Sox, JVo. Essex Institute. LIBRARY OF FRyVNCIS FEA.BOI3Y PRESENTED BY The Library Committee shall divide the books and other articles belonging to the Library into three classes, namely : (a) those which are not to be removed from the building; (b) tliose whicli may be taken only by written permission ot three members of the committee; (c) those which may circu- late under the following rules :— Members shall be entitled to take from the Library two folio or quarto volumes, or four volumes of lesser fold, with the plates belonging to the same, upon having them recorded by the Librarian, or Assistant Librarian, and promising to make good anv damage they sustain, while in their posses- sion, and to replace the same if lost, or pay a sum fixed by the Library Committee. No person shall lend any book belonging to the Institute, excepting to a member, under a penalty of one dollar for each offence. The Library Committee may allow members to take more than the allotted number of books upon a written applica- tion, and may also permit other peisons tlian members to use the Library under such conditions as they may imi>ose. No person shall detain any book longer than four weeks from the Librarv, if notified "that the same is wanted by an- other member, u'nder a penalty of five cents per day, and no volume shall be detained longer than three months at one time under the same penalty. Tlie Librarian shall have power by order of the Library Committee to call in any volume after it has been retained by a member for ten days. On or befoi-e the first Wednesday in May, all books shall be returned to the Library, and a i)enalty of five cents per dav shall be imposed for each volume detained. No book shall be allowed to circulate until one month after its veceiiJt. ELEMENTS OF SCIENCE AND ART. VOL. II. London : Printed by A, & R. Spottiswoode, New-Street-Square. ELEMENTS SCIENCE AND ART: FAMILIAR INTRODUCTION NATURAL PHILOSOPHY AND CHEMISTRY: TOGETHER WITH THEIR APPLICATION TO A VARIETY OF ELEGANT AND USEFUL ARTS. By JOHN IMISON. A NEW EDITION, Considerably enlarged, and adapted to the improved State of Science, By THOMAS WEBSTER, Sec. G. S. IN TWO VOLUMES. VOL. II. LONDON: PRINTED FOR F. C. AND J. RIVINGTONJ J. SCATCHEBD ; J. NUNN; LONGMAN, HURST, REES, ORME AND BROWNJ T. CADELL; S. BAGSTER; J. booth; J. booker; j. Murray; j. richardson; Baldwin, CRADOCK AND JOY; BAYNES AND SON; J.HARDING; SHERWOOD, NEELY AND JONES ; G. AND w. B. whittaker; t. tegg; j.bobinson; AND E. EDWARDS. 1822. CONTENTS THE SECOND VOLUME. CHEMISTRY. Page Simple substances 3 Operations and instruments in chemistry 4* Pneumato-chemical apparatus 12 Of the nomenclature of chemistry 19 Caloric 22 Light 33 Electricity 35 Oxygen -. 36 Nitrogen 39 Combinations of oxygen and nitrogen 40 Nitrous acid 44- Nitric acid 45 Atmospheric air 46 Hydrogen 49 Hydrogen and oxygen 54 Hydrogen and carbon 59 Sulphuretted hydrogen gas 61 Phosphuretted hydrogen gas 62 Chlorine 63 Iodine 66 Sulphur 67 Sulphuric acid 69 Carbon 70 Carbon and oxygen 71 Carbon and nitroffen 74 Phosphorus .,, , ,,,,, 74 VI CONTENTS. Page Phosphorus and oxygen 76 Boron 76 Fluorine » 77 Alkahes 78 Potash 79 Soda , 82 Lithia 84 Ammonia 85 Earths 86 Lime 87 Magnesia 89 Barytes 89 Strontia 90 Silica 90 Alumina 91 Yttria 92 Glucma 93 Zirconia 93 Thorina..... 93 Metals i 94 Platina 98 Gold 99 Silver 101 Mercury 103 Iron 104- Copper 109 Tin Ill Lead Ill Zinc 114 Antimony 115 Bismuth 116 Arsenic 117 Nickel 117 Manganese 118 Cobalt 119 Molybdena 120 Tmlgsten 120 Osmium 121 Iridium 121 Pihodium 121 CONTENTS. vii Page Panadium 122 Cadmium • 122 Tellurium 122 Titanium 123 Chromium 123 Uranium 124? Columbium 124* Cerium 124< Selenium 125 Vegetable substances , 125 Animal substances 137 Nomenclature of chemistry 142 MANUFACTURES'AND ARTS. Making bread 147 Brewing , 153 Bleaching 160 Dyeing 178 Callico printing 198 Tanning 101 Currying i..., 211 Manufacture of soda 212 Manufacture of potash 214 Refining metals , 215 Pottery 228 Manufacture of glass 235 Varnishing 239 Japanning 248 Lacquering 258 Gilding 261 Silvering • 275 Tinning 281 Bronzing 282 Soldering 283 Moulding and casting 284 Cements 292 Lutes 304 Ink making 306 Removing stains 310 vm CONTENTS. Staining wood 313 Staining ivory 316 Miscellaneous receipts 317 FINE ARTS. Drawing -... 342 Geometry 348 Perspective 374- Drawing the figure 388 Drawing landscapes 400 Mechanical drawing 403 Painting transparencies 407 Crayon painting 409 Colours 410 Of engraving 419 Etching 423 Mezzotinta scraping , 431 Aqua tinta , 432 Wood cutting 442 Etching on glass 442 Lithography , 445 ELEMENTS OF SCIENCE. CHEMISTRY. JHLiTHERTO we have considered the action of bodies on each other in masses, or what is called their mechanical actions ; and for this purpose it was not necessary to attend particularly to the difference in the many species or kinds of matter, which we distinguish more or less readily. But if we present bodies of different kinds to each other in proper circumstances, a certain action takes place between the minute particles of one sort of substance upon those of another sort, by which, frequently, the individual or peculiar properties of eacli disappear, and a new substance is formed. The study of this action of the minute or ulti- mate particles of different kinds of matter on each other is called chemistry^ and the powers thus ex- erted occasion chemical actions. Independently of the enlargement of our views of nature, and the pleasure and entertainment de- rived from contemplating her operations, chemistry j^is essentially useful in many of the arts upan VOL. IT. B '■2 CHEMISTRY. wliicli tlie comforts, and even the very existence, of civilized life, depend. As exani])les, we may mention the arts of dyeing, bleaching, tanning, potting, glass-making, baking, brewing, distilling, working metals, &c. &c. which owe their present state of perfection to the science of chemistry In agriculture it is capable of affording great assistance, by explaining the nature of soils and manures; and in medicine its import- ance is invaluable, many of the most efficacious re- medies being entirely formed by chemical processes. In short, there is scarcely any art or trade which either does not altogether depend upon, or may be benefited by this science. I3y chemical means we are enabled to reduce compound bodies to the constituent principles of which they are composed, and this operation is called analysis, or decomposition. When a substance cannot by any means be resolved into others, it is called a simple body j and it is now known that all that vast variety of substances which we see is composed of a few simple bodies, which hence are called elementary substances. Formerly, air, earth, Jire, and icater, were sup- posed to be the elements of which all bodies were formed ; but modern chemistry has shown that this was an erroneous supposition. For the air, or at- mosphere, is compounded of several distinct kinds of aerial fluids or gases. Instead of one kind of earth, it is now known that there are several kinds. Water is no longer considered as an element, being, in fact, formed of two substances very different, viz. of oxygen and hydrogen. Fire is less understood, and is still retained as an element under the name of caloric. From the improvements that are continually CHEMISTRY. s making in the methods of analyzing bodies, or separating them into their component principles or elements, several other substances once supposed to be simple are now found to be compounds : and, as chemistry continues to advance, the list of simple substances may be reduced ; our inability to de- compose any body not proving it to be simple, but only, perhaps, that our methods of examination are still imperfect. The substances which hitherto have resisted all the known methods of analysis, and which, in the present state oi' our knowledge, are considered as the elements of all bodies with which we are ac- quainted, are the following : — Substances not metallic. 8. Iodine 9. Sulphur 10. Carbon 11. Phosphorus 12. Boron 13. Fluorine. 1. Light 2. Caloric 3. Electric fluid 4. Oxygen 5. Nitrogen 6. Hydrogen 7. Chlorine Metallic substances. 14. Potassium 15. Sodium 16. Lithium 17. Calcium 18. Magnium 19. Barium 20. Strontium 21. Silicium 22. Aluminum 23. Yttrium 24. Glucinum 25. Zirconium 26. Thorinum 27. Platina 28. Gold 29. Silver Sa Mercury 31. Iron 32. Copper 33. Tin 34. Lead 35. Zmc 36. Antimony 37. Bismuth 38. Arsenic 39. Nickel 40. Manganese 41. Cobalt 42. Molybdena 43. Tungsten 44. Osmium 45. Iridium 46. Rhodium 47. Palladium 48. Cadmium 49. Tellurium 50. Titanium 51. Chromium 52. Uranium 53. Columbium 54. Cerium 55. Selenium. 4. OPERATIONS AND INSTRUMENTS The utmost degree of mechanical division which we can effect in bodies, by pounding, grinding, and similar processes, can only reduce them to frag- ments so small that they can no longer be per- ceived by the sight ; but we cannot thus arrive at those ultimate atoms, molecules, or particles, of which the various s])ecies of matter are sup})osed to consist, and which arc, perhaps, incapable of subdivision. Besides the attraction of gravitation possessed in common by all matter, these elementary sub- stances possess peculiar attractions for each other, whi-cli are called chemical attractmis. By these attractions, or affinities, as they are called, they combine together, and form com])oimd bodies. OPERATIONS AND INSTRUMENTS USED IN CHEMISTRY. The great principle of all chemical operations which enable us to decompose certain bodies, and to compound others, is, that every substance has a pecidiar affinity or attraction for other substances, but that it has different degrees of attraction for different substances. This is called elective affinity or attraction. If some oil and some alkali be put together, they will unite and form soap. But if to this a little dilute sulphuric acid be added, the oil and alkali will be separated from each other again ; the alkali having a stronger attraction for the acid than it has for the oil, will leave the latter and join the acid. Dissolve some magnesia in nitric acid, and the solution will be transparent. Also dissolve some lime in water by letting it remain for some hours: the solution of lime in water will also USED IN CHEMISTRY. O be transparent. Pour them together, and imme- diately a turbid appearance will be presented, and a white powder will fall to the bottom. This powder will be found to be magnesia. The ex- planation is this : the nitric acid has a greater attraction for lime than it has for magnesia ; there- fore, it lets fall the latter and takes up the former. The substance thus thrown down is called a pre- cipitate, and the process \'&c?i\\Qd. precipitation. If all the bodies presented to each other are compounds, sometimes two new substances are formed. Thus, if solutions of nitrate of barytes and of sulphate of soda be mixed together, the former being composed of nitric acid and barytes, and the latter of sulphuric acid and soda, two new products will be obtained, viz. nitrate ot soda and sulphate of barytes. For the nitric acid will leave the barytes and join to tiie soda, and the sulphuric acid will give up the soda and seize the barytes. Tliis is called double elective affinity, as the former example was of single elective nffi^iity. When diiferent substances unite chemically, and form a compound, they always unite in the same proportion. Thus, water, which is composed of oxygen and hydrogen, always con- tains the same proportion of each ; that is, we do not find that in several specimens of water the pro- portions of oxygen and hydrogen vary. Also, if an acid and an alkali combine together, and thus form a certain salt, they always unite in the same proportion to form that salt ; however, they will sometimes combine in another proportion to form another salt j but when substances unite in more than one proportion, the second, third, &c. proportions are multiples or divisors of the first. This is one of the latest discoveries in chemistry, B O b OPERj^TlONS AND INSTRUMENTS and has given rise to the doctrine of definite proportions. Here it must be remarked that chemical com- bination and mechanical mixture are very different ; since, although bodies only combine in definite proportions, yet, they can be mixed together in all proportions. in general, before substances can be made to act cliemically on each other, one of them, at least, must be in a fluid state ; and, that solids may be acted on more easily, they are generally mechanically divided into small pieces, or reduced to a powder. By trituration^ pulverization, and levigation, is meant the reduction of solids into pov^ders of dif- ferent degrees of fineness. Brittle substances are reduced to powder by means of hammers, pestles and mortars, stones and mullers. Mortars and pestles are made either of metal, glass, porcelain, marble, agate, &c. according to the hardness and properties of the bodies to be pounded. Wedge- wood's ware affords a most excellent kind of mor- tar for most purposes, as it is very strong, and not liable to be acted upon by acids. Many bodies cannot be reduced to powder by the foregoing methods : such are fibrous substances, as wood, horns of animals, elastic gum, and mettles which flatten under tlie hammer ; for these, JileSy rasps, knives y and graters, are necessary. The separation of the finer parts of bodies from the coarser which may want farther pulverization, is performed by means of sifting or "djashing. A sieve for sifting generally consists of a cylin- drical band of thin wood, or metal, having silk, leather, hair, wire, &c. stretched across it. They are of diflerent degrees of fineness. USED IN CHEMISTRY. 7 Washing is used for procuring powders of an uniform fineness, much more accurately than by means of the sieve ; but it can only be used for such substances as are not acted upon by the fluid which is used. The powdered substance is mixed ■with water, or other convenient fluid : the liquor is allowed to settle for a few moments, and is then decanted off; the coarsest powder remains at the bottom of the vessel, and the finer passes over with the liquor. By repeated decantations in this manner, various sediments are obtained, of different degrees of fineness : the last, or that which re- mains longest suspended in the liquor, being the finest. Filtration is a finer species of sifting. It is sifting through the pores of paper, or flannel, or fine linen or sand, or pounded glass, or porous stones, and the like ; but it is used only for separ- ating fluids from solids, or gross particles that may happen to be suspended in them, and not chcr mically combined with the fluids. Thus salt water cannot be deprived of its salt by filtration j but muddy water will deposit its mud. No solid, even in the form of powder, will pass through the above- mentioned filtering substances : hence if water or other fluid, containing sand, insects, mud, &c. be placed in a bag or hollow vessel made of any of those substances, the sand, &c. will remain upon the filter, and the liquor will pass through, and may be received clear in a vessel under it. Unsized paper is a very convenient substance for making filters for chemical purposes. It is wrapped up in a conical form, and put into a glass funnel, which serves to strengthen the paper and support the weight of the fluid when poured into it. Decantatioti.iS often substituted, instead of fil- B 4 8 OPERATIONS AND INSTRUMENTS tration, for separating solid particles which are diffused through liquors. These are allowed to settle to the bottom, and the clear fluid is gently poured off. If the sediment be extremely light, and apt to mix again with the fluid, by the slightest motion, a syphon is used for drawing off the clear fluid. Limviation is the separation by means of water, or other fluid, of such substances as are soluble in it, from other substances that are not soluble in it. Thus, if a certain mineral consists of salt and sand, or salt and clay, &c. the given body being broken to powder, is placed in water, which will dissolve the salt, and keep it suspended, whilst the earthy matter falls to the bottom of the vessel, and, by means of filtration, may be separated from the fluid. Evaporation separates a fluid from a solid, or a more volatile fluid from another which is less volatile. Simple evaporation is used when the more vola- tile or fluid substance is not to be preserved. Various degrees of heat are employed for this pur- pose, according to the nature of the substances, it is performed in vessels of wood, glass, metal, porcelain, &c. Basons made of Wedcewood*s ware are very convenient, as they are not apt to break by sudden changes of heat. Small flasks of thin glass also : these are placed either over the naked fire, or in a vessel filled with sand, which is then called a sand-bath. This affords a more re- gular degree of heat, and renders the vessels less liable to be broken. When the fluid which is evaporated must be pre- served, then the operation is called distillation. Distillation is evaporating in close vessels, when USED IN CHEMISTRY. 9 we wish to separate two fluids of different degrees of volatility, and to preserve the most volatile, or both of them. The substance to be subjected to distillation is put into some vessel that will resist the action of heat, called a retort, an alembic, or a stilly having a beak or neck projecting from it, to which is attached another vessel, to receive the fluid that rises flrst, which is called the recipient, or receiver. The vessel that contains the liquor to be distilled is placed upon the fire, or in a sand- bath, or over a lamp : the heat causes the most volatile fluid to rise in the form of vapour, and to pass into the receiver, where it is again condensed by cold. This condensation is sometimes as- sisted by making the vapour pass through a tube which is immersed in a vessel containing cold water. A (Plate 1. fig. 1.), represents a retort used for distillation. It is a vessel, either of glass or baked earth, for containing the liquid to be distilled. When it has a small neck, a, with a stopple fitted to it, for introducing the materials through, it is called a tubulated retort. B is the receiver for con- densing the vapour which is raised, and into which the neck of the retort is inserted. The joining, b, is made air-tight by means of some substance ap- plied to it, called a lute. Various methods are used for supporting both the retort and receiver, according to the degree of heat employed in the process, and several other circumstances. When great heat is employed, earthen retorts are used, which are placed on or in the fire. When a less heat is wanted, glass retorts are generally employed, which must not not be placed imme- diately on the fire, unless they are coated over with a composition of clay and sand, which is 10 OPERATIONS AND INSTRUMENTS sometimes done. Glass retorts are generally placed in a sand-bath, or suspended over a lamp, for which Argand's lamp is the best. The re- ceiver is placed upon some stand convenient for the purpose, with a ring made of hay under it, or some such contrivance, to keep it steady. A (Fig. 2.), is a vessel called a mattrass, for the same purpose, having a vessel, B, called an alembic, fitted to the head. The liquid raised by heat into the state of vapour, is condensed in the alembic, and falls into a groove all round its inside, from whence it runs out by the spout, C, into the re- ceiver, D. Fig. 3. are conical tubes that fit into another, for lengthening the necks of retorts, &c. to con- nect them with the receivers at any distance: they are called adopters. Fig. 4. are phials with bent glass tubes fitted in them, for disengaging gases, and similar experi- ments : they were used by Priestley, and are hence called Priestleij^s bottles, and sometimes proofs : they are either tubulated or plain. A (Fig. 5.), represents a common still. It is a large vessel of copper, into which the materials to be distilled are put. The still is built up in brick-work, which covers it up to the neck; the fire is applied underneath, and runs round it in a spiral manner. B is the Jiead of the still. This head is connected with the ivorm, which is a spiral tube, immersed in a vessel of cold water, called the refrigeratory, or cooling tube, C. The liquor be- ing condensed in its passage through the worm, runs out at the cock, D, into the vessel placed there to receive it. This is the construction of the common still for distilling spirituous liquors ; but a very great im- USED IN CHEMISTRY. 11 provement has been made upon this instrument, in Scotland, within these few years. This improved apparatus is known by the name of the Scotch still, a section of which is represented, Fig. 6. The principle of the improvement consists in exposing a great quantity of the surface of the fluid to the action of the fire, and affording a more ready means for the escape of the vapour or gas. A, is the body of the still, made very shallow and concave at the bottom, in order that the fire may act better upon it ; bb^ are a number of tubes opening into the still, and communicating with the neck of the still B, in order to convey the vapour off as soon as it is formed ; cc, is a cover that shuts down over the pipes and top of tlie still, to keep it warm, by preventing the loss of heat which would be occasioned by the contact of the cold air. This is effected by the quantity of air that is confined between the cover and tlie top of the still ; for it is a fact which is now well known, that confined air is a non-conductor of heat. In general, the heads of stills are kept warm by laying blankets upon them, at least when this is attended to, as it ought always to be ; but this metallic covering, by sur- rounding the still with a quantity of confined air, answers the purpose still better. When the materials which are evaporated con- crete in a solid form, within the neck of the dis- tilling vessels, then the distillation is more properly called sublimation. By the above means, one fluid may be separated from other materials; but it often happens, that in distillation the substances which are subjected to this process have a chemical action upon each other ; new combinations take place, and perma- IS PNEUMAT0-CHE31ICAL APPARATUS. nently elastic fluids or gases are disengaged, which are required to be preserved and examined. For tliis purpose, a very useful apparatus is employed, called the PNEUMATO-CHEMICAL APPARATUS. Fig. 7, represents an improved pneumato-chemi- cal apparatus and lamp-furnace connected with it. A, is a vessel filled with water. In this vessel a shelf is placed, so as to be a little under the surface of the fluid, having several holes bored through it, to which small funnels are attached underneath. The glass air-jar, or receiver, B, which is to re- ceive and contain the gas, is filled with water, and being inverted wdth its mouth under water, it is raised up gently till its mouth is nearly out of the water, but not quite ; and it is then placed upon the shelf over one of the holes. The receiver will remain full of water, w^iich is kept up by the pressure of the atmosphere upon the principle of the barometer described under pneumatics. The materials from w^iich the gas is to be dis- engaged, are now to be put into a glass retort, C, which is put through, and suspended in one of the rings of the lamp-furnace, D. An improved Ar- gand's lamp, £, having teo co7icentric wic/cs,* afl^brds a much greater degree of heat than the common Argand's lamp, wdiich has only a single circular Xiick; this is placed upon the shelf, F. * This lamp with two concentric tvicks was first contrived by the editor some years ago, and is extremely useful m some chemical operations, as it gives a much greater heat than the common Argand's lump with one circular wick. PNEUMATO-CHEMICAL APPARATUS. 13 The shelf, with the lamp and the ring having the retort in it, are now to be adjusted by moving them up or down, until the lamp is at a convenient height below the retort, the neck of whicli rests upon the edge of the cistern, and the end of its neck opens in the funnel under the jar standing upon the shelf. The lamp must now be lighted, and as soon as the substances in the retort act upon each other sufficiently, the gas will begin to be dis- engaged, and will ascend through the hole in the shelf into the vessel, B, and displace the water witli which it had been filled. When all the water is displaced, the receiver is full of the gas which was disengaged from the retort, and may be preserved in it by keeping its mouth always under the water in the cistern. This gas may be transferred from the vessel, B, into any other vessel, in the following manner : fill the vessel into which the gas is to be transferred, with the fluid in the trough, and place it on the shelf as before directed, over one of the holes. -Then take the vessel, B, and keeping its mouth still under the fluid, bring it under the hole on which .the vessel is placed, then depressing its bottom, and elevating its mouth, so as to bring it more to a horizontal position, the gas in it will escape and rise up through the hole on which the other vessel has been placed, and will fill it by displacing the fluid. In this manner any gas may be formed, or transferred from one vessel to another. The cistern for the water may be made of wood, in the manner of a tub, and hooped round, which may or may not be painted inside and out. But it will be much more elegant if made of sheet-iron, tinned, and japanned of a brown or chocolate co- lour. The ornaments, if any, may be of brass, or 14 PNEUMATO-CHEMICAL APPARATUS. gilt. The best material for the lamp-furnace is brass lackered, and the lamp should be of tin ja- panned. The apparatus constructed in this man- ner has an extremely elegant appearance, and is found to answer perfectly well for a variety of che- mical operations. When the gas to be procured is absorbable by water, quicksilver is used instead of water ; and, as it is very expensive, a smaller vessel is neces- sary, which must be made of some material not acted upon by quicksilver, as wood or stone ; and it must be sufficiently strong to resist the great weight and pressure of the quicksilver. It is usually cut out of a solid block of wood, or marble, or made very strong of mahogany, and varnished over, to make it perfectly tight. A small glass vessel, capable of containing an ounce measure, is used for measuring gases ; for if this phial be successively filled, and inverted un- der a large jar, we may thereby throw into that jar any required quantity of an elastic fluid, or as many measures of one elastic fluid, and as many of ano- ther, as we please. G (Fig. 7.), represents a tube for receiving a mixture of gases that are to be exploded by the electric spark. It is a very strong glass tube, closed at one end, and having a scale upon it, cut with a diamond. Near the closed end two wires pass through the glass, and almost touch each other, but not quite ; they are cemented in, so as to make the holes air-tight. When this graduated tube is filled with the fluid in the trough, and inverted upon the shelf, certain measures of the gases to be exploded are introduced in the usual way. If thus the interval between the two wires be made a part of the electric circuit, by fastening chains con- PNEUMATO-CIIEMICAL APPARATUS. 15 nected with a Leyden phial to the rings of the wires, the spark will pass through the interrupted space between the two wires, and explode the gases. These instruments are called ea:ploding tubes. In compound distillations, or when a decompo- sition of the materials subjected to this process takes place, and gases are formed, some of which are absorbable by water, some by alkalis, and others are not capable of being absorbed at all, it is often required to preserve separate the several new substances procured. The apparatus invented by Lavoisier for this purpose is the most con- venient. A (Plate 2. fig. 1.), is a glass retort, the beak of which is adjusted to a double tubulated balloon, or receiver, B. To the upper tubulure of tliis re- ceiver is fitted a glass tube, C, the other extremity of which is conveyed into the Hquor contained in the glass vessel, D : with this vessel, D, which has three tubulures, are connected two or three other similar vessels, by means of glass tubes fitted into their tubulures, and to the last tubulure of the range of vessels is adapted a glass tube which is conveyed under a receiver placed upon the shelf of the pneumatic cistern. Water is put into the first of these vessels, caustic potash into the next, or such other substances as are necessary for ab- sorbing the gases, and the joinings are w^ell luted. Sometimes it will happen that a re-absorption of gas takes place; and in this case, that there may be no danger of the water in the pneumatic tub entering rapidly into the vessels through the tube, E, a capillary tube is adapted to the middle tubu- lure of each vessel, which goes into the liquid con- l(i PNEUMATO-CHEMICAL APPARATUS. tained in it. If absorption takes place, either in the retort or vessels, the external air enters through these tubes, to fill the vacuum which is occasioned by the absorption, and no water comes into the vessels. Large vessels for containing air, and expelling any given quantity, are called gazometers. They are of various constructions ; one of the best is the following : AB (fig. 2.), is a cylindrical vessel of tin, japanned, nearly filled with water, and having a tube, C, in the middle, open at top, and branching, to communicate with the cock, D. Within this vessel there is another cylindrical vessel, generally of glass, of smaller size, F, open at bottom, which is inverted and suspended by the lines e e, whicli go over the pullies j^^^j^ and have weights^ o", attached to them, to balance the vessel, F. While the cock D remains shut, if the vessel F be pressed downwards, the air included within it will remain in the same situation, on the principle of the div- ing-bell ; but if the cock be opened, and the vessel, F, be pressed down, the air included within it will escape through the cock, and if a blow-pipe be at- tached to this cock, a stream of the gas may be thrown upon lighted charcoal, or any other body. By means of the graduated rod, //, also, the quan- tity thrown out is exactly ascertained : this rod is so divided as to express the contents of the inner vessel in cubic feet, &c. This instrument also an- swers for breathing any of the gases, by applying a mouth-piece to the cock. To render it more portable, the w^eights g gy are sometimes included in the uprights i i, which aie hollow, and wide enough to receive them. Sometimes, also, there is another branch from the bottom of the pipe, m PNEUMATO CHEMICAL APPARATUS. 17 the middle, directed to the side of the outer cy- Hnder, and coming upwards by the side to the top, where there is another cock attached. For soliitiony and dissoluiionSy and for crystal- lizing sails, vessels of glass or earthenware are used. The melting, or causing any body to pass from the solid to the liquid state, by the action of fire, is caWed Jiisi on. The fusion of metallic substances requires vessels sufficiently strong to resist the fire. Those vessels are mostly, if not always, made of earthen-ware, or porcelain, or a mixture of clay and powder of black-lead. They are called cru- cibleSy and are generally of the forms represented Tig. 3. Sometimes these vessels have covers made of earthen-ware ; but sometimes the fused metal must be exposed to a current of air : in that case, the crucibles are broad and shallow, as at Fig. 4. these are called cupels, and they are formed of calcined bones, mixed with a small quantity of clay, or of a mixture of clay and black-lead pow- der. But the cupels must not be placed in a closed furnace, or be surrounded by coals ; for, in that case, the required current of air could not have access to the fused metal. They are, there- fore, placed under a sort of oven of earthen-ware, which is called a miiffle, as represented, Fig. 5, which, with the included cupel, is exposed to the heat of a furnace. The various degrees of heat which are required for the performance of chemical operations render a variety of fire-places, ov furnaces, necessary for a chemist. Those furnaces are either open at top, or they are covered with what is called a dome, and have a chimney, or tube, to carry oft' the heated VOL. 11, c IS PNEUMATO CHEMICAL APPARATUS. air, smoke, &c. They are sometimes supplied with air from the natural action of the fire, which rare- fies the air about the ignited fuel ; and the rarefied air becoming specifically ligliter, ascends into the chimney, whilst the colder, and consequently hea- vier air, is forced by the atmosphere to enter at the lower part of the furnace. Some furnaces are sup- plied with air by means of bellows ; and those are applied for forging iron, or for reducing metals from the ore, which is called smelting. Hence the furnaces derive their various names, and are called simple^ or open furnaces^ reverheratory furnaces, tvindy or air furnaces, blast furnaces, forges^ smelt' ing furnaces, <§t. A very useful kind of furnace, for many pur- poses, is that invented by Dr. Black, of Edinburgh, represented in Fig. 6. It consists of a cylindrical or elliptical body of sheet-iron, coated within with a mixture of loam and clay. The aperture A at top is closed occasionally with an iron saucer full of sand, which forms a sand-bath ; B is the door of the fire-place, and C is the ash-pit register, which slides so as to admit more or less air. D is an iron tube which goes into the chimney of the room, to carry off the smoke. Blow-pipes are used for directing the flame of a candle or lamp against any bit of ore or other sub- stance required to be examined. They ought to have a bulb upon the middle of their stem, to contain the moisture that is formed from the breath. See Fig. 7- The blow-pipe contrived by Dr. Black, of a conical form, represented in Fig. 8., is very con- venient; a, is the nozzle. When a solid substance, in powder or otherwise. NOMENCLATURE OF CHEMISTRY. 19 is left for a certain time in a fluid, and the mixture - is kept exposed to a slow degree of heat, the pro* cess is called digestmi. When one substance, which has an affinity to another, is mixed with as much of that other substance as its affinity will enable it to hold in combination, then the former substance is said to be saturated^ or the mixture to have attained the point of saturation. If the mixture contain a greater proportion of either substance, then that mixture is said to contain an excess of it, or to be surcharged. The same thing must be understood of the compounds of more than two substances. The dry way of performing chemical operations is when strong degrees of lieat are used, and the humid way is when fluid solvents are used. Combustion is when a body is burned with the assistance of respirable air. Deflagration is when the combustion is attended with little explosions or cracklings. Detonation is a pretty loud report. OF THE NOMENCLATURE OF CHEMISTRY. One of the chief improvements which have been made in modern chemistry has been the invention of names for the compound substances, which ex- , press the elements which enter into their compo- sition, as well as the proportions in which those elements are combined. By this the memory is much assisted, in recollecting the nature of the great variety of substances, and to which the an- cient chemists gave arbitrary and frequently unap- propriate appellations. When the simple substances, oxygen, chlorine, and iodine, which are supporters of combustion^ c ^ 20 NOMENCLATURE OF CHEMISTRY. enter into combination with each other, or with the other elementary bodies, they form combinations that are divided into two classes. In one class the substances are ?iotacid, and their names have their termination in ide, as oa:ide of chlorine, oJ^ide of nitrogen, chloride of sulphur, iodide of iron, &c. \VTien these supporters of combustion enter into combination with a body in more than one propor- tion forming oxides, the terminations, ous and ic, are employed. Thus nitrogen, with the smallest proportion of oxygen, forms the 7iitroiis oxide ; and, with a large proportion, it makes the nitric oxide. When the metals combine with oxygen in one proportion only, the compounds are called simply oxides of the metals. Formerly the compound of a metal with oxygen was called a caliv, as the calx of tin, now the oxide of tin; and the process of combining a metal with oxygen was called calcina- tiojiy now oaigenation. Sometimes oxygen can enter into combination with a metal so as to form oxides in more than one proportion, and then a syllable is prefixed to the term oxide to denote that proportion ; the smallest quantity of oxygen forms the protoj:ide of the me- tal, the second quantity of oxygen makes the deutoaide, and the third, the tritodide ; antl, far- ther, the term peroxide is applied to that oxide of the metal that contains the greatest proportion of oxygen with which it is known to combine. The same syllables are prefixed to chlorides and io- dides. An oxide combined with water is called a hydrat. When an acid is formed by the union of a simple body with oxygen, it derives its name from that NOMENCLATURE OF CHEMISTRY. SI body ; as the sulphuric acid, which is formed of sulphur and oxygen ; the carbonic acid, which is formed of carbon and oxygen. Sometimes oxygen will unite in several propor- tions with a simple body, so as to form different acids ; then the acid which is the most oxygen- ated, has its termination in ic ; and that which is the least oxygenated, in ous. Thus sulphur forms two acids ; when it unites to the least proportion of oxygen capable of making an acid, it forms the sulphureous acidf and with a larger proportion of oxygen it makes the sulphuric acid. Hydrogen, like oxygen, combines with a certain number of simple substances, and with them forms compounds, some of which are acid, and others are not. To distinguish the acids Jbrmed hy hy- drogen, from those formed by oxygen, the former are designated by the word hydro^ as the hydro- chloric acid, hydro^uoric acid. Products not acid, Jbrmed by hydrogen and a simple substance, if solid, are called hydruret : if gaseous, the name of the simple substance termin- ated in ed is prefixed to that of hydrogen gas ; as carburettedy or yhosphoretted hydrogen gas. When chlorine, sulphur, phosphorus, and carbon, unite to each other, or to another simple body, the compound has also its termination in uret, as chloruret of phosphorus, and of iron, sulphuret of iodine, phosphuret of lime, carburet of iron, &c. Neutral salts, or substances produced by the union of acids and alkalis, are denominated from the names of the acids and alkalis of which they are composed. The salts produced by the acid whose names end in ous have their terminations in ite ; thus sulphurous acid and potash form sulphite of potash : salts produced by acids ending in ic have c 3 ^ CALORIC. their termination in ate : thus sulphuric acid and potash form sulphate of potash, and so of all the rest. The terms, bi-sulphuret, bi-phosphoret, bi-sul- phate, &c. denote that these compounds contain twice as much sulphur, phospliorus, sulphuric acid, &c. as the sulphuret, phosphoret, sulphate, &c. CALORIC. C4.L0RIC, or the matter of heat, is generally con- sidered as a peculiar elementary substance. It cannot be ascertained to have any weight, a body when heated not being heavier than before. A distinction is made between caloy^ic, or the njiatter of heat, and the word heat when considered as a sensation. The sensation of heat, or sensible heati is the eifect produced upon our organs by the motion of caloric disengaged from the surrounding bodies. Whei> we touch a cold substance, the caloric^ which e?cists in unequal quantities in dif- ferent bodies, but which always tends to be in equi- librio in all bodies, passes out of the hand into the body, which feels cold, because at the time there w^s less free caloric in the substance than in the hand ; and as we have lost heat, we feel the sensa- tion of cold : cold being, not any thing positive, but merely the want of heat. The contrary happens "vyhen we touch a warm body j the caloric then in passing into the hand, gives the sensation of warmth. If the hand and the body touched be of the same temperature, or very nearly so, we re- ceive no impression either of heat or cold, because there is no motion of caloric. l^yfree caloric, we mean that which is not com- bined with any other body. But, as caloric has a CALORIC. ^S very strong tendency to combination, we are not able to procure it in that state. Combhied caloric is that which is fixed in bodies by affinity or elective attraction, so as to form part of their constitution. By the expression spe- cific caloric of bodies, we understand the respective quantities of caloric requisite for raising bodies of the same weight to an equal degree of temperature. This proportional quantity of caloric is thought to depend upon the distance between the consti- tuent particles of bodies, and their greater or less degrees of cohesion ; and this distance, or rather the space or void resulting from it, is called the ca- pacify of bodies for heat. Heat has the property of expanding bodies, or increasing their bulk. This may be observed by fitting a piece of iron to an iron ring so as just to fill it : then if the iron be heated in the fire, it wdll be found that it has become too large to pass through the ring ; but when cooled, it contracts to the same size as before. Some metals will ex- pand more than others. It is supposed that the caloric forces itself be- tween the particles of bodies so as to separate them. In acting thus, it is in direct opposition to the attraction of cohesion, which keeps them together. Fluids also expand by heat. Put water into a very small glass tube with a bulb, and apply heat to the bulb ; the water will be seen to expand and fill more of the tube : as it cools, it will contract again. Gases also increase in volume, by increase of temperature. Tie the neck of a bladder tight ; when it is almost empty, lay it before the fire ; the included air will expand, and the bladder will swell c 4 24t . "- CALORIC. and appear full, but will return to its former state by withdrawing it from the fire. From this pro- perty of matter in expanding by heat, the thermO" meter becomes a measure of the heat in bodies. Every body, therefore, whether solid, liquid, or gaseous, is augmented in all its dimensions, by an increase of sensible heat : and on the contrary, all bodies contract by an abstraction of caloric. We are still very far from being able to produce the degree of absolute cold, or total deprivation of heat ; hence, we are incapable of causing the ulti- mate particles of bodies to touch each other. It may be supposed, since the particles of bodies are thus constantly impelled by heat to separate from each other, that they would have no con- nexion between themselves ; and that, of conse- quence, there could be no solid body, unless the particles were held together by some power which tended to unite them ; this power is the attraction of cohesion. Thus, the particles of all bodies may be considered as subject to the action of two opposite powers, repulsion and attraction^ between which they remain in equilibrio. So long as the attractive force remains strongest, the body must continue in a state of solidity ; but if, on the con- trary, heat has so far removed these particles from each other, as to place them beyond the sphere of attraction, they lose the cohesion they had before with each other, and the body ceases to be solid. Water gives us a regular and constant example of these facts. Whilst below 32° it remains solid, and is called ice. Above that degree of temper- ature, its particles being no longer held together by reciprocal attraction, it becomes liquid ; and when we raise its temperature above 212**, its particles giving way to repulsion caused by the heat, assume \ CALORIC. 25 the state of vapour or gas^ and the water is changed into an aeriform fluid. The same may be affirmed of all bodies in na- ture. They are either solid, or liquid, or in the state of elastic aeriform vapour, according to the proportion which takes place between the attrac- tive force inherent in their particles, and the re- pulsive power of heat acting on them ; or, what amounts to the same thing, in proportion to the degrees of heat to which they are exposed. But were there no other cause affecting the solidity of bodies except the powers of attraction and repul- sion, they would become liquid at an indivisible degree of the thermometer, and would almost in- stantaneously pass from the solid state of aggreg- ation to that of aeriform elasticity. Thus water, for instance, at the very instant when it ceases to be ice, would begin to boil, and would be trans- formed into an aeriform fluid, having its particles scattered indefinitely through the surrounding space. That this does not happen, must depend upon the action of some third power. The pres- sure of the atmosphere prevents this separation, and causes the water to remain in the liquid state until raised to the temperature indicated by SIS'^ ; the quantities of caloric, which it receives in the lower temperatures, being insufficient to overcome the pressure of the atmosphere. Whence it appears, that, without this atmos- pheric pressure, we should not have any permanent liquid, and should only see bodies in that state in the very instant of melting ; for the smallest addi- tion of caloric would then instantly separate the particles, and dissipate them through the surround ing medium. Besides, without this atmospheric pressure, we should not even have any proper aeri- 96 CALORIC. form fluids ; because the force of attraction would be overcome by the repulsive power of caloric ; and the particles of bodies would separate themselves indefinitely, having nothing to give limits to their expansion, unless their own gravity might collect them together so as to form an atmosphere. It may be admitted, therefore, as a general prin- ciple, that almost every body in nature is suscep- tible of three several states of existence, soUd^ liquid, and aeriform ; and that these states depend upon the quantity of caloric combined with the body. The elastic aeriform fluids are expressed by the generic name of gas ; and in each species of gas, a distinction is made between the caloric, which, in some measure, serves the purpose of a solvent, and the substance which, in combination with the caloric, forms the base of the gas. Thus water, united to a sufficient quantity of caloric, is called aqueous gas ; ammoniac saturated with caloric, is called ainmoniacal gas, he. Caloric, when free, appears to move in the form of rays, and to be capable of being reflected in the same manner as light. The calorific part of the solar rays, or those which occasion heat, are con- densed by a lens, ora mirror, as well as those which produce light; and the rays of heat from any burn- ing body, or even of a body heated, although not in a state of combustion, are thrown off in a radiat- ing manner. If two polished metallic mirrors be placed opposite to each other, at several feet dis- tance, and if a pan of burning coals, or a heated piece of iron, be held in the focus of one of them, a thermometer placed in the focus of the opposite one, will be immediately affected as if it had been CALORIC. %J held close to the heated matter ; and this will be the case, even if the heated body is not luminous or incandescent, as hot water, for instance; so that the invisible rays of heat also are reflected like those of light. The chief part of the heat received from a common fire is in the form of radiant heat ; and whatever kind of construction will most promote the reflection of radiant heat into the room, will be the most advantageous form of the chimney. It is upon this principle that the grates introduced into common use by Count Rumford are so much pre- ferable to all others. The effect of the solar rays upon bodies differs much according to their colour ; black and dark coloured bodies are more heated than white ones ; the latter throwing off" the rays, while the former absorb them. For this reason, black clothes are more heated by the sun than white ones. Polished surfaces, also, which reflect best, do not absorb so much heat as rough surfaces. The boiling or ebullition of liquids is a phenome- non which depends upon the liquid being converted into vapour by a certain degree of temperature ; consequently, those liquids which assume the va- porous or aeriform state at the lowest temperature are most easily made to boil. The ebullition, or the noise and motion of the liquid in boiling, is occasioned by small quantities of vapour being formed at the bottom of the vessel, which rise by their lightness in a globular form, and break at the surface. The ebullition of liquids is easier in pro- portion as the pressure to which they are subjected is less ; thus water, which boils only at 212° Fahr. in the air, will boil with a much less degree of heat in an exhausted receiver of the air pump ; and it 28 CALORIC, will also boil with much less heat on lofty moun- tains than in the valleys. Bodies differ very much with respect to the fa- cility with which heat passes through them. Those which transmit caloric easily are called conductors of caloric ; and, according to the power of doing so, they are termed good or bad conductors. Those which do not transmit heat at all, or with great difficulty, are called non-conduct07^s. How- ever, it should be observed, that, perhaps, no substances are absolutely non-conductors ; but liquids and gases admit the passage of caloric through them with such great difficulty, that, for practical purposes, this division is found useful. Liquids carry heat chiefly by transportation ; the part of the liquid that is heated rises to the sur- face, and gives place to another which is warmed in its turn, and so on until the whole has been heated. Many very important applications of this prin- ciple have been made by Count Rumford to oeco- nomical purposes. He showed that a stratum of confined air was one of the best modes of prevent- ing the escape of heat. The best conductors of heat are metals, and the best non-conductors are fluids and porous sub- stances. Charcoal is an excellent non-conductor. Heat may be excited by mere friction ; and this, probably, was the earliest mode of obtaining it to procure fire. It is still practised among uncivilized nations. For this purpose they take two pieces of dry wood, one about eight or nine inches long, and the other piece quite flat. They cut a blunt point upon the first, and, pressing it upon the other, they whirl it round very quickly, holding it CALORIC. 29 oetween both their hands, as we do a chocolate mill. In a few minutes the wood takes fire. If the irons of the axle of a coach-wheel be left with- out grease or oil, they will become so hot as to set fire to the wheels j and accidents of this kind some- times happen. It is no uncommon practice in the country, for a blacksmith to hammer a piece of iron till it be- comes red hot, as a substitute for a tinder-box. The heat excited by the boring of a cannon is suf- ficient to cause water to boil. Heat is also produced by collision ; when a piece of hardened steel is struck with a flint, some particles of the metal are broken off, and so violent is the heat produced by the stroke, that they are rendered red hot, and melted. If the fragments of steel be caught upon a piece of white paper and examined with a microscope, they will be found to be spherules, and highly polished, showing that they had been fluid. No heat seems to follow from the percussion of liquids in soft bodies. The instruments for measuring heat by the ex- pansion of bodies are, thermometers for fluids, and pyrometers for solids. A thermometer is a hollow tube of glass, her- metically sealed, and blown at one end into the shape of a hollow globe, or bulb. The bulb and part of the tube are filled with mercury, which is the only fluid that expands equally. AVhen we im- merse the bulb of the thermometer in a hot fluid, the mercury expands, and, of course, rises in the tube; but when we plunge it into a cold body, the mercury contracts, and, of course, falls in the tube. The rising of the mercury, therefore, indicates an increase of heat ; its falling, a diminution of heat. 30 cALonic. To facilitate the observation, the tube is divided into a number of equal parts, called degrees, or there is a divided scale attached to it. This scale is graduated in different manners by different nations : Fahrenheit's scale is that al- ways used in this country. The standard points are obtained by freezing and boiling water, degrees of heat which are con- stantly the same in nature. The heat at which the mercury stands, when immersed in each, being marked, the distance between them is divided into 180 parts, and 32 parts of the same size are con- tinued downwards, so that 32° shows the heat of freezing water, and 212° that of boiling water. AVater cannot be made hotter than this in open ves- sels, because it then becomes converted into steamy or aqueous gas. The mercurial thermometer, it is evident, cannot measure degrees of heat above that of boiling mer- cury, nor below that of freezing mercury ; the former is 600°, and the latter 40° below 0 of Fah- renheit's scale. For greater degrees of cold, thermometers of spirits of wine, or essential oil, are used ; and to measure those higher degrees of heat to which the thermometer cannot be applied, pyrometers are em- ployed. An instrument of this kind was invented by the late Mr. Wedgewood. It consists of two pieces of brass, fixed so as to form an angle, having the legs divided into equal parts. Pieces of baked clay are prepared for this scale, so as to fit the brass at a certain place. If then the piece of clay be exposed to the heat required to be ex- amined, it will contract in its dimensions, and, when again applied to the brass scale, it will be seen how much it has contracted. By this the in- CALORIC. 31 tensity of the heat is ascertained, for the clay of which these pieces are prepared, has the property of contracting regularly, according to the degree of heat. This is an exception to the general law of bodies expanding by heat ; the expansion of melted metal in the act of cooling is another, as likewise the ex- pansion of water in the act of freezing. The greatest degrees of heat which can be raised have been produced by concentrating the solar rays with a mirror or lens, or by supplying a blow- pipe with oxygen gas ; or, what is still more power- ful, by a mixture of oxygen and hydrogen. This last method has been but lately employed, and pro- duces a far greater degree of heat than any other. The mixture is itself of an explosive nature, and, therefore, without proper precaution, exceedingly dangerous. The greatest degree of cold known to have been produced has been obtained by mixing snow with certain salts. The best salt for this purpose is muriat of lime. If this be mixed with dry light snow, and stirred well together, the cold produced will be so intense as to freeze mercury in a few minutes. Salt and snow also produce a great degree of cold. Evaporation, likewise, produces cold. The me- thod of making ice artiiicialiy in the East Indies depends upon this principle. The ice-makers at Benares dig pits in large open plains, the bottom of which they strew with sugar-canes, or dried stems of maize, or Indian corn. Upon this bed they place a number of unglazed pans, made of so porous an earth that the water oozes through their substance. These pans are filled towards evening, in the winter season, with water v.'hich has been boiled, and are left in that situation till morning, S^ CALORIC. when more or less ice is found in them, according to the temperature of the air ; there being more formed in dry and warm weather than in cloudy weather, though it may be colder to the human body. Every thing in this operation is calculated to produce cold by evaporation ; the beds on which the pans are placed suffer the air to have a free passage to their bottoms, and the pans, constantly oozing out water to their external surface, are cooled by the evaporation of it. In Spain, they use a kind of earthen jars called buxaros, the earth of which is so porous, being only half baked, that the outside is kept moist by the water which filters through it ; and, though placed in the sun, the water in the jar becomes as cold as ice. It is a common practice in China, to cool wine, or other liquors, by wrapping a wet cloth round the bottle, and lianging it up in the sun. The water in the cloth evaporates, and thus cold is pro- duced. Ice may be produced, at any time, by the eva- poration of ether. Take a thin glass tube, four or five inches long, and about two or three eighths of an inch in diameter, and a two-ounce bottle of ether, having a tube drawn to a point, fitted to its neck. Pom- some water into the glass tube, and let a stream of ether fall upon that part of it containing the w^ater, which, by that means, will be converted into ice in a few minutes. If a thin spiral wire be introduced into the tube before the water is poured in, the ice will adhere to it, and may be drawn out. 33 LIGHT. Under Optics, the mechanical properties of light were considered. Light has considerable influence on chemical operations, but little is known of its real nature. Most generally it is considered as a certain simple substance, of which the chief source is the sun ; and it is also disengaged during the processes of combustion. The most delicate experiments have been insti- tuted for the purpose of discovering whether it has weight, but without success ; on which account it is reckoned among the imponderable bodies. - There appears to be an intimate connexion be- tween light and heat, and they are frequently given out together. But although they are both always found in the sun's rays, yet from them they may be obtained separately, the iusisible rays of heat being more refrangibible than those of light : see vol. i. Light is capable of entering in union with many substances, and of being again separated from them. This is the case in the substance called pyrophorus, which is made by exposing to a red heat in a crucible for some time, a mixture of pounded oyster shells and sulphur. If this sub- stance be then carried into the light for a few seconds, it will imbibe so much that it will become luminous in the dark by again giving out this light. Various kinds of meat, but particularly fish when they are beginning to putrefy, also rotten wood, sea-weeds, and some insects, as the glow- worm and lanthorn fly, have the property of shining in the dark. VOL. II. D 34 LIGHT. The effect of light upon vegetation is well known. Many flowers follow the course of the sun, and most flowers turn themselves more or less towards the light. Plants that grow in darkness are pale and without colour, and when this is the case they are said to be etiolated, or blanched. Gardeners avail themselves of this fact to render some vegetables, as celery and endive, white and tender. The more plants are exposed to the light, the more colour they acquire. Vegetables are not only indebted to light for their colour, but their taste and odour are derived from the same source. From this it happens, that hot climates are the native countries of perfumes, odori- ferous fruits, and aromatic resins. The action of light on the organs of vegetables causes them to pour out streams of oxygen gas from the surfaces of their leaves, while exposed to the sun, whereas, on the contrai'y, when in the dark, they emit air of a noxious quality. Animal life seems also to be no less influenced by light. Birds that inhabit tropical countries have much brighter plumage than those of the north. Animals in general seem to droop when deprived of light ; and no doubt it is \Qry essential to the health of human beings. The colour of metallic oxides is changed by the action of light : the yellow oxide of tungsten be- comes blue by exposure to hght ; the white salts of silver become black, and green precipitate of iron becomes red. Some oxides of metals lose w^eight by exposure to light, as the red oxide of mercury ; others lose their oxygen entirely, or become reduced, as the oxide of gold. Light, tlien, has the property of separating oxygen from several of the oxides. ELECTRICITY. 35 Some substances when heated to a certain de- gree become luminous ; iron, for instance ; and this is what is called a red heat. If bodies heated to redness be introduced into a gas, it does not become visible, and hence it has been concluded that gas is not capable of being made luminous : but it is now considered that flame is hydrogen gas in a luminous state. Light is also produced by percussion ; as in the case of a flint and steel. The spark produced in this case is owing to the flint breaking off a small fragment of the steel, which is thus rendered red hot, and burns diu'ing its passage through the air. But two pieces of quartz struck smartly toge- ther also give out light, although here there can be no combustion. Instruments for measuring the degree or inten- sity of light are called photometers, ELECTRICITY. Electricity and galvanism have been already treated of in the first volume. The electric fluid is now considered as a chemical agent of great importance, exciting a powerful influence in the decomposition of bodies. The connexion between electricity and chemical decomposition was first shown by Sir Humphry Davy, to whom the world is indebted for so many brilliant discoveries. There is still, however, great uncertainty and various opinions with respect to the real nature of this influence, which is usually classed among the imponderable elementary bodies. D 2 Si) OXYGEN. Oxygen is an elementary body that cannot be procured in a separate or free state, that is, it cannot be detached from tlie other bodies with which it is always combined. Oxygen gas is so called from two Greek words, signifying the generator of acids, because it was considered by Lavoisier as the only acidifying principle. It has been called also piu^e or vital air. About one fourth of the atmosphere consists of this gas, and it is essential to respiration and animal life. It is the most powerful and general supporter of combustion ; and by its union with other bodies^ it forms most of the acids. Oxygen gas may be easily procured by several processes. 1. It is obtained in the greatest purity from oxy-muriate of potash. Put some of this salt into a small glass retort, place the neck under the shelf of the pneumatic trough, and apply the heat of a lamp to the retort. The salts will soon melt and boil, when oxygen gas will come over in great abundance. Q.. Black oxide of manganese is usually employed for furnishing this gas, as it affords it at a cheaper rate. Procure an iron retort made for the purpose, fill it with the oxide, fit a conducting tube to it, and place the retort between the bars of a grate which contains a good fire. Keep up the heat until the retort becomes red hot, and the gas will be received in the pneumatic apparatus. Or it may be made from oxide of manganese, put into a ^lass retort, with half its weight of strong sulphuric OXYGEN. 37 acid. It may be likewise obtained in great quan- tity from nitrat of potass (salt petre) in an earthen retort exposed to a strong fire ; also from the red oxide of lead, heated with or without sulphuric acid. Having procured a sufficient quantity of this gas in separate vessels, its properties may be easily examined. It will be found that water does not absorb it ; for if some of it be agitated in a small vial half filled with water, and again immersed into the trough, it will not be diminished in quantity ; nor will the water rise in an inverted vessel of this gas, if left on the shelf of the trough for a day. Oxygen gas is eminently calculated to support the combustion of bodies. Plunge a lighted taper fixed to an iron wire, or a lighted splinter of wood, and the combustion will proceed with a splendour much encreased. The flame of a lamp urged by a stream of oxygen gas, - instead of common air, excites a heat more intense than the hottest furnace. Even the metals Which are not easily combustible in common air burn in oxygen gas with great readi- ness. Iron or steel wire burns in a very striking manner. It should be kindled by having a small bit of w^ood fastened to the point ; the combustion of this will communicate to the steel wire, which will continue to burn. The fused drops of iron that fall down, when examined, will be found to be no longer malleable, but brittle and converted into the oxide of iron. The same change will take place when the other metals are burnt in this gas. If a piece of charcoal, fixed to an iron wire, be lighted by a blow pipe, and put into ajar of oxygen gas, it will burn with a brilliant light, and throw D 3 38 NITROGEN. out numerous sparks, exhibiting a very beautiful appearance. Here the combustion pi'oduces a combination of" the oxygen with the carbon of the charcoal, and the result is carbonic acid. A small bit of phosphorus, put into a copper spoon, burns in this gas with a light intensely bright. It is necessary to inform the young prac- titioner, that this experiment must be made with great caution. The phosphorus must be cut under water, and the piece employed must not exceed half the size of a small pea. The glass jar, in which the combustion is made, is not unfrequently broken by the heat. The result of this combustion is the phosphoric acid, from the combination of the phosphorus with the oxygen. In all these cases, if the products of the com- bustions be carefully weighed, it will be found to ex- ceed that of the substances burned, and the oxygen will be diminished, which shows they have ab- sorbed a quantity of the oxygen employed. But this is still further proved, because the oxygen may be extracted from these newly-formed com- pounds, and the original bodies will be thus made to re-appear. If the metal potassium, or sodium, be burned in oxygen, they form, by their union with it, the alka- lis, potass and soda ; so that oxygen is not only an acidifying^ but an alkalising principle. Oxygen appears to be connected with the cause of the red colour in blood, for if dark coloured blood be put into a phial of oxygen gas and shaken, the blood will assume a bright red colour. S9 NITROGEN. Nitrogen gas is so called, because its base' forms nitric acid by its union with oxygen. It was by Lavoisier named azotic gas, and its base azote, from a Greek word signifying without life, because it is entirely destructive to animal life. This, also, though a very abundant principle, cannot be exhibited in a free or uncombined state. In the state of gas, it forms a considerable part of our atmosphere ; - in the solid state it enters into the composition of animal and vegetable bodies, nitric acid, and ammonia. It is incapable of sup- porting combustion or animal life. It is not ab- sorbed by water, and it has no acid properties. It may be obtained by separating the oxygen from a portion of the atmospheric air ; the residue will be nitrogen. This is done by exposing a cer- tain quantity of atmospheric air to sulphuret of potass, which absorbs the oxygen, leaving the nitrogen free. It may be also obtained by treating muscular flesh, (as lean veal) with nitrous acid in a retort ; the flesh is decomposed, and the nitrogen set at liberty. That it does not maintain combustion, and is fatal to animal life, may be proved by plunging a lighted taper into a vessel filled with this gas, the taper will be immediately extinguished. If a small animal, as a mouse, or a bird, be immersed in it, it im- mediately dies. D 4 40 COMBINATIONS OF OXYGEN AND NITROGEN. Nitrogen and oxygen unite together in four different proportions : 1. Nitrous oxide, in which the oxygen is but half the vokime of the nitrogen. 2. Nitric oxide, in which the volumes of oxygen and nitrogen are equal. 3. Nitrous acid, in which the volume of oxygen is twice the volume of nitrogen. 4. Nitric acid, in which the oxygen is two and a half times the volume of nitrogen. Nitrons oxide. This gaseous compound, called also the gaseous odide of nitrogen, or the gaseous oxide of azote, was first discovered by Dr. Priestley ; but it is to Sir Humphry Davy that we owe a tliorough knowledge of its properties. Nitrous oxide is a permanent gas. A candle burns in it with a brilliant flame and crackling noise ; be- fore its extinction, the white inner flame becomes surrounded with a blue one. Phosphorus intro- duced into it, in a state of inflammation, burns with increased splendour, as in oxygen gas. Sulphur, introduced into it when burning with a feeble blue flame, is extinguished ; but when in a state of vivid inflammation, it burns with a rose- coloured flame. Lighted charcoal burns in it more brilliantly than in atmospheric air. Iron wire, v/ith a small piece of wood affixed to it, and introduced inflamed into a vessel filled with this gas, burns rapidly, and throws out bright scin- tillating sparks. Nitrous oxide is rapidly absorbed by water that has been boiled, and a quantity of gas equal to rather more than half the bulk of the water may be thus COMBINATIONS OF OXYGEN AND NITROGEN. 41 made to disappear ; the water acquires a sweetish taste, but its other properties do not differ per- ceptibly from common water. The whole gas may be expelled again by heat. It does not change blue vegetable colours. It has a sweet taste, and a faint, but agreeable odour. This gas explodes with hydrogen, when electric sparks are made to pass through the mixture. Animals, when confined wholly in this gas, give no signs of uneasiness at first; but they soon be- come restless, and then die. When it is mingled with atmospheric air, and then received into the lungs, it generates highly pleasurable sensations. The effects it produces on the animal system are very extraordinary ; it ex- cites the body to action, and rouses the faculties of the mind, inducing a state of great exhilaration, an irresistible propensity to laughter, a rapid flow of ideas, and unusual vigour and fitness for muscu- lar exertions, in some respects resembling the sen- sations attendant on intoxication, without any lan- guor or depression of spirits, or disagreeable feelings afterwards ; but more generally followed by vigour and a disposition to exertion, which gradually subsides. This gas is produced when substances having a strong affinity with oxygen are added to nitric acid, or to nitrous gas. It may, therefore, be obtained by various methods, in which nitrous gas or nitric acid is decomposed by bodies capable of attracting the greater part of their oxygen. The most commo- dious and expeditious, as well as cheapest mode of obtaining it, is by decomposing nitrate of ammo- nia by heat, in the following manner : put into a glass retort some pure nitrate, and apply to it an ArgaQd's lamp ; the salt will soon liquify, and 42 COMBINATIONS OF OXYGEN AND HYDROGEN. when it begins to boil, gas vviJI be evolved. Increase the heat gradually, till the body and neck of the retort become filled with a milky white vapour. In this state, the temperature of the fused nitrate is between 340 and 480°. After decomposition has oroceeded for some minutes, so that the gas, when examined, quickly enlarges the flame of a taper, it may be collected over water. Care should be taken, during the whole process, never to suffer the tem- perature of the fused nitrate to rise above 500^ of Fahrenheit; which may be easily judged of from the density of the vapours in the retort, and from the quick ebullition of the fused nitrate ; for if the heat be increased beyond this point, the vapours in the retort acquire a reddish and more transparent appearance, and the fused nitrate begins to rise, and occupy twice the bulk it did before. The nitrous oxide, after its generation, should stand over water for several hours; it is then fit for respiration or other experiments. The explanation of this process is as follows: Nitrate of ammonia consists of nitric acid and ammonia ; nitric acid is composed of nitrous gas and oxygen ; and ammonia consists of hydrogen and nitrogen. At a temperature of 480°, the attractions of hydrogen for the nitrogen in the ammonia, and that of nitrous gas for the oxygen of the nitric acid, are diminished; while, on the contrary, the attractions of the hydrogen of the ammonia for the oxygen of the nitric acid, and that of the remaining nitrogen of the ammo- nia for the nitrous gas of the nitric acid, are in- creased; hence all the former affinities are broken, and new ones produced; namely, the hydrogen of the ammonia attracts the oxygen of the nitric acid, the result of which is water. The nitrogen of the NITRIC OXYDE. 43 ammonia now combines with the disengaged nitrous gas, and forms nitrous oxyd. To experience its effects in breathing it, put about a gallon into a large bladder, or oiled silk bag, having a tube attached to it, of three-fourths of an inch in diameter. First, the common air must be expelled from the lungs, before the tube is received into the mouth, and the nostrils must be accurately closed with the hand. It must then be breathed backwards and forwards into the bag for a few minutes. Nitric Oxyde is called also nitrous gas. This com- pound of oxygen and nitrogen cannotbe obtained by direct combination, but by abstracting from nitric acid a portion of its oxygen, leaving the remainder in such proportion as to constitute nitric oxide. When pure, it is not acid, and is void of colour. It is incapable of supporting the combustion of most bodies; nevertheless, phosphorus and pyro- phorus burn in it. Nitrous gas is made by putting clippings or filings of copper into a retort with nitric acid, diluted with thrice as much water ; red fumes will be given out, if the gas is suffered to escape into the air ; but if collected in the pneu- matic apparatus, the gas is colourless. In this pro- cess, the metal attracts the oxygen from the nitric acid, and becomes oxydated ; the rest of the acid being deprived of a great portion of its oxygen, can no longer exist as acid ; it therefore expands, be- comes aeriform, and appears as nitrous gas. When nitrous gas and oxygen gas are mixed to- gether in a glass vessel, previously exhausted of air, they instantly unite, and form a reddish coloured gas, which has but half the volume of the two gases, and which is highly acid. This new compound is called nitrous add gas. 44 NITROUS ACID. Nitrous acid gas is very easily absorbed by water, rendering it a green, sour liquid. When nitrous gas is mixed with atmospheric air, the same red fume appears, from the nitrous gas uniting to the oxygen of the atmosphere, leaving the nitrogen by itself. Hence this gas has been used for measuring the quantity of oxygen gas con- tained in air, and an instrument for this purpose has been called an Eudiometer. A tall glass tube, sealed at one end, is used for this purpose, filled with water, and inverted in the pneumatic apparatus. Send up a certain measure of the air to be examined into this tube, and mark the space which it occu- pies in the top of the tube. Then add to it a mea- sure of nitrous gas, and observe the degree of diminution. By comparing how much different specimens of air will be di"minished by the same quantity of nitrous gas, the relative quantities of oxygen in each may be estimated. This method of analysing atmosphere is not considered as very cor- rect, and other modes are sometimes used, where there are fewer sources of inaccuracy. Nitrous Acid. Considerable uncertainty prevails respecting this acid. The yellow coloured fuming acid, to which this name has been given, appears to be only nitric acid holding nitrous gas in solution. The nitrous gas may be expelled from it by the application of heat, and then the nitric acid is left colourless. But if nitrous gas and oxygen gas be mixed together, without the access of water, by intro- ducing them into a vessel previously exhausted of air, an union takes place ; the two gases diminish to half the volume, and an acid gas is produced. NITKIC ACID. 45 This is the nitrous acid in a gaseous form. This acid gas is extremely absorbable by water, which is at first rendered green : then, as the absorption goes on, it becomes blue, and, finally, of an orange colour : by adding more water, it may be brougTit back to the green colour. If dry nitrate of lead be distilled, an orange- coloured liquid comes over; which is considered as nitrous acid nearly pure. Nitric Acid. This acid is one of those which have been longest known to chemists. It is so named from nitre, from which it was procured. The corrosive acid called aqua fortis is an impure and weak nitric acid: but it was long used before its analysis was known: this we owe to Cavendish. NitrCi called also saltfetre^ consists of this acid united with potass, and the process for procuring the acid depends upon decomposing this salt. For this purpose, some substance is added to the nitre that has an attraction for the potass sufficiently strong to overcome that of the nitric acid, and, consequently, to allow it to be expelled by heat. Sulphuric acid is used for this purpose. During its expulsion, however, the nitric acid suffers a partial decompo- sition ; for though it is nitric acid that exists in the salt, it is nitrous acid that condenses in the receiver in the form of orange fumes. This is the common nitrous acid of commerce. To convert this into nitric acid, another process is necessary. By distillation, nitrous acid gas is driven off, leaving the nitric acid colourless. Or, 40 ATMOSPHERIC AIR. it is distilled on black oxide of manganese, which gives more oxygen to it. Nitric acid is extremely caustic; that is, acts powerfully upon animal substances. It unites with the alkalis and earths ; it oxidates all the metals except gold and platina ; it thickens and blackens oils, converting them into a coal, or inflaming them, according to the nature of the oil, and the degree of the concentration of the acid. The combinations of nitric acid with different bases are called nitrates. When the nitrogen and oxygen gases are mingled together, they form a compound exactly resembling common or atmospheric air. Atmospheric Air Is, indeed, essentially composed of these two gases: and its analysis or decomposition has been one of the most interesting discoveries of modern che- mistry. It is curious that one of the ingredi- ents of this substance, so necessary to animal life, should, by itself, be highly deleterious. It has been completely proved, that the air of the atmosphere is a compound body, formed by the mixture of oxygen gas and nitrogen gas. The first is the only one of them that supports combustion ; and when combustion takes place in common air, it is this part that unites to the burning body, form- ing either an oxide or an acid. If mercury be heated in a given quantity of atmospheric air for some time, it will become changed into a red pow- der, which will weigh more than the mercury ; the air will be found to be diminished in quantity, and 13 ATMOSPHERIC AIR. 4^ to be no longer capable of supporting combustion. The reason of this is, that the oxygenous part of the air has united to the metal, and converted it into an oxyde, leaving behind only the nitrogen. This decomposition of the atmospheric air may be effected more easily by burning phosphorus in it. During the combustion of the phosphorus, it unites to the oxygen, and forms phosphoric acid j the remainder is nitrogen. The proportion of oxygen gas contained in a given quantity of atmospheric air can be ascertain- ed by various processes. One method is, by in- verting a glass tube into a solution of sulphuret of potass. This substance will absorb the oxygen gas, but not the nitrogen ; hence the air in the tube will diminish in bulk, and what remains will show the proportion of nitrogen. It was supposed by modern chemists, until lately, that oxygen was essential to combustion ; and that this process was, in all cases, the combination of oxygen with the combustible body; but it has been found, that there are some other substances, as chlorine and iodine, which have also this pro- perty of supporting combustioii : it is, however, the oxygen that acts in all the usual combustions in common air. The heat and light were supposed to be separated from oxygen, the base of the gas, which became fixed in the burned body. At pre- sent it is maintained by some, that combustion may be the consequence of intense chemical ac- tion, and need not depend upon any particular combination. This subject, however, remains very obscure. Air, which has been breathed, is found to have lost its oxygen. This principle is retained in the 48 ATMOiSPHERIC AIR. Jungs, and is absorbed into the blood: it appears essentially necessary to vitality. An animal can only live for a limited time in a given portion of air. If a mouse or a bird be con- fined under a glass that is closed, they will soon die ; a candle, also, will burn only a short time. In crowded rooms, where there is not a free circula- tion of air, the oxygen is diminished by the respi- ration of so many persons, and the air is rendered unhealthy. The lights, also, are observed to burn dim, and contribute much to exhaust the oxygen. This points out the importance of ventilating all kinds of apartments, but particularly public places. It has been found that in 100 parts by measure of atmospheric air, there are 21 parts of oxygen gas and 79 of nitrogen gas. From the property of oxygen as being essential to respiration and animal life, it had been thought that the salubrity of air must depend upon the quantity of oxygen which it contained ; but, al- though the airs of various places have been ex- amined, as that of towns, prisons, the country, tops of hills, the ocean, &c., it appeared that the proportion of oxygen did not sensibly differ in them all. The healthiness of certain airs, therefore, must depend upon some other circumstances. Although the great mass of the atmosphere is to be considered as consisting of oxygen and hydro- gen, yet it contains a small quantity of many other gases, and also water, and a variety of exhalations and substances dissolved in it. It always contains a portion of carbonic acid gas, perhaps 1 part in 1000,for alkaUes become effervescent when exposed to it, and lime water acquires a pellicle on being HYDROGEN. 49 exposed a sufficient time to the action of the air, even upon the highest mountains. Since the oxygen of the atmosphere is continu- ally abstracted from it by various decomposing processes, it would appear that nature must have some mode of renewing a principle so important. Vegetables have been supposed to perform this office, since they always exhale oxygen gas in the day, and particularly when the sun shines. This circumstance may be easily observed by putting some leaves into an inverted tumbler of water placed in the sun-shine. Minute globules of air will be seen rising from the leaves, which, col- lected at the top and examined, will be found to be oxygen. HYDROGEN. Hydrogen is so called from two Greek words signifying the genei^ator of water, because it is one of the constituent principles of this fluid. It is also one of the ingredients of bitumen, of oils, fat, ardent spirits, ether, and of all the proximate com- ponent parts of animal and vegetable bodies : it forms a constituent part of all animal and vegeta- ble acids : it is one of the elements of ammonia, and of various compound gases. It possesses so great an affinity for caloric, that it is impossible to procure it in the concrete or liquid state, independent of combination. Hydro- gen united to caloric forms hydrogen gas. Hydrogen gas is the lightest substance whose weight we are able to to estimate; when in its purest state it is about thirteen times lighter than atmospheric air. It is unfit for respiration j ani- VOL. II. E 50 HYDROGEN. mals, when obliged to breathe in it, die ahnost in- stantaneously. It has a peculiar and disagreeable smell. It is decomposed by living vegetables, and its base is one of the constituents of oil, resin, &c. It is highly inflammable, and burns rapidly when kindled in contact with atmospheric air, or oxygen gas, by means of the electric spark, or by an in- flamed body, exhibiting a blue lambent flame. Water absorbs about one thirteenth of its bulk. It dissolves carbon, sulphur, phosphorus, arsenic, and many other bodies. When its basis combines with that of oxygen gas, water is formed, and with nitrogen it forms ammonia. An easy method of obtaining hydrogen gas consists in subjecting water to the action of a substance which is capable of decomposing this fluid. For this purpose, let sulphuric acid, diluted with four or five times its weight of water, be poured on iron filings or bits of zinc, in a small retort or glass bottle ; as soon as the diluted acid comes in contact with the metal, a violent effer- vescence takes place, and hydrogen gas escapes, without external heat being applied. It may be collected in the usual manner over water, taking care to let a certain portion escape, on account of the common air contained in the disengaging vessel. Hydrogen gas is often found in great abundance in mines and coal-pits, where it is sometimes gene- rated, and becomes mixed with the atmospheric air of these subterraneous cavities. If a lighted can- dle be brought into this mixture, it explodes, and produces the most dreadful effects. It is called by miners the Jire damp. It generally forms a cloud HYDROGEN. 51 in the upper part of the mine, on account of its lio-htness, but does not mix there with atmospheric air, unless some agitation takes place. The miners frequently set fire to it with a candle, laying, at the same time on their faces, to escape the violence of 'the shock. An easier and safer method of clearing the mine is, by leading a long tube through the shaft of it to the ash-pit of a furnace ; by this means the gas will be conducted to feed the fire. Hydrogen gas, though itself inflammable, extin- guishes burning bodies, and is incapable of main- taining combustion. Bring an inverted jar filled with hydrogen gas over the flame of a candle, and depress the jar, so that the lighted wick may be wholly surrounded by the gas 5 the candle will be immediately extinguished. Hydrogen gas is only inflammable when in con- tact with atmospheric air or oxygen gas. Fill a small phial with hydrogen gas, and take it from the pneumatic trough, placing the thumb on the mouth thereof, to prevent the gas from escaping ; if a lighted taper be applied to the mouth of the phial, the gas will take fire, and burn with a lam- bent flame. The gas will only burn where it is in contact with the atmospheric air ; the flame will descend gradually, till all the gas is consumed. If the hydrogen gas be pure, the flame will be of a blue colour ; but if the gas holds any substance in solution, which is generally the case, the flame is tinged of different colours, according to the sub- stance. It is usually reddish, because the gas holds in solution a little charcoal. On this principle i? constructed the philosophical candle, which cannot be easily blown out. Fill with hydrogen gas a bell glass, furnished with a E 2 52 HYDROGEy. capillary tube ; compress the gas, by making the bell descend below the surface of the water in the pneumatic trough ; then apply a lighted taper to the upper extremity of the tube ; the gas will take fire, and exhibit a candle, which will burn till all the gas is exhausted. Artificial fire-works may be constructed by filling bladders with hydrogen gas, and connecting them with revolving jets, tubes, &c., bent in different directions, and formed into various figures pierced with holes of different sizes. The air which is forced through these holes by pressing the blad- ders, will, when inflamed, exhibit a curious fire- work, without either noise or smoke. By the inflammable property of hydrogen gas, and the effects of electricity, a curious lamp has been invented by Volta, which, by turning a stop cock only, may instantly be lighted, and that many hundred times. Hydrogen gas burns more readily in proportion as it is surrounded with a larger quantity of atmos- pheric air. Hydrogen gas and atmospheric air, or, what is better, oxygen gas, may be mixed together, so that every particle of each gas shall be contigu- ous to a particle of the other, in which case they will burn with great rapidity. Into a strong bottle, capable of holding about four ounces of water, put one part of hydrogen gas and two of amospheric air. On applying a lighted taper, the mixture will explode with a loud report, and the inside of the bottle will become moist. It will be prudent to wrap a handkerchief round the bottle, to prevent it from doing any in- jury if it should burst. The same experiment may be made with oxygen gas, instead of atmospheric air, changing the pro- HYDROGEN. 53 portions, and mixing only one part of oxygen gas with two of hydrogen. The report will then be much louder than with common air. This experiment may be made conveniently by means of an apparatus called the hiflammahle air pis- tol. To charge it, nothing more is necessary than to introduce its mouth inverted into a wide-mouthed bottle, filled with a mixture of oxygen and hydro- gen gas, leaving it in for a few seconds ; it is then to be stopped with a cork, and may be fired by the electrical spark taken from the prime conductor of the machine, or by a charged Ley den phial. It has been, with great plausibility, conjectured, that the noise of thunder is the effect of the rapid combustion of hydrogen and oxygen gas, fired by the electric spark ; and that the rain which falls so copiously at the time of thunder-storms, is owing to a sudden formation of water by this means. From its Hghtness, it has been employed for making air-balloons, which have been already de- scribed. Soap-bubbles, filled with hydrogen gas, ascend in the air. To show this, fill a bladder with hydro- gen gas, and fasten it to a tobacco-pipe ; dip the bowl of the pipe into a lather of soap, squeeze the bladder gently, in order to form a bubble, and de- tach it in the usual manner. These bubbles will rise rapidly into the air : if a lighted taper be pre- sented to them, they catch fire and burn with a slight explosion. If the bladder be filled with a mixture of hydro- gen and common air, the soap-bubbles will ascend, and when the taper is presented to them they will explode with a loud report. This experiment is more striking if oxygen gas be mixed with hydrogen. If the bladder be squeezed so as to E 3 S4i HYDROGEN AND OXYGEN. form a great many bubbles on the surface of the bason,'the report will be as loud as that of a cannon. It has lately been discovered, that hydrogen, like oxygen, is an acidiJi,:hig prmciple. United to chlo- rine, it forms hydro -chloric acid, which is the same as muriatic acid. Combined with iodine, it forms hydriodic acid. When hydrogen gas is united to sulphur, it forms sulphureted hydrogen, which has also the properties of an acid. Tellureted hydrogen has also acid properties. Hydrogen and Oxygen. It has been already mentioned, that these two elements, when combined, form "doater. Till lately, water was considered as a simple sub- stance, or element ; no one had ever been able to decompose it ; and the decomposition of it, which is daily effected in natural processes, had escaped observation. We shall, however, give such evi- dent proofs of the decomposition and recompo- sition of water, as will clearly show that it is not a simple body. Ea:periment I. — A tube of common glass E F (Plate 2. fig. 70j well annealed, and difficult to be fused, about ten or eleven lines diameter, was placed across a furnace C F E D, in a position somewhat inclined ; and to its upper extremity was adapted a glass retort A, containing a known quan- tity of distilled water, and resting on a furnace V V. To the lower extremity of the glass tube F was applied a worm S S, connected with the dou- ble-tubulated flask H, and to the other tubulure was adapted a bent glass tube K K, destined to con- vey the gas to an apparatus proper for determining HYDROGEN AND OXYGEN. 55 the quality and quantity of it. When the whole was thus arranged, a fire was kindled in the fur- nace C F E D, and maintained in such a manner, as to bring the glass tube E F to a red heat, but without fiising it ; at the same time as much fire was maintained in tlie furnace V V X X, as to keep the water in the retort A in a continual state of ebullition, In p]'oportion as the water in the retort A as- sumed the state of vapour by ebullition, it filled the interior part of the tube E F, and expelled the atmospheric air which was evacuated by the worm S S, and the tube K K. The steam of the water was afterwards condensed by cooling in the worm S S, and fell drop by drop, in the state of water, into the tubulated flask H. When the whole of the water in the retort A was evaporated, and the liquor in the vessels had been suffered to drain off completely, there was found in the flask H a quan- tity of water, exactly equal to that which was in the retort A, and there had been no disengage- ment of any gas ; so that this operation was merely a common distillation, which gave absolutely the same result as if the water had never been brought to a state of incandescence, in passing through the glass tube E F. Ea:perime7it II. — Every thing being arranged as in the preceding experiment, twenty-eight grains of charcoal reduced to particles of a moderate size, and which had been previously exposed for a long time to a white heat in close vessels, were intro- duced into the glass tube E F. The operation was then conducted as before, and the water in the re- tort A kept in a continual state of ebullition, till it was totally evaporated. The water in the retort A was distilled as in the E 4- 56 HYDROGEN AND OXYGEN. preceding experiment, and being condensed in the worm S S, had fallen drop by drop into the flask H ; but at the same time there had been disen- gaged a considerable quantity of gas, which escaped through the tube K K, and was collected in a pro- per apparatus. When the operation was finished, there was found nothing in the tube E F but a few ashes, and the twenty-eight grains of charcoal had totally disappeared. The gases disengaged were found to weigh alto- gether 113.7 grains. There were found two dif- ferent kinds of gas, viz. 114 cubic inches of carbonic acid gas, weighing 100 grains, and 380 cubic inches of a very light gas, weighing 13.7 grains. This last gas took fire, on being applied to a lighted body in contact with the air. In ex- amining afterwards the weight of the water whicli had passed into the flask, it was found less than that in the retort A by 85.7 grains. In this ex- periment, therefore, 85.7 grains of water and 28 grains of cliarcoal formed carbonic acid gas equal to 100 grains, and a peculiar gas susceptible of in- flammation, equal to 13.7 grains. To form 100 grains of carbonic acid gas, 72 grains of oxygen must be united to 28 grains of charcoal or carbon. The 28 grains of charcoal put into the glass-tube EF, took, therefore, from the water, 72 grains of oxygen, since there was formed carbonic acid equal to 100 grains. It appears, then, that 85-7 grains of water are composed of 72 grains of oxygen, and 13.7 grains of a substance forming the base of a gas susceptible of inflammation. The following is a proof of it. The apparatus being arranged as above, instead of the 28 grains of charcoal, 274^ grains of thin -shavings of iron, rolled up in a spiral form, were HYDROGEN AND OXYGEN. 57 introduced into the tube E F ; the tube was then brought to a red heat as before ; and, in the same manner, the whole of the water in the retort A was made to evaporate. In this experiment there was disengaged only one kind of gas, which was inflammable ; there was obtained of it about 406 cubic inches, weighing 15 grains. The 274 grains of iron put into the tube E F were found to weigh 85 grains above what they did when introduced ; and the water first employed was diminished 100 grains. The volume of these iron shavings was found to be greatly enlarged. The iron was scarcely any longer susceptible of attraction by the magnet ; it dissolved without effervescence in acids ; in a word, it was in the state of a black oxyd, like that which has been burned in oxygen gas. In this experiment there was a real oxydation of the iron by the water, entirely similar to that effected in the air by the aid of heat. 100 grains of water were decomposed ; and of these 100 grains, 85 united to the iron, to reduce it to the state of black oxyd ; these 85 grains, therefore, consisted of oxygen ; the remaining 15 grains, combined with caloric, formed inflammable gas. It thence follows, that water is composed of oxygen and the base inflammable gas, in the proportion of 85 to 15, or of I7 to 3. If it be true, as we have endeavoured to prove, that water is composed of hydrogen combined with oxygen, it thence results, that, by re-uniting these principles, water ought to be produced. This, in- deed, is what takes place when, into a vessel filled with oxygen, a stream of hydrogen is introduced and set fire to. 58 HYDROGEN AND OXYGEN. In proportion as the combustion proceeds, water is deposited in the internal surface of the vessel ; the quantity of this water gradually increases, and it unites itself intolarge drops, which run down the sides of the vessel, and are collected in the bottom of it. In making this experiment, proper means were taken to ascertain the weight of the gases em- ployed. Before the experiment, the vessel v/as weighed ; and, by weighing it after the operation, the weight of the water that had been formed was obtained. Here, then, is a double proof; on the one hand, the weight of each of the gases em- ployed ; and, on the other, the weight of the water formed ; and these two quantities were found to be equal within a two hundredth part. It was thus found that 85 parts by weight of oxygen, and 15 parts also by weight of hydrogen, are required to compose 100 parts of water. These phenomena of the decomposition and recomposition of water are continually effected be- fore our eyes, by the temperature of the atmos- phere, and the agency of compound affinities. It is this decomposition which gives rise, at least in a certain degree, to the phenomena of spirituous fer- mentation, to those of putrefaction, and to those of vegetation. Pure water is perfectly transparent, and has no taste nor smell. It is not liable to change. It can absorb a variety of gases ; and when exposed to the atmosphere, it always contains a small quantity of common air, which may be separated by boiling, or by the air-pump. Rain-water is the purest which we see in nature ; but, for delicate chemical pro- cesses, it is distilled in glass vessels. Spring- water generally holds some salts in solution, which gives it various properties. HYDROGEN AND CARBON. 59 Hydrogen gas combines with several simple bodies, constituting, with them, peculiar and dis- tinct gases. Hydrogen and Carbon. Hydrogen gas unites to carbon, and forms, with it, HydrO'Carhonate gas. Of this there are two kinds, according to the quantity of carbon which they contain. Light Hyd?^o-Carbo?iate. — This is frequently seen rising from stagnant ponds, when stirred. It may also be procured by passing the vapour of water over red hot charcoal. It burns with a pale blue flame. It is also called Light carbureted Hy- drogen. It is contained very abundantly in many coal mines, where it is disengaged from fissures in the strata, often in great quantities; which are called by the miners blowers. When it has accumulated iu any part of the mine, it forms an explosive compound, by its admixture with the common air : and when the miners approach it with lighted candles or lamps, it inflames with a tre- mendous explosion, killing the workmen and de- stroying the works. Indeed, nothing can be more terrible than such accidents ; and there is reason to think that they have happened more frequently than is generally known. The body of miners are, therefore, infinitely indebted to Sir Humphry Davy for his invention of the Safety-lamp, an in- strument which they can carry lighted into an ex- plosive mixture, without any danger of setting fire to it. This gas is called the Fire-damp by the miners. Bi'Carbureted Hydrogen. ■ — This gas contains 60 GAS ILLUMINATION. twice as much carbon as the last. It is heavier than it, and is also called the Heavy hydro-car- bonate. It burns with a bright white flame, like that of the best wax candles. It has been called the olejiant gas, because, when mixed with chlo- rine in an exhausted vessel, or over water, a pe- culiar fluid was formed, resembling a thick oil, but which has been termed by Dr. Thomson, Chloric ether. Bi-carbureted hydrogen may be procured by heating, in a retort, four parts of sulphuric and of one alkohol ; when the mixture boils the gas comes over. Gas Illumination. — The carbureted hydrogen gases are now extensively employed for the pur- pose of giving light. When coal is put into an iron retort placed in a furnace, an inflammable gas is given out, which is a mixture of the two above- mentioned species of hydro-carbonate, together with small quantities of carbonic acid gas, car- bonic oxide, sulphureted hydrogen, tar, ammonia, and water. These last substances are separated by passing the gas through a mixture of quicklime and water; and the purified gas then passes into the gasometer^ from which it is distributed by means of pipes. The coal that has been thus acted upon, being deprived of its volatile principle, is con- verted into colce. The kind of coal, fittest for the production of good gas, is that which contains most bitumen and least sulphur. Messrs. J. and P. Taylor have lately taken out a patent for the production of carbureted hydrogen gas from oil. The oil is decomposed by suffering it to drop into a bent iron tube, laid through a furnace. The oil is separated into charcoal and SULPHURETED HYDROGEN GAS. 6l bi-carbureted hydrogen, the flame of which much exceeds in whiteness and brilliancy that of coal o-as, which is a mixture of the two species of hydro- carbonates. Another material advantage in the use of the oil gas is, that it is not mixed with the impu- rities of coal gas, many of which are highly inju- rious to health, and to the furniture of houses. From experiments it appears that the coal gas does not contain above 10 per cent, of bi-carbureted hydrogen ; while the oil gas consists almost entirely of it. Sidphiir^efed Hydrogen Gas. This is a combination of hydrogen gas with sul- phur. It has an extremely fetid odour. It is in- flammable. It cannot support life nor combustion : indeed, it is highly deleterious. Water can absorb it, and acquires its peculiar smell. The mineral waters of Harrowgate and Aix-la-Chapelle owe their properties chiefly to this gas. Sulphureted hydrogen gas has the property of causing metallic oxides to re-approach the metallic state ; the hydrogen of the gas attracting the oxy- gen. If a piece of paper, dipped in a solution of acetite of lead, be exposed to this gas, it instantly becomes blackened. If letters be written with the solution of lead, they will be invisible when dry, but will become black on exposing them to sul- phureted hydrogen. It has also acid properties. It unites with the alkalis and the earths, forming compounds called Hydro-sul'phurets. This gas affords an exception to the doctrine of Lavoisier, that oxygen was the only acidifying prin- ciple ; for in it there is no oxygen, yet it performs 62 PHOSPHORATED HYDROGEN GAS. the most important functions of an acid, reddening vegetable blues, and combining with alkalis. The hydro-sulphurets are formed by passing a stream of this gas through solutions of the alkalis. Phosphorated Hydrogen Gas, This gas consists of hydrogen and phosphorus. It is so combustible that it inflames by mere con- tact of atmospheric air. It has a very disagreeable smell, like that of putrid fish. To procure it artificially, put one part of phos- phorus and ten of a concentrated solution of potass, into a glass retort, and apply a gentle heat. When the mixture boils, the gas will come over, and may be collected in the pneumatic apparatus. In preparing this gas, the body of the retort should be filled as nearly as possible with the mix- ture, otherwise the first portion of the gas, finding atmospheric air in the retort, inflames, a vacuum is produced, and the water is forced up into the retort, endangering the bursting of it. If the bubbles of air which are formed in the retort are suffered to escape into the atmosphere, they will inflame instantly with a slight explosion; at the same time a beautiful dense white circular ring of smoke rises, and gradually enlarges as it ascends. This gas maybe made to burn under the surface of water. Put into a deep glass some phosphuret of lime, and half the quantity of oxy-muriate of potass : fill the vessel with water. Procure a long- necked glass funnel and plunge it into the vessel, putting it down to the bottom. Take some con- CHLORINE. 63 centrated sulphuric acid and pour into the funnel. As soon as the decomposition of the water and that of the muriate takes place, flashes of fire will be seen to issue from the bottom of the vessel, having a screen colour. If a ribbon be impregnated by a solution of gold, and hung in a jar containing this gas, the gold will be revived, and will gild the ribbon. CHLORINE. This gaseous body is now generally regarded as an elementary substance : but it was lately con- sidered as a combination of muriatic acid with oxy- gen, and was hence called oxygenated muriatic acid gas. It is obtained by heating a mixture of muriatic acid and black oxide of manganese over a lamp : the chlorine will be evolved. In this process, ac- cording to the present theory respecting the ele- mentary nature of chlorine, the oxide of manganese and muriatic acid decompose each other : the oxy- gen of the oxide unites to the hydrogen of the muriatic acid to form water, leaving the other constituent of the acid, viz. the chlorine, disen- gaged. Chlorine is rapidly dissolved by water, the so- lution being of a pale yellow colour : it has a nauseous taste, and an extremely suffocating smell. When the gas is perfectly free from moisture, it has no action on vegetable colours, but, dissolved in water, it destroys them entirely. From this property, it is extensively employed in shortening the process of bleaching linen, and also paper; but it is said that it is apt to injure 64 CHLORINE. the durability of the substances bleached, and no doubt, except due care is employed, this must be the case. Prints that have been stained by smoke and dust may also be whitened by it, as it does not act upon the printing ink. Chlorine has likewise been found extremely effi- cacious in destroying the putrid effluviag in pri- sons, and hospitals, and preventing the infection of the small-pox. But when used for this purpose, a small quantity only is diffused through the air, for, when taken into the lungs by itself, it is fatal to animal life ; and, indeed, in preparing it, great precaution should be used not to inhale it, as it is extremely dangerous if not sufficiently diluted. Notwithstanding its unfitness for respiration, it supports combustion in a remarkable degree. Some bodies, as phosphorus, and several of the metals, are spontaneously ignited when plunged into a vessel of chlorine ; on this account it is now reckoned one of the supporters of combustion, a property which was lately supposed to be only en- joyed by oxygen. In this view, combustion is re- garded only as the result of intense chemical action, and it is supposed that the compounds of chlorine have less capacity for caloric than their constituent principles, and, consequently, that ca- loric is evolved at the moment of their formation. Chlorine is known to combine with oxygen in three different proportions, forming 1. Omde of Chlorine, or Euchloriney a gaseous body, not acid, having a smell less irritating than chlorine. 2. Ojnjchloric Acid, which does not exist inde- pendent of water or a base. 3. Chloric Acid. — Chloric acid cannot be ob- tained unmixed with water. It is colourless and CHLORINE. C)5 sour ; acts on metals, and combines with alkalies, forming chlorates. Chlorate of potash was formerly called oxymu- riat of potash. It is a soluble white salt. When heated it gives out oxygen, and the residue is chloride of potassium. It forms extremely explo- sive compounds with phosphorus, sulphur, and charcoal. A grain, with a minute portion of phos- phorus, laid upon an anvil, and struck with a hammer, makes a very loud report ; but this experiment should not be attempted by the i/owig student. From its detonating quahty, it had been imagined that it could be used advantageously in the manufacture of gunpowder, but it has not succeeded. Chlorate of potash is made by causing a stream of chlorine to go through a solution of caustic potash. The combinations of chlorine with other simple bodies, form chlorides, if they are not acids, as chloride of sulphur, &c. Chlorine and hydrogen. This compound body, which, according to the present nomenclature, is called hydrochloric acid gas, was known by the name of muriatic acid gas. It is readily obtained by distilling a mixture of common sea salt and sul- phuric acid. The sulphuric acid combines with the soda, one of the constituents of salt ; and the other constituent, the muriatic acid gas, is set free. Mu- riatic acid gas cannot support life nor combustion. It has a «harp pungent odour, and occasions white fumes when it is mixed with moist atmospheric air. It reddens vegetable blues. It combines with the alkaline bases : with ammoniacal gas it forms mu- riate of ammonia. VOL. II. F 60 IODINE. It is decomposed by the electric spark into hy- drogen and chlorine. It is readily absorbed by water, which then becomes very acid, and forms the liquid muriatic acid. The muriatic acid, called also the mai^ine acid and the spirit of salt, is in very common use. It is obtained, as above-mentioned, by distilling sea salt and sulphuric acid. It exists in a state of combin- ation with alkalies and earths in the mineral kingdom in great quantity, chiefly with soda, lime, and magnesia. With soda it forms muriate of soda, common or sea salt, with which every part of the ocean is impregnated, and also some lakes. Mu- riate of soda also exists in the form of a rock in the earth, whence it is extracted : it is called rock salt. The most considerable mines of rock salt are in Poland ; extensive mines are also worked in Hun- gary, Spain, and Cheshire in England. Muriate of soda is obtained also from the sea water, by driving off the water by evaporation ; and this is done either by exposing salt water in shallow places, called saltpans, to be evaporated by the heat of the sun, or by boiling salt water in vessels, or by these methods combined. Muriate of soda, so procured, is always contaminated with muriate of magnesia and muriate of lime, from which the salt is puri- fied by different processes. IODINE. This substance, considered as a simple body, has been but lately discovered. It exists in certain marine plants, and is procured from kelp, which is SULPHUR. ()7 made by burning them. It is obtained first in the form of fumes, of a violet color, which con- dense in small opaque crystals of a blackish grey color and metallic lustre, resembling plumbago. It appears to be an element that exists in small quan- tity. It is capable of producing acids by combin- ation with other substances. With oxygen, it forms iodic acid ; and, with hydrogen, it forms hy- driodic acid. It combines with phosphorus at the common temperature, giving out heat and light, and produces with it phosphuret of iodine. With sulphur, it makes sulphur et of iodine. Iodine, also, unites with all the metals, forming with them iodurets. SULPHUR. Sulphur, known also by the name of brimstone^ is a mineral substance, frequently found pure in nature. It is of a pale yellow colour, without taste and, also without smell, except when heated. It is chiefly a volcanic product, and a great deal of what is used in this country is brought from Italy and Sicily. It is found also in nature combined with most of the metals as ores : united to iron, it forms iron pyrites. Sulphur is extracted from pyrites by exposing it to heat in tubes, by which the sulphur is driven out and received in vessels with water : when melted and poured into moulds, it constitutes the roll sul- phur in common use. A good deal of this is made in England. The sulphur thus obtained, however, is not quite pure. To purify it, it is sublimed by F ^ (j8 sulphur. a gentle heat in close rooms, and thus forms Jloxvei^s oj' sulphur. If sulphur be exposed to heat it will soon fuse, and, by continuing the fusion for some time, it will become thick and tenacious. If worked between the fingers under water in this state, it acquires a consistency like wax, and may be employed for taking impressions from seals or gems. This change in the sulphur has been ascribed to oocijda- tion; but the same effect takes place if the sulphur be kept in fusion without access of air. Sulphur becomes electric by friction, and then exhibits negative electricity. It is soluble in oils. It does not combine with charcoal, but unites to phosphorus by means of heat. Sulphur and iron have a great attraction for each other. If a bar of iron be heated to whiteness, and then touched with a roll of sulphur, the two bodies combine and drop down together in a fluid state, forming sulphuret of iron. Sulphur also unites to potash and to soda, by melting them together in a crucible : by this liver- brown substances are formed, called sulphurets of potash or of sodciy which are soluble in water. Sulphur is a highly inflammable body, burning with a pale blue flame. Put some threads, dipped in sulphur, into a vessel floating in water. Set fire to them, and cover the whole with an inverted glass. The threads will continue to burn for some time, and the receiver will be filled with a dense white vapour. This vapour is the sulphurous acid, formed by the union of the sulphur and the oxy- gen during the combustion. It is absorbed by the water which will ascend in the receiver. Let the whole then be left till the vessel is be- come again transparent. If the water be exam- 9 SULPHURIC ACID. Qg ined, it will have a suftbcating odour and an acid taste. Sulphurous acid, or the vapour of burning sul- phur, has been found very useful for destroying the infection of clothes and small uninhabited places, and for fumigating letters from contagious places. It is used in dyeing, and for whitening straw and silk. Sulphuric Acid. This acid is composed of sulphur and oxygen, and contains a greater proportion of oxygen than sulphurous acid. This acid is the same with that commonly known by the name oi Oil of Vitriol. It was so called ori- ginally, because it was procured from green vitriol; now called sulphate of iron. Common oil of vitriol has strong acid properties. It is of an oily consistence, and has usually a brown tinge, from impurities. It is inodorous, and about twice as heavy as water. It is highly corrosive, acting strongly on vegetable and animal substances. It attracts water very strongly, and cannot be entirely separated from it by any known process. When exposed to the air, it attracts the watery vapour in the atmosphere, so as to increase I'apidly in weight, which will be doubled in a month. If mixed with cold water, it suddenly becomes ex- tremely hot, even more so than boiling water; and on this account, when it is necessary to dilute it with water, this should be performed very gradually. Sulphuric acid is now made by burning sulphur mixed with nitre, in close chambers, entirely lined F 3 70 CARBON. with lead, on the floor of which a thin layer of water is put. The combustion of the nitre fur- nishes oxygen to the sulphur, and the sulphuric acid is condensed in the water. It is in this manner that the common oil of vitriol is made: but it then contains many impurities ; when freed from these, it is colourless. If sulphuric acid be heated in contact with a combustible body, as charcoal or mercury, it loses part of its oxygen, and is then converted into sulphu- reous acid gas, which must be collected over mer- curv, as it is absorbable by water. CARBON. This elementary body is widely diffused through- out nature. Common charcoal consists of it, mixed with a small quantity of foreign matter. The purest variety of charcoal is lamp black. Carbon exists as a constituent principle in all vegetable and animal matters, and remains fixed, after all the volatile parts have been carried off, during the process of combustion. Charcoal is very nearly the same, from whatever it has been procured. It is always black and brittle, and exhibits the fibrous structure of the wood. It is not at all liable to change, and hence wood is some- times charred on the outside, when driven into the ground for piles, and similar uses. The diamond, a substance so very dift'erent in appearance, has been found by experiment to be only crystallized carbon. Diamonds are found only in Asia and Brazil, and always in the alluvial soil. Diamond is the hardest body, and can only be cut CARBON AND OXYGEN. 71 by its own powder. When found in the earth, they are crystalHzed, but are usually rough, having lost the angles of their crystals by attrition. They may be cleaved or split, and are then cut with facets for jewellery. They are of various colours. The diamond was long thought to be an incombustible body, but it is now known to be capable of being burnt ; and by its union with oxy- gen, it forms carbonic acid. But although we know that diamond is only carbon, no attempts to crys- tallize carbon, and thus to make diamonds, have succeeded. Art cannot always imitate the pro- cesses of nature, even when the materials she has used are known. Carbon and Oxygen. Carbon unites to oxygen in two proportions. We shall first consider the most common one : Carbonic Acid. — If charcoal be burnt, it com- bines with the oxygen of the atmosphere, and thus forms an acid, which, however, cannot be condensed into the liquid form, but is always aerial. Carbonic acid exists in great abundance in nature, combined with mineral bodies, chiefly lime. All limestones are formed of carbonic acid in a fixed state, united to lime. Hence this gas was at first called jixed air, which name is still sometimes used. It may be procured from limestone or marble, in the following manner : put a quantity of broken pieces of marble or chalk into a retort, and add to it some sulphuric acid, diluted with six times its weight of water: a brisk effervescence will ensuei, F 4 7^ CARBONIC ACID. and the carbonic acid gas will be disengaged, and maybe collected in the pneumatic apparatus. In this process the sulphuric acid severs the lime, leaving the carbonic acid free, which escapes in the gase- ous form. Carbonic acid gas cannot support flame, as may- be seen by plunging a lighted taper into a vessel of it : it will be instantly extinguished. It is fatal to animal life : a small animal confined in it would die in a few minutes. Its taste is sour: and it is capable of being ab- sorbed by water. Water so impregnated has an acidulous taste, and reddens vegetable blues. Many mineral waters owe their qualities to this gas, which is contained in them, and they may be imi- tated by impregnating water with carbonic acid gas. Agitation and pressure promotes the absoi'ption ; and in this manner the artificial soda water is made. During the process of fermentation, this gas is disengaged, and yeast is carbonic acid enveloped in a viscous substance. If a lighted candle be plunged into the upper part of a cask containing fermenting liquor, it will be extinguished, the apparently empty part of the vessel being filled with carbonic acid gas. This gas is heavier than common air; hence, when disengaged, it occupies the lowest situation. It may be poured from one vessel into another, which makes a pretty experiment. Fill a vessel with this gas, and then, having placed a bit of lighted paper in the bottom of an empty tumbler, pour the gas into the tumbler upon the taper: the flame will be extinguished : here the gas will be invisible, but its presence is thus manifested. CARBONIC OXIDE.- 7^ This gas is often found in the lower part of caverns, wells, mines, and other subterranean places. In mines it proves frequently fatal to the miners, who call it the choke damp. Wells, or similar places, which have been shut up for a long time, should never be entered without first putting down a lighted candle : if this is extinguished, it is not safe to go down. There are some caverns in which this gas is produced in so great a quantity, that it runs out at the opening, like a stream of water: this is particularly the case with the cele- brated Grotto del Cane. A dog is suffocated if it be held for a short time in the lower part of the cavern, but the upper part is free from this gas. Charcoal should never be burnt in rooms that have no chimney, because the red hot charcoal unites with the oxygen of the atmosphere, and forms carbonic acid, which cannot escape. Some melancholy accidents have happened from this cause. This gas has also been called mephitic air, from its suffocating quality. Carbonic acid combines with all the alkalies, and with the alkaline earths, lime, magnesia, barytes, and strontia. With these it forms a class of salts, called carbo7iates. Carbon does not combine with any of the metals except iron. This combination is the carburet of iroiiy called also plumbago and black lead ; which, however, contains only five per cent, of iron. It is the substance used for making black lead pencils. Carbonic Oiide. — This body is always gaseous. It contains only half as much oxygen as carbonic acid does. It is void of taste and smell, and fatal to animal life. It is inflammable, burning 74 CARBON AND NITROGEN. with a blue lambent flame, but does not explode when mixed with atmospheric air. It is pro- cured by depriving carbonic acid of part of its oxygen. This is effected by exposing equal parts of chalk and filings of zinc to a gradual red heat, suftering the first product to escape, which is car- bonic acid gas. The zinc deprives the carbonic acid in the chalk of part of its oxygen. Carbon and Nitrogen. This combination is called cyanogen. It is a gas- eous body, having a penetrating and peculiar smell, and burning with a purple flame. It red- dens vegetable blues. When cyanogen combines with hydrogen, it forms a triple compound, called hydrocyanic acid : this is also called Prussic acid. Prussic acid is a liquid having a very pungent odour, like that of bitter almonds. It is extremely acrid, and highly poisonous. It is called Prussic acid, because it forms one of the constituents of the well-known pigment Prussian blue, which is a combination of hydrocyanate of iron with alumine. PHOSPHORUS. This highly inflammable substance is not met with in nature uncombined ; but it exists combined with oxygen, forming phosphoric acid, in many animal and mineral substances. Phosphorus is a yellowish semi-transparent mat- ter of the consistence of wax. It is luminous in PHOSPHORUS. 75 the dark at the common temperature of the atmo- sphere. To show this property in a striking manner, write with a stick of it upon black or purple paper, or any other smooth surface ; the writing will be luminous as if on fire. The fiery appearance dis- appears and appears again by blowing upon it. It is necessary, in making this experiment, to cut the phosphorus under water, and to put it into a quill, in order to defend the hands, lest it should take fire 5 and great care ought to be taken lest any particle should be left under the nails, or in any other place, for if this were afterwards to take fire it might occasion very serious accidents, as a burn by it is extremely severe. Very slight friction is sufficient to inflame phos- phorus. Put a grain of it into brown paper and rub it with some hard body, and it will take fire and inflame the paper. It takes fire spontaneously, and burns rapidly in the open air at 122° Fahr., with a brilliant flame. On this account, it is alwavs kept under water ; and it should never be suffered to lie exposed to the air. Phosphorus is obtained by decomposing the phosphoric acid by means of charcoal in a retort. The oxygen of the acid unites to the carbon, form- ing carbonic acid j and the phosphorus distils over into water. The phosphoric acid is obtained by decomposing calcined bones by sulphuric acid. Bones consist chiefly of phosphate of lime j and in this process the sulphuric acid joins to the lime, leaving the phosphoric acid free. Phosphorus is soluble in oil in small quantity, which is thus rendered luminous. Sulphuric and nitric ether, and ardent spirit, dissolve it, though sparingly, in the cold. 70 Phosphorus and Oxygen* Phosphorus unites with oxygen in two proper* tions, forming phosphorous acid, which contains the lowest proportion of oxygen ; and phosphoric acid, which contains the greatest proportion. Phosphoric acid may be made by the rapid com- bustion of phosphorus in oxygen j but it is usually obtained from calcined bones, by decomposing them with sulphuric acid. Phosphorus has the property of de-oxidizing se- veral metallic solutions, as those of gold, silver, copper, mercury, lead, tin. If a stick of phospho- rus be left in a concentrated solution of nitrate of copper, the copper wall be precipitated upon the phosphorus in a metallic state. It also combines with lime, forming phosphu- ret of lime. When pieces of phosphuret of lime are dropt into water, flashes of fire are seen to rise out of the water, which is occasioned by the phosphuret decomposing the water, and part of the phosphorus uniting to the hydrogen gas, forming phosphuretted hydrogen gas, de- scribed before. The phosphurets of barytes and strontia have similar properties. J^hosphorus combines with chlorine and with io- dine j and also with sulphur and the metals. Its union with hydrogen has been already noticed as phosphuretted hydrogen gas. BORAX. This elementary substance is known only in the boracic acid, which consists of it united to oxygen. FLUORINE. 77 Boracic acid is rarely found native, but is gener- ally procured from the salt called borax. Borax is boracic acid united to soda, or a borate of soda. This is the //7zc«/ brought from Asia puri- fied. It is found at the bottom of certain lakes in Thibet, and in China. The boracic acid has been decomposed but lately, when it yielded to the ap- plication of galvanic electricity by Sir H. Davy. Borax is in the form of a powder of an olive colour. It is combustible. Borax is much used as a flux in soldering metals, and also for such stones as cannot be brought into fusion by alkalies. FLUORINE. This name has been given, provisionally, to the supposed base of the fluoric acid, which is ima- gined to consist of fluorine and hydrogen. The Jliwric acid has hitherto resisted all the en- deavours that have been made to decompose it completely ; and its real nature, therefore, con- tinues uncertain. According to the present no- menclature, it is now sometimes called hi/dro- Jluoric acid. Fluoric acid is obtained by adding sulphuric acid to some pounded pure fluor spar, and ap- plying heat. Fluor spar is that mineral well known by the name of Derbyshire spar, because very abundant in that county. It is employed for making vases and other ornamental works. It consists of fluoric acid and lime, or, perhaps, calcium, the metal of lime, and is hence called also fiuat of lime. The sulphuric acid, having a stronger attraction for lime 78 ALKALIES. than fluoric acid has, expels the latter and unites itself to the lime. It appears, that before the researches of Gay Lusac and Thenard, the pure fluoric acid had ne- ver been procured ; what had been considered as fluoric acid, being, in fact, a different acid, the siliceo-Jluorie acid. In their experiments, the leaden receiver was cooled by ice, and the fluoric acid condensed into a liquid form. In this state it is the most caustic substance known, corroding the skin instantly, and causing dangerous sores. Fluoric acid combines with silica, and becomes with it a permanent acid gas, called the siUceo-fiu- oric acid. This was formerly called Jluoric acid gas. It has a pungent irritating odour, will not support combustion, and forms white vapours when it comes in contact with the air. It corrodes glass, and combines rapidly with water, forming the li- quid siliceo-fluoric acid. This acid, formerly called the Jiuoric, also acts on glass, and is very acid and corrosive. In the process for making it from fluor spar and sulphuric acid, a little silicious mat- ter generally existed in the spar, or glass vessels, that had been used ; and thus the siliceo-fluoric, and not the fluoric acid, had been obtained. Fluoric acid forms Jluates with the alkalies and salifiable earths. It also unites to borax, forming an acid called the Jluo-boric acid. This does not act on glass, and is not so corrosive as fluoric acid. It gives rise to JiuO'borates. ALKALIES. Alkalies are an important class of bodies. They have received this name because one of them, POTASH. JO soda^ was procured in great abundance from a plant called kali, by the Arabians. Alkalies have peculiar properties. They change blue vegetable colours to green, and yellow to reddish brown. They unite to oil and fat, forming soap J thus rendering them miscible with water. They have an acrid and peculiar taste. They are caustic, or act powerfully upon animal substances. They combine with acids, forming with them a peculiar class of salts in which the properties of the acid and alkali disappear. Until lately, only three alkalies were known, potash, soda, and ammonia. The two former were called the fixed, the latter the volatile alkali. Their number is now increased by the addition of lithia. POTASH. Potash had long been* known by the name of the vegetable alkali. It is procured from the ashes of burnt vegetables in the following manner. Dried vegetables are burned in heaps ; the ashes are collected and lix- iviated with water. Thus the potash in the ashes is dissolved, while the rest of the ashes is insoluble. The solution is poured off from the sediment, and evaporated : what remains is the potash of com- merce, which is of a grayish colour, and contains some impurities: these are separated by being heated in a furnace. It is then white, and is called pearlash. All xvood ashes have in them more or less of this alkali, and hence they are applied to the same purposes as potash, or pearlash. so POTASH. Potash and pearlash procured in this manner are combined with a certain proportion of carbonic acid, but not so much as to destroy completely its alkaline properties : hence it is a sub-car bonate of potash. To free the alkali from the carbonic acid, another process is necessary. Twice its weight of quicklime is added to the pearlash, and the whole mixed with water. The carbonic acid having a stronger affinity to the lime than to the alkali, quits the latter, and forms carbonate of lime, which, being insoluble, falls down, while the purer alkali is kept in solution by the water, and is afterwards separated by evaporation. Sometimes it is still farther purified, if necessary, by mixing the whole with alkohol, which dissolves the pure alkali alone. The alkoholic solution ascends to the top of the fluid, and is drawn off by decant- ation. Potash, when thus prepared, is a solid white substance, and is called caustic potash, from its property of corroding the skin and flesh when it is applied to it : on this account it is frequently em- ployed by surgeons. Caustic potash, when prepared by alkohol, is united to a portion of water, and is therefore a hydrate of potash. It may be obtained free from water by another process. Potash may be made to combine with a greater proportion of carbonic acid than in the state of sub-carbonate, by causing a stream of carbonic acid gas to pass through a solution of the latter salt : when this solution is then evaporated, it af- fords crystals of bi-carbonate of potash. This salt is milder than the subcarbonate, and its crystals are not deliquescent. POTASH. 81 Tlie fixed alkalies were, until lately, regarded as simple bodies, and one of the most brilliant disco- veries of modern chemistry has been that which showed them to be the oxides of peculiar metals. The decomposition of the alkalies was effected by means of voltaic electricity. By acting upon a very small piece of caustic potash, the metallic base was liberated, and proved to be solid, malleable, and having a high metallic lustre resembling mercury. This new metal is called potassium. It differs considerably in its properties from all the metals previously known. It is lighter than water, and has so strong an attraction for oxygen, that it almost instantly attracts it from the atmosphere and re- turns to the state of oxide. If thrown into water, it produces a very singular phenomenon ; it decom- poses the water so rapidly that an explosion takes place, accompanied by a flame. The same effect is seen if a globule of the metal is placed upon a piece of ice. This metal can only be preserved by keeping it under naphtha, a liquid that does not contain oxygen as one of its constituents. Potash combines with all the acids forming neu- tral salts. Nitrate of potash, called also nitre, or saltpetre, is produced in considerable quantities naturally, particularly in Egypt. It has also been produced artificially by making beds of animal and vegetable substances, mixed with calcareous and other earths. In process of time, an efflorescence of nitrate of potash appears, and is separated by lixiviation. By the decomposition of these substances, nitrogen is disengaged, which, uniting to the oxygen of the atmosphere, forms nitric acid ; and this uniting to the alkali furnished by the vegetables and soil, pro- duces the nitre. Nitrate of potash has the property VOL. II. G 8g SODA. of detonating when inflamed witli charcoal or other easily inflammable bodies. It is upon this property tlmt gunpowder is formed, which consists of five partsof nitrate of potash, one of charcoal, and one of sulphur. Chlorate of potash is formed by passing chlorine gas through a solu- tion of caustic potash. It is also called oxy-mu- riate of potash. This salt detonates violently when three parts of it mixed with one of sulphur are tri- turated in a mortar, or struck on an anvil. With phosphorus the effect is still greater. It makes a powerful gunpowder when employed as an ingre- dient. If a small quantity of it be mixed with some sugar, and sulphuric acid be added, a sudden and vehement inflammation will be produced. These experiments require great caution. SODA. This has also been called the fossil or mineral alkali, because supposed peculiar to the mineral kingdom. It is obtained chiefly from the ashes of marine plants; all the fuci yield it in abundance ; when burnt, their ashes are called kelp, which con- tains a considerable proportion of this alkali. Ba~ rilla is the same, procured by burning a plant of that name in Spain. Soda is also found in large quantities in different parts of the earth, particu- larly Egypt ; and common sea-salt consists of it united to muriatic acid. In all these cases, however, the soda is com- bined with carbonic acid. Of this there are two varieties, the carbonatey obtained by dissolving the soda of commerce and crystallizing it, and the bi- SODA. Hfi carhonate, obtained by passing a stream of" carbonic acid gas through a solution of the former. Soda and potash considerably resemble each other, but the former does not deliquesce so as to liquefy, as potash does ; its crystals, however, efflo- resce or fall to powder. It is used in the manufac- ture of soap and of glass. Soda, also, like potash, consists of a metallic base united t oxygen. The metal is called sodium. It resembles potassium in most of its properties. It unites with chlorine, forming chloride of potas- sium ; this is the common sea-salt so much used in food, and was, till lately, called muriate of soda. Common salt exists in immense quantities in na- ture, both in the form of a rock, as rock-salt, which is dug out of the earth in a solid form, and also dissolved in the sea^ from which it is obtained by evaporation. Common salt is decomposed by sulphuric acid. The sodium is converted into soda, by taking oxy- gen from the M^ater of the sulphuric acid, and the chlorine combines with the hydrogen of the water thus set free, and forms hydro-chloric acid gas^ which is the same with what has been called muri- atic acid gas. This gas, absorbed by water, forms muriatic acid. Hence, since muriatic acid was thus procured from sea-salt, it was supposed to exist in it, combined with soda, whence the name muriate of soda. Soda unites with all the acids, forming neutral salts, the most remarkable of which are the fol- lowing : — Sulphate ofsoda, called formerly Glauber's salts, is formed abundantly in the process for procuring the muriatic acid from common salt ; the sulphuric acid which is employed uniting to the soda. G 2 84 LITHIA. Borate ofsoda^ or borax, and P/fOsphaie of soda, useful as a test. The fixed alkalies readily combine with oils, and tluis form soap. Soap is soluble in water, and owes its detergent quality to the alkali contained in it. Alkali by itself would be too powerful, and would be apt to destroy the linen and other sub- stances to be cleaned. Soap when in solution is decomposed by acids, which unite with the alkali ; hence if an acid is contained in water, the soap curdles. Neutral salts formed by acids with bases of the earths pro- duce the same effect. Hard waters are such as have earthy salts, and are unfit for washing ; soft water is that which is quite free from salts. Hard soap is made from soda rendered caustic by lime, and olive-oil, or tallow. Soft soap is com- posed of potash and whale-oil. LITHIA. This alkali was lately discovered by M. Arfvred- son, a Swedish chemist. It is found to be a con- stituent of certain stones, and has been met with in the petalite, spodumen, and lepidolite. Jt is of the class of fixed alkalies ; is soluble in water, has an acrid taste, and changes vegetable blues to green. It forms neutral salts with the acids. Lithia, like the other fixed alkalies, has been found by analysis to be the oxide of a peculiar metal, which has been called Lithium. Its decom- position has been effected by the voltaic pile, but the quantity of metal obtained has been extremely small. 85 AMMONIA. This substance is known also by the name of the volatile alkali. It is composed of nitrogen and hydrogen. In its purest form it is in the gaseous state. It is then called ammoniacal gas. Ammoniacal gas is procured by adding dry quicklime to muriate of ammonia, and exposing them in a retort to the heat of a lamp. The mu- riatic acid, having a stronger attraction for the lime than it has for the ammonia, leaves the latter, which is disengaged, in the state of gas. A pneumatic apparatus is necessary for this purpose, as this gas is rapidly absorbed by water. Ammoniacal gas has a strong pungent smell, and suffocates animals immersed in it. It changes vegetable blues to green. If water be introduced into the apparatus, in contact with the gas, it absorbs it entirely, and acquires its peculiar smell : this is a solution of ammonia in water, and is called liquid ammonia. Ammonia exists as a constituent in animal bodies ; and it is obtained from bones, horns, &c. It is a valuable material in manufactiu'es and medicine. Ammonia forms with the acids several valuable compounds. With carbonic acid it forms carbonate and hi- carbonate of ammonia. The carbonate may be obtained by mixing ammoniacal gas with carbonic acid gas over mercury. The two gases inunedi- ately combine and form a solid white body, which still retains some of the pungent smell of the am- monia. This is the common smelBig salts. The bi-carbonate is procured by causing a current of carbonic acid gas to pass througli liquid ammonia. It has no smell. G S 86 EARTHS. Muriate of aynmonia wxi called sal ammoniac from its having been originally brought from the neighbourhood of the Temple of Jupiter Ammon. It is now abundantly prepared in this country by saturating carbonate of ammonia with sulphuric acid, which forms sulphate of ammonia : by de- composing this salt by muriate of soda, muriate of ammonia and sulphate of soda are obtained. Sal ammoniac is employed in many processes. EARTHS. At the first view it would seem, from the vast variety of soils on the surface of the globe, and the number of rocks and stony substances, that the different earths of which they are composed were innumerable : nevertheless, their number is very limited, and, by the mixture of these, the greatest part of mineral bodies is composed. The earths were formerly considered as ele- mentary substances, but late discoveries have shown that most of them are, like the alkalies, me- tallic oxides. It is found, however, more conve- nient still to consider them as a separate class. The earths are of two kinds : 1. Those which have some of the properties of alkalies and which are called alkaline earths. 2. Earths simply so called. The alkaline earths are, lime, magnesia, barytes, and strontia. They unite with acids forming com- pound salts as alkalies do : like tliem they change vegetable blues to green ; they have a considerable degree of causticity and taste, and are soluble in water. LIME. 87 The rest of the earths are insipid, and are scarce- ly at all soluble in water, and have no action on vegetable colours. I.IME. Lime is one of the most abundant substances in nature. It is the chief constituent in vast moun- tains and rocks, and is very generally distributed, mixed with other earths. Chalk, marble, calcare- ous spar, and all those rocks called lim.e-stones, con- sist of it. In these substances, however, the lime is not pure or uncombined. It exists in them united to carbonic acid, constituting carbonate of lime. To obtain pure lime, these stones are exposed to a white heat, by which the carbonic acid is driven off in the gaseous state. This is called the huriiing of lime. The stone so treated is then called quicIiHme; or, in chemical language, properly lime. Quicklime, or pure lime, is white ; has a hot acrid taste, and is caustic, or corrodes the skin. It changes vegetable blues to green. Until the discovery of the bases of the alkalies by Sir Humphry Davy, lime, as well as all the other earths, was considered as an elementary substance ; but it has been ascertained to be the oxide of a metal to which the name of calcium has been given. From the extreme difficulty, however, in reducing lime to this state, the properties of calcium are but little known. It is white and solid, resembling silver, and soon returns to the state of oxide or lime by attracting oxygen from the air. When water is thrown on quicklime just burnt, it swells, bursts, and falls to powder; giving out, at G 4 88 LIME. the same time, much steam and heat. This is called the slaking of lime. In this process, the water miites to the hme, and becomes soUd ; for slaked lime is quite dry. It is, therefore, called a hydrate of lime. Lime is soluble in water : the solution has an acrid taste, and is called lime-watei\ When lime- water is exposed to the air, a stony film forms upon the surface, owing to the lime attracting carbonic acid, and returning to the state of carbonate, which is insoluble in water. This film breaks, falls down, and is succeeded by others in succession. Fresh quicklime has a strong tendency to attract mois- ture from the air, and also carbonic acid, so that it must be kept in closely-stopped vessels. Quicklime is used for making mortar for build- ing, by mixing it with sand. This, by solidifying the water and attracting carbonic acid, becomes a very hard substance like stone. The lime should be newly burnt, and the sand silicious and free from impurities. It is also extremely valuable as a ma- nure when put upon the land. Carbonate of lime is not caustic, nor soluble in water. It is decomposed by the stronger acids. Put chalk or marble into a vessel, and pour upon it diluted sulphuric or muriatic acid ; an efferves- cence will ensue, which is owing to the escape of the carbonic acid. Hence these acids are em- ployed to distinguish lime-stones. Lime combines with phosphorus, forming j)hos- phuret of lime, to be afterwards described. With sulphur it forms siilphuret of lime. It also combines with all the acids, forming a great number of neutral salts. Sulphate of lime, called also gypsum, exists largely in a natural state. When burnt, it forms the sub. MAGNESIA. BAKYTES. 89 stance called plaster of Paris, so much employed in making casts of statues, and in plastering rooms. Filiate of lime, or lime united to the fluoric acid, is the substance so well known by the name of Der- byshire spar, and which is much used for vases and other ornaments. Nitrate of lime is a very soluble salt ; its taste is acrid and bitter. It is often found efflorescing on old plaster walls. MAGNESIA. This earth, when pure, is white, nearly destitute of taste and has no smell. It is insoluble in water, but changes vegetable blues to green, and unites to the acids. It is conjectured to be composed of a me- tallic base, magnesiumy united to oxygen ; but the metal has not yet been distinctly obtained. Native magnesia is a rare substance, but it en- ters as a constituent in many rocks, as serpentine, steatite, &c. Carbonate of magnesia is extensively employed as a medicine. When a red heat is applied to it it loses its carbonic acid, and becomes calcined magnesia. Sulphate of 7nagnesia is known by the name of Epsom salt, because formerly procured from the springs of Epsom, in Surrey. BARYTES. This earth was formerly called terra ponderosa, from its great specific gravity. It has strong alka- line properties, a caustic taste, and changes vege- table blues to green. 90 STRONTIA. SILICA. It slakes in the air like lime, is soluble in water, and also in alkohol, the flame of which it causes to assume a yellow colour. It is a deadly poison. It is also found to consist of oxygen and a metallic base called barium. Carbonate qfbarytes is found as a mineral, but it is not abundant. Sulphate of barytes is found native more fre- quently. When calcined, it forms the Bolognian 2)hosphorus. Barytes is used as a white paint under the name of permanent whiter not being liable to change its colour. STRONTIA. The name of this earth is derived from Strontian, in Argyllshire, in Scotland, where it was first dis- covered by Dr. Hope. It is soluble in water, and changes vegetable blues to green. It is also considered to be the oxide of a metal called str^ontium. Strontia is not very abundant, and is always in nature found combined with the carbonic or sul- phuric acids. The other salts of strontia are but little known. All the salts of Strontia have the property of tinge- ing the flame of alkohol red. SILICA. This earth, which forms a large portion of the surface of the earth, exists nearly pure in flint and rock-crystal : hence it has been called the earth of flints. It may be obtained pure as follows : calcine ALUMINA. 91 gun-flints tiil they become brittle, then pulverize them. Mix this powder with three or four times its weight of carbonate of potash, and fuse the mixture in a crucible, by a strong red heat. We shall thus obtain a compound of alkali and siliceous earth : dissolve it in water, and add to it diluted muriatic or sulphuric acid ; a precipitation will take place, which, when well washed, is pure silex. Siliceous earth, when pure, is white and tasteless. It is infusible by itself, and insoluble in water. It has a harsh feel, and does not form a cohesive mass with water. No acid can act upon it, except the hydro- fluoric, which dissolves it. When mixed with an equal weight of carbonate of potash, and fused in a strong furnace, it forms glass. With a larger pro- portion of alkali it forms a substance soluble in water, which has been called silicated alkali. The solution of this was called liquor ofjiints. The silex is precipitated from it in the state of a gelatinous hydrate by acids. It is supposed that silica consists of oxygen united to a certain base, which has been assumed to be a metallic substance, and w^liich has been called Silicium : but its real nature has not been ascertained. It is imagined, however, that silicium forms an alloy with iron, and that the properties of some sorts of iron are owing to the addition of this substance. ALUMINA. This earth forms a part of all clays, and hence has been called argillaceous earth. It exists also in nu- merous rocks, particularly slate, and even consti- tutes some of the hardest gems and stones, as the sapphire, ruby, and corundum. 92 CLAY. — YTTRIA. It rarely occurs in a pure unmixed state. But it has been found native, in small masses, at New- haven, in Sussex, and also in Hall, in Saxony. Clay consists of this earth, joined to silex. For- celain clay proceeds from the decomposition of felspar ; it consists of silica, alumina, and some- times a little lime and potash. Pipe-day^ and 'potters' 'day are pure clays, but of variable com- position. Alumina has no smell nor taste 5 is insoluble in water, but forms with it a ductile paste, and shrinks much when exposed to heat. It is dissolved by the liquid fixed alkalies, and unites chemically with barytes, strontia, lime, and magnesia. It is dis- solved by most of the acids. The salt called alum^ which gives its name to this earth, is a sulphate of alumina and potash. Sulphate of alumina alone will not crystallize ; but when sulphate of potash is added, octahedral crystals of alum are produced. When alum is exposed to heat, it loses part of the acid and water of crystal- lization, becomes light and spongy, and is called humt alum. Alum is extensively employed in the arts of dyeing and calico printing, in consequence of the attraction which alumina has for colouring matter. Alumina also forms the basis upon which are precipitated certain colours used as pigments. YTTRIA. This rare earth, so called from Ytterby, in Swe- den, where it was discovered, is found only in a stone called gadolinite, so named from Professor Gadolin. It is insipid, and insoluble in water, but dissolves in carbonate of ammonia. It forms salts Vd GLUCINA. — ■ZIRCONIA.— ^THORINA. 9^ which have a sweetish taste. Its specific gravity is greater than that of any other earth. The base of yttria has been supposed to be a metaUic substance, which would receive the name of yttrium ; but it lias never been exhibited in a separate state. Yttria contains oxygen, and hence been inferred to be a metallic oxide. GLUCINA. Ghicina, or Glucinej is an earth which has been procured only from the beryl, the emerald, and the euclase. It derives its name from its forming salts which have a sweetish taste. It has no taste nor smell, is infusible by heat, but dissolves in the acids, and pure alkalies. It is insoluble in water. It is also supposed to be a metallic oxide. ZIRCONIA. Zirconia is a very rare earth, found as yet only in the zircon or jargon of Ceylon, and the hyacinth. It is void of taste or smell ; is insoluble in water and pure alkalies ; but is soluble in alkaline car- bonates. Its base is supposed to be metallic. THORINA. This is another very rare earth, discovered by Berzelius, who extracted it from a species of gado- linite. It absorbs carbonic acid, and dissolves readily in acids. It is not soluble by the pure alkalies, but slightly so by the alkaline carbonates. It is supposed to be the oxide of a metal. 94, METALS. We come now to treat of the last division of the metaUic substances ; those which, remaining in the air in the metaUic state, have received the name particularly of metals. Those metals whose combinations with oxygen form alkalies, as potassium, sodium, and lithium, as also those whose oxides form earths, as calcium, magnesium, barium, strontium, silicium, alumium, yttrium, glucinum, zirconium, and thorinum, have been already mentioned incidentally, in speaking of the alkalies and earths to which they give rise. But we shall now enumerate the general properties of this important class of bodies, including the above mentioned. The metals are distinguished from all other sub- stances by certain properties, particularly a pecu- liar lustre ; and most of them have great weight, or specific gravity. Several of them have been known to part of the world in ^ery ancient times, while some savages in the present day are totally unacquainted with their use : but a considerable number of the metallic sub- stances have been discovered only lately. The metals are so important in many mechanic arts, that mankind could never have attained their pre- sent state of civilisation without them. Metals are, in general, solid bodies at the usual temperature : one only, mercury, is fluid. They are opaque in the mass in its usual state ; but gold, when beat into very thin leaves, transmits a faint greenish light, when held between the eye and the direct rays of the sun. METALS. Q5 Tlie lustre by which they are distinguished, called the metallic lustre, is not easily described, but may be exemplified in that of silver, steel, lead, tin, SiC, as distinguished from that of glass, diamond, &c. Mica has a lustre which approaches that called the metallic, but it loses this on being scratched, while the metals do not ; on the con- trary, they are more brilliant when fresh cut. This property of the metals renders them highly useful for ornamental purposes, and for reflecting light, as in mirrors. Metals are the best conductors of heat, and also of electricity. Some of the metals are capable of being extended under the blows of a hammer, which property is called malleahilityj and is peculiar to metals. Others, again, are brittle, on which account they were formerly called sejui-metals. The malleable metals are, gold, platina, silver, palladium, potas- sium, sodium, mercury in its frozen state, copper, iron, lead, tin, zinc, and nickel. These differ much in their degrees of malleability. Gold may be beat into the thinnest leaves, and zinc is very little malleable, except when heated. The malle- able metals are also ductile, or may be drawn out into wire. Gold and platina may be drawn into the finest wire. One of the metals, iron, is capable of being made very elastic, which renders it fit for making springs. Most of the metals are very fusible, or capable of being rendered fluid by the application of heat; on this account they may be cast into moulds, and formed into various utensils: some of the metals are volatile at a high degree of heat. None of them are very hard naturally ; but some 96 METALS. of them may be hardened by art: thus the moderns make cutting instruments of iron and steel, and the ancients made them of a combination of cop- per and tin. All the metals are capable of combining with oxygen, and thus forming oxides ; but they differ very much in the readiness with which they com- bine with it, which occasions their division into several classes. The oxides of metals have none of the metallic brilliancy, and no malleability : their appearance and nature are totally different from that of the metals themselves. The oxides of some metals, as potassium and so- dium, are alcaline ; others are acid, constituting the metallic acids : the rest have neither acid nor alca- line properties, but are, as well as others, capable of being dissolved by the acids, thus forming salts. Some of the metals attract oxygen so strongly, tliat they become oxidized almost immediately in the open air, and even take oxygen from all its combinations, so that they are, with great difficulty, preserved in the metallic state ; of this nature are metals that produce the alkalies and earths, which can only be kept in pure bitumen called naphtha, which has no oxygen in its composition. Some of the metals do not experience any change on being kept in fusion by a strong heat with an access of air ; but others are by this means converted into oxides. The first have been called perfect metals, and comprehend gold, platina, sil- ver, and palladium. The rest differ very much in the degree of heat necessary to oxidize them. Arsenic, manganese, and the bases of the earths and alkalies become oxides at the usual temperature of the atmosphere, even when perfectly dry. Lead METALS. 97 and copper are oxidized slowly by moist air. Iron, zinc, copper, tin, &e., require to be heated to red- ness. Although the perfect metals cannot be oxidized by any degree of ordinary heat, they may by the effect of electricity and galvanism. All the metals, that are converted into oxides by atmo- spheric air, undergo this change still more rapidly in oxygen gas, as was shown in the burning of iron wire in oxygen. Metals are also converted into oxides by the ac- tion of acids, but in different manners. Some acids which contain oxygen loosely combined part with it to the metal ; while others, as the sulphuric and muriatic acids, do not act upon iron or zinc, except they are diluted with water, and then it is the wa- ter, and not the acid, which supplies the oxygen. Metals cannot be made to combine with all pro- portions of oxygen, but are susceptible only of cer- tain degrees or stages of oxidation. Thus iron has only two oxides j the black oa:ide composed of 29.5 parts of oxygen, and 100 parts metal ; and the red oxide of 43.5 parts of oxygen, and 100 parts of metal : and there are no intermediate degrees of oxidation, nor will iron combine with a larger or smaller proportion of oxygen. Metals differ in the number of oxides which they form : thus some have two, some three, and others four oxides : and, according to the law of the atomic theory, the different oxides of the same metal contain oxy- gen in proportions that are simple multiples of each other. The different oxides of the same metals have dif- ferent colours, which render them very valuable as pigments. They have also distinct chemical pro- perties, and combine, in different proportions, with the acids, forming distinct salts. VOL. II. II 98 PLATINA. All the metals are considered as simple bodies, none having been decomposed or resolved into other principles ; also, at one time, they were sup- posed to be formed of a peculiar basis and an ima- ginary inflammable principle called plilogisto7i. This theory was very favourable to the idea of forming metals, and transmuting or changing them into each other. The existence of phlogiston is no longer believed in, and the science of alchemy is only remembered as affording an instance of the dangers of false theories, and of the great credulity of persons in many respects well informed. The oxide of a metal was formerly called a cal^r^ and its conversion was supposed to be owing to the loss of the phlogiston ; but it was observed that the metal gained instead of losing weight by this change ; in fact, it acquires just the weight of the oxygen it combines with. When the oxides of me- tals are made to part with their oxygen, hey are reduced to the metallic state, and upon this depends the art of reducing metals from their ores. PLATINA. This metal was unknown in Europe before 1748, and is still chiefly found in South America : it has been also found in Estremedura, in Old Spain. In colour it is nearly as white as silver. It is very difficult of fusion, and can only be melted by the assistance of oxygen gas or by galvanic elec- tricity. From its refractory quality, it is employed for crucibles and other chemical utensils exposed to heat, for which it is admirably adapted. It is also extremely ductile and malleable, and may be drawn into very thin wire, and hammered into thin plates. GOLD. 99 Platina does not tarnish on exposure to the at- mosphere, and takes an excellent polish, on which account it is used in making specula for telescopes. It is also capable of being welded, a property only possessed by it and iron. It is the heaviest of the metals ; its specific gravity being nearly 22. Platina is readily dissolved by the nitro-muri- atic acid and by chlorine, but is not acted upon by any other acid. It also combines with sulphur and phosphorus. Platina is brought to Europe in small flattened grains, which, however, are not pure platina, but contain a mixture also of nine other metals. Four metals, osmium^ iridhmiy rhodhwiy and palladium, were unknown till they were discovered in these gi'ains. GOLD. Gold is found in nature in a metallic state. It is generally met with in grains called gold-dust, mixed with the sands of rivers, either b^ng carried away by them from the rocks which contain it, or having been deposited in ancient alluvium. It is chiefly found in Africa, also in Brazil and Peru. There are mines of it also in Hungary ; and it is met with in quantities too small to be worth work- ing, in the sands of many rivers of Europe. Lately some was found in the county of Wick- low, in Ireland ; one grain weighed 22 ounces, and considerable expectations were formed ; but, not- withstanding, the works were abandoned as unpro- ductive. Gold is the heaviest of the metals except platina. It is of a rich yellow colour, and not ^ ery hard when pure. II 2 100 ' GOLD. It melts at a bright red heat, but cannot be oxi- dated by any furnace, though it may by electricity and galvanism. It does not oxidate in the air ; hence it is so useful in gilding, its beautiful lustre remaining untarnished. It is the most ductile and malleable of the me- tals, and may be drawn into the finest wire for gold- lace and other purposes, and may also be hammered into leaves of extreme thinness for gilding. Gold is not acted on by any acid except the nitro-muriatic acid and chlorine. From this pro- perty the former was named aqua-regia^ gold being called by the alchemists the king of the metals. The solution of gold, called muriate of gold, yields by evaporation crystals of a beautiful yellow co- lour, which, when dissolved in water and precipi- tated by a solution of tin, afford the beautiful pow- der called the purple precipitate qfcassiuSy much used in enamelling. This consists of oxide of gold mixed with oxide of tin. If any substance, as a piece of ribband, be dipped into the muriate of gold, and then exposed to a stream of hydrogen gas, the gold will be revived, and the substance covered with it. Some com- bustible bodies attract the oxygen from the solu- tion of gold, and cause it re-appear in its metallic state. Thus, if a piece of charcoal be put into a glass-jar containing a diluted solution of gold, and exposed to the direct rays of the sun, it will soon appear gilt. When ammonia is added to a solution of gold, a yellow precipitate is formed, called ^ful- minating gold, because it has the property of ex- ploding when exposed to heat. If to a solution of muriate of gold, sulphuric ether be added, the gold will combine with the ether, 15 leaving the acid, and wilt float on the surface of the fluid. If pohshed steel be dipped into this, it will be covered with a coating of metallic gold. This process is employed for gilding lancets, and other surgical instruments, to defend them from rust. Gold easily alloys with mercury, which is, there- fore, much employed for extracting it from the substances with which it is mixed in its natural state. The mercury, being volatile, is driven off by heat, and the gold remains free. Gold in its purest state is too soft to be used as coin ; it is, therefore, alloyed with n of copper. Jeweller's gold generally contains considerably more. Gold seems to have been one of the earliest known of the metals. The ancients were lavish in its use, and it is still frequently used in orna- ments among savage tribes. SILVER. Silver is often found native, or in the metallic state, but it is most usually combined with other metals, or sulphur. In its native state it fre- quently assumes an arborescent form. The richest silver mines are in Mexico and Peru ; but others exist in many countries. Lead ore very frequently contains a quantity of silver, and sometimes it is worth extracting. Silver is of a brilliant white colour. It is very ductile and malleable ; may be drawn into fine wire, and beaten into thin leaves ; but it is inferior to gold in these qualities. Silver fuses when heated red hot, and may be cast into moulds, but is not thus converted into oxide H 3 lOi . SILVER. by any continuance of heat: it is oxidized by common and galvanic electricity. It is not oxidized by the air ; but it is tarnished by exposure, because the sulphurous vapours form with the metal a sulphuret of silver. Oxide of silver is of a dark olive colour, and is obtained by precipitating it from the nitrate of silver by lime-water, this metal being soluble in the nitric acid. Nitric acid can dissolve more than half its weight of silver, the solution depositing crystals. When these are fused by a gentle heat, they may be poured into moulds, and form the substance called luna7' caustic^ used in surgery. Nitrate of silver is used by chemists as a test for muriatic acid; for if it be dropped into any liquid containing muriatic acid, a white precipi- tate will appear, owing to the superior affinity of silver to muriatic acid, and to the insolubility of muriate of silver. Nitrate of silver is very caustic, staining animal and vegetable substances of a black colour, and hence it is employed as a ]ier- 7na7ient marking ink for linen, and also for staining hair ; though for this last purpose it should be used with great caution, and much diluted. If a few drops of the nitrate of silver be put upon a piece of glass, and a copper wire be placed in it, a beautiful metallic precipitation of the silver will appear in an arborescent form. When silver is precipitated from its solution in nitric acid by ammonia, it forms fulminating silver, M'hich is a dangerous preparation ; for it explodes by the slight contact of a body. When mercury is added to the nitric solution of silver, a precipitation of metallic silver is Ibrmed MERCURY. 103 resembling in appearance a vegetation, and called arbo7' Diance. Silver is not soluble in the hydro-chloric acid (muriatic acid), yet, when this acid is added to a solution of nitrate of silver, it unites to the oxide, and a white curdy precipitate falls down, which is the muriate of silver^ or, in conformity with the new nomenclature, tlie chloride of silver. If this precipitate be fused by a gentle heat, a semi-trans- parent mass is formed, called formerly lima cornea^ or horn silvery the fused muriate of silver* Silver is also dissolved by the sulphuric acid, and the sulphate of silver is used as a chemical test. Silver also unites to sulphur and phosphorus. Silver, when employed for coin is alloyed with copper to increase its hardness. Our coin con- tains thirty-seven parts silver and three parts copper. MERCURY. This metal, called also quicksilver^ is always fluid when in the usual temperature of the atmosphere ; but when exposed to an intense degree of cold, it is frozen into a solid mass, and is then malleable. The temperature necessary for this purpose is 39*^. The cold is sometimes so great within the polar circle as to freeze the mercury in the thermometer ; but in this country that can only be effected by exposing it to a freezing mixture. Mercury also boils at 655°, and then evaporates, and may be distilled from one vessel to another. It is sometimes found in nature in a pure state, but usually it is united to sulphur, with which it H 4 104 IRON. forms the ore called finnabar. The greatest quan- tity of it is found in Spain and South America. When acted on by heat and air for a long time, it absorbs oxygen, and is converted into a red oxide called formerly precipitate per se : and when the heat is increased, the oxygen is given out, and the mercury re-assumes its metallic appearance. When it is agitated long in air, it is converted into the black occidcy which contains a smaller propor- tion of oxygen than the red oxide. It is the black' oxide which is employed in mercurial ointment. Mercury is acted on by the acids, forming salts of mercury. It also unites to chlorine (oxymuriatic acid,) in two proportions, forming calomel and cor- rosive sublimate. Mercury when triturated with sulphur, com- bines readily into a black compound called ethiops mineral ; when united to a larger proportion of sulphur, it forms the beautiful pigment called cinnabar. Mercury combines with several of the metals, forming soft alloys called amalgams. The amal- gam with tin is used for mirrors : that with zinc is employed in electrical machines. IRON. ISIo metal is so universally diffused throughout nature as iron. It is never found in the earth in the metallic state, but is always procured from ores. Iron is of a bluish-grey colour. It is very duc- tile, for it may be drawn into wire as fine as human hair. It is also very malleable, and pos- IRON. 105 sesses the property of being welded; that is, of having two separate pieces united together by hammering when red hot. It is one of the most infusible of the metals, but may by intense heat be melted and run into moulds. It is in its pure state among the hardest of the metals, but may be made to exceed all the rest in hardness when converted into steel. It possesses the magnetic property, the load' stone itself being an ore of iron. Exposed to the action of the air and moisture, iron soon rusts or OTidates. It then attracts the oxygen and carbonic acid, and is changed into a reddish brown substance, which is a mixture of oxide of iron and carbonate of iron. Iron unites to oxygen in two proportions. The protoxide of iron consists of one hundred parts of iron, and twenty-nine parts oxygen ; it is of a black colour ; hence it is called the black oxide of irony formerly martial ethiops. It is formed when iron is heated red hot ; scales form on the outside, which fly off when hammered. It is magnetic. The peroxide is red, and consists of one hundred parts iron, and forty-three oxygen ; it is called the red oxide of iron. The red oxide is formed by keeping iron filings red hot in an open vessel, and agitating them constantly till they are converted into a dark red powder, formerly called saffron of Mars. Iron is acted on by all the acids, and various salts of iron are formed : the most remarkable are the following : — Sulphate of irony formerly called copperas or green vitriol. Nitrate of iroUy and acetite of irdiiy used in dying. 106 IRON. FerrO'prussiale qfirorij called prussian blue, used as a pigment. Iron also combines with sulphur, phosphorus, carbon, chlorine, and iodine. Sulphuret of iron, composed of sulphur and iron, is called also pyrites. Iron with carbon forms plum- hago, commonly called blach-lead, used for making pencils. Steel is another compound of iron with carbon. The ores of iron consist either of the black ox- ide, which is called the magnetic iron oi^e, the red oxide or the i^ed iro7i ot^e, carbonate of iron, and clay ironstone. The iron is separated from these ores by smelting in furnaces, where it is made to flow out into va- rious moulds made in a kind of loam. The first pro- duct is called cast iro7i. It contains some carbon and oxygen ; and, it is thought, also silicium, besides casual impurities. Of this, cannon, pipes, grates, and other articles of cast iron are made. It is of two kinds : "white cast-iron is very brittle ; grey cast iron is less brittle, though not malleable, but may be bored and turned in the lathe. To render iron malleable it must be freed from those substances with which it is combined in the crude state. To effect this, it is kept in fusion in a furnace exposed to air and flame, and well stired. The oxygen combines with the carbon, and escapes in the form of carbonic acid gas ; and the earthy matter is vitrified, and rises to the surface as slag. It is then subjected to the action of large hammers and rollers, by which the remainder of the impuri- ties is forced out. It then constitutes bar iron, also called 'wrought iron, fit for manufacturing. AVr.ought iron is of a fibrous structure, and is the metal in a pure slate. It is now extremely malle- IRON. 107 able, soft, and easily filed, and also capable of being forged and welded. There are several va- rieties of iron in this state, arising from the ores from which they were procured, the process of smelting, or the intermixture of foreign substances. One variety is called hot sJiort iron ; it is ex- tremely ductile when cold, and on this account is employed for making wire ; but when heated it is extremely brittle : it is also fusible. Cold short iron, on the contrary, is highly ductile when hot, but brittle when cold. The causes of these qualities are not precisely known, but it is said that the first is iron combined with arsenic, and that the latter contains phosphoric acid. Iron is capable of being reduced to a third state, which is that of steel. It is converted into steel, by exposing it to heat in contact with carbonaceous substances, which unite themselves with it. Steel is, therefore, iron united to carbon, and is made by three processes. Natural steel is made by keeping cast iron in a state of fusion in a furnace, its surface being all the while covered deep with scoriee ; part of the carbonic acid gas escapes, while another part com- bines with the iron. This steel is inferior to the other kinds. Steel of cementatmi is made by placing bars of iron in charcoal powder, and exposing them to a strong heat in a furnace for six or eight days. The iron and the carbon thus combined constitute what is here called blistered steel. When this is rendered more malleable by the operation of the hammer, it is called sheer steel. Cast steel is made by fusing bhstered steel with pounded glass and charcoal powder, in a close cru- cible. It is also made merely by fusing iron with 108 IRON. carbonate of lime. This is the most useful of all the kinds of steel, and employed for razors, surgeons*" instruments, and similar purposes ; its grain is the most compact, and it takes the highest polish. It is the particular property of steel to become extremely hard, if it be heated red hot, and then suddenly plunged into cold water ; but different instruments made of steel require to be of different degrees of hardness ; and they are, therefore, sub- jected to a process called tempering ^ which is heat- ing them again to a certain point after having been hardened. The tempering of steel, for some pur- poses, is a delicate process. A polished bit of steel, when heated with access of air, acquires very beautiful colours. It first be- comes of a pale yellow, then of a deeper yellow, next reddish, then deep blue, and at last bright blue. At this period it becomes red hot, and the colours disappear: at the same time the metallic scales, or the black imperfect oxide of iron which is formed, incrusts its surface. All these different shades of colour indicate the different tempers the steel has acquired by the increase of heat. Artists have availed themselves of this property, to give to surgical and other instruments those degrees of temper which their various uses require. Iron may be alloyed with most of the metals, but these alloys are not much used. Wootz is the name given to a kind of steel made in the East Indies, which is of a very superior quality for cutting-instruments. 109 COPPER. Copper is sometimes found native, but in very small quantities. It is generally met with in the state of oxide, or united to sulphur, or to acids. In Cornwall there are very rich mines of copper. Pure copper is of a red colour, very tenacious, ductile, and malleable. It melts at 27 of Wedge- wood's pyrometer, and burns with a green flame. It is not oxided by water. When exposed to a red heat, it becomes covered with a crust of oxide of a blackish colour, this is the peroa:ide of copper. The fir»t, or protoxide^ is of a red colour when found native,but when formed artificially is orange. The oxides of copper are reduced to the metal- lic state by heating with charcoal or oils. The nitric acid disolves copper with efferves- cence, and the solution has a blue colour. The acid first oxidates the metal, a large quantity of nitric oxide (nitrous gas), is disengaged, and the oxide dissolves ; this forms the nitrate of copper. The sulphuric acid does not dissolve copper un- less when concentrated, and in a boiling state. Fine blue crystals, which are the sulphate of copper, are the result. This is what is commonly called blue vitriol. This salt is decomposed by iron ; for if a piece of iron be immersed in a solution of sul- phate of copper, the copper will be precipitated upon the iron. This process is often employed for procuring the copper from the water ir copper mines, which has in it a large portion of sulphate of copper. The muriatic acid does not act upon copper ex- cept in a state of ebullition, and then the muriate 110 COPPER. of copper is formed, which is of a green colour, and of an astringent taste. A solution of it is used as a sympathetic ink ; for letters written with it will become yellow by warming, and will disappear again when cool. The acetous acid in a sufficient degree of con- centration dissolves copper, but when not concen- trated, as in vinegar, it acts upon it very slowly, and forms common verdigris, which is an impure acetate of copper. This being dissolved in distilled vinegar, and subjected to evaporation, crystals are produced which constitute what is called distilled verdigris. Copper is employed in making kitchen utensils ; but as these vessels are liable to be corroded by the acids and fatty substances used in culinary preparations, they often become dangerous, as all the salts of copper are poisonous. Culinary utensils of copper should always be well tinned, but those of iron tinned are safer, as iron has no poisonous quality. The alloys of copper with other metals are very useful. Tombac is formed of copper, arsenic, and tin. Prince's metal, or Pinchbeck, is made of copper and zinc. Brass is also formed of another proportion of copper and zinc. Bronze is made of copper and tin. Bell-metal is also of copper and tin, but with more tin than the latter alloy. A solder for silver is made of copper and silver. Ill TIN. Tin is a metal of a colour approaching to that of silver, but somewhat duller. It is extremely malle- able. When hammered into leaves it constitutes tin-foil. It is not, however, very ductile. It is nearly as soft as lead, and may be easily bent, and then emits a crackling noise, which is peculiar to it. Tin fuses more easily than any other metal : when it has been kept some time in a state of fiision, with access of air, its surface becomes wrinkled and covered with a grey pellicle, which is the Jirstj or grey oxide of tin. This oxide when mixed with melted glass forms white enamel. The grey oxide, when exposed to a greater degree of heat, takes fire, acquires more oxygen, and becomes of a pure white ; the white oaide of tin. Tin is not oxidized in the air at the common temperature ; on account of which property, it is used for covering iron plates, to prevent tlieir rusting. Tin dissolves in the muriatic acid, forming muri- ate of tin, much used by dyers. With nitric acid it forms nitrate of tin. Tin united with sulphur forms the aurum mus- turn. Alloyed with lead, it forms plumber's solder. The best pewter is composed of tin alloyed with antimony, copper, and bismuth. Tin is not found native, and its ores are not much distributed. The richest mines are in Cornwall. LEAD. This metal is never found in a native state. The ore from which it is chiefly procured is galena^ which is lead united to sulphur, or a sulplntrel of lead. 112 ' LEAD. Pure lead is of a greyish colour. When fresh cut it is bright, but it soon tarnishes in the air. It stains the fingers or paper when rubbed on them. It is easily cut with the knife; has little or no elas- ticity, and is very malleable, but not very ductile. Water does not act upon lead. It easily fuses ; and exposed to the air in a state of fusion, its surface becomes covered with a grey pellicle: if this be removed another succeeds, and in this manner the whole may be converted into a powdery substance. This pellicle is composed of oxide of lead mixed with a portion of metallic lead. If it be subjected to a strong heat, it is changed into a yellow powder, known by the name of massicot ; which is the Jirst, or yellow oxide of lead : it is used as a pigment. If massicot be exposed to the flame of a furnace for some time, and kept stirred, it is converted into a beautiful pigment, called minium^ or red lead. This has been called the red oxide of lead ; but it is a mixture of the yellow oxide above mentioned, and another, the brown oxide of lead. This brown oxide may be procured by pouring nitric acid on red lead j when the yellow oxide in the red lead will be dissolved by the acid, and the brown oxide will remain, being insoluble. If the oxides of lead be acted on by a strong- heat, they give up their oxygen, and metallic lead remains ; but they are more readily reduced by mixing them with combustible matter. Lead, when procured from its ore, frequently contains so much silver, that the latter is wortli extracting. This process is called refining. Tlie lead is played upon by the flame of a furnace, by which the lead is oxidized, and the oxide is partly vitrified, and assumes a scaly form, called litharge. The silver then remains free. LEAD. 113 The oxides of lead are easily changed into glass, and unite with all the metals except gold and silver; on this account they are employed for separating other metals from these. This process is called cupellation. The mixed metal is put into a dish called a cupel^ made of bone-ashes, and placed in a cupelling furnace ; the lead is oxidized and vitri- fied, and sinks into the bone-ash cupel, carrying with it all the baser metals. White lead, so much used in painting, is a com- pound of the yellow oxide and carbonic acid ; or a carbonate of lead. It is made by exposing plates of pure lead to the warm vapour of vinegar. By this they are gradually corroded, and converted into a heavy white powder, which is white lead. When the carbonate of lead is dissolved in dis- tilled vinegar, a salt is obtained, which crystallizes, and is called commonly sugar of lead; more pro- perly acetate of lead. All the salts of lead have a sweetish taste, and are of a poisonous quality. The affinity of the muriatic acid (hydrochloric acid) for the oxides of lead is so great, that the latter decomposes all the combinations of this acid. They decompose the muriate of soda (common salt), and thus form muriate of lead, which, on fusion, affords minei^al oy patent yelloxv. Sulphuric acid does not act on lead when cold; but dissolves it at a boiling heat, and forms sul- phate of lead, which is insoluble in water. Chr ornate of lead , or chromic acid and lead, is a very beautiful yellow pigment. It is found native in small quantities, but is now prepared largely by art. Lead is one of the most useful metals. It is much employed in covering houses, when made into thin sheets by casting or by milling. It is used also for water-pipes and cisterns, and for a variety VOL. II. I Il4 ZINC. of well-known purposes. Its oxides are used in the manufactures of glass, and the glazings of earthenware; also as pigments. Preparations of lead are also used as external applications in diseases. The alloys of lead with tin form solder, and other alloys are employed in various arts. ZINC. This metal is chiefly procured from calamine^ which is a liydy^ated oxide of zinc ; and from blende, a sulphuret of zinc. Zinc is a whitish metal of the colour of tin. It is slightly malleable when cold ; but heated to between 200° and 300° it is very malleable, and has been manufactured into nails, drawn into wire, and made into sheets. It is often known among workmen by the name of Spelter, It is easily fused, and is the most in- flammable of the metals; thin leaves of it will take fire with the flame of a taper. It is scarcely oxidized in the air at common temperatures, but is rapidly converted into oxide when kept melted in an open vessel. Its surface then becomes covered with a grey pellicle, which is oxide of zinc. When zinc is made red hot in an open vessel, it takes fire and burns with a brilliant flame, sending off white flakes of oxide. These have been calledj^ower^ of zinc. Zinc decomposes water very slowly when cold ; but with great rapidity when the vapour of water is brought into contact with it ignited. Zinc dissolves very readily in diluted sulphuric acid; forming thus sulphate of zinc, or "white vitrioL During this solution, a great quantity of hydrogen ANTIMONY. 115 gas is disengaged, and this is one of the best modes of procuring that gas. The nitric and muriatic acids also act upon zinc. Zinc combines with phosphorus and sulphur. It can be alloyed with most of the other metals. With copper, it forms brass, ANTIMONY. Antimony is rarely found native. It is procured from an ore called crude antimony, which is a sul- phuret of antimony. Antimony is of a silvery white colour. It is so brittle, that it may be pulverised in a mortar ; and its interior texture appears to be scaly or lamellar. It requires 800° to fuse it. It does not change in the air, but when kept in fusion at a red heat, it emits white fumes, consisting of an oxide formerly called^oa;er5 of antimony. There are two oxides of antimony. The protox- ide is procured by precipitating the muriate of antimony by potash. It is of a grey colour. The peroxide is formed by causing the nitric acid to act upon the metal, or by collecting the fumes already mentioned as the flowers of antimony. It is white. The oxidesof antimony are very valuable medicines. Tartrate of potash and antimony form emetic tartar, Jameses powder is composed of phosphate of lime and antimony. Kermes*s mineral is made from sul- phuret of antimony by potash. Antimony is also used in printers' types ; and in specula for telescopes. The sulphuret has been used for staining hair black. 116 BISMUTH. — ARSENIC. BISMUTH. Bismuth is found native, and also combined with sulphur and arsenic. It is of a reddish white colour, brittle, and easily fusible. It is not quite so hard as copper. It is not oxidated by water; it tarnishes in the air, but does not undergo any other change. Kept melted in an open vessel, its surface becomes covered with a dark grey pellicle, which is renewed till the whole is converted into oxide. The oxide of bismuth is a yellow powder. When strongly heated it melts and becomes darker coloured. Bismuth dissolved in the nitric acid, affords a white powder, if water be added to the solution. This is the magistry of bismuth^ ov pearl 'white, which has been used as a cosmetic, but very improperly, as it is apt to turn black by sulphuretted hydrogen. Bismuth dissolved by the acetic acid forms a sympathetic ink. The characters written with it are invisible, until they are exposed to sulphuretted hydrogen, when they appear black. Bismuth alloys with all the metals, and has the property of giving them great fusibility. If eight parts of bismuth, five of lead, and three of tin be fused together, they form what is called the fusible metal, which melts in boiling water. On this ac- count bismuth enters into the composition of some of the soft solders. It has also the property of rendering gold ex- tremely brittle. ARSENIC. Arsenic, the poisonous effects of which are so well known, is a metallic substance, sometimes NICKEL. 117 found native, but oftener combined with sulphur. The sulphuret of arsenic is called orpiment. Arsenic is frequently mixed in metallic ores, and is driven off by heat. It is known by its pecu- liar smell, like garlic. The colour of metallic arsenic is grey; it is very brittle. It soon loses its metallic lustre in the air, and becomes black. The oxides of arsenic have acid properties. There are two: the white oxide of arsenic is called arsenious acid. It is highly poisonous. It is soluble in water. It reddens vegetable blues. It is of a white colour, is semi- transparent, and brittle. Its taste is acrid, with a nauseous sweetness. The best way of getting rid of its action as a poison, when taken into the sto- mach, is to produce vomiting and purging. Arsenic acid is a white deliquescent substance, of a sour taste, obtained by distilling nitric acid off metallic arsenic. It forms salts with several of the metals. Arseniate of iron crystallizes in cubes of a green colour. The arseniates of copper are among the most beautiful minerals. The alloys of arsenic with some of the metals are used for some purposes. It is mixed with lead to assist its granulation in making small shot. It is also used in making flint glass, and in calico-printing. NICKEL. Nickel is a rare metal. It is white, much resem- bling silver*, and possesses, like iron, the magnetic property. It is not easily fused, and it is malleable. It is rather softer than iron, and soon tarnishes in the air. It is found native, and combined with arsenic. Nickel dissolves in the acids, and its salts are distinguished by their fine green colour. I 3 us ivAnganese. It forms two oxides, the black and the grey. Nickel alloys with most of the metals, and it is found alloyed with iron in those masses that fall from the atmosphere, called meteoric stones. The origin of those lapideous masses that appear in so extraordinary a manner is entirely unknown: but the numerous well-authenticated accounts we have had of the fact put it now beyond dispute. They are first seen as large meteors, at a great height in the air, which suddenly burst with an explosion, and the fragments are seen to fall to the earth. It is very remarkable that their composition is always the same, although they have fallen at many difter- ent times, ,and in different places. They always contain native iron alloyed with nickel, in grains imbedded in a stony matter. The substance of these meteoric stones is not like any bodies which are found in the earth. In 1795, one weighing 56 lbs. fell in Yorkshire. MANGANESE. This metal is never found native. Indeed its attraction for oxygen is so powerful, that it is with difficulty preserved in the metalHc state. When pure, it is of a greyish colour, much like cast iron, and not malleable. It soon tarnishes, and at last becomes black. This change takes place more rapidly, if the metal be heated, or put into water. There appear to be two oxides of this metal ; the protoxide^ which is of a greenish colour ; and the peroxide, which is steel black, and has a consi- derable lustre: the latter is found in abundance, particularly near Exeter, and is much used in bleaching, and also for procuring oxygen gas, as it parts with it simply by the application of heat. It COBALT. 119 contains one-third of its weight of oxygen. This oxide is sometimes very beautifully crystallized. Manganese is also employed by glass-makers to destroy the greenish tint of glass, and for making violet-coloured glass. Almost all the salts of manganese are soluble in water. COBALT. Cobalt is never found but in a state of combin- ation. It is met with united to sulphur, arsenic, and other metallic substances. The ores of cobalt had been long used for giving a blue colour to glass, before its metallic nature was known. The metal itself is not applied to any use. When pure, it is a reddish grey colour ; rather soft and brittle. Like iron, it is attracted by the magnet. It is not oxidized by the air nor by water. It is converted into a deep blue by exposure to heat and flame. There are two oxides of cobalt. The 'protoxide may be formed by precipitating by potass, a solu- tion of cobalt in nitric acid. It is of a blue colour when first precipitated, but becomes black by absorbing oxygen. To recover the blue colour, it must be heated red hot, by which the oxygen is expelled. This oxide dissolves in acids. The mu- riate of cobalt is green, and forms a sympathetic ink. Letters written with it are invisible, until they are warmed, and then they appear of a fine green j when cold they disappear again. The peroxide of cobalt is procured by drying in the air, with heat, the protoxide just precipitated; by this the protoxide absorbs oxygen, and becomes the peroxide. It is black. I 4 120 MOLYBDENA. — TUNGSTEN. Ores of cobalt are very valuable. Zaffre is a substance produced by roasting the ores of cobalt, by which the volatile matters (generally arsenic and sulphur,) are driven off; the remainder is then fused with sand or pounded flints. A blue glass is thus formed, which, when ground and washed, con- stitutes the pigment called smalt. MOLYBDENA, Molybdena is found in nature combined with sulphur; forming the sulphuret of molybdena, which resembles plumbago in some of its properties. This mineral is of a bluish colour, more brilliant than plumbago, and makes on paper a trace of a grey tint. The metal has only been procured in small grains, which do not differ much in their pro- perties from the sulphuret. It combines with oxygen, so as to form an acid called the molybdic acid. The molyhdate of lead is a beautiful yellow mineral. The protoxide of molybdena is a tasteless pow- der of a brown colour. Molybdena alloys with the other metals, TUNGSTEN. A mineral called tungsten^ or ponderous stone, affords a peculiar metal. This metal is capable of being acidified, and when in this state it is joined to lime, it forms the tungstate of lime. The metal when pure is much like steel, and is one of the hardest of the metals; a file can scarcely make any impression on, it : it is also the heaviest, OSMIUM. — IRIDIUM.— RHODIUM, 121 except gold and platinum. It is not used for any purpose. When heated in an open vessel it is oxidized, and there are two oxides of tungsten. The pro- toxide is of a brown colour, and when heated it burns, and is converted into the peroxide^ which is yellow, and has some of the properties of an acid, being capable of combining with salifiable bases. The mineral called wolfram is composed of tungstic acid, manganese, iron, and tin. OSMIUM. This metal was discovered by Mr. Tennant, in the ore of platina. The metal is of a dark grey colour, and is oxidized when heated. Its oxide is volatile, and has a peculiar smell. It is little known, and has not been fused. IRIDIUM. This metal was also discovered by Mr. Tennant, in the ore of platina. It is of a wliitish colour. It is fusible, and malleable. It unites with oxygen, and alloys with the metals. Its combinations are little known. RHODIUM. Dr. WoUaston discovered this metal in the ore of platina. It is very infusible, and forms malleable alloys with the malleable metals. It unites to oxygen like all the other metals, but is very little known. Igg PALI,AI)IUM.«- CADMIUM. -—TEJLiUmUM. PALLADIUM. This metal was discovered by Dr. WoUaston, who found it in the ore of platina. Its colour is of a duller white than platina ; it is malleable and ductile, and for fusion it requires a stronger heat than for gold. It is rather harder than iron. It unites with sulphur, and is acted on by the acids, but most readily by the nitro-muriatic. It forms alloys with other metals, that with gold has been usefully employed in astronomical instruments, as it is hard, and does not tarnish. CADMIUM. This metal was discovered by M. Stromeyer, in 1817> in ores of zinc, particularly in brown fibrous blende. It resembles tin, but is rather more fusi- ble. It does not tarnish in the air. It readily disolves in acids, but its salts are lit- tle known. It is a rare metal, and not applied to any use. TELLURIUM. This metal was discovered by Muller in 1782. It is of a bluish w^hite colour, of considerable bril- liancy. It is extremely brittle ; melts in a heat a little greater than that required for lead. It is so volatile that it may be distilled like mercury. Its oxide has acid properties. It is formed by burning the metal j a white smoke is disengaged, which is the oxide. It may be also obtained by TJTANIUM.'— CHROMIUM. 123 dissolving the metal in nitromuriatic acid, and di- luting the solution with a large quantity of water. Tellurium combines with hydrogen, and with it forms a gaseous substance, called telluretted hy- drogen. This metal is scarce, and its combinations yet little known. TITANIUM. This metal is rare. It was discovered in a mineral, found in Cornwall, called menachanite. It was afterwards procured from another mineral, titanite, and some others. The metal when pure is brittle, very infusible, of a brass or copper co- lour, easily tarnishes in the air, and oxidizes by heat. There appear to be three oxides of titanium, the blue, the red, and the xvhite. The ores of titanium are either pure crystallized oxide, or the oxide united to iron, or to silex. CHROMIUM. This substance, little known in the metallic state, is important on account of the fine pigments it affords. It is capable of being acidified, and the chromic acid forms salts. The beautiful mineral called red-lead of Siberia, is a chromate of lead. This is now artificially prepared, and is a very va- luable and beautiful yellow pigment. The chro- mic acid also unites to iron, the chromate of iron being found native ; and it is from this that the chromic acid is procured and united to lead, to form the chromate of lead. Chromate of iron is, therefore, much sought after, and is found in greatest abundance in America, from whence our colour-makers chiefly procure it. 124 URANIUM. —COLUMBIUM.— CERIUM, The pure metal is of a tin colour ; it is very brittle, and is said to be magnetic. It is very in- fusible, and is not altered by the air, though when heated it is converted to an oxide. Besides its acid, it seems to combine with oxy- gen in two other proportions, forming the green and hroTdon oxides. URANIUM. This metal was discovered by Werner, in a mi- neral called peclihlende, a blackish mineral re- sembling pitch. Metallic uranium is brittle, and veiy infusible. It is of a grey colour. It is obtained with extreme difficulty, and little known. Its oxide is greenish-yellow, and is found native, resembling green mica, and also in an earthy state. COLUMBIUM. This metal was discovered by Mr. Hatchet in analyzing an ore from North America. It has since been found in the minerals called tantalite and yttro-tantalite. The metal has been procured by Berzelius. It is of an iron colour, hard and brittle, and passes into an oxide at a red heat. Its oxide is white. Its combinations are little known ; but it is one of the acidifiable metals. CERIUM, This metal was lately discovered by Berzelius, in a mineral which has been called cerite. The characters of the metal are imperfectly known, as SELENIUM. — VEGETABLE SUBSTANCES. 125 it has been scarcely seen. The oxide of cerium (cerite) is found native. There appear to be two oxides, the white and the 7'ed. SELENIUM. Selenium is a metal lately discovered by Berze- lius in the sulphur of Fahhun, in Sweden. Its metallic lustre is considerable, and colour grey. It easily fuses and volatilizes before the blow-pipe, with a smell like horse-raddish. It alloys with the metals. It dissolves in nitric acid, and forms with it a substance which is considered as a new acid, selenic acidy which unites with alkalies, forming se^ leniates» VEGETABLE SUBSTANCES. Animals and vegetables differ essentially from minerals, in the two first possessing life and various organs fit for maintaining it, which is called organic structure. Through these organs, various juices and fluids circulate internally, and thus occasion the growth of the animal or plant. In mineral bo- dies this is pot the case j they increase in size only by successive portions of matter adhering to the outside^ nor is there any internal motion. The principal ingredients of ail vegetables are, oxygen, hydrogen, and carbon : sometimes they contain also a little nitrogen, and other elementary substances ; and although these elements are few, yet, by many varieties in their proportions and modes of combinations, a great quantity of proxi- mate constituents are produced. 126 VEGETABLE SUBSTANCES. Vegetable substances may be decomposed, or separated into their elementary principles by various means ; by heats, by acids, and by fermentation : some of these processes occasion not only decom- position, but also new combinations of the elements that did not exist in the living bodies. The principal substances of which all vegetables consist are. Mucilage, or gum, Woody fibre, Sugar, Colouring matter, Fecula, Tannin, Gluten, Wax, Fixed oil, Camphor, Volatile oil. Bitter principle, Resin, Narcotic principle. Caoutchouc, Vegetable acids. Mucilage^ or gum. — Various parts of vegetables impart to water, particularly if boiled with them, a certain viscous consistency : the substance so dissolved is called mucilage. Some trees suffer their mucilage to transude, either spontaneously or by incisions made in them. AVhen it has become concrete by drying in the air, it is called gum. Gum is soluble in water, but not in oils or al- kohol, the latter of which precipitates it from its solution in water. It is insipid ; it does not un- dergo any change by exposure to the air when dry. The gums of different trees differ considerably in their properties. Gum arable may be considered as a very pure gum. Cherry-tree gum and gum tragacanth do not dissolve in cold water ; but dis- solve in boiling water, and, on cooling, assume the state of a jelly. VEGETABLE SUBSTANCES. 127 Gum consists of carbon, oxygen, and hydrogen. Sugar. — The sugar in common use is extracted from a cane that grows only in warm climates, called the sugar-cane ; but it may also be procured from all sweet vegetables. The American maple-tree affords a great deal of sugar, and this useful sub- stance has been made from the beet-root, car- rots, &c. All sugars consist of carbon, oxygen, and hydro- gen ; but it appears that sugar from the cane contains more carbon than other sugars. That obtained from some vegetables will not crystallize. Sugar is first prepared in the countries where it is grown, by boiling the juice and evaporating ; one part of the juice crystallizes, and forms the raw or muscovado sugar ; the other part, the molasses or treacle, will not crystallize. The raw sugar when brought to this country is re-dissolved and crystal- lized again, which is called refining, by which the loaf-sugar is made. To whiten it completely, clay is put upon the tops of the conical pots in which the sugar has granulated, which allows water to percolate through, and thus drain off the last re- mains of the molasses. This is called claying the sugars. Fecula, or starch. — This substance is contained in many seeds and roots. It is separated by bruising the vegetables containing it in water, and stirring them together. The fecula separates in the water, making it appear turbid. The white fluid is pour- ed off and suffered to settle ; the starch subsides to the bottom. Starch is made mostly from wheat; it is also made form potatoes. Starch is a white substance, insoluble in cold water, but soluble in warm. Its solution is gelatinous, and when solid it resembles gum : this, when dry, is a com- 128 VEGETABLE SUBSTANCES. pound of starch and water. Starch is not soluble in alkohol. In the process of converting grain into malty the starch or fecula is changed into sugar. It may also be converted into sugar by boiling it with diluted sulphuric acid. Starch consists of carbon, oxygen, and hydrogen. Gluten. — This principle is found in various vege- table juices, but most abundantly in wheat flour. It is separated from it by washing, with a stream of water, a paste made of flour and water, at the same time kneading it between the fingers. The water car- ries off the starch gradually, leaving the gluten be- hind. Gluten is insoluble in water, and is elastic like elastic gum. It has no taste, and, when dried, becomes hard and brittle. It considerably resem- bles animal gluten, furnishing ammonia by distil- lation. Fixed oil. — This is obtained by pressure from certain seeds and fruits, as the olive, linseed, rape seed, almond, &c. The fixed oils differ much ; some being nearly solid, are called vegetable butters. When expressed, they are generally mixed with some mucilage, which occasions them to turn rancid. They may be deprived of their colour by charcoal. Fixed oils dissolve sulphur, and then form balsams. They also dissolve phosphorus. Fixed oils are very combustible, and, when strongly heated, yield olifiant and carburetted hy- drogen gases. They form soaps by being combined with alkali. The best soaps are made of olive oil and soda ; but common soaps are made with the animal oils and fat. Transparent soap is made by dissolving soap in alkohol, and then concentrating the solution whicli VEGETABLE SUBSTANCES. 129 is of a gelatinous consistence, by distilling off the alkohol. Fixed oils are mucli used for painting, as they are of a drying nature : they are rendered still more drying by boiling them with the oxides of metals, as litharge. Volatile oil. — This is also called essential oil. Many vegetables afford essential oil by expression, or by distillation, When dissolved in water they constitute perfumed essences and distilled waters. They have much odour and taste. They are in- flammable. They are volatilized by a gentle heat, and evaporate entirely when pure so as to leave no trace. The chief essential oils are, the oils of tur- pentine, spike, cloves, oranges, lemons, lavender, &c. Many of them bear a high price. Resin. — The resins are an important class of vegetable substances from their application in the arts. They are very numerous, and often exude spontaneously from trees. Common resin is obtained from the^r ; a juice exudes from this tree, which is common turpentine: this consists of the oil of turpen- tine and resin. When the essential oil is separated by distillation, the resin remains. Mastich is a resin obtained from a tree that grows in Turkey. San- darach is the resin of a tree in Barbary. Copal is a resin from a tree that grows in America, and is a very valuable substance for varnishes. Lac is a resin made by an insect in the East Indies. It is very useful in varnishes, and in sealing-wax. Am- ber is a substance resembling in its properties the resins, but it is only found in the earth, or washed out and driven on the shores. All the resins are insoluble in water, but soluble in alkohol, especially when assisted by heat. The greater number are soluble in the essential oils, and some are so in the VOL, II. K ISO VEGETABLE S¥BSTANCES. fixed oils. They are also dissolved by alkaline ]ys, and by the acids. Resins consist of oxygen, carbon, and hydrogen ; and they are supposed to be volatile oils saturated with oxygen. Bitumen is a substance having some analogy witli oils and resins, although differing in its consti- tuents, and being also a mineral body. Pure bitu- men is called naphtha, which is transparent, highly inflammable, volatile, of a pungent odour ; it is found in certain wells, and there are springs of it in several parts of the world. When naphtha is exposed to the air, it thickens, and becomes dark coloured; it is then called j9e/ro/ez^w, which is procured in the same manner, and is used for burning in lamps. Maltha or mineral pitch is a still farther thickened bitumen, and when it has become solid it is called asphaltum. Caoutchouc. — This is the substance usually known by the name of Indian ri(hbcr, and- some- times elastic gum. It was first brought from South America. It exudes as a milky juice from a tree, which thickens and hardens by exposure to the air. The natives form it into bottles by coverina: balls of clay with this juice ; the clay is afterwards washed out after the caoutchouc is solid. When caoutchouc is pure, it is white, the black colour being owing to the smoke used in drying it. This substance is extremely elastic. It is perfectly inso- luble in water, but it may be softened by boihng, ; so that its edges may be united together. It is not ( soluble in alkohol : but it is soluble in ether j and when the ether is evaporated, the caoutchouc re- I mains unaltered in its properties : by this means tubes and other instruments might be made of it, \ but the method would be too expensive. It is so- luble in some of the fixed and essential oils, as in spermaceti and in oil of cajeput. if I I VEGETABLE SUBSTANCES. 131 Woody fibre. — When a piece of wood has been boiled in water and in alkohol, until the soluble sub- stances have been extracted from it, what remains insoluble is the woody fibre, or lignin^ which is the basis oi wood, and consists of long fibres, having a considerable degree of transparency, without taste, and unalterable by the air. It is insoluble in water and alkohol. It is very inflammable ; and, when distilled in a close vessel, yields an acid sub- stance formerly thought to be a distinct acid called the pyro-ligneous, but now known to be the acetic acid with an empyreumatic oil. Pure acetic acid or vinegar is now made from wood by distillation. Wood consists of oxygen, carbon, and hydrogen j when burned, the carbon remains, constituting charcoal. Colouring matter. — The colours of vegetables are owing to peculiar matters, which are extremely numerous, and but little known. Many of them are used as dyes and pigments. The extraction of colouring matters from vegetables, and fixing them on cloths, constitute the arts of dyeing and calico- printing (which see). The colouring matters sometimes are inherent in gums, sometimes in resins, sometimes in fecula ; consequently they require different chemical agents for their solution. Tannin. — This principle is so called because it is employed in the art of tanning leather. It is also called the astringent principle. It is found abundantly in the barks of several trees, particu- larly the oak, and also in certahi seeds. The gall- nut and grape-seeds afford very pure tannin ; and a substance called catechu^ from India, consists chiefly of it. Tannin is distinguished by its forming a precipitate with glue, or isinglass. This precipitate is insoluble in water, and is that wliich .132 VEGETABLE SUBSTANCES. is formed when skins are tanned and made into leathe7\ Wax. — This substance appears to be formed by bees, by some animal process. It is also a vege- table substance, for the polish or varnish of leaves is owing to a coating of wax ; and in some vege- tables in Brazil wax exists in considerable quan- tity; Wax is insoluble in water, but sparingly dissolved by boiling alkohol. It is dissolved rea- dily by the fixed oils, and then forms cerates and ointments. Wax contains a large proportion of carbon, with hydrogen and oxygen. Camphor. — This substance is brought chiefly from Japan, and is distilled from a species of laurel. It is white and semitransparent ; it is very inflam- mable, soluble in alkohol, and sparingly so in water. It is very volatile, and capable of converting into an acid, called the camphoric acid, which form ' neutral salts called camphorates. Camphor resem- bles essential oil in many of its properties. Bitter principle. — It is supposed that this is a peculiar principle. It exists in many vegetables, particularly in quassia, gentian, hop, &c. When extracted, it is of a brownish yellow colour, and brittle when dry. Its taste is very bitter. It is soluble in water and alkohol. A variety of it is supposed to exist in unroasted coflfee. Narcotic priiiciple. — This has lately been called morphine, and is found most abundantly in opium, which consists of this together with several of the principles which have been just described. It is a violent poison when taken internally. When pure it is white, without taste or smell. It is soluble in boiling alkahol, but is scarcely acted upon by water. From the rapid progress of chemistry, many other vegetable substances are considered as pe- VEGETABLE SUBSTANCE^. 133 culiar principles ; but it would exceed the bounds of this work to describe them all in detail. The chief amono- them are saber, or a peculiar substance found in cork j asparagin, found in asparagus ; medullinj from the pith of the sunflower ; fungin, the fleshy part of mushrooms, &c. Vegetables also contain several acids ready formed. Vegetable and animal acids differ from the others essentially. They always contain car- bon and hydrogen : some of them contain azote, and generally, though perhaps not always, oxygen. They do not seem capable of combining with dif- ferent proportions of oxygen only, but whenever the quantity of this principle changes, that of the rest changes also. Tartaric acid. — Tartar , or cream of tartar^ is a substance found in an impure state, incrusted^on the bottom and sides of wine casks : when purified by solution and filtration, it is sold for use. This salt, which is soluble in water, consists of tartaric acid and potash ; it is therefore tartrate of potash. Tartaric acid when crystallized is imperfectly trans- parent, white, and does not deliquesce in the aii« It is soluble in water. It combines with alcalies, earths, and metallic oxides, and forms tartrates. Ojcalic acid, so called from being first obtained from oxalis acitosella, or wood-sorrell. It is also called the acid of sugar, because obtained from sugar by the nitric acid. It is proper that every one should know that oxalic acid is a deadly poison, and that many persons have lost their lives by mistaking it for Epsom salts, which it resembles. It IS much employed for cleaning boot-tops and leather, and also by the calico-printers. Malic acid was first found in the juice of apples. It exists also in many other vegetables. This acid K S 154 FERMENTATION. is very sour, and does not crystallize ; it forms salts with many of the metallic oxides. Gallic acid. — Tliis acid is found in gall-nuts. It crystallizes, and forms whitish crystals, of a sour taste and peculiar smell. When gallic acid is put into a solution containing iron, a black precipitate appears. The base of ink is iron thus precipi- tated. To produce good black ink, infuse one pound of powdered gall-nuts for four hours, without boiling, in common water, with six ounces of gum-arabic, and six ounces of sulphate of iron. With gold, gallic acid forms a brown precipitate j with silver, a grey ; with mercury, an orange; with copper, a brown ; and with lead, a wliite. Citric acid is procured from the juice of lemons and other fruits. It is capable of crystallizing. Its crystals are soluble in water, and very sour. It forms citrates with the earths, alkalies, and metals. It is much used in calico-printing. It is also used for discharging spots of ink from linen. Benzoic acid is obtained from gum-benzoin, or benjamin. It is a crystallizable acid. The com- pounds which it forms are called benzoates, Kinic acid is found in Peruvian bark. FERMENTATION. If mucilagi-nous saccharine vegetable substances be subjected to the action of water and heat, (from 60 to 70 tleg. Fahr.) they experience, in a very short time, a very striking change. An internal commotion takes place, the mass grows turbid, a large quantity of air-bubbles, consisting of carbonic acid gas, are disengaged, which, on account of the viscidity of the matter in which they are inclosed, form a stratum on the surface of the fluid, known FERMENTATION. 155 by the name of yeast. After a time these appear- ances cease, the fermented liquor becomes clear and transparent, and no more gas is discharged. The liquor now has lost its sweetness and viscidity, and has acquired the vinous taste and intoxicating quality. Sugar appears to be essential to this pro- cess J and all mucilaginous substances containing sugar are capable of this fermentation, which is called the vinous. Wine is made in this manner from the juice of the grape ; if the fermentation be checked when at its height, by excluding the air, the wine begins to ferment anew, and effervesces when again ex- posed to the air. The sparkling wines, as Cham^ pagne, are prepared in this manner, and hence should be considered as imperfect wines. To prepare vinous liquors from grain or corn, it must first be converted into maU^ by steeping it in water, and then exposing it to the air, turning it frequently over j by this process, the gluten of which the germ consists is separated, and the fecula is converted into sugar by the germination of the seed. Beer is made by boiling the malt in water, which produces a sweet liquor called tvoi^t ; this is con- verted into beer by fermentation and the addition of hops, which furnish a bitter substance. Wine, beer, and all fermented liquors, owe their intoxicating qualities to a peculiar substance which they contain, and which is the produce of fermen- tation alone. . This substance is a fluid called alko- hoi, or spirit of m7ie, and may be separated in a pure state by distillation. When first obtained it is mixed with a quantity of water, but if it be re- distilled, it is obtained very pure, and is then called rectified alkohol. Alkohol is of a strong heating K 4 lS6 FERMENTATION* taste, of a peculiar penetrating odour, and it is very inflammable and volatile. It dissolves resins, essential oils, camphor, sulphur, phosphorus, &c. It is composed of hydrogen, carbon, and a small quantity of oxygen. Strong acids and alkoliol have a considerable action on each other, and this produces ether^ which is a fluid still more highly volatile, inflammable, and odorous. Nitric acid with alkohol produces nitric ether ^ and sulphuric acid in the same way produces sulphuric ether. When wine, or any fermented or vinous liquor is exposed to a heat, from 75'^ to 85S Fahr., and access of air is permitted, the fluid becomes turbid, and a new change of principles takes place. It loses its taste and smell, it becomes sour, and is converted into vinegar, or acetous acid. Though vinegar is chiefly prepared from fluids which have undergone the vinous fermentation, yet this is not necessary to the production of vinegar, for simple mucilage is capable of passing into the state of acetous fermentation. When the saccharine prin- ciple predominates in any substance exposed to the necessary conditions of fermentation, alkohol is produced ; when mucilage is most abundant, vinegar or acetous acid is the product j and when gluten is predominant, ammonia will be discovered, and putrefaction will take place. Common vinegar may be purified, or concen trated by distillation, and it is then called distilled vinegar. This, however, still consists of the acetic acid and water. To free the acid from the water, distilled vinegar is saturated with some metallic oxide, and an acetate is thus formed. The acetate is then heated red hot in a retort, by which it is decomposed, and the acetic acid passes over pure. ANIMAL SUBSTANCES. 137 Acetate of copper or verdigris^ and likewise ace- tate of leady are used for this purpose. Acetic acid is very pungent and caustic. It is very vola- tile, and combines with the metals, earths, and alkalies. This acid may also be obtained from wood, by subjecting it to distillation in a retort. In this state it is very impure, being combined with a quantity of empyreumatic oil. This was formerly called pi/- roligneous acid. When separated from impurities it is essentially the same with vinegar, and is now employed for the same purpose. The last change, or final decomposition that vegetables undergo, is called the putrefactive fer- mentation^ OY putrefaction. Without moisture, heat, and a due access of air, this does not take place. By this vegetables are resolved into their consti- tuent principles, and ammonia is formed. ANIMAL SUBSTANCES. The elementary principles of animal substances are nearly the same with those of vegetables, but the former contain more nitrogen and phosphorus, and the latter more carbon and hydrogen. The proximate constituent parts of animal sub- stances are the following : Gelatine^ or animal jelly, is very generally dis- persed through all the parts of animals, even in bones, but exists in the greatest quantity in the tendons, membranes, and the skin. It is a viscid substance, very soluble in warm water, but not in alkohol ; insipid, and without smell ; when cold, it congeals into a cohesive, tremulous substance. It forms the basis of soups, broths, &c. and imparts to 138 ANIMAL SUBSTANCES, them tlieir nutritious qualities. \VTien evaporated to dryness, it forms poi^table soup, size, ghie, &c. The union of this latter substance in the skin with tannin constitutes leather. Isinglass is gelatine procured from certain parts of several fish, particu- larly the sturgeon. The tendons and membranes of the body are chiefly gelatine. Fibrin, or animal Jibre, forms the basis of the niusctdar, or fleshy parts of animals. It is there combined with albumen, and remains with it after all the soluble parts of the flesh have been separated by water. It may also be obtained from blood, by washing the clot or coagulum in water, till a white fibrous matter remains. Fibrin is not soluble in cold watei% but is very slightly so in boiling water. It is soluble in acids and alkalies, and by its union with the latter a soap is formed. Chaptal em- ployed this joroperty to make a soap from wool. It is very analogous to vegetable gluten. Albinnen is the principal constituent of the serum of blood, and is also called coagidable lymijh. The white of eggs consists almost entirely of albumen. It is miscible with cold water, but is coagulated by heat, which forms the best test of its presence. It is also coagulated by acids and alkohol. Mucus. — This substance in animals appears in- tended to lubricate or smooth certain parts of the body, and seems very analogous to a solution of gum. However, Dr. Bostock has shown that it diflfers from gelatine, as it cannot in cold water be brought to assume the gelatinous state. Tannin precipitates gelatine, but not mucus, whereas sub- acetate of lead, (extract of Goulard,) forms a preci- pitate with mucus, but not with gelatine. Mucus is found in saliva, tears, in the intestines, joints, &c. ANIMAL SUBSTANCES. IS^ Oil.'— Animal oils are fat, tallow, butter, &c. They are mostly solid at the usual temperature. They may be rendered fluid by heat. Oil is ob- tained in great quantities from certain fish, parti- cularly the whale, seal, &c. and fish oil continues fluid. It is very similar to vegetable oil in its other properties. Spermaceti somewhat resembles wax, and is obtained from the head of a species of whale. Animal fibre may be converted into a substance like spermaceti by treatment with the nitric acid, or by exposing it to a current of running water for several months. This has been called adipoeire. It has been shown lately that fat is a compound body, consisting of a substance solid and much like wax, which has been called stearin^ and a fluid oil called elain. Milk is a substance secreted by certain animals for the nourishment of their young. As is well known, milk on standing for a day throws up cream to the surface. Cream has mucli of the properties of an oil, and when agitated by churning, butter is separated from it. If milk stands until it becomes sour, it separates into a coagulum and a whey. This change may be more completely effected by adding to the milk a small quantity of certain sub- stances, as acids, or rennet^ procured by boiling in water the inner coat of the stomachy of a calf. The coagulum is thus made more solid, and when pressed and dried it forms cheese. In animal bodies there are also found several pe-' culiar acids. The lactic acid is found in sour whey. It com- bines with the earths and alkalies, forming salts called lactates. It resembles much the acetic acid. The uric acid is found in urine. The substance voided with the urine called gravel, and also those 140 ANIMAL SUBSTANCES. stones formed in the bladder called calculi, are almost entirely composed of nric acid. This acid, however, exists in urine even in its most healthy state. The amniotic acid is found in the liquor of the amnios of a cow. It separates in white crystals. The saccho-lactic acid is formed by acting on su- gar of milk, or on gum by the nitric acid. It forms salts called saccho-lactates. The sehacic acid is procured from animal fat. It becomes solid, is of a white colour, with a taste slightly acid. The Prussic acid has been described, p. under the name of the hydrocyanic acid. The formic acid is an acid procured from ants. Animal resins. — Peculiar tesins have been found in certain animal substances, as in the bile, amber- gris, &c. Animal sugar is found in milk, also in the urine in certain diseases. It is similar to common sugar. " Blood, when suffered to rest, separates into two parts J the one a coagulum or clot, called the crassamentum ; the other, a fluid called the serum. The crassamentum consists of fibrin mixed with al- bumen and colouring matter. The colouring part of blood consists of extremely minute globules of a red colour, which float in the serum, and may be seen by the microscope. The red colour of blood has been supposed to be owing to iron which was oxy- dated by the air in the lungs, but this theory is now rendered questionable. The serum is com- posed of albumen, and also contains a small por- tion of alkali and other substances. It is coagu- lated by heat, the acids, and alkohol. Bone is composed of gelatine, another substance which seems t5 be analogous to cartilage or coa- ANIMAL SUBSTANCES. 141 gulated albumen, an oil, or marrow, and phosphate and carbonate of lime, besides other matters in minute portions. Teeth are composed of similar ingredients. Shells contain a greater proportion of carbonate of hme. Horns, nails, hoofs, and quills are chiefly gelatine and albumen. Besides the animal substances above enumerated, there are various matters secreted or formed by cer- tain organs in the body, as saliva, the gastric juice, the bile, thejluid ofi^erspiration, kc, the nature of which is not yet thoroughly known. The examination of animal substances, called animal chemistry, is one of the most difficult, as well as one of the most important, branches of the science ; and a wide field is yet open for research. When animal bodies are deprived of the vital principle, and are exposed to the air, they undergo a speedy decomposition called putrefaction. By this they are resolved partly into their elementary principles, and some of these form new compounds. The first change is observed by the bodies altering in their colour, losing their elasticity, and by their giving out a very fetid and noxious sm.ell. The greater part, in time, assumes a gaseous form, and nothing remahis but a small quantity of earths and salts. One of the greatest improvements in chemistry has been that made in its nomenclature, which we owe chiefly to the French chemists. As the former names of many substances differ so entirely from those at present employed, that, without some assistance, many of the old writers on chemistry are not now" intelligible to those acquainted only with the modern nomenclature, a list is subjoined 142 NOMENCLATURE OFJ CHEMISTRY. of the terms which most generally occur in old books on this subject, together with those which are now adopted instead of them. } Old Names arranged Alphabetically. Acetous salts Acid of vitriol, phlogisticated — of alum — of vitriol — of vitriolic — of sulphur — of nitre, phlogisticated — of nitre, dephlo- gisticated — of saltpetre — of sea salt! — marine - j" — aerial - "] — of chalk I — cretaceous [>• - — of charcoal | — raephitic J — of spar or fluor ") — sparry - | — of borax — of arsenic — of tungsten | — of wolfram J' — of molybdena — of apples — of sugar n — saccharic J — of lemons — of tartar — of benzoin — of galls — of amber — of ants — of phosphorus phio- ") gisticated - j — of phosphorus de- ") phlogisticated J New Names. Acetates Sulphureous acid Sulphuric acid Nitrous acid Nitric acid Muriatic acid Carbonic acid Fluoric acid Boracic acid Arsenic acid Tungstic acid Molybdic acid Malic acid Oxalic acid Citric acid Tartareous acid Benzoic acid Gallic acid Succinic acid Formic acid Phosphorus acid Phosphoric acid NOMENCLATURE OF CHEMISTRY. 14.3 n Old Names arranged Alphabetically, Acid of fat \ — sedative / — of lac - — ofmilk — of the sugar of milk Air - — dephlogisticated' — empyreal — vital — pure — impure, or vitiated") — burnt - - > — phlogisticated J — inflammable — marine acid — dephlogisticated) — marine acid j — hepatic - - 7 — fetid of sulphur 3 Air fixed - > — sohd of Hales j — alkaline Alkalies, fixed ■ volatile — concrete volatile caustic effervescent, ae- \ rated, or mild J vegetable mineral or marine Prussian - Alum Antimony, crude Aqua fortis - regia - ammonia pura Argil, or argillaceous earth Bezoar mineral Black lead - Borax Butters of the metals Calces, metallic Ceruse Nexv Names. - Sebacic acid - Laccic acid - Lactic acid - Saccho-lactic acid - Gas - Oxygen gas - Nitrogen, azote, or azotic gas - Hydrogen gas - Muriatic acid gas - Oxygenated muriatic acid gas, or chlorine - Sulphureted hydrogen - Carbonic acid gas - Ammoniacal gas - Potash and soda - Ammonia - Carbonate of ammonia - Pure alkalies - Alkaline carbonates - Potass - Soda - Prussiate of potash - Sulphate of alumine and potash Svdphuret of antimony - Nitric acid of commerce - Nitro-muriatic acid Ammonia - Alumine, or alumina - Oxide of antimony - Plumbago - Borate of soda - Muriates of the metals - Metallic oxides » Carbonate of lead 144< NOMENCLATURE OF CHEMISTRY. Old Names arranged Alphabetically. Ceruse of antimony - Charcoal, pure Colcothar of vitriol - Copper, acetated Copperas, green • blue Cream of tartar Earth, calcareous aluminous siliceous ' ponderous magnesian, or muriatic Emetic tartar Essences . - - Ethiops, martial • mineral Flowers, metallic of sulphur - Fluors . - - Hepars . - - Heat, latent Kermes mineral Lapis infernalis Leys Liquor sllicum 1 of flints J Litharge Liver of sulphur, alkaline calcareous Luna cornea Magistery of bismuth Magnesia alba ") • aerated j ■ black Masticot Mephitis Minium Mother waters Nitre, or saltpetre - Neix Names. White oxide of antimony Carbon S Red oxide of iron by the sul- ( phuric acid Acetate of copper Sulphate of iron of copper Acidulous tartrate of potash Lime Alumina, or alumina . Silex Barytes Magnesia Antimoniated tartrate of potash Volatile oils Black oxide of iron J Black sulphureted oxide of \ mercury Sublimated metallic oxides Sublimated sulphur Fluates Sulphurets Caloric f Red sulphureted oxide of an- \ timony Fused nitrate of silver Solutions of alkalies Solution of siliceous potash J Semivitreous oxide of lead or \ litharge Sulphuret of potash of lime Muriate of silver (Oxide of bismuth by the nitric I acid Carbonate of magnesia ' Black oxide of manganese Yellow oxide of lead - ■ Nitrogen gas • Red oxide of lead • Saline residues ■ Nitrate of potass NOMENCLATURE OF CHEMISTRY. 145 Old Names arranged Alphabetically. Nitres Oils, fat - • etherial of tartar per deliquium Phlogiston - Phosphoric salts Precipitate, red ■ per se Principle, astringent ■ tanning - — — acidifying inflammable Pyrites of copper Pyrites martial Realgar Reguliis of the metals Rust of iron Saffron of Mars Sal ammoniac — polychrest Salt, common or sea — febrifuge of Sylvius — fusible of urine — Glauber's — Epsom - — of sorrel — of wormwood - — vegetable Saltpetre Selinite Spar, calcareous fluor - ponderous Spirit, ardent "i of wine 3 — — of nitre of salt Nex'o Names. ' Nitrates . Fixed oil ■ Essential oils A solution of potash f A principle imagined by Stalil, \ but now not admitted . Phosphates f Red oxide of mercury by the \ nitric acid - Red oxide of mercury by fire - Gallic acid - Tannin - Oxygen - See Phlogiston - Copper pyrites rlron pyrites, or sulphuret of "1 iron ("Red sulphuretted oxide of \ arsenic - The metals in a pure state - Oxide of iron - Oxide of iron - Muriate of ammonia - Sulphate of potash - Muriate of soda - Muriate of potash - Phosphate of soda - Sulphate of soda of magnesia - Acidulous oxalate of potash - Carbonate of potash - Tartrite of potash - Nitrate of potash - Sulphate of lime - Crystallized carbonate of lime - Fluate of lime - Sulphate of barytea - Alkohol - Nitric acid - Nitrous acid - Muriatic acid VOL. II. 146 NOMENCLATURE OF CHEMISTRY. Old Names arranged Alphabetically. Spirit of sal ammoniac of vitriol Spiritus rector Sublimate, corrosive Sugar of lead Tartar emetic vitriolated Tartars Tinctures, spirituous Turbeth mineral Vinegar, distilled") radical j Vitriols Vitriol, blue green — — white Water acidulated "^ hepatic Netu Names. • Ammonia Sulphuric acid • Aroma - Muriate of mercury ■ Acetate of lead ■ Acidulous tartrite of potash Antimoniated tartrite of potash ■ Sulphate of potash ■ Tartrites Resins dissolved in alkohol J Yellow oxide of mercury by the \ sulphuric acid Acetic acid ■ Sulphates . Sulphate of copper of iron of zinc c Water impregnated with car- \ bonic acid gas {Water impregnated with sul- phuretted hydrogen 147 MANUFACTURES AND ARTS. The modern sciences, and particul-ajy cbemjstjy, have been of late successfully applied to the im- provement of several of the useful arts j and some, in consequence, have undergone almost an entire change. Of the principles of some of them we propose to give a brief description. MAKING BREAD. Scarcely any nation exists, in which the use of bread is entirely unknown, or something as a sub- stitute for it ; a dry food appearing to be neces- sary to promote the secretion of saliva, in the pro- cess of mastication. In Lapland, where they have no corn, they make a kind of bread from dried fish, and of the inner rind of the bark of the pine. In some parts of xlmerica, they use, for this purpose, casava, the root of a plant which is poisonous till it is rendered whole- some by the extraction of its acrid juice. In the South Sea islands, the bread-fruit tree affords the natives a substance resembling bread. From time immemorial, the farinaceous seeds have been employed as food, and they are the most nutritive of all the vegetables. Few of the alimen- tary substances are used by man in a raw ana crude state; almost all undergo some preparation, by which they are rendered more easy of diges- tion, or are more palatable. The application of L ^ 148 MAKING BREAD. heat generally effects considerable changes in tlie different principles of which they are composed. Thus, bread from wheat is no longer capable of forming a paste with water, such as can be made with flour ; nor can starch, and gluten, elements existing in flour, be obtained from it after it has been baked in bread. The alteration in potatoes by the culinary process is even more considerable. The farinaceous vegetables used for making bread, are chiefly wheat, barley, oats, rye, buck wheat, maize, beans, pease, rice, potatoes, &c. In times of scarcity, other substances have been used, as acorns, chesnuts, &c. Of all these wheat is found to afford the best bread, and we shall begin by describing it. Wheat flour, when analysed, is found to consist of — 1. Gluten. 2. Fecula, or starch, 3. Saccharine matter, or mucilage. The gluten is very elastic, of a greyish white colour, and when drawn out to its fullest extent, has the appearance of animal membrane. In this state, it adheres to many bodies, and forms a very tenacious glue, which has been used for mending broken porcelain. It is insoluble in water, alkohol, ether, or oil ; and, in many of its properties, it re- sembles animal substances. The Jecula is a delicate white powder, soft to the touch, scarcely sensible to the taste, almost inso- luble in cold water, but soluble in warm water. The saccharine part is a sugar similar to what is contained in other vegetables. These three constituent principles are easily separated from each other in the following manner. Knead some flour with water, and let a stream of water constantly flow over it. The fecula, or starch, will be carried off' by the water, and will MAKING BREAD. 149 fall to the bottom of the vessel where it is collected; the siiffar will be held in solution in the water em- ployed, and the gluten will remain alone. There are three sorts of bread in general use, prepared from wheat flour : 1. Unleavened bread. 2. Leavened bread. S. Bread made with yeast. Unleavened Bread. When flour is kneaded with water, it forms a tough adhesive paste, containing the constituent principles of flour, with little or no alteration, and not easily digested by the stomach. When formed into cakes, and baked by heat, the gluten, and probably the starch, undergo a con- siderable change, and the compound is rendered more easy of digestion. Bread made in this manner, without any addition, is called unleavened bread. It is not porous, but solid and heavy. This is, no doubt, the most ancient method of preparing bread, and it is still used in many coun- tries. The oat cakes, and barley bread, used in Scotland, and the north of England, are of this kind ; so are also biscuits of all kinds. Unleavened bread is also used by the Jews during the Passover. OfLeave7ied Bread. When flour is kneaded with water, it is called dough ; and when this is kept in a warm place, it swells up, becomes spongy, and is filled with air- bubbles ; it disengages at length an acidulous and spiritous smell, tastes sour, and in this st3>t,e is called leaven, .7.: . Here the saccharine part has been converted into ardent spirit, the mucilage tends to acidity, L 3 ||J0 MAKING BREAD. and the gluten probably verges towards a state of putridity. By this incessant fermentation, the mass is rendered more digestible and light, that is, it becomes much more porous by the disengage- ment of elastic fluid, which separates its parts from each other, and much enlarges its bulk. The operation of baking puts a stop to this process, by evaporating a great part of the moisture, which favours the chemical attractions, and probably also by further changing the nature of the component parts. Bread, however, in this state, will not pos- sess the requisite uniformity. In order to promote an uniform fermentation, a small portion of leaven is intimately blended with a quantity of other dough, which, by the aid of heat, diffuses itself, and causes all the parts to ferment at the same time. As soon as the dough has acquired a suffi- cient bulk from the extrication of carbonic acid gas, it is considered as fit for the oven. It will be necessary here to consider more at large the nature of the fermentation^ which is so essential in the making of good bread. When wheat-flour and water are mixed, the saccharine extract of the flour, in consequence of heat and moisture, has its constituent principles disunited ; the oxygen seizes the carbon, forming carbonic acid, which flies off in the form of gas, and occasions that internal motion and increase which appears. This process, if left to itself, is extremely slow, and is therefore accelerated by the addition of more dough and warm water. The gluten, being dispersed through every part of the mass, forms a membrane among the dougli, which suffers the carbonic acid gas to expand, but pre- vents its total escape, thus causing that porous reticulated appearance, which fermented bread MAKING BREAD. 15| always has. As soon as the dough begins to sink it is made up into the proper form, and put into the oven, where tlie heat converting the water into an elastic vapour, the loaf rises still more. The fer- mentation by means of leaven is thought to be of the acetous kind, because it is generally so managed that the bread has a sour taste. Bread made mth Yeast. Yeast is the froth formed upon the surface of beer, or ale, in a state of fermentation, and is com- posed of carbonic acid gas inclosed in bubbles of the mucilaginous liquor. When this is mixed with dough, it causes it to ferment, and rise better and more quickly than ordinary leaven ; and by this means the best bread, and that now most generally in use, is made. Bread made with yeast is not only less compact, lighter, and of a much more agreeable taste than the preceding kinds ; but it is also more miscible in water, with which it does not form a viscous mass, a circumstance of the greatest importance in digestion. Bread, if well baked, is materially different from flour and farinaceous cakes ; it no longer forms a tenacious dough with water, nor can starch or gluten be any more separated from it, : and hence most probably its good qualities result. The method of making common family bread is as follows : to half a bushel of flour add six ounces of salt, a pint of yeast, and six quarts of water that has boiled ; in warm weather pour the water in nearly cold, but it winter let it be lukewarm. Put all these into a kneading-trough, and work them together till they are the proper consistence of dough. Cover up the dough warm that it may L 4 152 MAKING BREAD. ferment and rise. This is called setting the sponge. After letting it lie the proper time, an hour and a half, more or less, knead it well together, and let it lie some time longer covered up. The oven must in the mean time be heated : when this is done, and it is properly cleaned, make the bread into loaves, and place them in the oven to bake. Household hread^ or brown bread, is baked in the same manner, only of flour that is made from the whole of the wheat, the bran as well as the flour being ground together ; whereas in the white bread, the coarser part of tlie bran is separated from the flour. In what is called French bread, the fermentation is carried on longer than in com- mon bread, by which it becomes more porous, and consequently lighter. Some bakers make a supe- rior kind of French bread, by putting together a peck and a half of the finest wheaten flour, called Hertfordshire white, a pint of milk, a quarter of a pound of salt, a pint and half of yeast, a quarter of a pound of butter, two eggs, and three quarts of water ; it is baked nearly in the same manner, only frequently turning the bread in the oven. The process used by the bakers for making bread varies from what has been described, only in circumstances depending on the great quan- tity that is baked at a time. It is said that they are apt to adulterate the bread sometimes with alum, and also with chalk, and for this they are severely punishable ; and any one suspecting it may easily detect it by cutting a loaf in slices, and mixing it with water which will dissolve the alum : and it may then be obtained by evaporation. Bread is made from the farinaceous grains ; but of these, barley, oats, and rye, are most generally used in Great Britain next to wheat. Wheat alone MAKING BREAD, 153 possesses the gluten above described, which is so useful in making the bread porous and light ; on which account it is more difficult to make fer- mented bread from the other grains : but this dif- ficulty is obviated by adding to them a small quan- tity of wheat flour, and many of them afford bread nearly as nutritious, if not entirely so, as wheat. It appears to be the fecula, or starch, that is the the most nutritive part of the grain ; the potatoe, which contains a great proportion of this substance, forms the food of the most of peasantry in Ireland. Ri/e h^ead is of a brownish colour, and has rather a sweetish taste. It is much used in the north of Europe, and also in some parts of this kingdom ; but it is more usually mixed with a quantity of wheaten flour. Rye is also sometimes mixed with a fourth part of ground rice, and makes a good and economical household bread. Bread has also been made by mixing turrdps and flour in equal quantities. This requires rather longer baking, and has at flrst a sweet taste, which it loses on being kept twenty-four hours. RicCy though usually prepared for food by boil- ing, has been made into bread by mixing with it a little flour, or potatoes. Potatoes have also been made into bread by mixing with them a quantity of wheaten flour, BREWING. The art of brewing, or of preparing a fermented liquor called heer^ from farinaceous seeds, is very ancient. It was known to the ancient Egyptians, Spaniards, Germans, Gauls, inhabitants of the British Isles, and of the north of Europe. The l^l* BREWING. liquor made by them, however, resembled more our sweet and mucilaginous ales, the use of hops being of modern invention. Beer is made of an extract produced from malt and hops by boiling ; and this extract is after- wards fermented by adding yeast to it. Malt is made from barley by a process which is called malting. Barley is a grain consisting of fecula, or starch, albumen, and a little gluten. By the process of malting, its fecula is converted into sugar, a substance essential to the production of ardent spirit or alkohol, w^hich is the substance that gives the intoxicating quality to every liquor. To prepare malt, the grain is put into a trough with water, to steep for about three days j it is then laid in heaps, to let the water drain from it, and afterwards turned over and laid in new heaps. In this state, the same process takes place as if the barley were sown in the ground; it begins to germinate, puts forth a shoot, and the fecula of the seed is converted into saccharine matter. When this is sufficiently accomplished, which is known by the length of the shoot, (about \ of the length of the grain) this process of germination must be stopped, otherwise the sugar would be lost, nature intending it for the nourishment of the young plant. The malt is, therefore, spread out upon a floor, and frequently turned over, which cools it, and dries up its moisture, without which the germination cannot proceed. When it is completely dried in this manner, it is called air- dried malt, and is very little altered in colour. But when it is dried in kilns, it acquires a brownish colour, which is deeper in proportion to the heat applied ; it is then called lUn-dried, This malt is then coarsely gi'ound in a mill. BREWING. 155 The quality of the beer depends upon the way in which the malt has been prepared as well as the quantity. There are three kinds of malt generally used, pale, brown, and amber. Pale malt is dried by a slow fire, and only so much as just to check the future germination of the grain : it is dried sometimes upon hair or wire sieves, which are made to form the bottom of the kiln. Brown malt is dried with a quick fire, and the outside is in fact a little charred. Amber malt is intermediate be- tween these two. Pale malt is used for fine ales and pale beer : brown malt is used for porter ; and amber is em- ployed for brown ale and beer, and also to mix with brown malt for porter, a practice which many prefer. MasJiing is the next step in the process of brew- ing. This is performed in a large circular wooden vessel called the mash-tun, shallow in proportion to its extent, and furnished with a false bottom, pierced with small holes, and fixed a few inches above the real bottom. There are two side open- ings in the interval between the real and false bottom : to one is fixed a pipe, for the purpose of conveying water into the tun, and the other is for drawing the liquor out of it. The malt is to be strewed evenly over the false bottom of the same tun, and then, by means of the side pipe, a proper quantity of hot water is introduced from the upper copper. The water rises upwards through the malt, or, as it is called, the grist, and when the whole quantity is introduced, the mashing begins, the object of which is to efiect a perfect mixture of the malt with the water, so that the soluble parts may be extracted by it : for this purpose, the grist is sometimes incorporated with the water by iron rakes, and then the mass is beaten and agitated by 166 BREWING. long flat wooden poles, resembling oars, which are either worked by the hand or by machinery. When the mashing is completed, the tun is co- vered in, to prevent the escape of the heat, and the whole is suffered to remain still, in order that the insoluble parts may separate from the liquor : the side pipe is then opened, and the clear wort al- lowed to run off, slowly at first, but more rapidly as it becomes fine, into the lower or boiling copper. The chief thing to be attended to in mashing is the temperature of the mash, which depends on the heat of the water, and the state of the malt. If the water was let in upon the grist boiling hot, the starch which it contains would be dissolved, and converted into a gelatinous substance, in which all the other parts of the malt, and most of the water, would be entangled beyond the possi- bility of being recovered by any after-process. The most eligible temperature appears to be from 185° to 190^ Fahr. j for the first mashing, the heat of the water must be somewhat below this temperature, and lower in proportion to the dark colour of the malt made use of. For pale malt the water may be 180°, but for brown it ought not to be more than 170°. The liquor, or wort, as it is called, of the first mashing, is always by much the richest in saccha- rine matter ; but to exhaust the malt, a second and third mashing is required, in which the water may be safely raised to 190°, or upwards. The proportion of wort to be obtained from each bushel of malt depends entirely on the pro- posed strength of the liquor. It is said that twenty- five or thirty gallons of good table beer may be taken from each bushel of malt. For ale and porter of the superior kinds, only the produce of the BREWING. 157 first mashing, or six or eight gallons, is to be em- ployed. Brewers make use of an instrument called a sacchrometer, to ascertain the strength and good- ness of the wort. This instrument is a kind of hydrometer, and shows the specific gravity of the wort, rather than the exact quantity of saccharine matter which it contains. The next process in brewing is boiling and hopping. The hop plant is well known : hops con- tain an aromatic and essential oil, having an agree- able bitter flavour. Hops are necessary to prevent the beer from passing into the acetic fermentation, which would take place after the vinous ferment- ation had ceased. They check the fermentation in a great degree, so as to occasion it to go on slowly, and thus to acquire strength ; and the quan- tity of hops depends upon the length of time the beer is intended to be kept. Hops are best when new, as they lose much of their flavour by keeping. If only one kind of liquor is made, the produce of the three mashings is to be mixed together ; but, if ale and table beer are required, the wort of the first, or first and second mashings, is appropri- ated to the ale, and the remainder is set aside for the beer. All the wort destined for the same liquor, after it has run from the tun, is transferred to the large lower copper, and mixed with a certain proportion of hops. The better the wort, the more hops are required. In private families a pound of hops is generally used to every bushel of malt ; but in public breweries, a much smaller proportion is deemed sufficient. When ale and table beer are brewed from the same malt, the usual practice is to put the whole quantity of hops in the ale wort, which. 158 BREWING. liaving been boiled some time, are to be transferred to the beer- wort, and with it to be again boiled. When the hops are mixed with the wort in the copper, the liquor is made to boil, and the best practice is to keep it boiling as fast as possible, till upon taking a little of the liquor out, it is found to be full of small flakes like that of curdled soap. The boiling copper is, in common breweries, unco- vered : but in many, on a large scale, it is fitted with a steam-tight cover, from the centre of which passes a pipe, that terminates by several branches in the upper, or mashing copper. The steam, therefore, produced by the boiling, instead of being wasted, is let into the cold water, and thus raises it very nearly to the temperature required for mashing, besides impregnating it very sensibly with the essential oil of the hops, in which the flavour resides. Vv^hen the liquor is boiled, it is discharged into a number of coolers, or shallow tubs, in which it re- mains until it becomes sufficiently cool to be sub- mitted to fermentation. It is necessary that the process of cooling should be carried on as expedi- tiously as possible, particularly in hot weather ; and for this reason, the coolers in the brewhouses are very shallow. Liquor made from pale malt, and which is intended for immediate drinking, need not be cooled lower than 7-5 or 80 degrees ; of course this kind of beer may be brewed in the hottest weather ; but beer brewed from brown malt, and intended to be kept, must be cooled to 65° or 70*^ before it is put into a state of ferment- ation. Hence in the spring, the month of March, and in autumn, the month of October, have been deemed the most favourable for the manufacture of the best malt liquor. BREWING. 159 From the coolers the wort is put into the "work- ing tun, in which it is mixed with yeast, in the proportion of a gallon to four barrels of wort, in order to excite the vinous fermentation. This process is called tunning. By this the beer obtains its strength and spirit ; the sugar extracted from the malt being con\^erted into alkohol. In four or five hours the fermentation begins. Its first appearance is by a white line on the surface of the liquor, next to the side of the vessel, which gradually advances to the middle, till the w^hole surface is covered with a scum, or froth, formed by innumerable minute bubbles of carbonic acid gas, which rise through the liquor. The temperature of the liquor increases, and the whole is much agitated. The froth on the surface accumulates, and constitutes the yeast. At this time the presence of carbonic acid gas may be easily perceived, by holding one's head over the barrel or tun ; and fatal accidents have happened through the accumulation of this gas in situations where persons have been exposed to it without being able to remove. The vinous fermentation must be checked in time, otherwise the acetous fermentation would begin ; all the spirit would be lost, and the beer would become sour. The fermentation requires from 18 or 20 to 48 hours J and the beer is then put into smaller barrels, called cleansing tuns. In them, the fermentation goes on again, and during a fev/ days, a copious discharge of yeast takes place from the bung-hole. Care must be taken that the barrels are filled every day with fresh liquor. This discharge gradually becomes less, and in about a week it ceases j when the bung-hole is closed. The liquor is now suffered to stand for some 160 BLEACHING. time tojine (or become transparent), by depositing the mucilage that was suspended in it. When there is time, the beer is allowed to fine itself; if not, a preparation of isinglass and sour beer, called Jinings, is put into it, to precipitate the mucilage. A larger quantity of hops are used in porter than for ales. Although in porter the brown malts are necessary, it is bad economy to use them too highly dried for the deepening of the colour, since the consequence of drying too highly is a carbonization of part of the saccharine matter. A dark colour may be procured more economically by adding burnt sugar to the wort. It is in Britain prohibited by law to use any sub- stance in brewing, as a substitute for hops. BLEACHING. Bleaching is the art of whitening cloths, made from vegetable or animal substances, by depriving them of their colouring matter. The art is of great antiquity; and mankind, in all ages, appear to have admired garments of a pure whiteness. The effects produced by the air and rain upon vegetable fibres exposed to them, must have led originally to the idea of producing this by artificial means. The ancients appear to have been acquainted with the uses of soap and leys ; and to have practised bleach- ing, nearly in the same manner as it existed among us until lately. But few manufactures have received so much benefit from modern chemistry, as that now under consideration ; so that since the year 1786, it has undergone a complete change. Bleaching ofLineth The processes of bleaching difl'er materially, according to the different materials of which cloths BLEACHING. l6l are composed: thus, linen, cotton, woollens, and silk, are whitened by different methods. lu order to understand the rationale of the bleaching pro- cesses, it is necessary to be acquainted with the nature of the materials. Flax, from which linen is formed, is a vegetable consisting of several coats or layers. The external coat is a very thin bark ; under this is a green juice or sap; next lies a layer of fibres or filaments, which constitutes the part used for making linen ; and, lastly, in the centre, there is a woody part. To prepare flax for making cloth, the filaments or fibrous part must be separated from the rest. The filaments are held together by the sap, or succulent part. To detach them from this, the flax is steeped for several days in pools or ponds of soft stagnant water; by which the putrefactive fermentation takes place. But this fermentation must not be suffered to proceed too far; otherwise the fibres themselves would be aflR^cted by it, and their texture injured. The flax must be taken out while it is yet green, and while the wood breaks easily between the fingers. The putrefaction of the sap occasions the water in which the flax is steeped to be extremely offensive ; and it is even found that the fish are destroyed in any stream where this process is used. In some places, instead of steeping the flax in water, it is simply exposed to the dew by laying it on the grass. The time required for this part of the process is variable ; depending upon the state of ripeness of the flax, the quahty and temperature of the water, and other circumstances. After steeping the flax, where the watering sys- tem is practised, it is spread very thin on the grass, VOL. II. M l6^ BLEACHING. and occasionally turned, until it is found to be very brittlej so that on being rubbed between the hands, the woody part easily separates. It is then dried by the heat of the sun or of a kiln. The flax is now ready to be beat or broke by a mill for the purpose, or by mallets on a sort of wooden anvil. The fibres of the flax are thus separated from the wood, which is reduced to frag- ments, most of which are cleared away by scutc7ii?ig. To divide completely the fibres from each other, and to separate the remaining part of the wood, the process of hackling is employed. This consists in drawing the flax through piles or groups of sharp and polished iron spikes, placed close together, and fixed in wood. The Ifackles are of various degrees of fineness ; that is, the spikes are placed at different degrees of distance from each other. The coarsest, or most open hackles, are used first ; then a finer, and so on, till the process is completed. The flax is now ready to be spun into thread or yarn, which is manufactured into cloth by the weaver. The linen, as it comes from the loom, is of a brownish grey colour ; and it is then that the pro- cess of bleachiuff- be^'ins. The linen is first steeped in cold water for 48 hours, to discharge from it the weaver's dressing ; which is a paste of flour and water, that had been brushed into the yarn to enable them to stretch it more easily. The grey substance that colours the linen before it is bleached is of a resinous nature, and conse- quently it is insoluble in water. It is also intimately united with the fibres of the flax, and is of difficult separation. What appears to the eye to be a single fibre is, in fact, a bundle of minute filaments, agglu- ^I,E ACHING. 163 dilated t.ogethei' by this resiijoijs matter. To sepa- rate these filaments from eacli otlier, and to destroy entirely the resinous colouring matter, is ^a process of some difficulty. Solutions of alcalies rendered caustic *5 called alcaline leySy have the property of dissolving resins ; hence they have been used for this purpose in bleaching. The linen is boiied in water containing a quantity of ca'.:::;tic potash, which acts upon the resiil of the external filaments, and loosens them a little irom each Qther. The cloth is then spread upon the grass, and exposed to the action of the air, sun, and dew; and is also occasionally watered. It is then returned again into the bucking vat ; and the alkaline solution is poured over it : by this another layer of the fila- ments is opened, and the resin dissolved. It ds then carried again to the field, and ti'eated as before. In this manner, the ibucking and spreading on the grass are repeated alternately, for 15 oi' 16 times, according to the weather and other circum- stances, until the clotli is whitened. Were the alcaline ley go strong as to dissolve xill the resin at once, it would injure the texture of the fabric. This alternate bucking and. exposing on the grass is the old manner of bleaching, and was universally used, till Scheele discovered the properties of the oxygenated muriatic acid in destroying vegetable colours. M. Bertholiet first applied this property to the purposes of bleaching, and he, with great liberality, communicated his observations to the public. For this purpose, he immersed the cloth into diluted oxygenated muriatic acid, between the operations of the alcaline leys, which produced .the * Common potash is rendered sufficiently.c^usdcfor the pur- pose of bleaching, by adding to it quickhme, which nas a stronger affinity for the carbonic acid than potash. M S I64f BLEACHING. same effect in whitening it, as by exposing it to the action of the air and light in the field. The new method of bleaching was quickly and successfully introduced into the manufactories of France ; and almost as soon into those of Great Britain. It is now universally adopted. The advantages are, that the time required for bleach- ing is shortened in a surprising degree so that manufacturers experience a much quicker return of their capitals ; and that it may be carried on at all seasons of the year. The first way in which the oxymuriatic acid was applied in bleaching was in the liquid state ; that is, when water is impregnated with the gas. The goods were immersed in this liquid according to the nature of the objects to be bleached. Skeins of thread were suspended on frames in the tub in- tended to receive them ; cloth was rolled upon reels. When every thing was thus disposed, the tubs were filled with oxygenated muriatic acid, by introducing a funnel that descended to the bottom of the tub in order to prevent the dispersion of the gas. The cloth, or thread, was made to pass through the liquid by turning the frames, until it was judged that the acid was exhausted by acting on the colouring matter. But the volatility of this acid, and the suffocating nature of its vapours, which produced extremely noxious effects upon the health of the workmen, rendered its use very difficult, although very in- genious apparatus had been invented both by Ber- thollet and by Mr. Watts. It was also found diffi- cult to cause the acid to act upon all parts of the cloths equally, when they were stratified in the cis- terns with the acid. A considerable improvement was made in the BLEACHING. 16.5 apparatus by Mr. Rupp of Manchester, which is described in the Manchester Memoirs. Still it was found that the acid alone was apt to weaken the cloth, and that it injured the health of the workmen. At length it was discovered by some manufac- turers at Javelle, near Paris, that the addition of an alkali to the liquor deprived it of its suffocating effects, without destroying its bleaching powers. Potash was the alcali they employed ; and this so- lution was called the Javelle liquor. The invent- ors came into this country, and established a bleaching-work. The process was then carried on in open vessels ; and the bleacher was able to work his pieces in the liquid, and expose every part to its action without inconvenience. Although these advantages were unquestionably great, they were diminished by the heavy expense of the alcali, which was entirely lost. Also, the the potash, which added to the liquor, though it did not destroy its power of bleaching, diminished it; because a solution of the oxygenated muriate of potash, which differs from this bleaching-liquor in nothing but in the° proportion of alcali, will not bleach at all. This is a well-known fact; from which we might infer, that the oxygenated muri- atic acid will lose its power of destroying the co- louring-matter of vegetable substances, in propor- tion as it becomes neutralized. Mr. Tennant discovered that lime might be substituted for the potash, the oxymuriatic acid combining with all the alcaline earths, and forming oxymuriates which were soluble in water, and had the property of bleaching. This is the substance nov/ employed. If the oxygenated muriatic acid be passed through lime-water, it will combine with M 3 1©6 BLEACHING. the lime, and form oxymuriate of lime ; but as the water can only retain a small portion of lime, this was not found of much use. To cause a larger quantity of lime to combine with the oxymuriatic acid gas, the lime is mechanically suspended by agitation in the water into which the gas is made to passj so as to present fresh matter to the gas. By this means, the oxymuriatic acid combines with the lime, forming a compound soluble in the water : this is used as a bleaching-liquor. The oxygenated muriatic acid gas may also be combined with lime in a dry state. To effect this, the oxymuriatic acid gas is sent into a vessel contain- ing dry hydrate of lime (that is, lime slacked with water) : the powder is agitatedj and the gas com- bines with it to a certain amount, or till the hy- drate of hme becomes saturated. The compound is a soft white powder, possessing little smell. It is partially soluble in water, yielding a solution much the same as that obtained by the former process. Although most salts that are soluble in Water are capable of being formed again by evaporating the water, either in crystals or in a dry Saline mass, this is not the case with oxymuriate of lime. When- ever a solution of it is evaporated, part of the acid escapes, and the rest is mostly converted into mii- riatic acid ; so that ins,te?A of oa^i/jrmriate of lime, muriate of lime is obtained. Hence the dry salt cannot be obtained from the liquid solution. The dry oxymuriate of lime may be very Con- veniently transported without injury, an advantage not possessed by the acid alone, which cannot be transported without the loss of almost half its strength : but it must be observed that the dry salt is much imjiaired by being long kept. BLEACHING. l67 *'We have hitherto used the old term of oxynuiri- atic acid, because it is best known by this name in the bleaching processes ; but it will be remem- bered that this substance is now considered as a simple body, and is known by the name of chlorine. What has just been called oxymuriate of lime is known among modern cliemists by the term cldorate of lime. The oxymuriatic acid gas, or chlorine, may be procured by distilling muriatic acid in black oxide of manganese ; but to save the expense of first preparing the muriatic acid, the usual practice in bleaching is to mix three parts of black oxide of manganese with eight parts of muriate of soda or common salt, and five parts sulphuric acid, diluted with four parts water. To ascertain the strength of the liquid for bleaching, a solution of indigo in the sulphuric acid is employed. The colour of this is destroyed by the oxygenated muriatic acid; and according to the quantity of it that can be discoloured by a given quantity of the liquor, its strength is known. The linen is usually not immersed in the solution of oxymuriate of lime until after the fourth or fifth bucking ; because a great portion of the resin is removed cheaper by the alkaline leys, and washing in water. Tlie last operation in bleaching is souring, or steeping the linen in some sour liquid of a blood heat. For this purpose, formerly sour milk was em- ployed : but now sulphuric acid is used. Of this as much is put into water as will give it the acidity of vinegar. The linens are generally steeped about twelve hours, and are tlien well washed. This souring is essential to the procuring of a good white, but the theory of its action is not well understood. TNI 4 168 BLEACHING. Nothing now remains, in order to complete them for the market, but rubbing them with a strong lather of soap, washing, and blueing them. The alcali is one of the chief articles of expense used in bleaching : and it is a great object with the bleacher to recover the pure alcali from the leys which have been used. The sulphuret of lime, or the combination of sulphur and lime, which are both cheap articles, has been used in Ireland for bleaching, instead of potash. It was first proposed by Mr. Higgins, and it answers in some cases, particularly where the goods are intended for dying. The sulphiu'et of Hme is prepared as follows: — sulpliur in powder, four pounds j lime, well slaked, twenty pounds ; and water, sixteen gallons ; are to be well mixed, and boiled for half an hour in an iron vessel, stirring them briskly from tim.e to time. Soon after the agitation of boiUng is over, the so- lution of the sulphuret clears, and may be drawn off free from the insohible matter, which is consider- able, and whicli rests upon the bottom of the boiler. The liquor in this state is pretty nearly of the colour of small beer, but not quite so transparent. Sixteen gallons of fresh water are afterwards to be poured upon the insoluble dregs in the boiler, in order to separate the whole of the sulphuret from them. When this clears (being previously well agitated) it is also to be drawn off and mixed with the first liquor ; to these again, thirty-three gallons more of water may be added, which will reduce the liquor to a proper standard for steeping the cloth. Here we have (an allowance being made for evaporation, and for the quantity re- tained ill the dregs) sixty gallons of liquor from four pounds of sulphur. BLEACHING. IgQ Althougli sulphur, by itself, is not in any sensible degree soluble in water, and lime but sparingly so, water dissolving only about one seven hundredth part of its weight of lime ; yet the sulphuret of lime 19 highly soluble. After the paste used by the weaver has been re- moved, the linen is steeped in a solution of the sulphuret of lime, prepared as above, for about twelve or eighteen hours. It is then washed, and steeped in oxymuriate of lime. This process is repeated by six alternate immersions in each liquor. For the use of private families, where the linen is dirtied by perspiration or grease, it will be of great service towards rendering it white, to steep it for some time in a clear liquor, made by mixing one quart ofquick-Ume in ten gallons of water, letting the mixture stand for twenty-four hours, and then using the clean water drawn off from the lime. After the linen has been steeped in this liquor, it should be well washed as usual, but will require much less soap to be used. It is of great consequence in bleaching with the oxygenated muriatic acid, that it may be employed of a proper strength ; as a test to ascertain its strength, a solution of indigo in sulphuric acid is used. A certain quantity is put into a glass tube, and Oxygenated muriatic acid is added until the colour of the indigo is destroyed : by the quantity of acid necessary to destroy the colour, its strength is estimated. Steam has been employed in bleaching in France with great success. The process was brought from the Levant. Chaptal lirst made it known to the public. When an aicaline ley is boiled, a certain quau-tity of aicali always rises with ihe steam. The 170 BLEACHING. cloth is first immersed in weak caustic alcaline liquor, and placed over a chamber constructed over a boiler, into which is put the alcaline ley which is to be raised into steam. After the fire has been lighted, and the cloth lias remained exposed to the action of the steam for a sufiicient length of time, it is taken out, and immersed in the oxygenated muriate of lime, and afterwards exposed for two or three days on the grass. This operation, which is very expeditious, is suf- ficient for cotton ; but if linen-cloth should still retain a yellow tint, a second alcaline vapour-bath, and two or three days exposure on the grass, will be sufficient to give them the necessary degree of whiteness. Bleaching of Cotton. Cotton is a vegetable substance, and the pro- duction of a shrub that grows only in warm climates. It is a fine downy substance, in which the seeds of the plant are inclosed. Cotton, in its natural state, is generally of a dirty yellow, and opaque, being- covered with a colouring matter of an unctuous nature ; when this is removed, it is white and transparent. Cotton is easier to bleach than linen. The colouring-matter is dissolved by the action of alca- line leys and washing. Sometimes the oxymuri- atic acid is also used to expedite the process. Steeping in diluted sulphuric acid, is also used to dissolve the earthy matter that always remains after the immersion in alcaline ley; and as cotton is not so easily injured by acids as flax, more use is made of the acid than in the bleaching of linen. The BLEACHING. I7I action of steam is very efficacious in bleaching cottons. In bleaching cotton for calico-printing, a pure white is not so much sought for, as that the oil may be entirely extracted. In applying the alcaline ley, great care must be taken that no lime remains in suspension in the liquor, as it might be fixed in the cloths ; and when the sulphuric acid is used, a sulphate of lime would be formed, which in fact is a mordant for the madder ; hence the latter could not be discharged from those parts intended to be white. For the same reason, the oxy muriate of lime can- not be used, if madder is to be discharged from any part of the cloth. When this is the case, oxy- muriate of potash, or of soda, is substituted for oxymuriate of lime. Bleaching of Wool. The bleaching of animal substances is somewhat different from the processes employed for vegetable substances. Wool is a sort of very fine hair which covers the bodies of some animals. Each hair is hollow, and contains an oily matter. Wool is not easily acted upon by acids ; is unalter- able by water, cold or boiling; but may be entirely dissolved by strong alcaline leys. On this account, the latter must be used with great caution. Wool is oiled before it is combed and spun, and the first operation is to free it from the oil which it has thus acquired. This is called scouring. Stale urine, which contains ammonia or the volatile ^Icali, is mixed with water ; and the wool is im- 17^ BLEACHING. mersed in this for about twenty minutes, heated to 56° Fahr. It is then taken oat, drained, and rinsed in running water ; then put into the bath of urine, and washed again. This is sometimes re- peated a third time, and sometimes scouring with soap is used. Fulling the cloth adds also to its whiteness. Fulling is a species of scouring with a particular kind of earth called J}dler's earth. It effectually removes all grease, from the chemical affinity existing between the alumina contained in the fuller's earth and the oil of the cloth ; and thus dis- poses the fibres to be entangled and matted toge- tiier in the subsequent process of milling, employed to thicken the cloth, and render it stronger and firmer. Scouring entirely with soap is preferred when the articles are valuable. Sulphureous acid is also used for giving the last degree of whiteness. Sulphuring is performed in the following man- ner. The articles to be whitened are suspended iiopn poles across a chamber, constructed so as to be perfectly close. Into this chamber is pre- viously put a quantity of sulphur in dishes. When the cloth is in, the sulphur is set fire to, and the doors of t]ie chamber are accurately sliut, and all the interstices carefully stopt up, so as to exclude entirely the atmospheric air. The combustion of the sulphur produces a va- pour which is the sulphureous acidj this destroys the colouring matter of the wool, whicli is conse- quently rendered white. The time necessary for this process varies from six to twenty-four hours. The cloth is left in the clianiber for some time after the combustion of the sulphur has ceased 4 it BLEACHING. 173 is then taken out and rinsed, to remove the acid; and afterwards washed with soap, to give a degree of softness. This mode of bleaching by the combustion of sulphur is also used for other substances, as straw in the manufacture of hats, &c. A superior method of employing the sulphureous acid in bleaching is the following. Water is im- pregnated with the sulphureous acid, and tubs are filled with this; then the stuffs are drawn through it upon reels, till they are whitened. The sulphur- eous iicid is made by decomposing the sulphuric acid by the addition of any combustible matter capable of taking away a part of its oxygen. A cheap method of effecting this is by putting chopped straw, or saw-dust, into a nlattrass, and then pour- ing over it sulphuric acid, and afterwards applying heat. The sulphureous acid gas will be formed, but will be combined with the water in the vessel. The stuffs are then taken out, and left to drain upon a bench covered with cloth; a precaution which is necessary, because the wood might be decomposed by the sulphuric acid, and would stain the goods. They are afterwards washed in clear water. It is generally necessary to sulphur them twice before the white is sufficiently bright. Some- times Spanish white is put into the water used for washing them; and they are also aziired or blued bv disolvino^ some Prussian blue in the water. Nothing then remains to be done but dryings stretching J and pressing. Bleaching of Silk. Silk is an animal substance, and is prepared by a caterpillar, usually called the silk-worm. This 174^ BLEACHING. insect inhabits warm climates, and cannot be reared in this country without difficulty, nor in sufficient quantity for the purpose of procuring silk. The south of Europe and Asia are its proper countries. The silk is spun by the silk-worm in the form of threads of a semi-transparent matter, which it winds up round itself when it passes into the crysalis state. The threads, when formed, are connected together by a viscous substance, from which they must be separated before they can be wound off, by putting them into hot water. The silk itself is covered with a yellow varnish, which is soluble in alcaline leys ; and as this varnish conceals the lustre of the silk, it is necessary to detach it. Silk is itself soluble in strong alkaline leys ;| care must be taken, therefore, not to injure the silk in taking off the varnish. Water at a boil- ing heat has no action on silk ; but steam dissolves its varnish. In France they proceed as follows. They fill a boiler with a very weak solution of caustic soda, and place in a chamber connected with tlie boiler, the skeins of raw silk, wound on frames ; then they close the door of the chamber, and make the solu- tion in the boiler boil. Having continued the ebullition for twelve hours, they slacken the fire, and open the door of the chamber. The steam, which is always above 250° Fahr., will have dis- solved the gum of the silk. The skeins are then washed in warm water, wrung, and boiled a second time ', then washed again several times with soap, till they have acquired the necessary whiteness and softness. It is not possible, however, to give to silk all the necessary splendour by this process alone ; to com- plete it, the silk must be exposed to the action of the sulphureous acid, either in the form of gas, or combined with water, as directed for wool. Bleaching Prints and Frinted Books. An application has been made of the new mode o^ bleaching to the whitening of books and prints that have been soiled by smoke and time. Simple immersion in oxygenated muriatic acid, letting the article remain in it a longer or shorter space of time, according to the strength of the li- quid W'ill be sufficient to whiten an engraving. If it be required to whiten the paper of a bound book, as it is necessary that all the leaves should be moistened by the acid, care must be taken to open the book well, and to make the boards rest upon the edge of the vessel in such a manner that the paper alone be dipped in the liquid : the leaves must be separated from each other, so that they may be equally moistened on both sides. The liquor assumes a yellow tint, and the pa- per, becomes white in the same proportion j at the end of two or three hours the book may be taken from the acid liquor and plunged into pure water, with the same care and precaution as recommended in regard to the acid liquor, that the water may exactly touch the two surfaces of each leaf. The water must be renewed every hour, to extract the acid remaining in the paper, and to dissipate the disagreeable smell. By following this process, there is some danger that the pages will not be all equally whitened, either because the leaves have not been sufficiently separated, or because the liquid has had more ac- tion on the front margins than on those near the 176 BLEACHING. binding. On this account, the best way is to de- stroy the binding entirely, that each leaf may receive an equal and perfect immersion ; and this is the second process recommended by M. Chaptal. " They begin," says he, " by unsewing the book, and separating it into leaves, which they place in cases formed in a leaden tub, with very thin slips of wood or glass ; so that the leaves, when laid flat, are separated from each other by intervals scarcely sensible. The acid is then poured in, making it fall on the sides of the tub, in order that the leaves may not be deranged by its motion. When the workmaa judges, by the whiteness of the paper, that is has been sufficiently acted upon by the acid, it is drawn off by a cock at the bottom of the tub; and its place is supplied by clear fresh water, w^hich weakens and carries off the remains of the acid, as well as the strong smell. The leaves are then to be dried, and, after being pressed, may be again bound up. " The leaves may be placed also vertically in the tub ; and this position seems to possess some ad- vantage, as they will be less liable to be torn. " With this view, I constructed a wooden frame, which I adjusted to the proper height, according to the size of the leaves I wished to whiten. " This frame supported very thin slips of wood, leaving only the space of half a line between them. I placed two leaves in each of these intervals, and kept them fixed in their place by two small wooden wedges which I pushed in between the slips. " When the paper was whitened, I lifted up the frame with leaves, and plunged them in cold water, to remove the remains of the acid as well as the smell ; this process I prefer to the other. BLEACHING. 177 " By this operation, books are not only cleaned, but the paper acquires a degree of whiteness su- perior to what is possessed when first made. " The use of this acid is attended also with the valuable advantage of destroying ink-spots. This liquor has no action upon spots of oil or animal grease ; but it has been long known that a weak solution of potash will effectually remove stains of that kind, " When I had to repair prints so torn that they exhibited only scraps pasted upon other paper, I was afraid of losing these fragments in the liquid, be- cause the paste became dissolved. In such cases, I enclosed the prints in a cylindric glass vessel, which I inverted on the water in which I had put the mixture proper for extricating the oxygenated muriatic acid gas. This vapour, by filling the whole inside of the jar, acted upon the print, ex- tracted the grease as well as ink-spots, and the fragments remained pasted to the paper." Bleaching of Paper. The oxygenated muriatic acid has also been ap- plied to the bleaching of paper, which it has ren- dered considerably more expeditious. Bleaching of old printed papers to he xvorked up again. — Boil the paper for an instant in a solution of soda, rendered caustic by potash. Steep it in soap water, and then wash it, after which tlie pa- per may be reduced to a pulp by the paper-mill. Bleaching of old written papers to he worked again. — Steep the papers in a cold solution of sul- phuric acid in water, after which wash them before they are taken to the mill. If the acidulated wa- ter be heated, it will be the more effectual. VOL. II. N 17^ DYEING, Bleaching of printed papers "without destroying the texture qf^ the leaves. — Steep the leaves in a caustic solution of soda, and afterwards in one of soap. Arrange the sheets alternately between cloths in the same manner as paper-makers dispose their sheets of paper when delivered from the form. Put the leaves in a press, and they will be- come whiter, unless they were originally loaded with printers' ink or size. If this should not com- pletely effect the whitening of the leaves, repeat, the process a second, or even a third time. Bleaching coloured rags to make ichite paper. — Soak or macerate the rags sufficiently ; put them into a solution of caustic alcali, and then into the oxygenated muriatic acid ; and, lastly, steep them into diluted sulphuric acid. DYEING. Dyeing is the art of extracting the colouring principle from different substances, and transfer- ring them to wool, silk, cotton, or linen. AVlien other matters are coloured, the process is called staifiing. In dyeing, the colouring matter is not merely de- posited on the stuff, but is firmly attached to it by chemical combination depending on an affinity subsisting between them. If the colouring matters were merely spread over the surface of the fibres of the cloth, the co- lours produced might be very bright, but they would not be permanent, since they would be rubbed off, and would disappear when the cloth Vvas washed, or even by exposure to the weather. Dye- ing is, therefore, a chemical process, consisting in combining a certain colouring matter with fibres of cloth, 'the colouring matters are, for the most part, extracted from animal and vegetable sub- stances, and have usually the colour which they give to the cloth. The particles of these colouring matters appear to be transparent, because the original colour of the cloth will appear through them. The colour of dyed cloth, therefore, does not depend upon the dye alone, but also upon the previous colour of the cloth. Thus, if the cloth be black it will not re- ceive a dye of any colour ; and hence it is neces- sary, that the cloth should be white, if we wish to dye it of a very bright colour. The colouring matter, or dye-stuff, must be dis- solved in some liquid, that the particles may be precipitated upon the cloth ; and it is essential that its affinity for this solvent should not be so strong as for the cloth to be dyed. Thus the facility with which cloth imbibes a dye depends upon two things ; namely, the affinity be- tween the cloth and the dye stuff, and that between the dye stuff and its solvent. Much of the accu- racy of dyeing depends upon preserving a due proportion between these two affinities. If the affinity between the dye-stuff and cloth, compared with that between the dye-stuff and the solvent be too great, the cloth will receive the dye tOb quickly, and the colour will be apt to be Unequal : and if the affinity between the dye-stuff and the solvent be greater than between the dye-stuff and the cloth, the latter will scarcely receive the dye, br, at least, very faintly. JVool has the strongest affinity for colouring- matters ; silk the next strongest ; cotton lias much less affinity ; and linen has the least of all. Hence the dye-stuff for cotton or linen shotild be dissolvetl N 9 180 DYEING. ill substances which they have less affinity for, than when silk or wool are to be dyed. Thus iron dis- solved in the sulphuric acid may dye wool ; but when it is intended to dye cotton and linen by iron, the latter should be dissolved in the acetous acid. There are few colouring substances that have, of themselves, so strong an affinity for cloth as to answer the purpose of dyeing so as to remain per- manent ; and, on this account, an intermediate substance is employed, that has a decided attraction for both the colouring matter and the cloth, thus serving as a bond of union between them. This substance is previously combined with the cloth, which is then dipped into the solution containing the dye-stuff. The dye-stuff combines with the in- termediate substance, which being firmly combined with the cloth, secures the permanence of the dye. Substances employed for this purpose are deno- minated mordants. Instead of this some prefer the term basis. The most important part of dyeing consists in the proper choice, and the proper application of mordants; as upon them, the permanency of every dye depends. What has been said respecting the application of colouring matters applies equally to the application of mordants. They must be pre- viously dissolved in some liquid, which has a weaker affinity to them than the cloth has, to which they are to be applied ; and the cloth must be dipped, or even steeped in this solution, in order to saturate itself with the mordant. The mordants are earths, metallic oxides, tan, and oil. Of the earths, alumine is the most useful. It is applied in the state of sulphate of alumine, or common alum j and in that of acetate of alumine. DYEING. 181 When alum is used as a mordant, it is dissolved in water, and sometimes a quantity of tartar is added. The cloth is put into this solution, and kept till it has absorbed as much alumine as is ne- cessary. It is then taken out, and is washed and dried. A quantity of alumine has by this process combined with the fibres of the cloth, which is perceived by the latter weighing more than before. The addition of the tartar, or tartrate of potash, is made on two accounts ; the potash which it contains combines with the sulphuric acid of the alum, and thus prevents that very corrosive substance from injuring the texture of the cloth : the tartareous acid, on the other hand, combines with part of the alumine, and forms a tartrate of alumine, which is more easily decomposed by the cloth than alum. Acetate of alumine is used as a mordant for cotton and linen, which have a much less affinity than wool for alumine. The alumine is retained less powerfully in a state of combination by the acetic than by the sulphuric acid ; and, therefore, cotton and linen are better able to separate it and attach it : also the acetic acid being volatile, gradually leaves the earthy basis, and allows the alumine to unite to the stuff*. This mordant is now prepared by pouring acetate of lead into a solution of alum j on which a double decomposition takes place ; the sulphuric acid com- bines with the lead, and the sulphate of lead pre- cipitates in the form of an insoluble powder, while the alumine combines with acetous acid, and remains in the liquor. This mordant gives a richer colour than alum. Liine is also sometimes employed as a mordant : but it does not answer so well in general, not giving so good a colour. It is used either in the state N 3 of limip v/at;er, or as sulphate of lime dissolved in water. Although all the metallic oxides have an affinity for cloth, only two, the oxides of tin and of iron, are much used as mordants. The oxide of tin is one of the most valuable mor- dants, and is the only one by which scarlet, the brightest of all colours, can be produced. It was first brought to London by Karsten, a German, in 1543, which period forms an epoch in the history of dyeing. Prous^ 1]^S shown that tin has two oxides. The first, pr grey oxide, consists of seventy parts of tin, ai:id thirty oxygen : the second, or w^hite oxide, of sixty parts of tin, and forty oxygen. The first ox- ide absorbs oxygen rapidly from the air, andbecomes converted into the white oxide. It is, therefore, the white oxide alone that is the real mordant ; since if the first were applied to cloth, as it proba- bly often is, it must soon be converted info the white pxide by absorbing oxygen. Tin is used as a mordant in three states ; dis- solved in nitro-muriatic acid, in acetous acid, and in a mixture of sulphuric and muriatic acids. That commonly used by the dyers, ^nd called by them sphit of tin, is the nitro-muriate. It is pre- pared by dissolving granulated tin in very dilute nitric acid, or what is called single aquafortis : and a quantity of muriate of soda, or muriate of am- monia, is added. These salts are decomposed by the nitric acid, and the muriatic acid is set free, sometimes to economize the nitric acid, a quan- tity of sulphuric acid is added, just sufficient to saturate the base of the muriate of soda. When nitro-muriate of tin is used as a mordant, it is dissolved in a large quantity of water, and tartar is added. The cloth is then put in and kept till it is saturated. A double decomposition takes place ; the nitro-muriatic acid combines with the potash of the tartar, Avhile tlie tartareous acid dis- solves the oxide of tin. When tartar is used, therefore, in any considerable quantity, the mor- dant is not a nitro-muriate, but a tartrate of tin. The mur'iu-sidphate of tin, produced by dissolving tin in muriatic acid, combined with about one- fourth of its weight of oil of vitriol, is also a valuable mordant, and is preferable to the last for some pur- poses J it is also less expensive. The oxide of iron is also a very useful mordant, and all kinds of cloth have a strong affinity for it. The permanency of the iron spots on linen and cotton is a sufficient proof of this. Iron, as a mor- dant, is used in different states. Wool is dyed generally by means of the sulphate of iron, which may also be used for cotton. Acetate of iron, pre- pared by dissolving iron in vinegar, sour beer, Sec, is preferable for some purposes. The pyro-lig- neous acid, which differs from the acetic only in having in combination a certain quantity of empy- reumatic oil, is at present preferred to the sulphuric, or acetic. The astringent principle, or tannin, is also em- ployed as a mordant, and has a strong affinity for cloth, and also for colouring matters. An infusion of nut-galls, sumach, oak bark, or any other sub- stance containing tannin, is made in water, and the cloth is kept in it till it has absorbed a sufficient quantity oi tannin. Silk has so strong an affinity for tannin, that manufacturers sometimes employ this circumstance to increase the weight of their silk. A compound mordant is sometimes produced by impregnating the cloth first with oil, then with the N 4" 184 DYEING. astringent principle, and, lastly, with the aluminous mordant. This is employed in dyeing the Adria- nople red. Several other substances are used as mordants occasionally, either as principals, or to facilitate the combinations of others with the cloths ; such as ni- trate of bismuth, oxide of arsenic, corrosive sub- limate, acetate of lead, sulphate, or acetate of copper, &c. The chief use of mordants is to render the dyes permanent, but they have also considerable in- fluence on the colour produced : thus, the same colouring matter will produce very different dyes, according to the mordant used to fix it. If the aluminous mordant be used for cochineal, the colour will be crimson ; but if the oxide of iron be used for the same colouring matter, black will be the result. It is necessary, therefore, to choose such mor- dants and colouring matters as together shall pro- duce the desired colour. And this principle enables us also to produce various colours with the same dye-stuff, only by changing the mordant. It is probable that the whole of the surface of the fibres of cloth are not covered by the colouring matters precipitated upon them ; but that the particles of colour are at some distance from each other. For cloth may be dyed different shades of the same colour; that is, it may be dyed deeper a second time than at first, by increasing the quan- tity of colouring matter, which could not be tlie case if the whole surface were covered. Another circumstance renders this opinion probable ; all those colours which dyers call compound are made by dyeing the cloth first one colour, and then another : thus, green is got by dyeing cloth first blue and then vellow. DYEING. 185 In dyeing, the water employed should be as pure as possible, and the exact temperature in each process should be attended to. The dye-houses should be spacious, light, and airy, and cleanness is essentially necessary. The stuffs are supported in the cauldrons, or baths, by proper apparatus, and are drawn through them by a winch, or reel. Of Dyeing Red, The colouring matters employed for dyeing red are cochineal, kermes, madder, lac. Brazil-wood, logwood, and earth amus. Cochineal is a species of insect (the coccus cactiy Lin.) brought from America. The decoction of it affords a very bright crimson colour, inclining to violet. When alum is added to this decoction, it combines wdth its colouring matter, and forms a red precipitate. Muriate of tin gives a still more beautiful colour. Kermes is also an insect found in several parts of Asia, and the south of Europe, which furnishes a red dye, by some thought not inferior to cochi- neal, but which has not been so much used since the introduction of the latter. Madder is the root of a plant (rubia tinctoriuniy Lin.) The colouring matter of madder is extracted by water, either cold or hot, and precipitates of various shades of red may be obtained by alum, chalk, acetate of lead, and muriate of tin. Lac is a colouring matter of animal origin, pro- duced in the East Indies, from tlie coccus lacca^ a small winged insect. This insect forms cells for its young, as regular as the honey-comb, but diffe- rently arranged ; and the lac is procured from the substance of which these cells are made. The whole matter of these cells is called stick lac ; when the 1 86 DYEING "s >- ^?^ red colouring matter is extracted by water, what remains is a resinous substance called shell lac^ used for various purposes, as varnishes, sealing wax, &c. Water dissolves lac, and the decoction is of a deep crimson colour. The precipitate, with alum or nitro-muriate of tin, forms a fine red. Brazil-wood is an article used in dyeing. It is the central part of a large tree, that grows in Brazil. It is heavier than water, and affords a decoction of a red colour with water. The precipitate, with alum and nitro-muriate of tin, is a fine red. Peach-wood gives a colour inferior to Brazil, and also in smaller quantity. Logwood affords a colouring matter extensively used in dyeing. It is very heavy, and sinks in water. Its decoction is yellow, but by alum be- comes violet or purple ; by sulphate of iron it becomes black. Carthamus is the flower of a plant cultivated in Spain and the Levant. It contains two colouring matters ; a yellow, which is soluble in water ; and a red, which is insoluble in water, but soluble in alcaline carbon ats. The red colouring matter of carthamus, extracted by carbonate of soda, preci- pitated by lemon-juice, and ground with talc, con- stitutes the rouge employed as a cosmetic: the fineness of the talc, and the proportion of it mixed with the carthamus, occasion the difference between the cheaper and dearer kinds of rouge. Wool is died scarlet, which is the most splendid of all reds, by cochineal. Alum will do as a mor- dant for fixing the red ; but nitro-muriate of tin, or what is still better, the murio-sulphate of tin, are now used as preferable mordants. To die wool scarlet, a bath is made by mixing pure tartar with a little cochineal and nitro-muriate of tin 5 but as DYEINGf. 1P7 the red prodiiced by cochineal alone is rather a crimson than a scarlet; and as the colour of scarlet is, in flict, crimson and yellow, some yellow dye, or fustic, turmeric, or quercitron bark, is added to the cochineal in the first bath. Into this the cloth is put, and boiled for two hours. It is then waslied, and afterwards put into a second bath of cochineal, which is called the red- dening. When crimson is the colour to be given to the cloth, the tin mordant is the best; but some- times the dyers use the alum for this purpose, and then a decoction of cochineal. The addition of archil and potash renders the crimson darker, and gives it more bloom, but this is very fugitive. For paler crimsons, some madder is substituted for a portion of the cochineal. Wool is dyed madder-red, by boiling it first two or three hours with alum and tartar, and then in a bath of madder. Silk may be dyed crimson with cochineal or Brazil-wood, and sometimes carthamus is used. The nitro-muriate of tin is the best mordant, but alum may be also used. Madder does not give a colour sufficiently bright. Poppy colour, cherry, rose, and flesh colour, are given to silk by carthamus or Brazil-wood. When the carthamus is employed, an alcaline solution is made, and as much lemon-juice as will give it a fine cherry-red is poured into it. It is extremely difficult to give silk a scarlet, and it is scarcely possible to give it a full scarlet. The murio-sulphate of tin, as a mordant, is first used, then the bath of cochineal and quercitron, and lastly, the cochineal bath alone. A colour approach- ing to scarlet may also be given to silk, by dyeing- it first crimson, then dyeing it with carthamus, and lastly yellow, without heat. 188 DYEING. Cotton and linen are dyed red with madder. Cochineal, which gives so fine a red to wool, by the nitro-muriate of tin, communicates only a dirty red to cotton and linen, by the same means. Madder reds are of two kinds. 1. The common madder red, which is formed by impregnating the cotton or linen with galls, and afterwards alumed, and then putting them into the madder bath. 2. The Adrianople, or Turkey red. This process was brought from the East. It is more durable and more beautiful than the common red. The cloth is first impregnated with oil, then with galls, and lastly, with alum. It is then boiled for an hour, in a decoction of madder, which is commonly mixed with a quantity of blood. After the cloth is dyed, it is plunged into a soda ley, in order to brighten the colour. The chief difficulty is in the application of the mordant, which is the most complicated employed in the whole art of dyeing. Cotton may be dyed scarlet by the murio-sul- phate of tin, cochineal, and quercitron bark j but the colour is extremely fugitive. Of Dyeing Yellow. The chief yellow dyes are M^eld, sumach, fustic, turmeric, and quercitron bark. Weld is a vegetable that grows commonly in this country. Sumach is a shrub growing naturally in the South of Europe. Fustic is the wood of a tree wliich grows in the West Indies. Querciti^on is the bark of a tree which is a native of North America. DYEING. 189 It is not possible to give to cloth a permanent yellow colour without the use of mordants. Alum is the most usual mordant. TFool is dyed yellow by weld, by the use of alum and tartar. Quercitron bark gives nearly the same colour, but more abun- dantly, and it is rather cheaper than weld. The process is as follows : boil the cloth for an hour or more in a solution of alum, and then immerse it in a bath of quercitron bark. Next add a small quan- tity of clean powdered chalk, and continue the boiling for eight or ten minutes. The yellow thus given will be as good as that obtained from weld. If very bright yellows are required, the tin mor- dant must be usedj and sometimes alum is added to the tin. If an addition of tartar be made to the mordant, the yellow will have a slight tinge of green. If an orange or an aurora be required, a small portion of cochineal must be added. Silk used formerly to be always dyed yellow with weld, but quercitron bark is now found to answer equally well, and at less expense. The proportion should be from one to two parts of bark to twelve pounds of silk, according to the particular shade of colour wanted. The bark, powdered and tied up in a bag, should be put into the dyeing vessel whilst the water is cold, and as soon as it becomes blood warm, *the silk previously alumed should also be put in and dyed as usual, and when the shade is required to be deep, a little chalk or pearl-ashes may be added towards the end of the operation. When very lively yellows are required, a little of the raurio-sulphate of tin may be employed as a mordant in addition to the alum. Annotto com- 1§0 byfitNG. municates an aurora colour to silk, the colour of the annotto is extracted by means of alcali. To dye cotton and linen yellow, proceed as fol- lows. Take a sufficient quantity of the acetate of alumine, formed by dissolving one pound of sugar of lead, aiid three pounds of alum, and the cotton or linen '.eing properly cleansed, immerse it in this mordant (which ought to be blood warm) for two hours, let it be then taken out and moderately pressed or squeezed over a proper vessel, to prevent the unnecessary waste of the mordant, dry it in a stove heat, and soak it again in the aluminous mor- dant; it is then taken out, and again pressed and squeezed as before ; after which, without being rinsed, it is thoroughly wetted in as much, and only as much, lime-water as will conveniently suf- fice for that purpose, and afterwards dried. The soaking in the acetate of alumine maybe again re- peated, and if the shade of yellow is required to be very bright and durable, the alternate wetting with lime water and soaking in the mordant may be re- peated three or four tim.es. Thus a sufficient quan- titv of alumine is combined with the cloth, and the combination is rendered more permanent by the addition of some lime. The dyeing both is pre- pared by putting 12 or 18 parts of quercitron bark, (according to the depth of the shade required,) tied up in a bag, into a sufficient quantity of cold water. Into this bath the cloth is to be put, and turned round in it for an hour, while its temperature is gradually raised to about 120*^, it is then to be brought to a boiling heat, and the cloth allowed to remain in it after that only a few minutes. If it be kept long at a boiling heat, the yellow ac- quires a shade of brown. DYEING. 191 To dye nankeen yellow, boil the cotton in a so- lution of carbonate of potash, and then dip it in a solution of the red sulphate of iron. Of Dyeing Blue. There are but few substances capable of furnish- ing blue dyes. The only vegetable products are indigo and wood. Indigo is a rich blue colour procured from the fecula of a species of plant that is cultivated in America, and also in the East Indies. The colouring matter is extracted by water, and is at first green, but immediately absorbs oxygen, and then assumes a blue colour. It becomes at the same time insoluble in water, but is soluble in sulphuric acid. As indigo has a very strong affinity for wool, silk, cotton, and linen, a mordant is unnecessary in dye- ing with it. The colour is very permanent, because the indigo being already saturated with oxygen, to which it owes its blue colour, is little liable to be decomposed. But it is essential that the indigo be applied in a state of solution in order to attach itself to the cloth. A solution of indigo in the sulphuric acid is used for dyeing wool ; this is called ScLvon bluet and it gives a very beautiful colour. But it will not do for dying cotton or wool, because their affinity for indigo is not sufficiently great to enable them to decompose the sulphate of indigo. To dye by the sulphate of indigo, dissolve oile })art of indigo in four parts of concentrated sul- phuric acid ; add to the solution one part of dry car- bonate of potash, and dilute the whole with eight times its weight of water. Boil the cloth for an 192 DYEING. hour in a solution of five parts of alum, and three of tartar, for every thirty-two parts of cloth. The clotli is then to be put into a bath of sulphate of indigo, diluted according to the strength of shade required, and kept till it has acquired the desired colour. The use of the alum and tartar is not to act as mordants, but to facilitate the decomposition of the indigo. The alcaii is added to the sulphate for the same reason. Another use of these sub- stances is, that they protect the cloth from the action of the sulphuric acid, by neutralizing part of it, otherwise the texture of the cloth might be injured. This, however, is not the most common method o[ dyeing by indigo. The usual method is to deprive the indigo of the oxygen which has been combined with the green fecula, and to which it owes its blue colour, and thus reduce to the green state again. It is then capable of being dissolved in water by means of the alcalies or alcaline earths, which act upon it very readily in that state, To dye wool blue, indigo is mixed with wood, bran, and madder, vegetable substances which readily undergo fermentation ; and the whole is boiled together, stirring the mixture frequently. JBy this a fermentation takes place, and the oxy- gen is separated from the indigo. Quick lime or alcaii is then tlu'own in, which dissolves the green base of the indigo. The solution of indigo is apt to run into the putrid fermentation, which is known by the putrid vapours whicli it exhales ; the green colour then disappears, and, indeed, the colouring matter is decomposed. This danger is prevented by adding more lime to correct the putrescent tendency. Sometimes the fermentation does not proceed with sufficient activity, and then more bran DYEING. 195 or wood is to be added. Wlien the wool or cloth is to be put into the indigo vat to be dyed, it should be wrung out of tepid water, and then in- troduced into the vat, where it should be kept for a longer or shorter time according to the strength of shade required. After being taken out, it is ex- posed to air, when the green colour which it had imbibed in the vat is changed to a blue by the absorption of the oxygen of the atmosphere. It is then to be carefully washed. Woad itself contains a colouring matter exactly similar to indigo, and indigo may be extracted from it, but the quantity is small. Cotton and linen are dyed blue by putting the indigo into a solution of some substance that has a stronger affinity for oxygen than the green bases of indigo. Green sulphate of iron, and metallic sulphurets answer this purpose, the green sulphate attracts the oxygen from the indigo, and reduces it to the green state, in which it is dissolved by lime added to the solution. The cloth is then put into the bath. Silk is dyed blue by indigo fermented by bran and madder, and the indigo dissolved by potash. If the shade required be dark, it is dyed first with archill, which is called giving it a ground colour.n Of dyeing Black. The substance that produces the black dye is the ta nno'gallate oi'h'on. Decoctions of many vege- tables strike a black with a solution of the red oxide of iron. Of these nut-galls give the most copious precipitate. Logwood is generally employed as an auxiliary, because it communicates lustre, and adds consider- VOL. II. O 19*4 DYEING. aljly to the fullness of the black. The decoction of logwood which is reddish becomes black by sulphate of iron. To dye cloth or wool black, the first process generally is to dye it blue, which renders the black to be given more intense. If the cloth be coarse, and the blue dye too expensive, a brown dye may be given by means of walnut peels. It is then boiled for two hours in a decoction of nut galls, and then for two hours more in a bath composed of logwood and sulphate of iron, at a scalding heat, but not boiled. During the operation, it must be frequently exposed to the air. The common pro- portion are five parts of galls, five of sulphate of iron, and thirty of logwood, for every 100 of cloth. For coarse cloths the previous blue dye is omitted. The cloth is then washed and fulled. Silk is dyed black as follows. After boiling it with soap, it is galled, and afterwards washed. It combines with a considerable portion of the astrin- gent principle, and increases in weight. It is then dipped into a bath of sulphate of iron and gum arable. Cotton and I'men are first dyed blue, then steeped in a decoction of galls, and alder bark. It is then put into a batli of acetite of iron, taken out and exposed to the air. This operation is repeated several times. Of dyeing Compotincl Colours. Compound colours are produced either by mix- ing together two or more simple ones, or by dyeing cloth first one simple colour and afterwards another. Greens are formed of blues and yellows. Wool is dyed green by dyeing it first blue of a depth of shade sufficient for the required kind of green. It is then washed and boiled in a bath of weld and tartar, or any of the processes used for dyeing blue and yellow may be used. Various shades will be given by different proportions of the dyeing ma- terials. The green called Saa:on gren? is obtained by solutions of indigo in sulphuric acid, sometimes quercitron bark is used. Another process for Saxon green is by the quercitron bark, and then a bath of the murio-sulphate of tin and alum with sulphate of indigo. Purples, violets. Sec. — All the shades of these colours are formed of blue and red. Sometimes the cloth is dyed blue and then scarlet, and some- times cochineal is mixed with sulphate of indigo, and the purple dyed at once. Silk is dyed first by cochineal and afterwards by indigo. Cotton and linen are dyed blue, then galled, and boiled in loffwood. li ,, .," Orange colours are produced by mixtures of yellow and red. Wool is first dyed scarlet and then yellow. Olive is blue combined with red and yellow. Cinnamon colour is given to wool by dyeing it first with madder, then yellow. Silk is dyed the same colour by logwood. Brazil-wood, and fustic. Cotton and linen receive a cinnamon colour by weld and madder. Brown is given to cloth by quercitron bark, or by walnut peels. When walnut peels, or the green covering of the walnut, are first separated, they are white internally, but soon assume a brown or even a black colour on exposure to the air. They readily give up their 0 ^ 196 CALICO PRINTING. colouring matter to water. It is common to keep them in water for a year before they are used. Wool is dyed brown with them by steeping in a decoction for a length of time proportioned to the depth of colour required. The same colouring matter is found in the root of the walnut-tree, but in smaller quantity. Other trees, as the bark of the birch may be used for dyeing browns, and in these cases it is probable that the colouring matter is combined with the tanning principle, and this may be the reason why no mordant is necessary, both the cloth and colouring matter having a strong affinity for tannin. Drab colours are dyed by combining brown oxide of iron with the cloth, and then the yellow of quercitron bark. The strength of shade will be more or less, by varying the quantity of the mor- dant, w^hen the proportion is small the colour in- clines to olive or yellow, on the contrary the drab may be deepened or saddened, as the dyers term it, by mixing a little sumach with the bark. CALICO PRINTING. Calico isa species of cotton cloth ornamented with coloured patterns. The name is derived from Cali- cut, a district of India, where it was first made, and from whence it was formerly imported. The art of making calicoes had been practised there from time immemorial, but it is scarcely, a hundred years since it was known in Europe; it has al- ready risen to such perfection as to equal if not exceed the manufactures of India, in the elegance of the patterns, the beauty and permanance of the colours, and the expedition with which the different operations are carried on. CALICO PRINTING. 197 The process of calico-printing consists in impreg- nating those parts of the cloth which are to receive the coloured pattern with a mordant, and then dye- ing the cloth by the usual methods. The dye is firmly fixed to that part only where the mordant has been applied ; and, although the whole cloth has received the tint, yet the colour will be easily discharged from the unmordanted parts by washing, and exposing on the grass to the sun and air for some days with the wrong side uppermost. Thus, suppose a pattern had been applied to white cloth with a solution of acetite ofalumine, and that then the whole was dyed with madder ; when taken out of the dye-vat the whole cloth would be red ; but, by washing and bleaching, the madder will be dis- charged from every part of the cloth except where the acetite ofalumine had been applied ; and, con- sequently, the pattern alone will appear red. In the same manner the patterns may be applied of any other colour by varying the dye, as quercitron bark or weld for yellow, &c. Two mordants are particularly employed in ca- lico-printing, acetite of alumine, and iron dissolved in some vegetable acid. The acetite of alumine is made by a double de- composition of alum and sugar of lead. When iron is used as a mordant, it is dissolved in vinegar, soured beer, or pyroligneous acid ; and it is, there- fore, an acetite of iron mixed with a portion of tar- trite, gallate, and, perhaps, other salts of the metal. When the colour of the required pattern varies in different places, this effect is produced on the cloth, by impregnating the several parts with vari- ous mordants. Thus, if one part is printed with acetite ofalumine, and another with acetite of iron, o 3 1^ CALICO PRINTING. and the whole cloth afterwards dyed with mad- der and bleached, tlie pattern will appear in red and brown. The mordants are applied to the cloth either by a pencil, or by means of blocks on which the pat- tern is cnt. Care must be taken that the printing from the block does not spread, or that the impres- sions from the several blocks do not interfere with one another when more than one is apphed. For this purpose it is necessary, that the substance used as mordants should have a degree of consistence that may prevent them ft'om spreading. Flour paste, or starch, is mixed with the mordant when it is applied by blocks, and gum arable when it is but on by a pencil. This thickening reqiiires exact- ness : if too little is used, the pattern will spread ; and, if too much, the cotton will not receive a suf- ficient quantity of the mordant, and will take the dye imperfectly. In order that the impression given by the blocks with the mordant may be seen easily before it is dyed, the mordant is tinged with some colouring matter that wdll not remain fixed. Decoction of Brazil-wood is used for this purpose. Before printing, the cotton cloth is well bleached and calendered, and laid smooth on a table : the blocks are applied by hand, and struck with a mallet. The cotton is then dried well in a room with a stove, which not only fixes the mordant more securely, but drives off part of the acetous acid from its base, by which the mordant will com- bine in a greater proportion, and more intimately with the cloth. To discharge the paste and gum used with the mordant, the cloth is next to be washed with warm CALICO PRINTINe. 199 water and cow-dung ; this, also, discharges such parts of the mordant as are not properly fixed, enough being still left to fix the dye. The cloth is then rinsed in clear water. It is then dyed in the usual manner. The principal dye-stuffs used by calico-printers are indigo, madder, quercitron bark, and weld. After dyeing, the cloth is well washed, exposed on the grass, and bleached ; by which all the parts not touched by the mordant are restored to their original whiteness. In this manner various colours may be given by one dyeing, merely by varying the mordant. Thus, if one pattern be printed with alum alone, a second with a mixture of alum and iron liquor, a third v.'ith iron liquor alone, and a fourth with iron li- quor and galls, and the piece be afterwards dyed with quercitron or weld, and the ground bleached in the usual manner ; the first pattern will be pure yellow, the second will be olive, the third of a dark drab colour, and the fourth nearly black, while the ground will be white. As indigo does not require any mordant, it is applied at once, either by a pencil or by a block and paste. But, as has been mentioned under dye- ing, indigo will not combine with the cloth except in its disoxygenated or green state ; and, if applied thus by the pencil, it would return to the blue state before it had time to fix upon the stuff. The in- digo is, therefore, prepared by boiling with potash, made caustic by quicklime, to which is added orpiment for the disoxygenation of the indigo. This solution is thickened with gum. It must be excluded from the air, otherwise it would attract oxygen and return to the blue or insoluble state. Dr. Bancroft proposed substituting brown sugar o 4 . . 500 CALICO PRINTING. for orpiments, as it is equally efficacious in disoxy- genating the indigo, and will also serve instead of gum. Some calicoes are printed only with one colour ; others have two ; others three, or more, even to the number of eight, ten, or twelve. The smaller the number of colours, the fewer are the processes. To give an example where six colours are used. 1. A nankeen yellow, of various shades down to a deep yellowish brown or drab, is given by acetite of iron put on with gum or paste, and afterwards plunged into the potash ley. 2. Yellow, by a mordant of acetite of alumine, the dyeing by quercitron bark and bleaching. 3. Red, by the last process, only madder is sub- stituted for the bark. 4. Light blue is given by making a block for all those parts that are to be white, and printing by it on the cloth a composition of which wax is the principal ingredient, or pipe- clay and paste. The cloth is then dyed in a cold indigo vat, and the wax removed by hot water. 5. Lilac flea-brown, and blackish brown, are given by acetite of iron, and dyeing afterwards with madder. 6. Dove-colour and drab, by acetite of iron and quercitron bark. The same mordant will frequently do tor several colours. Thus, suppose one part of the cloth should be printed with acetite of alumine, another with acetite of iron, and a third with a mixture of these two mordants, and the whole afterwards dyed with quercitron bark ; then the following colours would appear, viz. yellow, drab, olive ; and various depths of shade will be given by varying the pro- portions ot" iron in the mordant. TANNING, 201 If some parts of the yellow be covered over with the indigo liquor, applied with a pencil, it will be converted into green. By the indigo, also, any parts that are required to be blue may be pencilled. If j instead of quercitron bark, the cloth printed with the three mordants just mentioned be dyed with madder, then the colours exhibited will be red, brown or black, and purple. Other processes are still more complicated when a great number of colours are required. New mordants are applied to parts of the pattern alrea- dy printed, and the cloth again dyed, by which those parts only receive a new colour. Sometimes the dye stuff and the mordant are mixed together in the first instance, and printed on the cloth, which is a great saving of time and ex- pense ; but the colours thus produced on the cloth are not permanent: washing, or even exposure to the air frequently destroys them. TANNING. Tanning is the art of converting the raw skins of animals into leather. The skin is composed chiefly of two parts, a thin white elastic layer on the outside, which is called the epidermis, or cuticle ; and a much thicker layer, composed of a great many fibres, closely inter- woven, and disposed in different directions: this is called the cutisy or true skin. The epidermis is that part of the skin which is raised in blisters. It is easily separated from the cutis by maceration in hot water. It possesses a very great degree of elasticity. It is totally inso- lubje in water and alcohol. Pure fixed alcalis dis- solve it completely, as does lime likewise though slowly. S02 TANNING. When a portion of cutis is macerated for some hours in water, with agitation and pressure, the blood, and all the extraneous matter with which it was loaded, are separated from it, but its texture remains unaltered. On evaporating the water em- ployed, a small quantity of gelatine may be ob- tained. No subsequent maceration in cold water has any farther effect ; the weight of the cutis is not diminished, and its texture is not altered ; but if it be boiled in a sufficient quantity of water, it may be completely dissolved, and the whole of it, by evaporating the water, obtained in the state of gelatine. It was mentioned, when treating of chemistry, that gelatine wdth tannin^ or the tanning principle o^ vegetables, formed a combination, which is inso- luble in water. Upon this depends the art of making leather ; the gelatinous part of the skin combining with the tannin of the bark usually employed. The process which has long been used in this country is as follows ; the leather tanned in Eng- land consists chiefly of three sorts, known by the name o^ butts or backs, hides, and skins. Butts are generally made from the stoutest and heaviest ox hides, and are managed as follows : after the horns are taken off, tlie hides are laid smooth in heaps for one or two days in the summer, and for five or six in the winter ; they are then hung on poles, in a close room called a smoke-house, in which is kept a smouldering fire of wet tan ; this occasions a small degree of putrefaction, by which means the hair is easily got offj by spreading the hide on a sort of wooden horse or beam, and scraping it with a crooked knife. The hair being taken off, the hide is thrown into a pit or pool of water, to TANNING. 203 cleanse it from the dirt, &c. which being done, the hide is again spread on the wooden beam, and the grease, loose flesh, extraneous filth, &c. carefully scrubbed out or taken off; the hides are then put into a pit of strong liquor, called ooze^ prepared in pits kept for the purpose, by infusing ground bark in water ; this is termed colouring ; after which they are removed into another pit called a scower- ing, which consists of water strongly impregnated with vitriolic acid, or with a vegetable acid, prepared from rye or barley. This operation (which is called raising)^ by distending the pores of the hides, occa- sions them more readily to imbibe the ooze, the ef- fect of which is to combine with the gelatinous part of the skin, and form with \i leather. The hides are then taken out of the scowering, and spread smooth in ai pit commonly filled with water, called a binder, with a quantity of ground bark strewed between each. After laying a month or six weeks, they are taken up ; and the decayed bark and liquot being drawn out of the pit, it is filled again with strong ooze, when they are put in as before. With bark between each hide. They now lie two or thi^e months, at the expiration of which the saitie oper- ation is repeated ; they then remain four or five months, when they again undergo the same process, and after being three months in the last pit, aTe com- pletely tanned; unless the hides are so remarkably stout as to want an additional pit or layer. The whole process requires from eleven to eighteen months, and sometimes two years, according to the substance of the hide, and discretion of the tanner. When taken out of the pit to be dried, they are hung on poles, and after being compressed by a steel pin, and beat out smooth by wooden hammers, called hattSy the operation is complete ; and when 204 T4.NNING. thoroughly dry, they are fit for sale. Butts are chiefly used for the soles of stout shoes. The leather which goes under the denomination of hideSj is generally made of cow hides, or the lighter ox hides, which are thus managed. After the horns are taken off, and the hides washed, they are put into a pit of water, saturated with lime, where they remain a few days, when they are taken out, and the hair scraped off on a wooden beam, as before described ; they are then washed in a pit, or pool of water, and the loose flesh, &c. being taken off, they are removed into a pit of weak ooze, where they are taken up, and put down (which is technically termed handling') two or three times a-day, for the first week ; every second or third day they are shifted into a pit of fresh ooze, somewhat stronger than the former ; till at the end of a month or six weeks they are put into a strong ooze, in which they are handled once or twice a-week with fresh bark for two or three months. They are then removed into another pit, called a layer, in which they are laid smooth, with bark ground very fine, strewed between each bide. After remaining here two or three months, they are generally taken up, when the ooze is drawn out, and the hides put in again with fresh ooze and fresh bark, where, after lying two or three months more, they are completely tanned, except a few very stout hides, which may require an extra layer: they are then taken out, and hung on poles, and being hammered and smoothed by a steel pin, are, when dry, fit for sale. These hides are called crop hides ; they are from ten to eighteen months in tanning, and are used for the soles of shoes. Skins is the general term for the skins of calves, seals, hogs, dogs, &c. These, after being TANNING. 205 washed in water, are put into lime pits, as before mentioned, where they are taken up and put down every third or fourth day, for a fortnight or three weeks, in order to destroy the epidermis of the skin. The hair is then scraped off, and the excres- cences being removed, they are put into a pit of water impregnated with pigeon dung, called a grainer, forming an alcaline ley, which in a week or ten days soaking out the lime, grease, and sa- ponaceous matter (during which period they are several times scraped over with a crooked knife, to work out the dirt and filth), softens the skins, and prepares them for the reception of the ooze. They are then put into a pit of weak ooze, in the same manner as the hides, and being frequently handled, are by degrees removed into a stronger, and still stronger liquor, for a month or six weeks, when they are put into a very strong ooze, with fresh bark ground very fine, and at the end of two or three months, according to their substances, are sufficiently tanned : when they are taken out, hung on poles, dried, and are fit for sale. These skins are afterwards dressed and blacked by the curriers, and are used for the upper leathers of shoes, boots, &c. The lighter sort of hides, called dressing hides, as well as horse hides, are managed nearly in the same manner as skins ; and are used for coach- work, harness work, &c. &c. As the method of tanning above described, and all others in general use, are extremely tedious and expensive in their operation, various schemes at different times have been suggested to shorten the process, and lessen the expense. Much hght has been thrown by modern che- mists upon the theory of tanning, and considerable 2015 TANNINE . improvements have been made in the practice of this art. M. Seguin, in France, has particularly distinguished himself by his researches on thissu]b- ject, and mucli improved the art in his country. In 179<5, Mr. William Desmond obtained a patent for practising Seguin's method in England. He obtained the tanning principle, by digesting oak bark, or other proper material in cold water, in an apparatus nearly similar to that used in the salt- petre works : that is to say, the water which has remained upon the powdered bark for a certain time, in one vessel, is drawn off by a cock, and poured upon fresh tan: this is again to be drawn off, and poured upon other fresh tan ; and in this way the process is to be continued to the fifth vessel. The liquor is tlien highly coloured, and and marks from six to eight degrees upon the hy- drometer for salts. This he calls the tanning lix- ivium. The criterion for ascertaining its strength is the quantity of the solution of gelatine which a given quantity of it will precipitate. Isinglass is used for this purpose, being entirely composed of ge- latine. And liere it may be observed, that this is the mode of ascertaining the quantity of tanning principle in any vegetable substance, and, conse- quently, how far they may be used as a substitute for oak bark. The hides, after being prepared in the usual way, are immersed for some hours in a weak tanning lix- ivium of only one or two degrees ; to obtain which, the latter portions of the infusions are set apart, or else some of that which has been partly exhausted by use in tanning. The hides are then to be put into a stronger lixivium, where, in a few days, they will be brought to the same degree of saturation TANNING. 207 with the liquor in which they are immersed. The strength of the hquor will by this means be consi- derably diminished, and must, therefore, be renew- ed. When the hides are by this means completely saturated, that is to say, perfectly tanned, they are to be removed, and slowly dried in the shade. It has been proposed to use the residuum of the tanning lixivium, or the exhausted ooze (which contains a portion of Gallic acid, this forming a constituent part of astringent vegetables), for the purpose of taking off the hair ; but tliis liquor seems to contain no substances capable of acting upon the epidermis, or of loosening the hair ; and when skin is taken off by being exposed to it, the effect must really be owing to incipient putre- faction. The length of time necessary to tan leather completely, according to the old process, is cer- tainly a very great inconvenience ; and there is no doubt but that it may be much shortened by fol- lowing the new method. It has been found, how- ever, that the leather so tanned has not been so durable as that which has been formed by a slower process. The public is much indebted to Sir Humphry Davy, for the attention which he has paid to this subject. From his excellent paper " On the Con- stituent Parts of Astringent Vegetables,'* in the Philosophical Transactions, we present the reader with the following extract. " In considering the relation of the different facts that have been detailed, to the processes of tanning and of leather-making, it will appear suf- ficiently evident, that when skin is tanned in as- tringent infusions that contain, as well as tannin, extractive matters, portions of these matters enter, 208 TANNING. with the tannin, into chemical combination with the skin. In no case is there any reason to beUeve that galUc acid is absorbed in this process ; and M. Seguin's ingenious theory of the agency of this substance, in producing the de-oxygenation of skin, seems supported by no proofs. Even in the formation of glue from skin, there is no evidence which ought to induce us to suppose that it loses a portion of oxygen ; and the effect appears to be owing merely to the separation of the gelatine, from the small quantity of albumen with which it was combined in the organized form, by the sol- vent powers of water. *' The different qualities of leather made with the same kind of skin, seem to depend very much upon the different quantities of extractive matter it contains. The leather obtained by means of in- fusions of galls, is generally found harder, and more liable to crack, than the leather obtained from the infusion of barks ; and in all cases it contains a a much larger proportion of tannin, and a smaller proportion of extractive matter. " When skin is very slowly tanned in weak so- lutions of the barks, or of catechu, it combines with a considerable proportion of extractive matter ; and in these cases, though the increase of weight of the skin is comparatively small, yet it is rendered per- fectly insoluble in water, and is found soft, and at the same time strong. The saturated astringent infusions of barks contain much less extractive matter, in proportion to their tannin, than the weak infusions; and when skin is quickly tanned in them, common experience shows that it produces leather less durable than the leather slowly formed. ** Besides, in the case of quick tanning by means of infusions of barks, a quantity of vegetable ex- TANNING. 209 tractive matter is lost to the manufacturer, which might have been made to enter into the composi- tion of his leather. These observations show, that there is some foundation for the vulgar opinion of workmen, concerning what is technically called the feeding of leather in the slow method of tan- ning J and though the processes of the art may in some cases be protracted for an unnecessary length of time, yet, in general, they appear to have ar- rived, in consequence of repeated practical expe- riments, at a degree of perfection which cannot be very flir extended by means of any elucidations of theory that have as yet been known.'* As a vast quantity of bark may easily be ob- tained in countries that are covered with natural forests, such as many parts of America, New Hol- land, &c. it has been suggested, as a method of lessening the expense of freight in bringing it over, to make an extract from the bark, which might be very easily transported, and which would serve the purpose of the tanner as well as the bark itself. It was first suspected by Sir Joseph Banks, and afterwards confirmed by the experiments of Sir Humphry Davy, that a substance called catechu, or terra Japonica, brought from the East Indies, con- tained a vast quantity of tannin ; so much so, that it far excels every other known substance in this respect, Onepoun.-l of catecliu contains as much tannui as eight or ten pounds of common oak bark, and would consequently tan proportionately as much more leather. It is an extract made from the wood of a species of mimosa, by decoction and sub- sequent evaporation. Oak bark being a very expensive article in the process of tanning, various substances have been proposed as substitutes for it. All the parts of ve- VOL. ]I, p 210 TANNING. getables which are of an astringent nature, contain tannin (which may be known by their giving preci- pitates with gelatine, insoluble in water), and will answer this purpose. The leaves, branches, fruit, flowers, of a vast number of plants; every part of the oak, as the leaves and acorns, oak saw-dust, and the barks of almost all trees, contain more or less tannin. Mr. Biggins made a great many experiments upon the quantity of tanning principle in various barks, from which he constructed the following table. Tanning principle (in grains\ from half a pint of infusion and an ounce of solution of glue. ^ Bark of elm, - - 28 ' oak, cut in winter, - 30 horse-chesnut, . 30 beech. . 31 willow (boughs) - 31 1 elder. - 41 * plum-tree, - 58 willow (trunk). - 52 sycamore. - 53 birch, - 54> cherry-tree. • 59 saUow, - 59 mountain-ash. - 60 poplar. - 76 hazel. - 79 ash, - - 82 Spanish chesnut. - 98 smooth oak, - - 104 oak, cut in spring. - 108 Huntingdon, or Leices- . tershire willow. - 109 sumach, - 158 mi CURRYING. The art of currying consists in rendering tarinetl skins supple and of uniform density, and iiiipregr nating them with oil, so as to render them in a great degree impervious to water. The stronger and thicker hides are usually em-? ployed for making the soles of boots r.nd shoes, and these are rendered fit for their several purposes by the shoemakers after they are tanned ; but suph skins as are intended for the upper leathers ^nd quarters of shoes, for the legs of boots, for coach find harness leather, saddles, and other things, must be subjected to the process of currying. These skins after coming 'from the tanners, hav- ing many fleshy fibres on them, are well soaked in common water. They are then taken out aqcj stretched upon a very even wooden horse ; where with a paring knife all the superfluous flesh is scraped ofi\ and they are again put into soak. After the soaking is completed the currier takes them again out of the water, and having stretched them out, presses them with his feet, or a flat stone fixed in a handle, to make them more supple, and to press out all the filth that the leather may have acquired in tanning, and also the water it has absorbed in soaking. The skins are next to be oiledf to render them pliant and impervious to wet. After they are half dried, they are laid upon tables, and first the grain side of the leather is rubbed over with a mixture of fish oil and tallow ; then the flesh side is im- pregnated with a large proportion of oil. After having been hung up a sufficient time to dry, they are taken down and rubbed, pressed, and folded in various directions, and then spread out, when th^Y p 2 Sl^ MANUFACTURE OF SODA, are rolled with considerable pressure upon both sides with a fluted board fastened to the operator's hand by a strap ; by this means, and by repeating the rolling, a grain is given to the leather. After the skins are curried, it may be required to colour them. The colours usually given to them are black, white, red, green, yellow, &c. If the skins are to be blacked, the process varies according: to the side of the skin to be coloured. Leather that is to be blacked on the flesh side, which is the case with most of the finer leather intended for shoes and boots, is coloured with a mixture of lamp black, oil, and tallow, rubbed into the leather. And what is to be coloured on the grain side is done over with chamber lye, and then with a solution of sulphate of iron, which turns it black. MANUFACTURE OF SODA. Soda, or the mineral alcali, (described above, under Chemistry) is sometimes found in a native state, as in the lakes of Natron in Egypt, which are dry in the summer season ; the water leaving after evaporation a bed of soda, or, as it is there called, natron, of two feet in thickness. A marine plant, called the Salsola soda, whicli grows among the cliffs on the sea coast, seems to be endowed by nature with the property of decom- posing the salt water, that is, of separating the muriatic acid from the soda, which latter it absorbs. This plant is collected by the Spaniards with great care, and burnt for the manufacture of barilla, which is a carbonate of soda mixed with various impurities. Soda is also procured in a still more impure state, by the burning of the sea weeds on our own MANUFACTURE OF SODA. 213 shores, particularly in Scotland, from which is pro- j duced a substance called help. But the demand for a pure carbonate of soda having become very considerable of late years, from its great utility in many arts and processes, various means have been tried for procuring it by decom- posing the salts, in which it exists, combined with acids. Muriate of soda has been decomposed for this purpose. The following method is described in Nicholson's Journal. Solutions of 500lbs. of sulphate of soda*, and 560lbs. of American potash, are made to boil, and are then mixed. As soon as the mixture boils, it is conveyed into a cistern of wood, lined with lead, half an inch thick, which is fixed in a cool place. Sticks of wood are then placed across the cistern, from which slips of sheet lead, two or three inches wide, are hung into the fluid, at four inches distance from each other. When all is cool, the fluid is let off, and the chrystallized salt is detached from the slips of lead, and the bottom of the trough. The salt is then washed, to free it from impurities, after which it is transferred again into the boiler, dis- solved in clear water, and evaporated by heat. As soon as a strong pellicle is formed, it is suffered to cool so far that the hand may be dipped into it without injury, and the heat is kept at that temper- ature as long as effectual pellicles continue to be formed over the whole surface of the boiler, and then fall to the bottom. When no more are formed, the fire is withdrawn, and the fluid ladled out into the cistern to crystallize. The sulphate of potash, &c. which had been deposited, is then taken out of * Sulphate of soda is sold cheap by the bleachers, who save it as the residue in decomposing common salt by sulphuric acid with manganese. p 3 2l4i MAKtl^ACTUilE of POTASH. the boiler, and put aside. By this process from 136 to lo9lbs. of soda may be obtained from 1 OOlbs. Of sulphate of soda. MANUFACTURE OF POTASH. Potash, or the fixed vegetable alcali, exists as an ingredient, in very small quantity, in many mine- rals. It is also obtained from the tartar, or from lees of Wine, in which it is called salt of tartar. But the great supply of this substance is procured from the ashes of burnt vegetables. In many districts of England and Ireland they burfii the common fern to ashes, which they mould up with a little water, into balls of about three or foiir inches in diameter ; these are called ash balls, and are the rudest preparation of this alcali. . The potash of commerce, or Mack potash, i(s always procured from the combustion of wood, and can, therefore, only be made in those countries where wood is very plentiful^ as Poland, Russia, and Ger- manyw This country is chiefly supplied from Ame- rica. The ashes of burnt wood are put into a cistern with water^ and a strong lixivium is made. After a time, tlie water, holding the alcali in solu- tion, is drawn oflj leaving the impurities behind. Potash is converted into a purer state by calcining it in a reverberatory furnace. It becomes then dry, poix)us, considerably caustic, extremely deliques- cent, and of a beautiful bluish colour, from which it is called pearl ash. All these are carbonates of potash. To obtain potash in a state of perfect purity, or uncombined with carbonic acid, the carbonate must be boiled with twice its weight of quicklime to de- REFINING METALS. 515 prive it of the carbonic acid ; then to free it from other impurities, it must be dissolved in spirits of wine, (which dissolves alcalis and no other salt) and the solution evaporated to dryness. It is then pure and powerfully caustic. REFINING METALS. The term refining signifies the purification of some substance : but we mean to confine it at pre- sent to the separation of gold, silver, and copper from each other, and obtaining each of them in a pure state. Cupellation. Gold and silver being the only metals capable of withstanding the action of very strong heat, are therefore called perfect metals. All other metals are reduced to the state of oxides when exposed to a violent fire with access of air. Gold and silver may, therefore, be purified from all the baser metals by keeping them fused till the alloy be destroyed : but this process would be very expensive, from the great consumption of fuel, and would be exceed- ingly tedious. A shorter and more advantageous method of performing this operation has been dis- covered. A certain quantity of lead is added to the alloy of gold and silver, and the whole is exposed to the action of the fire. Lead is one of the metals which is most quickly converted by heat into an oxide, which is easily melted into a semi- vitrified, and powerful vitrifying matter, called litharge. By increasing the proportion of imperfect metals, it prevents them from being so p 4 216 CUPELLATION. well covered and protected by the perfect metals j and by uniting with these imperfect metals, it com- municates to them its property of being very easily oxidated. By its vitrifying and fusing property, which it exercises with all its force upon the cal- cined and naturally refractory parts of the other metals, it facilitates and accelerates the fusion, sco- rification, and separation of these metals. The lead, which in this operation is scorified, and scorifies along with it the imperfect metals, separates from the metallic mass with which it is then incapable of remaining united. It floats upon the surface of the melted mass, and becomes semi-vitrified. But the litharge so produced would soon cover the melted metal, and by preventing the access of air would prevent the oxidation of the remaining imperfect metals. To remedy this, such vessels are employed as are capable of imbibing and absorbing in, their pores, the melted litharge, and thus remove it out of the way ; or, for large quantities, vessels are so constructed, that the fused litharge, besides being soaked in, may also drain off, through a channel made in the corner of the vessel. Experience has shown that for this purpose, ves- sels made of lixiviated wood or bone-ashes are most proper. These vessels are called cupels^ and this process is called cupellation. The cupels are flat and shallow. The furnace ought to be vaulted, that the heat may be reverberated upon the sur- face of the metal during the whole time of the operation. Upon this surface a crust or dark coloured pellicle is continually forming. In the instant when all the imperiect metal is destroyed, and, consequently, the scorification ceases, the sur- face of the perfect metal is seen, and appears clean and brilliant. This forms a kind of fulguration, or i REFINING METALS. 217 corruscation, called lightning. By this mark the metal is known to be refined. Purification of gold by a7itimony. When gold contains only a small quantity of alloy, it may be separated from them by melting it in a crucible that will hold twice its quantity at least, and throwing upon it, whilst in fusion, twice its weight of crude antimony (sulphuret of antimony). The crucible is then to be covered, and the whole is to be kept in a melting state for some minutes ; and when the surface sparkles, it is quickly to be poured into an inverted cone, which has been pre- viously heated and greased. By striking the cone on the ground, the metal will come out when cold. The compact mass consists of two substances ; the upper part is the sulphur of the crude antimony, united with the impure alloy ; and the lower part is the gold, united to some of the regulus of anti- mony, proportionable to the quantities of metals which have been separated from the gold, which are now united with the sulphur of the antimony. This regulus of gold may be separated from the regulus of antimony by simple exposure to less heat than will melt the gold, because antimony is volatile in such a heat, and is then dissipated. If the gold is not sufficiently purified by this first pro- cess (which is often the case,) it must be repeated a second, and even a third time. When a part is dissipated, more heat is required to keep the gold in fusion ; therefore, the fire must be increased to- wards the end of the operation. The purification is completed by means of a little nitre thrown into the crucible, which effectually calcines the remain- ing regulus of antimony. Sometimes, after these 218 PARTING. operations, the gold is found to be deprived of much of its usual ductility ; this however is easily re- stored to it, by fusing it with nitre and borax. The first part of this process is founded on a pro- perty of sulphur, by which it is incapable of uniting with gold, and is strongly disposed to unite with all other metalUc substances, excepting pla- tina and zinc ; and also upon the property of sul- phur, that it has less affinity with regulus of anti- moiiy than with any metallic substance with which it can unite. Hence, when gold, alloyed with ^Iver, copper, iron, lead, &c. is fused together with sulphuret of antimony, these latter metals unite witli the sulphur of the antimony, while the regu- litm part, disengaged from them by its sulphur, unites with the gold. The sulphur of the antimony, though it unites with the baser metals, does not destroy them, but forms with them a scoria, from which they may be separated by treatment as an ore. Parting. When the quantity of silver united to the gold is considerable, they may be separated by other processes. Nitric acid, muriatic acid, and sulphur, which cannot dissolve gold, attack silver very easily ; and, therefore, these three agents furnish methods of separating silver from gold, which operation is called parting. Parting by nitric acid is the most convenient, and, therefore, most used ; and is even almost the only one employed by goldsmiths and coiners. Wherefore it is called simply, parting. That made with muriatic acid is only made by cementation, and is known by the name oi' concentrated parting. PARTING. 219 Lastly, parting by sulphur is made by fusion, and is, therefore, called dry parting. Parting gold from silver by iiitric acid or aqua j^Wf^.— Although parting by nitric acid be easy, it cannot succeed, or be very exact, unless we attend to some essential circumstances. The gold and silver must be in a proper proportion ; for if the gold be irl too great a quantity-, the silver would be covered and guarded by it from the action of the acid ; therefore, when assayers do not know the pro- portion of gold to silver in the mass, they rub the mass upon a touch-stone (which is usually composed of black basalt, though black pottery will do very weil^) so as to leave a maiiv upon it; they then make similar marks with the proof-needles, (which are needles composed of gold and silver alloyed together in graduated proportions,) and by comparing the colour of the several marks, they discover the probable sicaie of admiJiture. If the trial shows that in any given mass the silver is not to the gold as three to one, this mass is improper for the operation of parting by aqua fortis. In this case, tiie quantity of silver neces- sary to make any alloy of that proportimi must be added. This operation is called quart