One of the latest estimates of these, referring solely to a production of white sugar, is that of Van der Went.’ Putting the yield with sulpho-defecation at Ioo, he finds that with double carbonation is 100-32, with de Haan’s method 100-64, and with Bach’s process 100-96. Compared with the yields of 96° test sugar, the results of de Haan in one and the same factory may be CHAPTER “XV quoted. He found that the yield of available sugar (Winter’s formula) was 100°62 with 96° test sugar, as compared with 99:02 when using sulpho- defecation. BV AAEYYN A REFERENCES IN CHAPTER XV. Ou) LOO7)) 275 1220. “ Plantation White Sugar Manufacture,’’ London, 1913. Int. Sug. Jour., 1914, 16, 131, 438. U.S. Patents, 1,044,003; 1,044,004. Sucrérie indigéne et coloniale, 1887, 22, 159. “Cane Sugar and its Manufacture,’’ Manchester, 1909. Java Arch., 1914, 22, 1084. CHAPTER XVI SULPHITATION Tue discharge of the colouring matters of cane juices by acids has been already mentioned, and to this property is due in the main the extended use of sulphurous acid in the manufacture of white and yellow consumption sugars. Sulphurous acid in addition is a reducing agent, and it may have some further action on the colouring matters due to this property ; granted, how- ever, that such an action obtains, the results would be only temporary, the colout being restored on exposure to the air following on oxidation. To such a cycle may be ascribed the darkening which is frequently observed when plantation white sugars are stored for any length of time. Apart from the action of sulphurous acid on the natural colouring matters, it has a specific action on the ferric salts, which find their way into the juices from the pipes and containers. These ferric salts form very dark-coloured compounds with the polyphenols expressed from the cane, and also with the lime-reducing sugar decomposition products, which, according to Schneller,} are akin in structure to the polyphenols. These dark-coloured bodies are nothing else than inks. The ferrous compounds to which they are reduced by sulphurous acid are, however, colourless, and Harloff and Schmidt? distinctly state that these do not crystallize with the sugar, so that in their absence there is no darkening of sugar due to this cause. Sulphurous acid shares with any other acid the power of protecting juices from discoloration on boiling. As already stated, the action of alkalies on reducing sugars results in the form- ation of dark-coloured bodies, and a darkening to this cause is well known to occur between the defecated juice and the syrup in the ordinary defecation process. Such a darkening also occurs in the carbonation process and is here caused by the permanent alkalinity due to the potassium carbonate.* Suspended calcium carbonate due to bad filtration is also sufficient to cause this change. If then the juices coming from the second carbonation, or the first where only one is used, be rendered acid before evaporation they will maintain their light colour and will be especially adapted for the making of white sugars. Such a scheme, using sulphurous acid as the acid, was introduced into Java by Harloff, and is known as the acid thin-juice process. Acid thin-juice processes without carbonation had, however, been used for many years previously in Louisiana, Demerara and Mauritius, although no detailed account of them seems to have been given. The use of sulphurous acid was first suggested by Proust® in 1809, and its application forms the subject of French patent 2543, 1829, granted to Dubrunfaut. The earliest British patent is that of Stolle (7573, 1838), which describes its application much as it is now used. Its introduction is, however, due to Melsens,4 who in 1849 published a paper which had a * In the Battelle process, with complete elimination of the reducing sugars, this discoloration should not occur, 289 x 290 CHAPTER XVI great influence on sugar manufacture. Prior to this time both beet and cane sugar houses specializing in white sugars had employed animal charcoal filtration, and the first efforts to eliminate this agent may be traced to Melsens’ work. In Louisiana the application of sulphitation dates from 1860, where it was used under Stewart’s patent (U.S. 22590, 1859), and at about the same time it was introduced into Mauritius through the agency of Icéry. Sulphitation Processes.—There are a great many ways in which sulphur is used alone and in combination with other agents. Some of these methods are described below. Raw Juice Sulphitation.—In the older schemes, sulphitation was carried out on the raw juice, the lime and sulphurous acid being added separately to the cold juice, practice differing as to which defecant was added first. In either case the same end point was aimed at, namely, a juice with an acidity in terms of phenolphthalein of from 0-5 to 0-7 c.c. normal per I00 C.c¢. When the operation is conducted on cold juice, however, a rather serious trouble arises. Calcium sulphite is more soluble at ordinary than at higher temperatures, and it has also the property of forming supersaturated solutions. Consequently, when a cold limed and sulphured juice is heated, it deposits large quantities of calcium sulphite on the tubes of the heaters, and also upon the tubes of the evaporator. Java practice has developed a routine which satisfactorily eliminates this trouble. The raw juice is heated to a temperature variously quoted as 70° C. to 80° C., over which region the solubility of calcium sulphite is at a minimum. After reception of the hot juice in open vessels, the necessary quantities of milk-of-lime and of sulphur dioxide are added simultaneously. The treated juice now passes through a second heater, where its temperature is raised to 100° C., and thence to the settling or filter supply tanks. In this way is avoided the coloration due to lime- reducing sugar decomposition products following on heating after addition of lime only, or inversion due to heating after addition of sulphur dioxide only. Any deposit of scale which may form on the second heating can be sys- tematically removed by alternating the flow of juice through the first and second heaters. Whatever method is adopted, it seems general to use about twice as much lime as would be used in ordinary lime defecation, so as to obtain a sufficient bulk of calcium sulphite to carry down and entangle the colloids ; at the same time the simultaneous application of lime and sulphur dioxide reduces the quantities that are requisite for a good defecation. The action of sulphur dioxide on cane juice has been examined by Browne.° He shows that due to the action of sulphur alone a precipitate amounting to 0-3 to 0-4 per cent. on the weight of the juice is formed, and the composition of this precipitate he finds as below :— Water 4°07 4°49 Fat and wax 32°57 19°71 Protein one 23 *63 21°75 Ash and earthy matter 9-48 20°45 Crude Fibre 8 +05 10 °37 Gums, etc. ... 22 °20 23°23 SULPHITATION 291 The purification due to the action of sulphur alone, however, does not obtain in practice, since with the addition of lime to neutrality a part of the precipitate dissolves. Acid Waters in the Evaporation.—However carefully the acidity of the juices is controlled, the condensed waters in the multiple effect will be found to be acid, and to contain not only sulphurous but also sulphuric acid. This is an evil which must be accepted, since, if an alkalinity sufficient to prevent it were carried, the benefit of the application of sulphur would be stultified. Hence when such waters are used as boiler feed, they must be carefully neutralized with soda before going to the boilers. The most efficient location to effect this neutralization is in the bodies of the vessels themselves, thereby saving corrosion in the pumps and piping. This end is obtained by allowing carefully regulated quantities of soda solution to flow into the vapour pipes or calandrias. The requisite quantity of soda as carbonate should not exceed one Ib. per 100 tons of cane. Sulpho-carbonation.2—In this process, which is due to Harloff, and which is known as the “ acid thin-juice’”’ process, the complete neutralization of the first carbonated juice is effected by means of sulphurous acid. The saturation may be carried out wholly by this acid or by a combination of this and of carbon dioxide, the acidity finally obtained referred to phenol- phthalein being from 0-6 to 0-8 c.c. normal per 100 c.c. By this means the darkening of the juice on evaporation due to potassium carbonate alkalinity is avoided, and there results a lemon-yellow syrup affording a high-class white sugar. Syrup Sulphitation.7—Syrup sulphitation was introduced into Java by Bach, and his process is in many ways the most rational one by which a plantation white sugar can be made. The syrup as it leaves the evaporator is treated with 2 to 2} per cent. of milk-of-lime at 15° Baumé equivalent to from 0-3 to 0-4 per cent. of dry lime. Immediately after the addition of lime the material is sulphured to neutrality, and the copious precipitate which is formed is filtered off. The clear filtrate is then sulphured to an acidity of from 2 to 3 c.c. normal per Ioo c.c. and boiled to massecuite. Syrup filtration may, of course, be combined with any of the other routines, and is to be recommended as the surest means of giving a material free from suspended matter, upon which the brightness of the sugar largely depends. Apparatus used in Sulphitation.—-In the apparatus employed in sulphuring there are two independent units, the oven and the absorption appliance. The oven is merely a cast-iron chamber into which the sulphur is introduced 292 CHAPTER XVI ona tray. The combustion of the sulphur may take place with free access to the atmosphere, a draught being obtained by a fan or jet of exhaust steam, as in connection with the “sulphur box ”’ described below. Direct access to the atmosphere is, however, to be avoided, since in the presence of water sulphur burns in part to the trioxide, giving rise to sulphuric acid in the juices, the presence of which is objectionable. The air admitted for combustion should therefore be dried by passing through quicklime before it reaches the oven. A very simple and convenient dryer may be made from a piece of iron pipe about six inches in diameter and four feet high, and holding about forty Ibs. of coarse lime. As required, depending on the humidity of the air and the quantity of-sulphur burned, the lime is renewed. The fire area of the stove depends on the draught or on the air pressure when compressed air is employed. With a draught of two to three inches of water two lbs. of sulphur can be burnt per sq. ft. per hour. As the sulphur burns the rise in temperature causes some part to sublime, and this being carried forward SSS PLL TT I APP AP DA TIT TILLER N Sw res ON g NZ. PPLLILLLLT ELLE LT LLL} i—1 D =" ee. SLEareese willfin time cause the pipes to become“choked. The*ovenfshould therefore be provided with a water-cooled dome serving to condense the sublimate, and from which it may be periodically removed. The sulphur furnaces are of such simple construction that they'may‘be readily made on the plantation. For continuity of operation they are conveniently used in pairs. The means for the absorption of the gas may be the sulphur “ box” or tower indicated in Fig. 170. This consists of a wooden vertical shaft, in which are arranged perforated trays e. The juice is delivered to the top of the box by the pipe d, and flowing down meets a stream of gas entering by the pipe c, and travelling upwards under the influence of the draught caused by the steam jet a. In place of perforated trays other arrangements borrowed from the condenser may be used. In place of the tower it is better practice to sulphur the juice or syrup in tanks, and in this case the gas must be pumped to the tank or conveyed thereto by means of an ejector or by compressed air. A diagrammatic scheme of such an arrangement is shown in Fig. 171, where a represents the ovens with water-cooled domes, 6 the air compressor, ¢ towers packed with coke or similar material serving as a filter, d a chamber filled with dry lime, e the sulphitation tanks and f the conducting piping. Another SULPHITATION 293 type of oven which operates satisfactorily is shown in Fig. 172. It consists - of an iron oven with a heavy door, 8, resting on and making a tight joint with a rubber seat and covering the aperture through which the sulphur is period- ically introduced. The draught is obtained by means of the injector e using live steam, and affording sufficient head to force the gas into the tanks. The air enters through the pipe c, which is packed with dry lime. The in- jector may be made of lead alloyed with three per cent. of antimony. An apparatus very widely used in the beet sugar industry is that of Quarez, Fig. 173. The juice runs from the mills through the pipe B into the tank A, divided into two compartments by the plate C reaching nearly to the bottom. From here it is forced by the pump D through the injector E, which communicates by the piping H with the sulphur furnace G,; so that the gas is drawn into the juice, which now travels by the pipe K into the tank, whence it overflows through the pipe M. In this arrangement the quantity of juice passing regulates the rate at which the sulphur is burned. A method of sulphuring which was once largely used in the beet sugar in- dustry is that of Seyferth (patent 2756 of 1870), which drew the gas directly into the vacuum pan during the operation of boiling. This scheme is only exceptionally to be found in the cane industry. Quantity of Sulphur used.—In the © different schemes this will depend on | the quantity of lime used and on the | acidity desired. Starting with a neu- ; tral juice, each Ic.c. of normal acidity per 100 c.c. of juice corresponds to the presence of 0-16 gram sulphur per I,000 c.c., or very closely to 0-016 Fic, 173 sulphur per cent. on cane, when the weight of juice is the same as that of the cane. Actually when using sulphur only on second carbonated juices the consumption is found to be about 0-02 per cent. on cane, in sulpho-defecation processes about 0-04 per cent. on cane, and in Bach’s scheme it rises to 0-1 per cent. on cane. As sulphur burning to SO, requires oxygen equal to the weight of the sulphur, the air required will be 4-5 lbs. Actually due to inefficiency g lbs. air should be allowed in design. The volume of air remaining unchanged during combustion, per lb. of sulphur there will be at the normal temperature 125 c. ft. to be pumped. The maximum volume per cent. of sulphur dioxide in the gas will be 20-8 per cent., and with twice the necessary quantity of air admitted this will fall to 10-4 percent. These data give all the essentials required for design. Hydrosulphites.—The bleaching effect of hydrosulphurous acid was first employed in Ranson’s process,* which passes sulphur dioxide into juices 204 CHAPTER XVI in the presence of tin or of zinc. About 1904 stable hydrosulphites were manufactured, the calcium salt being sold under the name of ‘“ Redos”’ and the sodium salt as ‘‘ Blankit.’”’ These react under the equation, Na,S,0, + O + H,O = 2NaHSO,. In the cane sugar industry they have been chiefly employed in the decolorization of syrups in white sugar manu- facture. As the bleached material colours again on exposure to the air, they are used in the vacuum pan shortly before striking. The quantity required to obtain the maximum effect varies with different juices. With those that the writer has had to deal, it is about one lb. per ton of sugar, though the makers state that considerably less is usually required. The claim that so small a quantity can materially affect the viscosity is unworthy of con- sideration. Phosphoric Acid and Phosphates.—Phosphoric acid is employed as a defecant either as the free acid or as a soluble phosphate. Their action depends on their property of forming a bulky precipitate with lime, which on its formation entangles and carries down colloid matter. This action occurs to a certain extent in lime defecation due to the presence of phosphates in juices. Toobtain the maximum effect the lime and acid should be present in the proportions to form the tri-basic salt. The quantity used is generally about 5 lbs. per 1,000 gallons of juice. Apart from this action, phosphoric acid is a very weak acid, and it hence forms a convenient agent for obtaining an acid reaction when using an acid thin-juice process, and it is this function which is employed in Demerara and in Mauritius. These two effects may of course be combined in the same factory, though not in the same operation. The descriptions extant of the routines adopted in Java in white sugar manufacture do not indicate that phosphoric acid is used there in an acid. thin-juice process, though there would be advantages in doing so, reserving sulphurous acid for the final decolorization of the syrup. Sodium phosphate in the form of the di-basic salt has also been used as a means of removing small traces of iron salts from syrups immediately before boiling to grain. The use of phosphates as a defecant seems to be first mentioned in patent 13634, 1851, granted to Oxland and Oxland, and again in one issued to Col- — lette (1 of 1854). Their introduction into the cane sugar industry is due to Ehrmann in Mauritius about 1860. Alumina.—-Salts of aluminium in the presence of alkalies afford a very bulky precipitate of the hydroxide which at the moment of its formation carries down much colloid and colouring matter. Such a reaction was used in the cane sugar industry at least 150 years ago, and is described in the Marquis of Cazaud’s treatise of date 1770. The property is also included as a claim in Howard’s patent (3754, 1813), and the alumina so prepared was for long known as “‘ Howard’s finings.’’ Proposals for its use in one or another way are still occasionally made. Tannin.—Although tannin (and tannic acid) is one of the bodies most de- sirable to remove from juices, the bulky precipitate that is formed by the action of lime, etc., has led to the idea that plant extracts containing tannin afforded a purification of the cane juices to which they were added. The idea has been put into practice from very early days, and is still employed by the ryots of British India in their domestic processes. Its use forms the subjects of patents issued to Stokes (5555, 1827) and to Watson (7124, 1836). SULPHITATION 205 Baryta.—Although essentially similar to lime in action, baryta preci- pitates sulphates and some other bodies not thrown out by lime, and for this reason its use has been advised. Questions of cost, however, render its use in the quantities required impossible. In white sugar manufacture baryta is, however, sometimes used on syrups where the bulky precipitate formed is believed to carry down iron as ferric hydrate. Ferrocyanide.—Iron present as a ferrous salt may be quantitatively precipitated by potassium ferrocyanide and removed by filtration. If allowed to remain suspended, the white compound formed is oxidized to Prussian blue. This reaction is employed on syrups in white sugar manu- facture, the salt being used in quantities of about I oz. per ton of syrup, which is enough to precipitate the very small quantities of iron present. Potash Removal.—The removal of potash from juices has been attempted in many ways. In chronological order the proposals are :—Kessler, French patent 58613, 1862; Marix, French patent 82562, 1868; Tamin, patent 3151 of 1873 ; Hlavati, 15274 of 1903, precipitation as fluosilicates ; Duncan and Newlands, 2090 of 1871, precipitation as tartrate; Duncan, 1989 of 1874, precipitation as a potash alum; Gill and Gill, 3333 of 1874, precipi- tation as oxalate; Gans, 8232 of 1907, substitution of potash by lime obtained by filtering through an artificial zeolite, with subsequent recovery of the potash by washing. Of these proposals the recovery as an alum was successfully worked for a number of years in a London refinery. Electrical Processes.—Though the passage of a current does afford a coagulation of the colloids, the same effect can be obtained in a better and cheaper way by the action of heat and lime. Various proposals and processes depend for their effect, not on the passage of the current, but on the solution of the heavy metal forming an electrode. Other proposals of this nature have all the appearance of being frauds, and the secrecy attached to them does not invite confidence. Heavy Metals.—Nearly all the heavy metals form bulky precipitates with cane juices. This is especially the case with basic lead salts, the use of which and their subsequent removal as phosphates formed the subject of a patent issued to Gwynne and Young (7231, 1836). Later Scoffern’s proposal (patent I1ggI, 1847) to use lead and eliminate it as sulphite enjoyed a brief period of notoriety. It was used in a London refinery under the supervision of Daniell, and also in Spain and the West Indies. Authority finally inter- vened to stop its use. The use of tin salts was patented by Nash (366 of 1852), and of zinc by Terry and Parker (6442, 1833). The Use of Vegetable Carbons.—About Igio certain preparations consisting essentially of finely divided carbon appeared on the market, the object of their production being the decolorization of sugar materials. Great mystery, extravagant claims, and exorbitant prices were attached to these prepara- tions, which, however, may become of great value to the industry. A certain amount of research work has been done on these materials, and an abstract of the present state of knowledge is appended : Preparation.—A charcoal prepared by carbonizing wood at a low tempera- ture will be found to have little if any adsorptive properties. It may, how- 296 CHAPTER XVI ever, beactivated. This activation may be effected by heating in the presence (but not with active circulation) of air at temperatures variously stated, but probably about 400° C. The heating may also be done in the presence of superheated steam at temperatures up to 800--1,000° C. If the carbonaceous material be impregnated with various materials, lime, the chlorides of zinc, calcium and magnesium, soda, sulphuric acid, and be carbonized at a low temperature, a very active carbon results after the removal of the impreg- nating material by leaching or distillation. Certain materials, such as rice hulls, rich in silica, afford an active carbon after removal of the silica by boiling with caustic soda. The theory of these preparations is thus given by Lamb, Wilson and Chaney.’ Amorphous carbon exists in two forms, called primary and secondary ; primary carbon is formed at lower temperatures, and may be activated. Secondary carbon formed at higher temperatures is graphitic in nature and cannot be activated. When charcoal is obtained as usually burnt, the hydrocarbons tormed in the operation are adsorbed, and an inactive carbon results. Activation consists in removing these hydrocarbons. This removal is effected by heating, and is partly a process of distillation, and partly a process of oxidation. At the same time the charcoal itself is oxidized on the surface of the already existing capillaries, whereby the effective area becomes increased. The art of the process lies in careful control of the tem- perature, which if too low fails to remove the hydrocarbons, and if tco high causes the formation of the secondary or graphitic type of carbon. Possibly also the hydrocarbons may break down at higher temperatures and deposit a laver of inactive material on the surface of the charcoal. All of the im- pregnating materials used are dehydrating agents, and they have the property of rendering as charcoal nearly all the carbon present in the wood or other material. Hydrocarbons are therefore not formed, and on removal of the impregnating material an active charcoal results. A secondary action may be that they penetrate into the material and on removal add to the surface area. Their influence may also be catalytic. Our present knowledge of the action of these bodies on sugar materials is mainly due to Schneller,§ Zerban® and Bradley.19 The very detailed experiments of the last named are given in abstract below. All experiments were made with “ Norit”’ on solutions of Barbados or Mozambique raws. Five per cent. on dry weight was used on 50 per cent. sugar solutions, unless otherwise indicated. Effect of Size of Particles—Norit was fractionated according to size of particles by bolting through, silk sieves. Percentage of Percentage of Relative Mesh per material colour | speed of lineal inch. retained on removed. filtration. sieve. 20 0°45 Muddy —- 28 o-41 Do. 72 38 0°45 29 °1 mae 48 4°64 415 34 60 7 +30 65:0 28 72 12 -80 76 -2 18 84 FOX 80-0 — 94 6 -96 80-0 7 106 6 -43 81-0 4°5 124 46-0 81 -6 4°5 Original — 71 °8 6 ae. ee ee SULPHITATION 297 Effect of Quantity. Per cent. Per cent. Per cent. / Per cent. of colour of colour Norit. removed. Norit. removed. 0°5 / 36°5 ) 4°0 85-5 I-o 62 °5 4°5 86 -o 1-5 . 7O-o 5-0 86 -2 2-0 75°4 ' 5S 87-0 2°5 79-0 6-0 87-0 3-0 82-7 6°5 87-8 3°5 84-5 7-0 | 88 -o The filtrate became bright with 3-o per cent. of Norit. Effect of Temperature. Per cent. Per cent. Temp. C.° | colour Temp. C.° | colour removed. removed. 20 54-6 7O 7O -I 30 60 -8 80 qi -I 40 ‘| 64°5 90 qi -6 50 67 -2 100 71-9 60 ! 69 -7 Effect of Duration of Contact. } Time, | Per cent. Time, Per cent. mins. colour mins. colour removed. | removed. o 78 <2 35 81-o 5 78 “4 40 8I +7 = 78-9 ! 45 81-9 15 79-4 50 | 82 +3 20 80-0 55 | 82-9 25 80°5 60 83-5 L 7 Effect of Reaction. Acidity c.c. normal. Acidity c.c. normal. H,SO, Per cent. HeSO, Per cent. per colour per P colour 100 C.c. removed. 100 C.c. removed. o 76-2 | 0 +25 83-4 0-025 ' 771 0 +30 84-8 0-05 78 -o O-4 87-1 0-10 79°4 0°50 89 -6 0°15 80 -8 0°75 2-6 0 +20 82-1 I -oo Q5°0 298 CGHAPTER. XVI The influence of the particular acid used to obtain acidity was found to be negligible. The indicator used in this experiment is not specified. Zerban!! has, too, recently operated on large-scale experiments with Norit in combination with kieselguhr, and in the absence of lime treatment. He obtained normal working, and observed very great adsorption of pectins (alcoholic precipitate) and very small adsorption of ash. These vegetable carbons are recommended for use in quantity greater than necessary for decolorization, the material being used repeatedly until ineffective, when revivification is necessary. The quantity stated to be used is 5 per cent. on dry substance, used ten times in succession. Partial revivification is effected by washing with sodium carbonate, but eventually a heat treatment is required. ae These carbons have not yet come into standard practice. They have been used to some extent in refineries in Scotland, Holland and Portugal, by © some confectioners on a minor scale, and in isolated cases in raw sugar houses in Java and Mozambique and Louisiana. A material due to Peck and Lyon, and prepared by the action of sulphuric acid on molasses absorbed by kieselguhr, is also in use in at least one house in Hawaii. Other Agents.—In addition to those already quoted may be mentioned hypochlorites, chlorine, ozone. Von Lippmann!* has made a complete collation of all the proposals which may most conveniently be read in the fifth edition of Spencer’s ‘‘ Handbook for Cane Sugar Manufacturers.” Other than those mentioned above, none is of importance. REFERENCES: IN CHAPTER XVI. La. Ex. Sta., Bull. 157. “Practical White Sugar Manufacture,’’ London, 1915. Jour. de Phys., 1810, 71, 455. Ann. Chim. Phys., 1849, 27, 273- gee Sta ull tr S.C., 1897, 29, 346. Jour. Ind. Eng. Chem., 1919, 11, 157. Int. Sug. Jour., 1918, 20, 191. Int. Sug. Jour., 1918, 20, 309. Jour. Soc. Chem. Ind., 1919, 38, 396 T. ea. Bull.) 173° 4 HW OH bo fH © Deut. Zuckerind., 1909, 34, 9- CHAPTER XVII FILTRATION THE importance of filtration in a raw sugar factory depends on the class of sugarmade. Wheng6° test crystals form the output, filtration is usually confined to the scums formed on defecation, and it is only exceptionally that the juices themselves are filtered. When, however, white sugars are made by acombined defecation and sulphitation process, filtration is of importance since the appearance of the sugar largely determines its market value, and bright sugars can only be made from a transparent juice free from suspended matter ; in fact, this feature is of equal importance with the colour of the syrups. In the carbonation process, also, filtration becomes of importance because of the very large quantity of material that has to be filtered. Routines followed in Defecation Processes.—The heated and limed juice is allowed to settle in tanks, whence the clear juice is decanted, leaving from Io to 15 per cent. of the whole volume of the juice asa mud. The mud may be :— (a) Pumped direct to the presses, where it may or may not be washed. (6) The mud is run to resettling tanks, diluted with water, blown up with live steam and sent to the presses. (c) The method in 6 may be systematized so as to economize water by using the filtrate from the presses to dilute the original mud, which, after blowing up, is allowed to settle. The clear dilute juice drawn off is sent to the evaporators, the mud being then diluted with water, blown up and sent to the presses. (d@) When the mud is washed in the presses the dilute juice may be economically used to dilute the original mud. (e) After one pressing the mud may be dropped from the presses unwashed, pugged in a mixer with water, and pressed a second time. As in the other routines, economy may be effected by using the second filtrate to dilute the original mud. (f) In combination with any of the above schemes the decanted juice may be filtered through leaf filters, through sand, “ excelsior,’’ bagasse or other similar material. (g) The whole juice may be filtered ex masse through plate and frame presses. Of all these schemes decantation combined with scum filtration in plate and frame presses with washing in the press combined with the systematized use of the dilute washings is to be preferred. With certain juices washing of the scums is a very slow process, and in such cases double filtration is preferable. The filtration of the juice in bulk can only be satisfactorily performed 299 300 CHAPTER XVII with juices of high purity, and even then it is probable that more lime than necessary to effect defecation must be used. Filtration of the clear decanted juice is supererogatory when making g6° test sugars since the small amount of suspended matter present in well defecated juice is immaterial with this type of sugar. Routines followed in Carbonation Processes.—No choice exists here. The whole mass of the juice is filtered in plate and frame presses after both first and second carbonation. The filtration is followed by washing as these materials offer no obstacle thereto. ' Routines followed in Sulphitation Processes.—Any of the schemes men- tioned under defecation may be followed. As brightness is now of value, the filtration of the decanted juice occupies a position of importance. In place of this operation it is, however, more common and rational to filter the syrup after it leaves the evaporator and to thus remove also in one operation the material separated on concentration. Treatment of Scums before Filtration.—The rate of filtration of scums is much greater when they are limed to distinct alkalinity as indicated by phenolphthalein than when they are neutral. Also the rate is increased when the scums are actually boiled for a very short time, and both these treatments are common. The admixture of the very alkaline filtrate with the bulk of neutral juice is, however, not advisable. Means to eliminate this trouble and yet to employ a distinct alkalinity are indicated in the chapter on Defeeation. A third treatment which is used to a certain extent is the admixture of kieselguhr or diatomaceous earth with the scums. Although the advantageous action of this material is easily demonstrable, it is not extensively used in the cane sugar industry, the effects not being commensu- rate with the expense of obtaining the material, except in special cases. Filtering Media.—In nearly every case the medium through which filtration takes place is a stout, closely woven cotton cloth. This material is used to form the filtering surface in bag filters, leaf filters and in presses. Very lately, however, a woven metallic cloth has been put into use. Other materials that are employed in special forms of filters are coke, gravel, sand, sawdust, wood shavings and bagasse. All of these materials can, however, only be used to remove a very small quantity of suspended matter from juices that are very nearly clear. Principles involved in Filtration.—-The variables to be considered in filtra- tion are the pressure under which filtration occurs, the thickness of the cake through which the filtrate has to pass, the viscosity of the liquid and the size of the solid particles. When the last two factors were constant Almy and Lewis! found that with the pressure also constant R = a where R is the rate of flow, V is the volume of the filtrate, and K is a constant ; evidently at any moment V is proportional to the thickness of the cake. With pressure varying they found that the relation R = AT held. They point out that filtration may be considered as a flow through a yt capillary tube, the equation for which is C = ie where ¢ is the radius f FILTRATION 301 of the tube, P is the pressure, / is the length of the tube, and » is the viscosity.* In their experiments the exponent of P was found to be less than unity, and they explain this as due to a closer packing of the solid particles with increase of pressure. They also showed that the rate of flow is also proportional te the viscosity precisely as happens in a capillary tube. In the experiments quoted above the material used was chromic hydrate precipitated by glucose, and, although there do not appear to be any experi- ments on record dealing with cane juice precipitates, there is no reason to believe that similar expressions will not hold. Nothing can be said of the value of the exponents except that from mill to mill the variation will be large. The viscosity of all sugar products decreases very rapidly with rise in temperature, and hence all filtrations should be carried out at as high a temperature as is possible. This is especially the case with syrups. The following rates of filtration were observed by Brendel? with beet syrups. Temperature C°. Flow per minute. Temperature C°. Flow per minute. 2 3 eve 3°1 40 “ce 66 +8 8 a3 9°7 ey. 5) gI -2 21 Be 22-0 60 Se 146 °8 $0 *-- 31-3 Development of the Practice of Filtration.—Filtration as an art may be said to have been established by the invention of the stocking or bag filter by Cleland (patent 4949, 1824). This was improved by Taylor a few years later, and his name is connected therewith to the exclusion of that of the original inventor. The filter-press was originally invented as a means of simultaneously pressing and filtering oil seeds and is contained in Needham’s patent (1669 of 1853). This was developed into a chamber press, with special reference to sugar juices by Needham and Kite (patent 1288 of 1856), and by Needham, Kite and Finzel (patent 1083 of 1856). Its functions and applica- bility were greatly improved by Jacquier and Danék, whose patent (2I01 of 1864) introduces the continuous internal conduit, the plate and frame arrangement and washing out through the cake. A second important patent is that of Dehne (1957 of 1878), which shows separate conduits for juice and for water and locates them in lugs cast at the angles of the plates. This patent shows a plate chamber press. The leaf-filter is due to an American refiner, Lovering, before 1845. These filters are commonly called “ Danéks,” the type having been patented by Danék (15322 of 1887). From this time their use became general. A patent (376 of 1878) issued to Danchell hardly differs, however, from that granted to Danék nine years later. The use of materials, such as sand, coke, etc., is claimed in a patent (9574, 1842), issued to Crossley and Stevens, and these materials figure in a number of subsequent patents. The use of sand in the European beet sugar industry is generally credited to Mayer, who introduced it about 1878. The later patents, of which those issued to Kostalek (9331, of 1902) and to Abraham (27629 of 1902), Fig. 181, are examples, deal with special forms of filters only. The use of kieselguhr or diatomaceous earth is claimed in a patent issued to Heddle, Glen and Stewart (3116 of 1886), and in the same year Wiechmann * This equation is further discussed in the chapter on Centri ugals 302 CHAPTER XVII was granted a patent in America (343287). Soxhlet, to whom the credit for the introduction of this material is generally given, took out a patent much later (21217 of 1892). Casamajor’s proposal to use sawdust is contained in patent 257 of 1883. Filtration through fine wire gauze is claimed in a patent (11312, 1846), and again much later by Robertson and Watson (patent 974 of 1873). Filtration under centrifugal force through flannel is claimed in Bessemer’s patent (13202, 1850). ¢ The Bag or Stocking Filter—The bag filter of Cleland (patent 4949, 1824), usually known as the Taylor filter, consists of a sheath of strong woven material, one end of which is closed by tying. The other end is secured to the wide end of a hollow metal cone. Inside the sheath may be placed a second wide bag turned upon itself several times, and which forms the filtering material, the outer sheath in this case merely serving to support the inner one. This method is described in Schroeder’s patent (8675, 1840). The narrow ends of the cones are secured in a horizontal frame, the whole system of frame and bags being contained in a rectangular iron casing. The usual length of the bags is six feet. The sides of the chamber project ¥ w Jf @ w, J; 4 Fic. 174 Fic. 175 Fic. 176 above the frame on which the bags are carried and thus form a reservoir, into whichis run the material to be filtered. Generally filtration takes place under gravity only, but pressure types have been used, the pressure being obtained either by forming a vacuum in the chamber or by causing an air pressure on the surface of the liquid. The bag filter survives only occasionally in the cane sugai’ industry. The Chamber Press.—The chamber press is found in two forms, the plate and frame press, and the plate press. The form described below is an angle feed washout plate and frame press. Fig. 175 shows an elevation of the frame. It is formed of a skeleton of square shape, and is up to 14 inches in thickness. The thickness of the frame determines the thickness of the cake of material, and this is in turn determined by the nature of the preci- pitate to be filtered off. At horizontally opposite corners are arranged the lugs or ears, in which are formed transverse openings 7 and w, the upper one of which communicates by a channel, a, with the space bounded by the inner surfaces of the frame. Fug. 174 is an elevation of one of the two kinds of plates called the juice plate. It is a casting of over-all dimensions corres- ponding to those of the frame and with transverse openings 7 and w registering with those of the frame; neither of these openings communicates with the interior of the press. The other plate, Fig. 176, is called the water plate, FILTRATION 303 and is similar to the juice plate except that the transverse openings w com- municate by a channel, 5, with the interior of the press. Between the plates and the frames are stretched the filter-cloths; and both sides of the plates are ribbed or channelled or formed with a system of pyramids on their surface, to afford rapid drainage of the liquid that passes through the cloths. On both juice and water plates are located cocks communicating with the interior of the press by the channels c. The stems of these cocks may be of unequal height, so that one cock may be closed while the adjacent ones are open, or the flap closure shown in Figs. 174 and176 may beused. The assembled press is shown in Fig. 177, piping connections being omitted. The press is set up in the order: filter head, frame, juice plate, frame, water plate, frame, juice plate, etc. The frames are indicated by two dots, the juice plates by three dots, and the water plates by one dot. Dirty juice is admitted under pressure to the openings 7 (see Figs. 174, 175 and 176), and passes into the frames by the channels a. The cloths catch the suspended matter, and the clear filtrate which passes through the cloth runs out by the channels c and the cocks e into the gutter f, Fig. 177. SSS TS me a s ! z AMnBnHnak BAe 3a: { 4G ASSL SPSS ER DER ACES eee stat SSS SST CST ¢ AwMn , , 14 ; SSS55 z A i A i BAHAE 4448 & Vanes: CYeecyrer es NWS SS © FIG. 177 When the frames are filled with the intercepted matter washing begins. Water is admitted to the conduit formed by the transverse openings w, and at the same time the cocks on the water plates are closed. In order to escape, the water has to pass through the wall of cake and out through the cock on the juice plate. The plates are pressed together by means of the gear h, and in some designs hydraulic closure is used. Rubber rings inserted in the transverse openings make a tight joint, and these may be replaced by cloth pockets, in which are cut holes registering with the openings in the lugs. The gutter which receives the juice should be provided with three exits, one each for dirty juice, clear juice and washings. In the plate chamber press the chamber is formed in the space confined by the juxtaposition of two plates. The plates are made with thickened edges, the thickness of the edge determining the thickness of the cake. The form peculiarly associated with the Dehne press is shown in Figs. 178 and 180, which represent respectively the water plate and the juice plate. Fig. 179 shows six plates as assembled in a press, the odd-numbered plates being the water plates. The dirty juice conduit is central to the plates, 304 CHAPTER XVII the cloths being locked to the plates by a male and female screw combination passing through the central hole. The water conduit is shown at w, and the washing exit at a, in an upper corner of the plate. In this type cocks are not provided for the escape of the dilute juice from each alternate plate, but the conduit formed by the transverse openings is controlled at one end by a valve discharging into a gutter. At } are openings similarly controlled, which admit of the escape of the air. The assembled press is arranged — similarly to the plate and frame press, the method of washing being the same. The Leaf Filter.—The Philippe type of leaf filter is indicated in perspective in Plate XXV. It consists essentially of a rectangular box with double inclined bottom. Arranged near the top of the box is a horizontal frame, in which are supported a number, usually about twenty to thirty, rectangular wire or pressed steel frames or baskets. These frames are covered with cloth pockets, which make a tight joint with the horizontal frame. The cover of the box is a hinged lid, which carries a number of cocks, one for each basket. The lid on closing makes a tight joint with each filtering element. Dirty juice admitted to the box by the pipe passes to the interior of the baskets, the solid matter being caught on the cloths. When filtration ceases the dirty liquor remaining in the box can be discharged by a cock TT Ah he oH AATF |) i Fie. 178 FIG. 179 Fic. 180 These presses are made in a great variety of shapes. Instead of being rectangular the elements in some designs are cylinders, and many variations are possible without altering the principle. By European makers the frames are regularly made 0-7 metre square, thus giving a filtering area of nearly one square metre per element. They are operated under a head of liquid up to eight feet. Kelly Press.—The Kelly press, Plate XXV (U.S. patent 864308, 1907) is a leaf filter designed for the pressure filtration of scums. It consists of a cylinder mounted on an inclined frame. The filtering elements are made up of wire frames covered with cloth, and are usually spaced four inches apart; they are supported on a travelling carriage mounted on wheels. Each element has an individual outlet. Washing of the cloths and discharge of the cake is effected after running the whole filtering system down the runway. The cloths are washed by the impact of a jet of water. But one joint is ever required to be made. This press is very largely used in the American beet sugar industry. Sweetland Press.—The Sweetland press, Plate XXVI (U.S. patents 885398 and 887285, 1908), is another type of leaf filter. Its peculiarity lies in the “‘ clam shell ”’ arrangement, whereby the press is opened, allowing PLATE XXV. THE PHILIPPE FILTER. THE SWEETLAND LEAF FILTER PLATE XXAVI. FILTER PRESS. THE KELLY FILTRATION 305 the cakes to be discharged and the cloths to be washed. As in the Kelly press, only one joint is to be made. The filtering elements are formed of wire frames covered with cloth. It also is widely used in American beet sugar practice. The advantages of the two presses lie in their labour-saving opportunities. They do not add any new principle to the art of filtration. Sand Filters.—Of the various types of sand filter, that due to Abraham (patent 27629 of 1902), shown in Fig. 181, has been most used in the cane sugar industry. The filtering elements consist of a number of conical iron rings, a, piled vertically on one another and concentric with an upright vertical cylinder, 6. The sand fills the spaces between the rings and around the cylinder. The material to be filtered enters at c, passes through the sand and is withdrawn at d. Thesand when foul is discharged through a door and washed in running water, which carries off the in- tercepted matter. Bagasse Filters.—-A bagasse filter usually consists of a vertical cylinder, through which the juice flows from below upwards. The bagasse used is generally that from the second mill, that from the others being either too coarse or too fine. Bagasse filters have the advantage of eliminating washing, since the bagasse when foul is merely thrown on to the bagasse carrier of the mill and crushed with the rest of the material. Wire Gauze Filters.—The appliance usually used consists of a cylindrical rotating screen, set about Io degrees from the horizontal. The juice is introduced at the higher end and escapes through the perforations. The fine suspended matter is caught and carried for- ward by the rotation of the cylinder. The gauze used contains about 10,000 perfora- tions per square inch, each being about 0-005 inch in diameter. rita Manipulation of Filter-Presses.—Filter-presses for scums and first car- bonated juices are usually worked at a pressure of about 40 lbs. per sq. in., the pressure being obtained from a montjus or pump. The montjus, Fig. 182, which is a French invention introduced in 1819, consists of a cylindrical vertical or horizontal tank, a. It is filled with the material to be filtered through the funnel, b, and steam or compressed air passing through the valve c is allowed to act on the surface of the liquid, causing the material to ascend through the pipe d. The pumps employed may be plunger or centrifugal pumps. The former are often fitted with an appliance whereby the steam is throttled when the pressure exceeds a certain limit. A very convenient arrangement is as follows. The dirty juice is delivered from one centrifugal pump to a tank, in which is maintained a pressure of 20 lbs. per sq. in. The presses are filled from this tank. A second pump draws from this tank, Y 306 CHAPTER XVII and, when the rate of filtration slows down, completes the filling at a pressure of 40 Ibs. per sq. in. The washing is effected by a third centrifugal pump at a pressure of 60 lbs. per sq. in. In filtering decanted juices and second carbonation juices and syrups through either a leaf filter or a chamber press, it is not usual to employ a pump. Better results are obtained when the filtration takes place under a head of about ten feet. In order to preserve the expensive heavy cloth, beet sugar practice places over this a very thin inexpensive cloth, which may be frequently renewed at a net saving in expenditure. Sx ces = yh am 3 Capacity of Filters.—There is so much variation in the rate at which cane products filter, and so much variation in the demands made by different houses on this station that it is impossible to give anything more than a very rough statement, which is referred to a weight of juice equal to that of the cane. Defecation.—With juice equal to cane, scums Io per cent. on the volume of the juice and dry matter in the scums 0-3 to 0-4 per cent. on cane, a filtering area of 65 sq. ft. per ton-cane-hour will be sufficient, provided no washing is required. This figure is to be considered a minimum, and 80 sq. ft. per ton-cane-hour would be a better allowance. When washing of the cake is required, from 100 to 120 sq. ft. per ton-cane-hour should be allowed. The same figure will serve when double pressing is followed, since the second pressing is much more rapid than the first. When the whole volume of the FILTRATION 307 juice is to be filtered en masse, about 150 sq. ft. per ton-cane-hour is required, with proportionate increase if washing is to be followed. Carbonation.—For first carbonated juice there will be required from 100 to 120 sq. ft. per ton- cane-hour, and for the second from 40 to 50 sq. ft., whether in this case leaf presses Or plate and frame presses are used. These quantities seem very small when the greatly increased bulk of the solid matter compared with that obtained in defecation is considered, but the filtration is so much more rapid that the increase is not proportionate thereto. With De Haan’s scheme the area required on first filtration falls to 80 sq. ft. per ton-cane-hour. Leaf Filters—When used on well settled cane juice in a defecation process, from 30 to 40 sq. ft. per ton-cane-hour. Syrup Filtration—In both leaf and plate and frame presses there are required from 30 to 4o sq. ft. per ton-cane-hour. Bagasse Filters.—There will be required a volume of about Io cu. ft. per ton-cane-hour. Loss of Sugar in Press Cake.—The weight of the press cake usually lies between I-25 and 1-75 on Ioo cane. Of this about 25 per cent. is insoluble and 75 per cent. is water and soluble. With juice Ioo per cent. on cane, unwashed cake and undiluted scums, the loss will be from I to 1-5 per cent. of the sugar in the juice. In most Hawaiian factories this loss is reduced to less than 0-25 per cent. by dilution washing or double pressing. In Java, Cuba and other districts a much higher loss is common. In factories follow- ing the carbonation process where the weight of the cake is much greater, washing is essential to prevent a very notable loss. Composition of Press Cake.—Press cake consists of the suspended mechani- cal impurities, 7.e., cane fibre, sand, soil, etc., the coagulated colloids, including cane wax and albuminoids, and phosphate of lime, as well as other bodies. The percentage composition will vary greatly, and will be connected with the milling practice, with the perforations in the mill strainers, with the variety of the cane, and with the degree of exhaustion of thecake. Referred to dry insoluble matter, or to the cake proper, ae proportions will lie within the following limits soil, I0-15 per cent. ; cane wax, 20-30 per cent. ; albuminoids, 10-15 per “cent. ; calcium phosphate, 10-15 per cent. Well pressed cake, firm and dry to the touch, contains from 60 to 70 per cent. of water, while the sugar in the cake will vary from 12 to 1 per cent., dependent on the composition of the juice and the degree of ex- haustion followed. REFERENCES IN CHAPTER XVII. Jour. Ind. Eng. Chem., 1912, 4, 528. “Beet Sugar Manufacture,’ New York, 1905. U.S. Senatorial Document, No. 50, 1845. WO nh CHAPTER XVIII EVAPORATION AFTER the processes of defecation and filtration have been completed, there results a more or less clear juice, varying in quantity from 80 to 120 per cent. of the weight of the cane. This juice contains from 13 to 20 per cent. solid matter, of which 70 to go per cent. is cane sugar. In order to obtain the sugar as crystals the greater part of the water has to be removed. Its removal is effected in two stages: the first is referred to as evaporation, the second as boiling or graining. There is, however, no fundamental reason why these stages should not be continuous; their discontinuity is due to the nature of the operations involved. In the first stage the concentration is carried on until the percentage of solids has reached not less than 50 per cent., and it may reach 70 per cent. ; the variation depends on the capacity of the evaporators, the caprice of the superintendent, and the purity of the juice. The process is conducted under a system of multiple effect evaporation, whereby one unit of steam may evaporate ” units of water, where m may be very great. The extreme limit in practice is reached with an eight-fold evaporation; the apparatus in common use are of triple, quadruple, or quintuple effect. | The evaporator may be operated as an independent unit, or it may be worked in combination with the juice heaters or the graining pans. The first-named combination will be referred to as an isolated system, and the second as a connected system. In this chapter an attempt is made to bring together an account of the elementary principles involved, of the chief types of apparatus used (together with their essential] accessories), of the different systems and combinations, with their bearing on the general economy of the factory as a whole. Boiling Points.—All liquids continually give off to the surrounding atmosphere a part of their substance in the form of vapour, which exerts a definite pressure known as the vapour pressure. For every temperature there is a corresponding vapour pressure, which increases with the tem- perature. When this pressure becomes equal to the pressure of the surround- ing atmosphere, vapour is given off freely from all points of the liquid, and the latter is said to boil, the temperature at which this occurs being called the boiling point at that particular pressure. When no qualification is applied to the boiling point, the pressure is taken to be the normal atmospheric pressure ; this is 14-707 lbs. per sq. in.; 1-034 kilos per sq. cm., or that exerted by a column of mercury 29-92 ins. or 76-0 cm. high.. It is common practice to refer to pressures less than atmospheric in terms of vacuum ; thus an absolute vacuum would be referred to as 29:92 inches of vacuum, and a liquid boiling under a vacuum of 25 inches boils under a pressure of 308 EVAPORATION 309 4-92 inches of mercury, or 2-42 lbs. per sq. in., provided that the atmospheric pressure is 29-92 ins. Conversely, when ebullition occurs at pressures above atmospheric the liquid is said to boil under pressure, such pressures being usually reckoned from the normal atmospheric pressure as zero. Thus, steam at 30 lbs. pressure or 30 lbs. gauge means that the pressure is 30 lbs. per sq. in. above that, due to the atmosphere, corresponding to an absolute pressure of 44-707 lbs. per sq. in. At the end of this chapter will be found a table connecting the boiling points of water with the pressure under which ebullition occurs. The boiling point of a solvent is elevated by the presence of solids in solution. For non-electrolytes, as sugar, and in dilute solutions generally the elevation is proportional to the quantity of material in solution in unit volume, and molecular weights of different non-electrolytes give the same elevation of the boiling point. This elevation of the boiling point is inde- pendent of the pressure under which ebullition occurs. In the annexed table the values from Io to 70 per cent. are due to Gerlach, the balance being after Claassen.* TABLE GIVING THE BOILING POINT OF SUGAR SOLUTIONS. Per cent. Boiling Pen cent. | Boiling Percent Boiling Sugar point Sugar point Sugar point in elevation, in elevation, in elevation, solution. - solution. | BS: solution. Be. 10 0-7 JESS eee 87 “75 33 °9 20 ET 81 -o 19°9 88 -o 34 °6 30 Bite, 81 +5 20 °5 88 +25 35°3 40 72a | 82-0 27 <2 88 -50 36-0 50 3°6 82°5 22-0 88 -75 3Gicy 60 5°4 83-0 22°7 89 -o SPS 7° Sr | 83 °5 | 23-6 89 +25 38-3 75 13-2 84-0 24°7 89 +50 39°1 7305 13°7 84-5 | 25-7 89-75 399 76 14-2 85-0 26 -8 go -0 40°7 76-5 14 °8 teas Ma Uy oe?) 90 +25 41-5 a7 15°3 86-0 29 °2 gO +50 2-4 77-5 15 °8 86°25 | 29°8 90 *75 43 °2 78 16-4 86 °5 30 +4 gI -O 44 °I 78 °5 16-9 86-75 | Ere QI -25 4571 79 sy Aa eg esc Bak 8 erkiage ea QI +50 46 +3 79°5 18 -o ee 32 °5 QI °75 47 °7 80 18 -6 87 +50 33 °2 92-0 50-2 Ii the vapour from a liquid be mixed with the vapour from a second liquid, or with an imcondensible gas, the pressure exerted is the sum of the individual pressures. Thus, if the pressure of water vapour in an enclosed space is found to be higher than that which corresponds to the temperature, the presence of air or other gas is indicated. * The boiling points of sugar solutions were first given by Dutrone in 17g0, and were determined by him as a guide to the operation of sugar boiling in the open train. Generally, the conduct of sugar boiling has not yet reached this degree of refinement. 310 CHAPTER XVIII A vapour, like any other body, may be heated, and a vapour heated above the temperature corresponding to its condensation point at that pressure is said to be superheated, or to have so many degrees of superheat. The condensation point of the vapour and boiling point of the liquid are, of course, the same. Heat.—Heat is a definite measurable form of energy. The unit used in British and British-derived engineering practice is the British Thermal Unit (B.T.U.) : this is the quantity of heat required to raise 1 lb. of water through 1° F. at a temperature of 62° F.* The metric unit is the calorie, based on the kilogram and degree Centigrade ; it is hence 3-967 times as great as the B.T.U. Under this definition, to raise the temperature of water from 32° F. to 212° F. will require 180 B.T.U.; under atmospheric pressure water at this temperature will boil. To convert all the water to steam will require 969-7 B.T.U., and this quantity is said to be the latent heat of steam at 212° F. The sum of the latent heat of steam, and the quantity required to raise the temperature from 32° F. to 212° F. is called the total heat of steam. The latent heat of steam is not constant, but decreases with rise in tem- perature ; ‘the total heat of steam, however, shows an increase with temperature. The quantity of heat in the same weight of different bodies at the same temperature is not the same. The ratio of the quantity of heat required to raise the temperature of a body 1° F., to the quantity of heat required to raise the temperature of the same weight of water 1° F., is called the specific heat, the value assigned to water being unity. The specific heat of a mixture is. as computed arithmetically ; thus the specific heat of a Io per cent. solution of cane sugar is 0-9 X I + 0°I X 0°30I = 0-930I. The Transference of Heat.—In a certain sense a sugar factory may be considered as a system for the transfer of heat, not only in evaporation, but also in the following departments :—Generation of steam in the boilers, heating and evaporation of juices and syrups, cooling of juices on settling, cooling of injection water, cooling of massecuites, drying of sugars. The subject of heat transference will therefore be discussed in. some detail. Heat may be transferred from a hot body to a colder body by conduction, radiation, or convection. By the last term is meant the currents set up in a fluid, when one portion changes in density owing to change in temperature ; an intimate mixture follows, so that transference by convection is merely a special case of conduction. These means may act independently or in conjunction, some specialized examples being given below :—1. The hot body is separated from the cold body by a partition (boilers, juice heaters, and evaporators generally). 2. The hot body is in direct contact with the cold body (injection water in condenser, cooling tower). 3. The transfer takes place solely by conduction (surface condensers, water-jacketed crystal- lizers). 4. Transfer takes place by combined conduction and radiation (steam boiler, loss of heat in steam pipes). 5. The hot body is a gas (steam boiler), a liquid (massecuite), a condensing vapour (steam in evaporator) ; and conversely the cold body is a gas (air and steam pipes), or a liquid (juice in evaporator). 6. The hot and cold bodies may mutually change * The variation referred to any other temperature is very small, and for engineering practice may be neglected. EVAPORATION 311 in temperature (water-jacketed crystallizer), one may change (the hot body in a steam boiler and the cold body in a juice heater), or both may remain at uniform temperaturé (condensing vapour and boiling liquid in evaporators and vacuum pans). The passage of heat by conduction through a partition is controlled by the tollowing circumstances :— 1. The mean temperature difference between the hot and the cold body. If the hot and cold bodies do not change in temperature, as with condensing steam and boiling liquid, the mean temperature difference offers no difficulty in definition ; if, however, one or both temperatures vary, as with a hot liquid and a cold liquid, the mean temperature difference is given by the expression Gi abe ae y ae > (to, a ) min. where T,,,.,, and T,,,,, are the greatest and the least temperature differences (log. = 2°3025 logo). 2. The resistance to the passage of heat from the hot body to the partition, through the partition, and from the partition to the cold body. 3. The rapidity of movement (or circulation) of the hot and cold bodies. 4. The area of the partition. The influence of these factors is discussed below. According to experimental observations, when the temperature differ- ences are small and near to each other on the thermometric scale, and when the physical properties of the bodies on either side of the partition do not vary much with change of temperature, the rate of heat transfer is very nearly proportional to the temperature difference. Thus with a range of temperature, say from 200° F. to 220° F., with condensing steam on one side and juice of 15° Brix on the other, about twice as much heat will pass with steam at 218° F. and juice at 208° F. as with steam at 220° F. and juice at 215° F.; but it does not follow that proportionality will obtain as between one system at 230° F. and another at 150° F., or when the tempera- ture differences to be compared differ greatly in magnitude. It is, however, certain that as the position of the temperature difference rises in the absolute scale of temperature the rate of transfer also increases. This is very marked as between the first and last cells of a multiple effect evaporator, and is also in this case probably due to causes such as viscosity of the syrup, as well as to position in the scale. ’ The writer examined this point as regards the first and last cells of a vertical submerged tube quadruple effect apparatus, taking as the tempera- ture differences the value C, — J, or C; — C, and C, — VS,*; the rate of heat transference was obtained by observing the time required to fill a tank with the water discharged from the first cell. If the rate of heat transference is proportional to the temperature difference, then T (C, — C,) = constant, where TJ is the time taken to fill the tank. Some results follow below, the temperature being in F.° and time in seconds. These experiments were made in a factory and not in an engineering laboratory. * For the significance of these expressions see p. 32I- 312 CHAPTER XVIII RATE OF EVAPORATION AS DETERMINED BY TEMPERATURE DIFFERENCE, Cy ey Cy-Jy T | T(C,-Jy) Cy Cy C\-C, T | T(Cy-C,) 221 On| 4200 %5 I0°5 561 5850 230°7 | 22053 10 °4 453 4710 220°8 | 210°5 10 +3 621 6396 226-9 | 216°8 IO °I 495 4999 220-8 | 210-8 I0-O 670 6700 223-320 3%0 9°7 525 5093 220°9 | 211 <3 9°6 693 6653 220) I 2TOnS 8 +3 562 4665 22 t-te 203 9°3 770 7161 216°0 | 209°7 6°3 afi 4479 223. -0)|2252 "0 9:0 825 7425 212°4 | 207 °5 4°9 |} 915 4485 Gia lee ara) Tare (C5—C,) Cy VS, \(Cz-VSy)). T. TIC Se 220.51 a\e2 LO +7, 9°4 568 5339 T7602 (| T2265 BS} OF) 568 - 3049 22Or i ee Teo g°I 599 5491 gfe ts) || ALS) 6 51°8 599 3103- 220°0 | 211 *2 8-8 640 5632 I8I -O | 130°0 51-0 640 3264 2h Oe? Lebar 855 692 5882 183 -I | 134°9 48 -2 692 3336 220°0 | 211 °5 8 +5 7OI 5958 1830 | 135°0 48-0 7O1 33605 Poy ess | ana OF] 8-1 754 6112 187°5 | 140-4 Ae 754 3552 220eT | enone 7°9 haf 6098 188-0 | 145°1 42°9 772 32Ta 220 cia ee ees Gp or 835 6432 189-0 | 148-4 40-6 835 3390 | When, however, the temperature differences are very great, and are located in different positions in the thermometric scale, a difterent law obtains. Rankine! assumed the difference was in proportion to the square of the temperature difference, as was later indicated by the experiments of Blechynden.? The passage of heat through a partition takes place in three stages :— 1. The passage from the hot fluid to the partition. 2. The passage through the partition. 3. The passage from the partition to the cold fluid. Péclet’s classical equation? representing these conditions is :—Let a, b, ¢ be the coefficients of heat transfer at entry, through the partition, and at exit ; then if & be the quantity of heat transferred in unit time, through unit I ; : De es ees: ET area with unit temperature difference, joa + - on ao he = 1 ie a? oe Now suppose 0 is very large compared with a and c ; then it follows that will be very small, and the heat transferred will depend on the resistances ' ¥ I at entry and at exit or to a and ee For evaporators this subject has been studied by Holborn and Ditten- berger? and by Austin®; using their results, Aulard® finds the following values for a, b, c in beet sugar juices in multiple effects :— Cell I Cell IL Cell 1 Celia Conductance at entry = 4 d< ote O33 O°125 O-III 0 -067 HA through partition = 6 I I I I a dexter es bes oO? 22 0 +200 0-069 0 +042 The above values for b refer to brass tubes: for the fourth cell the relative EVAPORATION 313 value of & is = : 7 = 070250. If the partition be neglected at eS a 0-067 ° 1 0-042 altogether, the value of & is eal = 0-025I, so that the effect of 0-067 To. 042 the brass tube is barely appreciable. The relative conductivity of copper to brass is about 3 : I, so that substituting copper for brass would only cause the value of & to rise to 0-0256. The conductivity of copper is not the reason for its use in evaporators and heat transference apparatus generally; the real reason lies in its resistance to corrosion, and possibly to some extent in conservatism. As regards the manufacture of white sugar there are in ad- dition other grounds. Brass, which is frequently substituted for copper, has a conductivity substantially the same as that of iron or steel. It is easy to see from the above equation that the transference of heat is governed by the low conductivity of any one element, and not by the high conductivities of the others; hence, if an evaporator is not kept clean, application of principles of heat transference and the skill of the designer are rendered null and void. A badly designed clean evaporator will operate more efficiently than a well-designed machine the tubes of which are allowed to become coated with a deposit of scale. As regards velocity of steam flow, most engineers now seem inclined to revert to Osborne Reynolds’ hypothesis,* namely, that the transmission co- efficient is directly proportional to the product of density and velocity of the fluid, or to the weight passing per unit time and per unit area; experi- ments made by Jordan® with hot air and water confirm this hypothesis, and possibly the variations found between other experiments may be due to neglect of the precautions necessary to keep other controlling conditions constant. Jordan states with regard to the passage of heat from air to water :— ( weight per sec. \area of passage mission coefficient is directly proportional to temperature difference. (2) For a constant temperature difference, the transmission coefficient increases with the velocity under a lineal law. (3) Other conditions being equal, the transmission coefficient increases with rise in the absolute scale of temperature. (4) The transmission coefficient depends on the area of the passage and increases as the ratio, ‘‘ area ‘circumference,’ decreases. The effect of variation in the velocity of the liquid has been studied by a number of investigators who find the relation K = C V” where K is the transmission coefficient, V is the velocity of flow. C is a constant, and ” varies from zero to unity ; when # is zero, velocity has no influence, and this condition might occur in the case of the presence of some other dominant factor, but generally m is given by different ex- perimenters as one-half or one-third. The latest and very detailed experiments of Orrok® give K = 308 V3, with V in foot-second units; this expression relates to design conditions for surface condensers referred to a 27-inch vacuum. The presence of air in the steam decreases the value of a or the conduc- (1) For a constant mass flow = constant), the trans- 314 CHAPTER XVIII tivity at entry. Orrok, referring to surface condensers used with steam turbines, expresses the relation thus: let P, be the partial pressure due to the steam, and P, be the total pressure ; then the coefficient of transmission . jen . varies as ( a ; to the exponent 7, values varying from 2 to 5 have been t assigned, Orrok’s experiments pointing to the latter value. In tubular condensers the length and the diameter of the tube have an influence on the transmission of heat, the generally accepted formula being K = —*__ | wherec is a constant and d and / are the diameter and length Val’ respectively. With decreasing diameter it is easy to.see that the thickness of the wall of liquid through which heat has to be transmitted decreases ; it is not so easy to realise what influence length will have. In vertical submerged tube evaporators, however, increase in length of tube increases the hydrostatic head or pressure under which the lower layers of liquid boil, and also increases the length of time taken for a drop of water to trickle down from the top to the bottom of the tube. The passage of heat to the atmosphere from a steam pipe, a tank full of hot juice, an evaporator, pan, or juice heater, may be considered as a special case of the transfer of heat through a partition. In the case of a bare pipe the coefficients a and b in Péclet’s equation may be considered as of the same order as those found in surface condensers. By the substitution of air for water or boiling juice the value of c is many times decreased, and when a non-conducting material is placed round the partition the value of 6 is also decreased. The question is complicated by the dissipation of heat being also due to radiation and convection, as well as conduction ; in any case, however, the loss of heat cannot be greater than what can pass through the partition. In the case of a hot body separated from air by a partition, heat will pass through, and eventually, if there is no loss of heat, both sides of the partition will be at the same temperature and no more heat will pass. As soon as heat is lost by radiation and conduction, the temperature of the external side falls, and heat again begins to pass ; this process will continue until the external side is at such a temperature that the heat which passes under the temperature difference is exactly balanced by that given off by radiation to and conduction by the air. The dominant factor controlling the loss of heat will be the final difference in temperature between the external side of the partition and the surrounding air; this in turn will be controlled by the conductivity of the partition, the teniperature of and circulation in the air, and the nature of the external surface of the partition. The combined effect of all these influences, called the exterior conductibility or surface emts- sivity cannot be combined in one genera! formula, although a number of empirical formule have been suggested. For small and nearly related temperature differences the loss is directly proportional to the temperature difference, but the loss for mx degrees is more than m times the loss for % degrees when m is large, the proportionate difference increasing as m increases. As the loss in steam pipes is partly controlled by the value of a in Péclet’s equation, or conductibility between steam and partition, an explanation is afforded of the less loss found with superheated compared with saturated steam. Although the former is at a higher temperature, its conductibility EVAPORATION 315 is lower, and may more than counterbalance the effect of its higher tem- perature. : Conception of Multiple Effect Evaporation.—Heat may be quantitatively exchanged from one body to another, the heat always passing from that body with the higher temperature to that with the lower. If one pound of water at 80° F. be mixed with the same quantity at 60° F. there will result two pounds at 70° F. ; similarly, if one pound of water at 80° F. be contained in a vessel, separated by a partition from a second pound of water at 60° F., eventually 10 B.T.U. will pass from the hotter water to the colder, and there will again result two pounds at 70° F. If steam be conducted into water, the former will condense until the temperature of the water has been raised to the temperatute at which water boils under the prevailing pressure, after which nearly equal quantities of steam will enter and pass away. If, how- ever, the steam be not conducted directly into the water, but be directed against the outer wall of the vessel containing the water, it will condense and transfer its latent heat to the water ; and, if the heating steam be at a higher pressure than that prevailing on the surface of the water, the latter will eventually boil. There will then be a system in which the water and the vessel containing it act the part of a surface condenser, as opposed to an injection condenser, where the steam is conducted directly into the water. To give an arithmetical calculation let there be Io lbs. of water at 82° F. contained in a vessel open to the atmosphere, and acting as a surface con- denser to a current of steam at 227° F., which condenses, and is by some device or other removed at this temperature. Referring to the table at the end of this chapter, the latent heat of steam at 227° F. is 960-1 B.T.U. ; to raise the Io lbs. of water from 82° to 212° requires 130 B.T.U., and hence when (130 X Io) = 960-1 lbs. = 1-354 lbs. of steam have been condensed, the water will begin to boil. The latent heat of water at 212° F. is 969-7 B.T.U., and after boiling has begun each pound of steam condensed will cause the evaporation of 960-1 + 969-7 = 0-qgI Ib. of water as steam at ae Now let the steam evaporated at atmospheric pressure be collected and conducted to a second surface condenser, in which a pressure of less than one atmosphere is maintained ; exactly the same process is repeated, and the original pound of steam can in this way be conceived as causing the evaporation of an infinite quantity of water. Multiple effect evaporation is, then, a scheme for the alternate condensation and generation of steam under continually decreasing pressure. It is to be observed that ‘“‘ vacuum ”’ (or pressures less than atmospheric) has as such nothing to do with the principle, which is applicable over any range of temperature or pressure. The adoption of vacuum multiple effects in the sugar industry is due to the destruction of sugar which occurs when temperatures considerably above 212° F. are reached, and also to the pro- duction in the engines of large quantities of low pressure steam, the multiple utilization of which is possible only under reduced pressure. The method of obtaining the successively decreasing pressures will be understood by reference to the diagram, Fg. 183, which represents a vertical submerged tube triple effect. Each body consists of a vertical cylinder divided into two compartments by means of two transverse partitions, which are connected by tubes open at both ends. The transverse partitions are known as tube-plates, and between them and exterior to the tubes connecting them is 316 CHAPTER XVIII formed a chamber separated from the rest of the body. This chamber, which is known as the calandria, receives the steam which causes evaporation in that body. The space beneath the lower tube plate, within the tubes, and a small distance above the upper tube plate is filled with the juice under- going evaporation ; the space above the level of the juice is called the vapour space, and it communicates with the calandria of the next succeeding cell by means of a conduit, b, known as the vapour pipe, and by means of an opening in the side of the shell of the body. The vapour pipe from the last cell leads to a condenser, where it is condensed by means of a continuous supply of cold water, combined with the removal of air by means of a pump. By this means a very low pressure is obtained in the condenser, and a pressure only a little greater in the last vapour space. The calandria of the first body communicates with a source of steam by a pipe, 0, corresponding to the vapour pipes in the other vessels. The juice is introduced into the first body by the pipe a, and continuous communication, controlled by valves, is made by pg Fic. 183 the pipes a to the last body through the intermediate body. From the calandrias of the second and third bodies small pipes, d, also pass to the condenser, directly or through the last body as shown. These pipes, known as the incondensible gas pipes, are provided with valves. Suppose such a system filled with juice in each body to the level of the upper tube plate. By means of the pump the air is exhausted as far as possible from the last body, and by means of the incondensible gas pipes a less degree of exhaustion can be obtained and controlled in the other two bodies. Let steam at a temperature sufficiently elevated be introduced into the first calandria ; its condensation will cause the juice there to boil at the tempera- ture corresponding to the pressure in that cell. The steam or vapour given off here will pass on to the second cell, and condensing will cause the juice there contained to boil, since a lower pressure prevails. A similar process takes place here as between the second and third body. When once started the pressures and temperatures adjust themselves as long as there is a con- tinuous supply of steam and juice, as long as the vacuum or reduced pressure is maintained in the last body, and as long as the incondensible gases are removed, EVAPORATION 317 As the steam in each calandria condenses to water it is removed from the calandria by the drain pipes c, and evacuated against the atmospheric pressure by pumps, or other devices described elsewhere. At e is shown a washout pipe: In actual working in sugar manufacture the material to be evaporated is nearly always introduced to the first body only, and passes on to the last body with continually increasing concentration, whence it is pumped out against the atmospheric pressure. Similarly the steam is generally intro- duced to the first cell; there is no reason why the direction of flow of juice or of steam either separately or simultaneously may not be reversed, and this scheme forms a feature of one type of apparatus referred to elsewhere. It is also employed for special purposes in other industries. Coefficient of Transmission.—The coefficient of transmission is that quantity of heat which passes through a partition of unit area, in unit time, under unit temperature difference. In British and American engineering practice the units selected are the square foot, the hour and the degree Fahrenheit, the quantity of heat being expressed in British Thermal Units. In European practice the square metre, hour, degree Centigrade and calorie are used, so that the British or American coefficient is 3-96 times as great as the continental European value. No difficulty attaches to expressing the coefficient of transmission in a heater or single effect evaporator, but in a multiple effect it is to be noted that the mean coefficient is not the average of the individual coefficients even when the cells are all of the same area ; actually, if / be the total heat transmitted, ¢ be the total temperature difference, a be the total heating surface, and ” be the number of effects, then the value of the coefficient h is eee t or = and if h’ be the heat transmitted in one cell the coefficient n nh’ becomes —— at For example in a triple effect of I,000 sq. ft. in each cell, with temperature falls of 10° F., 30° F. and 60° F., and transmitting 6,000,000 B.T.U. per hour per cell, the coefficients in the first, second, and third cells are, respectively, 600, 200 and 100. The total heat transmitted is 18,000,000 B.T.U., and, since the transmission occurs in three stages, the mean coefficient for the whole 18,000,000 apparatus is 10n— i000. 5,000 Xx = 3 Distribution of Heating Surface for Maximum Efficieney.*—In a double effect let k, and k, be the coefficients of transmission in the first and second cells in which the heating surfaces are a, and a, and the temperature differ- ences ¢, and ¢,. Let a, + a, = 1, and also #, + 4, = 1. Then evidently h, = hy = kh, a, ty = Ry ag t, where A, and hy are the quantities of heat transmitted. * For this demonstration I am indebted to Mr. Louis Wachenberg. 318 CHAPTER XVIII Now @, = I — @, andi, = I — t,, whence h, =k, a; +, = Rh, (I — 4) (I — h), or Rk, a, t; = ky — hy ty — Pg a, + Fz a by, ky (I — a) a, (Ry — ke) +k Ry ky a (I — 4%) a, (Ry — Ra) + Ry Differentiating and equating to zero dh, =d { [As hy @ (I — @,)] [a, (ky — Fe) +.) 7} Solving, t, = Wherefore h, = hk, 4, = dh Re. = (ky — Fy) a” + 2 ky a, — kh, =0 —hky +vky k, Solving, a, = ——_1 4, § 1 ky eat ke anda, =I—a fae Wade Dee, lS ae ae ae ir hk, —k. whence 4 — — yas V hy he gfe al Gee leas WV Ri Re ky . and generally if a,, ay, a3 .... are the heating surfaces, and fy, ky, Rg ..-. the coefficients of transmission, then for maximum efficiency or for the passage of the greatest quantity of heat Bae Vig a Vg -- —8 gn OU ta) Vk, a, VR Weer ; ; t V ks ty Vk, ; 3 Similar reasoning gives !———, >; =——, so that in all cases for oe 4, VE, & maximum efficiency the division of heating surface and of temperature difference is the same. As a numerical example, let the coefficients of transmission in the first, second and third cells of a triple effect be 9, 4 and 1. Then for maximum a 2 a ieee efficienc at ee ay MIT ip NG 3 a3 V4 2 d if + a, + = iene lg ee eg an ay , + 4 = 1, then a, — —, = 5 &= 7 ee eR A eae ere ie eee eos ee eae oe aaa gesagt Zoe nie, BeaS 6. 62536 = —= — = a = = = i & — i and k, a, t, QUA aero Ry Go te eet So kg a3 ty x7, *\ 2 which is the maximum value under the stated conditions. Within the limits that occur in practice, however, no great advantage is to be found in dividing the heating surface as indicated above. Economy in construction costs is obtained by building all vessels of equal size, and there are reasons to believe that in the last cell where a very viscous material is boiled, the coefficient transmission increases more rapidly than does the temperature difference. It is well then to aim at having a large temperature EVAPORATION 319 difference here, and since the transmission coefficient is least in the last cell, this end will follow when the cells are all of equal size. Computation of the Conditions in a Multiple Effeet.—Let the temperatures in the four cells of a quadruple be 212° F., 203° F., 185° F., and 130° F. Let 1 lb. steam at 227° F. and 6 lbs. juice at 212° F. enter the first effect, the specific heat of the jure being 0-9. The I lb. steam at 227° F. condensing and passing away as water at 212° F. to Cell 2 gives up 975°2 B.T.U. and evaporates 1-006 Ibs. of water from and at 212° F. There passes on to the calandria of the second cell r-006 Ibs. of steam at 212° F. and 1 lb. of water also at 212° F.; 2-006 lbs. water leave the calandria of Cell 2, so that in all 978-8 B.T.U. have been surrendered, and the corresponding evaporation from and at 203° F. will be 1-013 lbs. water. Simultaneously 4-994 lbs. of juice pass from Cell I to Cell 2, and in cooling down from 212° F. to 203° F. give up 4-994 * (212 — 203) X 0-9 B.T.U., or 40-5 B.T.U., corresponding to the evaporation of 0-042 lb. water.* The total evaporation in Cell 2 is then 1-055 lb. of water. 14006 /bs 2/2°F 4085/b3s 203°F 1166lbs (85°F 42264 430 — e SSS a — . él 924 (bs 298923, STG 2 429816 130°F Yvuice Condeaocd Water Stream Fic. 184 Following on these lines the total evaporation in Cell 3 is determined as 1-165 lb., and that of Cell 4 as 1-476 lb. water. The final state of the apparatus is then as follows :— Water at 130° F. discharged from Calandria 4 ‘ 4-226 Ibs. Steam at 130° F. discharged from Vapour space 4 .. I -476 lbs. Syrup at 130° F. discharged from Cell 4 Sie ee =e -b296 Ibs, These results are shown diagrammatically in Fig. 184. The total evaporation per lb. of steam is 4-702 lbs., and expressed per unit of juice admitted the final position is :— Juice at 212° F. I -000 Condensed water at 130° F. 0-704 Syrup at 130° F. and 0 -6 a es heat 0-216 Vapour at 130° F.- .. : ae 0-246 Steam admitted at 227° F. 0-167 Water evaporated 0-784 This computation gives in a quadruple effect 4-702 Ibs. water per Ib. * This is known as “self-evaporation.” 320 CHAPTER XVIII steam as the maximum possible evaporation. The method of computation assumed that the condensed water in each cell passed on to the next with complete transference of heat, and that the juice entered the first cell at the temperature there prevailing. Under actual conditions the juice usually enters at a lower temperature, the condensed water is not generally passed on, and the exchange of heat is not complete. In addition, no account is taken of radiation losses and of heat carried forward in the evacuation of the incondensible gases. Further, as stated later, the exchange of heat between condensed water and juice is very small, and some amount of super- heating of vapours occurs. So great an economy can never obtain, and some experimental results are given later, which may be compared with those computed above. With evacuation of the water separately from each cell the maximum computed evaporation per pound of steam will be found to be from 4:3 to 4-4 Ibs. water. In a triple effect the evaporation as computed above will be from 3-4 to 3-5 lbs. with circulation of the condensed water, and from 3:1 to 3:2 lbs. with its separate removal. In so far as the effect of introducing juice below the temperature of ebul- lition in the first cell is concerned, it is to be remembered that heat consumed in elevation of the temperature is not used in multiple effect. In a quadruple effect the evaporation per pound of steam supplied will be as indicated below, with juice introduced at the temperature shown and as computed on the lines used above. Lbs. water per Ib. of Steam. Temperature of Wee Jiuicesk Condensed water Condensed water | circulated. separated. 160 | 3 69 3 29 105 Shells, 55h 170 3°85 3°46 175 3-96 3 756 180 4-06 3°65 185 4°16 3°95 190 4°26 3-84 195 | A °37 3°94 200 4°47 4 104 205 4°57 4°13 210 4.°67 4°2 According to the computations above there is a progressively increasing evaporation in each cell, which with circulation of the condensed water is :— Cellet Cell. II. Cell III. Cellisiive I -000 I *057 I -164 I -479 21 3% 22 4% 24 8% 315% If the juice enter at B, and leave at B, the total evaporation per I00 B wag 0 Ja} 13° Brix, it will leave at 60-8° Brix, and the total evaporation will be juice is If, in the case worked out in detail, the juice enter at EVAPORATION 321 78-6 per cent., while the degree Brix of the juices leaving each cell wil! be Cell 1:13 >. (0-786 X.0-213) = 15°6. Cell 2: 13 + {I — 0-786 (0-213 + 0-224)\ = 19-7. Cell 3: 13 + {1 — 0-786 (0-213 + 0-224 + 0-248)} = 33:8. Cell 4: 13 + {1 — 0-786 (0-213 + 0-224 + 0-248 + 0-315)} = 60°8. The conditions as determined experimentally in a multiple effect are not as computed, and hence it is not advisable to use these results as a basis of design or for other purpose generally, except as a means of demonstration of underlying principles. The Actual Conditions obtaining in Multiple Effect Apparatus.—In the following pages an account ‘s given of observations made by the writer, chiefly on a vertical submerged tube quadruple from which steam was not separated. The nomenclature adopted is shown in Fig. 185, where C, J, VS, and CW, distinguished by appropriate suffixes, denote the temperatures of the steam in the calandria, of the juice, of the vapour space, and of the Fic. 185 condensed water. C was observed in the vapour pipe immediately before it entered the calandria ; VS was observed about three feet above the upper tube plates ; J and CW were observed in the pipes as the juice or water left an effect. The temperature difference in any cell is C, — J,,, and the total tempera- ture difference is C, — J,, where 1 is the number of vessels: the values of a oar Cou4y iG Was were found to be very close together and to be in descending order of magnitude. In what follows C,, —C,,., is usually taken as the temperature difference in any cell, since these temperatures are the ones most easily observed, and GC, — VS, is sometimes taken as the gross temperature difference. Distribution of the Temperature Difference——Under the conventional methods of operation the total available fall in temperature is of the order too° F. This fall is unevenly divided between the cells, and it is the last cell that absorbs an undue proportion of the available fall. The balance of the temperature difference is unevenly divided between the other bodies. In an apparatus with each cell equally clean there are reasons for believing Z 322 CHAPTER XVIII that C, — J, ee I +25 1°75 55 17-8 -=eEe2s I-00 I +50 74 19°5 = er=40 Juice Distribution and Circulation—In very many apparatus the juice is introduced above the upper tube plate, the pipe ending flush with the side of the shell. This method is, the writer believes, quite wrong. Conversely, the juice should enter at the bottom and rise through the tubes ;_ this intro- duction may be made by means of a perforated pipe or at anumber of places symmetrically located with reference to the axis of a cell. The former method is specifically claimed in Smith’s U.S. patent (881351, 1908). In order to obtain a circulation, apparatus are constructed with a large tube or down-take, the route of the juice being up through the tubes and down through the down-take. This tube is usually located centrally, but in some designsis placed eccentrically, and in others takes the form of a segment cut out of the calandria. In other designs the circulating tube takes the form of an annular space between the calandria and the shell, this type being referred to as a drum calandria, as indicated in Fzg. 189. Circulation may also be assisted by shaping or bellying the saucer, as seen in Fletcher’s patent (13857 of 1894), or by inclining the calandria, as found in McNeil’s patent (8763 of Ig00). EVAPORATION 345 A system of circulation found in some designs is that known as progressive evaporation, in which the liquid is constrained to travel in a definite path, This system is first found in British patent 3965, 1816, taken out by Dihl for an unnamed inventor. It appears in Chapman’s patents (1752 and 2511 of 1888) and in Foster’s (13284 of 1890), where the flow is defined by vertical partitions alternately above the upper and below the lower tube plate of a vertical submerged tube apparatus. Mechanical circulation as obtained by a screw propeller located below the lower tube plate is found in Fletcher’s patent (14164 of 1886), but this means does not seem to have come into common use. Distribution of the liquid over the heating surface in thin layers as a spray, or by other means, forms what is known as film evaporation. It appears first in Cleland’s patent (4696, 1822), and is also shown in Rillieux’s first Fic. 189 FIG. 190 patent (U.S. 3237, 1843). Since then the principle appears in many designs, particularly in those of Yaryan, Lillie, and Kestner (q.v.), and more recently in that of Meyer and Arbuckle (4212, 7078, 19962, of 1903), who employ a perforated pipe rotating in a horizontal plane above the upper tube plate of a vertical submerged tube apparatus. Circulation by a localized use of high pressure steam is found in Heck- man’s circulators, which consist of a supplementary calandria, as shown in Fig. 190. In Rohrig and Koenig’s design, the live steam is used in a small annular tubular cluster arranged round the vertical axis of a cell. Incondensible Gases.—In the process of evaporation a certain amount of incondensible gas is formed ; some air enters with the juice, and some leaks into the apparatus. This accumulation of gas both retards the rate of boiling and causes corrosion of the tubes, so that it is necessary to remove it as fast as possible. In the first calandria there is generally a pressure, so that the gas can be vented to the air; as the heating steam contains but little air, generally all that is necessary is to expel the air present in the calandria when commencing work. In the second and subsequent calandrias communication is made by means of pipes from the interior of the calandria 346 CHAPTER XVIII to some place where the pressure is lower, as, for example, to the vapour space of the same cell. Various arrangements of piping are shown in Figs. IgI, 192 and 193. As arranged in Fig. 191,the pipes lead directly from the upper tube plate to the vapour space of the same cell and end flush with the upper tube plate. — In this arrangement the degree of opening is not under the control of the operator. As shown in Fig. 192, perforated pipes pass through the calandria ; the collecting pipe passes through the side of the apparatus and on to the calandria of the next cell; a valve allows the opening to be regulated. As indicated in Fig. 193, collection takes place at the top and the bottom of the calandria, the collecting pipes uniting into one outside the vessel, where a valve is placed. In this arrangement the collection of the gases takes place at a point remote from the steam entry. The gases are sometimes vented from cell to cell and sometimes direct from any cell to the condenser. In the latter case all the steam which AMT i A Fic. 191 FIG. 192 Fic. 193 escapes along with the gases is totally lost ; and, besides, there will always be observed difficulty in regulation, owing to the large difference in pressure between the condenser and the earlier vessels. The loss of steam along with the gases has been given by Claassen, as based on Napier’s formula for the flow of gas from an orifice: G =n F Na ¢ v where G is the rate of flow, F the area of the orifice, p the pressure of the escap- ing gases, v their specific volume, and 7 a constant. If G is in lbs. per sec., F in sq. ins., p Ibs. per sq. in., v cu. ft. per Ib., » for circular orifices is about O23; Claassen shows that with large openings very serious losses of steam may occur, and for EPaeaeHe of 10,000 sq. ft. he adiwises the following openings :— First body 12 in.; second body 33—33 in.; third body 35 in.—1r in. fourth body 1,% in. ‘He also advises the use of diaphragms, the setting of which is left to the superintendent and not to the workman. The distribution of the temperature fall and rate of working of a multiple effect apparatus can be controlled by means of adjustment of the valves on the incondensible gas pipes. If the valve on the third vessel be opened wide, communication is established between vapour space 2 and calandria 4. —e rT EVAPORATION 347 A rise in the pressure in calandria 4 results, which is reflected back to vapour space 3, causing arise in pressure therein. The result is a greater temperature difference in cell 4 and a more rapid evaporation there and throughout the whole apparatus. The steam which is short-circuited from vapour space 2, however, now only works at triple effect and the economy falls. Similarly, steam may be short-circuited from vapour space I to calandria 3, in which case some steam will only operate at double effect. At times, when the last cell is getting foul at the end of a run, the concentration of the syrup and the capacity of the apparatus may be maintained by this means, and generally it will be economical to keep at high density in the syrup and eliminate as much single effect boiling in the vacuum pans as is possible. Evacuation of the Condensed Water.—The condensed water in the first cell being normally under pressure can flow out by gravity. This water is always separated from the other condensed waters and is used for boiler feed. The water may pass through a trap or inverted syphon to prevent FIG. 195 simultaneous loss of steam. If the apparatus is on a sufficiently high level the water can flow directly to the boiler feed tank, otherwise a pump is necessary. In the latter cells, which operate at less than atmospheric pressure, the following methods may be adopted :— (a) The water may pass from cell to cell through inverted syphons (Chapman’s patent 1752, 2511, 1888). In Fig. 194, a and b represent two cells, in which the vacua are respectively five and fifteen inches, or a difference in pressure equivalent to a ten-foot head of water. If the syphon in this is more than ten feet long a water seal will be formed at the lower part of the U due to the balancing of the two columns of water, and the water will continuously and automatically pass from cell to cell. This system is also applicable to juice circulation. . The “ flashing ’’ of the water into steam as it passes to the lower pressure seems to disturb this system, and in actual operation it is found necessary to make the syphon twice as long as the prevailing pressures indicate to be necessary. (o) The water from each cell gravitates to a sealing tank by a fall pipe. 348 CHAPTER XVIII The sealing tank may be on the ground floor if the apparatus is high enough, otherwise it has to be located in a pit. A pump is employed to raise the water from the sealing tank. Ian T5_5 Zadts. aN ~ “3 Pas [p= sen 4------4-------- (oT) oo 00 3 | | | 3) © ee {290 2 ae 000 allacg ono 600 Ig00 [000 00/190 ooo (c) Each cell is supplied with an individual pump. In this case the water from a cell may pass into a receiver connected with the vapour calandria of the one next in series. This receiver is known as a “ flash pot,’’ and has for its object the release and utilization of the vapour corresponding to the differ- ence in pressure between the two calandrias. EVAPORATION 349 (¢) The condensed water from each cell flows to the fall pipe.of the con- denser or to the wet air pump. The method most to be advised is the separation of the first cell water, all of which is used as boiler feed. The second cell water is also taken away FIG. 197 cell waters may be taken away jointly and form a supply for maceration, filter cake washing, molasses dilution, and general service. This system does not utilize the economy to be obtained from circulation of the condensed water, but is advantageous in other ways. Position of Cells——Usually the units are placed on the same level and generally in series. Where space is restricted the piled type may be used, 350 CHAPTER XVIII in which the cells are superimposed one on another. This design appears in Pecqueur’s French patent (6686, 1834), and in a number of recent designs. Horizontal Submerged Tube Apparatus.—The original Rillieux multiple effect was of this type, and for its historical interest one cell is shown in Fig. 195 ; some very early apparatus of this type still (1919) remain in operation in Cuba. The modern form is contained in the Welner-Jelinek design used very extensively in Germany, Austria and Russia, and in the derived forms of the Swenson and Newall in the beet sugar industry of the United States. The Welner-Jelinek apparatus is illustrated in end elevation and in longitudinal section in Figs. 196 and 197. The tubes forming the heating surface may be as much as twelve feet long and from three quarters to an inch and a quarter in diameter; they are supported in tube plates at either end, and in intermediate plates shown at 7, and are arranged in nests of nine or twelve. The steam enters the steam chest through the valves f and g, one being used for live and one for low pressure steam. The tubes are set at a slight incline to assist the flow of the condensed water to the collecting box at the opposite end to the steam entry whence it is removed through the valve h. The incondensible gases are vented through the opening 7. Internal baffles cause the juice which enters at m to make several changes of direction before it reaches the exit shown to the right of the steam valve g. An entrainment vessel communicating with the vapour space by the conduits c forms part of the usual design. The advantage originally insisted on in this type was the obtaining of a low level of the material being evaporated, and, in order to maintain this advantage without increasing the size of the shell, apparatus are built with two heating elements in one chamber, as indicated in Fig. 198. In contradistinction to the vertical submerged tube type, the heating surface of this apparatus cannot be cleaned mechanically in situ. Yaryan Evaporator.—This evaporator is included in patents 14162, 1886; and 213, 1888: U.S. patents 300185, 1884; 355289, 355290, 1886 ; and 383384, 1888. In this evaporator the juice occupies the interior of tubes arranged horizontally, through which it is pumped at a high velocity. As shown in Fig. 199, steam enters the shell at e, and juice entering at d passes through the tubes, leaving at g. The juice does not fill the tubes, but forms a film on the inner periphery. On arrival at the end of a run, juice and vapour pass through 7 to the separator /, seen in section in Fig. 200. The vapour passes up and down the baffle plates b, and thence by the pipe & to the next effect or to the condenser. The liquor passes through the pipe ¢ to the tubes of the next effect. This apparatus may be built with the vessels in either the same vertical or horizontal plane; it is now only exceptionally found in the cane sugar industry. Lillie Evaporator.—This evaporator is contained in patents 3006, 12391, of 1888; 11686, 1890; 7187, 1891; 11104, 1893; U.S. patents 341669, 344586, 1886; 378843, 1888; 422234, 422235, 440231, 1890; 466862, EVAPORATION 351 1892 ; 491659, 1893 ; 521215, 1894; and a number of other patents dealing with details. As originally proposed, the Lillie model was a vertical tube apparatus, with juice distributed as a film on the interior of the tubes. In the form in Fic. 200 which it has become widely used in the cane sugar industry, horizontal tubes are employed, on the exterior of which is distributed a film of material. 352 CHAPTER XVIII One cell of a form of the apparatus is seen in.section in Figs. 201 and 202: The heating tubes ¢ vary in length from 5 feet upwards and are usually 3 inches in diameter ;_ they are expanded at one end into a thick tube plate, and are set at a slight incline, each tube having its own vent into the vapour FIG. 202 FIG, 201 space. The juice is circulated by means of centrifugal pumps c, and enters each cell by the distributing pipe, whence it flows as a rain over the surface of the tubes. Steam enters at g and leaves at 4. The condensed water is trapped at 7 and is circulated from cell to cell. The late forms of the Lillie apparatus are made reversible as regards direction of both liquor and steam. Kestner Apparatus.—This is covered by British patent 12502, 1906; EVAPORATION 353 U.S. patent I016160, I912. The apparatus depends on the principle of the climbing film, and is illustrated in Fig. 203. It is a vertical tube exter- nally heated apparatus, and consists of a vertical tubular cluster with tubes about 24 feet long. The juice enters the apparatus at the bottom through the pipe a, the heating steam entering at 6. Under the influence of ebullition the juice climbs up the interior of the tubes and passes on to the next effect in series by way of e. The condensed water is removed at f, and the steam generated after passing through a centrifugal separator leaves at d. Stillman Evaporator. — This apparatus, contained in U.S. patent 484831, 1892, is shown in Fig. 204. The method of juice I FIG. 203 circulation is the same as that in Chapman’s patents (1752 and 2511 of 1888), the central circulating tube, a, being used to establish circulation from cell to cell. Regulation of flow is obtained by a float and weighted lever combination, b, and in order to obtain a film effect the tops of the tubes project over the upper tube plate. Witcowitz Evaporator.—This type of evaporator, which has become established in central Europe, is illustrated in Fig. 205. The peculiar form of heating surface also finds application in the rapid heating of juices and syrups contained in tanks. 2B 354 CHAPTER XVIII Sandborn Evaporator.—In this apparatus (U.S. patents 1028792, Ig12; 1143074, 1915) the heating surface, Fig. 206, consists of vertical tubes, a, closed at the upper end and opening at the lower end into a steam chest, 0. The removal of the incondensible gases is effected by means of inner tubes, c, passing into the chamber d. This apparatus is referred to as the double tube type, and first appears in Beanes’ patent (2898 of 1853). Deerr Evaporator.—Patent 16544 of 1917; U.S. patent 1287650, 1918. This apparatus, Figs. 207, 208, 209, adopts a rectangular body, and in other respects is a vertical submerged tube design. The usual central circulating tube is developed into a down-take, a, extending the whole length of a vessel, and on either side are arranged the twin calandrias, c, provided with indi- vidual steam entries, 6. The incoming juice enters by the perforated pipes h, one to each calandria, and is taken away by the perforated pipe 1, lo- cated immediately below the down- take. The incondensible gases are FIG. 205 removed by the system of perforated pipes, d, opposite to the steam entry, and arranged in a vertical plane. The condensed water is collected by a system of pipes, f, formed in the lower tube plate, and passing into the header, g. In order to obtain a fall and rapid removal of water, the ap- paratus is erected slightly out of the vertical. Regeneration of Low Pressure Steam.—Pelletan (1840), Riltinger (1857), Felix (1871), Robertson (patent 790 of 1872), and Wiebel and Piccard (patents 5143 of 1878 and 1761 of 1883) were pioneers in attempting to introduce schemes whereby low pressure steam as from the first cell of a multiple effect is compressed to the pressure of the steam entering the calan- dria of that effect. The four first named experimented with the use of injectors. The Webel-Picard combination depends on the mechanical compression of the steam, and where power is to be had naturally the scheme is practicable. It is, or was, in successful use in a salt factory at Bevieux in Switzerland. EVAPORATION 355 The scheme has been described by Whitehead,!* and its mathematics fully discussed by Svorcik.17 Recently it has been put into operation by Prache and Bouillon (British Fic. 207 patent 26065, 1905). They employ an injector called a thermo-com- pressor. As applied to a triple effect thissystem isshown diagrammatically in Fig. 210. Live steam enters at a and aspirates and compresses a portion ea reeet ee re v RN eee y 7 * . or “~ - a? ak* ‘ * fe ‘ ihe’ 2 ¥ vt i q * ® F y s = “a P . . 7 5 . - o . Pa . , j é i - ! , ‘ EVAPORATION 369 Temperature of Cubic feet the discharge of cooling Cusitt_of Grerit.cot water, F°. water. air. air and water. 80 o -8192 O:‘II29 0 "9321 fete) 0 +5888 0 +0825 0 -6713 100 O*4112 0 +0703 o 4815 IIo 0 +2996 0 -0683 0 +3649 120 0 -2736 0 +0747 0 +3483 130 0 °2554 O*TT55 Daley 140 0 +2049 I°7712 I -9761 T40°5 ce os On examining these figures it will be seen that the volume of the air at first decreases as the quantity of water decreases, reaches a minimum, and then rapidly increases. Hence, if the air present in a condenser ts proportional to the amount of cooling water admitted, there is a definite temperature in the waste-water at which the volume of the air and water is least. This temperature in the waste-water is then the optimum for the particular condition, and the admission of more water beyond this quantity instead of affording a better vacuum has the reverse effect. Experimental data to calculate in advance this condition are wanting: it exists, however, and can probably be found by trial and error for each apparatus. If a series of calculations be made for different vacua, to obtain the optimum temperature of discharge, under the supposition that the gases introduced are proportional to the amount of water, it will be found that as the water increases in temperature so does the quantity required. The calculations lead to the following very rough approximation :— With initial temperatures of 60, 70, 80, go° F, the water admitted should be 10, 25, 35 and 50 times the amount of steam to be condensed. If further calculation on the above lines be made, it will be seen that for vacua of 24, 25, 26, 27 inches the volume of the air to be removed is roughly as 6, 9, I5, 25: that is to say, to maintain a 27-inch vacuum requires a pump DE on : 2 : = times as large as for a 24-inch vacuum. If, however, a quantity of air, x, enters which is independent of the water, the ratio will be = as and as x is positive the rate of pump capacity will not increase so fast. As regards relative pump capacity in wet-air pumps and dry-air pumps, some idea may be obtained from calculations made on the above lines. Under the same conditions it will be found that the volume of air from the dry system is usually only one-third or thereabouts that from the wet system, a condition which gives some idea of the relative pump capacity as cu. ft. developed per sq. ft. of heating surface, etc. As dry-air pumps can work at much higher speeds than can wet-air pumps, the actual size of the dry-air pump decreases still more in comparison. Empirical rules are very dangerous tools unless the basis upon which they are developed is known and appreciated. This is particularly true of vacuum pumps, into the necessary capacity of which so many factors enter. A collection of data of very many installations leads to the following very rough rules referred to dry vacuum pumps :— 2C 370 | CHAPTER XVIII Cupic FEET DISPLACEMENT PER MINUTE. Per. sq. ft: Per lb. of Per ton-cane- heating surface. vapour. hour. Quadruple on 0 *05—0 +075 I *5—-2 0 I5—-20 Triple are 0 :07—I :00 I -5—2°0 20—25 Pans oe 0*5 —I-:00 I +5——-2:0 I5—20 With wet pumps the displacement required is from 2-5 to 3 times as much. Cooling of Water.—In many districts, as for example in Cuba and in Mauritius, the supply of water is not sufficient for the needs of the condensers. It is therefore necessary to continuously cool and use over again the available supply. : The means adopted for doing this is the exposure of the water to the air in such a form as to expose as great a surface as possible. Cooling takes place by radiation, by contact through contact with the air, and also by means of the heat abstracted through evaporation. The appliances used to this end are either towers or spraying systems. Towers may be either enclosed shafts, to the top of which the hot water is delivered, and down which it flows over a series of trays designed to expose as much area as possible. A fan may force a current of air upwards through the tower, or natural draft may be used. This type of cooler is not to be found in sugar districts, and its place is taken by open towers. These consist of a. framework, usually about thirty feet high, on which at vertical intervals of about four feet are laid open horizontal platforms ; on these are frequently set faggots or brushwood, so as to increase the cooling area. The. hot water is delivered to a gutter or system of distributing gutters on the top of the tower. The sides of these are provided with saw cuts, and their inclination is such that an even distribution of the water is obtained. The horizontal cross section of the towers assumes various forms ; it may be circular or a long rectangle, ten to twenty times as long as broad ; or again a very efficient form takes the shape of three sides of a hollow square, the perimeter of which will be about fifteen times the width of the tower itself. Such a cooling tower is indicated in Plate XX VII. Expressions of the coefficient of transmission under these conditions can be obtained, but the assumptions necessary to be made are so broad that the results are very unsatisfying. Actual experience gives the following as a satisfactory basis of design :—Platform area, 300 sq. ft. per ton-cane-hour; cubic contents of tower 1,200 cu. ft. per ton-cane-hour ; capacity of cistern, 200 cu. ft. per ton- cane-hour. The general Cuban practice in connection with cooling towers is to place the condensers at a level so high that the overflow from the barometric seal will gravitate to the distributing system on the top of the tower. Recent practice in Cuba has tended towards the substitution of spray nozzles for the cooling tower, and such a system is illustrated in Plate XX VII. As usually installed each spray head is made up of five nozzles, each nozzle under a head of twenty-five feet having a capacity of 40 U.S. gallons per minute. Allowing twenty tons of cooling water per ton of cane this reduces to two nozzles per ton-cane-hour. As, however, a certain number of nozzles are out of commission being cleaned, and the capacity of those in action is reduced due to the presence of dirt in the water, three nozzles per ton- cane-hour would be a more suitable allowance. The pipes carrying the EVAPORATION 371 spray heads are spaced twenty-five feet apart, the spray heads being spaced thirteen feet centre to centre. A comparison of the two systems favours the spray system, both as regards first cost and renewals, the chief disadvantage being the annoyance following on the frequent choking up of the nozzles. In either system the loss of water is from 3 to 5 per cent., which has to be supplied from outer sources. Entrainment.—By this term is meant the carrying forward of material into the vapour pipes and its consequent loss. Three causes are at work :— 1. Material is splashing into the head boxes of the vessels. 2. Material creeps up the sides of the vessels due to capillarity. 3. Hollow drops or bubbles are formed, and when the forward velocity of the current of vapour is such that it exerts on the bubble a pressure equal to its weight the latter floats and is carried forward. This process is referred to as vesicular transference. It is in the last cell of the evaporators that these influences are mostly at work. They may be reduced to a minimum by the devices indicated below. Splashing losses may be avoided by giving a liberal height to the vessel and by placing ho1izontal guard plates in the body of the vessel. These guard plates may conveniently take the form of a ring, with its opening covered by an overlapping disc. This means is claimed in Vivien and Dujardin’s patent (2286 of 1884). Losses due to vesicular transference are best avoided by shock obtained by abrupt changes in direction, by a sudden decrease in velocity obtained by enlargement of the vapour pipe, or by a combination of these means. In Figs. 228 and 229 are shown two methods as applied in the vapour pipes. The Hodek ralentisseur, a standard European model, is indicated in Fig. 230. It combines decrease of velocity with the passage of the vapour through screens. Not dissimilar in action to the Hodek is the arrangement of Stillman (Fig. 231), shown in U.S. patent 484831, 1892. It is largely used in Hawaii, and is indicated in section in Fig. 231, as located in the body of a vessel. It is made up of three horizontal ihe each carrying a number of two-inch tubes, a tube in one plate being opposite a blank in others. A similar arrangement may be located as vertical baffles in a horizontal length of pipe, and in this case the chamber takes the form of two opposed pyramidal vessels. Types of centifugal separators are indicated in Figs. 232 and 233, the former being due to McNeil. What is perhaps the ‘most commonly used arrangement is indicated in Fig. 234, and this is due to Vivien and Dujardin, being claimed in patent 2286 of 1884. Finally a somewhat different device, based on a well-known form of oil separator, is indicated in Fig. 235. In this the direction of flow may equally well be opposite to that shown. Capillary losses are found mainly in the vapour pipes after the bubbles have burst, and hence all the devices indicated above must. be efficiently drained. Very often the drain pipe is led into, and terminates in, the vapour space of the effect. The downward flow of the liquid is opposed then to the rapid forward flow of the vapours, and a considerable quantity of material may be carried forward to the condenser. To avoid this the drain pipes may dip below the surface of the liquid, or an inverted syphon seal may be used. The writer, however, believes that the most satisfactory results are obtained by draining the save-alls into a receptacle external to the vessel. This receptacle 372 CHAPTER XVIII is connected to the last body by a pipe and valve, one also being located on the drain pipe. A third connection communicates with the atmosphere. When this receptacle is full, communication to the save-all is cut off, “and ATTEN ECE LE hq 231 tee the air cock and valve leading to the last effect are opened, when the contents | are sucked therein. In the complete absence of these devices, the writer has seen 3 per cent. of the juice Jost in the evaporation, a loss reduced to less than 0-1 per cent. by their well-advised application, EVAPORATION 373 Seale in Evaporators.—The concentration of the juice which obtains in the evaporators results in certain of the non-sugars becoming insoluble, and being deposited as “scale’’ on the heating surfaces of the evaporators. In addition to the scale formed from bodies originally in solution, there is that caused by the introduction of suspended matter due to inefficient defecation. The latter deposit is found mostly in the first cell, and the former in the last cell, where the concentration of the juice is greatest. The scales which are found in cane sugar houses fall into three classes—silicate, phosphate, and sul- phate scales, the two former being the most frequent. The quantity of scale formed is also a function of the lime employed, which may introduce silica. The use or non-use of phosphoric acid and sulphur will affect the quantity of the phosphates and sulphates in the juice. In the absence of the use of these agents the greater portion of the phosphoric acid is precipitated and is found in the press cake. Its maximum precipitation, however, depends (cf. Chapter XIII) on the use of an excess of lime when simultaneously lime salts enter into solution. Sulphates are frequently absent from the deposit of scale, but may occur in certain juices in very large quantity. The cause of this appearance is obscure ; it is, however, certainly to be correlated with variety of cane. It is evident that, while a deposit of scale due to suspended matter may be eliminated by careful work, that due to the deposit of dissolved matter is obligatory. It may be controlled by the use of selected limestone, and by using no more lime than necessary to protect the juice from inversion. The presence of sulphates in the juice is the most troublesome factor. Peck?* advises the use of sodium carbonate in the clarification, to precipitate the lime as carbonate and to substitute sodium sulphate for calcium sulphate. The prevention of the deposit scale has been attempted by placing in the tubes rods or chains, en which it was intended that the scale should deposit, and which by tapping continuously against the walls of the tubes would prevent the scale adhering. Rapid circulation is also believed to prevent the adherence, and the system of reversing circulation used in the Lillie horizontal film evaporators is claimed also to keep the surfaces free; but no mechanical means can alter the solubility of the substances causing scale, so that the most these schemes can do is to remove the scale from one part of the sugar house to another. Recognising the unavoidability of scale, the means for its removal remain to be considered. The agents most often employed are caustic soda or car- bonate of soda followed by hydrochloric acid. The strength of these solutions is from I per cent. to 2 per cent., and apparatus are boiled out periodically. The time required varies with the deposit of scale, but generally four hours’ boiling under atmospheric pressure with each reagent is sufficient to maintain a reasonable efficiency in the apparatus, if done once a week. The experiments of Peck and of Thurlow* indicate that generally sodium carbonate is as efficient in combination with acids as is caustic soda, and the use of the former is essential when removing a calcium sulphate scale, which has to be converted into carbonate before it can be attacked by acid. With a Silica scale the use of caustic soda in indicated, and with a phosphate scale acid alone is enough, provided the scale is not protected by a layer of fats or grease. It would appear not unreasonable to use a mixture of carbonate and caustic soda. The writer’s experience, however, is that all solution methods are inferior to mechanical ones as regards cost, speed, and efficiency. Small compressed-air motors operating wire brushes, and specially designed for 374 CHAPTER XVIII evaporator work, are on the market. With these it is possible to really clean three tubes a minute, and, as fourlabourers can easily work in one cell, an appar- atus can be very rapidly brushed. These apparatus are, of course, only applic- able to the vertical submerged tube type, and it is the latter’s amenability to mechanical cleaning that the writer regards as its one great advantage over all other types. This remark is equally applicable as between coil and calandria vacuum pans, the former of which can only be cleaned satisfactorily after dismantling. A deposit of another nature forms on the steam side of the tubes in the first cell, and has its origin in oil volatilized in the back pressure steam. This deposit can be reduced to a minimum by the use of an efficient oil separator, of which there are many types on the niarket. Even with these some oil wili find its way to the tubular bundle, and it will always be serviceable to remove this in the dead season. This can be done efficiently by filling the calandria with water, on the surface of which one or two inches of kerosene is floated. The water is allowed to drain out slowly, occupying four or five months in doing so. The fermentation of molasses and water will also effect the removal of this grease. A deposit of fats may also sometimes be found on the steam side of the tubes in the other cells. This probably has its origin from the vegetable fats and lecithins present in the juice. In the dead season it may be advisable to examine these bodies also. In the absence of fats a considerable amount of rust may likewise be found in them. This rust is readily soluble in very dilute acids, and its removal at the end of every season will tend towards maintaining the efficiency of the apparatus. Whenever an excessive fall in temperature is noticed in the first body, oil on the steam side may be suspected, and this oil may go on accumulating till the capacity of the apparatus is notably diminished. Oil will also be found on the interior of the coils in the vacuum pans which are used for exhaust steam, and these may be cleaned in the dead season by swabbing with kerosene. PROPERTIES OF SATURATED STEAM. (After Peabody.) ENGLISH UNITS. | Temperature Pressure lbs. Heat of the Heat of Specific Volume degrees per Liquid. Vaporization. cubic feet Fahrenheit. square inch. per pound. Se: pee See See oe ear eee ees eS fied: 32 0 -0886 0-0 1071-7 3308 33 0 -0923 I-o 1071 °2 3179 34 0 -0960 2:0 1070-7 3062 35 0 -0999 3:0 1070 :2 2950 36 0 -1040 4:0 1069 -7 2842 37 0 -1082 5-0 | 1069 -2 2737 38 O-1126 6 +1 1068 -7 2634 39 O-II7I uel 1068 -2 2538 40 O°1217 8-1 1067 :6 3446 41 0 +1265 gt 1067 -1I 2358 42 0 +1315 Io-l 1066 -6 2272 43 0 +1367 Ir-I 1066 -o 2190 EVAPORATION 375 PROPERTIES OF SATURATED STEAM.—Continued. ENGLISH UNITS. Temperature | Pressure Ibs. Heat of the | Heat of ~ | Specific Volume degrees per Liquid. | WVaporization. cubic feet Fahrenheit. square inch. | per pound. al Bia 5s Se ee) ee NS 44 O°I42r | 12-1 1065 °5 2110 45 ) 0 -1476 I3°I 1065 -O 2035 46 ! O +1533 I4°1 1064 -4 1963 47 O-I59r | 15-1 1063 ‘9 1894 48 0 *1652 16-1 1063 -4 1828 49 OF 7E5 > | I7°1 1062 -8 1764 50 | 0 -1780 I8-t 1062 -3 1703 51 o -1848 Ig:I 1061 -8 1643 52 o-r918 | 20-1 1061 °3 1586 53 o-Ig90_ | 21-1 1060 -7 1531 54 O -2064 ZEEE 1060 -2 1479 55 0 +2140 23-1 1059-7 1429 56 0 -2219 24-5 1059-1 1381 57 O +2301 25° 1058 -6 1335 58 0 +2385 26-1 1058-1 1291 59 0 -2471 a HS 1057 °6 1248 60 0 +2561 28 -I 1057-0 1207 61 O +2654 29-1 | 1056 °5 1167 62 0 +2750 30-1 / 1056-0 1128 63 | 0-2848 | 31 °I . 1055°5 | I09I 64 0 +2949 Bik 1055-0 1056 65 0 3054 331 1054-4 1021 : 66 0 -3161 34 °I 1053 °9 988 67 0-3272 | 3571 1053-4 956 68 0°3386 | 36-1 1052 ‘8 925 69 0 +3505 37°1 ! 1052 -3 806 ~ JO 0 +3627 38-1 1051 -8 868 7I 0 +3752 39°1 IO5I -2 840 7 o -3879 40-1 1050 °7 813 7 | O-4012_ | A4I-+I 1050 -2 788 74 ' O-4149 | 42-1 | 1049-7 763 75 0 -4289 | 43:1 1049 2 739 76 © +4434 | 44-1 1048 -7 717 vo, "0 +4582 45 "1 1048 -I 6905 78 0 -4736 46-1 1047 -6 74 79 0 +4894 47°1 1047 ‘I 654 80 0 +5050 48 +I 1046-5 634 81 0 +5223 49-1 1046 -o | 615 82 0 +5395 50-1 1045 *4 596 83 0 +5572 51-1 1044 °9 | 578 84 © +5754 52-1 | 1044 *4 . 561 85 | 0 +5942 5371 1043 °9 544 $5 0 -6134 54°71 1043 *3 528 87 | 0 -6332 55°1 1043 °8 513 88 0 +6535 56-1 1042 -3 498 -O 89 | © -6745 57° [ee AT 483 “4 go 0 -6960 58-1 ' IO4I +2 469 -2 oI .. | o-7181 59-L 1040 -6 455 °4 376 CHAPTER XVIII PROPERTIES OF SATURATED STEAM.—Continued. ENGLISH UNITS. Temperature Pressure lbs. Heat of the Heat of Specific Volume degrees per Liquid. Vaporization, cubic feet Fahrenheit. square inch. per pound, 92 0 +7408 60 «I 1040 -I 442 -O 93 0 -7642 61-1 1039 °5 429 ‘1 94 0 +7882 62-1 1039 :O 416-7 95 0 -8128 63 °1 1038 +5 404 ‘8 96 0 -8381 64:1 1037 °9 393 °3 97 0 -8640 65:0 1037 °4 382-1 98 0 +8907 66 .o 1036 °8 371 33 99 0 -g180 67 -0 1036 +3 360 °9 100 0 :9461 68 -g 1035 °7 350 °8 IOI 0 +9751 69 -O 1035 ‘1 341 +1 102 I +0047 70:0 1034 ‘6 331-6 103 I 0351 71:0 1034 °0 322-4 104 I 0663 2:0 1033 °5 313 °5 105 I -098 73:0 1032 °9 304 °8 106 I +131 74 °O 1032 °4 296 -4 107 I +165 75:0 1031 °8 288 -2 108 I +200 76-0 TOsie=2 280 -2 109 I °235 77-0 1030 °7 272 -6 IIo 1h Cat 78-0 1030-1 265 -2 IIl I +308 79:0 1029-6 258 -O 112 I +347 80 -O 1029-0 2500-0 113 I +386 81-0 1028 +4 244 °4 114 I +426 82-0 1027 ‘8 23820, a 115 I +467 83:0 1027 +2 23168 116 I +509 84-0 1026-7 225 °7 II7 I +552 85-0 1026-1 219°8 118 I -597 86-0 1025 °5 214-0 119 I 642 87-0 1025 :O 208 +4 120 I -689 88 -o 1024 -4 203 ‘0 121 I +737 89-0 1023 8 197 °8 122 I +785 90-0 1023 -2 192°7 123 1.°835 91-0 -022*7 187-7 124 I -886 92-0 1022 -I 182-9 125 I +938 93:0 IO2I +5 178 33 126 I -992 94:0 I02I -O 173 °8 L277, 2-047 95:0 1020 -4 169 -4 128 2-103 96 -o ro1g ‘8 165 -2 129 2 -LOT 97:0 IOIQ -3 I6I -I 130 2 +220 98 -o 1018 -7 157 °1 131 2 -280 99 :O 1018 7 Fic. 249 ated with live steam, exhaust steam being used in the calandria, the tubes in which are generally not less than four inches in diameter. Other arrange- ments of tubular calandrias are shown diagrammatically in Figs. 245 and 246, the object of these arrangements be’ng to obtain a sloping surface on which the massecuite may not lodge. - The inclined calandria is claimed in Frey- tag’s patent (8064 of 1888). Pans of this type, which afford two sq. ft. heating surface to one cu. ft. net capacity, were originally introduced into Cuba as a means of using up surplus exhaust steam from a multiplicity of small pumps and engines. At the present day they are again being largely installed in connection with the schemes described in Chapter XVIII for the economic utilization of steam, and for this purpose the short coil pans are equally applicable. Pans are also built with horizontal tubes similarinshapeand arrangement of heating surface to the Welner-Jelinek evaporator (g.v.), except that the 2E 402 CHAPTER XIX bottom is made sloping to allow of the discharge of the contents. They appear but rarely, if at all, in the cane sugar industry. Mechanical Agitation.—A patent (13286, 1850), taken out by Shears as agent, claims the use of a vertical screw in a vacuum pan. Many years later this same device appears in the Freytag pan, with a tubular heating surface, and in the Grosse coil pan, Fig. 249, and in the Reboux pan, Fig. 250. These pans, used in the beet industry for the slow methodical boiling of low-grade material, have not up to the present entered into use in the cane industry. Certain patents have for their object agitation by means of moving heating surfaces. Thus McNeil’s patent (8814 of 1899) employs a device similar to that of Bour’s evaporator (g.v.), while Czapiowski (15031 of 1902) employs a rotating coil similar to those once used in the Wetzel pan (q.v.). These devices have never come into use. Technique of Crystallization-in-Motion.—In a previous section it was stated that low-grade products when dropped from the pan should have a coefficient of supersaturation of 1-5 to 1-6. The object of operating with so high a coefficient is to push the work in the pan to the limit and to obtain there as great a crystallization as is possible. On cooling such a massecuite owing to the high viscosity crystallization will be very slow, and eventually a supersaturated mother liquor may remain, when it is time to dry the strike. There may be also much fine grain present, and the strike may dry badly and require much water to remove the viscous mother liquor. The supersaturation of such a material should be systematically reduced in the crystallizers by the addition of water until a saturated molasses SUGAR BOILING AND CRYSTALLIZATION-IN-MOTION = 403 results. Until the saturation point is reached the water added does not dissolve sugar or increase the purity of the molasses, but per orms solely the function of reducing the supersaturation. At the same time crystalliza- tion proceeds freely, and when all the operations have been properly performed a free-spinning material from which is obtained exhausted molasses results. The calculation of the quantity of water to add is best indicated by an example. The table given early in this chapter indicates that a strike of 60-5 polarization gravity purity and Brix 93-8° will give exhausted molasses. Let such a strike on leaving the pan be of 97-2° Brix. Let x be the quantity of water required to be added to reduce the material to a Brix of 93-8°. Then 0-972 = (I + %) 0-938, whence x = 0-036. That is to say, per I00 lbs. of massecuite there is to be added 3:6 lbs. of water or roughly 334 gallons per 1,000 cu.ft. This quantity of water should be added gradually, and in such a way as to ensure an equal distribut‘on. The rational location for introduction is at the bottom of the container, as the water will have a tendency to rise through the denser massecuite. Failing this, a perforated pipe may be arranged running the whole length of the upper surface of the crystallizer. The water when introduced should be at the same temperature as the massecuite. It is not to be understood that the table under which this calculation is made is generally applicable without change ; rather every factory should determine for its own use what are the most appropriate concentrations at which to strike and to dry these low-grade massecuites. On the other hand the general law under which the table in question was constructed remains valid and is applicable to any factory. The rate of cooling is of importance, since the rate at which sugar can separate from solution on to the surface of crystals is limited. Hence, if the rate of cooling be too great, a supersaturated solution is again formed. When crystallizers were first used, many were installed with jackets, into which either steam or water could be admitted. For use in the tropics this has been found unnecessary, and the natural rate of cooling as determined by the outside temperature seems to be what is required for the deposit of the sugar. Similarly, no advantage is gained if the rate of revolution is increased beyond that necessary to give the maximum rate of deposit of sugar from solution. The rate of revolution that experience has found desirable is about one revolution in 1? minutes. The size of crystal is also of importance since the deposit of sugar is essen- tially a contact process between solid and solid in solution. If be the num- ber of crystals in unit volume the surface area of the crystals is proportional to °4/n, and consequently the rate of desaccharification of the mother liquor will vary as the cube root of the number of crystals. Conversely, if d be the diameter of the crystals, the total surface area is inversely proportional to d. It follows then that as regards the rate of desaccharification a fine-grained massecuite is superior to one of larger grain. Larger crystals will then imply a longer period of cooling and more crystallizer volume unless compensated for by an increase in the rate of revolution, whereby the surface of contact between crystal and mother liquor is increased. This increase in speed should be in proportion to the diameter of the crystal or inversely in propor- tion to the cube root of the number of crystals. In operating crystallizers it is of importance to see that the blades of the stirrers are submerged, as otherwise in their movement they will force 404 CHAPTER XIX air into the magma, and so will form an emulsion with the molasses. This emulsion will be so light that it will float on the wall of sugar in the centri- fugals. Similarly, when a crystallizer is being emptied the stirring gear should be stopped. The temperature at which low grades should be dried is about 105° to 110° F. _ If allowed to cool below this limit the molasses becomes so viscous that any gain in sugar deposited is counterbalanced by the increased quan- tity of water required to wash the sugar in the basket. Crystallizing Tanks.—The receptacles in which the massecuites are received in order to be cooled in motion are either cylindrical or U-shaped. More capacity in a given floor area is obtained with the latter. A shaft located along the longitudinal axis of the vessel carries the stirring gear, which usually takes the form of a double helix, as seen in Fig. 251. Motion = j Zo, y 1 Ee. ow, q is usually transmitted to the shaft by a worm and wheel drive. The power absorbed is about 1 h.p. per 1,000 cu. ft. of massecuite. The tanks are made plain or jacketed. In the latter case water or steam may be admitted to the jacket so as to control the rate of cooling. In cane sugar houses this control is very uncommon, and excellent results may be obtained with an uncontrolled rate of cooling. a In the beet sugar industry rapid cooling tanks are sometimes installed by the use of which the massecuite is cooled and ready to dry in nine hours. Two forms due to Ragout and Tourneur and to Huch are shown in Figs. 252 and 253. The cooling surface of the former is a rotating helix, and in the latter a system of stationary tubes. In both patterns hot or cold water circulates through the tube system. The Huch pattern is also made as a vacuum erystallizer, permitting of the removal of water during cooling. Neither of these types has come into use in the cane sugar industry and possibly the vscosity of low cane products might prevent the deposit of sugar keeping pace with the fall in temperature. Caleulatien of Crystallizer Capacity——tThe calculat:ons given on page 395 show that the capacity depends on the gravity solids, on the purity as variables, and on the time considered necessary for cooling as a constant. SUGAR BOILING AND CRYSTALLIZATION-IN-MOTION = 405 Referred to four days’ capacity with massecuite of 55 purity and of 93° Brix occupying 23-5cu.ft. per ton, and with 100 tons of juice per ton of cane, the following general formula may be obtained: Cubic feet per ton-cane- hour = 2,200 X g.s. per cent. {0-00524 — 0:00024 (pf — 75)} where g.s. is ay aAininAniniaT Ai ini a0) ind the gravity solids in the juice and # is the polarization gravity purity. If, for example, there are roo tons of cane giving the same quantity of juice of 15 per cent. gravity solids and of 80 purity, there will be required 13,332 cu. ft. or 133 cu. ft. per ton-cane-hour. The design must allow, however, for the most adverse conditions, such as h‘gh Brix and low purity, as may result from burnt cane, and generally, in the absence of a detailed knowledge of local conditions, it is not advisable to install less than 150 cu. ft. per ton-cane- hour. Each crystallizer should hold one full pan strike, and if four pans be 406 CHAPTER XIX installed with a combined capacity of 40 cu. ft. per ton-cane-hour there would then be 15 crystallizers each holding one pan strike. If, as is often the case, | the crystallizers are laid out in a double row, 16 would be the number installed. Boiling Routines in White Sugar Manufacture—The same general principles apply to boiling in white sugar manufacture as in that of raw, _ with respect to which this chapter has been written. In details, however, there are several important differences. In the first place, owing to the necessity of washing the sugars, there results a much greater quantity of molasses to be handled, and this material suffers an increase in purity — over and above that of the mother liquor. Secondly, processes employing low sugars as seed grain are impossible, since a discoloured nucleus in the crystal would result ; the use of a pied-de-cuite or of high grade sugar as seed is, however, permissible and useful when a large crystal sugar is de- manded. A third point of difference lies in the treatment of the low grade sugars; evidently these sugars cannot be mixed with the white sugars, and they have to be marketed as low grades or else remelted in the juice and passed again through the process of defecation. This procedure is, however, not altogether to be recommended, as dark-coloured bodies are re-introduced into the juice. Finally, it is to be remembered that brightness and transparency in the material entering the pans is of perhaps more importance than is colour. A two-massecuite process is generally impossible in the manufacture of white sugar, and three boilings will nearly always be necessary. The first boiling is made from syrup alone, with or without the return of purging sytup (vide page 426), or of the rich molasses resulting from the washing of the sugar in the centrifugals, provided these are separated from the actual mother liquor. The second boiling is made from these last-mentioned materials, sometimes on a footing of first massecuite and sometimes grained separately. This massecuite affords a white soft-grained moist sugar very popular in the Orient; it may also be mixed with first sugar, only one quality of white in this case being marketed. The molasses resulting from this second boiling should be of purity sufficiently low to afford a low grade massecuite to be separated into a low grade sugar and waste molasses. REFERENCES IN CHAPTER XIX. 1. U.K. patent 5518 of 1900. 2. Sucrérie Belge, Nov., 1898. CHAPTER XX THE SEPARATION OF THE CRYSTALS THE concentrated syrup discharged from the pan consists of a magma of crystals and molasses. The molasses are separated from the crystals by causing the magma to be rotated at a great velocity in perforated baskets. In this way the whole mass is forced against the perforated wall, the molasses passing through the wall of crystals and the perforations in the basket. The machines employed are known as centrifugals or hydro-extractors. From one point of view this process may be regarded as one of filtration under great pressure. Receptacles for and Transport of Massecuite.—In modern factories the high-grade massecuites, which are dried without preliminary cooling, are discharged into large receptacles capable of holding a full strike of the pan. These tanks, which are usually cylindrical or U-shaped, and provided with stirring gear, may be placed directly over the battery of centrifugals or underneath the pans. In this case the centrifugals are provided with a smaller receiver, into which the massecuite is fed. This smaller receiver also con- tains a stirring gear usually operated by asun and planet motion. From this tank individual charging spouts lead to each machine. The most convenient system of handling is one operated by gravity. In districts, however, where cyclones or earthquakes occur a tall building is dangerous ; in this case it is usual to place the receptacles on the ground floor and to elevate the massecuite to the centrifugal supply tank by means of magma pumps, chain pumps, or preferably by compressed air. An earlier system included the use of tanks running on tramways, from which the massecuite was shovelled to the centrifugal supply tank. Ina second scheme once widely used the massecuite was discharged into cans holding about 500 lbs., which were transported on trucks to a hydraulic elevator, their contents being dumped into the centrifugal supply tank. Early Methods of Separation.—The original method of separating the crystals from the molasses was drainage, and to this day this method is still used in a few districts, the massecuite being packed into hogsheads with perforated bottoms. Pressure on the massecuite in cloth bags was patented by Wakefield (2506, 1801), and drainage into a vacuum by Vaughan (3261, 1809). Hague (4048, 1816 ; 5725, 1828) also patented vacuum drainage, adding thereto the use of compressed air on the surface of the massecuite ; this process was extensively used in London refineries, and also in the raw sugar industry. The removal of the adhering molasses, and its substitution by a clairce of high-grade syrup, is seen in Constant’s patent (3541, 1812), and is also 407 408 CHAPTER XX claimed in Howard’s classic patent (3754, 1813). This method passed into, © and still remains, a part of standard refinery practice in certain houses. Development of the Centrifugal.—The earliest reference to the centrifugal as a mechanical power is contained in Penzoldt’s French patent (8941, 1837), as applied to drying wool. Hardman’s British patent (9998, 1843) claimed the application of centrifugal force as a new principle for removing liquids from solids and was developed as being especially applicable to the sugar industry. The machine illustrated by Hardman was a basket carried on a vertical shaft, overhead belt-driven, and rotating in rigid bearings. He stated that the revolutions should be 800-1,000 per minute, and called his machine a molasses “ disperser.’’ The patent also claimed the liquoring of the sugar in the machine with high-grade syrup. Fic. 254 Very shortly after this a second patent was taken out by Alliott (10070, 1844), with reference to the drying of textiles. The upper bearing of his machine was supported at the end of an arm of a crane-shaped frame, a feature which still remains in use in certain machines. Another application of centrifugal force is due-to Seyrig (French patent 3947, 1848), in whose design the upper bearing of the spindle was carried in an inverted U-frame or arcade, supported on the curb or outer casing of the perforated basket. The machine was driven by friction cones or by buff wheels through belt gearing. This type of machine was extensively used, and some still remain in operation in cane sugar factories, especially in Brazil and Mauritius. A modernized form of this design appears in Fig. 254. A patent granted to Brooman, as agent (12742, 1849), fixed another standard type of machine, namely, that supported on top of the vertical spindle, combined with under-drive, as indicated in a modern form in Fg 255. Rotch, as agent, in a patent (13023, 1850), introduced a hemispherical THE SEPARATION OF THE CRYSTALS 409 bearing, on which the bottom of the spindle rests, and also a form of roller bearing, on which the hemispherical bottom of the spindle rests and rotates. He attempted to restrain the oscillations of the machine by suspending a weight to the spindle. This patent contains the germs of various later successful types. Instead of attempting to restrain the rotating basket in rigid bearings, all modern machines are so built as to be allowed to find their own centre of oscillation. This very important advance is due to Bessemer, who (patent 13202, 1850) described a machine suspended from a ball and socket joint free to find its own centre of gyration. The spindle of Bessemer’s machine was extended below the bottom of the basket and carried a loose wheel surrounded by a fixed curb. The object of this arrangement was to restrain the amplitude of any oscillation which might arise from lack of they SS) ZIT ce iS FIG. 255 balance in the load. Bessemer’s patent also claimed the inverted type of free machine, with the basket balanced on a ball and socket joint and under- driven. In addition, he claimed the use of a rubber buffer between the bushing and spindle, for the purpose of avoiding vibration and allowing a certain freedom of movement. In a patent (13416, 1850) granted to Nind, as agent, the whole machine is described as suspended by elastic rods, the lower end of the spindle rotating in bearings surrounded by rubber buffers. The modern sugar centrifugal machine dates from Weston’s patent (3041 of 1867; U.S. patent 63770, 1867), and was developed by him when engaged as an operating engineer in the Hawaiian Islands. His machine, as shown in his patent, and from which the very latest machines only differ in detail, combined freedom of oscillation with a solid stationary suspended spindle supporting a hollow rotating spindle, to which is attached the per- forated basket. His patent did not claim suspension, but only the special means of suspension,* and he is in no wise to be considered the inventor of * A provisional patent issued to Johnson as agent {418 of 1852) mentions a hollow spindle, but gives no details. 410 CHAPTER XX the suspended machine, the credit for which is due to Bessemer, and to whose design the latest types of solid spindle machines tend to revert. Fig. 256 which represents a belt-driven Weston centrifugal, independent 164 NG VAI BM Vi A = ea fe fe wrwe aay i pr) TI yy & J iy LT A h] y q Depaul ale mae nls bi yaa ea maaan TTATT AA ARTA AAA aR TP ra'S 02 « ; pete 77 rs iardowetee oo aaws "aaa [) i Wi Fic. 256 of certain refinements of recent introduction, referred to later. The machine is suspended from a girder, C.F., by the socket §.B., which contains an india-rubber or elastic bushing, E.B., in which the solid stationary spindle I.S.is held. At the lower part of this spindle is placed a series of washers, A.W,, supported by the screw nut D.N. The outer hollow rotating spindle si THE SEPARATION OF THE CRYSTALS 4It carries the driving pulley D.P. and the basket B., and is supported by a shoulder on the washers. The outer casing or curb, which serves to collect the molasses, is shown at O.C., the molasses flowing away by a spout. The central valve, D.V., sliding on spindle, also forms a part of the patent claim. In the Hepworth machine (patent 3375 of 1871 ; U.S. patent 82314, 1868) the whole machine was suspended from a ball and socket joint. The spindle which carried the basket was solid and rotated in fixed bearings, which were attached to the curb or outer casing, so that basket and curb always remained concentric. Oscillations of the rotating basket were hence trans- mitted to the suspended outer casing, and the whole machine was free to swing. The oscillations were restrained by attaching the outer casing to fixed pins by means of rubber bands. This particular type of machine has “412 CHAPTER XX not survived, though once in extended use. It is illustrated as formerly made in Fig. 257. It is curious to note that the differences between Bessemer’s patent (13202, 1850) and Nind’s patent (13416, of 1850) are very closely paralleled by similar differences in those of Weston and Hepworth. Two other types of machine may be mentioned. Lafferty’s patent (235 of 1869) caused the solid spindle carrying the basket to pass through an intermediate hollow shaft, elastic material being interposed between the shaft and the spindle. The spindle was extended through and beneath the basket, terminating at its extremity in an elastic bearing. In Cottle’s patent (1350 of 1872) the solid spindle carrying the basket terminated in a hemi- spherical piece resting on a counterpart bearing. This device was further developed in Tolhurst’s patent (255 of 1878), who employed a spindle with a cone-shaped termination resting on a cone-shaped base, so that the machine was free to rock in all directions, the amplitude of the movement being restrained by rubber cushions. These types have been largely used in the. past, and the last-named machine, though not employed in the sugar industry, finds an extended use in other trades. The Centrifugal Basket and Screen.—The centrifugal basket consists of a vertical cylinder partly open at top and bottom, as indicated in Fig. 256. It is usually constructed of steel and is securely attached to the revolving spindle. S As found in the raw sugar industry, the sizes of the basket are 30-in. X18-in., 36-in. x 18-in., 40-in. x 20-in., 40-in. x 24-in., 42-in. X 20-in., 42-in. x 24-in. and 48-in.x24-in.; the thickness of the shell is usually 3,-in. to }-in. The shell is perforated to allow the molasses to pass, the perforations being usually ?-in. to r-in. pitch and about ,%,-in. diameter. These dimensions, of course, vary among the different makers. To give additional strength, the shell is reinforced with circumferential hoops of steel; in a 42-in. machine there are usually eight of these hoops, one inch deep and one- quarter inch wide. The bottom of the basket is usually made horizontal or sloping slightly downwards, with a central opening for the discharge of the dried sugar ; when running this opening is closed by a valve. The lip of the basket is horizontal or slightly sloping upwards ; its duty is to prevent the massecuite from climbing upwards under the action of the — centrifugal force. The width of the lip is about six inches and varies, of course, as among different makers. The contents or charge of the basket is determined by the volume defined by the shell, the lip, and a vertical dropped from the inner edge of the lip. It is the practice, however, to charge the basket while it is already in motion, so that during the process of charging molasses is already being removed, and thus the capacity or charge is in- creased. The screen which serves to retain the crystals is made of perforated copper or brass sheet, or is woven. The perforations may be circular or- elongated conical holes, as first proposed by Gwynne (patent 13577, 1851). The woven material is suitable for very fine sugars, and the perforated for coarse material. The perforations are usually about one-fortieth of an inch, and are spaced twenty to the inch. Between the wall of the basket and the screen is interposed a very coarse woven screen, with mesh at least one- quarter inch, upon which the screen rests. In its absence the perforated THE SEPARATION OF THE CRYSTALS 413 copper or brass sheet would be forced against the inner surface of the shell, sealing its perforations. In the earlier machines the discharge of the sugar was effected by lifting it in scoops over the lip, and the discharge through the bottom of the basket appears for the first time in Weston’s patent, though previously Gordon (2213, of 1867) had patented a machine in which the whole bottom was lowered. Considerable labour is expended in scraping the sugar from the wall of the basket, and to obviate this Sillem (898 of 1858), Green (1332 of 1859) and Merril (1178, 1867) all patented the use of scrapers which were held against the wall of sugar whilst the machine was still revolving. Although patented again by Weston (1937, 1883) as a “ plough”’ in a very practical form, this system does not seem to have come into use till many years later. Fic. 258 Fic. 259 The Roberts-Gibson discharger (patent 5675, I910) is shown in Fig. 258. To avoid damaging the screen, these devices should be used with a renew- able hard wood tip, as was also pointed out by Weston. The self-discharging basket of Watson, Laidlaw & Co., Ltd., is shown in Fig. 259. This is contained in Laidlaw’s patents (4498, 1894 ; 8766, 1895 ; 5750, 1902). In this machine the massecuite is fed on the cone whilst the basket is in motion, at a speed sufficient to project the material against the side. When the massecuite dries, the slope of the wall is insufficient to retain the sugar, even before the basket has come to rest. The Centrifugal Spindle—The spindle shown in Fig. 256, representing very closely the original Weston patent, remained a standard pattern for many years. Certain modifications are mentioned below. Laidlaw’s patent (6081, 1891) introduced the double wedge-shaped buffers, shown also in Fig. 256, which serve to give a more uniformly distributed pressure in different positions of the basket. Later, the buffer assumes a conical 414 CHAPTER XX form in MacFarlane’s patent (10034, 1903), Fig. 260, and is so made as to afford access to the bearing without dismantling the machine. Ball-bearings are claimed generally as applicable to centrifugals in Theissen’s patent (15984, 1899), and they appear in MacFarlane’s patent (19060 of Ig02), and in that of Pott, Cassels, Williamson and Stuart (19069 of 1902), Fig. 261. In both these patents the usual inner solid stationary spindle is made hollow to accommodate a stem fixed at its lower end to the hollow rotating spindle which carries the basket. The step bearing is fitted between the upper ends of the stem and of the stationary spindle in an oil retaining casing. The solid spindle with the compound ball-bearing appears in Pott and Williamson’s patent (8806, 1903), Fig. 262, and in MacFarlane’s patent . Fic, 260 Fic. 261 (25097, 1903), Fag. 263. In the former the end thrust is taken up on the large balls, and the side pull on the journal bearing on the smaller balls: in the latter, the end thrust is taken up on the outer two rows of balls, and the side pull on the two inner rows. With the solid spindle the design reverts very closely to the original suspended centrifugal as designed by Bessemer. A type of spindle employed by the American Tool and Machine Co. is shown in Fzg. 264. It differs from the other designs in employing a ball and socket suspension and in continuing the inner stationary spindle throughout the length of the outer rotating element. Cycle of Operations in a Centrifugal.—In drying sugar the cycle of opera- tions is as follows :—Charging, accelerating, running at full speed, stopping, discharging. Often the charging and accelerating will take place simul- taneously. The complete time of a cycle will depend on the design, especially on the power of the prime mover, and on the nature of the material being . THE SEPARATION OF THE CRYSTALS 415 dried. In sugar-house work the nature of the material varies usually in terms of the “ purity,’’ but between material of the same purity much depends on the skill of the sugar boiler, and on the nature of the impurities. Referring to well-boiled massecuite of 75 purity or thereabouts, the time occupied by the various operations will be approximately :—Charging and accelerating, one minute to two minutes, the time depending on the power available ; running at speed, two to three minutes ; stopping, half a minute; discharg- ing, halfa minute. The cycle, in all, occupies rather less than five minutes, and at least twelve charges should be worked in an hour unless the masse- cuite is badly boiled or unless the molasses is very viscous for reasons outside the executive’s control, as happens when operating on burnt cane. On occasion, however, much greater capacities obtain; with very free masse- cuite and with the operatives stimulated to extraordinary exertion, as many as twenty charges per hour can be obtained, provided there is sufficient ‘a ae he N ai WE Fic. 262 power available to cut down the accelerating period to the lower limit. In installing plant, however, it is seldom safe to calculate for more than eight charges per hour. As regards low massecuites of 55 to60 purity the cycle is quite different, and is almost entirely occupied with running at speed. Fifteen minutes as the over-all time taken for drying one charge is probably below the average, and it is not advisable to reckon on more than three complete cycles to the hour. Methods of driving Centrifugals—The standard method of driving centrifugals is by belts. When the prime mover is a steam engine, the latter is usually found making about 60 to go r.p.m., so that the ratio of gear- ing between engine and machine will be about 1 to 20. The engine usually drives a countershaft, which in turn transmits motion to a second shaft, on which are mounted clutches, one for each machine in the battery. Occa- 416 CHAPTER XX sionally high-speed engines making up to 200 r.p.m. are found. The first mention of electric drive is found in Watt’s patent (2944, 1883) ; but its introduction is largely due to Williamson’s patent (21262, 1896). In this design the field magnets forming the stationary part of the motor are attached to the inner stationary spindle, the armature being connected to the outer rotating spindle. In electric drive, as now carried out, the motor is mounted rigidly, and communication to the rotating spindle is made by a friction clutch or by flexible bearings. Water drive for centrifugals is due to Laidlaw and Matthey (patent 17101 of 1895), who attached a Pelton wheel to the rotating spindle. This method of drive has been very largely adopted. In referring to electric and water drive, it must not be forgotten that SSA Xs comet} II SS IN WOON ‘ QQ EAN SS REM HH HOH gg SS RSs IAINNININ VLZZLLAS 5 6“ iy \ US CALUSTAs FIG, 263 in nearly all cases the steam prime mover stands behind the motor whether electric or water. In this case their principal difference is that in motor drive each machine has its individual motor, whereas with the older system it is a case of group drive from one larger motor. In discussing the centrifugal machine, it is shown that the power used over the cycle varies very largely from a minimum of zero when stopping to a maximum when accelerating. With individual drive, whether electric or fluid pressure, it is necessary to exaggerate the size of the motor to supply ample power during the acceleration, or otherwise to prolong this period unduly, thus cutting down the capacity of the machine. The water-driven machines of Watson, Laidlaw & Co., Ltd., are supplied with two jets, which operate during acceleration, one being automatically shut off when speed is attained. Similarly, the electric-driven machines THE SEPARATION OF THE CRYSTALS 417 are supplied with motors which can develop an excess of power over short intervals. Nevertheless, an individually driven battery is more expensive than one group-driven, and the sum total power of the individual motors will always greatly exceed that of the one larger motor, which need only develop the average power required for a battery, allowing for the time consumed in the five divisions of the cycle. Group drive does not prevent the use of electricity and the centralization of power. The writer inclines to the position that the most generally economical combinations are an electric motor driving a group of machines through the agency of belts or water-driven machines receiving power from a centrifugal pump. Load on a Centrifugal.—If W be the weight of a particle constrained to move in a circle of radius 7 and at a velocity v, the centrifugal force exerted 2 is oe , where g is the acceleration due to gravity. In the case of a machine 42-in. X 24-in., with steel shell ~,-in. thick, perforated with ,%,-in. holes at Z-in. pitch, the value of W for the shell alone is 180 lbs., taking the specific gravity of steelas 7-8. The weight of eight hoops of steel each 1-in. by }-in. will be 75 lbs., to which has to be added that of the backing and perforated strainer, amounting to 15 lbs.; the total of these is thus 270 lbs. At 1,000 : Wr? . r.p.m. the value of v is 183 ft. per sec., so that the value of 5 = is 146,000 lbs. The charge of massecuite will distribute itself in such a manner that its vertical section is a parabola, but with the vertex so distant that it may be considered as a hollow cylinder. The load may be taken as concentrated at the radius of mean position given by the formula a Ki — ko F RI—Re where R, and R, are the outside and inside radii of the hollow cylinder. If R, be 1-75 feet and R, be 1-25 feet, the value of the above expression is very nearly 1-5 feet ; for this radius at 1000 r.p.m. v is 157 ft. per sec. If the charge of masse- cuite be 600 lbs., and if none escape before full speed is reached, the value of 2 as is 308,000 lbs., so that the total load on the shell of the basket is 454,000 Ibs. Deducting the area of the perforations the area of the shell is 3,322 sq. in., so that the pressure per sq. in. is 136 lbs. The resistant cross-section is that due to the shell and to the rings: for the shell it is 8, x 18-6 X 2 = 7 sq. ins. nearly, after allowing for the perforations. For theringsitis8 x 2 X I X 0°25, or 4sq. in., in alla total of11sq.in. The force tending to break the basket is p d/ where p = pressure, d@ = diameter and / = height. Substituting the calculated values pd/ is 136 X 42 X 24, or 137,000 lbs., so that the stress is 137,000 + II or I2,400 Ibs. (54 tons) per sq. in. Force acting on Molasses.—If » be the number of revolutions per sec., r be the radius of gyration in feet, g be the acceleration due to gravity or 47° n?r 32 feet per sec., the centrifugal force acting on a particle is times. that due to gravity. In the case of a 42-in. machine making I,000 r.p.m., 2K 418 CHAPTER XX n will be 16 and ¢ for a particle on the shell of the basket will be 1-75, so that the value of the above expression is 553,1.e., the force at the periphery tending to drive the molasses through the screen is 553 times that due to gravity. Power used in Centrifugals.——The work done on a particle in reaching g 2 speed v is v, where W is the weight of the particle. In the case of the machine considered above, the basket weighing 270 Ibs. attains a speed of 183 ft. per sec. in, say, one minute. The load of 600 lbs. reaches in the same time a speed of 157 feet, and the rest of the machine, spindle, top and bottom of basket, pulley, etc., may be taken as weighing 300 lbs. and acting at a radius of one foot to reach a speed of 105 feet. 2 The value of = for these three items is 505,000 foot-pounds, and the average power developed, neglecting windage and friction, will be 505,000 + 33,000, or 15°3 H.P. Since at the commencement of the operation the power is zero, the maximum power developed, assuming uniform acceleration, will be twice the average or 30:6. This quantity will be reduced if molasses are thrown off during acceleration, as is actually the case. When speed is reached only the power to overcome friction and windage is required, and eventually during the period of slowing down and discharge no power is consumed. Provided the prime motor has sufficient power to keep the machine running at full speed, this speed would eventually be attained, though without an excess of power the period of acceleration may be so prolonged as to cut down the capacity of the battery materially. This point is of importance as regards the choice of drive, and is discussed elsewhere. Some actual results given the writer by Mr. W. G. M. Phillips follow:— A 40-in. X 24-in. machine with motor attached to spindle consumed 45 H.P. when reaching a speed of 1,060 r.p.m. in 70 seconds, falling to 21-5 H.P. when the time to full speed fell to 150 seconds. With eight 40-in. X 24-in. machines and mixer, belt-driven off a motor, the electrical input averaged over a long period and obtained from a recording instrument was 60 kw., corresponding at go per cent. efficiency to 72:5 H.P. delivered to the machines, or to 9:06 H.P. per machine. The sugar produced per hour was 26,650 lbs. Evidently in machines working up low sugars where the acceleration period is only about Io per cent. of the total time of operation, the power required is much less. With smaller machines the power required is roughly proportional to the decreased output, increasing, however, more rapidly than the output decreases, since the dead load carried is greater in proportion with the smaller machines. Further, in installations of fewer machines the power per unit must be increased, since the demand for power will not be so evenly averaged. Centrifugal Speeds.—In discussing centrifugal speeds the distinction between equal speed and equal centrifugal force must be recognised. Evi- dently if D be the diameter of the basket and if N be the revolutions per minute for equal peripheral speed, DN =constant. The equation for equal centrifugal force, however, is DN? = constant, and accordingly as the dia- THE SEPARATION OF THE CRYSTALS he o> meter of the basket increases so also must the peripheral speed, if it is desired to maintain the centrifugal force constant. When the Weston centrifugal first came into use it was designed for 1,440 r.p.m. with reference to a 30-inch machine, which for a number of years was the only size built. But within a few years the makers reduced this speed to 1,200 r.p.m. and the centrifugal force corresponding to this diameter and to this speed remains generally a standard at present. The table below gives the r.p.m. in other sizes required to give an equal peripheral speed, and an equal centrifugal force. EQUIVALENT SPEEDS REFERRED TO I,200 R.P.M. AND 30-INCH MACHINE. EgQuaL PERIPHERAL EgQuaL CENTRIFUGAL Diameter. SPEED. FORCE. inches. Revs. per min. Revs. per min, 30 <= I,200 ae 1,200 36 ae I,000 ds 1,095 40 me goo -- 1,039 42 2: 857 ate I,0I3 48 ~2 750 ae 948 54 Ac 667 a5 894 It also follows that with the larger-sized machines, run at equai centri- fugal force, the stress in the shell of the basket is greater, necessitating either a greater section or the use of materials of higher tensile strength. The relation between speed of rotation and water left in the material has not, the writer believes, been worked out in detail. Reasoning by analogy a law similar to that found by the writer as holding between pressure and quantity of juice extracted on crushing cane (cf. Chapter XI) would probably result. If such be the case great increases in the speed would be accompanied by but small decreases in the quantity of water left in the dried material. The following data on drying yarn made in 1878 have been given to the writer by Mr. A. R. Robertson, of the firm of Watson, Laidlaw & Co., Ltd., and, though incomplete, bear out the ideas put forward above. Diameter | Revs. Time be a ppt seer | Water per of Pe. | Spinning | dry yarn | taken from | ing rb. of machine. | min. min. Ths. machine. | in yarn. dry yarn. | | | 30 inches | 1500 4 60 107 °5 47°5 0-791 305 4575 1500 | 60 107 °25 47°25 0 -787 30nd esos 4 60 105 °5 5.5 0-785 SOT Se | 1500 7 60 105 °25 45°25 0 +754 30 - 2000 4 60 105 °25 45°25 O -704 20s <, 2000 | 4 60 102 42 0-7 BOF as 900 4 120 225 103 °5 o -862 30m 25. goo 7 | 120 222 102 o -850 $6... tis Fae ae 3 Pree 221 IOI o -841 Re | goo | 3 120 229 109 0-908 48 , 720; "| 4 | 180 350 170 0-944 yh eae 900 5 180 342 162 o°9 yt re 900 2 180 342 162 o-”9 wa Se goo 4 180 | 337 ie Sy, 0-816 420 CHAPTER XX These experiments show very clearly that when once a certain limit has been reached prolonged spinning does not further decrease the water content. If the limit to which the water can be removed is reached when the centrifugal force balances the force due to surface tension between the crystal and the liquid, it follows that prolonged duration of rotation will not further decrease the water content after these forces are once balanced. The drainage of molasses from a massecuite in a centrifugal may be considered as a special case of the flow of a liquid through a system of capillary tubes, which are formed by the interstices between the crystals. The equation a p a4 32 pl is the diameter of a tube of length /, # isthe pressure, w is the viscosity, F is the rate of flow andC isaconstant. The pressure acting on the molasses varies as the square of the number of revolutions and hence also does the rate of flow. The time required to expel the molasses should then decrease with the speed and should be accompanied by an increase in the capacity of the machine. for this flow is given by Poiseuille’s law,1 in which F = C xX where @ “s YOO) Fic. 265 Fic. 266 P”? 2” ” 55 ” ” Vs wae Be 14,310 85 oe) ” 2? ” BS) ” ” ee o- ee 49,672 5a) a ” 46 °° ae 10,296 In a preceding section a 40-in. X 24-in. machine was given as handling 80 cu. ft., or 7,200 lbs. containing 6,800 lbs. gravity solids per hour, at 75° purity. A 36-in. x 18-in. machine may be expected to handle 850 lbs. of gravity solids per hour at 55 to 60 purity. THE SEPARATION OF THE CRYSTALS 423 There will then on this basis be required :— Machines. 77 purity 75 purity massecuite we = 4°8 of 4o-in. x 24-in. oo Be ies ee = 16:9 of 36-in. x 18-in. 50 85 ” 75 ” » or = i es of 40-in, x 24-in. (ele) 6 : 55 en » =" = 12-0 of 36-in. X 18-in. 50 As the installation must allow for the maximum at the different condi- tions, the design would resolve itself into six 40-in. x 24-in. machines for high grade and eighteen 36-in. x 18-in. machines for low grade, some mul- tiple of three being taken in this case, since one unit of labour can handle three machines. Alternatively, a design might be offered comprising six 40-in. X 24-in. machines on high-grade and twelve 36-in. x 18-in. machines on low grade, with six 36-in. x 18-in. machines connected to work on either, changes being made dependent on the purity of the material being handled. It is not unusual to express centrifugal capacity as so many square feet of screen area per ton-cane-hour. A 4o-in. X 24-in. machine offers 21-1 sq. ft., and a 36-in. x 18-in. machine 14-1 sq. ft. In this case then there will be 423 sq. ft. in all, and if the roo tons of juice are derived from Io0o tons of cane the proportion is 23 sq. ft. per ton-cane-hour, of which 40 per cent. is used on high grade and 60 per cent. on low grade. Screen area is not, however, an altogether satisfactory basis of comparison except as between machines of the same size, for, whilst the screen area varies as the product of the diameter and height of basket, the capacity varies as the net cubic contents. In any case a flat rate does not form a good system of design, which should be considered in detail for every case with a knowledge of the purities and densities of the juice, as well as of the tonnage of cane to be handled. Handling of Low Sugars.—In the older processes of repeated boilings a quantity of fine-grained molasses sugars of 88 test or thereabouts was ob- tained. This material is of low comparative value, and its marketing is attended with difficulty. The best way to dispose of it is to remelt it or to take it into the pans as seed grain. In the two and three-massecuite processes described in the previous chapter the low sugars are boiled on a footing of high grade massecuite, so that they are of large grain, and if neces- sary can be washed up to g6 test. It is, however, much more convenient to double-cure these sugars. They are accordingly dropped wet from the baskets, mixed with sufficient high-grade molasses to allow of pumping, and mixed with the high-grade massecuite ; alternatively, they may be re- dried separately in independent machines. This process of double purging was first used by G. L. Spencer at Tinguaro, in Cuba, about Igoo. When these low sugars are mixed with high-grade massecuite, a uniform distribution should be obtained. This is best done by running a canal parallel to and over the centrifugal supply tank. Part of the canal is cut away precisely as is done with the ‘“‘ cush cush”’ distributors in use at the mills. 424 CHAPTER XX Centrifugalling for White Sugars.—When plantation white sugars are - made, a more complete removal of the adhering molasses is necessary. This is effected by washing with water and with steam. The water used should be as pure as possible, and the condensed steam available in every factory forms a suitable supply after cooling. Before the steam is allowed to act Wasnés Ovrier Fic. 267 on the wail of sugar it should be freed from water by being passed through a separator.% With high-grade massecuites the quantity of water used for washing is about thirty lbs. in a 4o-in. centrifugal, or 1 lb. to Io Ibs. of sugar. The quantity of steam used is about 1 lb. to 5 lbs. of sugar. With lower grade massecuites boiled from first molasses these quantities are doubled. Fic. 268 When following this method the water and steam runnings are of very high purity, and it is expedient to separate them from the first runnings and to return them separately to the high-grade product. This process is known as the classification of molasses, and the scheme was first suggested by Perier in the European beet sugar industry in 1852. Donner’s patent THE SEPARATION OF THE CRYSTALS 425 (3553 of 1874) specifies the use of two gutters and of a casing, interior to the curb or usual outer casing, and capable of being raised in a vertical plane. Material caught on this casing is delivered to one gutter, that intercepted by the curb when the interior casing is raised passing to the other gutter. This principle is contained in various later patents, that of Patterson (22384 of 1897) being indicated in Fig. 267. The use of individual gutters alone appears in patent 11842 of 1897, Fig. 268, granted to Lubinski and Krajewski, Fic. 269 but, the absence of a second surface to receive the purer runnings leads to an imperfect separation. In Matthewwissen’s patent (24993, Ig0I) vanes are formed in the curb, and the direction of rotation of the basket is changed when washing begins, the flow of the molasses being directed to independent gutters by the vanes. MacFarlane’s patent (26716, 1902) employs an imperforate cone-shaped basket separated from the screen. The molasses projected on to the inner wall drain off vertically, and are directed into one of two gutters according to the position of a cylindrical screen, the arrangement of which is adjusted by the operator. Another more complete and preferable scheme is that of double curing. 426 CHAPTER XX In this scheme the molasses are expelled in the first set of machines, the sugar being dropped without any washing. It is then made up to a magma with purging syrup and redried or affined in a second set of machines. In the first operation the sugar from the first drying is made up to a magma with water, and the resulting ‘‘ molasses”? forms the purging syrup used in subsequent operations, circulating continuously ; the excess as it accumu- lates is boiled into first product, or it may be returned to thin juice, since, being of very high density, it is not advisable to introduce it direct to the pan without dilution. The second quality white sugar may be treated in a FIG. 270 similar way, or after mixing with first molasses it may be dried along with the first massecuite, the factory then producing only one grade of white sugar. The great advantage of double curing lies in the complete classifica- tion of the molasses which it affords. When calculating the number of centrifugals required for white sugar manufacture, only half the capacity of that accepted for 96 test should be taken, so as to allow for the extra time consumed in washing with water and steam. If steam washing is dispensed with in favour of a sugar dryer, this extra allowance may be decreased. If double curing be installed, FIG. 271 either set should have the same capacity as would be employed with 96 test sugar. Conveyance of Sugar.—Occasionally the dried sugar is discharged direct from the machines into bags, but it is usually conveyed to an upper floor or bagging bin by means of an elevator of the type shown in Fig. 269. The erystals are carried from the machines to this elevator by a screw conveyor, as indicated in Fig. 270, or by a ‘‘ grasshopper ”’ conveyor, Fig. 271. This consists of a suspended trough, which is supported on flexible inclined blades, and to which a to-and-fro motion is transmitted by means of an eccentric. THE SEPARATION OF THE CRYSTALS 427 The Continuous Centrifugal.—A number of inventors have attempted to develop machines which will operate continuously and avoid the time and power lost in starting and stopping and in charging and discharging. No great success has been obtained so far, but the principles applied are :— x. A horizontal machine, in which rotates a screw moving at a slightly lower speed than the basket, whereby the material is propelled forward and discharged dry at the end of the machine remote from the inlet. This idea is contained in Aspinall’s patent (1196, 1855), and has been in particular developed by Stewart (6931, 1884, and 13655, 1888). 2. A fluid introduced into a rapidly rotating vertical cylinder will tend to rise against gravity, precisely as is observed in the ordinary machine. This tendency may be assisted by maintaining communication with the incoming material by defining a passage for its motion. In such a scheme it is intended that the dried material should eventually discharge itself over the lip of the basket. This device is included in Bessemer’s patent (13202, 1850), in Aspinall’s (2833 of 1855), and in several later ones. 3. If the shell of the ordinary machine be removed or opened when the basket is at speed the wall of dried sugar will be expelled. This idea is developed in patents 13846, 1851, and 1433 of 1854, and by Abel, 22900 of 1905. 4. Another patent, also due to Abel (14736 of 1889) places a number of baskets inside the main basket and located around its periphery. These baskets rotate with the machine and simultaneously about their own axes. They are divided into compartments by radial partitions, and located about the centre of each basket is a cone. Massecuite is fed into the cone and thrown into those compartments furthest from the axis of the main basket, whence the molasses is expelled by the usual action. As the baskets rotate about their axes each compartment in turn will arrive at a position when the wall of the basket lies between the sugar contained therein and the axis of rotation of the main basket. In this position the sugar is thrown out against the outer side of the cone and falls into a funnel-shaped receptacle, which directs it to the conveyor. REFERENCE IN CHAPTER XX. eg Oats, p LOM 0248 LO TAs CHAPTER XXI Raw SUGAR By raw sugar the writer understands a material prepared directly from the plant juice, and without any intermediate process of remelting or refining. Under this definition white plantation sugars of very high purity would be classed as raws, whilst the “ softs’ or “‘ yellow” sugars of the refinery of very much lower purity would rank as refined. A recent publication of the U.S. Bureau of Commerce however adopts an opposite view, and defines refined sugar as “‘ chemically pure”’ sucrose ; if the term ‘‘ chemically pure” be accepted within narrow limits a cane sugar-house specialising in plantation white would become a refinery, and the ‘‘softs”’ and “yellows”’ produced by what is generally accepted as a refinery would be classified as raw sugars. In the very early days of sugar manufacture the product was cane juice concentrated nearly to dryness and known in India as “ gur,”’ the name being derived from the Sanskrit gul or gud, a ball, and relating to the form in which such sugar appeared on the market. With increased skill there appeared a material in small crystals called sarkara, originally meaning gravel, and a material in larger crystals called khanda, the word denoting a piece. From these terms descend the words sugar and candy. Another Indian term, jaggery (a corruption of sarkara), appears to connote a date-palm raw sugar. The ancient Indian market also recognized (and as a folk custom continues to recognize) Cairene or Egyptian sugar (misv1) as a superior article, the antithesis being China sugar known as chimi. To the white refined sugar originally produced in Persia the name tabaschir was given, originally denoting a white siliceous product found in bamboos. In the old New World industry, two main classes of sugars were made, muscovado* and clayed sugar. The former was a crystallized product from which some of the adhering molasses had been removed by drainage; in the latter a less imperfect separation had been obtained by allowing a sus- pension of clay and water to percolate through the mass. Another term appearing in early days is cassonade, primarily implying a sugar shipped in chests. One form of cassonade was powdered clayed loaf shipped to France in this form so as to avoid a higher customs duty. Elsewhere, the term seems to be applied to an inferior type of raw sugar. New processes introduced new expressions and thus arose the terms Vacuum Pan Sugars as opposed to Common Process Sugars, Centrifugals as opposed to sugars dried by drainage, and Concrete Sugars in which no drain- age occurred at all. Sugars were once, and to a certain extent still are, classed according to the Dutch Standard. In this scheme, 25 D.S. (as it is abreviated) was a * The best authorities derive this term from the Spanish, menoscabo, implying damage and the idea of inferior- ty, and derived from menws, little, and acabar, to finish. Acabar appears in French as achéver, whence the transition to méchet and the English mischief is easily seen. A second derivation may be through the Low Latin muscum meaning musk (whence is derived muscatel) and correlating with the pleasant smell and taste of raw sugar; the Italian term musciatto certainly seems very far from menoscabo. The derivation sometimes found from mas, more, and acabodo, finished, i.e., the process carried beyond the syrup stage, seems fantastic. 428 — ee oe ere a. RAW SUGAR 429 sugar nearly white, the opposite end of the scale being 6 D.S., representing the darkest sugars appearing in commerce. Formerly in the U.S. market, sugars above 12 D.S. were considered as refined, and paid a higher duty. The raw sugars intended for refiners’ use have received various and some- what confusing trade appellations. In the United States market, the great bulk of the supplies come from Cuba, Porto Rico and Hawaii. These sugars are sold on a basis of 96 degrees polarization, and are very commonly called Centrifugals. Other terms are 96 Test Crystals, Dark Crystals, and Refining Crystals. The Java producers make two classes of refining crystals. One, 16 Dutch standard and higher, polarizes about 98 and contains about 0-5 invert sugar, 0:25 ash, 0-5 water and 0-75 organic non-sugar. This type of sugar is known also as Channel Assortment or European Assortment. The other type lies in colour between 12 and 16 D.S., and polarizes about 96. Itisknownas American Assortment, andin Java as Muscovado. Else- where muscovado is used to indicate a sugar similar to the original mus- covado and synonymous with the terms “ open kettle,” ‘‘ common process.” Other low-grade sugars appear under self-explanatory terms, such as Molasses Sugars, Stroop Sugars, Sack Sugars, Philippine Mats, Concrete. In Latin America these low-grade sugars have numerous names such as Pilon, Piloncillo, Dulce, Panela, Panoche and Raspadura. Raw sugars were formerly classed as first, second, etc., a first sugar being boiled from juice, a second from first molasses, and so on. With improved methods of operating calling for the return of molasses to process, this classification is no longer available. Direct consumption raw sugars fall into two classes, white and yellow. Java, Mauritius, Egypt, Natal, Brazil and Argentina produce large quan- tities of plantation white sugar for local and near-by accessible markets. The Java market recognizes three grades :—1. Superior hoofdsuiker (head sugar) of nearly 100° test and 25 D.S. This is boiled from juice only. 2. Superior stroopsuiker (molasses sugar), boiled from the runnings from the first class, with or without admixture with first product. This material is sold moist and contains about 0-4 per cent. of water. 3. Hoofdsuiker of 18 D.S. up to 25 D.S., a material similar to the first-named, but of lower quality. In Mauritius two qualities, vesow (juice) sugar and premiére sirop, only are recognized. Yellow sugars, known as Demerara crystals, yellow clarified or grocery sugars, are mainly made in Demerara for the London and_ in Louisiana for the local market. All the above sugars are sold on appear- ance only. The peculiar flavour of these raw sugars, which adds much to their value, has been attributed to the formation of bodies formed by the interaction of amides and reducing sugars in the process of manufacture, and in addition account must also be taken of the presence of essential oils which may also be present in the cane. The validity of the use of the term “ Demerara” to raw yellow cane sugars made elsewhere has been challenged, but in the British courts it has been decided that the term has no peculiar geographical significance, and applies to the process and not to the locality. Dyed sugar crystals, whether of beet or cane origin, stand on a different footing altogether, and the sub- stitution of these for a raw cane product is an evident fraud. A more difficult situation arises regarding materials boiled in refineries from imported remelted material. A criterion might be established with reference to their passage or not over char, a process which will remove those bodies to which the peculiar characteristics are due. An attempt to give to beet 430 CHAPTER XXI crystals the peculiar flavour of cane products is seen in Bensen’s patent (225 of 1866), which proposes to mix the former with cane molasses. More lately this idea was revived by Winter, who has proposed to use invert sugar syrups which have been exposed to the action of alkalies. The Composition of Raw Sugar.—Raw sugar, whether a consumption sugar or one designed for remelting and refining, may be considered as consisting of a crystal of nearly pure sucrose coated with a film of molasses. The quantity of molasses adhering to the crystal will depend on the surface area of the crystal, the viscosity of the molasses, and the speed of rotation of the centrifugals in which the sugars are dried. The composition of a typical raw sugar as conceived as consisting of crystal and molasses may be readily obtained. If, for example, molasses contain 20 per cent. water, the per- centage of water in the sugar multiplied by 5 will give the percentage of molasses. At the moment of discharge from the basket 96 test sugars of average size of grain, and under the usual conditions of manufacture, will be found to contain about 1-25 per cent. water, whence the percentage of molasses is 6-25 per cent. and of crystals 93-75 per cent. If this molasses polarizes 36, the polarization of the sugar will be 93°75 + 0:0625 X 36 = g6-0. Such a sugar would be obtained from a massecuite of 75 purity, and such a sugar is typical of a very great proportion of those that are offered for sale to the refiners. After discharge from the basket, sugars of this class will generally be found to lose water and they arrive at the port of destination with but little over I per cent. of water. The actual quantity of water present when melted will depend, of course, on atmospheric and storage conditions at the location of origin, in transit, and at the point of delivery. Accepting a raw sugar as constituted of crystal and molasses in fairly constant proportion, its polarization will be dependent on the composition of the molasses, and since (vide Chapter XIX) the percentage of sugar in a molasses increases as the purity of the magma whence crystallized increases, the polarization of the sugar will also increase. Thus from a massecuite of 85 purity molasses polarizing 50 may be expected, and if the sugar still contains 6-25 per cent. of molasses the polarization of the sugar will, at the moment it is dropped from the centrifugal, be 93-75 ++ 0-0625 X 50 = 96-875. The differences found between sugars obtained from high and low purity massecuites will, however, be rather larger than indicated by cal- culation, since the molasses of high purity being less viscous are less incom- pletely removed from the crystal. On the other hand, as the purity of the massecuite falls, so also does the purity of the molasses, and when the sugars are crystallized from massecuites of very low purity the polarization of the sugar falls. In this case, however, there is another factor at work. Such sugars have a very small crystal, and hence the surface area of the crystals is very large, indicating a very large retention of molasses. The sugars obtained from massecuites of about 50 purity boiled blank normally contain about 5 per cent. of water, indicating the presence of 25 per cent. of molasses. If the molasses polarizes 30, the polarization of such a sugar will be 75 + 0-25 X 30 = 82-5, anormal figure for such material. Sugars of this class are, however, of minor interest, since their production tends to become less and less as improved methods of manufacture become more common. The above argument does not take into consideration one point of interest RAW SUGAR 431 in that it assumes the crystals are puresugar. In every case some adsorption of non-sugar occurs, and this adsorption is greater as the purity of the mother liquor falls. In certain cases the presence of non-sugar may modify the shape of the crystal, and in some cases at least—with sodium chloride—a definite molecular compound of sugar and salt crystallizes. The conclusions to be drawn from the above argument may be modified in two ways in actual practice. The manufacturer may dry his sugar after it leaves the centrifugals ; such an operation, while appreciably raising the polarization and diminishing the water content, will leave the value of the other constituents appreciably unaltered within the limits of the ordinary analysis. In the second case the adhering molasses may be removed in whole or in part by washing with water, whereby raw sugars of high polariza- tion may be obtained from low purity massecuites. Such sugars can be obtained with a very low water content owing to the dilution of the molasses and consequent decrease in the viscosity. Finally, as regards the sugar on its arrival at port of destination, further disturbance, due to the action of micro-organisms, may have occurred through inversion of sugar, and the destruction of inverted sugar thus formed and of that originally present. The non-sugar present in raw sugars is derived principally from the non- sugar in the juice and its composition is modified by the manufacturing process under the following heads: 1. Phosphates and albuminoids are precipitated. 2. Non-sugars are added, as lime and occasionally as sul- phurous acid and phosphoric acid. 3. Sugar may be caramelized or inverted nto reducing sugars, and reducing sugars may be broken down by the action of heat and lime appearing as organic lime salts. 4. Mineral matter may be precipitated as scale on concentration. 5. On storage reducing sugars may be both formed from cane sugar, and reducing sugars thus formed and those originally present may be destroyed by the action of micro-organisms. It is customary in analysis to report reducing sugars, ash, and organic non- sugar, the last-named as obtained by difference. Owing to the variation in the amounts of these substances originally present and to the alterations in manufacture, it is impossible to give any definite composition for the non-sugar, but it will be found that in the great majority of cases the ash is present in less than half the quantity of either the reducing sugars or organic non-sugar, and that these are present in quantities of the same order. A typical 96 test made from a 75 purity massecuite not washed or subsequently dried will contain from 0-4 to 0-7 per cent. ash and from I to 1-5 per cent. of both reducing sugars and organic non-sugar. Taking this sugar as typical, the composition of sugars obtained from massecuites of higher and lower purity and of washed sugars can be calculated. The following generalities are, however, allowable :— 1. Sugars made from heavily fertilized canes will contain a larger pro- portion of ash. 2. Sugars made from exceptionally ripe and pure canes will contain a small proportion of reducing sugars. Both the influences mentioned above are to be observed in Hawaiian sugars. 3. In sugars made from low grade material, especially from massecuites boiled blank and cooled at rest, the proportion of reducing sugars tends to increase, due to an increase in the reducing sugars following on inversion of cane sugar. 432 CHAPTER: X2XI The largest constituent present in the ash of a cane sugar is potash. The other bases present are lime and magnesia, with traces of iron. The acids with which these are combined are organic acids (appearing in the ash as carbonate) sulphuric, silicic, and phosphoric. Chlorides are also very often — present. From inspection of a large number of analyses the following may be given as the limits in which these occur :— Potash 40 to 50 per cent. ; lime, 3 to Io per cent. ; magnesia, I to 5 per cent. ; soda, o to I per cent. ; carbonic acid, 5 to 20 per cent.; sulphuric acid, 4 to 15 per cent. ; silicic acid, I to 5 per cent. ; phosphoric acid, 0 to 2 per cent. ; chlorine, 5 to 20 per cent. The actual composition of the ash will be influenced by conditions of soil, manuring and variety and by the maturity at harvesting. Of the organic non-sugar, but little is known; as calculated from the composition of molasses a typical 96 test sugar will contain from 0:05 to 0-2 per cent. of gums (or alcoholic precipitate) ; from 0-or to 0-05 per cent. of nitrogen, much of which is present as amide, very great variation being ob- served as between different analyses. Calculated from carbonic acid in the ash the organic acids may be estimated as from 0:05 to 0-2 per cent. In the balance, which is more than half of the organic non-sugar, will be found caramel, all the bodies of unknown constitution and varying quantities of suspended matter derived from cane fibre. The Physical Characteristics of Raw Sugar.—The physical characteristics of a raw sugar that have influence in determining its value are the amount of insoluble matter, the size and the regularity of the grain, the hardness of the grain, and the nucleus of the crystal. The quantity of suspended matter depends on the efficiency of the defecation process, and what insoluble matter is present is due to suspended particles carried through the processes. It consists very largely of particles of cane fibre. The quantity present in raw sugars of 96 test made by a process of defecation without bulk filtration will vary between the limit of 0-02 to 0-2 per cent., with an average of about O-I per cent. The size of the grain varies from a maximum of over 2 mm. side to a minimum of less than 0:5 m.m., but in any one sample grains of all sizes will be found with a very different distribution of crystals classed as large, medium and small. The hardness of a sugar is doubtless a misnomer, since it is probable that all crystals as individuals are equally hard. What is indicated by the term is rather friability. A sugar composed of small crystals cemented together by molasses will be easily crushed between the fingers and will appear soft to the touch, while one consisting of large individual crystals will appear hard under a similar test. By the nucleus of the crystal is indicated a difference in the method used to form grain. Generally, the grain is formed directly from the syrup, but in other cases low grade sugars of small grain are used as seed. In the latter case an impure material is contained in the interior of the crystal. The colour of the sugar refers to both the colour of the dry sugar and to the colour in solution. It is evident that the colour will be correlated to the quantity of molasses adhering to the crystal. What colour is actually present may be due to the natural colouring matter of the cane, or may have been developed in the process of manufacture by the action of heat-giving caramel or by the combined action of heat and lime on the reducing sugars. RAW SUGAR 433 The last two classes of colouring matter are objectionable to the refiner as resistant to the action of bonechar. All these characteristics are of more interest to the refiner than to the producer. The former is benefited by the absence of insoluble matter, by a large and regular grain with the absence of nests of crystals cemented together by molasses, by a nucleus formed from syrup and not from seed grain, and by little colour, especially that formed by overheating or by the breaking down of reducing sugars. Sugar Drying.—In the manufacture of white sugar the crystals are dried after they are discharged from the machine. The apparatus usually employed for this purpose consists of a long inclined drum, Fig. 272, which is caused to rotate about its axis at a speed of about 12 revolutions per minute. At- tached to the inner periphery of the drum are a series of paddles, which serve both to carry the sugar forward and at the same time to throw it down in a shower as each paddle in turn reaches the upper point in its revolution. A current of hot air is drawn through the drum in a direction counter to the travel of the sugar. The air enters at about 180° F. and leaves at about FIG. 272 130° F., while the sugar remains in the drum about twenty minutes. The heating surface consists of an external system of steam-heated pipes, an allowance of 75 sq. ft. per ton-sugar-hour being usually found. These dryers are often made in pairs, the second one dispensing with hot air but being provided with an interior steam-heated drum. Sometimes the drum and hot-air system are combined in one unit, but in this combination there is a tendency for wet sugar to cake on the drum. Quite irrationally this apparatus is frequently called a granulator. In some houses it is not unusual to use simpler means for removing some part of the water. These means may take the place of one or more tables caused to rotate rapidly in a horizontal plane. These are arranged in the bin in which the sugar is discharged, and by the exposure of a large area permit of the removal of some of the water. In Java it was, and perhaps still is, the custom to dry the sugar by exposure on the flat roofs of the factories. Drying of sugars, though of great benefit to the producer of raw sugar, is but little practised. The advantages to the latter are discussed in detail in a following section. To these benefits must be added the protection afforded against deterioration, since it has been conclusively shown that a concentrated film of molasses forms a medium in which the activity of micro- organisms is suspended. 2G 434 CHAPTER XXI The Deterioration of Raw Sugar.—Raw sugar when kept under certain conditions loses in polarization. This process, which annually causes the loss of large sums of money, is known as “ deterioration.” Possibly the earliest reference to this matter is due to Ligon, (1673), who writes :— “Sugar should be kept drie in good casks, that no wet or moist aire enter.”’ It is now definitely established that the deterioration of sugar in storage is due to the action of micro-organisms combined with conditions suitable for their growth. The first observation connecting cause and effect is due to van Dijk and van Beek,? who in 1829 published the results of an investi- gation on the cause of the blackening of loaf sugar in an Amsterdam refinery. They determined the cause as due to the presence of a mould Conferva mucorotdes, and the source of infection as the troughs in which the implements were washed. Later, Payen® examined a similar phenomenon in a Paris refinery, identifying as the cause moulds described as Glyctphila erythrospora and G. elzospora. As regards the deterioration of raw sugar in bulk, Dubrunfaut* in 1869 identified micro-organisms as the cause, ascribing the damage to the lactic ferment. He was followed by Gayon® in 1880, who observed yeasts, torule and moulds in deteriorating West Indian sugars, and who also isolated therefrom an invertase. In the cane sugar industry proper, the first observation is that of Maxwell,® who in 1896 in Louisiana ascribed the damage to the lactic and butyric acid ferments. Shorey’ in 1898 in Hawaii found evidence that the damage was due to a species of Pentcillium, and attributed the infection to the air drawn through the sugar in the centrifugals. Kammerling® in 1899 in Java, in a study of the flora of Javan sugars, found Penicillium, Aspergillus, Sterigmatocystis, Citromyces and also Monilia and Torule. He believed that the bags were the source of infection, that the hyphomycete or moulds caused the initial damage, torule and monilia becoming active only after the sugars had absorbed water. Greig-Smith and Steele® in 1903 in Australia found one dominant organism in sugars of cosmopolitan origin, and to this they gave the name Bacillus levantformans. Lewton-Brain and Deerr?® in 1907 in Hawaii isolated from Hawaiian sugars five species of bacteria, all of which were capable of causing deteriora- tion in sugars under favourable conditions. Owen! in Igii in Louisiana isolated from sugars a number of bacteria which he identified as belonging to the Mesentericus group. In particular, he found B. mesentericus, B. mesentericus ruber and B. vulgatus. Browne,!? in examining Cuban sugars in New York in 1918, found that the commonest micro-organisms present were a torula, two species of monilia and a bacterium. Penicillium and Oidium were also present. Owen,?® in later work, found, as well as bacteria, yeasts and moulds, the identified forms being all Aspergillus, one of which was superficially similar to Pemt- cillium glaucum. In the beet sugar industry, similar observations have been made, mainly by Lexa! and by Schone,!® who have found the same classes of organisms as those mentioned above. The foregoing observations of different investigators are not contra- dictory amongst each other ; the absence of torule from one set of deteriorating sugars where bacteria were present does not imply that torulz Ps " ne i RAW SUGAR 435 are not an active agent in the deterioration of other sugars. In addition, all these experimenters have shown by carefully controlled experiments that each and all of the micro-organisms mentioned can and do cause damage under favourable conditions. At one time, however, following on the opinions of Greig-Smith, Lewton-Brain, Deerr, and the earlier work of Owen, there was a tendency to ascribe the damage almost exclusively to bacteria, and their position still remains one of great interest. As shown by Owen, all the forms observed belong to the group known by the earlier bacteriologists as the “ potato bacilli,” or those forms that appear spontaneously on slices of potato left exposed to a damp atmosphere. These bacteria are of wide distribution and in the economy of nature are concerned with the destruction of organic matter. Their natural habitat is the soil, and they are capable of living on media very deficient in nitrogen. They are thermophilous, and many species produce large quantities of gums and slime. They are continually being introduced into the factory along with the cane. The torule and the moulds are also of wide and frequent distribution. Their presence in the factory is probably due to air-borne infection, though torulz can also be found on the rind of the cane. Owen’s later work, however (with which that of Browne and of Kopeloff,1* who very recently has devoted great attention to the moulds, is concordant), attributes the damage chiefly to moulds. He shows that Aspergillus secretes an enzyme of great inverting power; that it is capable of functioning in greater concentration than either yeasts or bacteria, and that it is less susceptible to alkalinity and acidity than are the other two forms. He believes that the inversion of the cane sugar is due mainly to the moulds, which also destroy the reducing sugars thus formed, this action taking place in even the drier sugars. The yeasts, after some absorption of water, ferment the reducing sugars originally present and those formed by the moulds, but have but little invertive action. Finally the bacteria come into activity only when the sugars have absorbed more water still. His conclusions therefore tend to confirm the earlier observations of Shorey and of Kammerling. The factors which influence the growth of all of these organisms are mainly temperature, and the concentration of the film of molasses that forms their habitat. Generally the optimum temperature for the growth of micro- organisms is from 35° to 40°C., and Arrhenius?’ in particular has shown that the rate of change produced by micro-organisms follows the same dynamical laws as do “ chemical reactions.”’ In this connection Browne has showr that deterioration is almost inhibited at 20° C., and becomes noticeable as the temperature rises. Micro-organisms generally, though there are some exceptions, are unable to develop in very concentrated solutions, due to the phenomenon known as plasmolysis, and therefore a supersaturated film of molasses will act to some degree asa preventive of deterioration. Browne!” observed that certain Moniliz which he isolated from Cuban sugars were active in concentrations up to 64° Brix, whilst on the other handa bacterium he studied was inactive at this concentration. Previously Ashby!® haa isolated a yeast from a Jamaican molasses that was active up to a concen- tration of 80° Brix, and Owen observed that while the bacteria he studied were inactive at 60° Brix, Tortule were still active at 64° Brix, and moulds at 69° Brix. In their study of Hawaiian sugars, Deerr and Norris!® found that 96 test sugars did not deteriorate on storage when the percentage of water did not rise above I per cent. ; this was found to be the case, however much 436 CHAPTER XXI the sugars were infected artificially. This limit is evidently connected with the quantity of molasses adhering to the crystal and with the water in the molasses, and is not to be considered as an absolute limit. If, in the sugar they examined, the quantity of adhering molasses were halved and the per- centage of water in the molasses doubled, the water in the sugar wouldremain the same, but the film of molasses would now form a very suitable habitat for the growth of bacteria. Similarly, a sugar of lower grade containing much more molasses will have a much greater percentage of water while still maintaining so concentrated a solution that micro-organic activity is inhibited. These conditions have been combined into a “ factor of safety,” due to the Colonial Sugar Refining Co. of Australia. This may be expressed : t Witter oes 100 —pol. critically examined by Browne,!? who, in one series found that sugars with a factor lying between 0-313 and 0-346 deteriorated, while others with a factor lying between 0-253 and 0-28g did not deteriorate. The exact value of the factor is evidently connected with the concentration at which activity begins, and a different factor will obtain dependent on whether the organisms present are bacteria, yeasts, or moulds. Another point developed by Browne!” is that when sugars deteriorate in a sealed container the factor must decrease until the safety point is reached, and experimentally he has found that this is the case. A cessation of activity may also be due to a toxic action exerted by the products of decomposition. In warehouses, however, conditions are different and the decomposition products are free to escape and the sugars may absorb water. The prevention of deterioration is based on the following points :— I. One class of organisms to which deterioration is due enters with the cane. These organisms are not destroyed in the ordinary process of manu- facture. The temperature and period of exposure in a pre-evaporator as usually operated is, however, just sufficient to cause their destruction. Thus Deerr?® found that certain very destructive bacteria common in Hawaiian sugars were destroyed by 20 minutes’ exposure at 110° C., in 10 minutes at 115° C., and almost instantaneously at 125° C. 2. Avoid washing in the centrifugals in order not to dilute the film of molasses, but, if washing is necessary, use aseptic water. Every factory has a surplus supply of condensed water which is organically pure. 3. Concentrate the film of molasses by passing the sugar through a dryer. As generally operated, the temperature and period of exposure, while not sufficient to give a sterile sugar, will concentrate the film so that the safety limit is reached. Also, as Owen has shown, the dangerous Aspergillus is very largely destroyed in the process. 4. Avoid processes which tend to form hygroscopic substances in the juice. Such are the use of an excess of lime, especially in the presence of much reducing sugar, whereby hygroscopic lime-glucose decomposition bodies are formed. 5. Produce large-grained sugars, since in these the surface area is a minimum and the water absorbed in wet weather is consequently small. 6. Construct tight warehouses and open the doors only in. dry weather. Provide means for ventilation in the warehouses so that the temperature may be controlled. Raise the floor of the warehouse two or three feet above the ground level, and keep the surroundings well drained. <0:333, the sugar will not deteriorate. This factor has been 0 —E— ee app eh RAW SUGAR 437 7. If a cooling tower or distillery is operated, place these to leeward of the factory so as to avoid air-borne infection of the sugars and juice. 8. Keep all containers and the whole factory as clean as possible, pre- venting not only infection but also the evolution of a virulent strain of organisms, since Owen?* has shown that this occurs when the forms respon- sible have a continuous habitat. Aseptic conditions should be particularly maintained at and near the centrifugals, since Kopeloff!® has shown that generally the floors and immediate surroundings are foci of infection, whence the organisms can be drawn into the centrifugal basket by a current of air, as was first suggested by Shorey.’ g. If it were possible to do so, cold storage below 20°C. would eliminate destruction due to micro-organisms. Conversely in Java, when during the Great War large quantities of sugar were stored, the warehouses were kept as hot as possible, with the object of drying the sugars and concentrating the film of molasses. In the great majority of cases where sugars are attacked by micro- organisms a fall in polarization occurs. Exceptionally, instances are found where a rise in polarization results. This phenomenon is due to a selective action of the micro-organisms towards reducing sugars, the cane sugar itself not being attacked. This observation was first made by Watts and Tem- pany,”! and has also been observed by Deerr and Norris,!®° and by Browne.?* The last-named has suggested that the occasional appearance of a sugar with a sucrose content lower than the polarization may be due to the destruc- tion of the fructose due to a selective action of certain micro-organisms. The Valuation of Raw Sugars.—In the American market raw sugars are valued on a polarimeter test alone, the basis being a direct polarization of 96°. The value to the refiner is, however, also governed by the physical char- acteristics and by the purity, as is discussed in other sections. In other countries other methods of valuation are in use, and include special methods of analysis, which are briefly indicated in this section. In 1863 Monnier”? introduced a method for the valuation of sugars based on the supposition that the quantity of sugar retained in the molasses was proportional to the ash content of the sugars. In his method a sugar was estimated to yield the polarization less five times the ash content, and in- cluded in this formula are all the mechanical and other sources of loss. This formula was accepted as a basis of sale between refiners and producers. At various times other formule have been in use. Thus one due to Pagnoul*?? deducted four times the ash, twice the reducing sugars and allowed a manufacturing loss of I-5 per cent. Another formula deducted five times the ash and the reducing sugars. Scheibler** proposed to obtain the rendement by deducting four times the organic non-sugar, but this proposal was never adopted. Stammer and Weiler** were the first to propose the use of the total non- sugar, and at present in Germany sugars are valued on the basis of polariza- tion less 2-25 times the non-sugar. It is evident that this is the same as a sale on a purity basis with a purity in the molasses of I + (2:25 + 1) or 30-8, and neglects the specific effect of the various substances present in the non-sugar. These formule should be read in connection with Geerligs’ theory of molasses formation (see Chapter XXII). The purchase of sugars on a purity basis is discussed in a subsequent section. The second method determines the actual crystal content of a raw sugar, 438 CHAPTER XXI and all these methods descend from the process proposed by Payen in 1846. A summary of these methods is appended. Payen’s Method.24—The raw sugar is washed free from the adhering molasses with a saturated solution of sugar in 88 per cent. alcohol, con- taining also 50c.c. acetic acid per litre. After the removal of the molasses, the remaining crystals are dried, the loss in weight giving data to calculate the quantity of adhering wash liquor, after which the weight of crystals can be calculated. Scheibler’s Method.2®—Four solutions are used. (1) 85 per cent. alcohol saturated with sugar and containing 50 c.c. of acetic acid per litre. (2) 92 per cent. alcohol as in (I). (3) 96 per cent. alcohol as in (1). (4) Two volumes of absolute alcohol and 1 volume of ether. The raw sugar is washed with solutions 4, 3, 2, I, in the order named, the washing with (1) being continued until the washings are colourless. The process is then reversed, and the purified crystals are washed with solutions 2, 3, 4, in the order named, so as to remove the adhering wash liquor. Finally, the residue of. pure crystals. is brought into solution and polarized. | Koydl’s Method.2®’—Five solutions are used. (1) 82 per cent. alcohol with 50 c.c. acetic acid per litre. (2) 85 per cent. alcohol with 25 c.c. acetic acid per litre. (3) 91 per cent. alcohol. (4) 96 per cent. alcohol. (5) Abso- lute alcohol. Solutions r to 4 are saturated with sugar. In making the determination 50 grams of the sugar are washed on a weighed filter paper with 250 c.c. of solution (1), followed by. washings with 50 c.c. each of solu- tions 2, 3, and 4, and finally by 100 c.c. of 5. The residue of crystals is then dried to constant weight. Herzfeld-Zimmermann Method.?7—In this process the raw sugar is washed with a solution of sugar saturated at the temperature of observation. After removal of the adhering molasses, the major portion of the wash liquor is removed by centrifugalling, the residue is weighed and finally dried to con- stant weight, whence is calculated the weight of crystals when the proportion of sugar to water in the wash liquor is known. All these methods assume that the crystals in a raw sugar represent the refined sugar capable of extraction. If the adhering molasses is not ex- hausted, some sugar is capable of being obtained therefrom ; and, accordingly, sugars of the same crystal content need not necessarily have the same re- fining value. The methods would also be inapplicable to sugars boiled on seed grain. The Refiner and the Producer.—In the following section is given an algebraical representation of the relations between refiner and producer, considered from the financial standpoint. The Amount of Raw Sugar obtainable from a Given Juice as determined by its Composition.—lIf s, 7, and m have the significance given to them in Chapter X XVII, then, per unit of sucrose in the raw juice, the sucrose in a raw sugar of purity s obtained from a juice of purity 7, affording waste molasses of purity m, is given by the expression Pet If s changes to s, the sucrose obtained is 1 Sm) j (s —m)' Whence it follows that :— webs RAW SUGAR 439 Sucrose in sugar of s, purity s,(7 —m) 7 (s—m) _ s, (s — m) Sucrose in sugar of s purity 7 (s, —m) “s(j —m) — s (sy — my)" That is to say, the relative quantities of sucrose obtained in raw sugars of different purities depend only on the purity of the sugar and not.on the purity of the juice whence they are obtained. Now let a definite value be given to m, say, 0-40 as typical of the gravity purity of well-exhausted molasses ; then, if s be put equal to I (i.e., let the Ss; (I — m) product be pure sugar) the value of the expression gives the sucrose in a raw sugar of s, purity compared with what will be obtained when pure sugar of I00 purity is made. In the table below are calculated values of the expression for values of s, from 0-94 to 0-99. z Ss, (I —.m VALUES OF ne) for m = 40, OR SUCROSE IN SUGARS OF 94 TO 99 PURITY 1S. = inh 1 COMPARED WITH SUCROSE IN SUGAR AT I00 PURITY. ehh 3 SO ieee at gb a! = ™ Ss; —™m $s; —m 94 °0 I +0444 — O57 I 0309 97 °4 I ors 94°1 I +0436 95°8 I -0301 97°5 I -O174 94 °2 I +0428 95°9 I -0293 97 °6 I -0167 04 °3 I-0420 .- 96-0 I -0286 O7-7 I -O160 94 °4 I -O412 96-1 I -0278 97 °8 I ‘0153 94°5 I -0404 96-2 I -0270 07-9 I -0146 94 °6 I -0395 96 *3 I -0263 98-0 I -0138 04°7 I -0387 96 -4 I -0255 98 -I I -O131 94°8 I -0379 96 °5 I *0247 98 -2 I -O124 04°9 I -0372 96 -6 I -0240 98 +3 I -OL17 95 °° I -0364 96 °7 I +0233 98 -4 T -OIIo 95:1 I +0356 96-8 I -0225 98 +5 I -O103 95 °2 I -0348 96-9 I -o218 98 -6 I -0096 05 °3 I +0340 97:0 I -0210 98 -7 I -0089 05 °4 I -0332 97 ‘I I :0203 98 -8 I -0082 05°5 I +0324 97:2 I -0196 98-9 I -0075 95-6 I -0316 97 °3 I -o188 99-0 I -0068 The table may also be used to obtain the relative quantity of sucrose in raw sugars of different purity. Thus the sucrose contained in a raw sugar of 96-5 purity compared with that in a raw sugar of 97-4 purity is as I-0247 ~ I-o181 =1-0065. As acommercial basis of comparison, however, it is the actual weight of raw sugar which is required, and to obtain this comparison it is necessary to divide the values given in the above table by the sucrose in the product, pure sugar being taken as 1. Thus, in the example given above, if the sugar of 96-5 purity contains 95-8 per cent. sucrose, the weight of raw sugar compared with the weight of pure sucrose will be 1-0247 + 0-958 = 1-0696, and if the sugar of 97-4 purity contain 96-1 per cent. sucrose, its relative weight will be r-o181 + 0-961 = 1-0594. The relative weights of the two raw sugars will be as 1-0696 : 1-0594 = I+0097 : I-0000. To complete the argument developed above it may be also shown that 440 CHAPTER XXI the quantity of refined sugar that can be obtained from a juice is constant and independent of the number of operations and also independent of the purity of a raw sugar obtained as an intermediate product :—If raw sugar s (7 —m) j(s —m) If this raw sugar is refined, per unit of sucrose present there is obtained s(j7 —m) s—m and per unit of sucrose in the original juice ial x ; is made of purity s the quantity of sucrose contained therein is s—m s (I—m) ee ila 7 (I —m) other value. This is also the same quantity of sugar that will be obtained if pure sugar is made directly from the juice. The argument given above assumes that the molasses obtained by the producer and the refiner are of the same purity. and the same result will follow when s changes to s, or any The Value of the Crop to the Producer and the Conditions of Sale.—Since for every percentage of sucrose and for every purity there is produced a different weight of raw sugar, the money received by the producer will vary for every case. This variation is also controlled by the conditions of sale. The basis of sale at present obtaining in the United States markets is :— The price quoted refers to sugar of 96° polarization ; for each 1° above this standard the sugar receives a bonus of 1/32 cent per lb. and for each 1° below a fine of 1/16 cent per lb. is imposed. The fine and bonus are in- dependent of the market price, whether 2 cts., 3 cts., 4 cts., etc., whereas it is evident that both fine and bonus should be in proportion to the price. Hence a fine or bonus just at one price must necessarily be unfair at another. These figures also only refer to the limits of 94° and 98° polarization, sugars above the latter figure receiving no extra bonus and sugars below the former being only sold on special terms. The basis of sale is also faulty in that it does not take into consideration the purity of the product on which, equally with the polarization or percentage of sugar, the yield is controlled. Taking as a first approximation that the value of the sugar is proportional to the polarization, it is easy to see that 1/32 cent or 0:03125 cent per lb. per I° fairly well represents the increased value when sugar is at 3 cents, and that at 2 cents the producer is benefited, the buyer losing with sugar at 4 cents. Similarly, a mental calculation will show that the buyer gains in all cases when sugar is fined 1/16 cent or 0:0625 cent per 1° below 96 test. The question is, however, more complicated than this and may be treated thus :—In the previous section it was shown that the relative quantity of raw sugar produced is given by the expression E Le as x - where # is the percentage of sucrose in the raw sugar. With sugar quoted at ¢ cents per pound the sugar will sell for (s (I — m) ee | s—m ~ x f vl je a) om) \°— (96 — p) X oO: 0625 cents. | S—m c + (fp --96) X 0:03125 | cents, or for The net income received by the producer will be this quantity less the ex- RAW SUGAR 441 penses of containers, handling, railway, shipping, and port and dock dues, These may be expressed as a lineal function of the weight of the product, so that the nett sum received by the producer is either 5 x = xo + (p —96) x 0-03125 | Ao a = cents or ste — 8). 200) fe pe __,/S(@—™m) _ Too a, x anak (96 p) x 0-0625 } Mire acme x = cents where £ is a constant. It should be the object of the producer to produce that quality of raw sugar which will afford him the maximum of profit. In nearly every case the maximum will be found when both # and s are 96°. That is to say, when he makes an absolutely dry 96 test sugar. The natures of the equations given above are not such that they can be solved for a maximum value, and it will be necessary to construct tables for each and every factory with its particular conditions. As showing how the sum received by the producer may vary, one series of calculations is appended for sugar quoted at 3 cents, cost of containers, freight charges, etc., being $6-00 per ton. Percent.} Purity Relative Selling Expenses Sugar in of Weight Price Gross at Raw Raw in per | Returns $6.00 Sugar. Sugar tons ton. $ per ton 94:0 94°5 11,068 57 °5000 636,410 66,408 94-0 95:0 II,025. ; 57°5000 634,937 66,150 Sacer [O55 10,993 57 *5000 622,079 65,958 94°5 | 95°0 10,967 58-1250 | 637,478 65,802 94 °5 | 95°5 10,925 58-1250 | 635,014 65,550 94°5 96-0 10,884 58 -1250 632,632 65,304 BRO LL GR 5 10,867 58-7500 | 638,436 65,202 95 °0 96-0 10,827 58 -7500 636,086 64,962 95 °0 96 °5 10,786 58 -7500 633,077 64,716 6 95°5 96-0 10,781 59-3750 640,102 64.686 7 95°5 96 °5 10,740 59 °3750 637,688 64,440 7 95°5 97 °0 10,691 59 *375° 634,777 64,146 7 96-0 96°5 10,674 60 -0000 640.440 64,044 76 96:0 | 97:0 10,635 60 -0000 638,100 63,810 574,290 oG-0" [07 °5.. 46" 0,597 60 -0000 635,820 63,582 572,238 96 °5 97°09 | 10,580 60 +3125 638,106 63,480 574,626 96°5 97°5 10,543 60 +3125 635,879 63,258 572,621 96 +5 98 -o 10,506 60 +3125 633,643 63,036 570,607 97-0. I. 297-5 10,488 60 -6250 635,824 62,928 572,896 97°00 98 -o 10,452 60 -6250 633,652 62,912 570,940 97-0 98 +5 10,417 60 -6250 631,530 62,502 569,028 97°5 98-0 =| 10,398 60 -9375 633,629 62,388 571,241 975 | 98:5 10,362 60 -9375 631,433 62,172 569,261 97°5 | 99°0 10,326 60 -9375 629,240 61,956 567,264 98 -o 98 +5 10,309 61 +2500 631,426 61,854 569,572 98 -o 99:0 10,273 61 +2500 629,221 61,638 567,583 | 442 CHAPTER XXI A Basis for the Valuation and Sale of Raw Sugars.—lIf p be the sucrose in a raw sugar of purity 7, affording a barrel syrup of purity m, the available sucrose is p X aa 7 (I— Mm) There is also produced barrel syrup, the quantity eel i (tm), barrel syrup compared with a unit of refined sugar be &. Then the equivalent of dry barrel syrup being p X Let the value of a unit of dry available sucrose is f Shae + x Pues ; Px Fm) Ks j (I —m) ie Let c cents per lb. be the price quoted for refined sugar ; then the value of raw sugar will be in cents per Ib. : j ont ha ly ee ee [b+ iea me RP Xa mae 2 neg je where / represents the sum of the refiner’s expenses and profits. p If k = 1, the left-hand part of the expression reduces to c X a le Dry Substance, in which case the refiner buys dry substance and not sugar. The refiner’s expenses will, however, increase as the purity falls, and there- fore another term should be added to the expression. This term would be of the form“, where q is a constant and f(j) represents the increased ex- 50): penses due to fall in purity, so that the complete expression for the logical pate ay j (I — m) f (9) A basis of sale such as the above would be fair to both producer and refiner, and would allow the former to make sugars of low water content, thus elimin- ating danger of deterioration and permitting him to economize in expense of containers and freight. The refiner similarly would pay for what he re- ceives, including the barrel syrup. If the sale is conducted on a basis of valuation of raw sugars will be cp { available sucrose only, the expression will be cp | aS ieee | \7 (x FG) REFERENCES IN CHAPTER XXI. 1. “‘ History of the Island of Barbados,’’ London, 1673. Zee Nieuwe — Vethandelingen seam van het Koninklijk Nederlandsche Instituut. 1820, 2) ror 7 1830) 35271. (Gulf, UIST, “sy syo)e)- CaR2 V18605868" 1663" C.R- 1880) 91,993: La. Plant., 1896, 154. Jour. Soc. Chem. Ind., 1898, 13, 535. Java Arch., 1899, 7, 629. Int. Sug. Jour., 1902, 4, 45. Oh URES IEW Tosa Shah, Jeahl, Siac JEDI @; SP coe eee Tae r2. K3. 14. 15. 16. 17. 18. 19. 20. ait 22. 23. 24. 25: 26. Pgh RAW SUGAR La. Ex. Sta., Bull. 125. Jour. Ind. Eng. Chem., 1918, 10, 3. an Exot.) alle 162; Deut. Zuck., 1901, 26, 453; 1904, 29, 1,000. Zeit. Zuck. Boh., 1904, 29, 423. La. Ex. Sta., Bull. 166. “Quantitative Laws of Biological Chemistry,’’ London, 1g915. Int. Sug. Jour., 1909, 11, 343. H.S.P.A. Ex. Sta., Agric. Ser., Bull. 24. H:S.P/A. Ex. Sta., Agric. Ser, Bull) 36. W. Ind. Bull., 1905, 7, 226. “Guide pour l’essai et l’analyse du Sucre, Paris,’”’ 1864. “Technical Calculations for Sugar Works,’’ New York, rgIo. Moniteur Scientifique, 1846. Zeit. Ver. deut. Zuck., 23, 407. Oes-Ungar. Zeit. Zuck., 44, 877. Zeit. Ver. deut. Zuck., 62, 166. 443 CHAPTER. X XE MOLASSES MotasseEs is the material from which sugar has been removed in the course of manufacture. The terms “ first molasses,’ ‘‘ second molasses,’”’ etc., thus result, though generally molasses without any qualification refers to the final product from which it is not possible or convenient to extract any more sugar ; the terms “‘ final,” “ exhausted,” ‘‘ waste,”’ and “‘ refuse’ are, however, used to specify this by-product. In French practice “ mélasse ”’ refers to the final product, the terms “‘sirop’”’ or “ égout ”’ being used for the intermediate materials. The term molasses does not occur in refinery practice, ‘‘ barrel syrup’’ being the phrase used. In Louisiana the term “black strap’’ is employed to specify the product obtained when making 96 test crystals for refining purposes, “‘ table syrup’’ being used when the molasses are intended for consumption, as obtained when making yellow sugars. Since molasses is a residue obtained by the continual removal of sugar, it at once follows that the composition of the molasses is determined by the composition of the juice, modified by such changes as occur in the process of manufacture. Thus, the same relative proportions of reducing sugars and non-sugars must occur in the molasses as are present in the juice, except in so far as reducing sugars are destroyed or non-sugars are removed inde- pendently of concurrent removal with raw sugar. Very detailed analyses of waste molasses have been made by Geerligs,* as they occur in Javan factories, and others in less detail of Hawaiian molasses have been made by Peck and Deerr.?. From these analyses a num- ber of typical results have been selected and are given in the annexed schedules, wherein will be found examples covering the extreme variations ever likely to occur. Comparing the results, the higher percentage of ash in the Hawaiian molasses is to be noted, together with instances of a very low content in reducing sugars; these examples are afforded by juices from very ripe irrigated Lahaina cane, which often contains only 0-2 to 0-3 per cent. of reducing sugars. The low optical activity of the reducing sugars in carbonation molasses is to be noted,* and in this material the activity is positive as often as negative. * This peculiarity is not confined to molasses from carbonation factories. Demerara molasses frequently exhibit it. Two samples analysed by Peck and Deerr gave 36.5 and 35.0 polarization, and 38.3 and 34.9. sugar per cent, 444 MOLASSES . | 445 COMPOSITION OF JAVAN MoLassEs, (GEERLIGS. * * Brix, 5. sie RS -- 87-4 87-1 87-4 84°7 87°7 81°8 91 °2 79-2 81°8 83-2 Dry substance percent. .. 82-5 82:°3 83-6 77:4 80°7 75°9 85-3 74:0 77°6 76°7 Polarization .. oe -« 32°8 27-4 26:0 27.6 26-2 25 -6 31 -8) 31-8 28-6 33-8 Sugar per cent. ae ~- 36°5 32°5 32°3 33°8 33°%. 3353 37 °2 34°7 28-5 34-1 Reducing sugars per cent. 23 ‘2 29-4. 27 +0) 244) 22.7 20)-O-21 3) EO -l 25-0) D5 -4 Organic non-sugars per cent. 10°6 12°7 15°7 9°9 13°5 14°3 16°8 14°8 17°0 18:0 Gums per cent. ae we EF Ek er Pee 2th Oe 2150). ACO) Ol-0E OG Ash per cent, 8:0 7°97. “7°09 O-2) £1 -4= 8-3, 10-0 8-4) 7-40 Oro Insoluble ash per cent. TQ) FG iar ey la Se wed ee 2 eo EEG) Soluble ash per cent. GE Grit Ora gg 98s 70 ey Se OO Stee: res Lime per cent. st jer OF) JOe5 Op TeO 2s NOs um Or 2 Onn Or 7 ane Dee onan Potash per cent. 3:69 Ota a7) OOD Alc2t3i-N tai 63) -3 one Sulphuric acid per cent. E39. sisi. OO O18) 101-5! 10, OF 70173) 1 Orcs, O34 Chlorine per cent. > (O04 ORB MO 33 Or7-"OlrrG) OCG, .Ol-3" FOl-35 (O52) / O)-6: Absolute purity ate -- 44°3 39°5 38-6 43°7 41°2 43°8 43°6 46-9 36-1 44°5 Polarization x I00 ; . 37 °5 31-4 29°7 32-6 29-9 313 34°9 40-0 34°9 40°6 Brix COMPOSITION OF HAWAIIAN MoLasses, (PECK AND DEERR.) Brix . wk ote -- 86-0 81-4 89°9 86°5 87-9 93°9 91°2 93°5 84°'9 84°6 Dry substance percent. .. 81-8 79-6 85-0 83-3 82:5 86-0 84°1 84:5 82:7 79°9 Polarization .. sé -. 27°5 35°5 27°5 28-0 28°8 32:5 38-0 32°5 23°5 31-0 Sugar per cent. ac ve 882 7.300 3h -O) 3873 135-0) 38-1 4065 Sh e2nS Or esa Reducing sugars percent. .. 21:0 12-2 26°8 24°3 18:4 Q:I 5:9 12°6 23°7 12°'9 Ash per cent.f 4c =» f0°4. 10-9 IO+E 10-3) O\-4 Tr -8 12-8) 05-9262 7050-5 Nitrogen per cent. .. ae ORS, TOF" 0-3 :0-2— 0.24) 10)-0) 1 -O MoO onomors Chlorine percent. .. a 28h 92 TA EOP 2 -O%'2)278 12 OU sO) ta eOm GEonsemas Absolute purity... -+ 38°7 46°3 37°5 39°9 42°5 44°3 47°9 41-7 36°8 4353 Polarization x 100 ee 32 °0 43 °6 30°6 32-4 32°7 34°6 41-7 34°7 27°7 36°6 Brix Since the reducing sugars and the non-sugars in a juice must occur in the molasses in the same relative proportions, the question at once arises as to what is the effect, if any, of these bodies on the quantity of sugar that remains in the molasses. A typical beet sugar molasses formed in the absence of reducing sugars contains about 45 per cent. of sugar, whereas a typical cane molasses contains about 30 per cent., together with about 20 per cent. of reducing sugars. Cane molasses is, however, much more variable in composition than beet molasses, and a casual inspection of a series of analyses will show that generally a high percentage of reducing sugars is accompanied by a lower percentage of cane sugar. From a large number of analyses of molasses made by Geerligs, Peck, Deerr and others, the writer has obtained the average analyses of molasses divided into the following categories as regards the reducing sugars :—Below 14 per cent. ; between 14 and 18 per cent. ; between 18 and 21 per cent. ; between 21 and 24 per cent. ; between 24 and 27 per cent. ; over 27 percent. The results appear in the annexed table, all being calculated to 80 per cent. dry matter. * Carbonation molasses. 7 The potash in Hawaiian molasses is of the order 4 per cent. as in Javan molasses, but the sulphates are often present in a quantity from two to three times as great as in Javan molasses. 446 CHAPTER XXII AVERAGE COMPOSITION OF MOLASSES AS CORRELATED WITH REDUCING SUGARS PER CENT. Dry Reducing Non- Total Absolute | Reducing Sugars Substance. | Sugars. Sugar. | sugars. | Sugars. Purity. Non-sugars. 80-0 0:0 45 -0* 35:0 45:0 56-2 0:0 80 -o 9 ‘8 305s 42 | 5 33,59 46 +I 45 °4 0°3 80-0 17-1 S70 . 1 259 54 °1 46-2 0-7 80-0 20 *8 EY ay gaan ue 55°5 43°4 0:8 80-0 22-1 34°8 73h 56-9 43°5 0-9 80-0 25 °3 32°5 22 °2 57°8 40 +6 I-t 80 -o 28 -I 31°55 20 -4 59 °6 39-4 I °4 On inspection it is at once apparent that there is a tendency for the sugar to decrease as the reducing sugars increase, and that the total sugars present also show a very distinct increase. It follows then that when the composition of a juice is known, an idea can be obtained regarding the probable composi- tion of the molasses that will result. This composition, it is evident, will be determined not by the absolute quantity of reducing sugars in the juice, but by the ratio of reducing sugars to non-sugars ; when this ratio is small, as occurs in beet juices and occasionally in cane juices, a molasses of higher purity may be anticipated ; in the presence of much reducing sugar a molasses of low purity is obtained. In routine technical control over nearly all the cane sugar producing 100 olarization . ; oeoaorosr in the neighbourhood of 30 has come to be regarded as indicative of good work. Probably in the great majority of cases this is so, but it must be remembered that the value of this ratio is governed by the routine followed by the analyst, especially as regards the concentration in which the degree Brix is determined, and the. quantity of lead acetate which is used in the analysis. In addition, though the direct polarization is indicative generally of the quantity of sugar in the molasses, the ratio between sugar per cent. and polarization is by. no means constant, and it is quite possible to have a molasses of ‘ 35 test” contain less sugar than one of “ 30 test.”” The determination of sugar as opposed to polarization affords a much more reliable criterion, and on this - basis a gravity purity of 40 will generally be found representative of com- mercially exhausted molasses, those special cases indicated in the foregoing paragraphs being excepted. There are, of course, many other factors besides the ratio of non-sugars to reducing sugars that determine the purity of the waste molasses, and indeed the statement made above has only an empirical basis. The deter- mining factors have been made the subject of a classical research by Geerligs,? whose work is abstracted below. He calls attention first of all to the differ- ence between beet and cane molasses ; the higher solubility of sugar in the former he attributes to the formation of a compound between the salts and the sugar, the solubility of which is greater than that of sugar itself, and he defines beet molasses as a hydrated syrupy liquid composed of sugar and salts. In a cane molasses the presence of reducing sugars leads to a similar reducing sugars-salt-water complex which abstracts water which would districts, a value of the ratio * Typical beet sugar molasses. MOLASSES 447 otherwise cause the solution of sugar. The water in the complex appears in analysis, and hence the solubility of the sugar in the water as returned appears lower than the normal solubility in water alone. In place of referring the dominant factor to the reducing sugars /non-sugar ratio, Geerligs con- siders that the deciding factor is the reducing sugars to ash ratio, or more exactly the alkalinity of the ash as representative of the amount of organic salts present, as it is these that enter largely into the formation of the syrupy compound. The position of the reducing sugars is also discussed by Geerligs. He recalls the older idea that glucose was a molasses-former, and in a series of experiments shows that this idea is ill-founded.* In one series of experi- ments he dissolved cane sugar in a specially purified honey and allowed the excess of sugar to crystallize out. As indicated in the table below, the effect of the reducing sugars in increasing the solubility of the cane sugar is zero. EFFECT OF GLUCOSE ON SOLUBILITY OF CANE SUGAR. (GEERLIGS.) Sucrose crystallized 9°3 g:I 10-0 8-9 9 °8 9-2 9:0 Sucrose dissolved Scam ayy 15-9 15-0 16-1 15-2 15°8 16-0 Glucose .. i ee 2 -O T2°5 omre) 3-0 I-o 0-5 — Water Loo t fae ie fae, Lia Fed Viste) In another series of experiments he showed that it is possible under certain conditions to “ salt ’’ cane sugar out from solutions by the addition of glucose, thus affording experimental evidence in favour of the actual existence of the postulated sugar-salt-water complex. On the other hand Williams* has observed that, if a commercially ex- hausted molasses be boiled almost dry and then be allowed to stand for some weeks, there is a formation of small impure sugar crystals that can be re- covered in centrifugals after “‘ pugging’’ the mass with a small quantity of cold water. He considers that this observation negatives the existence of the complex demanded by Geerligs’ theory, and goes so far as to accuse the water of being the only molasses-former. Some controversy over the matter has resulted, but in the opinion of the writer both observations are consonant with each other. Evidently if all the water is removed the com- plex must be broken up, and it should be possible by rapid work to separate the sugar crystals before the syrupy compound is formed, since the time element must enter into its formation. In addition it is possible that the molasses used by Williams while being commercially exhausted may not have been absolutely so. In the early days of research in sugar technology, viscosity as preventing the movement of sugar molecules was considered to be one of the chief factors in molasses formation. Geerligs has shown that eventually even in jellies all the sugar capable of crystallization does so, and accordingly vis- cosity can only be of influence in determining the time taken for complete crystallization. Technically this influence is not unimportant, and is par- ticularly noticeable in a comparison of the rapidity of crystallization in refineries and in raw sugar houses, material of equal purities (but with the ““gums’”’ removed by char filtration) crystallizing much more rapidly in the refinery than in the raw sugar house. The purity of the refinery “barrel syrup ”’ is, however, substantially the same as that of the molasses afforded in the houses where the raw sugar was produced. * All non-sugar is a molasses-former since the water required to keep it in solution will also dissolve sugar. The old idea of positive and negative molasses-formers referred to those bodies which increased and decreased the solubility of the sugar in water. In the former class were included the organic salts of the alkalies, which in Geerligs’ theory are responsible for the formation of a very soluble complex. 448 CHAPTER XXII There is one more point to discuss in regard to molasses, and that is due to Claassen, who paradoxically has called attention to the influence of the sugar itself. He refers to a supersaturation in the mother liquor whereby sugar is kept from crystallizing and molasses of high purities result.* Although loss here easily occurs, such material is due to bad technique and not to the formation of a real molasses. The position of glucose in Geerligs’ theory has led to many misunder- standings. It has been proposed to commercially salt out cane sugar by the addition of glucose, and, though such a scheme might in certain cases result in the separation of cane sugar, there could be no possible prospect for commercial success. On the other hand it has been proposed to ferment the glucose, recover the alcohol, and obtain an enhanced yield from the purified material. One result of this scheme would be to raise the purity of the molasses so that little if any more sugar would be obtained ; that this is so can be seen at a glance from the typical analyses of molasses quoted in the beginning of this chapter. Finally, it may be mentioned that the inversion of part of the cane sugar has been proposed as a corollary of Geerligs’ theory with the view of obtaining a greater yield. It is hard to see how such a meaning could be read into his results. | The Extraction of Sugar from Molasses.—Although no one of the processes used in beet sugar factories has succeeded in establishing itself in the cane sugar industry, all are of such technical interest as to deserve cursory mention. They fall into three classes ; those dependent on the formation of insoluble saccharates, those based on the precipitation of sugar by the addition of fluids in which cane sugar is insoluble, and those based on the application of diffusion phenomena. The initial conception of these processes is mainly due to French chemists, though their development is largely due to Germans, Saccharate Processes. Cane sugar in combination with various metallic oxides forms insoluble saccharates. Of these bodies, which were first studied by Péligot® and Soubeyrau, ® the following are of technical importance: Monobasic lime saccharate, CaO C,,H».0,,, H,O: this is soluble in water, and is obtained by mixing molecular proportions of lime and sugar. Sesquibasic lime saccharate, 3CaO 2C,,.H.,0,,: this is obtained by pouring an excess of a milk-of-lime into a dilute sugar solution and evapora- ting the mixture to dryness. Bibasic lime saccharate, 2CaO C,.H,.0,, : it is formed by mixing two molecular proportions of lime to one of sugar. It is soluble in 33 parts of cold water. Tribasic lime saccharate, 3CaO C,,H,,.0,,: it is obtained by boiling a solution of the bibasic saccharate. Bibasic strontium saccharate, 2S7O0 C,.H,.0,,: it is obtained on mixing two molecular proportions of strontia with one of a hot solution of sugar. Monobasic strontium saccharate, SvO C,,.H,.0,, : it is formed on cooling the bibasic compound. Monobasic barium saccharate, BaO C,.H5.0,,: this is the only barium saccharate known. It is formed as a crystalline precipitate on mixing a hot saturated solution of baryta with a solution of sugar. It dissolves in 41 parts of cold water. Lead saccharate, PbO C,,H»0,,: it is obtained on mixing litharge with a solution of sugar. It is very insoluble in cold water. 7 * cf. page 403. —— ==" : \ See. MOLASSES 449 Dubrunfaut? was the first technicist to use these processes. He mixed a hot saturated solution of baryta with molasses at 30° Baumé. The resulting saccharate which formed at once was washed with cold water, suspended inwater, and decomposed by a current of carbon dioxide. After filtering off the insoluble barium carbonate aliquor of 98° to 99° purity was obtained. A sample of sugar thus made obtained a Council gold medal at the Great Exhibition of 1851. Difficulty in regenerating the barium has prevented the extension of this process, which, however, still remains in limited use. Following on Dubrunfaut’s work, Scheibler, Seyferth and Manoury, all working about 1870, developed the schemes known as elution processes. In these, milk-of-lime or dry lime was mixed intimately with undiluted molasses. An impure saccharate resulted, which was purified by washing with alcohol afterwards recovered. A somewhat similar process is the sucro-carbonate process of Boivin and Loiseau,® in which a current of carbon dioxide is passed through a paste obtained on intimately mixing lime and molasses. The sugar is precipitated as a complex lime-sucro-carbonate, which after washing is suspended in water and broken up by further passage of carbon dioxide. The use of strontia was patented by F. Jiinemann Pierre de Rieu in 1866, and it was used ina secret process about this time in Germany. The credit of making the process technically successful is due to Scheibler, who devised two schemes. In the bibasic process!® three equivalents of strontia to one of sugar are mixed with hot dilute molasses. The saccharate that forms is separated from the mother liquor by filtration and washed with a Io per cent. solution of strontia. In order to decompose the saccharate it is placed in vessels set up in a battery,-through which is passed a 2 per cent. solution of strontia at a temperature of from 4° to 15° C. The bibasic saccharate is decomposed into the monobasic body and strontia, the whole operation taking forty-eight hours. The monobasic saccharate is decom- posed by carbonation and the strontia used in the next series. In the mono- basic process" a solution of strontia is mixed with molasses, the temperature not being allowed to rise above 20° C. The monobasic saccharate which forms is separated by filtration and decomposed by carbonation. The strontia process due to the Austrian, Steffen, is known as the sub- stitution process.” The five operations in the cycle of this scheme are :— I. Formation of a soluble bibasic saccharate in the cold. 2. Transformation of the bibasic saccharate into sugar and insoluble tribasic saccharate by boiling. 3. Separation by filtration of the tribasic saccharate. 4. Regeneration of the mother liquors by the addition of fresh molasses. 5. Periodic reduction of the mother liquors. In outline the different processes are worked as follows :— I. Molasses diluted to 11°-12° Brix are mixed with continued agitation with powdered quicklime in the proportion of one part of sugar to one of lime. The mixture is then filtered to remove scums. 2. The filtrate is heated in autoclaves to a temperature of 105°-110° C. 3. The tribasic saccharate formed on heating is filtered, the cakes washed with boiling water, and the saccharate used instead of lime in the treatment of the raw juice. 4. The mother liquors coming from the filtration of the saccharate are used to dilute a further portion of molasses. 2H 450 CHAPTER XXII 5. After a time the mother liquors become too charged with impurities to be returned. They are then treated separately, two operations being sufficient to exhaust them. In all, the mother liquors are returned from 25 to 30 times. The second process of Steffen!® is known as separation, and this of all the saccharate processes is the one that has survived. Its operation falls into three parts :-— I. Preparation of a very finely divided quicklime. 2. Formation of a tribasic saccharate in the cold. 3. Extraction and purification of the saccharate. In preparing the lime, a very pure non-siliceous stone is used, which is burned out of contact with the fuel. The burnt lime is brought by some means to a very fine state of division. In the United States, Raymond mills are exclusively employed. These mills separate the fine lime from the residue by means of an air blast. In the second operation the molasses at a density of 10°-12° Brix is cooled down to a temperature of 5°-6° C., and the powdered quicklime is gradually added to the material until 210 parts of lime per 100 of sugar have been used. During the operation, the molasses is constantly agitated, and its temperature is not allowed to rise above 13° C. At the completion of the process there is obtained a pasty mass consisting of tribasic saccharate and lime. This precipitate is filtered off and washed with cold water, after which the washed cake is used in the treatment of fresh juice, The filtrates contain some sugar, and this is recoverable by boiling when an in- soluble saccharate forms, which is recovered by filtration. In some cases the washings are run to waste as not being worth while treating. The lead saccharate process has been lately developed by Wohl and by Kassner. Molasses mixed with 80 per cent. of water is kneaded with litharge in the proportion of 150 parts lead oxide to 100 of sugar. The pasty saccharate is separated and decomposed as in the other schemes, affording a liquor of 98-99 purity. Difficulty of regenerating the lead and objections to the use of lead in the preparation of an article of food have prevented any extension of this scheme. Osmosis.1®—It follows from the above sections that if the salts could be removed from an exhausted molasses, the conditions of solubility of the sugar would be altered and a further portion would be capable of crystallization. About 1850 a method of effecting this was worked out by Dubrunfaut. The principle of his process known as osmosis is as follows: If a concentrated solution of any soluble body be separated from a weaker solution or from water by a semi-porous membrane, such as parchment, the two solutions will pass through the membrane until they are of the same concentration. The rate at which this osmosis or diffusion takes place is not the same for all bodies; inorganic salts such as potassium chloride diffuse much faster than sugar; hence if a solution of molasses be separated by a parchment membrane from water, a greater proportion of salts will pass through the membrane in a given time than sugar. An osmogene is an apparatus to effect this separation; it consists of a structure similar to a filter-press, in which are held a series of wooden frames, shown in elevation in Fig. 273. Between each frame are placed sheets of parchmentized paper, pierced at the angles to correspond with the apertures shown at A, B, C, D, and at A!/,B!,C/,D/, in Fig. 273. At 6 and c in the one frame, and at a and d q a i , : MOLASSES 451 in the other, are small channels establishing communication with the interior of the frame. If, then, water enters at B and molasses at D, the water will flow along the canal formed by the openings B and into the interior of the frames by the channels 4, and the molasses will similarly flow by way of D and d’. The water will discharge itself along the canal formed by the open- ings C andc, and the molasses along that formed by the openings A ‘and a’. There is thus a continual flow of molasses and water separated by a sheet of parchment. The water which leaves the apparatus now charged with a proportion of molasses is called water of exosmose, and it contains roughly about half the salts originally present in the molasses. Although this process has been largely used in times past and is still to a certain extent employed in beet sugar factories, it is financially unsuccessful ; the large size of the osmogenes required (500 square feet diffusion surface only being sufficient to treat three tons of molasses in twenty-four hours) the extreme dilution of the osmosed molasses, the expense of evaporation, and the small extra yield of sugar, entirely discounting the monetary value of the process. FIG. 273 Precipitation Processes —In Margueritte’s process!? molasses was first purified from “‘ gums ’”’ and a part of the salts and then treated with a large excess of alcohol, which was afterwards recovered. Glacial acetic acid is another precipitant of sugar; its use has been proposed by Wernicke and Pfitzinger.1® The writer does not believe that this process has ever been used on the commercial scale. The Disposal of Molasses. By sale as such.—In certain places the sale of molasses to distillers or for direct consumption forms a part of the routine ; in some cases, particularly in the muscovado process followed in Barbados, this procedure is very profitable since fancy prices are still to be obtained for these grades of molasses. Considered from the point of view of the agricultural chemist, nothing can be said in favour of this scheme as it entails the absolute removal from the soil of much valuable plant food, particularly in the form of potash. With the very pure juices found in the Hawaiian Islands the molasses amount to about 20 per cent. of the sugar shipped, a figure rising to as much as 4o per cent. in the case of the impure juices found in Demerara, and elsewhere ; molasses on an average contains about 4 per cent. of potash, so that the sale of the molasses implies the removal from the soil of from 18 to 36 lbs. potash per ton of sugar shipped. 452 CHAPTER XXII Sale as Cattle Food.—The sale of molasses as cattle food was originated on the large scale by Mr. G. H. Hughes, in 1902, who observed that the finely divided interior pith of the cane was capable of absorbing large quantities of molasses, affording a product which could be shipped in bags; this product was put on the market under the name of “ molascuit.”’ The manufacture of this article requires plant of a very simple nature, which is generally capable of being placed so as to fit in with existing arrange- ments. The method of manufacture in a certain West Indian factory is as follows. The bagasse, before the manufacture of molascuit was started, discharged itself from a scraper elevator on to the cross-carrier which conveyed the bagasse in front of the furnaces ; a sifter of one-eighth inch mesh and of 8 ft. x 4 ft. dimensions was interposed between the elevator and cross-carrier ; the bagasse fell on to this sifter, to which an oscillating motion was given by an eccentric driven off a convenient engine; in the passage of the bagasse along the sifter to the cross-carrier a number of the finer particles fell through and these were directed down a shoot on to the flue wall of the boilers. The brickwork on the top of the flue was replaced by sheet-iron plates and a drying surface obtained for the bagasse; after the latter had been dried it was again sifted through a sifter of mesh one thirty-second of an inch. Refuse molasses was mixed with the doubly sifted bagasse powder in the proportion of seventy parts of molasses to thirty parts of bagasse ; the molasses was concentrated to 85° Brix before mixing and a much more even product was obtained when hot molasses was used ; before bagging, the molascuit was allowed to cool. The mixing was performed in a “‘ Carter’’ kneading machine. The double sifting is of importance so as to eliminate the larger particles of bagasse, especially splinters, consisting of the hard and indigestible outer rind. In other installations more elaborate machinery is employed, and in large plants the use of a dryer similar to. those used for drying sugar would be advisable both for the bagasse and for the final product. The keeping qualities of the product depend very largely on the extent to which it is dried. Molasses feeds are not a complete food and are very deficient in proteid, the percentage of nitrogen being only about 0-15 per cent. ; hence they re- quire supplementing with other material, especially in the case of working animals. In Mauritius the seeds of an acacia-like shrub, Lucena glauca, are used in combination with molasses, and in Louisiana the ration of molasses is frequently balanced with cotton seed meal. T. U. Walton!* advises a ration of 15 lbs. of molasses to a 1,270 lb. horse, and states that for working horses this quantity has no undue fattening effect, that the salts in this quantity of molasses are not deleterious, and that sugar is generally an efficient substitute for starch. The following analyses of molasses feeds are due to Browne?® :— Cotton Seed Extracted Blood, Meal, Corn, Rice, Cereal, Corn, Oats, Oats, Bran, Bagasse, Molasses. Molasses. Molasses. Molasses. Molasses. Water axe Ai 1G) Xs, II ‘gO 12 +23 8 +40 13-98 iBatiner. = we T Ek 3°15 2 +30 o 83 0 +90 INST ey. ne Wey Ly OYE 6-27 7°79 9°70 5°11 Fibre 53 EOS I4 *30 12 °78 13:00 5 64 Protein ae ee LOS T2755 6 +41 14 :00 I +94 Sugars ae I5 -O1 21-65 19 +43 5 50 55°94 Other carbohydrates 29-87 29 -98 39 06 48 +56 16-49 MOLASSES 453 Manufacture of Alcohol.—In the West Indies, Argentina, Peru, Natal and Australia the distillery forms an integral part of the sugar factory and large quantities of a potable spirit known as rum are manufactured. As the sale of alcohol leaves all the fertilizing elements available for their return to the soil, this is perhaps the most rational scheme. Market limitations are, however, a factor that prevent the more extended use of molasses in this way. Eventually, however, a more extended field may be afforded by the growing use of alcohol as fuel and in the arts. Use as Fuel.—Molasses is occasionally used as fuel in combination with the bagasse. The large amount of ash formed on combustion is, however, a troublesome factor. During the potash shortage in the Great War a number of Hawaiian factories installed special furnaces to both burn the molasses and to recover the potash. The design included a storage tank set in the brickwork of the furnace in which the molasses was sufficiently heated to allow it to flow freely to the hearth, on which it was burnt under a fire-tube boiler. The flues were made of wide cross-section to allow of the deposit of potash carried forward in a volatile form, Return to Soil—This method of disposal, which is of all perhaps the most rational, is discussed at Jength in Chapter V. REFERENCES IN CHAPTER XXII. I. ‘‘ Cane Sugar and its Manufacture,’’ Manchester, 1909. 2a rio byAs Bx. Sta: aAenc. oer, bull 28: Bie Gi L803, (25). 25455 1600, 125, Oris 4. Int. Sug.) four., 1917, 19, 218: 5. Ann. Chim. Phys., 67, 113; 73, 103. 6. Jour. Prak. Chem., 26, 468. 7. U.K. patent 656 of 1859. 8. U.K. patent 3865 of 1877. g. U.K. patent 54 of 1867; 3093 of 1893. to. U.K. patent 331 of 1881; 398 of 1882. 11. U.K. patent 2239 of 1882. 12. U.K. patent 967 of 1883. 13. U.K. patent 2416 of 1883. 14. U.K. patent 22859 of 1895; 6733 of 1900. 15. U.K. patent 14925 of 1895; 23171 of 1895. 16. U.K. patent 2053 of 1863; 8502 of 1884; 9243 of 1884. 17. U.K. patent 1254 of 1867; 164 of 1869. 18. U.K. patent 1817 of 1882. 19. Haw. Plant. Mon., Sept., 1905. 20. ,LG~ Plank 3454.230: CHAP Tih Soret BAGASSE AS FUEL AND THE STEAM GENERATING PLANT OF THE CANE SUGAR FACTORY In this chapter an account is given of the special points of interest of bagasse* regarded as a fuel, and of the designs of furnaces and boilers used in its combustion. Composition of Bagasse.—Bagasse consists essentially of crude fibre and water, together with more or less cane sugar and glucose depending on the degree of extraction practised in the mill whence it is derived. In addition there are present ash, organic acids, cane wax, and the other bodies associated with plant life. By the crude fibre is here meant the material insoluble in water. C. A. Browne! found as an average that purified cane fibre contained : Per cent. Cellulose (including oxycellulose) (C,H, 0;), ate oe 55 Mylan 4) es a6 3 oie 20 Araban $ (CoHsOa)n ae e Fe aes ah 4 Lignin aC, ¢(CHs)sO49 56 ae oe Se an 15 Acetic acid, CH,COOH os ae te ee or 6 As bagasse is an indefinite material, it is not possible to give an exact figure for its percentage composition as regards carbon, hydrogen, and oxy- gen; but since the crude fibre and sugar of which its solid matter almost entirely consists have nearly the same percentage composition, the variation between dry specimens of bagasse of different origin is not great. As long ago as 1869 Robert Angus Smith® gave the ultimate composition of dry bagasse, calculated to ash-free material, as carbon 47-6 per cent., hydrogen 6-2 per cent., and oxygen 45-4 per cent. These results are almost identical with the 46-8 to 48-4 and 6-3 to 6:7 found by Geerligs,? and the 47-9 to 48:3 and 5-5 to 5:7 found by Norris.* The ultimate composition of bagasse is influenced to a small extent by the proportion of rind tissue and pith tissue, the former generally containing * Bagasse was the term originally applied in Provence to the refuse from olive oil mills. Hence, as anything worthless, the word was used to describe a disreputable woman, and it appears in English as ‘‘ baggage.” The ultimate root of bagasse may possibly be the same as the Anglo-Saxon baeg, referring to the olive skin as a bag. If so, megass coming from bagasse by phonetic change is cognate with belly, which also denotes a bag. 454 eT ee ae BAGASSE AS FUEL 485 more carbon than the latter. Thus Norris found with Yellow Caledonia cane 48-75 per cent. carbon in the rind fibre and 47-2 per cent. in the pith fibre. So also as between varieties which differ in the proportion of rind and pith tissue differences may be expected, but these differences are not of much moment, and it is justifiable to accept a flat rate for the composition of dry bagasse. Including the ash in certain computations that follow, this will be taken as 46-5 per cent. carbon, 6-5 per cent. hydrogen, and 46-0 per cent. oxygen. Heat of Combustion of Bagasse.—As dry bagasse of any origin has nearly the same ultimate composition, it would be expected that its heat of combus- tion would also vary within very narrow limits. That this is so has been definitely proved by the determinations of Geerligs,? who found values from 8289 to 8514 B.T.U. per Ib. of dry bagasse; of Burwell,® 8289 to 8384; of Norris,> 8089 to 8344; and of Kerr,® 8375. The differences that occur may reasonably be attributed to variation in the proportion of rind tissue and pith tissue. Norris found the former to afford 4 per cent. more heat than the latter, and this difference may also be extended to give the bagasse from one variety a higher value than that from another. In the various computations that follow the heat of combustion of dry bagasse will be uni- formly taken as 8350 B.T.U. per lb. This figure is considerably higher than that obtained by calculation from the heats of combustion of the fibre (taken as cellulose) and of the sugars, or as obtained from Welter’s rule, which gives the heat of combustion of an organic compound as that of its constituents, less that of such hydrogen present which can be combined with oxygen in the proportions in which they form water. Products of Combustion of Bagasse.—One pound of carbon requires for its combustion 2-67 lbs. oxygen, and one pound of hydrogen requires 7-93 Ibs. oxygen. One pound of dry bagasse of the typical composition accepted above will then require: 0-465 X 2:67 + 0-065 X 7:93 = 1-75 lbs. oxygen. The bagasse itself contains 0-45 lb. oxygen, so that there has to be supplied 1-30 lb. from the air. The composition of the atmosphere will be taken as oxygen 23 per cent., water vapour I per cent., nitrogen 76 per cent., included in “ nitrogen ”’ being all the rarer gases of the atmosphere. To supply 1°30 lb. in oxygen there will be then required 5-65 lbs. air, and the products of combustion per pound of bagasse will be :— Due to carbon 0-465 X 2-67 +0°465.. 1-701b. Carbon dioxide. Due to hydrogen 0-065 x 7-93 + 0:065.. 0-58 1b. Water. Introduced with air 5°65 X 0-01 Teens si -OGrED: 5°65 xX 0°76 4 +30 lb. Nitrogen. It is not possible to burn any material with the admission of only the exact amount of air necessary; for, with the very best control, 50 per cent. excess is necessary, and Io00 per cent. excess is not considered unreason- able. With 50 per cent., 75 per cent., and roo per cent. excess air, the products of combustion per pound of dry bagasse will then be :— 456 . CHAPTER ek xait 50 percent. 75 percent. 100 excess. excess. per cent. Due to Carbon Carbon dioxide = I-70 L+7O I-70 Due to Hydrogen Water $e cae 0°58 0 +58 0 +58 Introduced with air Water eae fe 0 -08 0-10 O-II . Nitrogen 56 He 6 +45 7 +51 8 +59 = Oxygen dic oe 0-65 0:97 I +30 To reduce these figures to a pound of mill bagasse containing 55 per cent. dry matter and 45 per cent. water, all that is necessary is to multiply by 0:55 and to add 0-45 lb. to the water, whence the following results are obtained in terms of a pound of mill bagasse :— PouNDs, PER PouND OF BAGASSE 50 per cent. 75 per cent. Loo per cent. excess air. excess air. eXcess. Carbon dioxide ae a OcO” 0-94 0-94 Water .. ae 8 ORO E 0°82 0 -83 Nitrogen me ae Foe CLOG 4°13 4°72 Oxygen aie ake PoeeON sO 0°53 0-71 At a temperature of 0° C. and 760 mm. pressure, the volumes of 1 Ib. carbon. dioxide, water vapour, nitrogen, and oxygen, are respectively 8-1, 19°8, 12-8, 11:2 cu.ft. At a temperature of 273°C. or 523° F., which may be taken as representative of that prevailing in flue gases, these volumes are doubled. The volumes of the products of combustion of 1 lb. of mill bagasse may then be estimated :— Cupic FEET. 50 per cent. 75 per cent. IOo per cent. excess alr. excess air, excess air, Carbon dioxide 50 See MEOI2 18 +2 18 +2 Water .. oe yo Oe Scr S255 3207, Nitrogen ae no 5 OOeO 105 °8 I2I +o Oxygen eh te 56 8-7 II ‘9 15-9 otal nn. mite ae se LAORO 168 +4 187-8 These results may be used to compute the required diameter of chimneys or areas of flues. Engineering practice allows a velocity of 20 ft. to 30 ft. per second to the waste gases. It is also customary to take the effective diameter of a chimney as four inches less than the actual diameter. Temperature reached in Combustion of Bagasse.—One pound of dry bagasse of the typical composition affords on combustion 8,350 B.T.U. with the exact quantity of air for combustion. If the latter is at 32° F., the temperature of combustion T will be found from the following equation :— 8350 = 0:58 [180 + 970 + 0:48 (TI — 212)] + T (1-7 x o-217) + T (0-06 X 0:48) + T (4:30 X 0:244), whence T = 44Io. If the air is at ¢° F. instead of 32° F., the temperature reached will be T + (¢ — 32). In this equation the latent heat of steam is taken as 970, and the specific heats of steam, nitrogen, and carbon dioxide, as 0-48, 0:24 and 0-22. BAGASSE AS FUEL 457 Similarly, the temperature of combustion of bagasse with associated water and with various quantities of excess air can be calculated. Certain examples are tabulated below, referring to the typical dry bagasse with 45, 50, 55 per cent. of associated water. The specific heat of oxygen is taken as 0°22. Excess AIR. Water per cent. None. 50 per cent. 75 per cent. 100 per cent. bagasse. a] Rise tictem pertare Poe 45 3320 2430 2160 1940 50 3020 2310 2000 1850 55 2770 2140 1900 1720 These calculations do not take into consideration unburnt fuel or losses due to radiation. The temperature of combustion is a most important point in the economics of bagasse firing. If caused either by an excess of air, by an insufficient supply of air, or by an excess of water (inefficient mill work), the temperature falls below a certain limit, products of distillation are formed which pass through the furnace unburnt, and lower the quantity of heat which would otherwise be afforded by the bagasse. Hence, the effect of sending to the furnaces material containing only a little more than the normal quantity of water may have an effect on the steam production quite out of all pro- portion to a computation based on the heat required to evaporate the ad- ditional quantity of associated water. Bolk? believes that the point at which unburnt products distil over is where the bagasse contains 52 per cent. or more of water. Steam Available from Bagasse.—The subjoined table is calculated on the following basis: each pound of water present in the flue gases, whether associated water or water formed on combustion, abstracts 1,250 B.T.U.: eachYpound of gases, whether carbon dioxide, oxygen, or nitrogen, abstracts 100-B.T.U. These data correspond to external air at about 80° F. and to a flue gas temperature of a little over 500° F. No allowance is made for radiation loss or for unburnt fuel. The calculation is made for bagasse with 45, 50, 55 per cent. water, the dry matter being taken as having a heat of combustion of 8,350 B.T.U. per lb. The last column in the table gives the computed Ibs. steam per ton of cane containing Io per cent. fibre, and can be easily converted to conform with any other fibre content. It is not to be overlooked that when the bagasse contains 55 per cent. water there is only 40 per cent. fibre, and hence 500 lbs. bagasse per ton of cane. When the bagasse contains 45 per cent. water, there is 50 per cent. fibre, and only 400 Ibs. bagasse per ton of cane. Accordingly, the quantities in the penultimate column ex- pressing the computed lbs. of steam per Ib. of bagasse are not directly pro- portional to the steam available per ton of cane. The quantity of dry fuel available remains the same, the heat afforded is the same, but more goes away as steam in the flue gases in one case than in another. 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Jo ‘yuso 10d WIOI}. osseseq pue wo1y osseseq “[e}07 “ure9}S ses OI sulureyuoo ouvs | Arp ‘q] tod wresys ‘q[ tod urv9}s jo IOF o}SeM Jo uo} iad urvoys “sq] JuoTeAIn bay “sq[ quoyeatn bay "yuoo 19g | o[qeireay [e101 “sq[ yuoTeamn bay ‘ % ‘ALi zgS‘h NOILsnaWoo dO LVa_Y “AALVM ‘INGO Uda SP assvovg ‘aSSVOVd AO SHNIVA IVNUYAHL GULVWILSH BAGASSE AS FUEL 459 Actual Results obtained in the Combustion of Bagasse.—Following on the computation given in the preceding section, some results of boiler trials are given in tabular form below.* Of these Nos. 1-3 were made by Kerr,$ and 4, 5, 10, II were made by the writer; the rest are taken from ‘‘ Steam,” published by the Babcock & Wilcox Co. In tests 1 and 2 flat grates with Dutch ovens were used ; in 3 a flat grate with extended Dutch oven, the volume of the combustion space being 3-83, 2:58, 6-00 cu. ft. per rated B.H.P. respectively. The tests numbered 4, 5, Io, II, were made with Dutch ovens with step grates. These tests seem to cover a wide range of conditions as regards grate area, heating surface, and fuel burnt ; but there does not appear to be any instance that can be picked out pointing to superiority in any one particular. Roughly they may be interpreted as indicating that a well-designed steam producing plant should actually afford 2-5 lbs. steam per lb. of bagasse burnt, when the latter does not contain over 45 per cent. water; and if these trials count for anything this quantity should form a basis of design. The tests Nos. 4 and 5, which afforded results much higher than any of the others, were made with two boilers set tandem, the second having been added with the original installation of furnace and grate left unchanged. Accordingly, a relatively small quantity of bagasse was burnt per sq. ft. of heating surface. The term efficiency is used in two senses. In the line marked A, it refers Heat in steam produced | Heat in fuel burnt ’ Heat in steam produced — Heat in steam due to associated water in fuel. Heat in fuel burnt. This last ratio is unusual, but is a rational method of comparison. to the ratio in the line marked B, it refers to the _ ratio DaTA OF VARIOUS BOILER TRIALS. Water per cent. bagasse -- 55-3 46.5 45-8 47.4 47-4 52.4 52.9 51.8 51.7 45.9 45.0 Lbs. dry bagasse per sq. ft. heating surface perhour 0.44 0.81 1.94 0.39 0.37 0.79 0.70 0.76 0.84 0.77 0.85 Lbs. dry bagasse per sq. ft. grate area per hour .. 44.3 47.0 IOI.0 41.3 41.0 71.9 63.9 147.1 163.4 29.8 33.0 Heating surface Grate surface Flue gas F° O24 = 52G~ 5G SU4A2Q. | 424. 5636 S545 @ * 52 Excess air per cent. 124 98 go 36 34 56 70 84 68 52 40 Lbs. steam from and at 212 F° per lb. dry bagasse 3-88 4.78 4.33 5-45 5-28 4.26 4.67. 4.30 4.15 4.20 4.28 “ Efficiency’? A 45.0 55.5 50.3 63.3 61.3 49.4 54.2 49.9 48.2 49.4 49.7 “ Efficiency ’’ B 64.0 69.0 63.3. 77-3 75-1 66.7 71.4 66.5 64.5 62.5 62.4 Too.t 58.1 52.r 108.8 108.8 91.8 91.8 -193.4 193.4 38.6 38.6 The Connection between Quantity of Fuel burnt and Heating Surface.— The combustion of a fuel gives rise to a quantity of hot gases at a certain * The data as published have been rearranged by the writer and certain of the items entered have been calcu- lated from the records as given in the publication whence they are taken. 460 CHAPTER XXIII temperature. The principles under which this obtains have been given in the preceding sections, with special reference to bagasse. These hot gases come into contact with the boiler, which is at a lower and constant temperature. _ The rate at which the heat from the hot gases passes to the water in the boiler is proportional in some way to the difference in temperature. Rankine® assumed that the rate was proportional to the square of the temperature difference, and this assumption is developed very completely by Kent.?° Accepting this assumption, the writer offers the following graphic analysis with special reference to bagasse burning. Let the bagasse on combustion afford hot gases at a temperature of 2200° F.; let the boiler be at a temperature of 350° F. (roughly 120 lbs. gauge): the initial temperature difference is 1850° F. After the gases are cooled down to 1200° F., the temperature difference is 850° F., and the rate of transfer is proportional in the two cases to the squares of 1850 and 850. The graph in Fig. 274 is obtained thus: On the horizontal axis are set out the temperatures 2200, 2100.... 450. From these points are drawn ordin- ates proportional to the reciprocals of the squares of the temperature differ- ences ; that is to say, to 1850, 1750....100. The graph is then obtained by drawing a curve through the ends of these ordinates. Then the area enclosed between any two ordinates, the base line, and the curve, is propor- tional to the heating surface required to reduce the temperature of the gases from the temperature under the first ordinate to the temperature under the second ordinate. In the graph above the curve have been inserted the areas of each division of 100°, and below the horizontal axis the total area at any particular temperature. Thus to reduce the temperature from 800° to 700°, an area proportional to 709 units is required; the total area required to reduce the gases from 2200° to 700° being 2154 units. Again, on this basis it follows that if a certain heating surface, say 3349 sq. ft., is sufficient to reduce the hot gases to 600° F., then to reduce them to 500° F. an additional 1658 sq. ft. will be required; that is to say, 5007 sq. ft. in all. Again, if the external air be taken as 80° F., a reduction in temperature from 2200° to 80°, or 2120° F., would represent roo per cent. efficiency. A reduction to 600° F. indicates a fall of 1600° F., so that at this temperature in the waste gases the efficiency is ae = 75-5 percent. A reduction to 500° F. would similarly indicate an efficiency of 80-1 per cent., or an increase in efficiency and steam production of 6-0 per cent., which would be obtained by an increase in the heating surface from 3349 to 5007 or 49 per cent. Again, let a quantity of fuel be burnt such that the waste gases pass away at 500° F., and let the heating surface be 5007 sq. ft. Let double the quantity of fuel be burnt, or the original quantity per 2503 sq. ft. This area is found from the graph to correspond to a temperature of 680° F., and to an efficiency of 76:0: that is to say, doubling the fuel capacity of a furnace only decreases the efficiency from 80-1 per cent. to 76-0 per cent. In other words, a steam-producing plant is a very elastic system capable of carrying great overloads with relatively very small decrease in efficiency. This discussion is very incomplete and treats of heat transfer by con- ductance only, and also reflects the question of radiation losses. It has been introduced rather to present the general principle involved, along with the engineering problem, namely the determination of the economic heating surface, questions of first cost of installation as well as fuel consumption BAGASSE AS FUEL OS: HA a es HHH] Bieter feels cee esl Pi ei eb Eerie TTTTTIVITLIS & BERETA a Cer A SL} S2ONc 8 oe ee RX SenEn sx 2g SSS Q 8 * 8 +8 $ \ © rota g Sz S$ $8 38 ae, > SSS ° RRs QQ Fas TTTITII PITT oe GRAPE FRR eS REPRE EGA! Rena SaeR On w SS BS 9 $ s N 461 Fic. 274 462 CHAPTER XXIII being considered. For more detailed general treatments reference may be made to Kent’s “Steam Boiler Economy,” and to Kreisinger and Ray, Bull. 18, U.S. Bureau of Mines. Steam Value of Bagasse.—It is a matter of observation among those who have had an extended experience in cane sugar factories that at times the bagasse “‘ steams ’’ much worse than at others. Not only is there an in- sufficient production of steam for the wants of the factory, but there is diffi- culty in burning the bagasse. In Demerara, Mauritius, and Hawaii, the ‘ ' ' ‘ x FC 2, SOA BSSSSSSESSSSESESSESE NINN PW, SSSSSSSSSSMSH SG Ssss LixvielitsnbdtLedddic fA KI SS s N N N N N N ZSSSSSSSSSSSS | > SSSEPYLTTPPITIIIPLTOIOIDIIDIID IIIa DIODE boOD OS. AAAAARRANR ULMLULLLLLM BL LELEL LLU SS SSS Fic. 275 writer has observed this condition associated with the cane known as White Transparent or Rose Bamboo, and in Demerara with “ seedlings ” generally. The detailed studies of Geerligs and Norris eliminate the question of the fibre of one cane being of more value than another, except in a degree quite insufficient to account for the difference which may be observed; and al- though low fibre content will account for an insufficiency of fuel it will not explain bad combustion. . In a detailed study of the matter, Geerligs* observed among other points that there was a great variation in the volume occupied by the same weights of bagasse from different varieties ; the weight of roo c.c. of bagasse lying BAGASSE AS FUEL 463 all the way from 5-45 to 7:95 grams, and the following observations were drawn. 1. A denser bagasse was of superior fuel value. 2. A denser bagasse was generally rich in cellulose. 3. Canes with most fibre give a bagasse of superior fuel value. These observations tend to connect the mechanical structure of the bagasse with fuel value, for it is not unreasonable to suppose that a grate AV sag Ss her Y MMMM \\N fame was mag 5 tes pe | = ce ot cS didi rn rn el aaa —AN ae |i Bish eeeN KE ERK SS KKK Fic. 276 : = i fa + a (= area sufficient for a dense bagasse may be too small for that afforded by another type, and the solution of the trouble would be in the installation of auxiliary grate area. In addition, the trouble may be due to a combination of all the causes tending towards low thermal value :— 1. A fibre with the lower limit of the recorded heat of combustion. 2. A fibre which retains after crushing a higher quantity of water. 3. A lower percentage of fibre in the cane. 464 CHAPTER XXIII 4. A bagasse of low apparent specific gravity. All these causes combined in one cane would be sufficient to account for the actually observed results, although any one might not be of itself of sufficient magnitude to be detected in the routine control; and, further, the trouble might be accentuated by the objectionable combinations causing an imperfect combustion in the bagasse. . Furnaces employed in Bagasse Combustion.—The main principle from which the various designs of bagasse furnaces have been developed is the complete combustion of the fuel before the hot gases impinge upon the boiler surface. This end has been obtained by external furnaces, large combustion chambers, arrangements of arches, check walls and baffles designed to cause the gases both to mix and to pass over surfaces of incandescent brickwork, and by the use of waste radiant heat to partially dry the bagasse before combustion begins. These principles seem to have been first clearly enun- ciated by Marie (patent 1017 of {188z), and to have been put into practice by him. In the Figures below are collected a number of typical designs. FiG. 277 Fig. 275 shows a furnace and setting devised by Abel,’* whose name is usually attached to this design. The bagasse enters at a and falls on to the step grate . The combustion chamber is formed by the inclined arch k, acting in combination with the check wall e, and beyond this there is formed a supplementary chamber. The storage platform for bagasse is at i 1, and this platform enclosed a chamber k whence hot air may pass into the supplementary combustion chamber with the idea of completing any imperfect combustion. Air also enters the furnace through the passage /f. The path of the gases is underneath, back through the tubes and out along the side. This type of furnace is largely used in Demerara, where it’ was developed. Fig. 276 shows a type much simpler than the foregoing, and which is used extensively in the Hawaiian Islands. Here the gases travel under- neath and along the sides and back through the tubes to the main flue. The type that has been evolved in Java is shown in Fig. 277. It is noticeable for the steeply inclined grate and for the overhanging arch, a, at the upper portion of the grate and for the baffle, , running in a reversed direction. In some cases in Java a supplementary furnace is used, with BAGASSE AS FUEL 465 the intention of drying the bagasse before combustion obtains in the furnace proper. Fig. 278 shows a furnace as applied to a Stirling boiler, and differs from the other designs by the adoption of a horizontal arch, a, in place of a sloping one, and by a check wall, 8, of larger dimensions. LZZ£Z’LZ LL ALA hh ea RIMM MOAI OO yi The principle of causing very complete mixture of the products of com- bustion by means of a reversed check wall, a, combined with a long extended combustion chamber, is shown in Fig. 279, as applied toa Babcock & Wilcox boiler. All the above examples have been shown with inclined grates. fig. 280 shows a flat grate provided with hollow blast furnace bars, a. The air necessary for combustion enters by the conduit 0. NY ee Ree | SSS y) WZ FIG. 279 The grate disappears entirey in the Cook furnace (U.S. patents 203643, 1886 ; 362362, 372969, 1887; 382992, 1888; U.K. patent 12393 of 1889). In this design the bagasse is burnt on a hearth, the air necessary to combustion being supplied through the twyers a. As shown in Fig. 281, the typ‘cal Cuban setting of one hearth to two boilers is indicated with passage of the gases underneath, back through the tubes and out over the top of the bo ler to the main flue. . 21 466 CHAPTER XXIII The grates themselves are either flat bar, step grate, or flat grates, The first-mentioned type has almost disappeared. Sections of forms of step grates are shown in Fig. 282. The type on the extreme right comes from Java, and eliminates one d fficulty of the step grate, namely a tendency for the bagasse to feed forward unevenly. KML LALLA LA KELLY, a SSS ZZEELLLELLLL Fic, 280 Besides the grate proper, an ntegral portion of the furnace is the ash grate ind cated in the above sketches at the lower portion of the inclined portion. Frequently a large air space is left between these two elements both for the admission of air and for the removal of clinker. In other designs the ash grate is made so as to allow of pivoting to aid in clinker removal. The flat grate shown in Fig. 280 is intended to be used with forced draught, and may, of course, be applied to any other type of furnace and boiler. — — 4 = LEC LLL TILE, WLLL, ALLTEL SELLE ELEN CREW REE =x PLDT ITIIIT TOIL SNNAND SSS CEI: ee ae ASQ ~ ON A LLLLLL BILE —————————— SSS ef oe} x SS Lin SSS SS Of SIELLA TITS TTLELL ‘ SSSpp>o Fic. 281 A point wherein considerable difference in practice exists is the ratio of openings between fire bars to total area of grate. Generally the area is approximately evenly divided between bar and opening, but examples may be found with either twice as great as the other. All schemes now used in the stoking or firing of bagasse may be referred back to Fryer and Alliott’s patent (284 of 1883), other essential principles of BAGASSE AS FUEL 467 which scheme appear again in one (8320 of 1903) granted to the Stirling Boiler Co. This scheme is shown diagrammatically in Fig. 283. Bagasse direct from the mill is delivered to an elevator, which in turn discharges to a scraper carrier, a, running in a direction at tight angles to the furnaces. From the mouths of the furnaces, b, shoots, c, communicate with the Fic. 282 carrier, over each shoot being a sliding trap door controlled from below, whereby bagasse may be directed to the shoot, whence it gravitates to the furnace. The actual feeding to the furnace is often effected by a rotating drum, d, on which are placed longitudinal projections, e, shown on an enlarged scale in the right-hand sketch. In this design the door, f, auto- matically closes when the hopper is empty. Two lay-outs of furnaces are general. In one they are arranged in two lines between which is located a platform, on to which surplus bagasse may Fic. 283 be discharged through trap doors, and which serves as storage room. Other- wise the carrier may be extended beyond the line of the furnaces, and may discharge any surplus to a shed there located. In this case a return carrier is provided to deliver the surplus back to the main carrier when required, The boilers used in connection with bagasse are not specialized types, 468 CHAPTER XXIII modern practice seeming to be equally divided between the horizontal fire- tube boiler and some form of the water-tube. In some houses two distinct batteries have been installed; the latter to supply steam at higher pressure to the engines, and the former to give steam at a lower pressure to the heating and evaporating stations. It was for long considered a fundamental idea in sugar-house design that a type of boiler of large water capacity should be installed, so as to allow for unequal consumption of steam in the boiling house. This argument has been used to support the fire-tube as opposed to the water-tube boiler. In badly designed or badly operated houses these unequal loads may occur, but rational operation is capable of eliminating them. In addition, water- tube boilers with specially constructed large water spaces are made, and in any case the difference is not large. The first cost of the fire-tube boiler is less, but the water-tube being con- structed in larger units decreases the cost of operation, though large units are objectionable when it comes to cutting out a unit for cleaning or washing out. In the writer’s opinion economy in steam is not so much a question of the boiler as it is of the furnace, of the firing of the bagasse, and of the intelligence with which the whole factory is operated as a co-ordinated whole. The ‘‘ Boiler Horse Power ”’ required in a Cane Sugar Faetory.—Given the number of tons of cane to be ground per hovr, the designer of a factory has to determine the “‘ Boiler Horse Power ’”’ or square feet of heating surface to be installed in the steam-producing plant. To give a rational answer to this question the designer should be supplied with complete data showing how much steam is intended to be used in the factory in heating, in evapora- tion, and in pipe and cylinder condensation, etc. This will depend on the quantity of mixed juice to be obtained per ton of cane and on the system of heating and evaporation adopted. In the beet sugar industry this is a comparatively simple matter, since the rate of operation can be regulated to a uniform daily output, and all the fuel consumed is independent of any supplied as a waste material. In the cane sugar industry in many localities it has come to be considered that the bagasse should afford all the fuel necessary, and the operations in the factory are often controlled by the quantity of bagasse, or in other words by the fibre in the cane. This quantity varies between the limits of 10 and 15 per cent., so that between different factories there may be a 50 per cent. variation in the quantity of fuel available from the cane. Hence, a ratio of Boiler Horse Power to cane correct for one factory may be quite inadequate for another, if it is only desired to burn a certain quantity of bagasse at its maximum efficiency. It is fortunate, however, that steam- producing plants permit of very considerable elasticity, whilst remaining within reasonable economic limits. For example, in the data of boiler trials collected in this chapter there is very wide variation in the quantity of dry bagasse burnt per sq. ft. of heating surface, and very much less varia- tion in the efficiency. Evidently the greater the heating surface the greater is the opportunity to abstract heat from the hot gases ; but, after the tem- perature of the gases has been reduced to a certain temperature, very large heating surfaces are required to effect any further reduction, and conversely the capacity for producing steam by burning increased quantities of fuel per sq. ft. of heating surface is but little affected. This point has been discussed at length in a previous section. BAGASSE AS FUEL | 469 From a study of actual results, and bearing in mind capital, cost of extra fuel, etc., the writer has come to the conclusion that, as a basis of design referred to a cane with ro per cent. of fibre, the economic limit is reached when about r lb. of bagasse with 50 per cent. fibre is burnt per sq. ft. heating surface per hour. Under these conditions this is equivalent to 400 sq. it. heating surface per ton-cane-hour, and allowing for one boiler in ten being out of service for cleaning furnaces, etc., to 450 sq. ft. in round numbers. When the fibre in the cane increases, more bagasse is available for fuel and more will be burnt per sq. ft., with only a small fall in the efficiency, and an increase in the total amount of steam produced, which will be used up in heating a greater amount of mixed juice following on a greater dilution. Some figures from actual factories all of recent design follow :— Hawaii.—Thirteen factories. Average 429: extremes 350 to 570 sq. ft. per ton-cane-hour. Java.—tTen factories. Average 429: extremes 319 to 569 sq. ft. per ton- cane-hour. Fic. 284 Cuba.—Seventeen factories. Average 532: extremes 385 to 610 sq. ft. per ton-cane-hour. In the taking out of these data the results have been expressed as fire-tube heating surface, water-tube heating surface being considered as of 20 per cent. higher value. The ratio of grate area to heating surface is found to offer wide variation, the lowest ratio the writer has ever observed being 1:54, and the highest I : 343; generally this figure is found to be within the limits I : 70 to I : I20. Connected with this ratio is the quantity of bagasse burnt per sq. ft. of grate area per hour. With a ratio of grate area to heating surface of 1: 100, and 1 lb. bagasse burnt per sq. ft. heating surface per hour, roo lbs. will be burnt per hour per sq. ft. of grate. Of some importance also is the volume of the combustion chamber in relation to fuel burnt. Difficulty at once arises in determining what is the combustion chamber, since some engineers treat the space under the boiler as a combustion chamber, and others only that volume before the gases come in contact with the boiler. Treating of the external furnace only before the gases reach the boiler, the volume usually found is from Io to 30 cu. ft. per 470 CHAPTER’ XXTI too sq. ft. of heating surface, or per I lb. of bagasse per hour on the basis outlined above: including the space beneath the boiler as combustion volume, this ratio is roughly halved. The writer believes that the ex- aggerated combustion volumes sometimes found are inefficient, as exposing a large area for radiation and affording opportunity for leakage of cold air. Drying of Bagasse.—The earliest proposals to use waste heat for drying bagasse preliminary to its combustion are those of Merrick (U.S. patent 3994, 1845) and Crosley (U.K. patent 11158, 1846). These patents claimed the use of endless horizontal metallic belts arranged in a brick chamber, through which the waste flue gases were exhausted to a chimney. This device has become a part of routine practice in Mauritius, where their introduction is due to Eynaud. The general arrangement followed is in- dicated in Fig. 284. Ina factory working up 50 tons of cane per hour the sécherte was 40 feet long, 7 ft. wide and 30 ft. high. The carriers ran at 7 ft. per minute, the period of exposure being 18 minutes. The bagasse entered with 50 per cent. of water and left with 35 per cent., corresponding to the removal of one half of the water. These sécheries are operated in combination with induced drafts; other arrangements use a vertical shaft, down which the bagasse falls in counter-current relation to the ascending hot gases. This scheme appears in Gros-Desormeaux’s patent (1532 of 1882), and again has been experimented with by Kerr and Nadler,!* who place in the shaft a series of inclined trays. For a mill working up 1,000 tons cane per day, they estimate the total cost erected of the plant to be $15,000-$16,000. A third scheme is the Huillard dryer,!* based on the beet pulp dryer, and in operation in Egypt. This arrangement consists of a vertical brickwork chamber, down which the bagasse travels in a spiral. A fourth scheme employs a rotating drum slightly inclined from the horizontal and similar in principle to the sugar dryer described in Chapter XXJ. In a series of boiler trials made by Kerr and Nadler with bagasse containing 53-5 per cent. of water, and the same bagasse dried to 45-4 per cent., the evaporation from and at 212° F. was 1:63, and 2-35 lbs. water per lb. of fuel, or 3-51 and 4-65 Ibs. per lb. of dry fuel. This result is probably to be correlated with the incomplete combustion that occurs when the water in a bagasse exceeds a certain limit. Although computation will show that a very sensible benefit obtains from drying bagasse, the scheme is little used, and the benefits are counter- balanced in other ways. There has to be supplied fan draft, together with the power required to operate the dryer machinery; some mechanical loss occurs on handling; and difficulty is experienced in firing the very light material, which has a tendency to be swept through the flues unburnt. Furthermore, in operating a sécherie in Mauritius, the writer observed that a little inattention would result in the contents of the sécherie igniting, with the loss of fifteen minutes’ supply of fuel. Value of Bagasse as compared with other Fuels.—The relative value of bagasse, wood and coal is often required, as fuel statistics are generally based on the coal value of the fuel burnt. There is no constant fuel value for either bagasse or coal, and any factor adopted depends on the local .conditions ; coal, depending on its quality and the skill used in firing, may give from 7 to 12 lbs. of steam per lb. consumed. On an average from 4 to 5 tons of bagasse are equal to a ton of average coal. Woods, weight for weight and BAGASSE AS FUEL 471 of the same water content, have practically identical values; air-dried wood usually contains from 20 per cent. to 30 per cent. of water and from 3 to 3-5 tons are equal to a ton of average coal. Molasses are of very similar value to wood, the predominant factor being, of course, the water content. Cane straw contains as a rule about Io per cent. moisture and from 2-5 to 3 tons are equal to a ton of coal. A table giving a comparison of fuel values follows :— Gross B.T.U. Fuel. per Ib. Welsh Steam ot $e aie es a= I5,000—16,000 Pennsylvania Anthracite .. =f an ss I 5,000—16,000 Newcastle ae sre sa = 2 os I4,000—14,500 Lancashire oe oe! =< =a oe -* I4,000—14,500 Scotch ae a = ae ee ae I3,000—14,000 Australian ae a = Pi, Re Pe I3,000—14,000 Indian > 23 a Se = te I3,000—14,000 Patent Fuel .. sis me =x a 2 I5,000—16,000 Air-dried wood 25 per cent. moisture = ore 4,500—5,000 Green Bagasse 45 per cent. water E 2a 4,500 Cane Straw Io per cent. water re ap 2c 7,500 Molasses 25 per cent. water = sf ae 4,500 Petroleum oy xe =e a % I6,000—17,000 Carbon .. an me x Se 2e ie 14,400 Fuel Value of Molasses.—Atwater found 6956 B.T.U. per pound of dry matter; Norris* obtained 4759 and 5137 B.T.U. for molasses containing 20-8 and 21-9 per cent. of water and 14-1 and 8-4 percent. of ash. Hooge- werf!* found 5275 B.T.U. for a sample with 19-4 per cent. of water. The great trouble that has always been experienced in burning molasses in combination with bagasse is the formation of a large amount of ash and clinker. During the campaign of Ig14-15 special molasses furnaces and boilers were erected in Hawaii both to burn the molasses and to recover the potash in the ash. The molasses were burnt on a hearth in an extended furnace, the ash in part remaining on the hearth and in part being deposited on the flues. Under a 16-ft. x 6-ft. horizontal fire-tube boiler there was burnt per hour 880 lbs. of molasses, which afforded 1,476 lbs. steam and 77 lbs. ash. It will be tound, however, that it is only when the cost of fuel is exces- sively high, or when the value of molasses is abnormally low, that it is economical to burn this material, even allowing for the recovery and sale of the potash. Fuel Value of Cane Straw.—Hoogewerf™ found 7841, Koenig and Bien- fait?! 7409, and Norris* 7780 B.T.U. per lb. of dry matter. 472 CHAPTER XXIII REFERENCES IN CHAPTER XXIII. Ta. bx, ota., bull or. SiG aL OOQ) alleys Java Arch., 1906, 14, 445. H.S.P.A. Ex, Sta., Agric, Ser., Bull. 32. La. Plant., 1906, II. ea. Ex. Sta., Bull. 109. Java Arch., 1906, 14, 319. La. Plant., 1913, 54, 315- “‘The Steam Engine and Other Prime Movers.”’ 10, ‘‘ Steam Boiler Economy.” 11. Pyroc. Inst. Civ. Eng., 1894, 123, 370. 12. Int. Sug. Jour., 1908, 10, 13, Int. Sug. Jour., 1907, 339. 14. Bull. Assoc. Chim. Suc., 1905, 150. Ce ON OURS a re aiayen CHAPTER XXIV THE POLARIMETER* Tus chapter treats of the principles involved in the determination of cane sugar through its action on plane polarized light, the subject being carried so far as to enable the operator to appreciate the principles of the methods and the construction of the instruments that he employs. For more detailed treatment reference should be made to the larger works of Landolt or of Browne, and to textbooks on Physics and on Light. Nature of Light.—Ordinary light is accepted as being the effect on the eye of vibrations in the ether which take place in all directions. According to the wave length of the vibrations, the eye receives the sensation of colour, white light being the effect on the eye of the simultaneous receipt of ether vibrations of different wave lengths and colours, which severally ge to form the colours of the spectrum, into which white light is split up on its passage through a prism. Polarized Light.—By means of certain devices the vibrations of ordinary light may be confined to one plane and such light is called polarized light. The position of the plane may be determined by many devices and hence, if the plane be rotated, the angle through which rotation has occurred may be measured. Rotation of the Plane of Polarization—There are certain bodies character- ized by the possession of an asymmetric carbon atom (or atom which is at least quadrivalent), which have the property of rotating the plane of polariza- tion when a beam of such light is passed through them. Generally the magnitude of the angle through which the plane is rotated is proportional to the concentration of the active material and the length of column through which the passage of light occurs. Hence if the rotation is known for one definite length and concentration, the composition of an unknown solution can be found when the length of column thereof and the rotation produced thereby is known. Cane sugar is but one of very many bodies of the class mentioned above, and, owing to its commercial importance, polarimeters are built specially designed and graduated for sugar analysis. Such instruments are often called saccharimeters, but it is to be understood that instruments designed for general work can be used equally well for sugar analysis, and with some types the converse is also true. * In English the word “ polariscope’” has come to mean an instrument devised to measure the rotation of the plane of rotation. The appropriate use of the word is to designate an instrument or device to see or examine the phenomena of polarized light, and in this sense the wordis correctly employed. Polarimeter is used here when reference is made to an instrument measuring rotation. 473 474 CHAPTER XXIV Those bodies which rotate the plane of polarization are said to be optically active. Means of obtaining Plane Polarized Light.—-All light reflected from a plane surface is partially polarized, and for a certain angle a it is wholly polarized. This occurs when tan «4 = index of refraction of the reflecting substance (Brewster’s law).1_ This method of obtaining polarized light was used in the first polarimeter of record by Biot,” to whom the science of polari- metry in general, and its application to sugar analysis in particular, is due. The means now almost always adopted to obtain a ray of plane polarized light is the prism of Nicol or some modification thereof. The construction of this is explained below. If ordinary light be allowed to pass through a rhombic crystal of Iceland spar, ABCD, Fig. 285, it suffers double refraction and two rays of light emerge where only one entered. This phenomenon, illustrated in Fig. 285, always obtains unless the entrant ray of light pass in a direction parallel to the line joining two opposite obtuse angles, this direction being known as the optic axis, and any plane containing the optic axis and perpendicular to the face of the crystal is known as a principal plane. B Fic. 285 Fic. 286 Of the two rays into which the entrant ray is divided, that ray KL more refracted from the original direction is known as the ordinary ray, the ray less refracted, KM, being the extraordinary ray. On emergence both rays are found to be plane polarized and in directions at right angles to each other. Thus as illustrated the extraordinary ray vibrates in the plane of the paper, the ordinary ray vibrating at right angles thereto. In 1829, Nicol? published a paper, ““On a Method of so far increasing the Divergence of the two Rays in Calcareous Spar that only one Image is seen at a Time.” The means he adopted was the total reflection of the ordinary ray within the crystal, obtained as follows :— Let ABCD, Fig. 286, represent a section through a crystal of Iceland spar divided* along B D, and let the two parts into which the crystal is divided be united by a transparent cement, such as Canada balsam. Now the index of refraction of the ordinary ray is 1-658, and that of the extra- ordinary ray is 1-486. That of Canada balsam is 1:55. Hence when the ordinary ray K L meets the film of balsam it is reflected in the direction L N, and if the dimensions of the crystal, and the angle of incidence of the beam of light be properly selected, it will pass out through the upper face of the crystal and be lost when the exterior surface is blackened. ©The extra- ordinary ray K M passes through the balsam with small change of direction _ “The means adopted by opticians are either sawing through the prism with a copper wire and emery, or grind- ing away one half of the prism. Splitting is a process not employed. ee ee a ee THE POLARIMETER 475 and emerges as plane polarized light vibrating in a direction perpendicular to the principal plane of the nicol.* In the natural rhomb of Iceland spar the angles B A D and BC D are 71°. As constructed by Nicol, these angles were cut down to 68° so as to obtain such an angle of incidence as to eliminate the ordinary ray. This construction was afterwards altered by Nicol himself* and by many physicists. Thus, Hartnack and Prazmowski’ first suggested that the prism should be sawn from a large crystal of spar, and that to it a rectangular section should be given. Later developments are due to Soleil,? Thompson,® Glan,!°, Lippich,4 Glazebrook!? and Feurstner,!* the two last mentioned having given very complete mathematical analyses of the passage of light through the prism. Of the various suggestions, that independently made by Thompson and by Glan and a form due to Lippich are now used. The Thompson-Glan combination consists of a right prism with vertical end faces, so cut that the optic axis is parallel to the plane of section. The Lippich prism is cut so that the optic axis is perpendicular to the axis of length, but has no relation to the plane of section, though usually perpendi- cular thereto. Prisms of the above construction are shown in perspective view in Fig. 287. With these prisms a wider pencil of light can be admitted, combined with total extinction of the ordinary ray than can be obtained in the original form; at the same time loss of light by surface reflection also disappears. ee Fic. 288 Passage of Light through two Nicols.—Let there be two nicols, P and A, Fig. 288, with monochromatic light passing in the direction indicated. The prism next the source of light is called the polarizer, and the one that receives the polarized ray is the analyser. Let the prisms be so arranged that their principal planes are parallel. Then the emergent ray of light from P will fall on A in a direction parallel to the optic axis, and the extraordinary ray will emerge with its direction substantially unchanged and the quantity of light passing will be a maximum. Let A now be rotated through a nght angle so that its principal plane is perpendicular to that of P. The vibrations of the extraordinary ray now are perpendicular to the optic axis of A, and no light passes, and the eye of an observer looking through A towards P receives the impression of total darkness. These two positions are referred to as parallel and crossed nicols respectively. Now between the nicols P and A set as crossed nicols let an optically active material be introduced whereby the plane of rotation of the light emergent from P is rotated. Light will now reach the eye of an observer, and to again obtain the position of total darkness the analyser 4 must be rotated through an angle equal in magnitude and opposite in sign to that through which the plane was rotated by the optically active material. By * It is evident that that part of the prism remote from the face at which light enters could be substituted by a glass prism of suitable refractive index. For prisms constructed of a combination of glass and Iceland spar see Jamin‘ and Sang.£ 476 | CHAPTER XXIV attaching a pointer and circular scale to A this angle can be measured, giving means to determine an unknown concentration of active material when the rotation for one known concentration has been obtained. This combination of two nicols serves to fix the position of the plane of the polarized light emergent from P and also to determine the rotation produced by an active material. It thus forms an elementary type of polarimeter, in which the critical position is that of total darkness. White and Monochromatic Light.—-In the discussion immediately above light qua light was mentioned. The statement therein made refers only to a beam of monochromatic or homogeneous light. White light is not homo- geneous, but is composed of the spectral colours red, orange, yellow, green, blue, indigo, violet. These components are rotated differently, and hence when an active material is interposed between two nicols, no position of total darkness obtains, since a position crossed with reference to one spectral colour will permit light from all the others to pass. Consequently, on the rotation of one of two nicols, between which is interposed an active material, through which passes a ray of white polarized light, the eye receives in suc- cession the sensation of all the colours of the spectrum. In such a case, however, the position of total darkness can be restored by the interposition of an active material of opposite sign and of the same rotation dispersion as that of the material undergoing examination. Many textbooks make very confused statements on this matter, and frequently imply that it is the means adopted for obtaining the critical position which determines the kind of light to be used. Actually the de- termining factor is the means adopted for compensation (v. infra.), mono- chromatic light being capable of compensation by a number of means, whereas white light cannot be compensated by analyser or polarizer rotation, but requires special devices. This error is of special occurrence in descriptions of the Laurent apparatus, which has been regularly built for use with white light since 1882.14 Similarly, Wild in 18831° adapted his instrument for the use of white light. Critical, Positions.—The various critical positions that are or have been in use are described below. Mathematical analysis of the devices is not introduced, for which reference to specialized works or to original papers must be made. . Extinction of Extraordinary Ray.—In one particular position of a natural prism of Iceland spar with reference to an incident beam of light the double image does not appear. This position was used by Biot? in the first polari- meter on record as a critical position. Elimination of other than Red Rays.—l{ between two nicols an active material such as cane sugar be interposed, the position of total darkness cannot be obtained when white light is employed as the illuminant. On rotation of one nicol the spectral colours in turn appear. Ventzke,!* in a fundamental paper on sugar analysis, took as a critical position the appear- ance of the red field as matched against a standard cell of iron anilate. Total Darkness.—This position has already been described. It is applic- able (with rotation compensation) only to homogeneous light, and was first used by Mitscherlich.?? THE POLARIMETER 477 Transition Tint—When a beam of white light is passed through an active material, each of the several spectral components is rotated through a different angle, and in a system made up of parallel nicols and interposed active material those rays rotated go° do not reach the eye of an observer. A plate of quartz cut perpendicular to the optic axis and 3°75 m.m. .thick rotates the yellow rays of white light through go°, and the remainder combine to form a peculiar pale rose or lilac tint known as the transition tint. The appearance of this tint forms a critical position. The device used to obtain the tint is the Soleil bi-quartz,1® which is made up of halves of dextro- and levo-rotatory quartz. Such a plate interposed between parallel nicols gives. a uniform field of a pale rose tint. Now let a rotation of x° be introduced. In one half of the field the rotation will be x + a degrees, and in the other half x — a degrees where a represents the rotation due to the quartz. Owing to the different rotations assumed by the components of white light, the colour effect transmitted on either side of the field is different, on one side green rays and on the other red rays predominating. The critical position again appears on the interposition of a rotation of — x°. If the quartz plate were wholly of the same optical activity the transition tint would again appear at the same position, but then there would be no sharp contrast at positions a little removed from the critical position. ACB ‘ © dD, Fic. 289 Half Shadow or Penumbra Devices.*—In Fig. 289, let OA and OB represent the vibration planes of two beams of polarized light travelling towards a nicol prism as analyser. Let OD, OD,, OD,, represent various. positions of the optic axis of the analyser. Thus in the position O D, per- pendicular to OA the analysing nicol is crossed with reference to OA. Similarly in the position OD, all light vibrating in the plane OB is eliminated. When, however, the position OD perpendicular to OC bisecting the angle between the vibration planes is assumed, equal amounts of light are transmitted from either source. By making the angle A O B small, a nicol prism used as. analyser will on rotation through the small angle show three well-defined positions, as indicated in Fig. 290. In position OD, left half dark, right half illuminated ; in position OD,, right half dark, left half illuminated ; in position OD, equal illumination throughout. This last is the critical position, and is one of great accuracy ; it was devised by Jellett?® in 1860, for whom the first half shadow prism was made by Bryson, of Edinburgh, and the first half shadow polarimeter by Spencer, of Dublin. Jellett Half Shadow Device.t+—“ A rhombic prism of Iceland spar, whose: * “ Half shadow ’’ has come into use as the term defining these devices as a slavish translation of the German. ** Halbshatten.” Though clumsy, “‘isophotostatic”” would be a better word. ; . ; T Most textbooks, evidently quoting from the same source of misinformation, describe as Jellett’s aconstruction- quite different from that given by the Irish physicist. They also fail to state that he located the half shadow device in the analyser and not in the polarizer. Jellett’s exact wording is quoted above. 478 CHAPTER XXIV long edges should be of length about two inches, or a little more, is cut by two planes perpendicular to those edges, so as to form a right prism as in Fig.291. This prism is divided by a plane parallel to those edges, and making a small angle with the longer diagonal of the base. One of the two parts into which the prism is divided is then reversed, so as to place the base up- | wards, and the two parts are cemented together as in Fig. 292, with the sur- faces of section in contact and the ends of the prism thus formed are then ground and polished.” Cornu Half-Shadow Device.2°—Cornu applied Jellett’s principle thus. An ordinary nicol prism is divided into two parts following the plane of the lesser diagonals. Each face of cleavage is then ground down 24 degrees, after which the two parts are cemented together. A prism with a half- shadow angle of 5 degrees is thus obtained. FIG. 291 FIG, 292 Schmidt and Haensch Prism,21—The German firm of Schmidt and Haensch have employed a prism made thus. The prism of calc spar is divided into two parts by a plane perpendicular to the principal section. One half only is then treated as in Cornu’s method, after which the three pieces are united and arranged so that the incident light falls on the undivided half. The Laurent Half Shadow Device.?2—The Laurent half shadow polariscope obtains its end point ina manner quite different from the instrument described above. Between the polarizing and analysing nicol of ordinary construction, and close to the former, is interposed a thin plate of active quartz, which is cut parallel to the optical axis of the crystal. A beam of light entering such a plate perpendicular to its surface is doubly refracted into two beams, with vibration planes parallel, and perpendicular to the optical axis. In such a system that ray which vibrates perpendicular to the optical axis has its speed of vibration increased, and the thickness of the plate of quartz is so taken that that ray vibrating perpendicular to the optical axis has gained half a wave length on the wave vibrating parallel to the optical axis at the moment they emerge from the quartz plate. In Fig. 293 let the circle THE POLARIMETER 479 represent the diaphragm opening, covered as to one half by the quartz plate, and let the optical axis of the plate be represented by the line o 0; letoa represent the amplitude of vibration and the plane of polarization of the light coming from the polarizing nicol. On meeting the quartz plate this ray is resolved into two rays, 0 6 and oe, parallel and perpendicular to the optical axis of the quartz plate; on emerging from the quartz plate the ray o e has gained half a wave length on the ray o J, and is now represented by the line od. These two rays can be compounded into the ray o c, precisely as if the field of vision was illuminated by the rays o a and oc, symmetrically arranged with respect to the optical axis of the quartz plate. The effect of this is to obtain a field of vision exactly similar to that described in dealing with the Jellett apparatus. The Laurent half-wave plate may take the form of a central disc or of a ring. In the former method one position of unbalance appears as in Fig. 294, a tripartite field shown in Fig. 295 as unbalanced obtaining in the latter case. Poynting Half Shadow Device.*?—This consists of a plate of quartz cut perpendicular to the optic axis, and of which one half is very slightly reduced in thickness. As a means of obtaining variable sensibility it is suggested FIG. 293 FIG. 294 FIG. 295 that a scheme involving the principle of the Soleil-Duboscq compensator (q.v.) could be used. A simpler means yet consists of a cell filled with some active material, the horizontal depth of which is reduced as to one half by inserting in the cell a thin glass plate. The effect produced by this device is similar to other half shadow contrivances. Horsin-Déon Device.4A—This instrument is of different construction from any of those previously described. The light passes through a Jellett prism, and then through a plate of dextro-rotatory quartz rather more than 4mm. thick; the effect of this is to produce a blue field on the left and a pale yellow field on the right. The compensator is a wedge of levo-rotatory quartz, behind which is placed a disc of levo-rotatory quartz, the effect of which is to produce a final tint rather darker than the sensitive tint of the colour polariscope. The field of view of this instrument in positions remote from the zero position is that one half is colourless, and the other coloured in all colours of the spectrum. Near the zero position the colourless half becomes tinted before the other half loses its colour; at the zero position, the field of view is a uniform field, similar to that of the half shadow instru- ments, The Lippich Half Shadow Device.>—This device obtains its half shadows by the interposition of a small Nicol prism between the polarizer and the 480 CHAPTER XXIV analyser, as shown in Fig. 296.12 The half nicol is so fixed that its edge, ¢, lies in the axial plane of the apparatus, and divides the field of vision into halves. Let the principal sections of the two prisms make an angle with each other. Light passing through the large nicol, a, and through the open part of the field, vibrates vertically to the principal section of that prism. Of the rays that pass through that half of the field covered by the half nicol, only those pass that vibrate vertically to the principal section. A field of vision is thus obtained made up into two halves, in which the planes of polariz- Fic. 296 Fic. 297 ation are inclined at a small angle to each other, and the effect is precisely as described when dealing with the other forms of half shadow instruments. In this instrument the analysing nicol is not set parallel to the polarizing nicol, but makes with the polarization direction of the half nicol a larger angle than it does with that of the large nicol, so as to correct for the absorp- tion of light which occurs in the passage through the small nicol. As in the Laurent instrument, a tripartite field can be obtained by the use of a second half nicol, the appearance of one position of an unbalanced field being shown in Fig. 297. Interference Devices.—In the passage of plane polarized light through certain optical combinations, well-defined visual phenomena due to the interference of light result. These phenomena in combination with polarizer and analyser may be made to fix the position of the plane of polarization. The Savart polariscope?® consists of two sections of calc spar, each 3 mm. Fic. 298 FIG. 299 thick, and cut at an angle of 45 degrees to the optic axis of the crystal. The sections are finally cemented together, so that the principal sections cross at right angles. If this device be arranged between parallel nicols a number of horizontal bands or interference fringes occupy the field, as shown in Fig. 298. When the principal section of the analyser forms an angle of 45 degrees with the crossed sections of the Savart plate, and when the principal plane of the polarizer is parallel with one of the crossed planes, the field of vision is as in Fzg. 299, and this is taken as the critical position. THE POLARIMETER : 481 Crossed spider lines arranged in the instrument aid in giving definition to the critical position. This device is used in Wild’s polarimeter. The Sénarmont polariscope?’ is a composite plate of quartz made up ot four similar right-angled wedges of this material. The wedges are united two and two along their hypotenuses, and are cut in such a manner that light enters and leaves by surfaces perpendicular to the optic axes. Each of the four wedges which make up the plate is opposed vertically and hori- Fic. 300 FIG. 301 zontally by a fellow-wedge of opposite optical activity. When mounted between two nicols interference bands are seen. With parallel nicols the bands take the form shown in Fig. 300, but in all other positions the lines in the upper and lower parts of the field are not continuous, as in Fig. 301. This device is used in an instrument of Trannin,?* and in another by Duboscq and Duboscq.*® Compensation.—By compensation in polarimetry is meant the means adopted to restore the plane of polarization to that originally occupied at zero of the scale connected with the compensation device. Rotation compensation.—The most direct, accurate, and simple means of compensation lies in rotation of the analyser (or polarizer) through an angle equal in magnitude but opposite in sign to that through which the plane has been rotated by the active material whose rotation is being ob- served. This means is used in those instruments which employ mono- Pdi Fic. 302 Fic. 303 chromatic light, but is inapplicable to those using white light unless the rotation to be measured is very small. The analyser is the element usually rotated, and to it is attached an alidade moving over a graduated circle, whence is read off the rotation required to effect compensation. Introduction into Field of Opposed Rotation.—This means is used in the quartz wedge compensator of Soleil and Duboscq®®. It consists of a device whereby a variable thickness of active quartz may be interposed and a 2K 482 CHAPTER: XXIV rotation, equal in magnitude and opposite in sign to that due to the active material, introduced, so that the critical position again appears. It consists, Fig. 302, of a plate of levo-rotatory quartz, c, and of two wedges of dextro- rotatory quartz, a and b. By means of a rack and pinion gear, one of the wedges is capable of being slid past the other, so that the combined thickness of the system is capable of being varied. On the moving wedge is fixed a scale graduated in single degrees from 30 to 105°, and on the fixed plate of quartz is mounted a vernier. When the scale is at zero, the combined thickness of the dextro-rotatory wedges a and 6 is equal to that of the levo-rotatory plate c, so that the effect of the system is zero. By sliding the scale towards the roo-point, a diminished thickness of dextro-rotatory quartz is introduced, so that the effect of the system is levo-rotatory, and, in instruments designed for sugar analysis, at the 100-point exactly neutralizes the rotation produced by the normal weight of sugar dissolved in roo c.c., and observed in a 20 cm. tube*. The double compensator is a development of this device. In this arrange- ment two sliding wedge compensators are fitted to the instrument. The milled head controlling one is coloured black, and the other red. The observation is made in the usual way with the black compensator. The active solution under analysis is then removed, and neutrality obtained by adjusting the red compensator. The readings on the red and black scales should be identical, practically demonstrating the accuracy of the reading, for it is very unlikely that an identical error should be made twice running, or that both compensators should possess the same error in construction. The arrangement of the wedges is shown in Fig. 303. Saccharimeters are usually only provided with a scale reading to —30° ; with this device, by setting the zero of the red scale to the right, negative readings of any value can be obtained. In instruments with single wedge compensation, negative readings of magnitude greater than the scale permits may be obtained by inserting in the path of the light a known positive rotation conveniently afforded by a quartz plate. It is evident that the validity of this appliance depends on the nearly equal rotation dispersion of quartz and of cane sugar. Equalization of a Fixed Rotation.—Between the polarizer and the analyser permanently set in the critical position is introduced a fixed and known rotation of sign opposite to that of the material being determined. The material being examined is contained in a graduated and telescopic tube the length of which is varied until balance is obtained. The observed length of tube gives data to calculate the rotation of the unknown material reduced to unit concentration and to standard length of tube. This device was used by Jellett®! and by Trannin*®. Optical Arrangements of Saccharimeters.—The arrangements of these instruments from the time of Biot onwards are illustrated in Figs. 304-315. The systems of lenses are not shown so as to avoid confusion. * Tt is somewhat confusing to appreciate the function of the analyser in instruments using the quartz wedge system of compensation. In these instruments its function is to obtain a critical position acting in combination with the polarizer. When monochromatic light is used it not only does this but serves as a means of measuring the rotation. Conversely, quartz wedge compensation could be used, if so desired, with monochromatic light. THE POLARIMETER — Ss mS ; TS al C B ema oe FE E r ey, im H G iz = = : ae a ea ang Biabegt © Eig om 484 CHAPTER XXIV Biot.A—P. Mirror affording polarized ray by reflection. A. Bi-refractive achromatized prism compensating by rotation, extinction of the extra- ordinary ray forming the critical position. Fig. 304. Mitscherlich*—P. Polarizing nicol. A. Rotating nicol serving as analyser and compensator, used with total darkness as critical position with monochromatic light and with appearance of red field as critical position with white light. Fig. 305. Robiquet??,—-P. Polarizing nicol. B. Soleil biquartz. A. Rotating nicol serving as analyser and compensator. Used with transition tint as critical position, and with white light. Fig. 306. Soleil-Duboscg.—P. Polarizing nicol. 8B. Soleil biquartz. A. Analysing nicol. C. Quartz wedge compensator. D. Colour compensator consisting of a nicol prism and a plate of quartz. This instrument was designed for white light and used 16-35 grams as normal weight. It was the first instru- ment of a high degree of accuracy. Fig. 307. Soletl-V entzke-Scheiblery—In the hands of German opticians this last instrument took on the arrangements seen in Fig. 308, the only changes being the position of the colour compensator and of the normal weight to 26-048 grams. Jellett.A—P. Polarizing nicol. E. Levo-rotatory material of known rotation. . Graduated telescopic tube to contain sugar solution, the adjust- ment of the length of which serves to compensate the rotation due to E. A. Analysing half shadow prism. White light was used with this instrument. Fig. 309.. Wild**,—P. Polarizing prism also serving as compensator by rotation. G. Savart polariscope. H. Crossed spider lines. A. Analysing nicol. This instrument was designed originally for monochromatic light and by the addition of the Soleil-Duboscq compensating system becomes adaptable for white light.1* The normal weight is Io grams. fF7g. 310. Cornu®®.—P. Half shadow prism. A. Analysing prism also serving as compensator by means of rotation. Designed for use with monochromatic light and 16-35 grams normal weight. Fig. 311. Precisely as the Soleil-Duboscq instrument with a changed normal weight became in the hands of German firms, the Soleil-Ventze-Scheibler, so this, with the additional change of the quartz wedge compensating prism, became the standard design of German houses. Laurent”®.—P. Polarizing prism, in the older designs Foucault’s modifica- tion of the nicol being used. J. Half wave plate of quartz. A. Analysing nicol serving as compensator. In this instrument the half shadow angle is capable of adjustment by rotation about its longitudinal axis with variation in the sensibility and amount of light admitted. Many instruments are sent out with quartz wedge compensation system in addition to the compen- sating analyser. Fug. 312. Trannin®8.—P. Polarizing prism. J. Sénarmont polariscope arranged at zero of scale so as to be out of adjustment equal to the rotation produced by ro cm. layer of a Io per cent. sugar solution. F. Telescopic graduated tube serving as compensator through adjustment of length. Fig. 313. Duboscq and Duboscq?®.—P, Polarizing nicol. J. Sénarmont polariscope. C. Quartz wedge compensator. A. Analysing nicol. Fg. 314. THE POLARIMETER 485 Lippich—P. Lippich modification of nicol prism. KA. Half prism serving to give half shadow. C. Quartz wedge compensating system shown as a double system. A. Analysing nicol. Fig. 315. . Adjustable and Fixed Half-Shadow Angles.—In the original types of polarizer the half-shadow angle is fixed, and generally lies between 5° and 8°. Jellett himself in the first half-shadow analyser used a 7° angle. The instru- ment of Laurent is sent out with an arrangement such that the angle can be varied, and the same is true of instruments designed for general use; but apart from the Laurent type, sugar instruments have usually a fixed angle. The advantage of the variable angle is that with light-coloured solutions a small angle and low intensity of light can be used giving superior sensibility. With dark solutions and a greater angle more light can be transmitted, facilitating their observation. Landolt* asserts that with technical instruments a fixed half-shadow angle should be employed, since with every change of angle there is a change in the zero which requires adjustment. While this reasoning may be correct with regard to chemists of a certain mental type, it is quite inapplicable te others of a superior intelligence. The instrument of Bates** as built by Fric, is provided with means to vary the half shadow dependent on the colour of the solution under analysis and this with automatic adjustment of the change in the zero. Source of Light used in Polarimetry.— Measurements of academic interest are always made with monochromatic light. That first used was obtained from a bead of a sodium salt incandescing in a bunsen flame; such light is not spectrally pure and a closer approximation to homogeneity is obtained by filtration through a cell of potassium bichromate, to which Landolt** later added a cell of uranous sulphate; such measurements are referred to as [a]. More recently measurements are made with spectrally pure light obtained by passing the light from a mercury vapour lamp through a prism. Such measurements are referred to as [a],,. Although homogeneous light may be, and is, used in saccharimetry, it is more convenient to employ white light and such light before use should be filtered through a cell of potassium bichromate such that percentage of salt « length of cell in cms. equals 9. Such light has a mean wave length of 600 pp and to it the roo-point of the sugar scale is referred. Error may be introduced by neglect of filtration, and, for example, Schénrock%? found a rotation of Ioo-12 with unfiltered as compared with roo for filtered light. The difference varies with the eye of the observer and is probably connected with the pigmentation of the eye. The actual light used may be a flat-wick kerosene lamp, a fish-tail coal gas or acetylene burner, the Welsbach mantle or any form of electric light. The writer prefers a concentrated filament nitrogen-filled tungsten light of 50 c.p. The Welsbach and electric light require the interposition of a dis- persing surface to eliminate the image of the mantle or filament. Ground glass is usually employed, and in its absence colourless transparent paper, which may even be represented by a grease spot, serves well. In instruments of German design the light filter is inconveniently placed within the instrument and difficult of access. It should be located without the instrument, and between it and the source of light. It may be carried on an extension rod or on a separate stand. Noobjection lies to its replacement by a glass light filter giving a light of the same wave length as that specified. 486 CHAPTER XXIV Polarimeter Tubes.—The older form of polarimeter tube is shown in Fig. 316. It consists of a glass or metal tube with the ends ground exactly flush and parallel. On either end a screw thread is cut. To fill the tube, a glass disc is placed on one end and secured by the cap. The tube is filled in a vertical position and the second glass disc slid over the end and the emergent Fic. 316 meniscus, avoiding the formation of an air bubble. The disc is then secured in position by a second cap. A second form of tube, Fig. 317, uses sprung metal caps for securing the glass discs in place. The latest form of tube, Fig. 318, has an enlarged end into which an air Fic. 317 bubble may be directed, outside of the field of vision. This form is very convenient since, when making a series of observations, the tubes may all be placed in a row with the enlarged ends together ; if the tubes be systemati- cally reversed when read, the observer knows the one last read in case of interruption. Fic. 318 Another form, Fig. 319, eliminates the annoyance of the air bubble by means of a cavity blown in the glass. It also affords means for the identifica- tion of a particular tube in a series. This tube rests on shoulders and not on the caps, a method due to the U.S. Bureau of Standards?’. The Laurent instruments are supplied with bayonet-fastening spring caps. Fic. 319 The continuous tube of Pellet®* is a great time-saving device. One method of using the tube is shown in Fig. 320. The material under examina- tion is poured into the reservoir a, whence it flows through the tube displacing material already contained therein. By mounting a T-syphon, 8, as in- dicated at the delivery end, the flow automatically stops when the level c is reached. This appliance is most useful when many consecutive readings on materials of about the same density have to be made. In fitting up the THE POLARIMETER 487 appliance, it is convenient to arrange a cradle alongside the trough of the polarimeter to hold the Pellet tube whenever an ordinary tube is brought into use. The tubes used for materials when temperature contrcl is important, as in the reading after inversion, are water-jacketed and are supplied with a tubulure for the insertion of thermometer and stopper, as indicated in Fig. pau, Tubes are found made of both glass and metal. The former must be FIG. 320 used for acid materials and is preferable on the grounds of smaller expansion. In addition, metal tubes may become bent, due to rough use, without the damage being observed. The life of a glass tube is shorter than that of a metal tube, but fracture is only due to avoidable carelessness. Polarimeter tubes are supplied in lengths of 2.5 cms., 5 cms., IO cms., 20 cms., 22 cms. (for elimination of calculation in certain routine dilutions) 40 cms. and 60 cms. The Laurent instruments are usually built to accom- modate, and are supplied with, a 50-cm. tube. The diameter of a tube should be larger than that of the diaphragm through which the pencil of light passes, so as to avoid depolarization due to internal reflection, and the glare which accompanies a tube of smaller diameter. Bates adopts 9 mm. as a convenient diameter. Fic. 321 jvw Convenience in Observation.—A dark room, or cabinet enclosing the instrument, with source of light located externally is usually advised. In place thereof the writer finds the use of a shield of the form shown in Fig. 322 very effective to cut off extraneous light. Polarimeter Seale.—The scale of the polarimeter is usually mounted on the moving wedge of the compensator. The vernier is stationary. The scale is either made of some alloy as nickelin, the expansion of which is low, or of invar, the expansion of which is zero. In some patterns the scale is 488 CHAPTER XXIV made of glass, and in others it is engraved on the quartz wedge. The appear- ance of the scale is as in Fug. 323, where the reading is 26.7. Control of the Seale.—Quartz plates, the exact value of which has been determined in sugar degrees, may be obtained from makers. These plates are standardized at 20° C. in Europe, and as they are equally affected by variation of temperature with the quartz wedge, they will serve at any tem- rile Bo so | Wr! FIG. 322 FIG. 323 perature to control the scale of a polarimeter of this type; but, if used to control the scale of a polarimeter compensating by rotation of the analyser, the correction for temperature must be applied. A control observation tube by Schmidt and Haensch is shown in Fig. 324 ; it consists of an outer tube, T, in which is moved by means of a rack- and-pinion gear the tube f, fitting closely into T, exit of liquid between T and f being prevented by the washer e: the tube fis closed by a glass disc atc. The solution to be used for testing is poured into the funnel a, whence Fig. 324 it fills the tube JT, The distance between d and ¢ is regulated by the rack- and-pinion gear, the exact distance and also the length of the column of liquid being read off a scale carrying a vernier; the tube is conveniently filled with a solution of the normal weight of sugar in 100 cc. ; with a column of liquid 20 cm. long a reading of 100 should be obtained, and other readings should be proportional to the length of the column of liquid. A very rapid control over the scale can thus be obtained. Of course, the scale can also be tested by polarizing different weights of pure sugar in a tube of constant length, but this, compared with the adjustable control tube, is a laborious operation. THE POLARIMETER REFERENCES IN CHAPTER XXIV. Phil. Trans. Roy. Soc., 1818, 125. An. Chim. Phys., 1840, 74, 428. : Edinburgh New Philosophical Journal, 1829, 6, 83. Edinburgh New Philosophical Journal, 1831, 14, 372; 1839, 27, 332. G.R:, 1869, 68, 22t. Proc. Roy. Soc., Edin., 1891, 83, 323. Repertorium fir physikalische Tecknik, Carlsberg, 1, 325; 2, 217. C.R., 20, 1805. Phil. Mag., 1881, 12, 340. Repertorium fiir physikalische Tecknik, Carlsberg, 16, 570; 17, 195. Zeit. fiir Instr., 1892, 2, 167; 1906, 14, 326. Phil. Mag., 1883, 15, 252. Zeit. fiir Instr., 1894, 4, 41. C.R., 94, 442. St. Petersburg Academy, Scientific Bulletin, 1883, 28, 407. Erdmann’s Journal fiir practische Chemie, 1842, 25, 65. Lehrbuch der Chemie, 1844, 3, 36. C.R., 1845, 50, 105. Proc. Roy. Irish Academy, 1863, 7, 348. Bull. Assoc. Chim. Suc., 1870, 14, 140. “Optical Rotation of Organic Substances.” C.R., 86, 662; 89, 665. Phil. Mag., 1880, Io, 18. Bull. Assoc. Chim. Suc., 1902, 19, 601. Zeit. fiiy Natuurwissenschaft, 30, 45. Poggendorf’s Annalen, 1840, 49, 292. An. Chim. Phys., 1857, 50, 480. Assoc. Frangaise pour l’Avancement de Science, 1885, 105. Jour. de Phys., 1886, 5, 274. GAR; “49,2485 Proc. Roy. Irish Academy, 1864, 8, 279. “Optical Rotation of Organic Substances.” Poggendorf’s Annalen, 1864, 122, 626. “Optical Rotation of Organic Substances.” U.S. Bureau of Standards, Bull. 44. Zeit. ftir Instr., 1892, 2, 340. Zeit. Ver. deut. Zuck., 54, 521. Bull. Assoc. Chim. Suc., 1892, 551. 489 CHAPTER XXV THE DETERMINATION OF CANE SUGAR AND THE ASSAY OF SuGAR HousE PRODUCTS THE routine analyses necessary for the control ot a cane sugar-house com- prise the determinations of :—Specific Gravity, Soluble Solids, Water, Polarization, Sucrose, Reducing Sugars, Fibre, Ash, Acidity and Alkalinity. Other specialized determinations are mentioned separately. The bearing of these determinations on the control and other inter-relations is discussed in this chapter, together with the means adopted for their execution. Specific Gravity, Degree Brix, Soluble Solids, ete.—The specific gravity, or density, of a material is used for determining the solids in solution referred to a sucrose-gravity basis. Thus a 16 per cent. solution of sucrose in water, as determined at 20° C. and compared with water at 4° C. as unity is of specific gravity 1-06346. A sugar-house material of this specific gravity is said to contain 16:0 per cent. soluble solids, or to be of 16-0 degrees Brix.* Other synonymous terms are fofal solids and apparent dry substance. The writer has used the term gravity solids, as thereby confusion as to the basis of reference is avoided. In place of deducing the apparent dry substance from the specific gravity, the refractive index has also been used. Thus the refractive index at 28° C. compared with water at 28° C. of a 16 per cent. solution of sugar is 1-3562, and a sugar-house material with this refractive index is said to have 16 per cent. apparent dry substance, or totalsolids. The term used by the writer is refractive solids, and the expression optical solids is alsoin use. The intro- duction of this method is due to Main.! The real dry substance in solution is determined by drying to constant weight. The results of determinations made in this way are referred to as total solids, true total solids, or dry sub- stance. The term used by the writer is absolute solids. The relation between the three bases of comparison is as under :— Gravity solids > Refractive solids > Absolute solids, and the difference is found to increase with the quantity of non-sugar, particularly salts in solution. Reducing sugars have almost the same solution factor as cane sugar, and the difference is not great for other organic bodies which occur in sugar-house materials. : * Brix is the name of the German chemist whose determinations of the relation between sugar per cent. and specific gravity of solutions are generally accepted. Previously the degree Balling, named after an Austrian chemist, was used. The principle involved is the same and the differences are very small. In France the degree Vivien is used. This gives, referred to a sucrose basis, the grams soluble solids per 100 c.c. of material. Hence Degrees Brix x Specific gravity = Degrees Vivien. 490 THE DETERMINATION OF CANE SUGAR 491 The definition of the gravity solids, or degree Brix, or of the refractive solids, presents no difficulty when the material is examined in its original condition. If the bodies present, other than sugar, gave the same relation between dilution and specific gravity as does sucrose, the dilution at whicha determination is made would be a matter of indifference. On experiment, however, the following relation? is found to hold for impure solutions :— If from an impure sugar solution containing q per cent. gravity solids, or refractive solids, dilutions be made containing Q, per cent., Q, per cent., etc., of the original material, and if these solutions contain q, per cent., 2 per cent., etc., gravity or refractive solids, and if Q; > Q2 > Qs, then :— On the other hand, the absolute solids are independent of dilution, as are also the gravity and refractive solids of solutions of cane sugar. This follows from the definition. The gravity solids and refractive solids in a solid or in a semi-solid solution can only be obtained after a controlled dilution, and, following on the above statement, different results will be obtained dependent on the dilution. Experiments made by the writer gave the results tabulated below. The method of calculation used was as follows :—A syrup was of density 1-35643 at 27°5° C./27-5° C.; it thus contained 71-290 per cent. gravity solids ; a 63-701 per cent. solution of this syrup was of density 1-206798 at 275° G. /27-5°C. and hence contained 45-609 per cent. gravity solids. Calculated back, the original material contained (45-609 /63-701) * I00 = 71:598 per cent. gravity solids. The variation in the degree Brix, or gravity solids, and of the refractive solids in a raw sugar, a syrup and a molasses, as affected by dilution, is shown in the following tables. in ‘‘ SOLIDS’’ IN A RAW CANE SUGAR WITH DILUTION AS CALCULATED FROM THE OBSERVED SOLIDS AT THE STATED DILUTION. VARIATION THE RAw SUGAR CONTAINED 99 ‘005 PER CENT. ABSOLUTE SOLIDS, 96 -30 PER CENT. SUGAR, AND 0°55 PER CENT. ASH. Raw Gravity | Refractive} Calculated | Calculated | Absolute | Absolute Sugar per | solids per | solids per gravity refractive | solids per | solids per cent. in cent. of | cent. of solids per | solids per cent. of cent. of solution. solution, | solution. cent. of cent. of solution. | raw sugar. raw sugar. | raw sugar. 100 ‘000 -- — + — 99 *005 99 005 67 -418 67 +292 66 -gI 99 814 99 24 66 +747 = 59 513 59 “413 59 09 99 *832 99 *27 58 921 " 48 +500 48 +529 48 +26 99 *854 99 +30 48 -118 i 37 °875 37 834 37 °63 99 *892 99°35 37 *499 n 30°°222 30 -198 39°05 99 *922 99 *43 29 921 , 22-994 22 ‘804 22 -89 99 °957 99°55 22-766 »» 18-131 18 -168 18 -07 100 :208 99 -68 17 ‘950 - 13 490 13 +562 13°46 100 *534 99 ‘80 13 *356 r 9 °944 10 -043 9°94 100 -936 99 °93 9 846 5 835 5 *949 5°85 TOI +799 100 +26 SEIT » 3 °850 3 °930 3°87 102-401 100 +53 3 812 492 CHAPTER XXV VARIATION OF ‘‘ SOLIDS’”’ OF A CANE SYRUP WITH DILUTION AS CALCULATED FROM THE OBSERVED SOLIDS AT THE STATED DILUTION. THE SYRUP CONTAINED 69-233 PER CENT. ABSOLUTE SOLIDS, 60°44 PER CENT. SUGAR, AND 1:73 PER CENT. ASH. Syrup Gravity per cent. solids per in cent. of solution. solution. 100 -000 71 +290 90 -834 64 824 77-141 55 °442 63 +701 45 609 48 -120 34 °513 38 °547 27 679 25 *909 18 -665 13 °334 9 641 8 -108 5 997 4 685 3 482 3 ::258 2°472 Refractive solids per cent. of solution. 79°35 64 °05 54°52 45°13 34 "12 27°37 18 +41 9 +52 6 86 3°38 2°40 Calculated gravity solids per cent. of 71 +290 71 *365 71 °473 71 +598 71 °723 71 :806 72 °040 72 °393 73 ‘960 74 °322 75 °899 syrup. Calculated | Absolute refractive solids per cent. of 12.29 solids per cent. of solution. *233 *887 *407 “102 “314 687 "938 Q °232 5 “613 3 °243 2 +256 Absolute solids per cent. of syrup. 69 +233 VARIATION OF ‘‘SoLIps’’ oF A MOLASSES WITH DILUTION, AS CALCULATED FROM OBSERVED SOLIDS AT THE STATED DILUTION. THE MOLASSES CONTAINED 76-630 PER CENT. ABSOLUTE SOLIDS, 31 ‘QI PER CENT. SUGAR, 16°43 PER CENT. REDUCING SUGARS, AND II‘I3 PER CENT. Molasses Gravity | Refractive} Calculated per cent. solids per | solids per gravity in cent. of cent. of | solids per solution. solution. solution. cent. of molasses. 100 -000 84-040 50 +O 84 *040 92 354 77 °902 a: 84 +460 _ 88-079 73°778 a 84 +736 84-180 71 +558 -- 85 :025 77 :042 65 +700 — 85 278 70 -188 60-118 -— 85-653 63 ‘019 54°12 55:0 85 -866 54 °317 47 ‘100 a 86 709 46 +473 40 ‘170 = 86 +438 39022 | 33-923 = sae 30 894 27 291 = 87 +338 23 696 20 +826 19 +43 87-973 16 +568 14 *663 S08 88 +501 13 ‘167 II -674 10 +30 88 -739 7 034 6-261 5°85 89 -O14 3 467 2 +998 2 +83 89 +390 Calculated | Absolute refractive solids per cent. of molasses. 80-0 solids per cent. of solution. “630 ie “494 "997 °037 *785 *291 -624 ‘612 *309 "674 "158 -696 :080 2399 2-656 ASH. Absolute solids per cent. of molasses. 76 -630 Purity.—By the expression “‘ Purity ”’ is meant the value of the expression Depending on whether the Polarization or the sucrose per cent. is used as the numerator in this ex- pression, and whether the solids are absolute, gravity or refractive, six values (Sugar per cent./Solids per cent.) x 100. THE DETERMINATION OF CANE SUGAR 493 < > may be found. Generally the term “ purity’ without any qualification is taken to mean the ratio (Polarization/Gravity solids) x 100. This expression is often further identified by the use of the adjective apparent. The ratio (Sucrose per cent. /Dry Substance) x Ioo is usually termed the true purity or real purity. The writer uses the terms gravity purity, refractive purity and absolute purity when referring to determinations of sucrose, qualifying these expressions with the term folarization when the sucrose per cent. is not determined. The apparent purity is thus equivalent to the polarization gravity purity and the true purity to the absolute purity. Following on the results quoted in the preceding section, the gravity and re- fractive purities will vary with the dilution at which the observations are made. This point is of importance in the calculation of the available sugar. Fic. 325 “Fic. 326 Determination of the Specific Gravity or Degree Brix.—Three methods are in use :—x. Direct comparison of the weight of the material with the weight of an-equal quantity of water. 2. Comparison of the weights of a substance when weighed in water and when weighed in the material. 3. By observa- tion of the position of equilibrium of an empirically graduated instrument called an hydrometer, when immersed in the material. I. This method is carried out with the pycnometer, or specific gravity bottle, shown in Fig. 325. The weight of the bottle when clean and dry is obtained. It is then filled with distilled water, the ground glass stopper is inserted, and the excess water forced out through the side tube. It is well to reduce the temperature of the water, or other material, below the tem- perature at which the observation is to be made. On gradually reaching this temperature, a little liquid will exude from the side tube, which may be removed with a piece of absorbent paper. The cap is then placed on and, after wiping dry, the weight of the bottle and water is obtained, whence follows the weight of water contained at a definite temperature. A similar 494 CHAPTER XXV process gives the weight of an equal volume of the material being examined, when the specific purity follows by a simple division, the degree Brix being obtained from reference to tables. In very exact work all determinations should be made at one fixed temperature, now selected as 20° C. As this is inconvenient in rapid technical work in the tropics, the writer worked as follows :—The mean temperature of a laboratory was 27:5° C. The weight of water in the pycnometer was determined for each tenth degree between 25° C and 30°C. The weight of the juice or other material was determined at whatever tempera- ture obtained at*the time of the determination, and was compared with the weight of water at that temperature. The corresponding degree Brix was then taken from a table calculated for 27°:5° C/27-5° C. The error intro- duced by accepting an equal expansion for water and sugar solutions between these limits does not appear till the third decimal place in the degree Brix. 2. A weight is suspended by a thread of silk from the end of an arm of the balance. Its weight is observed in air, in water and in the material under examination. If x, y, z be the weights respectively in air, water and Vd ae 8 C = ed WA Se a OH chs || ( if It ry ¥y abe = FIG. 327 Fic. 328 material, the specific gravity of the last is given by the ratio —. This method may be employed on any balance as in Fig. 326, or the specially designed Mohr-Westphal balance, Fig. 327, whereby the specific gravity is read directly from the rider weights used, may be employed. 3. The hydrometer, Fig. 328, consists of a glass tube on which is blown an elongated bulb. Beneath this bulb is a second loaded with lead shot or quicksilver. The upper portion consists of a slender stem, in which is located the scale. When immersed in a liquid, the instrument will sink, or float with THE DETERMINATION OF CANE SUGAR 495 some portion of the stem above the level of the liquid. The Brix hydrometer, which is generally used, is so constructed that the degree indicated at the point where the level of the liquid cuts the stem indicates the solids in solution referred to a sucrose basis. The principle of graduation of the hydrometer is as follows :—The weight of liquid displaced by the floating instrument is equal to the weight tN Tih ce il Fic. 329 of the instrument. Let w be the weight of the hydrometer and let v be the volume of the portion immersed. Then d=w/v where d is the specific gravity of the solution, and v=w/d. For a series of specific gravities, 0, =, /d,, Ve = We/do, V3 =Wz/d, and if di, —d,+c=d,+2c etc. where c is small v, =v, + * =v 3 + 2x nearly. Hence, for a restricted range the scale on the spindle will be divided into equal portions for each increment in specific gravity or for each degree Brix. 496 CHAPTER XXV It further follows that the delicacy of the instrument depends on the cross section of the stem, or rather on the relation between cross section of stem and volume displaced by the bulb. The smaller the cross section, the longer will be the division corresponding to each difference in specific gravity, or degree Brix. In making the determination, the approximate degree Brix is found. The instrument is then removed and the stem wiped dry. It is then im- mersed in the liquid a very short distance below the approximate degree already observed, allowed to come to rest and the reading again observed. The position observed is the actual level of the liquid and not the level of the meniscus which forms on the stem. A simultaneous observation of the temperature is made and the appropriate correction added or subtracted. For certain purposes a greater degree of refinement than is obtainable as described above is necessary. With this object in view, the writer has — devised the following arrangement, Fig. 329. The cylinder in which the hydrometer floats is provided with a flared-out upper portion. In this is located an interior overflow controlled by a cock. By filling with liquid above this overflow, and allowing the excess of liquid to escape slowly, a constant level can be obtained. The scale of the instru- ment is read, not at the level of the liquid, but at a known distance, con- veniently 1° above this level. One device for obtaining this end consists of a vertical piece of glass with a horizontal scratch opposite to a mirror. This arrangement is carried on a horizontal holder capable of vertical ad- justment, and is adjusted until the scratch is exactly 1° above the level of the liquid.* The eye of the observer is levelled so that the scratch and its image are coincident, the point where the former appears to cut the scale being taken as the reading. This can be estimated to 1/100 of a degree and repeated readings to this accuracy can be obtained. The holder also carries three horizontal pointed screws which, when adjusted to a certain point, restrain the instrument in a central position without interfering with its freedom of vertical motion. A portion of the holder is hinged and swings out in a horizontal plane so as to permit of removal of the instrument. The appliance is provided with a charging container filling the cylinder from below, with a discharge cock and with level screws. Since hydrometers are seldom accurate to less than 0-05 Brix, that one selected for use with this device must be accurately standardized with the pycnometer. This is best done by ascertaining the degree Brix of the solu- tion used with the pycnometer and adjusting the level of the scratch until it indicates exactly 1° too little. The hydrometers found in use are standardized as correct at 17°5° C. or 27:5° Ct: that is to say, they indicate the degree Brix correctly at these temperatures. The necessary corrections to be applied when the liquid is at another temperature are given in the Appendix. When the hydrometers are standardized at either 17*5° C. or 27°5° C. the writer understands that the specific gravity of water at these temperatures is taken as unity. The general feeling of chemists is to abandon all these standards and to adopt a temperature of observation of 20° C. compared with water at 4° C., but the writer has seen no spindles based on this system yet in use. * Alternatively, specially graduated hydrometers incorrect when referred to the liquid level may be used. + The complete apparatus, termed a “‘ Brixometer,” is sold by the Sugar Manufacturers’ Supply Co., Ltd., 2 St. Dunstan’s Hill, London, E.C.3. { French practice stil] retains 15.6° C. as a basis of reference. In the British West Indies 84° F. is used. THE DETERMINATION OF CANE SUGAR 497 Brix spindles, as purchased from reliable dealers, are generally of con- siderable accuracy. Nevertheless, each instrument should be standardized. This is most readily done by reserving one special set as a carefully checked standard against which newly purchased instruments can be compared. Special Points in connection with Sugar House Products.—Raw juices from the mills carry in suspension much solid matter and are also emulsioned with air. As a preliminary, they should be strained through gauze, allowed to stand for some time to allow the heavy particles to subside and the air and lighter solid particles to rise.. The intermediate portion may then be drawn off into the cylinder in which the observation is made. A vessel with a cock located about two inches from the bottom is convenient and this vessel should contain two to three times the volume of the cylinder. Molasses and massecuites cannot be observed directly. The usual convention for process control is to dilute with an equal weight of water, observe the Brix of the diluted material and multiply by two. This determination is of sufficient exactitude for controlling the manufacturing processes, but it does not give exact data to determine the “‘ weight per cubic foot.” When the density of the undiluted material is required, the following procedure may be adopted :— A large wide-mouthed vessel of the shape shown in Fig. 330 is constructed of copper or brass, or even a wide-mouthed bottle may be employed. The mouth of the vessel is best formed sloping inwards, so that a stopper may be ground accurately to fit this mouth. Through the centre of the stopper is bored a hole about 3-in. in diameter. Massecuite from the pan is allowed to flow into the vessel until about seven-eighths full ; the vessel is then allowed to cool until it has reached the temperature at which the factory measurements of massecuite Fic. 330 are taken, and the weight of massecuite determined. Water is then carefully poured over the surface of the massecuite till the vessel is full, the stopper inserted, when the excess of water escapes through the aperture and is wiped off. The method of calculation is shown below :— Grms. Weight of vessel and stupper empty .. =. ae Se 416 *35 - ~ ak me and water a =< “i 2163 -40 a Water <<. es e- ee es e se 1747 05 pe vessel, stopper, and massecuite aie a ate 2645 °95 al massecuite xs ee es a ae = 2229 -60 = vessel, stopper, massecuite, and water .. are 2875 :95 water above massecuite ze These materials are dried before the addition of the sugar material and are treated as a part of the container. Acceleration of the period of drying may also be obtained by drawing a current of hot dry air over, or through, the material. In general, the con- tainers used in water determinations are shallow aluminium dishes, listed by dealers as specially applicable to milk analysis. A formal routine for the determination of water in cane sugar-house products is described below. This routine may be modified by the individual chemist in accordance with the principles discussed above. Sugars of Higher Grade.—Weigh out about 5 grams into a dry container. Keep at 100° C. for 10 hours. Weigh. Replace for one hour. Re-weigh * The extent of this loss was examined by the writer. A waste molasses was exposed for ro hours to a tem- perature of roo° C. A current of dry air, free from carbon dioxide, was drawn over the molasses. The volatile matter given off was passed through calcium chloride to collect the water and through potash to collect the carbon dioxide and volatile acids. Per 100 total loss of weight 98.7 was found as water, 1.0 as volatile acids and carbon ae and 0.3 was apparently lost. With a juice 99.7 was found as water and 0.3 as carbon dioxide and volatile acid, . 500 CHAPTER XXV and repeat until consecutive weights do not vary. Vacuum drying is ad- missible, but unnecessary. Where results of less exactitude are required for immediate use, the drying may be carried out at 110° C. Sugars of Lower Grade.—As for higher grade sugars, with the obligatory use of vacuum drying at low temperatures. Massecutte, Molasses, Juices.—In a flat shallow container, place about Io grams of some absorbent material, such as pumice stone, quartz sand, or filter-paper, then obtain the weight of the container, absorbent material, and stirrer. Weigh into the container the massecuite, molasses or juice. With the first two materials, add sufficient distilled water to dissolve and to distribute over the absorbent material. Dry at a low temperature to constant weight. The necessity for the use of a low temperature is most pronounced with molasses where the proportion of reducing sugars is greatest. Results of reasonable exactitude may be obtained with juices at atmospheric pressure. Alternatively, the following scheme may be adopted :—Fold and crimp a strip of filter paper. Insert this in a stoppered tube, through the stopper FIG. 332 Fic. 333 of which are led two tubes. Dry and weigh the tube and its contents. Weigh and dissolve, if necessary, the material to be dried. Distribute it over the crimped paper. Insert the tube in a bath of boiling water and draw through the tube a current of dry air, until constant weight is obtained. Bagasse.—As shown by Norris’, bagasse may be dried at a temperature of 130° C. with so small.a decomposition as not to affect the value of the results. At this temperature desiccation is complete within two hours, as compared with at least six hours at 100° C. Two very different routines obtain. The method followed in Java and Hawaii entails the use of flat containers in which the bagasse is placed in a shallow layer. These con- tainers, which are from one half to one inch high, and about 20 square inches in area, hold from 20 grams to 50 grams of material. In order to obtain a representative sample in so small a quantity, the original sample must be brought to a fine state of division in a chopping machine. A change in composition during the process of subdividing is inevitable. The other routine is that recommended by Spencer’, and with him the writer is in complete agreement. In this method much larger quantities of material are used, and the analysis is made on the bagasse without any subdivision. The apparatus designed by the writer for the purpose, and THE DETERMINATION OF CANE SUGAR 501 which differs only in details from that employed by Spencer, to whom the routine is due, is shown in Fig. 332. A is a cylindrical container 6 ins. diameter by Io ins. high, provided with a wide flange B at the top and per- forated at the side near the bottom as indicated at C.D is a cylindrical vessel with a flange E corresponding to the flange B. At the bottom of this container is located a hot element, F, which may be either a steam coil, or an electrically heated resistance. The bottom of the vessel D is perforated. Across the top of the bagasse container is laid a cover G, in which is inserted a tube H, allowing of connection to a source of vacuum. The three parts B, E, and G may be drawn together by means of clamps K, and a tight joint secured. On making connection to the source of vacuum, a current of hot air following the direction shown by the arrows is aspirated through the bagasse. The size of container given will hold 1,000 grams of bagasse and drying will’be complete in two hours. Vacuum Oven.—The vacuum ovens usually found in sugar laboratories are essentially of the pattern devised by Carr®. They are obtainable from dealers, but more conveniently and at less cost can be constructed in the field. One made by the writer is shown in section in Fig. 333, while a perspective view is given in 7g. 334. It consists of a piece of 6-inch copper pipe 9 inches long. A chamber 0 is arranged round the pipe, into which is conducted exhaust steam, the condensed water being carried away by the pipe c. The vacuum chamber of the oven is connected to the last cell of the evaporator by a half-inch pipe d. The door of the oven is a stiff iron or steel plate 4, on which is arranged a washer of some soft material such as asbestos packing. The external pressure keeps the door in place and thumb-screws are unnecessary. A pipe g serves to break the vacuum. A vacuum gauge and thermometer are shown at f and e. The arrangements specifically mentioned here may be modified by filling the space between the oven and jacket with water and heating by a 502 CHAPTER XXV flame, instead of using exhaust steam ;-and a water vacuum pump may be used in place of a connection to the evaporator. Determination of Cane Sugar.—The method adopted generally for deter- mining the quantity of sugar present in a material is based on the measure- ment of the rotation of a ray of polarized light. Within the limits specified in detail below, this rotation is proportional to the concentration of the solution through which the ray passes, and to the length of the column of the solution. Hence, if the rotation for any one concentration and for any one length of column be known, an unknown concentration can be estimated when the rota- tion for that concentration and for a known length of column is determined. Specific Rotation—The specific rotation is that rotation expressed in angular degrees when the light passes through a column of length 10 cms. of solution containing one gram in one cubic centimetre. This rotation is referred to some source of monochromatic light, the yellow line of the sodium spectrum or the green line of that of mercury being selected for use. Obser- vations made on these bases are referred to as [a] and [a];,,. Rotations measured with ordinary white light are referred to as [a], (French jaune yellow, referring to the elimination of the yel'ow rays. V. page 477). For convenience of reference, the specific rotations of some important sugars are collected here, where # is the percentage, and c the concentration in grams per I00 c.c. The rotations are referred to [a]> Sucrose® = 66-386 + 0-015035 p — 0:0003986 p*. Sucrose! == 66:438 + 0:010312 p — 0:003545 p”. Sucrosel! == 605520, (1en ¢ —= 26): Glucosel? == 52:50 + 0:018796 p + 0:00051683 p?. Fructosel!® = —/101-38 — 0:56¢ + 0-108 (c — I0)}. I Raffinose 5H,O 4 104°5 [for c = 16-6]. Maltose!® = 140°375 — 0:01837 p — 0-095 #. Lactose!® == 52 e ton t =—20. 6. Mannose!’ == i2ego for t-— 20°C Galactose! = 83-883 + 0-0785 p — 0-209 #. for values p 5 to 35 and# 10° C. to 30° C. Arabinose!® 105*4;for 7 = "18> GC Hylose ; = 18-095 + 0:06986 # for p 3 to 34. extran? ==230: Levulan?? = Zo tO —— 20 cy Xylan”* = 70 to 85. Normal Weight.—-In the process of saccharimetry a certain weight of cane sugar observed in the polarimeter under fixed conditions gives on the arbitrary scale a reading of 100 degrees. This weight is called the normal weight. The original normal weight was devised by Biot,?4 who took as a standard of rotation that afforded by a plate of quartz 1 mm. thick and cut perpendicular to the optic axis. Transformed into sugar terms he found that this rotation was that produced by 16:47 grams of sugar dissolved in Too c.c. and observed in a tube 20 cms. long. In combination with Clerget he reduced this figure to 16:35 grams, a figure for which the older Soleil- Duboscq instruments are graduated. Girard and Lunes?’ found 16- 1g grams, a figure altered to 16-29 grams in the determinations of Mascart and Benard,”® which now is the accepted standard. This weight has always been referred to Ioo metric centimetres. THE DETERMINATION OF CANE SUGAR 503 The German normal weight is due to Ventzke.?’_ In his original publica- tion he compared the polarization of various sugars in 25 per cent. solution, the specific gravity of cane sugar at this point being 1-1056, and defined this as a normal solution. He also used a tube 23-4 cms. long. Later this standard was changed to a sugar solution of density 1-1, with a tube length of 2ocms. This again was referred to weight, the equivalent being 26-048 grams of sugar dissolved in 100 c.c. Originally metric c.c. were specified, but in 1855 with the general adoption of Mohr’s c.c. a change to this standard was made with no change in the weight. The International Sugar Com- mission sitting at Paris in Ig00 recommended a change to metric c.c. and the adoption of 20° C. as the temperature of observation. The normal weight © now became 26-0082 grams, for which 26 grams is substituted. A third normal weight, namely Io grams, is that used by Wild in the few instruments of this type that have come into use. In 1896, Sidersky, at the International Congress of Applied Chemistry, proposed the adoption of 20 grams as a normal weight, and at the Inter- national Congress of 1906, this quantity was specifically adopted as the Inter- national normal weight referred to metric c.c. and a temperature of 20° C.* Unfortunately, however, the exact rotation of cane sugar is uncertain. By definition 26 grams of sugar in I00 metric c.c. observed at 20°C. in a 20 c.m. tube should read 100° on the Ventzke scale. Bates and Jackson?® were the first to challenge this basic standard, and in a research of very great care, conducted at the U.S. Bureau of Standards, they found a value of 9g9°895. A very little later Walker?® in Hawaii confirmed their work, finding a value of 99-86. The result first quoted makes the normal weight 26-027 grams. This value is very appreciably lower than that due to Schénrock on whose measurements of the equivalence of quartz and cane sugar the graduation of all except the French instruments is based. On the other hand, Herzfeld?° has challenged the correctness of the work of Bates and Jackson, so a state of confusion prevails. To remove an element of uncertainty the careful analyst should confirm the graduations of his instrument, and determine at the average temperature of his laboratory what is his proper normal weight. This is the procedure followed by Harrison*! in British Guiana :—“ Each roo c.c. flask in use for sugar polarization is verified by weighing into it 99-533 grams of recently boiled distilled water at 20°C. The exact weight of chemically pure sugar, which, when made up to a bulk of Iooc.c. in one of the corrected flasks at 28°C., gives a polarization reading of Ioo°, is ascertained by experiment for each instrument, and this weight of sugar is invariably used instead of the maker’s weight for 17°5° C.”’ It is at once evident that cane sugar can be determined by direct polari- zation only in the absence of other bodies which also rotate the plane of polarization. In very many routine analyses in the sugar-house the dis- turbing effect of other optically active bodies is small, and the polarization very closely measures the quantity of cane sugar present. For the purposes of trade and for the imposition of customs duties the polarization of raw sugars is accepted as the percentage of sucrose, from which, however, the polarization is to be carefully distinguished. In the presence of other optically active bodies the sucrose may be determined by the Clerget or double polarization methods, described in detail elsewhere. * The 26-gram weight has also come to be referred to as the International normal weight. 504 CHAPTER XXV The polarization, and also determination, of sucrose is affected by. the conditions discussed below :— Concentration.—The rotation of cane sugar varies slightly with con- centration; Nasini and Villavecchia!® found for # 3 to 65. [aj> = 66-438 + 0-010312 fp — 0:00035449 p?, where # is the percentage of sugar. In very dilute solutions the results of different investigators are very discordant. Tollens?? found very irregular values. Prbram** found a decrease from # 3:659 to 0-222 and Nasini and Villavecchia!® found an increase from p 1-253 to 0-824. Schmidt’s*4 tables, which still remain in use, are based on the formula :— fa]7= 66-514 —0-008415c¢, where c is the grams of sugar per Ioo c.c., and should be abandoned. The most probable formula is that of Landholt*® which combines the results of Tollens, Nasini and Villavecchia into the formula : [a]? = 66-438 + 0:00870 c. — 0:000235 c.2, for c, 0 to 65. Temperature.—The effect of temperature on polarimetric observation is twofold :—firstly, there is the effect of temperature on the quartz wedge compensating system, and secondly the effect on the specific rotation of the sucrose. As regards the first, three factors enter :—the linear expansion of quartz parallel to and perpendicular to the optic axis, the imcrease in the specific rotation of quartz with rise of temperature and the expansion of the scale, which becomes zero when the latter is engraved on the wedges. These effects have been studied by Schénrock*® and, as the result of his studies, it is found :— Rotation of quartz near 20° C. [@\> = [a], + [2]; 0-000143 (f — 20). Linear coefficient of expansion of quartz parallel to the optic axis, 0-000007 Whence specific rotation coefficient, 0-000143 — 0000007 =0- 00000136 Linear coefficient of expansion of quartz perpendicular to the optic axis, 0000013. Linear coefficient of expansion of nickelin scale, 0-o00018. Linear < - z. ,, glass », 0000008. Whence the total temperature coefficients for the instrument alone become :— Nickelin scale 0-000136-++0:000007 —0 :000013 +0: 000018 =0- 000148 Glass scale 0:000136-+0 - 000007 —0: 000013 +0- 000008 =0- 000138 Scale on wedge 0:000136-++0- 000007 —0 - 000013 =0+000130 and the following formule result :— Nickelin scale Sy3,=S,+S, 0-o00148 (¢—20) Glass scale Sg ,=S,+S, 0:000138 (¢—20) Scale engraved on wedge Sy5=S,+S, 0:000130 (/—z20), where S, is the reading at ¢° C.and Sy is that at 20° C. The effect of temperature on the specific rotation of cane sugar was first observed by Dubrunfaut®® and, though disputed by various physicists, a decrease with rise of temperature is now established. Schrénrock*®® has found that the coefficient varies with temperature and is as follows :— 10° .C.; 0°000242; 20° C., 0-000184; 30° C., 0-00012T. THE DETERMINATION OF CANE SUGAR 505 These sources of error are usually summed up in one formula which may be used as a general one independent of the type of instrument or scale :— Sop = S. +S, 0:0003 (t—20). This expression is based on the average results of Andrews?’, the U.S. Coast and Geodetic Survey*$, Wiley®®, Geerligs?®, and Watts and Tempany". The correction quoted immediately above is a blanket correction, and includes the error introduced by expansion of the tube, assumed to be glass and of correct length at 20° C. The above section assumes that the solutions are observed at the temper- ature at which they were made up. If observed at one and made up at a second temperature the expansion of the sugar solution influences the re- sult, and a correction based on the expansion of the sugar solution, applicable to solutions made up at 20° C. and observed at ¢° C., must be applied. The blanket correction found by Andrews and others agrees exactly with the sum of the individual corrections found by Schénrock, referred to 25° C. and a nickelin scale. At this temperature the coefficient for sugar is 0-000152, which added to 0-o00148 gives exactly 0-0003 as the blanket correction. Since, however, the temperature coefficient of sucrose is a func- tion of the temperature, a blanket correction can only be correct at one par- ticular temperature. The validity of temperature corrections as applied to impure sugars has been ably discussed by Browne.‘ The correction given above is only strictly valid for pure sucrose. Commercial sugars contain fructose, and for this body a reverse correction is necessary. Browne has shown that the correction given in this section is applicable generally to raw sugars of 96 test. For sugars containing much reducing sugar it actually accentuates the error, and for sugars of about 80 test he has shown that generally the polarization is independent of temperature, while below this test the correction is negative. Nevertheless, by a decision of the U.S. Supreme Court a temperature correction is applied to all products at the U‘S. Customs. This difficulty may be entirely eliminated by making all obser- vations at 20° C. as is done in the New York Sugar Trade Laboratory. The chemist in the tropics has to work at a temperature remote from 20° C. Since all his readings are equally affected, his control and balance sheet are not invalidated. The polarizations of the sugars at northern ports should however be systematically higher than those determined on the plantation, and exact coincidence should be considered as evidence of a deterioration of the sugar in storage and transit. Presence of Inactive Bodies—The most detailed study is due to Farn- steiner** who found a small decrease in the specific rotation of cane sugar in the presence of :— Hydrates of the alkalies and alkaline earths. Chlorides, nitrates, sulphates, carbonates, phosphates, acetates and citrates of the alkalies. Chlorides of the alkaline earths. Borax, magnesium sulphate. An increase occurs with formaldehyde. The effect is in all cases small, and in the quantities in which these bodies occur in routine analysis may be neglected. The action of lead acetate is discussed separately. 506 CHAPTER XXV The Errors Inherent to the Use of Lead Salts as Clarificants.—The use of lead salts in sugar analysis introduces two small, but distinct, sources of error. These are recognized by analysts, but in general, in technical work, are neglected. These inherent errors are discussed below :— In the majority of the schemes for clarification detailed beiow, an insoluble precipitate is formed, which occupies an appreciable volume, so that if, after clarification, the solution be made up to 100 c.c. the actual volume is too c.c. less the volume occupied by the precipitate ; prima facie, an error is thus introduced, though that this is the case is denied by certain chemists. H. Pellet** in particular claims that the precipitate formed by the addition of basic acetate of lead entrains sugar, and that this entrainment compensates for the volume occupied by the lead precipitate. In his experiments he shows that a weight of sugar material dissolved in water and made up to Ioo c.c. in the presence of its precipitate gives a reading of, say, 50; the same weight of sugar material made up to 200 c.c. in the presence of its precipitate will give a reading exactly half the first, in this case, 25 ; if the lead precipitate exercised an influence proportional to its volume, the first solution would be more than twice as concentrated as the second, and hence the first reading should be more than twice as large as the second. This phenomenon he attributes to the entrainment of sugar by the lead precipitate, and claims that it is unnecessary to apply a correction for its volume. The. writer in investigating the same subject found also that a fixed weight of sugar material made up of different volumes in the presence of the precipitate tends to give identical polarizations independent of the dilu- tion, and explains the apparent non-influence of the lead precipitate by an increase in the specific rotation of cane products with dilution. Horne’s very detailed experiments also point to the conclusion that the lead precipitate introduces a positive error and that sugar is not entrained. Correction for the volume of the lead precipitate is made by the following methods :— 1. Schetbler’s Method.**°—The material under analysis is first made up to a volume of Ioo c.c. in the presence of its precipitate, and the reading taken ; a second reading is taken under identical conditions, except that the volume is now made up to 200 c.c. Let x be the volume of the precipitate ; let a be the reading in 100 apparent c.c., and b the reading in 200 apparent c.c. Then (100 — x) a = (200 — x) b. Solving this equation x is found. 2. Deerr’s Method.4*—The material under analysis is first made up to 100 c.c. in the presence of its precipitate, filtered, and 50 c.c. of the filtrate diluted to 100 c.c., and the reading observed ; let it be a. The same weight of material is made up to 200 c.c. in the presence of its precipitate, and the reading taken; let it be b; let the volume of the precipitate be x; then 2a (100 — x) = (200 — x) b. Solving this equation x is found. The object of this procedure is to obtain both readings in the same concentration and at the same part of the scale, thus eliminating errors due to any change in opticity with dilution, errors in the zero point and errors in scale graduation. 3. Method of Sachs.47—The precipitate obtained is collected on a filter and washed until free from sugar ; it is then transferred to a graduated flask, THE DETERMINATION OF CANE SUGAR 507 into which is weighed a sugar of known polarization. This weight of sugar is then made up to an apparent definite volume in the presence of the pre- cipitate and a polarimetric reading taken. The apparent increase in the polarization of the sugar affords data to calculate the volume of the pre- cipitate. 4. Wiechmann’s Method.t8—The precipitate is collected, washed free of sugar, dried and weighed. Its specific gravity is then obtained with the pycnometer, benzene being the liquid used ; from its weight and density the - volume of the precipitate is calculated. 5. Horne’s Method.49—Horne eliminates the error due to the volume of the lead precipitate by making the solution of sugar product up to definite volume, and clarifying by the addition of dry basic acetate of lead in powdered form, and assuming that the volume of the acetyl radical which goes into solution is compensated by the volume of the material precipitated. This method has met with considerable approval, and may be considered as a standard process. All the above methods are applicable to the analysis of juices measured by volume and not by weight. Action of Basic Lead Acetate on Sucrose-—The effect of lead acetate on cane sugar is small, and is given by Bates and Blake®® as under, pure sugar being tested in normal concentration :— Basic lead Difference in Basic lead Ditference in acetate added. Polarization, acetate added. Polarization, aoe Ventzke. GC. Ventzke. O°5 5c — 0:09 4:0 — 0-06 I-o — 0°l3 ae 5-0 — 0:93 I°5 — o-Io oie 6-0 — 0-00 2‘O — 0°53 7-0 0 +05 2°5 a — 0:06 8 -o 0-09 3°0 — 0:08 =< IO -00 O'I9 Action of Basic Lead on Reducing Sugars.—The left-handed rotation of fractose is diminished by the presence of lead acetate in alkaline solution, so much so that in great excess the opticity may become positive. This observation was first made by Gill.6! It has also been shown by Davis*? that the position of equilibrium is not obtained instantaneously, and that a slow, progressive change in the polarization of products containing fructose takes place in the presence of basic lead acetate. Neither glucose nor fructose is precipitated by basic lead salts in pure solution, but, in the presence of bodies which form insoluble combinations with lead, both glucose and fructose are carried down, probably in the form of lead glucosate and fructosate. This observation was first made by Lagrange,®* and has been further studied and proved by Geerligs,*4 Pellet,5> Bryan®® and Deerr,®” since the absence of precipitate in the system, fructose-water-basic lead acetate, has led to much confusion and misunderstanding. It is also to be remembered that this lead compound is not broken up by the addition of sodium sulphate or other precipitant of lead. Actually the precipitation of an excess of lead in this way leads to a further precipita- tion of reducing sugars and accentuates the error. The error is also intro- duced by the use of neutral lead acetate followed by sodium carbonate to remove an excess of lead. 508 CHAPTER XXV It follows then that the polarization of a product containing reducing sugars depends on the quantity of basic lead acetate used in the clarification, and it is for this reason that formal instructions often specify: “ Carefully avoiding an excess.”” Nevertheless, both the personal equation of individual operators and also the composition of the lead solution will affect the deter- mination ; one analyst will use just sufficient lead to obtain sufficient de- colorization to enable a reading to be obtained, and a second will aim at ob- taining the maximum decolorization. Lower readings will be obtained by the former, and results between different analysts are not strictly comparable. Elimination of this source of error is given under “‘ Determination of Sucrose.”’ Preparation of Sugar Materials for Polarimetric Observation.—Except in special cases, all sugary materials require clarification and filtration before observation in the polariscope. The agents used are :— Alumina Cream.—Used in sufficient quantity, alumina cream will entangle the colloids even in a material such as waste molasses. Its use is limited to the removal of turbidity from high grade materials. It is prepared by precipitating a cold saturated solution of an alum with ammonia and washing the aluminium hydroxide by decantation till it is free from sulphates. Alternatively, the washing may be dispensed with and soluble sulphates left in solution. This preparation is used in conibination with lead clarification, the sulphates precipitating any excess of lead and producing perhaps a more brilliant filtrate. Kieselguhr.—The diatomaceous earth mined and used as kieselguhr has the property of entangling colloids and affording a clear filtrate when used in sufficient quantity with sugar products. It is used chiefly as an adjuvant with other materials. Precipitation of Alumina within the Solution—This method is due to the writer, and, as finally formulated, is as below :— A saturated solution of baryta* is prepared. At 27-5 C. such a solution is nearly 0-5 normal. 165 grams of aluminium sulphate (A/,(SO,),18H,0), and 135 c.c. of normal sulphuric acid are dissolved in 1,000 c.c. This solution is adjusted until 15 c.c. are exactly equivalent to 25 c.c. of the baryta solution, using phenolphthalein as indicator. The sulphuric acid is employed so as to accelerate inversion when sucrose is determined, as opposed to polarization. As a clarificant it has no objective, but its presence avoids the use of two ~ sulphate solutions. The sugar material to be prepared for examination is dissolved in 50 c.c. of water; 25 c.c. of the baryta solution added and mixed with the sugar solution ; 15 c.c. of the alum solution is then allowed to flow into the mixture with constant stirring. The whole is then completed to roo c.c. and is then ready for filtration and examinaticn. The volume occupied by the precipi- tate produced is approximately 0-70 c.c. These quantities are sufficient to clarify 3-25 grams, or one-eighth normal weight of a waste molasses and to give a filtrate readily capable of observation in a 40 cm. tube, provided a nitrogen-filled tungsten filament lamp is used. Juices and normal weights of sugars can be clarified with less of the re-agents, but it is convenient to use one fixed quantity and apply one fixed correction for the precipitate volume. *The use of aluminium sulphate and baryta as a defecant in manufacture was suggested by Pimienta in “‘Manuel de Cultivo de Cafia de Azucar.” 1881. THE DETERMINATION OF CANE SUGAR 509 A fuller decolorization in this process is obtained by the use of sodium hydrosulphite, added just before filtration. The advantage of the process is that nothing is introduced into solution, the products of the reaction, barium sulphate and aluminium hydroxide, being insoluble. It is not so convenient for use as basic lead acetate, which will continue as the standard defecant, but it may be used for special analyses. Basic Lead Acetate.—This re-agent, the use of which is due to Clerget,*® is prepared under a variety of directions :—(a@) 130 grams litharge and 430 grams neutral acetate of lead are boiled with I,o00 c.c. water, and finally diluted to a density of 1-250. (0) 200 grams litharge, 600 grams neutral acetate of lead and 2,000 c.c. water, allowed to stand for 12 hours with occa- sional agitation. Neutral Lead Acetate——Neutral lead acetate may be used with materials of light colour, but is nearly useless with substances such as molasses. It may be kept as a solution of 54° Brix. Dry Basic Acetate of Lead.—The use of this material is due to Horne.*® It is used as the anhydrous dry salt and placed directly in the solution. Calcium Hypochlorite.—The use of this material is due to Heron®® and to Zamaron.*® A solution of calcium hypochlorite made by agitating 625 grams with 1,000 c.c. of water is filtered and preserved for use in stoppered bottles. It should be of density I-14 to 1-16. Pellet uses 20 c.c. of this solution in combination with neutral lead acetate to decolorize 4 grams of molasses. Basic Lead Nitrate——This process is due to Herles.*! Two solutions are used :—(a) 90 grams caustic soda dissolved in 2,000 c.c. of water; (0) I,000 grams lead nitrate dissolved in 2,000 c.c. water. The lead solution is added to the alkali solution immediately before use, in the proportion of 1 of lead to I-o or I-I of alkali. Mercuric Compounds.—Mercuric compounds exercise an effect similar to lead salts, but not in so marked a degree. They, however, precipitate amides from solution and are used for the separation of these bodies. The following formula is due to Andersen®? :—220 grams mercuric oxide are dissolved in 100 c.c. of nitric acid of specific gravity I-39. This is made up to I,000 c.c. with the addition of 60 c.c. of a 5 per cent. solution of caustic soda. After addition to a sugar solution neutralization is necessary. It is stated that an excess has no effect on the opticity of sugars. Animal Charcoal.—By the use of this body, all cane sugar products can be obtained as a brilliant and largely decolorized filtrate. Since sugar is absorbed, as was first shown by Clerget,®$ this material has only a limited and specialized use in analysis. Certain highly purified charcoals have been prepared in which the absorption is a minimum, but results obtained are not reliable, and the products offered by different dealers vary very considerably. To nullify the absorption, it has been proposed to saturate the charcoal with sugar before use, but with dilute solutions sugar might then be dissolved out from the charcoal. In a second procedure, the sugar solution is filtered through a column of the charcoal and the runnings rejected until absorption no longer takes place. A third process aims at obtaining a correction by observing the absorption from solutions of known polarization, and conducting the test under condi- tions exactly equal to those of the check. 510 CHAPTER XXV Formal Instructions for obtaining the Polarization.—/Jwices.—(a) Fill a flask graduated at I00-II0 c.c. to the I00 c.c. mark with juice. Add suffi- cient basic lead acetate to clarify and no more than necessary. Complete the volume to Ilo c.c. Shake. Filter. Reject the first runnings. Obtain Nx" Ce too X D N is the reading, D is the density of the juice referred to water at 17°5° C., and W is the normal weight adopted. (b) Transfer 52-096 grams of juice to a 100 c.c. flask referred to Mohr’s c.c. (or 52 grams if the flask is graduated in true c.c.). Add lead acetate as in (a), complete the volume with water to Ioo c.c._ Filter, etc., as in (a). The polarization is one-half the observed reading. Spencer’s pipette,®* graduated © with reference to degrees Brix, so as to deliver the proper quantity corres- ponding to the density of the material, is used in this routine. (c) Place an unmeasured quantity of juice in a container. Add sufficient dry lead acetate to clarify. Agitate violently. Filter, etc., asin (a). Then the polarimeter reading. Then the polarization is where the polarization is where N is the reading, D is the density of the juice NW 100 D referred to water at 17-5° C., and W is the normal weight adopted. This method is due to Horne.?? Raw Sugar._—_Weigh out the normal weight. Transfer to a I00 c.c. flask. Dissolve in water, making the total volume about 80 c.c. Add suffi- cient basic lead acetate to clarify, but not an excess. Complete the volume to 100 c.c. Shake. Filter. Reject the first runnings. Obtain the polari- meter reading of the filtrate, giving the polarization of the sugar. The formal directions given above are substantially those adopted by the U.S. Bureau of Standards,** and for commercial and revenue purposes should be strictly followed. It is not permissible, for example, to take 24+32 grams and calculate the polarization. Such a variation is permissible, however, to the analyst working as an individual, but legally the exact instructions should be followed. In addition to the above formal instructions, the use of filtered light is obligatory. For legal purposes, the observation must be made at 20° C., or corrected for temperature error, as indicated in the previous chapter. The 'J.S. Bureau of Standards does not take into account the effect of the volume of the precipitate, or the effect of basic lead salts on the rotation of the fructose, which may be present. In a strict determination of sucrose in a sugar, as opposed to a polarization, these points should be considered. The routine control operations also neglect these points and also any temperature correction. Massecuites, Molasses, etc.—The routine is essentially as for Raw Sugar. In actual work the following procedure is adopted by most analysts. In obtaining the Brix the material is diluted 1: 1. Normal weight of this diluted material is transferred to a 100 c.c. flask by means of a Spencer pipette and clarified as for a juice. Twice the reading gives the polarization. With very dark molasses it is better to use a half-normal weight of the 1: 1 dilution. Alternatively, the material may be weighed out, an integral fraction of the normal weight being used, or not, at the option of the operator. Thirdly, a solution of any ascertained degree Brix may be made up without weighing. This solution may be treated as a juice and the purity THE DETERMINATION OF CANE SUGAR 511 determined, whence the polarization is calculated from the Brix determina- tion. The results obtained by these different routines will vary following the principles discussed at the beginning of this chapter. For strict control work, the determinations should be made in the appropriate concentrations of non-sugar. Filter Press Cake-—As under Raw Sugar, but using only 25 grams to compensate for the volume occupied by the insoluble matter. Determination of Sugar in Bagasse.—The process always used is one of aqueous digestion and extraction of the sugar in a determined volume of water. A number of routines have been suggested and some of these are described below.* Java Experiment Station Method.—Twenty grams of finely divided material are heated with 250 c.c. water and allowed to boil for fifteen minutes, the FIG. 335 Fic. 336 water evaporated being continually replaced by a drip from some convenient vessel. After heating, cooling, and the addition of basic lead acetate, the quantity of water remaining is determined by weight, to which is added that introduced with the material. The polarization of the filtered extract gives the polarization of the bagasse by calculation, or from a table. Norris's Method.**—This method employs the “ double cooker,” shown in Fig. 335, which is of dimensions :— A. 6ins. high by 54 ins. diameter. B. 4% ins. high by 4} ins. diameter. One hundred grams finely divided material are placed in vessel B, with 500 c.c. hot water and 5 c.c. of 5 per cent. solution of sodium carbonate. Water is placed in the vessel A and boiled for one hour. Every fifteen minutes the material in B is pressed down by the tamp C. After cooling, the weight of the extract is determined, the extract is pressed out, filtered * The exactness of the usual bagasse analysis schemes has been subject to controversy. Pellet®> found that ordinary boiling failed to extract all the sugar. Geerligs** found that prolonged boiling gave higher results, which he attributed to the gradual solution of hemi-celluloses. Norris** did not confirm this, but found that the fineness of division very materially affects the rate of extraction. 512 CHAPTER XXV through cheese-cloth, 99 c.c. placed in a Ioo c.c. flask, adjusted to the mark with lead acetate, filtered and polarized, and the polarization of the bagasse obtained by calculation, or from a table. Zamaron’s Method.*7—100 grams of finely divided bagasse are put along with 200 c.c. of water in a wire basket placed in a copper container provided - with a draw-off cock. The bagasse and water are boiled for Io minutes — and the extract drawn off into a litre flask. This process is repeated seven times, when rather less than 1,000 c.c. will have been obtained. Extraction | is now assumed complete. Lead acetate is added, the volume completed to 1,000 c.c. and the polariscope reading obtained. Deerr’s Method.68—This method employs a larger quantity of material, so as to eliminate the necessity for chopping and sub-sampling with its accompanying errors and consumption of time. The apparatus, Fig. 336, consists of a vessel A of height twelve inches and of diameter six inches. A draw-off cock, B, is fitted at the bottom and a second, C, at a height of 81 inches. The vessel is filled with boiling water above the height of the cock C, and the surplus removed by opening this cock. A fixed quantity of water is thus obtained. The bagasse is contained in the basket D, of dimensions 52 inches by 10? inches. This size of basket will hold 500 grams of loosely packed bagasse. This quantity is weighed out into the basket and the latter is then placed in the container. This container is provided with a wide machined, or ground, flange, on which sits the flat cover E, carrying the metal reflux condenser F.. Clamps or spring clips, G, make a tight joint. The whole apparatus is then placed on a six-inch electric hot plate or over a naked flame, and the contents allowed to boil for 45 minutes, at the end of which time extraction is complete. A portion of the extract is drawn off, cooled, defecated with dry lead acetate and polarized. The quantity of water contained in the vessel, plus that introduced with the bagasse, can be correlated with the weight of bagasse constantly used, so that a half-normal extract is obtained.* The reading in the 40 cm. tube then gives the polarization of the bagasse. In this scheme only one weighing is required, namely, that of the basket and its contents against one fixed weight, and no calculation or reference to tables is required. Bagasse from the last mill of a train is sufficiently comminuted to allow of complete extraction. This routine is accurate and requires less time and attention than any other yet proposed. Determination of Sugar in Cane.—As explained in the chapter on “ Con- trol,” this quantity is almost always obtained from combining certain of the routine control observations. When a direct observation is required on individual stalks, the following methods may be adopted :— I. Crush the stalks, halved or quartered longitudinally, in a hand mill. Weigh the resulting bagasse and take the weight of juice as the difference between weight of cane and bagasse. Determine the sugar in juice and in bagasse and calculate back to cane. Very rough results may be obtained from the analysis of the juice alone, as indicated in Chapter XXVII. 2. Thoroughly comminute the cane and extract the sugar by aqueous = digestion, following one or other method indicated under “ Determination * This is best done by fixing the weight of bagasse after ascertaining how much water is contained in the apparatus. There is, of course, no reason why exactly 520.96 grams bagasse should be used, as long as a half normal solution is obtained. There will be a different weight of bagasse for each apparatus, dependent on how much water is held in the container. , THE DETERMINATION OF CANE SUGAR 513 of Sugar in Bagasse.”” The means usually found to comminute the cane are :— . (a) The “‘ Chipped beef” slicer, Fig. 337, obtainable from dealers and giving, with considerable labour, very thin transverse slices. A pattern- maker’s trimmer may also be used with advantage. (b) The “‘ Sausage meat chopper,” Fig. 338, consisting of a heavy, ver- tically reciprocating knife with chopping table simultaneously rotating _ about a vertical axis in a horizontal plane. This machine produces finely divided material at the expense of excessive manual labour and much noise. (c) The “‘ Hyatt cane reducer,’ Fig. 339. This consists of a horizontal, rapidly rotating drum, on the periphery of which are arranged a series of staggered teeth, or “ drunken saws.’ This machine rapidly reduces cane, in quantity, without loss of juice, to a finely shredded condition, from which the juice is readily extracted. It is by far the most valuable appliance for this specific purpose. Determination of Crystallized and Dissolved Sugar.—The total sugar in a massecuite or molasses exists in two forms: either separated out as crystals, or still remaining in solution in the necessarily accompanying water. In general, two similar juices, similarly treated and boiled to the same water content, will separate out the same amount of crystals, but the actual recovery at the centrifugals may be widely different. For, in one case, by skilful pan-boiling, the crystallized sugar is obtained in a form permitting of easy separation from the molasses, and, in a second, the presence of fine crystals may cause considerable losses. The determination of the crystallized sugar affords a valuable check on the pan-boiler. Vivien’s Method.®®°—Weigh out about 200 grms. of massécuite and place in the funnel of the pressure filtering apparatus, as in Fig. 340, connect the apparatus to a filter pump, and wash with a cold saturated solution of pure sugar and water until all molasses are removed; transfer the crystals to a tared dish and obtain their weight. Remove about Io grms. and dry to constant weight to determine the water adhering to the crystals. At a 2M 514 CHAPTER XXV temperature of 84° F., for each one part of water 2-125 parts of sugar are dissolved in a saturated solution. This last determination gives data to calculate the weight of washing syrup which has replaced the molasses. An example is appended. Weight of massecuite, 200 grms. ; weight of washed crystals, 175 grms. ; percentage of water in washed crystals, 7-54. Then total moisture in washed 175 X 6:54 100 12°62 X 3°125¢t— 35:77 grms., and weight of crystals 175 — 35°77 = 139°23 grms., or 69-66 per cent. on weight of massecuite. Dupont’s Method.?°—Heat the massecuite to a temperature of 80° C. and centrifuge in a small hand machine, the wire basket of which is covered with thin flannel, or some similar material; polarize the molasses and the cured sugar and calculate the percentage of crystallized sugar from the fol- crystals, = 12-62, and wash liquor in washed crystals = Fic. 339 , lowing formula: % pea nue 2 where x = weight of crystallized sugar in one part of massecuite, a the percentage of sugar in the massecuite, p the percentage of sugar in the cured crystals, and #’ that in the molasses. This formula is applicable for use on the factory scale, provided no water is used in curing, and that the molasses are filtered through flannel before analysis, so as to remove fine crystals ; if water be used in small quantities, and if the amount can be calculated, the sugar percentage of the molasses can be corrected for dilution, but, in this case, the formula will not give results so correct. Geerligs’ Method.*1—This method depends on the observation that sugar crystals themselves only contain a trace of ash, the ash of commercial sugars being due to the accompanying molasses ; hence, in a massecuite, the ash is due solely to the molasses. Determine the percentage of ash in the masse- cuite and in its molasses freed from fine grain by filtration through glass wool; as an example, let the massecuite contain 2:25 per cent. and the molasses 6-07 per cent. ash; then the percentage of molasses in the massecuite is 2-2 ce < 100 = 37:07 per cent. ; the remainder 63-93 per cent. being crystal- lized sugar. THE DETERMINATION OF CANE SUGAR 515 Deerr’s Method.—On the plate of a Buchner funnel is placed a layer of glass wool, after which the funnel is filled with the massecuite under analysis. On connecting to the vacuum, the molasses, entirely freed from crystals, passes through. Let x and y be the proportions of sugar in the massecuite and filtered. molasses, respectively, and let s be the proportion of sugar as crystals per unit of massecuite. ioe I—-y This equation gives the amount of crystals of pure sugar; actually, in practice, the crystals are obtained with an adhering layer of molasses, which increases the weight, as indicated by this analysis. These methods have been described as applicable to massecuites ;_ they are, of course, applicable to molasses to determine the quantity of fine grain which has been separated on cooling, or is present after having passed through the mesh of the centrifugal basket. Then x = (I —s) y +s, whences = Detection and Estimation of Small Quantities of Sugar.—The reaction of Molisch’? is the one most often used. It is thus carried out :—Five c.c. of concentrated sulphuric acid are placed in a test tube, into which is then run 2 c.c. of the water supposed to contain sugar, followed by the addition of two or three drops of a 5 per cent. alcoholic solution of a-naphthol; the contents of the test tube are shaken, and the colour produced compared with that obtained with known quantities of sugar ; as little as one part of sugar in 1,000,000 can be detected. If the sul- phuric acid alone produces the reaction it should be boiled to destroy organic matter before use. Ammonium molybdate is also a useful re-agent to employ, and, as shown by Pinoff,’* is specific for fructose in the absence of mineral acids. As applied by Pinoff to fructose 0-1 gram of material, Io c.c. of a 4 per cent. solution ammonium molybdate, Io c.c. water and 0:2 c.c. glacial acetic acid are heated at 95° C.; fructose in three minutes gives a fine blue coloration ; all sugars give the same reaction in the presence of mineral acids. The writer modifies this test as follows :—To a suspected water 2 per cent. of hydrochloric acid of 1-18 sp. gr. is added, placed in a test tube, and heated on the water bath for five minutes; an equal quantity of a 5 per cent. solution of ammonium molybdate is then added, and the heating continued for five minutes ; in the presence of sugars a blue coloration is produced, which may be compared with previously prepared samples. The colour thus produced may be simulated by solutions of copper sulphate prepared to represent the coloration produced by 1 part of sugar in 20,000, etc. The sugar in waste waters and condenser water may be also conveniently estimated by evaporating a large quantity, say, two litres, to a volume of Too c.c. and determining the sugar by the polariscope or by ascertaining the reducing sugars after inversion. In making the calculations, the quantity of water used in the condenser is estimated from the difference in temperatures of the incoming and outgoing water combined with a knowledge of the quantity and pressure of the steam given offin the last body. The experiments of the writer (cf. Chapter X VIII) have shown that the steam given off in the last body is nearly r/nth of the total evaporation, where 7 is the number of units. 516 CHAPTER XXV The Determination of Sucrose as opposed to Polarization.—It only occasionally happens that sucrose is the sole optically-active body present in a material presented for analysis. Should other active bodies be present they will be returned as sucrose with an influence either positive or negative. The influence of such adventitious bodies may be eliminated by the following procedure developed by Clerget’! at the instigation of Biot. Let x be the rotation due to sucrose and let y be that due to other active bodies. Then, if d be the direct polarization, d =x-+y. Let an operation be made on x changing the value of x to a x, the value of y remaining unchanged. If 17 be the reading now observed in the polarimeter, 7=ax-+y. Subtracting this second equation from the first, d—1=x+y —ax —y =x (I-a), d—t : ' whence x = = so that if a be known, x, or the rotation due to the sucrose alone, can be calculated. The quantity I—a, or generally (I—a) x I00 is known as the Clerget constant. The operation by means of which this determination is made is the inversion or hydrolysis of sucrose under the influence of a catalyst into equal parts of glucose and fructose. The catalyst usually employed in analysis is hydrochloric acid, and in the immedi- ately succeeding pages reference is made solely to this means. Sucrose after inversion into glucose and fructose (invert sugar) possesses a left- handed rotation, so that the value of a in the equation above is negative and 1—a is greater than unity. The reading after the operation, or the inverted reading, 7, will also be negative unless the value of y is suffici- ently great to counterbalance the negative rotation of the invert sugar formed. In order that this analysis may be justified, the following postulates are ~ necessary. 1.—The operation of inversion must be conducted in such a way that the same value can always be found for a. 2.—The influence of temperature and concentration must be accurately known. 3.—The value of y must remain unchanged. Of these influences that due to temperature has always been recognised and allowed for ; it is only recently that the other factors have been taken into consideration and the great majority of textbooks ignore them. Temperature. The rotation of invert sugar decreases with rise of tem- perature and is such that d—t t I —a—— 200 where ais the observed value at 0° Cand ¢ is the temperature of observation. This correction for temperature was given by Clerget and has been uniformly confirmed by all subsequent observers. For example, Clerget found that under his routine a sugar solution polarizing 100°, after inversion polarized — 44° at 0° C., — 39° at 10° C., — 34° at 20° C., etc. The Clerget constant, then, becomes I — (—0-44) = I-44, or, as generally expressed, 144, in which = constant F bet oie t case 0:5 ¢ is used as the temperature correction in place of Saar “ THE DETERMINATION OF CANE SUGAR 517 Method of performing the Inversion—The methods of performing the inversion accepted as standard are many. They have been critically ex- amined by Jackson and Gillis, and the following section is based largely on their work. The original Clerget method of inversion was to place 50 c.c. of the material to be examined in a 50-55 c.c. flask, fill to the 55 c.c. mark with strong hydrochloric acid, heat to 68° C., taking 15 minutes to reach this temperature, allow to cool and polarize, adding ro per cent. to the result or using a tube 10 per cent. longer than that used in the direct polarization. This method has always been used in France and is the one preferred by. Browne. In 1883 the original procedure of Clerget was modified thus by Herzfeld7®. Into a 100 c.c. flask, 50 c.c. of the material from the direct polarization is placed together with 20 c.c. water and 5 c.c. of 38 per cent. hydrochloric acid, sp. gr. 1-188. The flask and its contents are then heated to 67°C., taking 2-5 to 3 minutes to reach this temperature, which is after- wards kept as near as possible at 69° C. for 5 minutes and always between the limits 67—70° C. After cooling rapidly and completing to 100 c.c., the reading is observed. These directions are frequently misquoted, acid of 38-8 per cent. strength sp. gr. I: 1198 being specified, and the total time of heating being extended to Io minutes. Jackson and Gillis?® have shown that this routine is unsound since dupli- cates cannot be obtained, and since after a maximum value of a has been obtained its value falls so rapidly with continued heating that unavoidable deviations from one determination to another invalidate results. They show a maximum, constant with large deviation from the stipulated time, can be obtained by their method (a), or that of Walker (b) :— (a) Seventy-five c.c. of material and five c.c. of 38°8 per cent. acid are placed in a water bath kept at 60° C., agitated for three minutes and allowed to remain in all for six minutes. If Io c.c. of acid diluted 1:1 and 70 c.c. material are used, the total time of exposure is increased to 9°5 minutes. (6) Seventy-five c.c. of material are placed in a flask and heated to 65° C., followed by the addition of 5 c.c. of 38-8 per cent. acid. The inversion is complete after 15 minutes’ standing without further heating. Methods employing inversion in the cold are in use and Tolman’’ pro- bably first proposed them, using 5 c.c. of strong acid to 50 c.c. of material and allowing ro hours at 26° C. and 20 hours at 20°C. for inversion. Steuerwald’8 used 30 c.c. of acid I-1029 sp. gr. (38-8 per cent. acid diluted 1:1) and prescribed 2 hours’ exposure if the temperature was 25° C. or over, and 3 hours if below 25° and above 20°C. Jackson and Gillis, for a total volume of 80 c.c. with 5 c.c. of 38-8 per cent acid, demand 30-8 hours at 20° C., 14:6 hours at 25° C., 7-1 hours at 30° C., 106 minutes at 40° C., and 29 minutes at 50° C. With 55 c.c. total volume and 5 c.c. 38-8 per cent. acid, the times are 21-2 hours at 20° C. and Io hours at 25° C. Concentration of the Acid.—The rotation of invert sugar varies with the concentration of the acid, and accordingly there will be found different con- stants depending on the concentration of the acid in material as presented for observation. The value found by Clerget, 16 grams sucrose and 5 c.c. strong acid, in a total volume of 55c.c., wasI-44. The value under Herzfeld’s pro- 518 CHAPTER XXV — cedure, 13 grms. sucrose and 5 c.c. of 38 per cent. acid in 100 c.c. was found by him as 1: 4266. Other determinations with this acid concentration or with 38-8 per cent. acid and the same sucrose concentration are 1-4278 (Walker), 1- 4288 (Tolman), 1-4305 (Steuerwald). With the greater proportion of acid (v. sup.) Steuerwald found 1-4554. These values are in some doubt since the use or otherwise of bichromate-filtered light is not stated. The very careful and -exact determinations of Jackson and Gillis’® give a value of 1-4325, referred to bichromiate-filtered light, 13 grams of sucrose per Iooc.c. and 5 c.c. of 38-8 per cent. acid; and this value should be accepted as the most probable. The influence of concentration is noteworthy and the values of the constant given above refer only to that one particular concentration. The rotation of invert sugar falls with dilution and hence also the value of the Clerget constant. a Concentration of the Sugar.—A different constant obtains with each different concentration of sugar. In the Herzfeld routine the value of the constant is given by the expression 141.84 — - where 7 is the direct reading in the 20 cm. tube after the inversion, which at a concentration of 13 grams sugar per 100 c.c. gives the value 142.66. In the scheme given below due to Jackson and Gillis, and representative of the latest work, the appropriate value of the constant for each concentration and temperature is given in tabular form. Constancy of the Value of y.—The presence of basic lead salts diminishes the rotation of the fructose originally present, which is afterwards restored in the process of inversion, thus giving a variable value of y (v. sup.). Pellet’? was the first to correct for this, and he acidified the material used for the direct reading withsulphurousacid. This process reads as follows:—Two hundred c.c. of normal weight solution of material are placed in a 220 c.c. flask, clarified with basic lead acetate, completed to 220 c.c. and filtered. One hundred c.c. of the filtrate are treated with. 30 c.c. sulphurous acid in saturated solution, made up to 200 c.c., filtered if necessary, and observed. A second portion of the original filtrate from the lead clarification is used to obtain the invert reading. The rotation due to the sucrose is then obtained after making the necessary allowance for dilution and selecting the ap- propriate constant. The method generally used in Java, due to Ter- vooren, °° makes a similar correction in principle, acidifying the filtrate from the lead clarification with acetic acid. These last two methods eliminate a very substantial source cf error, but still do not fulfil the postulate that there be no change in the value of y (v. sup.), since the media in which the direct and inverted readings are made are not the same. An attempt to eliminate this error is due to Andrlik, who proposed to take the direct reading in the presence of urea and hydro- chloric acid, the former body inhibiting inversion long enough to allow an ob- servation to be made; this method has not found general acceptance. That method which most nearly meets all the conditions necessary for accuracy is the double neutral polarization method first proposed by Saillard.§4 In his method a quantity of sodium chloride, equivalent to the hydrochloric acid used in inversion, is added to the material used for direct polarization, and, after inversion, the hydrochloric acid present is exactly neutralized with caustic soda. There thus result two systems similar except for the 4. THE DETERMINATION OF CANE SUGAR 519 essential change of sucrose to invert sugar which it is the object of the anal- ysis to obtain. The method of Saillard has been developed by Jackson and Gillis, who use ammonia as the neutralizing agent, and take the direct reading in the presence of the appropriate quantity of ammonium chloride. They call particular attention to the necessity of exactitude in the analysis, failing which, errors, other than those intended to be eliminated, may be introduced. A scheme, one of several proposed by them, but quite general, is quoted below, and it may be mentioned that this scheme takes into - account the effect upon the rotation of cane sugar of the ammonium chlo- ride used in the direct reading. Jackson and Gillis’ General Double Neutral Polarization Method.— ‘Reagents: Hydrochloric acid d@ “2 1-z02g (24-846 Brix) ; ammonium hydroxide solution, 5 to 6 N; solution of ammonium chloride containing 226 grams per litre; pulverized potassium or sodium oxalate. Ascertain by at least three concordant titrations in the presence of methyl orange the volume of the ammonia solution required to neutralize Io c.c. of the hydrochloric acid. Prepare the normal solution of the substance to be analysed or a solution of such fractional normality as the nature of the material and the sensibility of the saccharimeter will permit. Clarify with the minimum quantity of dry basic lead acetate. Shake thoroughly and filter. (If desired, the solution may at this point be freed from lead; but, if this is done, the de-leading reagent must be added to the whole filtrate. Finely pulverized potassium oxalate in minimum quantity is added until precipitation is complete. Filter. If this procedure is omitted, the lead is precipitated satisfactorily by the chlorides added later). Pipette into two I00 c.c. flasks two equal volumes of the filtrate (50 c.c. 70 C.C., OF 75 C.C.). For the direct polarization, add to one portion 15 c.c. of the ammonium chloride solution or 3-392 grams of dry ammonium chloride. Complete to volume at the temperature at which the observations are to be made; filter, if necessary, and polarize. For the invert polarization as follows: Pipette 50 c.c. into a I00 C.c. flask, add 20 c.c. of water and Io c.c. of hydrochloric acid, d m I+1029 ; immerse in water bath at 60° C. for g min., agitating continually and cool quickly. . After the solution has become quite cold, add from a burette while continually shaking the precisely determined volume of ammonia required to neutralize the acid. Adjust the temperature, make to volume, filter, if necessary, and polarize at carefully controlled temperature. Multiply both polarizations by the factor— Volume of original solution containing 26 grams of sample. Volume of solution taken for polarization. The algebraic difference between the corrected polarizations gives P—P’. If the original filtrate contained 26 grams in Ioo c.c., refer to the following table, and under the column which designates the volume taken for the invert polarization find the value of the divisor. Apply the temperature correction and divide into P—P’. If the original solution contained a fraction of 26 grams of the sample, multiply P—P’ by this fraction before referring to the following table. Divide into P—P’ 520 CHAPTER XXV Volume of solution taken for invert polarization. Temperature corrections (to be subtracted). P—P 10 4 1] 50c.c. x 2/70c.c. x= 75c.c. X 3 90.9le.c x 10 133206) Sacercece | cee eel aaa ce 134.06 || 20.0]0.00|| 23.0 1.59 26.0 3.18) 29.0) 4.77)\| 32.0| 6.36 N35 078) foeitysteen| amet are ASS PG! Pe eee sieror 20.1] 0.05 | 23.1 1.64 || 26.1 | 3.23 | 29 1| 4.82|| 32.1] 6.41 1333169)... siren 1332607) oo Sack oo Wien ese. cate 20.2} 0.11 || 23.2) 1.70 26.2) 3.29) 29.2)| 4.88 || 32.2) 6.4: NBS S413 4 al toccreretere tsa arecisrereyslo dl wore lavevorw cletas 20.3] 0.16]| 23.3} 1.75 26.3 3.34) 29.3)| 4.93 || 32.3| 6.52 133 133.34 133.68 133.77 134.04 || 20.4] 0.21) 23.4) 1.80 26.4 3.39) 29.4) 4.98 || 32.4] 6.57 130 133.32 133.66 133.74 134.01 || 20.5] 0.27] 23.5) 1.86|| 26.5 | 3.44 | 29.5) 5.04|| 32.5| 6.63 125 133.29 133.62 133.69 133.95 || 20.6| 0.32/| 23.6/| 1.91 26.6 3.50 |.29.6 5.09 || 32.6| 6.68 120 133.25 133.57 133.65 133.89 || 20.71 0.37|| 23.7) 1.96|| 26.7 | 3.55 || 29.7| 5.14]| 32.7] 6.73 115 133.22 133.52 133.60 133.84 || 20.8] 0.42 | 23.8] 2.01 26.8 | 3.60, 29.8)|5.19]| 32.8| 6.78 © 110 133.18 133.47 133.55 133.78 || 20.9|0.48 | 23.9 2.07 || 26.9 3.66 | 29.9 5.25 || 32.9| 6.84 105 133.15 133.43 133.50 133.72 || 21.0] 0.53|| 24.0} 2.12|| 27.0 | 3.71 || 30.0 5.30} 33.0| 6.89 100 133.12 133.38 133.45 133 66 || 21.1}0.58}| 24.1 | 2-17|| 27.1) 3.76 || 30.1 | 5.35 || 33.1] 6.94 95 133.09 133.34 133.40 133.60 || 21.2] 0.64 || 24.2 | 2.23 || 27.2 | 3.82 || 30.2) 5.41 || 33.2| 7.00 90 133.06 133.29 133.35 133.54 || 21.3]0.69 | 24.3) 2.28 27.3 | 3.87 | 30.3| 5.46|| 32.3] 7.05 85 133.02 133.25 133.30 133.48 || 21.4|0.74 24.4 2.33 27.4 | 3.92 || 30.4) 5.51 || 33.4) 7.10 80 132.99 133.20 133.25 133.42 || 21.5]0.80|! 24.5 | 2.39}/ 27.5 | 3.98 || 30.5| 5 57|/ 33.5) 7.16 75 132.95 133.16 133.21 133.36 || 21.6]0.85| 24.6) 2.44 27.6 | 4.03 | 30.6) 5.62} 33.6| 7.21 70 132.92 133.11 133.16 133.30 || 21.7]|0.90 | 24.7| 2.49 27.7 | 4.08 || 30.7} 5.67 || 33.7| 7.26 65 132.89 133.07 Weyer) (1) 133.24 ||21.8}0.95 | 24.8 | 2.54 27.8 |4 13 |) 30.8) 5.72 || 33.8} 7.31 60 132.86 133.02 133.06 133.18 || 21.9] 1.01 24.9 2.60 27.94.19 30.9! 5.78 || 33.9| 7.37 55 132.82 132.97 133.01 133.12 |) 22-0] 1.06]! 25.0 2.65 || 28.0 | 4.24 || 31.0| 5.83|| 34.0] 7.42 50 132.79 132.92 132.96 133.06 || 22.1}1.11 || 25.1|2-.70)| 28.1 | 4.29 | 31.1/| 5.88 || 34.1] 7.47 45 132.75 132.88 132.91 133.00 || 22.2|1.17]| 25.2] 2.76 || 28.2 | 4.35 || 31.2 5.94|| 34.2) 7.53 40 132.72 132.83 132.86 132.94 || 22.3] 1.22| 25.3 / 2.81 || 28.3| 4.40 31.3) 5.99 34.3| 7.58 35 132.69 132.79 132.81 132.88 || 22.4] 1.27 | 25.4) 2.86 28.4 | 4.45 || 31.4) 6.04|| 34.4| 7.63 30 132.66 132.74 132.76 132.82 || 22.5] 1.33 | 25.5 2.92 || 28.5) 4 51| 31.5) 6.10] 34.5) 7.69 25 132.63 132.70 1B2=71 132.76 || 22.6] 1.38 || 25.6) 2.97 || 28.6| 4.56 || 31.6) 6.15|| 34.6| 7.74 20 132.60 132.65 132.66 132.70 || 22.7} 1.43 || 25.7 | 3.02 || 28.7 | 4.61 || 31.7 6.20}| 34.7) 7.79 15 132.56 132.60 132.61 132.64 || 22.8] 1.48|| 25.8 | 3.07 || 28.8 | 4.66 || 31.8) 6.25|| 34.8| 7.84 10 132.53 132.55 132.56 132.58 || 22.9)1.54 /25.9 | 3.13||28.9| 4.72 | 31.9) 6.31 || 34.9] 7.90 5 132.49 132.50 132.51 132.52 sb 26.03.18 29.0 | 4.77 32.0)| 6.36|| 35.0} 7.95 i } } [Sucrose+3.392 grams of NHiCl= +99°43°S; (13 grams of invert sugar+3.392 grams of NH4Cl) x2= —33°91° S] Example.—Twenty-six grams of a sample were dissolved in 300 c.c. of solution. Two 75 c.c. portions were taken, prepared for direct and invert polarization, respectively, and finally made up to Ioo c.c. The direct polarization multiplied by 300/75 = 4 proved to be 38-75. The invert polarization multiplied by 4 was — 16-22 at 22-4°C. P—P’ was thus 54°97. Since the original sample was in I /3 normal solution the actual concentration of sucrose was proportional to 1/3 x (P—P’) or 18-32. Opposite 18-32 and under the column “ 75 c.c. taken ” we find the divisor to be 132-63. This is diminished by 1-27 for the temperature correction to give 131-36, which divided into 54-97 gives 41-85 per cent. sucrose. Other Inversion Methods.—There are two other inversion methods which fulfil all the postulates demanded for accuracy. These are the method of inversion by invertase first suggested by Kje'dahl*®? and the alumina-baryta defecation method of the writer. The former method has been developed by O’Sullivan®’, Hudson® and Ogilvie®*, and the routines of the two last named are given here. As carried out by Ogilvie, the sugar material is dissolved in 200 c.c. of water : 100 c.c. of this solution is treated with sulphurous acid to precipitate wr THE DETERMINATION OF CANE SUGAR 521 the lead followed by calcium carbonate to neutrality and made up to 200 c.c. After filtering, aided if necessary by alumina cream or kieselguhr, the direct reading is observed; 50 c.c. of this filtrate is heated with 0-5 gram pressed yeast at 55° C. for 44 hours, made up to 55 c.c. and filtered. This material serves to give the inverted reading. Hudson* has worked out the following routine for preparing an invertase of great activity :— “ To prepare a stock solution of invertase, break up 5 lbs. of pressed yeast, which may be either bakers’ or brewers’ yeast, add 30c.c. of chloroform to it in a closed flask, and allow it to stand at room temperature over night. By morning the solid mass will have become fluid and it should then be filtered through filter paper, allowing several hours for draining. To the filtrate add neutral lead acetate until no further precipitate forms, and again filter. Precipitate the excess of lead from the filtrate with potassium oxalate and filter. To this filtrate add 25 c.c. of toluene and dialyse the mixture in a pig’s bladder or collodion membrane for two or three days against running tap water. The dialysed solution is colourless, perfectly clear after filtra- tion, neutral to litmus, has a solid content of about half of I per cent., an ash content of a few hundredths of 1 per cent., will keep indefinitely in an ice box, if a little toluene is kept on its surface to prevent the growth of micro- organisms, and is exceedingly active in inverting cane sugar. This invertase solution does not reduce Fehling’s solution.” Of this preparation 5 c.c. is used. Hudson performs the inversion at room temperature and effects the de-leading with potassium carbonate or oxalate. In both these schemes, the rate of inversion is very much increased, as was shown by O’Sullivan, by the simultaneous presence of very small quantities of free acid. Hudson states that the maximum activity with hydrochloric acid occurs at a concentration of one-thousandth normal. In the method proposed by the writer®® the solutions required are those of the alumina-baryta method of defecation given earlier in this chapter. To 50 c.c. of material the stated quantity of aluminium sulphate and sul- phuric acid is added, after which the flask and its contents are immersed in a bath of boiling water for 30 minutes to obtain inversion. After cooling, the defecation is then made by the addition of the exact equivalent of baryta, and then, after completing to volume and filtering, the reading in the polari- meter is made. This method has not yet been subjected to independent critical examination. Both of these methods require the determination of the Clerget divisor. Ogilvie found 1-416 as the value for 13 grams in Iooc.c. Both Browne and Jackson and Gillis incline to 1-420 as the value, and introducing the factor for concentration the probable value should be 142-0-+0-0676 (m—13) — : where m is the number of grams sucrose per I00 c.c. and ¢ is the temperature. Methods depending on the Destruction of Reducing Sugars.—Dubrunfaut® first observed that reducing sugars heated with alkalies tended to give a product almost inactive optically, and proposed the application of this ob- servation to analyses. Two later applications are described below. Pellet and Lemeland’s Method.®’—Fifty c.c. of a solution of molasses, containing not more than 5 per cent. of reducing sugars, are transferred to a 300 c.c. flask. To this is added 7:5 c.c. of caustic soda of 36° Baumé 522 CHAPTER XXV and 75 c.c. of hydrogen peroxide Io per cent. by volume. The flask and its contents are maintained at 100° C. for 20 minutes. After cooling and neu- tralizing, clarification is effected with basic lead acetate and the reading obtained, which is intended to afford that due to cane sugar alone. Actually, however, it has been found that the optical inactivity of the reducing sugars is not absolute, although it is reduced to a very small quantity. Mudller’s Routine.8°—Muller obtains the optical inactivity of the reducing sugars as under :—A solution of 25 grams Rochelle salts, 32 grams caustic soda, and 11 grams bismuth subnitrate, is made up to 500 c.c._ Fifteen c.c. of this solution is heated with 20 grams of molasses at 100° C. for 15 minutes. After making up to 300 c.c. with the addition of basic lead acetate, the solu- tion is filtered and transferred to a flask graduated at 100-110 c.c. It is acidified with acetic acid and treated, if necessary, with a little especially prepared decolorizing carbon. The volume is completed to rio c.c., and the filtrate used for the observation. Errors due to Dark Colour after Inversion.—Very often the inverted solution is so dark-coloured that it has to be observed in extreme dilution. A decolorizing effect is obtained by the addition of a crystal of sodium sulphite, by the use of sulphurous acid (Pellet’s process supra), by the action of nascent hydrogen following on the addition of zinc dust to the inverted solution (Lindet®’), and, best of all, by the limited use of bone char. In the strong acid solution the absorption, if any, of sugars by the small quantity necessary is undetectable by ordinary means. Pellet’s sulphurous acid process also affords very light-coloured solutions. The Determination of Sucrose as Invert Sugar.—Since cane sugar is quantitatively converted into equal quantities of glucose and fructose, this reaction affords a process when properly conducted of accurately estimating cane sugar. It may be carried out, for example, as under :— Prepare a solution of the material, such that it contains not more than 2 grams total sugars per 100 c.c. Take 100 c.c. of this material, clarify with basic lead acetate, and de-lead with potassium oxalate, and make up to 200 c.c. and filter. Determine the reducing sugars in this filtrate. Place 50 c.c. of the filtrate in a 100 c.c. flask, invert by any of the processes given above, neutralize, make up to Ioo c.c., and determine the reducing sugars in the inverted solution. An example of this method of calculation to be used follows :—2o0 grams of molasses were dissolved in 1,000 c.c. Fifty c.c. of the de-leaded filtrate in Munson and Walker’s routine afforded 0-1510 gram copper, equivalent to 0:0760 gram invert sugar (using column 4 of Munson and Walker’s table*). Fifty c.c. of the inverted solution gave 223-8 grams copper, equivalent to 0-1174 gram invert sugar (using column 3 of Munson and Walker’s table). The invert sugar present in 50 c.c. of the inverted 0:1760 “liar : TMB bee OLOK94: BEAM: which is equivalent to 0°0794 X 0'95 = 0:0754 gram cane sugar, and the percentage of cane sugar . 4000 _ 100 in the molasses is 0:0754 X ca x peer 30°16 per cent. In this example clarification is effected with basic acetate of lead, and, if the reducing sugars originally present in the molasses are required, this scheme must not be followed. Clarification in this case must be obtained solution is then 0-1174 — * See Appendix. h THE DETERMINATION OF CANE SUGAR 523 with kieselguhr or alumina cream ; where, however, the sucrose is especially sought, more disturbing elements will be eliminated by the use of basic lead acetate. The principles discussed in the chapter on the Determination of Reducing Sugars are equally applicable here. Although quite logical and academically correct, this method does not seem to have been subjected to a critical survey. Some careful analyses of cane juices once made by the writer gave such discordant results as to lead to the supposition that some disturbing factors enter into the determina- ton. The Separation of Sugars in Mixtures.——The method of solution of this problem was first given by Apjohn®® in 1869. It has been developed especially by Browne,*! whose treatment is followed here. I. The reducing power of the sugars is expressed in terms of glucose, the reducing power of which is put equal to unity. The reducing power of the commoner sugars investigated by Browne is given in Chapter XXVI. 2. The optical rotation of the sugars is expressed in terms of cane sugar, the rotation of which is put equal to unity. According to Browne these a o— Cane Sugar ore ae oa I -000 Glucose .. re 32 zo SOZOS Galactose = oe = I-21 Arabinose -= ie ae 1-571 XGyIOSE <> ak = = oor, 0283 Fructose.—The rotation varies so much with temperature that special numbers have to be calculated for each temperature. The factors calculated from the formula of Jungfleisch and Grimbert*? are :-— CONCENTRATION. Temper- I per 2 per 3 per 4 per 5 per Io per 25 per ature. cent. cent. cent. cent. cent. cent. cent. 15 ais I +384 I -385 I +387 I +389 I -390 I -398 1-422 20 : I *341 I +343 I +345 I +346 I +348 I +356 I -380 - 25 x I +299 I +301 I +303 I +304 I -306 I +314 I -338 30 1 +257 I +259 I -261 I +262 I +264 I +272 I -296 Let x = per cent. of a given sugar A. Let y = per cent. of a given sugar B. = glucose ratio of sugar A. Let 6 = glucose ratio of sugar B. Let R = per cent. of reducing a as dextrose. Then ax + hv, =R. : a a Arps 3) Let A = polarization factor of sugar Ae Let B = polarization factor of sugar B. Let P = polarization of mixture, i.e., reading in Ventzke scale in 20 cm. tube for 26 grms. of sugar in I00 c.c. Then Ax + By=P .. os = sg Suppose, as is the most general case, that ‘fie zie is one of cane sugar, glucose and fructose. The cane sugar is determined by the process of double polarization. The difference between the value of the double polarization and the single polarization is the sum of the polarization of dextrose and levulose and P is the equation (2). 524 CHAPTER XXV The values of x and y can then be found by solving the two simple simul- taneous equations. It must be remembered, however, that in cane products unfermentable reducing sugars occur, so that only approximate results can be obtained. The Simultaneous Determination of Cane Sugar and Raffinose. —The official German method due to Creydt™ i is as follows :— The direct reading is taken at 20° C. a The material is inverted according to the official Clerget process. — Let A = direct reading, B = reading after inversion, C = algebraic difference between A and B. . C — 0:493A ; Then Sugar per cent. ere, Raffinose per cent. eat! 1°54 Pieraert’s®! process is as follows :— Ten grms. of material are dissolved in I00 c.c.; this solution serves to give the direct reading. Fifty c.c. of this solution are transferred to a 100 c.c. flask, to which are added Io c.c. of a 20 per cent. solution of citric acid, and the mixture boiled for 15 minutes in a flask to which is attached a reflux — condenser ; after making up to 100 c.c. and cooling, the inverted reading is taken. Then if x and y are quantities of cane sugar and of hydrated raffinose in I00 c.c. of solution, and a and 0 are the readings before and after inversion, x =9:287a — 18-315 y = 3°6594 + 11-6525 The Simultaneous Determination of Cane Sugar, Invert Sugar, and Raf- jinose.—The following scheme is due to Wortmann® :— The reducing sugars are determined and calculated according to the formula R = a , R being the per cent. reducing sugars, C the weight q § p § sug of copper, and g the quantity of material used. The direct and invert readings are then obtained according to the official German method. Then :— 0:9598A — 1°85B —0:-277R 1-5648 A—S X0°3103N 1°85 where A and B are the direct and invert readings. Per cent. cane sugar = Per cent. raffinose = Determination of Fibre in Cane and Bagasse.—Fibre in cane sugar-house work refers to everything insoluble in water. It is therefore to be carefully distinguished from the ‘‘ Crude fibre” of plant analysis or from its chief constituent, cellulose. Methods for its determination are given below, the remarks under ‘‘ Determination of Sugar in Cane ”’ referring to comminution being equally applicable here. 1. Differential Method.—Dry the material and estimate the fibre by difference :— Fibre per cent. = 100 — water per cent. — soluble solids per cent. = THE DETERMINATION OF CANE SUGAR 525 This method may be used with cane after extracting most of the Juice in a hand-mill and determining the soluble solids in the expressed juice. Error is introduced since the composition of the juice remaining is not the same as that expressed. If the cane is comminuted with a Hyatt shredder the juice expressed and retained is of uniform composition due to the rupture of all the cells. In the case of bagasse taken from mills, it is often custo- mary to accept the last mill juice or last roll juice as being the same as _that of the juice retained in the bagasse. , h In the routine of control of bagasse analyses, one portion of the sample is usually used for water determination and one for sugar. The soluble solids may be estimated directly in the sugary extract obtained, and if the analysis, as is convenient, is made with constant quantities of bagasse and water an exact mechanical average of a day’s run can be obtained in one analysis by combining equal quantities from each sugar determination. In a series of tests made by the writer®® it was found that, due to a compensa- tion of errors, the use of the polarization gravity purity of the last mill juice to calculate the soluble solids in the bagasse (cf. Chapter XXVII) gave results almost exactly the same as the use of the dry substance in the extract. 2. Direct Methods——Extract the finely divided sample in a Soxhlet apparatus using water as the solvent, dry and weigh. This method demands the use of very small quantities of material. It is objectionable, since pro- longed exposure to hot water does not obtain in the process of milling, and the object of the analysis is to control this process and not to determine matter insoluble in hot water. A similar objection lies against the use of alcohol as a solvent. The most rational method is the use of cold water. One way of application is to immerse the material for a long period in a linen bag in a stream of water, followed by subsequent pressure and drying. The time required may be much shortened by the use of a hydraulic or powerful screw press. The type shown in Fig. 341 is useful and can be readily con- structed in the plantation workshop. After each pressing the wad of bagasse is loosened, additional water placed in the pot and pressure again applied until extraction is complete. Determination of Ash.—Weigh out from five to ten grams of material in a dish, preferably of platinum. Heat gently till gases no longer escape, and finally at a low red heat. Moisten with a solution of ammonium car- bonate, expel the excess at a moderate heat and weigh. The result is returned as carbonate ash. In place of returning carbonate ash, the sulphate ash is often returned. In this process the preliminary carbonization is effected by sulphuric acid. It is attempted to reduce the results to carbonate ash by a deduction of Io per cent. A whole series of investigations, dating from Violette%*® in 1873 to Ogilvie and Lindfield®’ in 1918, have demonstrated that this correc- tion is generally much too small. The average of the last-named chemists’ results indicate an average correction of the order rather over 15 per cent., with, however, very irregular results, the correction varying from 6 per cent. to 26 per cent., with only four results out of thirty-six giving a value of 10 per cent. or under. The continued use of the ro per cent. deduction is an instance of the per- sistence of a once accepted error in spite of numerous protests. 526 CHAPTER XXV Determination of Gums.—By gums are meant those bodies insoluble in alcohol ; 100 c.c. of juice are concentrated to a volume of about 20 c.c., and poured into Ioo c.c. of go per cent. alcohol containing I c.c. hydrochloric — acid. The precipitate is allowed to settle and washed by decantation with strong alcohol, collected on a tared filter paper, or, better, in a Gooch crucible, and dried to constant weight. The increase in weight gives gums and ash ; the weight of ash is determined, and being deducted from the weight of gum and ash gives the weight of gum. — Shoe: Acidity and Alkalinity.—1oo c.c. of the juice are titrated from a burette By with decinormal alkali ; to the juice a few drops of phenolphthalein solution Sgare threads £ pitch i} an are added, the neutralization of the excess of acid being shown by the appear- ance of a pink coloration. The juice may be conveniently contained in a white porcelain basin. In this method the juice is alkaline to litmus before the appearance of the pink colour. A variation of this procedure is given in Chapter XIII. Carbonated Juice.—The carbonation process, which is but sparingly used in cane sugar factories, requires special methods for its control; an abstract of the methods employed in beet sugar factories may be given here. It is customary to determine the alkalinity of the juice of the first and second saturation in terms of lime as CaO ; as this determination has to be done rapidly, special methods of moderate accuracy are employed. One of the simplest and most convenient is Vivien’s. A standard acid containing 0-875 grm. H,SO, per 1,000 c.c. is prepared: the acid is standardized THE DETERMINATION OF CANE SUGAR 527 against decinormal alkali; Io c.c. of the latter are equivalent to 56 c.c. of the acid, which, when exactly made up, neutralizes volume for volume a solution containing 0-05 grm. lime per 1,000 c.c. ; the indicator employed is phenolphthalein, which is placed in the stock of standard acid. The tube, Fig. 342, is filled to the zero mark, and the standard acid added ; as long as lime is in excess, the juice remains red, becoming finally colourless when the lime is neutralized. Each ten divisions in the tube correspond to 0-1 grm. fme per 1,000 c.c. For juice of the second saturation a weaker acid, only One-fifth the strength of the above, is used. The determination of the total lime in the juice is performed by the usual methods ; I00 c.c. juice are heated to boiling, treated with ammonia in excess, and filtered, if necessary; the lime is precipitated by ammonium . oxalate from the hot solution, boiled for two hours, filtered, washed, dried, and weighed as carbonate or sulphate. The alkalinity of a juice is in part due to caustic soda and potash set free by the action of lime on the salts of the former present in the juice. When it is wished to determine the alkalinity due to lime and to soda and potash, Pellet’s method may be used: 1. Determine the total alkalinity by titration with sulphuric acid, using litmus as an indicator and making the titration at the boiling point. 2. Toa volume of the juice add an equal bulk of alcohol, which will precipitate the lime as an insoluble saccharate ; filter, and in an integral part of the filtrate determine the alkalinity; the latter is due to free caustic potash and soda, but is expressed as lime for purposes of convenience: by determining the total lime, the combined lime can be likewise obtained. Sulphited Juices.—In the control of sulphitation processes, the sulphurous acid free and combined is often determined as such. The means adopted is the titration of the material with a standard solution of iodine in potassium iodide. Starch is used as indicator, an intense blue colour appearing with the presence of free iodine. This analysis does not give acidity, but shows free and combined sulphurous acid. One-hundredth normal iodine contains I*27 gram iodine per 1,000 c.c., and one c.c. is equivalent to 0-32 mgrm. of sulphur dioxide. The Analysis of Limestone and Lime.—It is not general for sugar factories to prepare their own lime, but in the carbonation process it is necessary, and where a supply of limestone is abundant, as in Mauritius and Barbados, it is cheaper to burn lime than to import. The choice of limestone is im- portant, and it is advisable also to keep a check on the composition of the purchased lime. Moisture.—Dry 1-2 grms. to constant weight. Sand, Insoluble and Organic Matter.—Dissolve about I grm. in hydro- chloric acid, filter through a tared filter paper, wash and dry at 100° C., weigh, giving the weight of sand, etc., ignite and weigh obtaining the sand, the difference of the two weights giving the organic matter. Soluble Silica——Evaporate to complete dryness the filtrate from the determination of the sand, etc. ; moisten the residue and again evaporate to dryness, keeping the residue at a temperature of 120° C. for an hour after the residue is apparently dry ; take up with hot water, filter and wash till free of chlorides ; dry, ignite, and weigh the residue as SiO,,. 528 CHAPTER XXV Insoluble Silica.—Mix the residue obtained in the determination of the sand with four or five times its weight of fusion mixture, composed of molecular proportions of sodium and potassium carbonates, and keep at a red heat for half an hour after effervescence has ceased: dissolve out with dilute hydrochloric acid, evaporate to dryness and determine the silica as before. Iron, Alumina.—Mix the filtrates from the determinations of soluble and insoluble silica; evaporate to convenient bulk, add ammonia til alkaline, and heat till the solution smells only faintly of ammonia; filter while hot ; wash, dry, ignite, and weigh the precipitate as Fe,O, + AI,Og. If there be present any large quantity of iron and alumina after decanting off the supernatant liquid, the precipitate should be dissolved in hydrochloric acid and re-precipitated. Lime.—Precipitate the lime in the filtrate from the iron and alumina while boiling hot with ammonium oxalate ; allow to stand for six hours, and filter, wash, dry and ignite the precipitate to constant weight and weigh as CaO ; convert the lime to sulphate or carbonate by evaporation to dryness with either sulphate or carbonate of ammonia and again ignite, and weigh as CaSQ,, or as CaCO, : CaCO; x 0:56 = CaO; CaSO, x 0-4118 = CaO: Magnesia.—Precipitate the magnesia in the filtrate from the lime de- termination as phosphate by the addition of sodium phosphate: agitate the solution violently, and allow to stand for twelve hours ; filter, wash with dilute ammonia, dry, ignite strongly and weigh as Mg,P,0,: Mg,P.0, x 0: 3604 == Me ©: As magnesia is detrimental to the value of good limestone, Geerligs®® has given a scheme for its rapid estimation. Two grams are dissolved in hydrochloric acid, evaporated to complete dryness, the residue brought into solution with hydrochloric acid, boiled after the addition of a few drops of nitric acid, and evaporated to small bulk. An excess of calcium carbonate is added to precipitate iron and alumina, the precipitate filtered off, and the filtrate collected in a flask to which an excess of lime water is added; the flask is filled nearly to the neck and set aside to settle; the supernatant liquid is decanted through a filter, and the precipitate washed by decantation. The precipitate from the lime water contains the magnesia: it is dissolved in hydrochloric acid, the lime precipitated as before by ammonium oxalate, and the magnesia determined in the filtrate. The method of Sundstrom®® for the rapid estimation of magnesia in lime- stones is as follows :— Weigh out one grm. of material into a small dish, add about 100 c.c. water and 25 c.c. of normal hydrochloric acid: heat to boiling, allow to cool and titrate the excess of acid with normal caustic soda, thus obtaining the quantity of acid required to neutralize the carbonates of lime and magnesia. The lime is determined as usual and calculated to carbonate; if the per- centage of calcium carbonate be divided by five, the quotient will give the number of c.c. of normal hydrochloric acid required to neutralize the calcium carbonate. The difference between that found above, as necessary to neutralize the lime and magnesia carbonates, and the calculated number of c.c. necessary for the lime alone, gives the number of c.c. requisite to neu- tralize the magnesia carbonate ; this number, multiplied by 0-42, gives the percentage of magnesia carbonate. THE DETERMINATION OF CANE SUGAR 529 Sulphuric Acid.—Dissolve about five grms, in dilute hydrochloric acid ; separate the silica as before, and in the hot filtrate precipitate the sulphuric acid by barium chloride; allow to settle for six hours, filter, wash, dry, ignite, and weigh as BaSO,: BaSO, x 0-3427 = SO,::BaSO, x 0°5828 = CaSQ,. "és The analysis of the lime is performed exactly as for limestone ; very often large quantities of alkalies are found in the lime, especially if the limestone has been burnt with wood fuel in a short-flame kiln. In addition to the chemical analysis of the lime, a mechanical bulk analysis for the determina- tion of stones, unburnt limestone, etc., may be made}; very considerable quantities of these materials are often found. The following are special methods of lime analysis :-— Free Lime.—Dissolve about one grm. of lime in a 25 to 30 per cent. solution of sugar ; make up to definite volume, filter and titrate an aliquot part of the filtrate with normal acid. Unburnt and Slaked Lime.—Dissolve about one grm. of lime in a definite quantity of normal acid and determine the excess of acid by titration with normal alkali; the difference between the total lime, as thus found, and the free lime, as found above, gives the unburnt lime. Degener-Lunge Method.1°°—Slake about one grm. of lime with water and titrate with normal acid, using phenacetoline as indicator. The point at which the indicator changes from yellow to red marks the neutralization of the free lime ; the addition of acid being continued, the point at which the unburnt and slaked lime is neutralized is marked by a change from red to _ golden yellow. REFERENCES IN CHAPTER XXV. E 1. Int. Sug. Jour., 1907, 99, 481. Plt) SUL POUL... SQLS, 117, 300: Brun int= Sus. fOUur., TOTA,. 16, 112° 4. Chem. News, 52, 280. 5. Bull. Assoc. Chim. Suc., 1893, 10, 656. Gxehi SPA bx, Stas Agric. ser, Bull? 32. 7. ‘‘ Handbook for Cane Sugar Manufacturers,“ New York, 1915. 8. “ Agricultural Analysis,” New York, 1906. One ber 1577, 10)-1043. to. Publicacion Laboratorio chimici dele Gabelle, Rome, 181, 47. 11. Z. fur Instr., 1896, 47. Be.) Bey, 1876.96 497, E531 + 1684, 17, 2234. 3: © 2R: 107,390. 14. Ann. Chem., 232, 169. 15. Jour. Prak. Chem. [2], 25, 114. 16.: - Ber = £880;"53, 1922: 17. Ber., 1889, 22, 265. 18. Jour. prak. Chem. [2], 22, 97. 2N 530 CHAPTER XXV 19. Ber., 1884, 17, 2239. 20. Ann. Chem., 271, 40. 21. ‘‘ Chemie der Zuckerarten,”’ 22. Ber:, 188%, 14; 71511. 23. ‘“‘ Handbuch der Kohlenhydrate.”’ 24. Ann Chim. Phys., 1840, 74, 401. 25. Jour. Fab. Suc., 28, 42. 26. Ann. Chim. Phys., 1899, 17, 125. 27. Erdmann’s “ Journal fiir praktische Chemie, 28. U.S. Bureau of Standards, Bull. 44. 29. Jour. Ind. Eng. Chem., 1915, 7, 216. 30. Zeit. Ver. deut. Zuck., 1917, 68, 407. ” 1242. 31. Jour. Royal Agric. and Commercial Soc., B. Guiana, Dec, 18y5. 325) Ber: 487 7,10, LOA: 33. Ber., 1887, 20, 1848. 34. Ber., 1877, 10, 1414. 35. ‘‘ The Optical Rotation of Organic Substances.” 36. Zeit. Ver. deut. Zuck., 54, 521. 37. .Ann. Chim. Phys. [2], 18, 201. 38. Technological Quarterly, 1889, 267. 39. Jour. Am. Chem. Soc., 21, 268. 40. Java Arch., 1903, 25, 879. 41. W. Ind. Bull., 1901, 3, 140. 42. Jour. Ind. Eng. Chem., 1909, 1, 567. 43. Ber., 1890, 23, 3570. 44. Int. Sug. Jour., 1908, 8, 455. 45. Zeit. Ruben., 1875, 504. 46. Int. Sug. Jour., 1907, 9, 13. 47. Revue Universelle de la Fabrication du Sucre, 1, 45. 48. Int. Sug. Jour., 1903, 5, 376. 49. Jour. Am. Chem. Soc., 1903, 26, 186. 50. U.S. Bureau of Standards, Bull. 3, 135. 51. Jour. Chem. Soc., 1871, 9, 91. 52. Jour. Soc. Chem. Ind., 1916, 35, 201. 63, *C.R., 1883, 557, O57: 54. D. Zucker., 23, 1753- 55. Buil. Assoc. Chim. Suc., 1897, 14, 141. 56. U.S. Bureau of Chemistry, Bull. 116, 73. 57. Int. Sug. Jour., 1916, 18, 402. 58. C.R., 16, 1,000; 22, 438; 23, 256. 59. Jour. Federated Institutes of Brewing, 1, 113. 60. Bull. Assoc. Chim. Suc., 1899, 16, 337. 61. Z. Zuck. Boh., 13, 559; 14, 3433 21, 180. 62. Comptes rendus, Carlsberg Laboratory, 7, 243. 63. ‘‘ Handbook for Cane Sugar Manufacturers,’’ New York, t9t5. 64. U.S. Bureau of Standards, Circular 44. 65. Int. Sug. Jour., 1905, 7, 331. 66. Java Arch., 1908, 16, 3. 67. Bull. Assoc. Chim. Suc., 1897, 14, 74. 68. Int. Sug. Jour., 1915, 17, 213. roo. THE DETERMINATION OF CANE SUGAR “Handbook for Cane,Sugar Manufacturers.”’ “Manuel Agenda du Fabricant du Sucre.” SG tS8Q5;, 27, LS2. Monatshefte fiir Chemie, 6, 198. Ber., 1905, 38, 3808. Cyl EO,.1,000 > 22) 438) 51,235,256: Z. Ver. deut. Zuck., 38, 699. U.S. Bur. of Standards, Scientific Paper, 375. U.S. Bur. of Chemistry, Bull. 73. Java Arch., 1915, 21, 1383. Bull. Assoc. Suc. Chim., 1912, 29, 366. Java Arch., 1904, 12, 321. 531 Transactions of the Eighth International Congress of Applied Chemistry. Comptes rendus, Carlsberg Laboratory, 1, 192. Jour. Chem. Soc., 1891, 46, 61. U.S. Bur. of Standards, Circular 44. Int. Sug. Jour., 1912, 14, 89. Int. Sug. Jour., 1915, 17, 179. Int. Sug. Jour., 1911, 13, 616; Ig12, 14, I6t. Int. Sug. Jour., 1916, 18, 274. Bull. Assoc. Chim. Suc., 1890, 7, 432. Trans. Roy., Irish Acad., 1869, 24, 587. Jour. Am. Chem. Soc., 1906, 28, 4. C.R., 107, 390. Zeit. Ruben., 38, 367. Bull. Assoc. Chim. Suc., 1906, 23, 143. Zeit. Ruben., 39, 766. Ann. Chim. Phys., 1873, 29, 514. Int. Sug. Jour., 1918, 20, 114. “Manufacture of Cane Sugar.’’ Jour. Soc. Chem. Ind., 1893, 16, 520. “Handbook for Beet Sugar Manufacturers.’’ CHAPTER Seat THE DETERMINATION OF REDUCING SUGARS THE method adopted for the determination of reducing sugars. is based on the property possessed by these bodies of reducing cupric salts to cuprous. This property was first used by Trommer!? to distirguish grape sugar from cane sugar, and established as an analytical method by Barreswil?. The method was extended by Fehling®, whose name is connected with the process. Fehling himself concluded that one molecule of glucose reduced five atoms of copper and, accordingly, he specified that the copper solution should contain 34:56 grams of CuSO,5H,O in 1,000 c.c., since he found that Io c.c. of a solution of this strength was reduced completely by 0-05 gram. of anhydrous glucose. This strength of solution is retained in the majority of the formule since proposed. Much work has been done in connection with the process, and very many routines and modifications have been proposed. The essential step forward is due to Soxhlet*, who observed that the quantity of cupric salt reduced is not a constant, but is dependent on the excess of copper which-is present during analysis ; other important points recognised are that the quantity of copper reduced depends on the composition of the copper solution, on the period over which the re-action extends, and on a number of minor points. There are a great number of sugars which reduce cupric salts, and their re- ducing powers? differ ore from another. These reducing powers have been established by experiment and are, following Browne, conveniently referred to glucose as unity (v. infra). The reducing sugars found in cane products are mainly glucose and fructose, with occasionally small quantities of mannose and glutose. The last two sugars are found as the result of the action of alkalies on either the glucose or fructose which occurs naturally. Since the glucose and fructose occur in quantities not far removed from equal, it is well to calculate reducing sugar determinations in cane products as invert sugar. The methods of analysis in use do not separate the reducing sugars as such, but indicate the reducing power calculated as dextrose, invert sugar, etc. Hence all bodies adventitiously present and which possess the property of reducing cupric salts are returned as reducing sugars. The methods in use for the determination of reducing sugars fall into two classes :— (a) A fixed quantity of copper solution of invariable composition is reduced by a fixed volume of the solution containing reducing sugars under fixed conditions. The quantity of reducing sugar used is insufficient to effect complete reduction of the cupric salt. The quantity of cupric salt reduced is obtained by one of many methods, whence the quantity of reduc- ing sugar corresponding to the cupric salt reduced is obtained by reference 532 4 THE DETERMINATION OF REDUCING SUGARS 533 to tables based on the examination of known quantities of reducing sugars. That due to Munson and Walker is given in the Appendix. (6) To a fixed quantity of cupric salt is gradually added the solution containing the unknown quantity of reducing sugar. The addition is continued until all the cupric salt is reduced. Of routines following the first method there are many. Those most in use have been arranged by Brown, Morris and Millar®, by Allihn?, by Defren$ and by Munson and Walker, whose method is selected for description. Munson and Walker’s Method—Two sclutions are required :— I. 34°639 grams CuSO, 5 H,O in 500 c.c. 2. 173 grams potassium Soden tartrate and 51-6 grams sodium hydrate in 500 C.c. The quantity of sodium hydrate present should be controlled by analysis. Place 25 c.c. each of the above solutions in a 400°c.c. Jena or non-sol beaker, followed by 50 c.c. of the reducing sugar solution. Heat upon asbestos gauze so that boiling begins in four minutes and continue ebullition for two minutes. Filter at once and determine the copper in the pre- cipitate by one or other of the methods given below :— The Filtration.—The filtration of the precipitated cuprous oxide may be made through asbestos, contained in a g‘ass tube or Gooch porcelain crucible ; through an “‘alundum”’ crucible; or again through spongy platinum. With these apparatus the filtration is effected under reduced pressure. Paper may be used in the absence of other appliances, but an error is introduced due to the absorption of copper sulphate by the paper. The asbestos used for filtration should be the long fibre variety. It should be prepared for use by digesting with 33 per cent. hydrochloric acid for 48 hours, followed by digestion for an equal period with Io per cent. caustic soda. After washing free from alkali it is preserved suspended in water. The Soxhlet tube, Fig. 343, consists of a glass tube, about six inches long in all; the upper portion is about three inches long and half an inch in diameter, and terminates in a concave bottom, to which is attached a short capillary of about 1/32 in. bore; the lower half is about three inches long and in diameter tapers from 1/2 to 3/16 in. It is prepared for use thus :—A plug of glass wool is placed on the concave bottom of the tube 534 CHAPTER XXVI and above this a pad of asbestos; the plug of glass wool should be about 3 /8 in. deep and the asbestos about 1/16 ; the asbestos pad is most effectively formed by filling the tube with a suspension of the asbestos, and allowing it to settle gradually. It is then drained by the pump, dried, weighed and is ready for use. After the Soxhlet tube has been prepared, it is fitted into the stopper of the filter flask, and filled about three parts full with water; a small funnel is then fitted on to the tube, the stem of which does not quite reach to the level of the water in the tube. The funnel is then filled with water and the pump started ; as the water passes through the filter, the liquid undergoing filtration is poured into the funnel, care being taken to keep the funnel full. When all the copper oxide has been brought into the funnel, the level of liquid is maintained by hot water until all the precipitate has passed into the Soxhlet tube and is continued until the washing is complete. Fic. 344 Fic. 345 A Gooch crucible!® consists of a tall crucible of conventional pattern, the bottom of whichis a perforated disc. It is prepared for use as described for the Soxhlet tube, save that the pad of glass wool is unnecessary. The filtration apparatus used in the laboratories of the Hawaiian Sugar Planters’ Association is shown in Fig. 344. The filter flask is of the form due to Diamond". The tube a communicates with the vacuum pump ; connection with the atmosphere may be made by the cock on the tube 80. The Gooch crucible c is held in the carbon tube d, a tight joint being made by ~ a piece of inner tubing of a bicycle tyre. The filtrate may be discharged through e. The advantages of this apparatus for all vacuum filtrations are obvious. The alundum crucible is made of a porous preparation of ignited alumina. It is prepared for use by boiling in nitric acid. It may be mounted as in Fig. 344; but in order to facilitate washing Spencer! has designed the holder indicated in Fig. 345. The spongy platinum filtering surface due to Munro’? is prepared by igniting ammonium platinum chloride placed on the bottom of a platinum THE DETERMINATION OF REDUCING SUGARS 535 or porcelain Gooch crucible. After ignition the mat of spongy platinum is pressed down carefully with a glass rod and manipulated until a satisfac- tory filtering surface is obtained. Determination of the Reduced Copper. As Cuprous Oxide.—The cuprous oxide after collection by one or other of the above methods is dried to constant weight. The drying is materially accelerated by washing the precipitate first with alcohol and then with ether. As Cupric Oxide—lIf the cuprous oxide has been collected on’ paper the precipitate is, after drying, detached as completely as possible from the paper and ignited in a porcelain crucible. The paper and adhering cuprous oxide are burnt separately, the cuprous oxide being partly reduced to copper. The ash and reduced copper are placed in the crucible, a few drops of nitric acid added, evaporated to dryness and cautiously ignited. If collectedina Soxhlet tube, the narrow end of the tube is connected byrubber tubing to a vacuum pump, and a current of air is sucked through the layer of cuprous oxide. At the same time the tube is heated over a small flame, when the cuprous oxide is seen to glow and is rapidly converted into cupric oxide. If a Gooch crucible has been used, it and its contents are heated at a low red heat, care being taken to prevent the reducing gases of the flame entering the crucible, an end which is best obtained by placing the crucible containing the cuprous oxide inside a second one. As Copper, by Reduction in Hydrogen.—The precipitate of cuprous oxide conveniently collected in a Soxhlet tube is attached to an apparatus generat- ing hydrogen, and a current of hydrogen is passed through the tube. On gently heating the tube, the cuprous oxide is rapidly reduced to metallic copper. According to Perrault! the hydrogen should be purified by being passed through towers containing :— a. Crystals of iodine, mixed with pumice stone. 6. Caustic soda. c. Potassium permanganate 5 per cent., in caustic soda of density 1°32 d. Potassium bichromate in concentrated sulphuric acid. By Reduction in Alcohol—This method was originally proposed by Votocek and Lexa’. As carried out by Wedderburn?® the cuprous oxide is collected in an alundum crucible. Some alcohol is made to boil in a beaker and the heated crucible with its contents placed therein on a stand. The crucible should not be heated sufficiently to ignite the alcohol. After placing the crucible in the beaker, the latter is covered with a clock face. Reduction to copper is rapid and complete. By Electrolytic Deposition—In the United States Agricultural Depart- ment’s laboratory the copper is obtained by electric deposition ; the cuprous oxide is dissolved in nitric acid, and collected in a platinum basin of about 175 c.c. capacity ; after the addition of 3-4 c.c. sulphuric acid, the copper is ready for deposition, which is thus effected by Spencer?’. “Where a direct current is used in lighting the sugar-house, it is the most convenient source of electricity for depositing the copper. The current must be passed through a resistance or regulator in addition to the lamp. A convenient and durable regulator is shown in Fig. 346; ¢ is a glass tube partly filled with water slightly acidulated with sulphuric acid; the wire 4 536 BARD. -) CHAPTER XXVI connects with a platinum sealed into the tube; 0 is a glass tube through which a copper. wire extends and connects with a platinum wire e sealed into this tube. The tube ) may be slipped up and down, thus regulating the distance between the wires e and a, and regulating the current. The twin wire m is separated, severed, and one end d connected with the platinum dish in which the copper is to be deposited, and the other with the regulator b, thence through the acidulated water, and a with the platinum cylinder suspended in the copper solution. Sufficient current for a large number of dishes arranged in sets of four will pass through a 16 C.P. or 32 C.P. lamp. The copper should be deposited very slowly. Usually, if the apparatus be connected when the lights are turned on in the evening, all the copper will be deposited before they are turned off in the morning.” By the Permanganate Process.—In this process the cuprous oxide is dissolved in a concentrated solution of ferric sulphate in 25 per cent. sul- phuric acid ; the ferric oxide is reduced by the cuprous oxide according to the equation : 5 Cu, O +5 Fey (SO), +5 Hy SO,= 10 Cu SO, + 10 FeSO, + 5H,0, and the ferrous sulphate formed is estimated by titration with potassium permanganate. The exact copper value of the permanganate should be determined by, direct assay against a pure preparation of. a copper salt. A solution of a ferric salt will always decolorize a few drops of deci- normal permanganate, and hence a fixed quantity of the ferric solution should be adhered to; by standardizing the permanganate under the conditions of the subsequent assays, this source of error is automatically removed. ~~ - Iodometric Pyrocess.—The reactions involved are :— 2 Cu (CH,COO), + 4 KI=2Cul + 4 KCH;COO + I, 2 Na,S,0,+],=2 NaS,0,;+2 Nal. From the above equations it follows that 126-8 parts of iodine are equival- ent to.63:+5 parts of copper. THE DETERMINATION: OF REDUCING SUGARS 537 ~.. The precipitated cuprous oxide is dissolved in nitric acid, the excess of acid partly removed by evaporation, neutralized with a slight excess of sodium carbonate, and the precipitate redissolved with acetic acid. A slight excess of potassium iodide over that indicated as necessary from the above equa- tion is added, and the iodine determined in the usual way with sodium thio- sulphate, using starch as an indicator. The thiosulphate solution should be standardized against pure electric copper or a pure preparation of a copper salt. Choice of Form in which the Copper is estimated.—If the material analysed is a pure reducing sugar, the reduced copper may be estimated as cuprous oxide, as cupric oxide, as metallic copper or volumetrically with identical results. With materials such as cane molasses, a precipitate other than that of cuprous oxide may be thrown down and hence the weight found will be in excess of that due to the reduced cupric salt. If the cuprous oxide be burnt to-cupric oxide, the only contamination will be that due to ash. The most exact methods are probably the estimation as copper deposited electroly- tically, and as copper estimated iodometrically. The estimation by per- manganate is likely to be falsified by the presence of organic matter in the cuprous precipitate. Meade and Harris!® have shown that the results with cane molasses are almost identical when the estimation is made as cupric oxide, as reduced copper or iodometrically. - Glucose Ratio of Sugars and Munson and Walker’s Table.—Munson and Walker’s table concerns invert sugar, glucose, lactose and maltose. By establishing the reducing ratio of the sugars, that for invert sugar may be used for any sugar. Accordingly, only the values for invert sugar and invert sugar and sucrose are recorded in their tab!e in the Appendix. These are Specially applicable to cane sugar work, where the mixture of reducing sugars is never far removed from invert sugar. The table has also been altered by substituting the weight of cupric oxide for cuprous oxide. _ The reducing ratios of the commoner reducing sugars compared with anhydrous glucose as unity are thus given by Browne!® :— Glucose, 1-000; Fructose, 0-915; Xylose, 0-983; Arabinose, I-002 ; Invert Sugar, 0-:957; Galactose, 0-898; Lactose, H,O, 0:678; Maltose, H,O, 0-620. The Effect of Cane Sugar on the Determination of Reducing Sugars.— Cane sugar, by itself, has only a very small reducing power, but in the presence of reducing sugars, especially when the cane sugar is in great excess, the effect is sufficient to invalidate the analysis. This behaviour is allowed for in Munson and Walker’s tables, and the analysis should be soconducted that the quantities of material taken are substantially those for which these tables are drawn up. Preparation of Materials for Reducing Sugar Assay.—Many cane sugar products, without previous treatment, afford a copper precipitate which is incapable of filtration. Certain formal directions specify a clarification with basic lead acetate, the use of which is, of course, irrational (cf. Chapter XXV). Further, the precipitated lead-reducing sugar compounds are not broken up by the addition of sodium sulphate, but the error is accentuated, since, with an excess of lead, a further precipitation of lead-reducing sugar 538 CHAPTER XXVI compound occurs. Neutral lead acetate is frequently specified to be used as a Clarificant followed by the removal of the excess of lead by sodium carbonate, oxalate or sulphate. The use of the first-named salt is irrational since a basic lead acetate will be formed resulting in the precipitation of reducing sugars. In addition, Meade and Harris!® have shown that the results of the analysis are affected by the quantity of neutral lead acetate ‘used, and also by the de-leading agent employed. They recommend, instead, that kieselguhr should be employed as the clarificant in quantity sufficient to give a clear filtrate. To this recommendation the writer would add that alumina cream or intra-precipitation of alumina is equally efficacious. Standardization of Solution—The quantity of copper reduced depends on the exact composition of the solution, particularly on the amount of alkali present. It also depends on the time of boiling and even on the surface area of the beakers in which the reaction takes place. Every fresh prepara- tion of copper and alkaline tartrate should therefore be standardized under the precise routine of the analyst against a pure preparation of glucose or invert sugar. From the results of the standardization a correction may be applied to the quantity of reducing sugar, as found from the correspondence in the table employed. For example :—The analyst has found that with his preparations and routine (all intended to conform with those of Munson and . Walker) o-1I40 gram invert sugar corresponds to 0:2203 gram copper, the value found by Munson and Walker being 0-2176 gram copper; he should therefore in subsequent analyses with this stock material multiply the weight of copper found by 0-988 before using the correspondence in Munson and Walker’s tables. Direct Volumetric Methods.—The original process for the determination of reducing sugars was a volumetric one, and as such it is described in the older textbooks. It was also accepted that no correction was necessary for variation in the concentration of the reducing sugar solution, or for the pres- ence of cane sugar. Neglect of these points tended to discredit volumetric processes. Ling,?° however, has always supported the use of such, and in conjunction with Rendle and with Jones has arranged tables for the correc- tion of the errors so introduced. His treatment of the question is followed below. Solutions Required.—(a) 69:3 grams CuSO,5H,O in 1,000 c.c. (b) 142 grams caustic soda and 346 grams Rochelle salt in 1,000 c.c. For the analysis 5 c.c. each of the above are mixed immediately before use. A solution of I-o gram of ferrous ammonium sulphate and 1-5 gram of ammonium sulphocyanide in Io c.c. water and 2’5 c.c. hydrochloric acid is used as indicator. This solution is decolorized if necessary with zinc dust, and is preserved out of contact with air. The treatment with zinc dust may be repeated if necessary, but eventually it will be necessary to make up a fresh stock. In the presence of cupric salts an intense red coloration is produced. The analysis is performed by adding gradually the reducing sugar solution from a burette to the boiling Fehling solution. The reducing sugar solution should contain not less than 0-1 or more than 0:25 gram reducing sugar. The approach of the complete reduction of the cupric salt is indicated by the waning blue colour of the solution. When this is no longer distinctly blue, a drop of the unfiltered liquid is withdrawn by a glass rod, placed on a THE DETERMINATION OF REDUCING SUGARS 539 white tile, and brought in contact with the indicator. The exact end-point is thus obtained. Often it is well to make a preliminary test to obtain the approximate result as a guide and to follow this by the analysis of record. A less convenient method of testing for the presence of unreduced copper consists in filtering off a few drops of the liquid, acidifying with acetic acid, and adding a drop of a solution of potassium ferrocyanide. The filtration from the suspended cuprous oxide may be made by using very small filter papers folded into a cone and held in the liquid by a forceps. The clear liquid will pass into the cone whence a drop may be removed by means of a fountain pen filler. Alternatively, a Wiley”! filter tube may be used. This consists of a glass tube, on the end of which a flange has been formed. Over the flange is stretched a piece of linen, on which is formed by suction an asbestos film. On applying suction to the tube a clear filtrate passes through which can be tested with the indicator. Knorr®! modified the Wiley tube by sealing in a platinum disc. Ling?® has prepared the following table giving the relation between reducing power and concentration of the solution analysed :— C. C. Fehling’s Invert Sugar C. C. Fehling’s Invert Sugar solution used. in I00 C.c. solution used. in I00 C.c, 21 aye 0 -24IT 32 ae 0 -1629 22 0 2311 33 . 0 1583 23 0 2218 34 0 +1539 24 0 °2132 35 0 *1497 25 O +2052 36 0 +1458 26 0 1980 37 O+I42I 27 0 *IQIO 38 0 +1385 28 0 +1846 39 0 +1349 29 0 -1787 40 0 +1319 30 0 +1731 41 o -1288 31 0 +1678 42 0 +1259 The error due to the presence of cane sugar may be eliminated by the use of the annexed tables, where column A gives the percentage of invert sugar on total sugars present; column B gives the percentage of invert sugar as found by experiment, using the table immediately above; column C is B — A, which gives the error (due to the presence of cane sugar) in the percentage of invert sugar so found. This table is referred to 0-2 gram of invert sugar per I00 C.c. A. B: C. Js B Gc 95 ‘2 95 °3 O°! -11 8 I2-°IO 0 +30 87-0 87-1 O°! 10 +3 Io -60 0 +30 80-0 80-1 O°! Q°I 9°45 0°35 66 -7 66-9 0:2 WES 7°76 0 +26 50 -O 50 *4 O°4 6-2 6°44 0°24 ZA) 40 °4 04, 39 4°05 0°25 33°4 33 °8 04 2°8 3°04 0 +24 28 -6 29-0 O°4 2-0 2°23 0 +23 25:0 25 °4 0°4 I -O I-14 0-14 22 °3 22°F 0-4 0-8 0-92 O°I2 20-0 20 °*4 0-4 O°7 0-80 o-IO 13 °8 14-10 03 540 1 CHAPTER XXVI _ It is evident that the greatest percentage errors occur when the cane sugar is in large excess, as in the analysis of raw sugars. _The remarks already made concerning the necessity of standardization under the exact working conditions apply equally here. Detection of Small Quantities of Reducing Sugars.—Since cane sugar itself slightly reduces Fehling’s solution this material is not adapted to detect small quantities of reducing, sugars in the presence of cane sugar. This may be done by means of Soldaini’s solution, which, as used by the U.S. Bureau of Standards, contains 297 grams of potassium bicarbonate and I gram copper sulphate in 1,000 c.c. Ten grams of cane sugar give on two minutes’ boiling with 50 c.c. of this solution only I-I mgrms. of cuprous oxide. A very delicate test for the purity of a sample of cane sugar is also afforded by this means. Optical Assay of Fructose.—The rotation of fructose falls very rapidly with rise of temperature. Hence by observation of the optical activity at different temperatures the amount of fructose can be estimated. For each 1° Centigrade rise in temperature and for I gram fructose in I00 c.c. the rotation falls 0-0357° Ventzke. Assuming that the other sugars present are not atiected, the amount of fructose follows directly. : Individual Estimation of Reducing Sugars in Mixtures.—Aldose sugars may be estimated-in the presence of ketose sugars, and vice versa, based on their different behaviour towards the halogens, the former being readily oxidized, while the latter are but little affected. Romijn’s?* method is as below :—Ten grams of iodine and forty grams of borax are made up to 1,000 c.c. Twenty-five c.c. of this solution are mixed with the same quantity of a solution of the mixed sugars containing not more than 0-15 gram. The mixture is then kept for from 16 to 22 hours in a stoppered flask in a thermostat at 25°C. After oxidation is complete the excess of iodine remaining is determined by means of sodium thiosulphate, as in the iodo- metric determination of copper described already in this chapter. For two atoms of iodine, one molecule of an aldose sugar is accepted. A more direct and convenient method of applying this reaction is that of Herzfeld and Lenart,2* conducted as follows :—To 50 c.c. of a solution containing not more than I per cent. of ketose sugar, bromine is added in quantity I c.c. for each gram of aldose sugar present. After standing 24 hours at room temperature the excess of bromine is evaporated off, and the ketose sugar determined in the residue. In either of these methods determination of the total sugars present gives data to calculate the undetermined sugar. Ammoniacal lead acetate, prepared by adding ammonia to lead acetate until the opalescence which forms just disappears, precipitates glucose and fructose from solution ; the sucrose remains in solution as a soluble lead compound. The precipi- tated lead-sugar compounds are suspended in water through which is passed a current of carbon dioxide; the lead glucose compound is decomposed, and is removed by filtration; the lead fructose compound may then be f THE DETERMINATION OF REDUCING SUGARS 541 decomposed by hydrogen sulphide. This method was used by Winter*4 in pioneer work on the nature of the sugars of the cane, but is unsuited for ordinary laboratory routine. NOR OOF eS Sat Core team tet Io. REFERENCES IN CHAPTER XXVI. Ann. Chem., 39, 360. Journal de Pharmacie [3], 6, 601. Ann. Chem., 72, 106; 106, 75. Jour. Prak. Chem. [2], 21, 227. Jour. Am. Chem. Soc., 1908, 28, 263. Jour. Chem. Soc., 1902,.71, 281. Jour. Prak. Chem. [2], 22, 46. Jour. Am. Chem. Soc., 1898, 18, 751. Jour. Am. Chem. Soc., 1908, 28, 663. Chem. News, 37, 181. Chem. News, 74, 283. ‘‘ Handbook for Cane Sugar Manufacturers,’’ New York, 1915. Jour. Anal. Chem., 2, 241. “Le Rhum,” Paris, 1899. Chemiker Zeitung Repertorium, 21, 234. Jour. Ind. Eng. Chem., 1915, 7, 610. ‘‘ Handbook for Cane Sugar Manufacturers,’’ New York, IgI5. Jour. Ind, Eng. Chem., 1916, 8, 504. “‘ Handbook of Sugar Analysis,’’ New York, rogIt. Analyst, 30, 182; 33, 160. “ Agricultural Analysis,’?’ New York, 1906. Zeit. Anal. Chem., 36, 349. Zeit. fiir Zucker., 1918, 68, 227. ““ Agricultural Analysis,’’ New York, 1906. GHA PPER oe Fh THE CONTROL OF THE FACTORY ce By the term “ chemical control”’ it is not meant that the control of the factory should be given over to anyone but the manager ; but by it is implied a system of routine analysis and sampling combined with an organized scheme of technical book-keeping whereby the chemist can detect, locate, correct, and hence control any imperfections of the process of manufacture. To obtain this end three postulates are demanded: correct weights, correct samples and correct analyses ; neglect of any one of these three will vitiate the control, but as shown in some sections below incorrect measure- ments may, in some cases, be indicated from analytical data alone and it is not the least of the duties of the chemist to check the weights against the analyses; this is particularly the case where the cane is bought or where its weight forms a basis of payment for the labour. In addition, the sugar factory should be regarded as a huge chemical experiment, and efforts should be made to account for every pound of sugar entering the factory. The points necessary to the control as defined above are discussed below. Determination and Definition of Weights. Cane.—For the purpose of the technical control cane should be defined as everything which goes through the mill, including the dry leaves and other foreign matter. In some cases where cane is purchased it is customary to make an arbitrary deduction from the recorded weight; and executives, not without reason, may object to the appearance of two cane weights as likely to be a source of misunderstanding with an ignorant population. No difficulty attaches to the weighing of cane, which is conducted pre- cisely as for other material. In Cuba the transfer derricks (Plate XIX) are now often fitted with means for weighing the suspended load of cane before it is dumped into the cars. Juice.—The weight of the juice is often determined on beam scales, two tanks, one filling and one emptying, being employed. These apparatus are provided with appliances which print the weight on tickets at each weighing. In many houses automatic self-recording weighing machines, of which the Richardson! may be taken as an example, have been installed with very satisfactory results. The Baldwin and Hedemann machines described in the first edition have found no extended use. The Richardson weigher is shown in Fig. 347. It consists of a strong iron frame, supporting the equal- armed beam A ; to one end of the beam is hung the weighing tank or hopper, B, in which the liquid is carried, and to the others is suspended the counter- balance or weight box, C. 542 THE CONTROL OF THE FACTORY 543 The quantity determined on is represented by the weights placed in the weight box, which furnish the power to actuate the scale. The supply of the liquid into the scale is from the upper hopper tank, D, which is fed by the feed, E, which forms its joint by descending on to the rubber seating, F. This valve is raised through the plunger, G, by the power of the weight in the box, C, and is controlled by means of the levers, K and L, which form a dead centre. FIG. 347 A full stream of liquid enters the weighing tank, B, until its weight in the hopper begins to off-set the counterpoise, and in so doing releases the plunger, G. The valve now partially closes and only a reduced flow enters the hopper until the balance is reached. This final flow may be enlarged or reduced, by means of the screw J. At the balance, the beam trips the arm, W, and the valve completely closes. The lever, L, engages with the lever, N, breaking the lock formed by the dead centre of levers N and M, and the weight of the liquid opens the outlet valve and the contents of the tank are 544 CHAPTER XXVII discharged. This discharge is controlled by the conical valve, H, which also has a rubber seating, and thus a joint is formed against the wall of the tank at S. ora It will be seen that the liquid is delivered on to the tun-dish, Q, connected with the outlet valve, H, and the weight of the liquid on this tun-dish has the effect of holding the valve open until all the liquid is drained from the weighing tank. This valve returns by means of the weighted lever, M, when relieved of the weight of the liquid on the tun-dish, Q. The sides of the tank are continued down to prevent splashing, and a mechanical counter, R, registers every weighing. Another juice weigher, the Leinert Meter (7g. 348) consists of two tanks of equal capacity A, and A,; they are balanced on a knife-edge B; at C isa syphon pipe and at D is arranged an adjustable counter-weight. The juice discharges from the pipe E into the gutter F, which is tilted one way or the other by the movements of the tanks. The juice flows into one tank until the weight is just sufficient to counterpoise that at D, when the tank tilts Fic. 348 into the position shown by the dotted lines and aliows the juice to discharge through the syphon ; simultaneously the gutter is tilted and directs the flow of juice to the other tank. The number of fillings is registered by an auto- matic counter. In the absence of these devices resource must be had to measurement in tanks. These should be provided with an overflow, and the juice should be allowed to enter until it discharges over a wide weir, the excess being allowed to return to the pump suction. To reduce the error in measure- ment, tanks are sometimes built with a constricted upper portion. It is not a hard matter to accurately gauge a tank or to fill it to a constant level, but the accurate volume measurement of juice requires attention as regards the following points :—xz. Allowance must be made for the juice retained by capillary attraction at each emptying. 2. The volume of air entrained must be ascertained. This is best done by filling the tank to the overflow, and allowing to settle for some time and noting the decrease in volume. 3. The suspended solid matter must be ascertained and allowed for. The corrections for these three sources of error can only be average THE CONTROL OF THE FACTORY 545 corrections, as it is not feasible to make the determinations except at infre- quent intervals. The error due to the suspended matter may be eliminated by regarding it as juice and making the analyses on the whole material, but it is much more satisfactory to make the analyses on juice from which the suspended matter has been removed and to correct the recorded weight on volume of juice. When the weight of juice is recorded from the number of tanks filled, it is well to attach to each tank a counter operated by the movement of the valves so as to check the record of the operator. A device such as that due to Horsin-Déon,? is also useful to demonstrate that the tanks have been properly filled and emptied, and also toserve asacounter. In this apparatus (shown diagrammatically in Fig. 349) a chain, aa, transmits motion from a Fic. 349 ; float, 6, to a drum, c, which revolves as the float rises and falls. A pinion, d, on this drum drives a rack, e, which carries a pencil bearing on the cylinder, g, rotating once in twelve hours. Press Cake.—In cane sugar houses the weight of press cake only averages I per cent. of the cane, and sufficient accuracy is obtained by finding the average weight of one cake and thus obtaining the weight from the record of the presses dumped. Raw Sugar.—This material is weighed on ordinary scales or more con- veniently is filled into the bags from an automatic weighing machine, of which there are several satisfactory forms on the market. These machines also keep a tally of the number of bags filled. Molasses —The most satisfactory method is to weigh the molasses on beam scales, using two tanks, one filling and one emptying. If the molasses is shipped in tank cars, their contents may be determined by weight as for any other material, or less accurately the average net contents of a car may be determined. The measurement of molasses in storage tanks is very diffi- 20 546 CHAPTER XXVII cult owing to the depth of foam or scum which forms on the surface. The following method of determining the real level was shown the writer by Mr. H. C. Sayre. To one end of a rod of wood a weight is fixed, such that the rod will sink in molasses to a mark, the position of which on the rod is noted. This rod suspended from a cord is let down into the storage tank until it meets and floats in the molasses. The length of the string from the top of the tank is observed, whence is obtained the level of the molasses below the top of the tank. The foam, which may be a foot in depth, has a very small influence on the depth to which the weighted rod sinks. Automatic Record of Density.—Langen’s apparatus? is shown in Fig. 350. The juice enters a containing vessel, f, overflows at d and passes away at h, thus maintaining a constant level. Inside the narrow central part of the vessel is a tube, e, to the lower end of which is attached a rubber ball, g. This tube is filled with water, and the height to which the water rises is dependent on the pressure on the ball, which is in turn controlled by the density of the material in the vessel f. The level of the water is recorded through a float, c, carrying a pencil, a, bearing on the rotating cylinder, 0. The lower part of the tube, g, is formed into a spiral, so as to equalize the temperature of the water therein and the juice in the vessel f. This apparatus, or others working on similar principles, are very useful to obtain a record of the density of the last mill juice and of the syrup, with the object of checking the care exercised by the operatives. -They do not eliminate the necessity for taking regular samples, the results of the analysis of which give the figures entered in the records. Sampling.—The control is vitiated by inaccurate sampling equally with inaccurate analyses. The degree of exactitude demanded depends on the purpose for which the sample is taken. General information only may be required or the sampling may form part of a process on which a calculation of recovery and losses is based. The second object requires as exact a sample THE CONTROL OF THE FACTORY 547 as the circumstances will allow, whilst a less degree of exactitude is permis- sible in the first case. Examples of the first case are found in the sampling of the first mill juice, when required to give the executive an idea of the nature of the material being worked up, and in the determination of the purities of material in process made as a guide for regulating the operations of boiling. The methods of sampling in use may be defined :—r. Intermittent from a continuously flowing material. 2. Continuously asin xz. 3. Intermit- tently from containers, the quantity taken being proportioned to the quantity of material in the container. The first method should only be used when general information is required. The second method is accurate provided the sample drawn is proportionate to the rate of flow of the material. The third method is the most accurate. Various methods and devices are described below :— If a current of liquid be allowed to impinge on a wire pointing downwards, a very small portion of the liquid will trickle down the wire, and may be col- lected in a container. The quantity drawn depends on the diameter of the Fic. 351 wire. This method is very conveniently used for taking samples of juices from a roller, as when taking first expressed juice, or last mill juice. The wire is supported against the roller and the neck of the container. It is conven- ient to insert a funnel in the opening of the bottle so as to mimimize error from evaporation. Wire sampling may also be readily adapted to juices pumped in pipes, by allowing a jet of juice to impinge on a wire, the excess of juice flowing back to the pump suction. Continuous samples may also be taken from pipe lines by employing the arrangement shown in Fig. 351, thus dispensing with the wire. Samples from gutters may be drawn by means of a toy pump. A form of automatic sampler described by Maurice Pellet? is illustrated diagrammatically in Fig. 352. This is intended to be operated off the mill shaft through a crank, so that at each revolution the bucket dips into the Juice gutter, and on its upward motion capsizes its contents into a container. A device due to Davoll* is shown in Fig. 353. A spoon with a channel running through its haft communicates with a hollow shaft caused to rotate by belt drive from some adjacent machinery. The spoon is covered with gauze so as to keep out fibre. Other gutter samplers are built as undershot wheels, and are caused to rotate by the flow of the juice. They thus auto- matically proportion the sample taken to the rate of flow. A form due to 548 CHAPTER XXVII Bacher® is shown in Fig. 354. The wheel has eight paddles, two of which are provided with cups to collect the sample. In sampling from gutters it must be remembered that mixture may not be complete, when juices of different composition, such as mill juices, are led into the same gutter; indeed, the unequal composition may sometimes be traced after the contents of the main gutter are discharged into a tank and even in the pipe line after passing through the pump. Sampling from Containers.—The most accurate sample is obtained by taking an aliquot portion from each container of juice, syrup or molasses. If, as should be the case, all containers are of equal capacity each sample taken is of the same volume. The continuous weighing machines on the market are arranged to take a sample when dumping their contents. Tanks on beam scales, or used for volume measurements, may easily be fitted with a pet cock through which x. sample is drawn, and which is opened by the movement of the main valve, chus avoiding any forgetfulness on the part of the attendant. Fic. 352 Fic. 353 Sampling of Sugars.—The sugar sample is usually taken by the weigh- master, who throws a pinch of sugar from each bag into a container. A very convenient continuous automatic sampler (Fig. 355) adapted to the bucket elevator was devised for the writer by Sr. Sacramento Bareto. A stout horizontal rod, a, was attached to +the sides of the elevator. To this rod was loosely hung a hinge, b, with flattened end. This last was of such a length that it projected about one half-inch over the lips of the buckets c. The latter in their upward motion struck the swinging hinge, whereby a few crystals of sugar were “‘ flicked” backwards and fell into a container, d, the position of which was determined by trial and error. In its motion after being struck by a bucket, the rod b hit against a third horizontal rod, e, and thus fell back on to the next bucket in succession. The container was made with a conical mouth and was provided with a sliding bottom, through which all the material collected over any period could be removed. Sampling of Press Cake-—Unwashed cakes are of nearly equal composi- tion throughout, but washed cakes show large variation in composition. THE CONTROL OF THE FACTORY 549 They must therefore be sampled in numerous places, samples being taken also from many cakes. Sampling of Bagasse.—The sampling of bagasse, which is very important, is also the most unsatisfactory problem met with. It is of unequal composi- tion due to the structure of the cane, to unequal distribution of added water, and to inferior crushing at the extreme ends of the rollers. To avoid error from these causes the sample should be taken from across the whole width of the rollers. The subsequent treatment depends on the method of analysis used. If small quantities—r1oo grams—are used in the analysis, it is im- perative that a large sample of, say, a kilogram be chopped to a fine meal in some machine, such as a sausage-meat chopper. This process is trouble- some and invariably entails some alteration in the composition of the material. It is much better to make the analyses on a larger quantity, say, one kilogram, and to avoid the sub-sampling. With efficient modern milling, bagasse is in a suitable condition for analysis without further division. Bagasse taken from the earlier mills of a train for special analyses must, of course, be reduced to a fine state of division. Sample Re servot r. The sampling of bagasse cannot be automatic, nor yet can it be safely preserved for analysis. Its composition depends on the feed of cane and on the quantity of water used. The samples should then be taken under normal working conditions and should indicate as the result of their analysis what has been the average, and not what was the composition of bagasse at any particular moment. In the system of operating cane sugar houses lack of appreciation of this point often leads to friction between the engineer and the chemist, both often forgetting that they are merely individual units in a complicated machine. The number of samples and analyses necessary to obtain an average result reasonably accurate will depend on the variation between individual analyses, and this variation will depend on the variation in the raw material, the regularity of feed, and the general oversight exercised on the operation of milling. An hourly or at the least a two-hourly sample and analysis is generally necessary. Sampling of Cane.—In general cane cannot be satisfactorily sampled since the variation from stalk to stalk is great, and also the composition of individual stalks varies from butt to top. When circumstances arise such 550 CHAPTER XXVII that it is desirable to make an analysis of cane, a Jarge number of stalks must be taken and the finally completed sub-sample must be representative of the length of the canes. Division of the stalks into quarters by splitting longitudinally is easily done with a sharp heavy knife. If cane is defined as the material delivered to the mill the accompanying trash and dry leaves are therein included. In sampling, the proportion of trash to clean cane should be determined and its analysis made separately. In general, when the composition of the cane from a certain field is re- quired it is better to isolate a car load on the carrier and to take samples of the juice and bagasse rather than to attempt to obtain a sample from so unsatisfactory a material. Preservation of Samples—The preservation of samples composited over periods as long as twenty-four hours adds materially to the capacity of the Fic. 355 chemist, and provided the compositing is intelligently done does not detract from the value of the control. Indeed a careful analysis of a twelve-hour sample is of more value than twelve hourly analyses necessarily performed in haste. The two antiseptics employed to prevent fermentation are mercuric chloride and formaldehyde. Of the former 25 mgrms. and of the latter I c.c. of a 40 per cent. solution per 100 c.c. of sample is used. The above quantity of mercuric chloride causes an increase of 0-05° Brix, which correction is applied to the readings of the instrument. In taking samples of juices it is advisable to duplicate the sample, using one for the determination of solids and one for sugar. The writer uses formaldehyde as the preservative of the first, diluted to nearly that specific gravity which experience has shown the juice will be. Correction for the presence of the preservative in the Brix determination is thus eliminated. The sugar sample is preserved with dry lead acetate, used in such quantity as is necessary to defecate the whole sample. It should be remembered that the use of antiseptics does not give an excuse for the neglect of cleanliness. THE CONTROL OF THE FACTORY 551 Syrup does not require any preservative provided the containers are scalded each time after use. Bagasse may be preserved for several hours by the liberal use of formalde- hyde. This material is, however, best analysed immediately after sampling. Control of the Milling Plant.*—The control of the milling plant is concerned mainly with the determination of the quantity of juice and sugar extracted from the cane, and with an oversight on the efficiency of the operations made in this connection. The control may be positive, i.e., with the actual de- termination of the weights of cane, mixed juice, added water and bagasse; or inferential when the above quantities are partly determined from the results of analyses. Before giving the methods used it is necessary to explain at some length various points connected with the constitution of the cane. The juice in the cane is not of uniform composition and may roughly be divided into pith juice and rind juice. The pith juice is that of higher density and is expressed first. Hence the average composition of all the juice in the cane is lower than that first expressed. In addition to juice proper, there is the watery protoplasm of the living cell and water of constitution loosely combined with the fibre which perhaps exists in a hydrated state. This constitutional water is expelled on drying at 100° C. The writer prefers to regard for the purpose of technical control the proto- plasmic and constitutional water as juice and to define as the absolute juice of the cane everything not fibre as determined directly or indirectly (by difference) by drying to constant weight. As the result of analyses he found on an average that the relation, Brix of first-expressed juice < 0°975 = Brix of absolute juice, held. This figure refers to an extraction of about 60 per cent. on the weight of the cane. The very able chemists in Java have taken the opposite view, and determine and record the constitutional water as distinct from the juice. The method there employed is as follows: The last mill bagasse is pressed in a hydraulic press at a pressure of about 600 lbs. per sq.in. The expressed juice is assumed to be residual juice and its percentage of sucrose is deter- mined. Simultaneously the percentage of sucrose and of water in the bagasse is determined by drying, and, of course, the constitutional water is here included. Let the constitutional water per unit of dry fibre be w, then y = 1I— m — mw, where ¢ is the residual juice and m is the fibre per unit of bagasse. If the residual juice contains s sugar and the bagasse contains b sugar, then 6 = s (I — m — mw). Solving this equation w is found, giving the quantity of constitutional water in the bagasse. The methods used by the writer follow. In practice a number of cases may occur, such as :—z. The weight of mixed juice alone is known. 2. The weight of cane and mixed juice is known. 3. The weight of cane, mixed juice, and added water is known. Case 1.—The complete solution of case 1 demands a knowledge of the percentage of fibre in the cane and the application of the equation :— Cane + Water = Mixed Juice + Bagasse. Data for solution of this equation can be obtained from the ordinary routine analyses and one measurement as under. Let f be the fibre in cane, m be the fibre in bagasse, B., Bj, Be * The first attempt to give a system of mill control is, the writer believes, to be found in Pimienta’s “‘ Manuel el cultivo del cafia de azucar,’’ Madrid, 188r. 552 CHAPTER XXVII be the degrees Brix respectively of the absolute juice, mixed juice, and residual juice in the bagasse. Let the weight of canes be unity and the weight of the mixed juice be a; from well-known equations the weight of bagasse is = and the weight of the juice in the bagasse is - (I — m). ‘3 The total weight of juice is then a + a (r — m). The solids in the total weight of juice then are see reas a By + on (I m) By and the total solids per unit of juice are a B; rae (rx —m) By, m a+l—m) _aBm+f(i—m) Bn ~ am-+f(r—m) The water added per unit of original juice in the cane is then B, —a Bi m+f(t —m) Bn am +f (I —m) a Bm +f (i —m) Bn am+f(I—m) _aBem+fBe—fmB,—a Bim —f Bu +fm Bm a aB;m+f Bn —fm Bn Let this expression be denoted by P. The weight of original juice is 1 —f; hence the total weight of added water is (I —f) P. Hence from the equation Canes -++ water = mixed juice + bagasse I + (1 —fP=at. A numerical example will show the application of this equation, The following analytical data (expressed per unity) were found :— B, 0:209 (1.¢., 20°9 Brix); fo-119; mo-487; B;0:190; By 0-088; Bae m From these quantities P is found to be 000934 + 0:0074 0°0925a +- 0:0054 hence 0-2443 and 1 — f = 0-881. whence 0:0093a + 0:0074 Sy = 5 nae B80( ee -- ray, Ceres Solving this equation a is found to be o-g1I5, or the weight of mixed juice is 91-15 per cent. on that of the cane. The weight of bagasse is 24-43 per cent. on cane, so that, putting the weight THE CONTROL OF THE FACTORY 553 of cane equal to unity, the weight of the added water is found from the equation : I +w =0-9115 + 0:2443, whence w = 0:1558, or the added water is 15-58 per cent. on cane. By this method, if any one of the weights of cane, mixed juice, added water or bagasse be known, the others can be obtained. The calculation of the extraction, etc., once the actual quantities have been determined, is made as shown below under Case 2. Case 2.—This is the case which usually occurs in modern factories, namely the weight of cane and of mixed juice is known. The fibre in the cane is not determined, but is obtained by calculation from the observed fibre in bagasse. The method of calculation is best shown by a completely worked-out example :— Weight of cane - Weight of mixed juice IIr5 <3 tons. 1016-6 tons or gI-1I5 per cent. on cane. Absolute juice aurees 20-9 Brix. Mixed juice -.. =. -. 19:0-Brix,; 16°23 per cent. sugar. Last mill juice* - - 7-0 Brix, 5-74 per cent. sugar, 82-0 purity. Bagasse - - - - 46-8 per cent. water, 3-69 per cent. sugar. Then :—Soluble solids in bagasse Be: Na = 4°50 per cent. Fibre 82-0 per cent. in bagasse = 100 — 46-8 — 4:50 = 48-7 per cent. Put the weight of cane equal to unity, and, since the soluble solids in the cane are equal to those in mixed juice and bagasse, it follows that is 0-487 (1 —/f) X 0-209 = 0-9gII5 X 0-190 + x 0-045, where / is the fibre per unit of cane. Solving, f is found to be 0-I1g or II-g per cent. on cane. The weight of bagasse is san = 0+2443 or 24-43 per cent. on cane.t From the relation, Canes + water = mixed juice + bagasse Bae == O GETS... “= "0" 2448 w = 0:1558 or 15°58 per cent. on cane. The actual quantities of material are then :— Cane =F is as = od py ees 3 TONS, Mixed juice is aA i) a a= FOTO" 6 tons: Bagasse III5:3 X 0:244 ae as a 272°5 tons. Added water 1115-3 X 0:1558 be 28 173°8 tons. Sugar in mixed juice, Io16:6 X 0:1623 sz 165-0 tons. Sugars in bagasse, 272°5 X 0:0369 .. a3 Io-I tons. Sugar in cane .. os Me = a: 175-1 tons. Sugar percent. cane... z Ss ot 15°70 * In this example the last mill juice and residual juice in bagasse are taken as equal. Spencer uses back roll juice, and in Java juice is expressed from the bagasse in a hydraulic press. Alternatively, the solids in the bagasse extract obtained in the sugar determination may be found, using the pycnometer because of the extreme dilution. } This computation assumes that all the fibre finds its way to the bagasse and neglects the small amount which passes through the strainers into the juice. 554 CHAPTER XXVII Sugar in mixed juice x 100 : = ti .- 2 Sugar in cane eh let 94°23 20:9 — 19:0 X 100 | Dilution per cent. mixed juice 70°0 9°09 Dilution per cent. normal juice aaa aoa = 10°00. Added water in mixed juice 1016-6 X 0-0909 = 9g2°-4 tons. Added water in bagasse 173°8 — 92°4 =| 8174 tome Bagasse due to cane 272°5 — 81-4 = IQL*T tomes Normal juice extracted III5°3 — I9QI‘I = 924-2 tons. Normal juice per cent. cane pe Peta = 62-86 III5°3 Or alternatively gI:I5 X (Zi — 00-0909) = 82-86 Case 3.—A number of recently erected houses have installed. apparatus for automatic weighing of the added water. In this case a positive control results, and the weight of bagasse is obtained by the difference between Canes + water — mixed juice. x The weights of material once known, the calculations are made precisely as in case 2. This method is the most rational. Case 4.—The extraction and other results can also be obtained from analy- tical data only, as in the following example :-— Sucrose per cent. cane (by analysis) 12-81 Fibre per cent. cane e II-:00 Sucrose per cent. bagasse - 4°00 Fibre per cent. bagasse 3 44:00 II Bagasse per cent. cane A x 200) ="25+00 On x 4 : 2 Sucrose in bagasse per cent. cane Sag wee Sucrose in juice per cent. cane 12:81 — 1:00 = 11°81 TI - G0 12°81 This method was first used by Icéry.* Inferential methods and the direct determination of sucrose and of fibre in the cane do not now form a part of the usual routine. They have a real value, however, in checking the re- sults obtained from direct weighing, especially when abnormal results appear and when there may be reason to suspect collusion between vendors of cane and weigh-bridge operatives. Extraction = x 100 == 92-49 Case 5.—If the juice of the cane were of uniform composition, the relation, Sugar per cent. cane = sugar per cent. first expressed juice (I — f) where fis the fibre per unit of cane, would hold. Actually the substitution of = f for f gives results close to the truth. This relation is of use for mental and preliminary calculations, and any large departure from it implies an error in weights, analysis or calculation. The ~~ THE CONTROL OF THE FACTORY 555 ratio of sugar in first-expressed juice to sugar in cane should be tabulated as a part of the control records. Interpretation of the Mill Control Analyses.—-In addition to obtaining data to afford a record of the operations, the analyses should be used to maintain the standard of work at its highest efficiency. The criterion usually used to judge the efficiency of the “ crushing ” is the water per cent. in the bagasse. A number of years ago 50 per cent. water in bagasse was considered a standard of good work. With improved milling this figure has been gradually reduced until at the present moment certain Hawaiian mills report crop averages of less than 40 per cent. water. This reduction is largely due to the adoption of drainage grooves in both front and back rollers. Under equal conditions of milling, however, different varieties of cane will behave in a different way. Generally a lower percentage of water will be found with the harder canes, which contain both more fibre and a larger proportion of rind tissue. The water as found by drying to constant weight will also be affected by the constitutional water cr water of hydration in the fibre. Possibly this is less in the more fibrous canes, which contain a higher proportion of rind tissue. The exceptionally low percentages of water reported from the Hawaiian Islands come from those mills operating almost exclusively on Yellow Caledonia cane, which is of the nature referred to. Conversely, the writer has observed that the cane known as Crystalina, White Transparent, etc., tends to afford a bagasse retentive of water. The percentage of water is not altogether a rational basis of comparison, since the water in a given volume of juice will vary with the proportion of dissolved solids. A more rational basis is the value of the expression :— Juice per cent. in bagasse SL en Pn OBE Gn a = = PS, DLL en hi h Fibre per cent. in bagasse X density of juice, CE ere rays ar ea F = : , where fis the fibre and d is the density of the juice. It is usual to make the analysis of the bagasse on the material from the last mill only. A complete control would demand the analysis from the intermediate mills since inferior work here is equally obnoxious. This control is very seldom adopted. ’ An oversight on the efficiency of the added water is very hard to obtain, particularly with systems of compound maceration. The efficiency of the added water will be most when the water mixes completely with the residual juice after dry crushing, and consequently a comparison of the density of the last mill juice with the computed density affords an oversight. A number of years ago it was the custom in Java to report a “ coefficient of admixture of added water,’ which was the value of the expression Sugar per cent. in last mill juice. Sugar per cent. in residual juice. This expression is liable to misinterpretation since a high coefficient must necessarily be found with the use of little water, even if the admixture is zero, and, further, the presence of constitutional or hydration water in the fibre vitiates the value of the result. A third control may be obtained by comparison of the added water per cent. cane and the dilution per cent. normal juice. As the weight of cane is greater than the weight of normal juice at first sight, it appears that the water 556 CHAPTER XXVII per cent. cane would be less than dilution per cent. normal juice. Only part of the added water appears, however, in the mixed juice, and unless the admixture is very low the figure for dilution per cent. normal juice will be less than added water per cent. cane. The Control of the Boiling House.*—The proportion of sucrose which can be obtained from that present in the juice depends on the purities of the original material, of the raw sugar, and of the waste product or molasses. From the comparison of the amount actually obtained with that calcu- lated from the observed purities, a control over the operations in the boiling-house follows. The fundamental formula may be obtained thus: From a material containing 7 sugar per unit weight of dry substance let there be removed c sugar and d non-sugar and let (c + d) contain s sugar per unit weight of dry substance. The residue (molasses) is (I — c — d) and let it contain m sugar per unit weight of dry substance. Then 7= (c + d) s + (zi —c—d)m. This equation can be transposed to the form c-+d = i= Multiplying both sides by — the following equality results — s(c+@) _sG—m “ j (s —m) Now, s (c +d) is the sucrose in the product (raw sugar) and 7 is the SY sucrose in the original material, so that the expression s Acrang is the sucrose obtained in the raw sugar per unit of sucrose in the original material. This quantity is termed the available sucrose, so that s(7 — m) 7 (s — m) where s, 7 and mare the purities of the raw sugar, the original material, and the molasses. If sucrose or pure sugar is the product made, then s becomes unity g—m 7 (l —m) This formula has been deduced above as applied to sucrose and dry substance, that is tosay with regard to absolute purities. In its deduction the only postulate required is that the following self-evident relation holds :— : Dry substance in juice = dry substance in raw sugar + dry substance in molasses. Evidently for dry substance may be substituted gravity solids provided a similar relation holds in this case, and this relation does hold when the gravity solids of the original material, of the raw sugar and the molasses are determined in equal concentrations of non-sugar. s (7 — ™) j(s —m) available sugar, and it gives the quantity of sucrose in raw sugar of purity s, available sucrose per cent. = x 100 and the formula reduces to The value of the expression I00 X is used by the writer as the * Formule for available sugar have been chiefly developed in Java by Winter, Geerligs, Rose, Carp, Lohman and ° Hazewinkel. The form usually employed is that due to Winter : Available sugar = S X 1.4 X + where S and P are the polarization and the polarization gravity purity of the raw juice, and the available sugar is expressed as 96 test and not as sucrose. Algebraically this form is the same as that developed by the writer, who, however, was anticipated in its use by Hulla in the beet sugar industry. A very complete discussion of the work done on control formule in Java will be found in the Dutch Editions of Geerligs’ ‘‘ Cane Sugar and its Manufacture.” The writer has preferred to present the matter here as he himself has developed it. THE CONTROL OF THE FACTORY 557 which must be removed from an original material of purity 7 to afford a residue (molasses) of purity m. In the use of this formula all purities must be referred to one and the same basis, i.e., all must be either absolute, gravity or refractive purities, and, further, the formula is correct only with determinations of sucrose and not with polarizations. As a basis of reference the writer prefers gravity purities, on the grounds of both accuracy and ease of execution. The refractometer is of lower sensibility and there are inherent sources of error in the determination of dry matter, especially in low grade cane-sugar products. The scheme put forward by the writer for determining gravity purities for control purposes is best shown by an example. The syrup or finally purified material before the abstraction of sugar is, for example, analysed at I5 per cent. gravity solids, and is of 85 purity. It therefore contains 2-25 per cent. non-sugar. The raw sugar contains 3 per cent. of non-sugar. A determination of the gravity solids should there- fore be made at a concentration of I00 x oa or 75 percent. As this is at a greater concentration than is possible, the determination is made at a concentration of about 60 per cent. with the known admission of a small error. Similarly, if the molasses is known to be of approximate composition, water 20, sugar 30 per cent., non-sugar 50 per cent., the determination is : : 2°25 made in a concentration of about Ioo x Say or 4°5 per cent. As an actual example of the use of this formula in control the following example may be given. Juice contained 1023-4 tons sucrose, of which 8-4 tons was lost in the press cake, leaving 1015-0 tons in the syrup, which was of gravity purity 85-32. The raw sugar obtained was 950-8 tons, containing 96-32 per cent. sucrose or 915-8 tons sucrose. Determined at a concentration of 60 per cent. the gravity solids in the sugar were 99-73 per cent., whence the gravity purity was 96-58. The gravity solids in the molasses determined in 4 per cent. concentration were 90-43, the sucrose per cent. was 36-44, giving a gravity purity of 40-41. The value of I0o X ae) is then: 100 X See Crete 4044) j (s — m) 85-32 (96-58 — 40-41) That is to say the possible recovery of sucrose as deduced from the actually observed control analyses is 90-53 per cent. of the 1015-0 tons obtained as syrup or 918-9 tons. The actual recovery was 915-8 tons, indicating a loss of 3-1 tons in the operations of boiling, crystallizing and centrifugalling. By the rational use of the s, 7, m, formula as developed above a control over and an examination into the processes in the boiling house can be obtained. A divergence between the computed and observed results may be due to actual losses, to incorrect weighings or to inexact analyses. If such a divergence should arise, it is the duty of the chemist to locate the cause and of the executive to remove it. The sugar lost in the press cake may be regarded as available or not, depending on the point of view of the chemist. The writer prefers to regard it as available and to refer calculations to the sugar in the mixed juice, using, however, for 7 the value determined in the syrup as representing the AO che 558 CHAPTER XXVII finally purified material whence sugar is removed as crystals. As long as the principle of the formula is understood, the basis of reference is a matter of indifference. The general control formula discussed in detail above may be used as a starting point to deduce other formule of use in control. These, which follow from simple algebraic transpositions, are collected below, and from them passage by means of constant multipliers may be made to commercial standards of reference, such as “ gallons of molasses per bag.” Let s denote the purity of the final product : raw sugar, or refined sugar, in which case s = I. Let 7 denote the purity of the initial material :—syrup in a raw sugar house and raw sugar in a refinery. Let m denote the purity of the by-product :—molasses in a raw sugar house and “ barrel syrup ”’ in a refinery. Then :— 1. s (7 — m)/j (s — m) = sucrose in product per I sucrose in initial material. 2. (7 — m)/j (I — m) = product = sucrose in product = solids in product per I sucrose in initial material, when referred to refined sugar as product. 3. m(s —7)/7(s — m) = sucrose in by-product per I sucrose in initial material. 4. m (xi —J)/j (I — m) = sucrose in by-product per I sucrose in initial material, when referred to refined sugar as product. 5. j — m/s — m = solids in product per I solids in initial material. 6. 7 —m/I — m = product = solids in product per I solids in initial material, when referred to refined sugar as product. 7. s —j/s — m = solids in by-product per 1 solids in initial material. 8. 1 —7/I — _m = solids in by-product per I solids in initial material, when referred to refined sugar as product. g. s — 7/7 — _m = solids in by-product per 1 solids in product. Io. I —7/j — m = solids in by-product per I sucrose in product, per 1 solids in product, per 1 product, when referred to refined sugar as product. Iz. m(s —7)/s (7 — m) = sucrose in by-product per I sucrose in product. 12. m (1 —4)/j — m = sucrose in by-product per I sucrose in product, per 1 solids in product, per 1 product when referred to refined sugar as product. Again, if = sucrose in initial material, especially raw sugar, then 13. ~p (7 — m)/j (I — m) = sucrose in product = solids in product = product per I of initial material, referred to refined sugar as sole product. 14. Non-sugar in raw sugar /non-sugar in barrel syrup = barrel syrup per I raw sugar, where refined sugar is the sole product. 15. If s, and sg be purities of the product, then sucrose in raw sugar of s, purity Paes (So — m) apes Mare pes sucrose in raw sugar of sy purity = Sq (Sy — ™) Sy (I — m) i.e., with reference to pure sugar. These formula may be used to solve many problems, some examples being appended. 1. What are the comparative weights of raw sugar of composition (a) 96:0 per cent. sucrose, 96:3 gravity purity, and (b) 97-0 per cent. sucrose, —— ore THE CONTROL OF THE FACTORY 559 97:2 gravity purity, which can be obtained from a juice of 80 gravity purity with molasses of 40 gravity purity ? From formula 11 the relative quantities of sucrose in the sugars are sucrose at 96:3 sd 96°3 (97°2 —40) bagesessr2 sucrose at 97°2 97°2(96°3—40) and the relative weights of the products are as 1-0066 xX 7 . I, or as T-OI7I: 1. 96 2. What weight of molasses of 40 gravity purity and 96 gravity solids will be obtained from roo tons of juice of 18° Brix and 84 purity, from which sugar of 97 gravity purity is extracted ? 97 — 84 _, Ioo $< xX — 97 —40 96 3. 1000 lbs. of low grade sugar of composition sucrose go per cent., absolute purity 92, are to be melted and produced as 96 test sugar of 96-3 per cent. sucrose and 97-3 purity. What quantity will result ? It is necessary to assume a purity for the waste molasses; let this be 45 absolute. Then from formula 1 the percentage recovery of sucrose will 97°3 (92 — 45) 92-0 (97°3 — 45) BO 52/3) ye BOO s gag Tbs. £00." E00... :90«3 An additional control over the operations in the boiling house may be obtained by constructing dry substance balances, based on absolute solids, gravity solids or refractive solids. From the difference between the solids balance and the sucrose balance, a non-sugar balance is obtained, in which, however, will appear all the experimental errors. In the application of such balances to control, the following points are to be borne in mind. Mechanical loss of material before the removal of sugar from solution will result in an equal proportionate loss of sugar and non-sugar, but after sugar has been removed any loss gives a disproportionate loss of non-sugar. A means is thereby afforded of locating the position of mechanical loss. On the other hand, any sugar lost by inversion or caramelization goes to swell the amount of non-sugars, so that an exact balance in the non-sugars may result from a compensation of errors. From formula 7 the answer is 18 x == 2-28 tons. be 100 X = 95-0, and the weight of commercial sugar will be r000 X The Basis of Reference for Purities—The system of control described above and the various formule are equally correct whether the solids used in the purity calculations are absolute, gravity or refractive (cf. Chapter XXV), provided that in the last two cases the determinations are made in equal concentrations of non-sugar. The writer’s opinion is that gravity purities form the most convenient basis since the specific gravity can be determined with ease and with far greater accuracy than can either the dry substance or the refractive index. Whatever basis is selected must be used throughout, as the control is vitiated if the bases are mixed, as, for instance, determining gravity purities in the juices, absolute purities in the sugar, and refractive purities in the molasses. Control of the Sugar Boiling.—In the more recently adopted methods of sugar boiling the procedure is based on making the strikes at certain 560 CHAPTER XXVII predetermined purities. This is effected by regulation of the quantity of syrup and molasses introduced into the pan. The relative proportions depend on the purity of the materials. Systematic determinations of these purities must then be made. In this way the superintendent is able to instruct the pan operator how many “ feet” of syrup and of molasses is to be used in each strike. The methods of calculation to be used are those explained in Chapter XIX. The relations between contents of pans and contents of storage tanks should be worked and tabulated. The pan operator should also keep systematically a record of the work done on loose-leaf forms, which are filed daily in the laboratory. Besides the routine determinations of Brix, Polarization and Purity, examination of the condition of the crystals is at times useful. The recovery of the separated crystals in the centrifugals is not complete, and with careless operation an excessive loss may result. The determination is most readily made by filtering the massecuite through glass wool and comparing the analysis of the crystal-free filtrate with that afforded by the factory centri- fugals. A similar analysis may be made on the molasses flowing from the centrifugals. This control is of the nature of a special investigation, as the systematic routine determinations of purity afford in general a sufficient check. Entrainment Losses.—By this term is meant especially the losses which occur by sugar being carried over mechanically, especially in the last body of the evaporator and also in the pans. Automatic continuous samples of the discharge water can be obtained by adopting the devices described for juices. After obtaining the quantity of sugar, if any, in the water, the volume of the latter is required in order to compute the sugar losses. Per lb. of steam condensed the quantity of water w required is given by = tg — ty t, and ¢, are the initial and final temperatures of the cooling water. The exact quantity of steam generated in the last body of multiple apparatus is not known unless definite experiments are made to determine the expression w = 3? where h is the total heat of the steam and : ; I , it. It is of sufficient exactitude to take this as oe of the total evaporation where # is the number of bodies. Inversion Losses.—In a well-conducted factory inversion losses should not be detectable. Even if white sugars boiled from a juice with an acid reaction be made, careful control may reduce these to a very small quantity. The method which suggests itself for their estimation is a reducing sugar balance, any increase in this material being due to inversion of cane sugar. However, if the juices havean alkaline reaction, isomeric change of the original reducing sugars to others with a lower reduction factor occurs, and if the alkalinity be pronounced actual destruction occurs. The reducing sugar balance has then a very limited application. Number of Analyses Necessary.—The number of analyses necessary for a complete control is a matter for the judgment of the individual chemist. Much unnecessary labour may be saved by judicious sampling and composit- ing. Distinction should also be made between those analyses required as a THE CONTROL OF THE FACTORY 561 guide to direct the operations and those on which the statement of yield and losses is made. For the latter to have their full value sucrose and not polariz- ation should be returned and all statements should be based on the former.* The writer regards the following scheme as sufficiently detailed. First Expressed and Last Mill Juice—Brix, polarization, in six-hourly composite sample. Mixed Juice——Brix, sucrose, reducing sugars in 24-hourly composite sample. Syrup.—Brix, polarization every three hours. Gravity purity in 24- hourly composite sample. Bagasse._-Water, polarization, every hour. Massecuites and Molasses in Process.—Brix, polarization, purity, each strike. Waste Molasses—Brix, polarization, purity from each container. Peri- odical detailed analyses including gravity solids in appropriate dilution, sucrose, gravity purity, reducing sugars and ash, in composite sample. Sugar.—Polarization, water per cent., every two hours. Periodical detailed analysis as for waste molasses. Press Cake.—Polarization every six hours on composite sample. Condensed Water.—Polarization in composite 24-hour sample. Records.—In the technical accounting of a sugar-house, distinction should be drawn between the “‘ weighted average ’’ and the simple average. The former is used when the weights of the material are known and when a balance is required. The latter used when the weights of the material in question are not recorded, and where a great degree of exactitude is not demanded. The “ weighted average’ is determined periodically by a reversed operation after the total of the materials over a period has been found as the sum of the daily quantities. An example will make the method to be used clear. Over a period of seven days the daily quantities of mixed juice, of sugar therein and sugar per cent. were :— Mixed juice .. 563-4 1180-2 1263-4 1187-2 1251 °4 923°5 II51-2 .. Total 7520°3 Sugar in juice Bios) -£O0sOmcE 70cOl. £67 2A5 E7720 TAGE ES Gee ons. 1080 +2 Sugar percent. 15°42 14°40 13°93 I4°IO 14°21 16°15 13°80 . I080°2 The weighted average sugar per cent. 1s 8 ge sugar p 7520-3 The simple average of the daily determinations is 14°58. If, for example, in the ten previous weeks there had been recorded 801921 tons of mixed juice and 11170-5 tons sugar therein, the totals to date will be 87712-4 and 11250-7 respectively, giving the to-date figure for I1250°7 87712°4 The quantities which should be worked out as actual weights daily and = 14°39 per cent. sugar per cent. as == 12°83 per cent. * The very great majority of cane factories in Cuba, Java and Hawaii base their results on polarization as opposed to sucrose percent. In Mauritius, on the other hand, for the crop of 1918, eighteen houses, out of thirty- three reporting, used the more rational basis. 2P 562 CHAPTER: XXVIII carried forward as totals periodically so that they may be reduced to correct period and to-date averages are :— Cane.—Weight of, sugar in, fibre in. Bagasse.—Weight of, sugar in, fibre in, water in. Mixed Juice.—Weight of, gravity solids in, sugar in, polarization in. Added Water.—Weight of. Syrup.—Gravity purity of. Press Cake.—Weight of, sugar in. Sugar.—Weight of, gravity solids in, polarization in, sugar in. Molasses.—Weight of, gravity solids in, polarization in, sugar in. It will be sufficient to determine the gravity solids and sugar in the sugar and molasses in a sample composited over the period. Simple averages of the observations relating. to first and last mill juice, density of syrup, purities of massecuites and process molasses, are of sufficient exactitude for obtaining the average results of a period. The to-date average may be obtained most readily by cross multiplication :— Previous to date average, seven periods, 49:0; current period average TAO eo She 8 51:2; average to date: = 49°3. Stock-takings and Balances.—Periodically* a stock and balance sheet of the quantities of material worked up, of the produce made, and of stock in process should be made. The time required to do this depends on the sys- tematic keeping of the daily records, combined with a knowledge of the capacities of the various tanks. The stock can be taken with only a few minutes’ delay of the mills, provided the foremen at the various stations are instructed in their duties, and are supplied with forms on which they enter up the material on hand when the mill is stopped. In stopping the mill all that is necessary is to leave a space on the carrier between two separate car loads and to stop the carrier when the cane corresponding to the end of the period has passed the crusher. The resulting juice is allowed to reach the measuring tanks, after which the mills are again put into operation. After obtaining the measurements of juice, syrup, etc., the estimate of sugar obtainable is made from previous experience combined with the already made routine analyses, supplemented if necessary by special analyses of stock. In estimating the product obtainable from the pans it is well to instruct the operators in advance to record the “ feet ’’ of syrup and molasses already taken into the pan at the time stock is taken. In measuring the material in crystallizers and mixers, it is only necessary to observe the “ outage ”’ measured from the top of the container. The corresponding contents in cubic feet can then be obtained at once from tabulated records. In houses which work at prearranged purities in the massecuites, passage can at once be made by a constant factor from cubic feet to bags of sugar and gallons of molasses or to any other desired system. * In Hawaii it is customary to take stock and balance weekly. In Java a ten-day period, and in Cuba a fort- nightly one is general. = —|.. THE CONTROL OF THE FACTORY 563 A typical stock-taking, in which the estimated quantities are calculated from the s 7 m available sugar formula, follows :— ESTIMATED YIELD. Sugar Molasses. bags of (QUES = @umeet. Brix. Polarization. 325 lbs. gallons). Raw Juice 565 af 453 18-0 I5°5 Io 64 Defecated Juice .. Spy lig Heke) 18 -6 16-2 35 220 Scums 3 i ieee 220 13 °3 I1-o 3 20 Evaporators o Sey fe ie — — 40 225 Syrup te a a O2Z0 62-0 54 °6 129 825 Vacuum pans (Syrup) <4) E550 = — 322 2,062 Vacuum pans (Molasses) 310 — = 21 1,756 Massecuite at 75 purity .. 945 = = 138 3,193 Massecuite at 55 purity... 8,340 -- -- 890 39,919 Molasses at 45 purity .. 220 -= — 14 Te 27E Total in process = aoe fet OO2: 49,545 Total shipped and steted tone ntelsigeneg: 511,918 Total to date .. ae ao) sirius 561,563 Total previously se out OT, 702 403,710 Total for period BS Sian a OG ee 157,853 REFERENCES IN CHAPTER XXVII. Chemical Engineer, 1908, 9, 4 “Handbook for Cane Sugar Manufacturers.” Int. Sug. Jour., 1913, 15, 141. Jour. Ind. Eng. Chem., 1913, 5,.315- Int. Sug. Jour., 1915, 17, 432. WIS'G;,, 1869) -1,: 27: An wy H CHAPTER: XXVIII FERMENTATION WITH SPECIAL REFERENCE TO THE SUGAR HOUSE Tuis chapter treats principally of the fermentation of molasses and of the manufacture of rum ; incidentally, opportunity is taken to bring together some part of the scattered articles dealing with the mycology of the sugar house. Yeast.—By this term is loosely meant any organism which has the property of fermenting sugars and producing mainly alcohol and carbon dioxide ; in this sense organisms such as the Torule, Monilia, and certain of the Mucoracee would be included, although these organisms are very distinct from that mainly composing “ brewers’ yeast,’ which consists essentially of Saccharomyces cerevisi@. Systematically, production of alcohol is not an essential character of the Saccharomyces although the greater number of species here included do produce alcohol ; in addition some species ferment saccharose, glucose, fructose and maltose; others glucose, fructose and maltose only ; others lactose only. A complete list of all the known “ yeasts” is given by Kohl; following him they are divided into these groups :— I. Yeasts proper or budding yeasts. Saccharomycetes. These are divided into the following genera :—-1. Saccharomyces; 2. Hansenia ; 3. Torulaspora; 4. Zygosaccharomyces; 5. Saccharomycodes; 6. Sac- charomycopsis; 7. Pichia; 8. Willa. II. Fission Yeasts, Schizosaccharomycetes. This includes one genus, Schizosaccharomyces. III. Yeast-like fungi. These are divided into the following genera :-— 1. Torula; 2. Mycoderma; 3. Monilia; 4. Chalara; 5. Oidium; 6. Dema- tium; 7. Sachsia; 8. Endomyces; 9. Monospora; 10. Nematospora. In rather a loose way yeast as it appears in breweries and distilleries is classed as ‘‘ top”’ yeast or “‘ bottom” yeast, or otherwise as “ high ’’ and “low” yeast. These terms refer to the behaviour during fermentation, some races rising to the surface and others falling down as a sediment. The difference is not specific, since a top race can be cultivated from a bottom type, and vice versa. In breweries and distilleries generally, the production of alcohol is due to the species Saccharomyces cerevisi@, of which a number of varieties or races are known. Went and Geerligs? in Java examined the budding yeast there in arrack distilleries, and describedit as a newspecies, S. vordermanit, although 564 FERMENTATION 565 what differences distinguish it from the typical S. cervisi@ are very small and by some systematists would not be considered specific. Peck and Deerr® collected yeast from distilleries in Demerara, Trinidad, Cuba, Mauri- tius, Java, Natal, and Peru. All of these except that from Peru were typical budding yeasts, between which they could find no difference sufficient to form a distinction. The Peruvian yeast was a fission yeast. In 1893, Greg? isolated from Jamaican distilleries a fission yeast, to which he gave the name Schizosaccharomyces mellacet, and in the following year Eijkmann} found a fission yeast Sch. vordermanit in Java distilleries. Material received by Peck and Deerr from a Peruvian distillery also proved to be a fission yeast, the samples sent therefrom containing no budding forms. All of these fission yeasts are very similar, if not identical with the original fission yeast, Sch. Pombe, obtained by Lindner® from Kaffir millet beer. In Plates XXIX and XXX are shown the yeasts examined by Peck and Deerr, distinguished as to country of origin by the initial letter, two forms from Natal being shown. In Plate XXIX the specimens are drawn from material obtained from fermenting beer-wort 36 hours old. The sporulating yeasts in Plate XXX were obtained from gypsum blocks, except the Peruvian type, which is from an old beer-wort agar culture. The yeast marked NT is a non-sporing yeast from Natal, referred to else- where in this chapter. Of other yeasts the most important are those to which the fermentation of grape musts is due, and usually referred to as S. ellipsoideus. A conjugating yeast, Zygosaccharomyces, was first observed in the fermentation of apple juice by Barker? in England. Yeasts of the type S. mali duclauxt, which do not invert cane sugar, have been pro- posed for use in analysis by Pellet and Perrault®; on the economic scale the use of such ferments has been patented by McGlashan,® with the object of removing the glucose in order to obtain a greater yield of sugar on crystallization. Previously, however, Gayon,!® in 1882, had suggested the use of the pin mould, Mucor circinellioides, for the same purpose. Other Organisms of Special Interest. Woulds—The two orders, Peri- sporiacee and Mucoracee, are frequent inhabitants of distilleries. The first order includes the genera Aspergillus and Penicillium, which have been specially studied in connection with grain distilleries, where an unpleasant taste is often ascribed to their presence. Aspergillus oryz@ is of interest as the organism to which the saccharification of rice is due in the preparation of the Japanese spirit, saki. The Mucoracee are also an important family unfavourably known in the distillery. Some can produce small quantities of alcohol. Mucor oryze, which is perhaps the same as Rhizopus oryz@ was isolated by Went and Geerligs? from vaggt or Java yeast. Mucor rouxtt isolated from “‘ Chinese’’ yeast has at one time enjoyed some notor- iety as an alcohol producer. Lactic Acid Fermentation.—The importance of the bacteria which produce lactic acid in green malt in cereal distilleries is shown in a subsequent section ; they occur chiefly in sour milk and in green malt; through their agency the production of lactic acid from beer wort has been proposed, and its pro- duction from molasses does not seem prima facie impossible ; certain species have been noted as causing disease in beer. Acetic Acid Fermentation.—This fermentation is economically of import- ance in the production of vinegar from alcohol ; it may take place under the 566 CHAPTER XXVIII influence of certain well-defined bacteria or under that of an imperfect fungus, referred to as Mycoderma vini; generally it is essentially a process of oxidation, but Watts and Tempany have shown that the spontaneous souring of cane juice proceeds anerobically, the sugar forming the source of oxygen. Acetic acid has been observed by Greig Smith" in soured sugar, and sugar or juices left in crevices about a sugar factory undergo this fer- mentation and are responsible for the sour smell often observed ; wash kept after the alcoholic fermentation is complete also undergoes acetic fermenta- tion, and the writer has knowledge of cases where consignments of “ molas- cuit ’’ completely underwent this fermentation in transit between Demerara and London. Butyric Acid Fermentation.—This fermentation is technically of import- ance in the rum industry as the flavour of fine rum is by some authorities believed to be intimately connected with its presence ; in cereal distilleries it is considered most harmful, as not only does it decrease the yield of alcohol, but also forms objectionable products as butyric acid and butyl alcohol. Viscous Fermentation.—This term has now only an ill-defined meaning, but occurs frequently in older writings on fermentation ; it is used in refer- ence to fermenting liquids becoming ropy or slimy, and was once not an uncommon phenomenon. In European distilleries this disease has been associated with certain well-defined bacterial species; in rum distilleries it is not unknown, and may often be traced to lack of cleanliness and to attempting to work with too little or no bactericide. Gumming.—The “ gumming”’ of cane juices has been studied by Greig Smith! who found that this was due to a bacillus which he described, and named Bacillus levaniformans ; this organism is also one of several respon- sible for the deterioration of sugars. Lewton Brain and Deerr?* isolated from Hawaiian sugars several forms which also produced large quantities of gum. Formerly this fermentation would have been classed as a “ viscous fer- mentation.” Leuconostoc mesenteroides.—This organism, known as “ frog spawn,” has the faculty of converting sugar solutions into a gelatinous, viscous mass. It is a well-known type and has been reported from Europe and Java where it has been the cause of blocking up pipes used for the convey- ance of juices. It a’so occurs in Hawaii and Cuba. An alkaline reaction favours its development, and theyefore “ liming ’’ does not prevent, but aids, its growth. In recent literature this organism is classed as a Streptococcus. Spontaneous Fermentation of Cane Juice—Watts and Tempany* found that yeasts and an undetermined bacterium were concerned in this process. Alcohol was produced by the yeast, and acids by the bacterium, of which about one-third were volatile acids. The fermentation was both aerobic and anaerobic, and was inhibited by the presence of phenol, indicating that already formed enzymes do not play a very prominent part in the souring of juices. Spontaneous Combustion of Molasses——Crawley! has recorded a case of molasses on storage becoming charred, the damage being supposed to have been initially due to micro-organisms ; consignments of. ‘‘ molascuit ” have suffered a similar change on board ship. Nitric Fermentation of Molasses.—In beet sugar factories the after- massecuites on storing sometimes show a nitric fermentation. A dense ‘ FERMENTATION 567 red cloud of vapour due to the presence of nitrogen dioxide is observed to hang over the massecuites; this is ascribed to decomposition of the potassium nitrate present under the influence of bacteria, but really very little is known on the subject. The writer is unaware of any similar phe- nomenon being observed in cane sugar factories. Foaming Fermentation of Massecuites—Low grade massecuites and molasses frequently exhibit the phenomenon of suddenly producing large volumes of gases giving rise to foaming and frothing. In the cane sugar industry the matter was first studied by Geerligs!® who believed the cause was the spontaneous decomposition of the glucinates or bodies formed by the action of lime on reducing sugars. A similar condition happens not infrequently in the beet houses, where reducing sugars are mostly absent, and Lafar!’ believes the cause in this case is that due to yeasts acting on the amides present. He also accepts the possibility of purely chemical causes such as the interaction of amides, water and reducing sugars. That organic action is possible inso higha concentration follows from the isolation by Ashby?8 (Jamaica) of a yeast active in molasses of 80° Brix, and also by von Richten!® of a conjugating yeast from honey. Two types of bacteria have also been obtained by Gillet?° from foaming beet massecuites, one of which was thermophilous and active at 70° C. A third cause is proposed by Kraisy”4, who suggests that dissolved carbon dioxide is responsible, and that the gas is released only when the supersaturation of the mother liquor disappears. Possibly all three causes contribute, since they are not incompatible as between each other. Molasses as a Source of Alcohol.—Fermentation proceeds according to the equation : C,H,.0, = 2C,H;OH + 2C0O, Glucose Alcohol Carbon dioxide. Following on this equation rb. of glucose or 0-95lb. of cane sugar should pro- duce 0-5111b. of alcohol and 0-48qlb. carbon dioxide. This yield is never obtained in practice even when the distillation losses are disregarded. _ Peck and Deerr® fermented in pure culture a number of molasses with tropical yeasts, and found that on an average go per cent. of the fermentable sugars were recovered in alcohol, the amount as indicated from the above equation being put equal to 100. In addition, in Hawaiian molasses they found from 4:05 per cent. to 7:32 per cent. of the sugars were unfermentable. Previously Pellet and Meunier”? had observed in Egyptian molasses 2-40 per cent. of “‘ glutose,”” and Deerr?’ had found up to 3 per cent. in Demerara molasses. The total amount of sugars in cane molasses varies from 45 per cent. to 65 per cent., so that it is impossible in the absence of an analysis to state what quantity of alcohol can be obtained from a molasses. In the very best practice employing pure specially selected yeasts as much as go per cent. of the theoretical yield mdy be obtained, falling to 70 per cent. with the indifferent methods usually found. Referred to volume measure- ments and to a molasses containing 55 per cent. of sugars, superior, good and indifferent operation is represented by 2, 2:5, and 3 gallons of molasses per gallon of 95 per cent. alcohol. Manufacture of Rum.—The manufacture of rum as a product of the fermentation of cane juice or of molasses forms an important part of the cane sugar industry in Demerara, Trinidad, Jamaica, Cuba, the Leeward 568 CHAPTER XXVIII Islands, the French West Indies, Hayti, and the Argentine. Rum is also manufactured in connection with sugar mills in Peru, Mauritius, Queensland, and Natal. Molasses forms the source of the spirit “ arrack”’ in Java, and is also utilized in British India; in these two localities, however, the manufacture of spirit is divorced from the sugar industry proper. The writer has been unable to obtain statistics of the annual production of rum, but believes the total production cannot be less than 20,000,000 gallons of spirit containing 75 per cent. of alcohol. The fermentation processes under which rum is eventually produced are very complex, and differ largely from locality to locality. Probably the most general agents are the budding yeasts which have been described earlier in this chapter. To these is almost entirely due the rum made by the quick fermentation process, as followed in British Guiana for example, where the fermentation from start to finish only lasts forty-eight hours. The second most important agents are the fission yeasts, which do not seem to be of such general occurrence as the budding type. Thirdly, there is the influence of the non-sporing yeasts, torule, etc.; and finally there is the part played by bacteria, especially of the butyric-acid forming type, which appear principally in the slow fermentation processes in use in Jamaica, where the fermentation lasts as long as two weeks. Outlines of the processes used in different localities follow. Demerara.—A process of adventitious fermentation obtains; com- mercially exhausted molasses forms the initial product ; the molasses are received directly from the centrifugals, storage for a few days’ supply only being provided. The molasses and water—generally trench water—are usually mixed to the required density in a mechanical mixer in the basement and pumped up to the vats in the fermenting loft ; in other cases the mol- asses is pumped up to the vat and mixed by hand with the requisite amount of water. The density of the mixture varies from 1-060 to 1-063. To the wash is added sulphuric acid, and sulphate of ammonia in the proportions of r gallon and to lbs. per Iooo gallons ; the acid is added to prevent the growth of bacteria, especially the ‘‘ butyric acid’ form. Fermentation sets in rapidly, and is generally complete in 48 hours ; the density of the fermented wash varies from I-o15 to I-025, and is governed by the amount of sugar present, and by the action of the yeast. In some distilleries, ammonium bifluoride is used as a bactericide in place of sulphuric acid. Bird, in Demerara, has quite recently shown that better results are obtained by transferring yeast from an actively fermenting vat to one just set up. .As a means of doing this he places a cask within the vat, the contents of the former serving to “ pitch”’ the next lot of wash in that vat. Mauritius.—In this district only one sugar factory possesses or did possess (Ig01) a distilleryas an annexe. The process there followed is as under:—A barrel of about.50 gallons capacity is partly filled with molasses and water of density 1-10 and allowed to ferment spontaneously ; sometimes a handful of oats or rice is placed in this as a preliminary to fermentation. When attenuation is nearly complete, more molasses is added until the contents of the cask are again of density 1-10, then again allowed to ferment. This process is repeated a third time ; the contents of the barrel are then distri- FERMENTATION 569 buted between three or four tanks, holding each about 500 gallons of wash of density I-10, and, 12 hours after fermentation has started here, one of these is used to “‘ pitch” a tank of about 8,000 gallons capacity. A few gallons are left in the pitching tanks which are again filled up with wash of density 1-1, and the process repeated until the attenuations fall off, when a fresh start is made. This process is very similar to what obtains in grain distilleries, save that the initial fermentation is adventitious. Java.*4—In Java and the East generally, a very different procedure is followed. In the first place a material known as Java or Chinese yeast is pre- pared from native formule. In Java, pieces of sugar cane are crushed along with certain aromatic herbs, amongst which galanga and garlic are always present, and the resulting extract made into a paste with rice meal ; the paste is formed into strips, allowed to dry in the sun, and then macerated with water and lemon juice. The pulpy mass obtained after standing for three days is separated from the water and made into small balls, rolled in rice straw and allowed to dry, these balls being known as vaggi or Java yeast. In the next step rice is boiled and spread out in a layer on plantain leaves and sprinkled over with vaggi, then packed in earthenware pots and left to stand for two days, at the end of which period the rice is converted into a semi-liquid mass. This material is termed fapej, and is used to incite fermentation in molasses wash. The wash is set up at a density of 25° Brix, and afterwards the process is as usual. In this proceeding the starch in the rice is converted by means of certain micro-organisms, Chlamydomucor oryz@, into sugar, and then forms a suitable habitat for the reproduction of yeasts, which are probably present in the vaggi, but may find their way into the tapej from other sources. About 1I00 lbs. of rice are used to pitch 1,000 gallons of wash. Jamaica.—Allan*> gives the following outline of the process followed in making flavoured spirit :—‘‘ The wash is set up from skimmings, dunder, molasses, acid and flavour. Acid is made by fermenting rum cane juice which has been warmed in the coppers. To this juice is added dunder and perhaps a littleskimmings. When fermentation is about over, the fermenting liquor is pumped on to cane trash in cisterns and here it gets sour. Into these cisterns sludge settling from the fermented wash is from time to time put. This acid when fit for use smells like sour beer. Flavour is prepared by running fermented rum cane juice into cisterns outside the fermenting house, along with cane trash and dunder that has been stored from a previous crop. Generally a proportion of liquid from what is called the ‘ muck hole’ is also added to this cistern. The components of the ‘muck hole’ are the thicker portion of the dunder from the still, the lees from the retorts, and cane trash and other adventitious matter which from time to time finds its way into this receptacle. From this cistern the incipient flavouring material passes on to a second and third cistern filled with cane trash, and to which sludge from fermenting wash has been added. From the third cistern it is added to the wash. Skimmings are run from the boiling house into cisterns half filled with cane trash. This is allowed to remain four, five, or six days. When the skimmings are considered ripe, wash is set up with them. Fermentation lasts seven to eight days. The time which elapses between setting up the wash and distillation is from thirteen to fourteen days.” 570 CHAPTER XXVIII Process used in Grain Distilleries**—It is of interest to compare the above methods with those in use in cereal distilleries. The basis of manu- facture is grain; this is ground to a coarse powder and a weighed amount is placed in a digester, mixed with water, and heated by steam under a pressure of two or three atmospheres for an hour or more. The liquid contents of the digester are then blown into a second vessel and cooled. As soon as the temperature falls below 63° C., a proportion of malt is added ; the malt contains a ferment, diastase, which converts the starch in the grain to a sugar, maltose. After the starch has been so converted into maltose, the contents of the vat are drawn off into a fermenting vat. and rapidly cooled. These vats are usually large enough to hold a whole day’s work, and a dis- tillery will have generally six fermenting vats, each of which may be of as great a capacity as 50,000 gallons. After the vat is set up it is “ pitched” with yeast, and the temperature and quantity of yeast regulated with the object of obtaining the maximum yield of alcohol within the legal limit of time, 7.e.,72 hours. The temperature is regulated by means of water circula- tion through coils and maintained at 20°-25° C.; the high temperature promotes a rapid fermentation, but more fusel oils are formed than at a ~ low one. The preparation of the pitching yeast is as under :—A mixture of green malt and water is warmed to about 70° C., kept at this temperature for about two hours to allow the starch to be converted to maltose and soured. Green malt contains enormous numbers of bacteria, amongst which are the lactic and butyric acid organisms. Butyric acid isa virulent yeast poison, and its devel- opment would injure the yeast. Yet these organisms cannot be killed by raising the temperature, as this would also destroy the action of the diastase. The butyric acid bacteria are, however, themselves susceptible to slight degrees of acidity. In order to destroy them without injuring the yeast the temperature is arranged so that the lactic acid bacteria can develop; the optimum temperature of the lactic acid bacteria is from 47 to 50° C., that of the butyric acid organisms about 40° C. The mash is hence kept at-a temperature of about 50° C., whereby the lactic acid bacteria thrive and the formation of lactic acid effectually prevents the development of the butyric acid organisms. When the acid present reaches 1-0 to I-I per cent., the process is stopped by raising the temperature to 70° C.; the mash is re- cooled to 20° C. and pitched with yeast, in the proportion of about rb. to Io gallons ; after about 14-16 hours the yeast has so far developed as to be used in the main process, a portion being kept for the next sour mash. This process left much to chance, and has been developed on other lines, although the object in view has always been the same. In the first place the presence of lactic acid bacteria is adventitious, and, although their presence is very general, it not infrequently happened that the process miscarried by reason of their absence. To get over this difficulty the infection of the sour mash was carried out by inoculation with pure cultures of lactic acid bac- teria, and now more recently a new procedure known as the hydrofluoric acid process has been largely introduced. It was sought for a long time to find some substance that would be anti- septic to the butyric acid bacteria and yet harmless to the development of yeast, and after many bodies had been tried Effront, in 1890, introduced the use of alkaline fluorides. The initial proposition was to add from 4 to 8 grms. of hydrofluoric acid per hectolitre (say from ,, to jj, Ib. per 100 gallons) of the FERMENTATION 571 yeast mash which had been treated in the way described above, this quantity being found sufficient to prevent the development of injurious organisms. ~ Pure Yeast Processes—In the processes described above the fermentation takes place under the influence of such yeast moulds and bacteria as adven- titiously find their way into the wash. Bya pure yeast process, is meant one in which the fermentation is conducted under aseptic conditions, and under the influence of one selected yeast. Such a process in its entirety demands the sterilization of the raw material, and the continued cultivation in special apparatus, designed to prevent contamination of the selected yeast. The sterilization of the wash is not absolutely essential to the process, as sufficient of the pure yeast may be added to ensure that the fermentation takes place mainly through it. Pure yeast processes are in very limited use in the cane sugar industry, and the only plants of which the writer has knowledge are ° in the state of Morelos, in Mexico. The process here followed as described by Fournier** includes a Magné apparatus for the aseptic continuous pro- duction of selected yeast, two intermediate vats of 25,000 litres capacity each, the contents of which are “ pitched ”’ with the pure yeast, and which in turn serve to supply yeast to the main fermentation vats of which there are forty-five of capacity 17,000 litres each. In such a process by means of selection, yeasts capable of completely fermenting wash at a density of 1-1 can be used and yields 95 per cent. of the maximum possible can be obtained. Rum.—Rum has been legally defined in Great Britain as a spirit distilled from fermented products of the sugar cane in a country where the sugar cane is grown. This definition is quite inapplicable to the United States, where rum has been manufactured in New England from molasses since the old colonial days. It is also almost self-evident that the location of manufacture need have nothing to do with the composition and flavour of the product. Originally the term rum was confined to a spirit distilled from juice, the term tafia being used for spirits of molasses origin. The term in the French West Indies is guildive, a corruption of “ kill devil.’ Rum consists mainly of alcohol and water, the other bodies present being caramel (in coloured rums), fatty acids, ethereal salts, aldehydes, higher alcohols and essential oils. The acids known to be present are formic, acetic, butyric and capric, both free and as ethereal salts. Miller®’ has given the following analyses of Demerara rums :— ANALYSES OF DEMERARA COLOURED RUMS. PERCENTAGE BY VOLUME. j | | | | | | (RS bs rs ieee sit fae, 6 7 8 9 Alcohol = é Zs .- 80.84 (80.40 179.19 |77.39 |76.68 |80.56 \77.32 |80.98 80.19 Higher alcohols, “‘fusel oil” .., 0.8956) 0.7975 | 0.4557 | 0.5903 0.6942 | 0.6463 | 0.3218 0.9243 | 0.1581 Ethylic formate .. os -- 0.0088 | 0.0153 | 0.0405 | 0.0373 | 0.0233 | 0.0396 | 0.0180 0.0373 0.0350 Ethylic acetate .. Zara 30°2 14°3 15 °2 I2°5 6-1 65°7 31 °8 33:2 30 °8 24°5 Sik 24-35), “D500 I2°9 6°5 66 -6 32 °3 33 °6 31 °2 24°9 ee be E 5 ~2; || POE | 134 PO OPES 23267 op Paces | oe Ee eae aoe} 15,6) TGts | 13-8 TA G84 SReE | 34254 = 32°38 1 25e9 Ba s05| LOE bh 1G9 | lr a3 725 W- OG23) fh 935-6.) $3580" | 63256452663 B26 | 16*5 |. 17%4 | 14°7 | 84 || “7o*z | 34-0 | 35%4 | 3371 | 26-8 Sep op eROOn | 17286 EG ei BB EE) 34:4] 35:9 3355 | 2733 Boece 4 | LSB 1536) Oraeh ZrO") 34°90.) (36°3-| 34°04) 2727 Sasa te La e7- TQ e O57 I 74-8]. 35°35 | 3658). 34-5) 28-2 38 -2 18-2 19:2 16 -6 10 ‘2 TiaCgf ie MiGs Ss 37°3 34-9; 286 SA ES 27') MO 6 1 2750 | TO-7 1) 746") 36 °2 | 3757 |. 354-) 20-8 40-0 Ig°I 20°1 I7°5 bp ea 75°5 36°7 38"2 35°8 29 -6 49°9 | 19°6 | 20°5 17°9 IT -6 FOsA | 93 7eT 38-6 | 36°73 30-0 41 °7 20°0 21-0 18-4 I2°0 77 °3 37°5 390°! 36-8 30°5 42 6] 20°4 21-4 18-8 I2 5 78 +2 38-0 39°5 37 °2 31-0 FS oe eo Wet Oo} LOS) Eee 7 OsE | 384 | 400 [a sz en) eZ kaa Oo KW he Qo 614 Munson AND WALKER’S TABLE—(coniinued). . fan Invert sugar Fy Invert suga’ 5 i and sucrose. a g ej and sucrose = = 2 cI is = = 2 g 3 2. = g Bi. Bie & a g ae Se a + bo a Bs bo ° = fo) a mgs mgs. mgs. mgs mgs mgs. mgs mgs mgs mgs. 79°9| 38:9) 40°4 | 38°2 | 3ro-115.°5 |||; 56-8 |. 58:9 | 50nO0 maaan 80-8 | 39°3 | 49°9] 38°6 | 32°74 | 116-41 57:2] 59°4| 57°74] 5r-2 81-7 | 39-8). <40*4 | 39-1} ~ 32-8 117-3] 5727 | ¢ 5978.) 57S ciesatee S2-On lesz 41 °8 39:6 33°3 || 118-1 58-1 60 °3 58 +3 52-1 83°55 40-6 42 °3 40 +O 33 °8 || IIg-0 58-6 60 -8 58-8 52-6 84°4 | 40 *t-])42°7 | -40°5:| 34°21 Ir9"9 | “59-0 | “61-2 '|. 59 |) LCOS I13°I | 107 o 113-6 | 107 5 I14‘I | 108 ¢ 1146 | tot « 616 MuNSON AND WALKER’S TABLE—(continued). Invert sugar and sucrose. 3 2 3 ui 5 a altar i - fe} mgs. mgs. mgs. mgs. 222>Tae| eh 2 AO ne On Al eta ayer 223)-0) |) FL3 225 |) D160 rns) 2237-83) EES 7a el eanTHL Ole 2247s eit A 220 007 sOe| att O)<6 2250) Well Aver palel Ohad a) WeTSL eg iE 220e5 o\ etl ye?) ehh oO) fy Ise 7tO 227 eal eae 4 | INO 4 sere oer 229-20 |eREOr | | PLO EO) cleo 220)-2eEL6.-O4| L20R4) |e Ee aT 220-Te | hg 1 L20,-Onerr 26 22 TAO 9 haig One teas TZ ObeT 22 Oh ethos eke Ta On| bT2 Ol 232-74. mt SiG! | T2204 | 27st 22362 RE O)O i220) |) L216 234-5 >| ILQ)-5 | 223 <4.) 122-1 235 °4 | 120-0 | 123-9 | 122 °6 23623 | 120-5 |'i24-4 | 523)-1 237-2 enet-Oul E24) Quiet 2 3-0 238eT | T2Eeh | Ves A et2 quer 238-9 | 122:0 | 125°9 | 124°6 239°8 | 122-5 | 126°4 | 125-1 240°7 | 122°9 | 126°9 |.125-6 DAT AGH | t23 4 27 sa G2 Oz DAIS C232 ga-Q) sh 207 ZAZA | L2424)| L284N || 272 2443. 124-9 | 1289) 127.27 245°2 | 125°4 | 129-4 | 128-2 ZAG In|) L251-9 | L29 59 J r23 7 246-9 | 126-4 | 130°4 | 129-2 247°8 | 126-9 |-130-9 | 129-7 248-7 | 127-3 | 13r-4 | 130-2 249°6 | 127°8 | 131-9 | 130°7 25025 | 128-3) 9 rs2i-4) |erain-2 251-4 | 128-8 | 132-9) | 13h-7 252 °3 | 129-3 | 133-4 | 132-2 | 253-2) (r20)-88) 83 31-Onl lie ze7 2540 | 139°3 |. 134 °4 | 133 :2 254°9 | 130-8 | 134-9 | 133°7 255°8 | 131-3 | 135-4 | 134°3 256 °7 | 231781 135)0) | 134-8 2 grams total sugar. HAR OAH AHAHGD AAGUS UNUSUGH Orth Guar eG, ato) ume) on AH AH OG Copper (Cu). mgs. 2 i/as 258° 259 260 261 262: ZO2y- 263 264° 265 266 267 268 269: 270 270° 271 272 ch (a: 274° LoS} 27.0% 278.* 278): 279° 280: 281° 282: 283° 284° 285 286: 286: 287: 288 289: 290° 291° 292° An woo 6 nou a OHURY neu aX 277° Dextrose (d-glucose). HI Yn NYoHr vA Pa S48 NAR YNNA SISh I) Se os eS TSS bw SY Sse nu Invert sugar. SSN SAN spe au AHAHA HUSGMSO UOUDH 6udokr © Ww OW wow BS (o We ino Sa Invert sugar and sucrose. B @ Lan | ww nr us cou cow - 135 T3 Or H Ww Oo 137 I37 138 138: 139° 139" 140° 140 141 141 142 142° 143 144 144° 145 145 146 146° 147° 147° 148 148° 149 149° 150 150 I5I° 151 152 152° 153 153 154 154° 155° pS Ses HOR OAH Aoundu audsto EOROR OF OW Ww CW ond 0.4 gram total sugar 2 grams total sugar, Adeéudeun 6udseGo KORSGH ww cow cd W ww wn A OH AH IHN BN Copper (Cu). Ax ws 6 ANwunn Tod 6H” eH DHNOY WER AI® GOHNYW os oun KAN wos Dextrose (d-glucose). HAdsudu CNSCKRG FEOKRBCKE CK OH wD UW wo DY A AH OAH ou ony MUNSON AND WALKER’S TABLE—(continued). Invert sugar. 166 166° 168 - 168 - 169 170 170 B7L nels fat 172 173 173 174° 174 E753 175° 176: 176: 177° ORO © BoHOIS IUWEBIYAA HaAKUSd Uoudk Adsoudu NN HH Ow Invert sugar and sucrose. 617 0.4 gram total sugar SIA AAU CONOR G6 FOU OH YQSYKY HoaAHDS USUSK Ww ona s 2 grams total sugar FOL Ow SY 4 nN BAADAH USEUSEUN CGEEKE DH Ho woH SSG HAY’ CGudusd Copper (Cu). mgs. 328- 329° 5}5 532% 332 333° 334° 334° 335° 336° 337-7 338- 339° 340 341 342 342 343° 344 345° 346 347 348 349 ft 35° SOS 35% 307" 353 354 355 j 350° 357° 358 - 358° 33/25 360° 36i.: 362° 363 horus UU aAwoo oO Mw Wm 6H HWE RU Doo CSOH HW: wh OY NM OO OF Dextrose (d-glucose). 185° 186 186 188 188: 190 IgI- Ig! 192° 192° 193 ° Uo Oo wow oni PY ADA Houdu OF CORRS BOY OH IYHYNKA HOwHM Oo Invert sugar. SRoOWY NHIHASG USEroewk OW oONnHY HBAHHASG USOKGH cow cow i” DAHUOH Invert sugar and sucrose. 0.4 gram total sugar. SGu 6G BHeOHA SH YHGASU OR OK & Won YH DAHAH OF OF co I S8XY HO 2 grams total sugar WOW TNH AAU Ceuskr SG 618 Munson AND WALKER’S TABLE—(continued). S Invert sugar os Invert sugar J g 4 and sucrose. : g é and sucrose. a 3 3 =) 5 s o ep a = oO % = = : 3 a $ g *s < E 5 8 B Ps 5 2, 2: a. 9 5 ae =; Bo Be 86.) ee ae oe | ee % Ls tn 5° o % La iba g% ia) a a A a a mgs. mgs. mgs. mgs. mgs. mgs. mgs. mgs. mgs mgs. 364)°2, | 19377 | 1991 | 198-3 | 191-9 || 399)-7 | 215-2" | 220-1 | 220-2 Nong 3651 | 194-2 | 199°7 | 198-8 | 192°5 || 400-6 | 215-8 | 221-6 | 220-8 | 214 °3 366-0 | 194°7 | 200-2 | 199-4 | 193-0 || 401-5 | 216-3 | 222-2 | 221-4 | 214 °8 366-0 | 195°2 | 200°8 | 199°9 | 193°5 || 402°4 | 216-9 | 222-8 | 221-9 | 215-4 367 °7 |_195°8 | 201 -3 || 200-5 | 194-1. || 4033 | 277 +4 | 223 +3 | 222-5) oe 368 -6 | 196-3 | 201-8 | 201-0 | 194 °6 || 494 °2 | 218-0 | 223-9 | 223-0 | 216°5— 369°5 | 196-8 | 202-4 | 201-6 | 195-2 || 495 °2 | 218-5 | 224-4 | 223 °6 | 217-0 370 “4 197 °4 202 °9 202 °1 195°7 405°9 219 -ASSOFEMECH Ge. « tapaecseeebaees 22 Munson and Walker ................-. 533 INGO IsEAS siaciein- nse an eee aaa = pee 511 (Slee Kite Meetage scesdanecane comer ac ceaee 520 OPS MURA: ce oso ns inno aba duasmeiswonensee 520 IRDeNetrre sy -navencaen has os- 506, 518, 527 Pellet and Lemeland.................. 521 IPETMANEANATE Bienes cqcwscuenees er 536 IPIOSE hc se wcne oo sae ep eeneee eames oa 515 (PI@ra erty sscmc. ose serenere sees s2=-4- seer 524 FROMAjD. 522 os cence sennenreve-ncesriees-ee 540 GA GHS aes iae se erah cee ne neem aase eae ne 506 Sarllard pete s1- co vesveee ts serieees tan 518 Scheibleris...2- 2-as+ ss steseeets ees =s 506 Sol@aing< cates cnet onecarecesaiaes snees 540 Steterwald .........cceee sees eeeeee eee 517 SGundstromberc.oscssars cesses one arenes 528 WRERVOOTCI oy ou dus wewscccciseceee vewsiea sae 518 PROUMNANS 5.00000 susecee. ve os - sr eeepneeer 517 WA MIETION <. ccscanconensssestsgeesb 513, 526 Walken iccsacecaccccssseensare se -sgeonees 517 Wiechmann ...........eeeeeese eee eeees 5°07 WAIT GeIy pot cic se ss ane nicest anatase Peer see 541 Wortmann ...........2s0necceesesecesces 524 ZAMALON —.... eee ceeeeee eee e ences 509, 512 621 622 GENERAL INDEX PAGE PAGE ANGESILER SOUS gre tacteins ste ceesteacmeeet ss 64 | Bagasse, Physical Properties of ...... 463 Animal Charcoal for Clarification ... 509 _- — Use of in Analysis 509 PAMIENOGY. ANG: Orcs uces saison sa ccesetc ent 18 Argentina, Harvest Time in ......... 28 =P Raimi falas so ostewee aceceedccte 23 ATMY WOrM 2. ae desicesee es haoa ete 150 PA TEA GIS on satan ols don racine oi oases 568 Arrowing of Cane........ ren Se raeraeen 135 ASEXUOl Valtia OMGae scm case eeeee 2 Ash\s Determination: Of: #:2%.ces.citere 525 = MOL Cane Aeptase ses neces 16, 93 — of Molasses ............... 453, 525 a OL SUSATS i. ioanawseles viosoe cs 431, 525 INS PATA LIME: 5) rrp iaisiorsigeteiswigaiswegcesaeeocies 16 Aspergillus ‘Moulds -.2.0....-<-<.< 435, 565 ANSTEY MIUSLY: S HEeTOCESS) jaccce oat stem nea 575 ANGSSAy Ol Al CONOMtteansaseceeessionecteee 585 Pin PASI ote chase opols eisre aie slaia tine oreia yatta ate 525 == "Cane, Sugar. .......:. 502, 515-524 =~ = Crystals Sugars ies catceesestees 513 ad S10} Cort Berea one SER Ron aS RE eae cic 524 SUPE GLOSS pac atscinsslocmaice ses ce ehacbed 540 =e 4 GIN COSEssonrcnisiingeseteisicnsaen een 532-541 SAG UMS HS se aectotesshereescueteo 526 — Reducing Sugars............ 532-541 San WV ACCT, eid aalnusine't sisfrsisisnaceMiaaciorias 499 PASSOLUMEMb es AIM TI CAMe re mesitraete ties sats 429 <= Si Chanmeli cts. .sGasanqaue nase aes 42 == APAULOP EAM weiss cues cash oases eee 429 PATTEMUA LLOM cm aiis v's oe’ Sack saree coe aceeer 585 AN AIlADIS CSU aay conn che aececeser 493, 550 Bacher’s Sami plerics: Gasssiessae se eeeendae 548 Bacteria fn WDistilery: cesses tweet onset 570 ea AM OOM: Sshseershiccneenueakantertey S 66 — in Sugar House ............... 434 iBagassey Amalysis) Oftsae.spesonsesee eee 511 — OF, DISHMeRIOS fa eget Saat 2, 582 == 5t7, 519, 527 — of Entrainment ......... 371,560 — — Saillard’s Modification... 518 SPAS Facet Pests Hae oe 146, 151 — — Sources of Errorin ...... 518 | __ of Milling Plant................- 551 =... Temperature Effect in...” 516 == of the. Factory. -<-2:.2-222-.2-- 542 = ea en 517, 538 of Sugar Bowing ia. t2s23-e. 559 Climate of Cane Growing Districts... 20 =~ of Weight of Juice ............ 542 — Continental .....---.-.---.------ 2°’) Gonveyars; Geran 2.5222 2274..--¢-textess 426 — Effect of, on Cane ............... 24°) Coolitig? TOwers |. ; ..2.25--2-.. sdaahe teen 370 — Equatorial ey ea ae 20 Copper Determination by Reduction AE CINE tice ce noaw an onccsnaesteweses 21 Alcohols oe een? 535 oat EV ATICHES ANG aa 55-u- ons pe cosene sn 29 — — by Reductionin Hydrogen. 535 CONG TASS) cc. o-tens cence ves e ena see 139 — — as Cuprous Oxide ......... 535 Coefficient of Transmission ............ 317 — — by Electrolytic Deposition 535 OT Eyer are eee 579 — —— by Iodometric Process... 536 Coleothrix Methystes «......-.........: 574 — — by Permanganate Process 536 Colouring Matter of Cane............... 18 | Corliss Engine, Steam consumed in 330 — — of Cane Juice......... 258, 280 | Cotton Seed Cake ..........25.-.00eee0ee o4 Combustion Chambers............-.---- 464 | Coupling Boxesin Mills ............... -215 = a Volume of 469 | Cow Peas as Green Manure .......... 96 — of Bagasse (see under Bagasse). @reydt's: Process: <2 sis een--2<- ees 524 — Spontaneous, of Molasses...... 566-1 “Critical “P@sttions:s..<...<.a-ee--sdeent =: 476 AGTH PENS A. O Mage ae. os oes andepn sete 481 | Crop Time in Various Countries...... co: Compensator in Polarimetry .......-. 451 "| Crops, Rotation of. ..2c3.-.0 ee 103 Concentration, Effectof,on Rotation 504 | Cross-Fertilization ..............0.-++- 34 Concrete Sugar.........-.--.---0.-eeeeeee 428 Craibles 52. cniesesess nasi eee 534 Condensation, Central..............2.... 362 | Crushers, Hungerford’s .-............- 230 Condensed Water Evacuation in — Thomson and Black’s ......... - 230 Evaporators «.....-..s0ese+005 347 —=+ -KrajewSki's » c2:.si A: .0s- 08.125 230 SE CUSETS VARIN 2 oo scenes ss nsanne spa 367 S22 Marshalls ooo eee _230 — Barometric. .........--..-:.:+++- 358 an > SEAEN YS. accnien Suet ne ie age aaa EAGT UI ee ge ea 362 | Crystal Sugar, Determination of..:... 513 — Co-Current .............:. 359, 361 | Crystallization, Addition of Waterin 403. — Counter-Current ......... 359, 360 EO GDR EOE 4s acne a ee toe 393 — Cross-Current ..........--++-++- 359 — Development of ........::.:.. 392 Ete PMECHSIONS, Of) 25. asso 362 = Java, Process, of frist 393 — DIY «. +s eevee nese ences seen 358, 360 =—— Low Products of-<. 22./2-=- 404 — High Level ...........--..++-++- 358 — Rapidity of Cooling and ...... 403 POU LEVEL sok apt cccant sabiocwanence 358 == Sire of Pan and , AssUbieeb- ess) he Sap soqoaeer coo 328 DMIGCELSULAT, /.crtcassssacare acnseeewws se 429 — Rohrig and Koenig’s ......... 345 HBMPOMEMETOCESS (..c.dasatmsnial secs ta oes 514 aad SATIC OLIN Site cee piinsaticass Cements 357 UEGH SLANG ATC +... ssenqe-sessdeeceas- 428 eS ESCA Guinea Sauce ee eco eee 392 =a CAT GAT apres) opcean Saloons ee vaned 343 Earth Nut as Green Manure ......... 97 ——, Steam Consumed in: <..2.02.e26 331 Eckart, Manurial Experiments of ... 83 =—— Steam Distibution in).s...5-- 343 ES TECOM GS FOCESSHos tetrsccents oe sects cece 570 oS ELAS, so see sven teeee acceines 353 Bigy pie ClimaterOfmcaceecs ee cernn aces 21 2 SSUbpmMerseG. wll Meme cn< mie ell. 351 — Harvest Time in °.......6....... 28 SO WENSON Sten teeveuscmseneces. 350 san heat ah nto) that hae omar maneos tse I1O — Temperature Difference in . 20k — Manuring Practicein ....:.... 85 — Temperature Difference, Dis- Seen SAIS POE << Jot yak Oooh ae 72 tribution Of, IM .....seeeseeeee 325 Ejectors in Evaporation ............... 360 2 ADEs SIAS Ole ata Aad tendccon a0: 344 Electrical Processes in Sulphitation 295 Pee VETtGAlL“UDE) bncetenecaeee sent 343 HEREGHISPTOCESSES << (o.ases. ss ccd scenes nae 449 — Vivien and Dujardin’s ......... 343 Eutramment, Causes of »..5...00- 2s 371 — Welner-Jelinek ................-. 351 —- WiPrevention! Of seocenapeeddqodKconsthe 574 Haure Shredder: csnscteancsactsensancts 230 Belilimers TOL uOm Peeenee eeecee eee: 532 AFEIMES sacieiion ova temas eee aosisaadeetecnars 582 Fermentation, Alcoholic ............... 582 Seed SUEY TEC ores) ses a Seiten nceteeece 566 — Foaming, of Massecuites ...... 566 ats VACUIC ronnie daa te maelomeneriman maven iets 565 —— > INItHie Ofdvlolasses: ea ose tee 566 — Spontaneous, of Cane Juice... 566 — Spontaneous, of Molasses...... 566 = -WISCOUS © sskostaanscandseeasaetee ses 566 Ferrocyanides as Defecants............ 295 Fertility of Cane, Discovery of ...... 33 Begiiliza WonsOh Came saaaeeeeneeeee 34 IE IDLE NeASSAV OL ia. remas eee ema 512 ——, Quantity, of, in Cane ~......2- 15 — Composition of............ 15, 454 — Compression of ............ 187, I91 = Determimation of 7-7-2 /s.4-4.0.. 524 == S Eele Villian Oka sseeaeee neti aee 470 Film Evaporation ......... By Sesh T a5 e Biliter MlaSKS wir w.cesenarsencmctn cree 533, 534 Filter-Press Cake, Analysis of......... 511 — — Composition of ............ 307 — — Loss of Sugarin .......... 307 — — Manurial Value of......... IOI ——~ ==) FOAM pling Of... sesmasee.. 548 EUters\ Bases. qi ietancaete sh oattee. 302 =, JBAPASSE nacchintcemueeec eee een: 305 =. (Capactty (Of s.c4c.8-moten eines 306 == Chamber * ciecsince sae doamemeetees 302 == Dame) he gases tere coe eae: 301 =e MECO ly: ite. cies sees cinta c ence cet: 304 Spe) CAP aberisc dove stiaetsanesearee 304, 307 == Wilehsthoybl Ehaveral xis cconcassccsence 305 ATA aera side et oceoaar eee anaes 301, 305 = OMEN Sti serratcvonne Settdneioce tee hes 302 —— epi late cnc einai Cer aaeeeneer rr: 302 ==" StOCKIMee «6. etme seaseatees ens 302 ==) (SWeetland de : ecererunacteecam eras 304 SSW harey (GARIAS. Gadd cobdoscsuospeaser 305 Filtration, Development of ............ 301 =) Double. isc eee eee en 306 — ) Media sedans. acter aie eee 300 ——~ s PractCerOr = yeseie een eee 301 —— (Principles; Of Iss.e-7s ence eee 300 First Sugar and Molasses Process ... PAGE Blashy Portserss-rscesktoscsesecceatsisee ane 364 lash Rotsiatran-cena,.0 Check Walls im) - si.ccadseeere 464 — Combustion Chambers of...... 464 +" COOK'S! ices t ces cance nnaeneee 465 =~ Culbanl sts sete basa eee 405 = =~ Plat» Grate n.ccch.,.lonnanidaeeeeee 465 == Forced Draughtim 7-2epceeeee 466 —~ (Grate, Area lofi. ss os..ntrseeee 459 =) HA Wala o..nseKieiciscierwenrnseeeeeee 464 SS" HAVA. | ninshiers os sein see Reena 464 == Marie's: esa. seinen. cats eee 464 Gases dissolved by Water. (-ce.ceree 368 — JImcondensitble) 22. .o--eacneetae 344 Gas Washer 0-% tonlier aces ine aon eee 283 Gay-lWussac Scales cn. ice scn eee 583 Gearing of: Malls v.02 ses -eneeaseee 215 Geerligs-Hamakers Process ............ 255 Geerligs’ Theory of Molasses ......... 446 Gendar. Scale |i... s2..5e.2 nee 583 Glucose, Action of Alkalies on......... 265 — Action of Heat onls3...s-cene 265 — Action of Lead Salts on ...... 537 = Determinations. ..-ccreceee 532-540 — Determination as Copper...... 535 — Determination by Perman- PANATE swiss. seklehe anaes 536 — Determination Electrolytically 535 — Determination Iodometrically 536 — to Non-sugar Ratio............ 537 —— Rotation! of 2... daceenesteeeee 502 (EihbereWnabbavey aAcndopsoocodceungnoousojcdajoo8¢ 16 GENERAL INDEX PAGE ‘Ci S ES ae hac dace cacbecacdsbussadbaecedase 567 ly COcolgimh Canes ser ssterc cece: seees 16 Peeve CAd AUTEN) pe eemase See ao ose wna: 534 Granulation, Methods of obtaining 386 Go SSS aI LPG) Sado sndanaenog esoscsocsdoc 139 Rea MGLIEE So Src cntcwes och ust scone 142, 150 Grate, Forced Draught ...........2... 466 MEN AT Soca hcetaaceteeeecs ote te 465, 466 eT OLLOW A ewer sbons ome acaae acca sles: 405 == 4 SLESD> ¢ cuosiebaansgasosospeonss 466, 467 Sue adn JETER? Gadetacobas Pscppaadseanoee 493 — Purity Polarization ............ 493 ee ESO LIES § My aaone omen cnet elas « 490 — Solids, Effect of Dilution on 491 RRS COMO VOCE UANsase oa cnes sates asec 182 Grooving Of ROMerS << 3-2 eas-creces swe 231 5 TB Cena SS Re papeics tae aecoe toe nee enone 16 SESTUGE ” sGoepdetoss eecr ceecdbsacbessbocasbe 94 MG TUNG VGN See ss ces 22558 5s8% ssaosesesesese ves 571 Gumming Fermentation ............... 566 Sams Metermination Of" 2......s eaawaseaaiecaebee sttesece eins 95. |) Mall, Aitken’s 272... enacitanen een 202 =a GY PSUMEAS. (oc, scaasaceessncee sia 95 — “Allanis so ona An enteccceooaeseemeer 200 st RAINIGIAS. csclone teen saeieseeee tess 95 — Alliott and Paton’s ............ 200 ye, IBSSSEIS Gaccovegipesd soeeosaon0500p I0o —" Bartlettis) ~-:smje..ssseeceeeemeeee 200 | =p! Bibs ene: I tenSeee pen ae a Sac ect aneoe gI = SOLS) Uomsduss gticeden aaa eee 201 pnt VI OLASSCSMAS) tre aeplesiate scenester IOI = - BOW CE Siciss sles nc saeco ss eae 200 —— Nitrate of ime as: sates. 94 — Buchanan's) ~..4.9s5.e ese 199, 200 — Nitrate of Potashas ......... 94 = CHA PMNINS eae iets cls sae eee 202 — Nitrate of Soda as............... 94 — , ACollinge’s; aces. ecace eae 198 > EIT go scscoonbuadnntecedsaocuscD0be0n 98 ——_ Mea COniS ies anacesactnatem memes 227 =~ Phosphatessdsii ne -o.69-/10 90, 95 —. De Mormay’s : 5.62... -,eeeeeeene 228 — Plant Residues as ..........:.... 99 ——) = Delbert’s-2::..). Scccsteme-eeeeeees 200 =P OLASD AS! -- cahiaeiisteeceleasree nets 95 3" FISHES Sosccinesneieieate oo ee eee 207 P= MI SCCM Ga KOrzc'S cai setae nett 94 es PE LOTCHEL 'S). Mactan ose ee eee eee 200 ee SPE CHIC ul teCt Olmame rma att sielette 92 =) HORATLY?S i aaccene ack aaa 201 — Superphosphates as ............ 95 = (rh AGULY: |S csiiaysieisjeislele Os cistete sce rae eeni 227 ——, MaMa Ge saSre.teretenscsmetees sou 94 me» EM ATS sav acctew ci'nlern\o\o'ais elelerc ieee seater 201 Manures, Distinction between Nitro- eeente = chashllvoyolche minaanesoneGd iano sac" 200 SEMIOUS ses eeeeeeeeeeeeeeeeeeens 89 == (Hatton's! 020 See 200 Manurial Experiments in Barbados 82 = Medemann’s: 2525...csis-cecccneeee 201 — Experimentsin BritishGuiana 79 == Hughes” 2... vecssne: sohnns hee ee een — Experiments in Hawaii ...... 83 —=— “Le -Blane’St: sees ste eseeeeeee 227 — Experiments in Java ......... 84 —=" IMCNEll’siiaethe nace ners ates 200, 202 = PTAC CEM DERM ttes te eter ete 85 =: Mc@nicis’ “eiinias.. cuecene eee 202 — Practice in Hawaii ............ 85 == PA eIiSt is dccec sas-cdene nee eeee 228 TACT CEMIM fic Vidartes seis steer asic 85 — Robertson & Hudson’s ...... 227, — Practice in Louisiana ......... 85 —- -RODINSONIS cesses ee eee eee 227 — Practice in Mauritius ......... 85 — Rollers, Construction of ...... 201 Manuring, AshofCanein Relationto 93 — Rollers, Grooving of ............ 231 — Effect of, on Composition of ——- | Rollers, -Settine Of7 27.55. sae 223 Caner reir een oee ee ea as 92 —— sRollers, Speed of 25s... 226 Marguerittes’ Precipitation Process 451 == “ROUSSELOE’S skeen: noone 199 Massecuite, Analysis of.......+........-. 510 ==" “SKEKEL'S) fie suse siecee soe edare eee 200 — Calculation of Quantity pro- —='. Stillman’s. 54.52) b.scoessueseeee 202 ne Cimemctcioesecsecssncarseetayt 394 | Milling, Algebraical Analysis of ...... 232 — Determination of Density ... 497 — Extraction Economics of 238,.243 ——-, Draimage Ofadisenvces ee ascetes: 407 — Preparation of Cane for ....... 228 ——-, SAMPHNG Of. oases cesar ns 561 —= TP Talim) Oeaieas. ceeeoe seca 217 i TANS POTtyOLPemaseser ber (saseeie 407 >| Malls; Actual Pressuneii is: --ss.. seems 221 Mauritius, Canes of 41, 51, 56, 57, 60 == Capacity Ot sec o..cesaesse tee 218 ==. Climate OL caacremecnemestenstaeeers 22 =) ACONtLOl Ol; 5: --ateeces wes thee 232 ==) VCultivatonwin wee cnse eeeee 129 —— Development (Of. -ss-soaeees 197 — Distillery Practice im.....:...... 568 — ) East ‘Indian: =.23tv.2.:- sss 197 — Green Manuring in ............ 96 —— Blectric Drive tOn....6.0-ns ere 217 GENERAL INDEX PAGE Malis OnT— Olle ren. ssaske aceeeeeenceue. 227 SS" Cech niinlttes Rove (Abe soenun ce eEOeOcee 213 a AO USIMO e Olen onan noses ee cence 202 == Motive, Power for: ..:..0.62.j0% 215 — Multiple-Roller............... 22 =e HPETIOTMANCES Of sein. ooetaee 247 — Power required for ...... IQI, 194 GLA PeTSe Olen mers. senate e acai 213 Beer etnies’ is Nohivecte isk voaiseaes: 223 EIS LTESSES SUING o,.. Saje ciate ws cfese et esos 219 ae WORONET fit asec etm sawnnsess 228 eee TEC Tolle Tae reece eenels 197 Mohr-Westphal Balance ............... 404 Molascuit, Manufacture of ............ 452 Se HOOU Viale Of 5.2. sc -miecte cus ee 452 Molasses -AlCONO! frOMl 12 -cien i fs5ccsec:ee<<-: 366 EERO EATING CPS ctinc scenes shodece ess 363 a) SHOE WVAlVe 20.2. aawee we cack xe. 363 ae POEDEUO fei scakc cee occ siaccdbe neste 363 mae MAC TRESN 255.5 20s San cece sess 362 — Volume of Air removed by... 367 — Wegelin and Hibner ......... 364 Se) (aU Rec ae eens 358, 363 Parity, /A bsolute Vee <<. vociesdosion--s- 493 ot NEALE bia ees statsn [Baretojss.uiaineees seater 548 Revolving Knives in Cane Milling... 229 —— COMEMUOUS--“cc0scnsnte leer 547 Reynolds’ Hypothesis of Heat Trans- == tt AVOUESHf inte ibis evnic eee eee 547 MISSION .......seeeeeeeeeeeeecee 313\,| Samples, Preservation of:....0..0.se-ee 550 Rdzome-Of Came. i. 265. sae ups Keeeak: 7 | Sampling /4.: naeivets eee ee 546 Richard sone Wei Sher ieens.cs' teers: 542 =~ from ‘Containers a5. -ee seer 548 Rillieux, History of his Invention... 342 — Of-Bagasse’ svar. A0s: sence eee 549 Rollers, Construction of ... 195, 201, 231 == of Caner 3c tiene aces 550° ei, PO UTEU 2 care sete lstemetarnee aoe ce 231 == OL JUICE eo. ue hae eee eee 547 =e GOONIES, Ulan teem dsrace stains eie se 231 —- Of Massecuite 222. se-naeeeeee 561 ROM BESTE TOCESS) eet ries saeiacen tee sertacn: 540 == 1Of Molassess\.n.daiscecsuscseetere 565 Root of Cane, PunctionlOf ..2s.s5-- 8 10 —— + OfiPress» Calkesc. s.r .eeee eee eee 548 — of Cane, Structure of ......... 9 = LOf Sugars <.s.ass5 580-ca ee 548 —- (systenl of Cane... :istiecsscces 7 = OLS SYLUPl> iassot. tances 561 Roots eAdventitlOusm ses eeeeeeete es 2." Sand. Bilterse.cG..ccteosee. cae eee 305 Rota oniol Crops: wesssceseee are 103, 171 | Saturation (see Carbonation and Im- ——-) OL Polarized: Wight aya enesseee 473 bibition). == SPCC, Of SUATS:..J.s0-se-505- 502 Sawanh Landy.) jacsesthadcesccue eee 75 Row: Width Of tac pins ester wasesemeceste D30:| Scaleine va poratorss.-2. saeco eee Sa/3: IRI PAT OMA Ob ecm nae cemee serene seenees 573 =—) Kands wots ~ cnicwaecteesa eee BS COLO UTAMOvOL oa seen Sea ee rere 575 — of Polarimeter, Control of ... 488 =—— Common’ Clean \.a:..2:e-cetscsee 573 = “of Polaxiscopes .caisswuseeee 487 ——= COmpPositiOn Olean dseae see Spicy) ==. JRemovall 108 Biscauteeeh aeee eee 378 =) DeTMitdOM (Obi 5. sacscce nase eee 571 | scheiblers Hlution sProcess:+-o meee 449 SD STMELAT Au seis eet eeaer ace cece 573 | Schizosaccharomyces ..........-. 564, 565 Se) PAB AULEY Feta defoas os eee esonrowe's 574: |) Scolidstas Parasites -vs.a. sss LS Oats == HlawOunr Oh. scmetceee ootosaee oes S73 el eSela PELSMOLA MGI Seeseeaneeeeeeeeee 213, 249 sen, LEY IENICE Me eacaobecoqcubereunnen Uouce 5973-|-Scum Piltration! ..2:)..cce-s0 se eee 300 = Mania Chure Of nvenn saves cecaee- 567- |_ Séthetiess Fuss. ses costed eee 47° — Manufacture of, in Demerara 568 | Seed Cane, Nurseries for ............... 131 — Manufacture of, in Jamaica... 569 = Cane; Source. of as, 00 cneceete 131 — Manufacture of, in Java ...... 569 — Cane, Quantity required ...... 130 — Manufacture of, in Mauritius 568 ST Grail eo. thc daa tila nae 387 ear Casts COnmMeC fede wi. bE r. tier. 568 | Seeding in Vacuum Pan ............... 387 Seedlings Barbados <.....-00--e eee 38 Saccharate Processes ........2seecee0 448 == .Bovellioms.c.%. sociation teks 38 Saccharatesip oscscetcsenn es heen eee 448 = ~ ‘CrosssPertihized:".s.s.5se sere 34 NaACChATEtBY raw. . to chcghecty ates eeeeeN es 258 =~ “Demerara ..s2tis.need 2 aeeneneeee 35 Saccharimeters, Optical Arrange- — Discovery Of. 2a i eee 32 inneseas) XOLi - (Gonsouaponuscaudeoses 482 SR ckart) OM. concent ss ea eeeee 38 ACC ALTOMY CESm aera camcrmenceete ere 564 = Harrison:0n-yiac-cee.ceen eee 35 ee VOLC CUM Mitts aes. sien erie ere 564 <= Ha wallam. vis 2 2 -on 2. ..-.2.:eedssisove.. 0s ZA SOMOS. PO tlle ry cous setras teaphia Su xn ctis whe 490 Separation, Centrifugal ............... 270i) SOXDIED Ampere: csstk sew ase. ekae esos eee 533 mt FOQEESSES 1 eet oo eae ren wens ecee ss 450 | Soy Bean as Green Manure............ 97 Settlers, Continuous ..............-...... 275 | Specific Gravity, Determination of... 493 ee IMUCTMMILLEH Gc. cosas sccees- oe - 274 ——~, SEIGAE 5 Sok sesenaet some oe eee 310 Settling, Mechanism of........... kee 269 — Rotation,Effect of Concentra- SCRE UE ESIC: 25> te ocean eeern ees < 270 [ELUM OO pee ees: oe ae Seas 504 Seepite MAPALION “22025-22505 n= ons a-- 32 — Rotation, Effect of Inactive Short and Long Ratoons ............... 135 BE acsne oie ere 5°S TOLLE iene ela ee ee 117 — Rotation, Effect of Lead Salts eee See ee 0 eee PS EE SP Ae ged et 506 se — Rotation, Effect of Tempera- Sezedders. Call's | ..2.32s.2 ia Aso wisn pis adie 38 402 = WS) Siitein sl Ororll Biter eaeaen a ereaee 400 639 PAGE Vacuum Pan. Standard: ..cs.....e<0es 398 er TL ATS Monscsoce souts.o<'s cee 23 401 ——- ee VETLCAIMCUDES aac<.n5ces.': 401 Ee VI CKESS Urs atone teeth a scectes : 40 -Ennubaednchon wang woeescooaadocop asta 49, 50 P.O AES Bali se vacate eee 40 Sr biiokess ene lean ane snore ARORA ea araco: 48 P.O: Ji, 228 eles ete cane ea oe gee 41 IB IIKOOT gaeabopeuedeenocaadnaechecocnhoudoo: 39 Ie On) 5.7361 aso npngenpnnnsccobesbosedoo00¢ 4I MARV AIBATA SS copic:sutactenle ctrelelaeam = lo tee eels 61 P.Oz] 247 wives Onn. eae eee 41 Valonea\ey JBtunVOles se seenanncoodecoducdorac 54 Palania ie trartutivenons stn eee eee 61 IB [OV OYE noae.cocdostedosoupbaoabavonbbuce nhc 54 Bamachee livin ne ester ee cape et eee emete 54 PA AOGIM eC yies erie esictsisioe ceed asacoseeeias 42 12h OF) cas ne ononasandonesaccdounadadcsccon: 61 whoayoVesaGn| nas nadpocopoosoaosoaacodoeaSoudoT 60 Pain dalatetce stoic) or eee eect 60, 612 i hoVobich OB eenaaananeamencAdccceocdeuncsqouccac 59 JRabaeh alee eae gqocboncnEppormbncacscdsqoce Sc 57 t(Yorhnal oysiVen) iaqoop ouacedoosaoradeaeroneaccs 60 IPO=a=Oleyaa-ae- sti bise tee ee eee een 58 JJEROENBYESIEY So coSspnaeanenAnaadsoodasosneek. 59 | Po feyRcYahe = GRoqoonecccobooedoooGasaccodoos = 60 TER OHNEESY concpnoas codccopnpbesdonsodcedoos 54 Portiar Pe seeeeeatsscscseee secant 51, 57 HEN Sbeacccasdaoosonde sd yscocauoano0ncor 52 (PortiMackaysesccscccnnssscanceranet - 57, 58 LAGE evateghy= sopdogsoqdapanodesosnoanaaacot 57 iPreangert Me secee-ceston ete 54, 55 1RCesobiel Get cb hop Reason be ocAa saneruccocSo 51 IPAbH EAN ONL BL aac GooRonsbedodsadsosmooooKoe 60 TRO MIKC AT Beteenchrtcistowetraceneas nace: ele 61 Purple Bamboo! 22.2... seceec ascot 54 IEGHIINIG ENS SopsqnonenbanepooodtenscasousEe se 59 Queensland Creole .......-.........- 54 Ib; Gil It: aaqgaqacnoapecadoassaobasdaKocdndooD 42 TRU DaOINS qaccooeedonstbooDNapedonAcadrron: 42 Tea PiGes hea cenn cap naci cat cenoenasenaes 54 1542} 0) 0.0) A wennoopbeE conboo NO Uso AncascoocAbc 53 Wea Heat 1 ay so meale eres svatetaleleteteteletetstoretlew acre aiesre 50 ISEDVANGIEY “Shc ocacodasvoappbonosscoceseaTooc 54 Ty GO uit th aerpaye sia o taiavelaretctaletan ns teeter ieries 2 Bde BRAC MERE icORr AS CSA aCCCt.c °- 55 TG ETIMETS = Sietlstettirctasajotesteranerste etsrelosiavaier 51, 612 REStAlL Gsces de aches cere eee enee 60 IL(OMNISTERAE, Shooongnacoscassdodag so5anacnc 54 IRWoYCINEN Ga pocobndunPondss Scingbudaads secon 57 TBOMZA CLM esse tdattanate cteretsionttae tates 42, 50 Rose Bamboo) :..5 ah sa sceeteoeetcee tenes 564 == JOf Cubana sot taiisetecadneenenee 5605 ——~ Of, Memeraray: sores. scesoneeee 565 te OF | JamMaiCa evs. cecase deme oe 565 = OF) JAVA. scccabaceeeeecases 564, 569 a= OL Natal 2200. sence cmnceseertcn 565 aad GOL LOT U, . S-aereincrecarmssiaestatiae eee nce 565 =a Ole PATIG AY scutes sate ave sete ets 565 = pO D:das qaantiae som secosonace SpeOneSOue 564 Nieds Eee rocesses si Unrem cer eee ree berhace 571 —— Use of, ini Analysis: <<.-.2-pese 520 Mellow; Crystals! “2 sc.nen.cceee. sapien 429 Yaeld’of Cane ini C@uba) -cesc.-.euceceee 138 — — — in Hawaii ............ 137 —— eh se haleal hatch} Pheasrinccoadsee 138 — — — in Java ............00. 137 — — — in Mauritius ......... 138 — — — in Queensland ...... 138 i es bo Vel 2 2 8 ce 138 — — Sugar per Acre............ 137 Zagas SY SPC se see senescence 134 ZamMaroOn: Ss} Method sameenaecessses mama 512 ZygosaccharomyceS —....... ses eee 564, 565 oe oy INDEX TO PATENTS (Unless otherwise stated, the reference numbers of Patents given in this volume refer to Patents of the United Kingdom.) BAGASSE FIRING : PAGE PAGE OOK: ain. vo snven cede ateeseneepas 465 Aspinall sic. 3csca= 2 eee 427 Crosley. “a keeeec eer eee 470 BesSenler 9. weas.gecteee w+ 409; 427 Bryer.and AUuotives...-e-naeare 466 Booman: ca-<.0s-e eee nice 408 Gros-Desormeaux .........+.. 470 Cottle:...ct:.4...+- 7 412 MATIC Wena secncateceoonser ts onrehs 464 Donner <.cc.casesteteci eee 424 WW Kejaarel een hen nerhostuacascndenss 470 GOrdOn wedseabecnden oe 413 Stirling Boiler Co. ...........- 467 Green, 2\.22) Pfs) .t Ree 413 Cant CHeaNG: a nchwee beds pe IB erCerra wesc wane 176 He ae ee be WSOIGCH: Sere gtacs ace taseeeeessere 176 = yh ke saree gaa Beet: alicoe ani hese eee 176 ue coat see dea ceased seooaede een 409 Dae ee 176 — He Yc dlass dt poss aoe ee 412 GaniSSiralie 7c oewts. tas cdednceoss 176 -— AW ott aal 473 (GTI AGAs popcoe: sav eseas Seen mamas igs 176 sidiaw and ae = VEN WOOG) 225.6 snriccsspatdeosos 176 Pubinsie ang are 425 Hustace and Smiddy ......... 175 Rea eee a ot 414, po FO BLAVO jecwosawutiaeieaeia cre 175 M WN ISSES S aa 5 TRE ol Le ee ern i aed 176 cel wiéddis algsatis procs ohaneeeaeeeee 413 EOC Se Ser ooshe ge enot anode eae 176 IM sagen eae eae cea 4 Patterson: (i232. sssansseoeseeme 25a Pal esscecuecas kaos wees 175 425 PIE Te wa Ok, Vic locate Oe 175 Penzoldt. ........000 Sse 408 SIOAMIE S255 docs see aeaeeoteaemnces 176 2 ae i. ee Be Shek ines tsecc verdant 176 Roberts;G1bson -s-<- ae 4t3 SLOMNSOM -Weeatseeesexensce nee 176 Ses Seay” ee UNITES «een acme aes be Ch peta 176 TS oer eo rr Sillema< 2.2 Gets. sacs tee eee 413 CANE LOADING: SEGWALE j.ccecekan 60h ape ee eee 42 Bennet eae ee pee anes 176 TPHEISSEN oc. s0cein spleen eee 414 Crozier ia Sra stu teeter 176 Tolhurst, c.3.34:c05 see A4I2 PRET bert” Sie ce otene scewet erie 176 WALE sockccbs aoe oeteuceenneeee 416 MEGA bos cau oes ace caene sewe dele mens 176 Weston oho vale oe eet 409, 413 Ee GApING: Williamson. ....deheiscecee 414, 416 ce Peer eee Sh cae ac ens oacamn te os DEFECATION, CARBONATION, ETC. : aA be, ea Le eee a Kast iba Aes Battelles 22 .t.2 sence eee 282 Mallen gee | Bessemer 2 IRODINSON 4.5.2.2) -oesseen eee oans 181 ae oe Borguitete ae gis Sanchez o)23. st enacaseeeeen ones 181 seer Ab costae aaa F a LUCIE Pps teeecactasprrt och ae Galisyctanesences sas ganisane sa Cee 205 CENTRIFUGALS : Gill keene ees osaehs scene 295 ADL fie. otncsceen dere eceaeaen 427 Gwynne and Young............ 295 Pll be is ie eembers Saeo cost deictic arbor 408 | Harvey and Scard ............ 278 642 INDEX TO PATENTS PAGE PACUIOM epi cathe sb twat a dein ees 279 SEES CTS) Is Se Reheat ee Der ree 279 BUS Vateans 6304 -Gaene vp twee sees 295 BLOM aIN Le esas cavk cb ware' 3. 294 TS igo OS he a 205 Wats eee accede age asc cust 279 RRMA A Sno ons aetna ne tivesekt 279 | Se SPE RS a ence ee er ae 295 BNSISUL, Sis shies dee nee hon osn open etes 295 BORAT: Cetreek Ue hits < wanes 204 Pickering and Macgregor ... 275 eRe aig hae oss Spee ee RE 279 Possoz, Perrier and Cail ...... 280 BRITAIN 22S A aninnts owe ie 8p oe 278 PRGUSSCANE Seon ence red waht ayes 280 BEIGE | sna ce aioe as cates: deed os 293 PICOMOEE F cee sac osnpehne’ caahaes 205 BIDCRVAL C3. Santee ates oie sne saps 290 BUAIGES Shp ocala haces bss Lesa AN 204 EL SRR AR ce eS Se 289 ECL eae ee ae ee 295 aOR. ake. o pean nanpracks usieas 273 tres yo and: Parker’ o2 se 340 Vivien and Dujardin ......... 343 Waebel and: Picard-<..2a.6ar 354 WWHISOID) :.-.02....eseenn 451 Scheibler.3.2..00st ee 449 Steven: Jc y.<.osenre ae 449, 450 Wernicke <.2.:2..225.-s.c00 Pee 451 Williamis, °...<-.0...-. « 62:05 ac-a seen 402 Preytag. ti -c0ss0s.5 see 401 . Greehwood: -.2.....; 5005: ee 398 Loren’ «02s. iieceS. sees a 400 McNeill 2.2.50. so aeeo eee 402 Shears.) :3.tee.. asses oe 402 WiCk@SS. 2i4ncnsghoseseo ne eee 400 Walker: cx. ccn tchecane een » 40T AT THE BURLEIGH PRESS wo J Avesta Ninel St lal hla aia Sa am New York Botanical Garden Library WN ;a 00067 9496 ¥, aa rita gies Pi ite