GIFT OF HAND-BOOK MINERAL ANALYSIS BY PRIEDRICH WOHLER, PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF GOTTINQEN. EDITED BY HENRY B. NASON, PROFESSOR OF CHEMISTRY IN THE RENSSELAER POLYTECHNIC INSTITUTE, TROY, NEW YORK. PHILADELPHIA: HENRY CAREY BAIRD, INDUSTRIAL PUBLISHER, 406 Walnut Street. mi. Entered according to Act of Congress, in the year 1870, by HENRY CAREY BAIRD, in the Office of the Librarian of Congress. All rights reserved. ; / i* : * PHILADELPHIA: COLLINS, PRINTER, 705 JAYNE STREET. PREFACE TO THE AMERICAN EDITION. The present edition of WOHLER'S HAND-BOOK OF MINEKAL ANALYSIS is a translation of the last German with some changes and additions. A few of the methods here described might have been omitted, and newer, in some cases preferable ones, given instead, but it has been thought advisable to present the book in nearly the same form as the ori- ginal. Free use has been made of the excellent translation of the first edition by Dr. A. W. Hoffman, and frequent reference had to the French edition by Messrs. Gran- deau and Troost, from which many of the illustrations of apparatus have been taken. The work is not intended to take the place of larger and more complete works on analysis, but it is believed that it will be found a convenient companion to these in the laboratory. H. B. N. TROY, N. Y., Dec. 15,1870. 339665 PREFACE. THIS collection of examples for illustrating the most important processes for determining the composition of mineral substances, is designed chiefly for use in the laboratory. It is drawn up under the impression that it is easier for most minds to obtain a clear insight into general relations and laws by the study of special cases, than, inversely, to acquire a knowledge of individual cases by first directing the attention to general rules. An endeavor has been made to arrange the book in such a manner as still to leave enough to demand the re- flection of the student and the explanations of the teacher ; the latter also must point out the authority for the individual methods here given, and also which he considers the best. FRIEDKIOH WOHLER. CONTENTS. PAGE Preface to the American edition ' . ' . . r . . 3 Preface . . . . . . .'.' * . . . 4 Chloride of sodium . . . . . » .13 Chloride of silver ' . . . ./.•'.'.'. 14 Sulphate of soda 15 Tartrate of potassa and soda > . 16 Sulphate of soda and ammonia . . ' . . . . 18 Sulphate of potassa and magnesia . . . .19 Carbonate of potassa and magnesia . . , . .21 Epsom salt and Glauber's salt . . . . . " . 21 Phosphate of soda and .ammonia . '. . '. '. . 22 Phosphate of magnesia and ammonia . . * . 23 Chlorides of potassium, sodium, and magnesium . . . 25 Dolomite and bitter-spar .. 27 Bone-ash 27 Apatite „ • . .29 Barite, celestite, and gypsum ...... 31 Alumina-alum ....... . . 33 Iron-ammonia-alum ........ 34 Alumina-chrome-alum . . . . .34 "Wavellite and phosphates of alumina in general . . 36 Spinel. (Alumina and magnesia in general) ... 37 Alumina and sesquioxide of iron 38 Phosphoric acid and sesquioxide of iron .... 41 Hematite and liraonite V '. . . » • • 42 Magnetite . '. '. . \ \ ". ^ * . 44 Siderite '. ; ". . . ',« • . . • • 46 Bog iron-ore . '* . '.- . . . . '\* . 49 Wet assay of iron "• . "» *• • . • • 50 yi CONTENTS. PAQB Iron assay 52 Sulphate of copper, 53 Chalcopyrite • .53 Sphalerite, or blende 55 Smithsonite 57 Brass 58 Oxides of manganese, iron, and zinc . . . . .59 Cadmium and zinc . . 60 Cadmium and copper ........ 60 Galenite . . .'*•".' 61 White lead V '. ". . . '.* . . .62 Pyromorphite . . . . . . . . . 63^ Silver and lead . . . . . . . . • ~ 65 Silver and copper ........ 66 Silver assay .... " .^ . . .. . 67 Gold and copper ^ . . '._",'. ' . . . 68 Gold and silver .' f . . 69 Amalgams .......... 70 Mixtures of protoxide of mercury, minium, and cinnabar . 72 Tin and copper . 72 Tin and lead 73 Bismuth, lead, afid tin 74 Bismuth and copper 76 Schweinfurt green 76 Arsenic and lead 77 Arsenic and tin . .78 Tartar-emetic 80 Antimony and lead 80 Bournonite » . 82 Zinkenite >. .. ... 83 Berthierite • . ... . . 84 Ked silver-ore •, ? .84 Tin and antimony .... . ;" "• • 87 Arsenic and antimony ... V V '.. . 88 Arsenic, antimony, and tin . . . "./.*.". 90 Tetrahedrite . 91 CONTENTS. Vii PAOE German silver (argentan) . . ».. ' . . . . 97 Niccolite •• -. '-. . . . . ;.' -»...*, • . 98 Smaltite , . , . ,. I. ;, . 103 Cobaltite -. -. /. -'• •-..- . ... .. .104 Manganese and cobalt, or nickel .'..*"•. . . 107 Meteoric iron .. .. ',. ...» ?. 109 Platinum metals and ore . .* . "<•<: :' >.' ., . Ill Iridosmine and platinum residues . .' .. .. .'. . 118 Thallium '... •; •' \.~- "' '..,. '•'... '. 126 Indium . . . . 7 . . . . . . 133 Tellurium ore , ^ ...... 138 Natrolite, thomsonite, &c. . . . • *>•' •**'. ; . 141 Ilvaite . . . . i . *; -^ ; . ^ * 143 Chrysolite (olivine) -. •, •..• . 144 Datolite } .. •,. ••« -fc -. . 145 Ulexite .. .. ,. '••:.-.• . * ••*. ..-..*>, . 146 Orthoclase . . . ... .... . . . . . . . 147 Pyroxene, amphibole, garnet, idocrase, epidote . -•„ . 150 Beryl ,. ,.. ^ .. ,. , 151 Topaz. .. ,. ;. .* /*' 'v' : .- -i,.,' «*-.;••• fv .;-.. 153 Fluorite . . . , . % . . . . . . ". . ' -. i-154 Cryolite 155 Zircon . . . 156 Cerite * ; . ;-. 158 Gadolinite 1. .. .. \ -. 164 Thorite ...» :* . >. -> 167 Triphylite . . . ... ..•'=*'.,.•'* -* 168 Titanite (sphene) . -<-t ,v .-:•:, -.. •-... •; 171 Menaccanite. (Titanic iron.) -. -..'-%_ *. . 172 Eutile ....".. 1 . . . .175 Columbite. (Niobite.) ,> /. ,; ^l| '- . • 176 Tantalite . . . =. ... -;. ' . ; . . 177 Wolframite ... .-<. .... -.. ;.'. -.:• . 178 Scheelite .... .,--..,.,;• . . 181 Wulfenite (molybdate of lead) . r \ ' ' -. • v.-' . 181 Molybdenite . . . . "..'.; . .184 Brown iron-ore, containing vanadium . . •» ". . 185 yiii CONTENTS. PAGE Vanadinite. (Yanadate of lead) 187 Chroraite. (Chrome-iron-ore) 187 Chromate of lead Uraninite 192 Seleniferous deposit from sulphuric acid chambers . . 195 Selenium soot 197 Clausthalite. (Selenide of lead) . . . . .198 Cast-iron 20° Ash of the refining-hearth 205 Glass 209 Clay 210 Common limestone, hydraulic limestone, marl . . 21JL Iodide, bromide, and chloride of sodium . . . . 212 Crude common salt 214 Incrustations from salt-pans 215 Mineral waters, well-waters, saline springs . . . .216 Soils 224 Ashes of plants 228 Guano 232 Oxalate and phosphate of lime 238 Alkalimetry 240 Valuation of manganese ores 248 Chlorimetry 250 Analysis of nitre . . . . . . .252 Gunpowder . . . ... . . . 254 Hydrocyanic acid . 255 Ferrocyanide of potassium . . . . . . 257 Examination for arsenic in cases of poisoning . . . 258 Examination for phosphorus in cases of poisoning . . 278 Silicates 285 Separation of the iron and manganese .... 295 Analysis of the materials soluble in nitrate of ammonia . 296 Examination of the volatile materials in silicates . . 300 Equivalent weights of the elements ..... 304 Equivalent weights of compound bodies .... 306 INDEX 309 HANDBOOK OP MINERAL ANALYSIS 1. CHLORIDE OF SODIUM. Nad. PERFECTLY pure crystallized common salt is strongly heated, to expel adhering moisture, weighed, dissolved in water, the solution slightly acidified with nitric acid, heated, and the chlorine precipitated by nitrate of sil- ver, the liquid being at the same time violently agitated by stirring. When the chloride of silver has com- pletely separated, leaving the liquid clear, it is filtered off and washed (with as little exposure to light as pos- sible), first with hot water acidified with nitric acid, in order that it may not pass through the filter and sub- sequently with pure water. When the precipitate has been perfectly dried it is removed as completely as possible from the filter, and fused, in a weighed porce- lain crucible, over the gas-lamp. The filter is com- pletely incinerated by itself; the ashes are placed upon the cooled chloride of silver, and heated, first with a little nitric acid, in ordei" to oxidize the reduced silver, 2 14 " ' CHLCtHIpE 'O.F .-SILVER. and afterwards with a few drops of hydrochloric acid ; the excess of acid having been expelled, the chloride of silver is again heated to fusion, allowed to cool, and weighed. 100 parts of AgCl contain 24.73 chlorine (and 75.27 silver). The liquid in which the chloride of silver floats can also be decanted with care on a filter. The chloride can be collected in a weighed porcelain crucible, after washing, dried, gently calcined, and weighed. The chloride of silver being a little volatile, there is danger of loss if it is heated to fusion. The filter is burned by itself and the ashes weighed with the. calcined chloride. For the determination of the sodium, another weighed portion of chloride of sodium is carefully moistened, in a weighed platinum crucible, with concentrated sul- phuric acid ; after some time, a gentle heat is applied until all the chlorine has been expelled in the form of hydrochloric acid, when the excess of sulphuric acid is carefully evaporated, and the residual sulphate of soda finally heated to redness, a fragment of carbonate of ammonia being placed in the crucible, to decompose any acid salt. From the weight of the sulphate of soda, that of the sodium is calculated. 2. CHLORIDE OF SILVER. AgOI. In order to determine the composition of chloride of silver, a weighed quantity of pure silver is dissolved in dilute nitric acid, the solution precipitated with dilute hydrochloric acid, and the precipitated chloride of silver treated as in No. 1. Or a weighed portion of fused chloride of silver may be heated with a low flame; in a bulb-tube, through SULPHATE OF SODA. Fig. 1. 15 which a stream of hydrogen is passed until it is com- pletely reduced to metallic silver, which is then weighed. 3. SULPHATE OF SODA. NaO;S03-flOHO. For the determination of the water, a weighed quan- tity of the salt is gradually and carefully heated in a platinum crucible, until the whole of the water is expelled, to insure which the heat is finally raised to ignition. The sulphuric acid is determined by dissolving the salt in water and precipitating with chloride of barium. The liquid is then warmed, and must not be filtered until the sulphate of baryta has completely separated. The clear liquid is then poured upon the filter, without the precipitate, which is stirred up with hot water, again allowed to subside, the clear liquid being poured upon the filter, and the precipitate once more treated in the same way before it is thrown upon the filter, in order that none may pass through the pores of the 16 ROCHELLE SALT. paper. When perfectly washed, it is dried, separated as much as possible from the filter, the latter being completely incinerated, and its ashes added to the pre- cipitate, which is then ignited and weighed. 100 parts of sulphate of baryta contain 34.29 of sulphuric acid, or 13.71 of sulphur. The amount of soda is deter- mined by difference. 4. TARTRATE OF POTASSA AND SODA.* Seignette-salt ; Eochelle-salt, (K0; NaO, T + 8 HO). The estimation of the water requires the cautious application of heat for a long period. The salt fuses even below 100°, and enters into ebullition at 120°, but does not lose the whole of its water till heated to 215°. To determine the bases, the salt is ignited, the alka- lies dissolved out of the carbonaceous mass by dilute hydrochloric acid, and the filtered solution evaporated to dryness; the mixed chlorides are heated to dull redness in a covered platinum crucible and weighed. They are then dissolved in a little water, and the solu- tion mixed with a moderately concentrated solution of bichloride of platinum. The solution, with the sus- pended precipitate, is evaporated to dryness on the water-bath, the dry mass digested for some time with alcohol, and the potassio-chloride of platinum col- lected upon a filter which has been dried at 100°, and weighed. The filtrate, which contains the sodio- chloride of platinum, must still have a distinct yellow color. The platinum-salt is washed with alcohol, * Prepared by saturating a hot mixture of water and powdered tartar with carbonate of soda, filtering, and crystallizing. ROCHELLE-SALT. 17 dried at 100°, and weighed. 100 parts correspond to 16.03 of potassium, or 19.33 of potassa. The amount of the chloride of sodium may be ascertained by deducting the weight of the chloride of potassium from that of the mixed chlorides. It is safer, however, to control this result by direct deter- mination, for which purpose the filtered liquid is care- fully evaporated to dryness, and the mass strongly ignited in a covered platinum crucible; in order to insure the complete decomposition of the chloride of platinum, the ignition should be repeated, with addi- tion of a few crystals of oxalic acid. From the cooled mass, the chloride of sodium is extracted with water. When, as is frequently the case, the two alkalies are present as sulphates, together with an excess of acid, the greater portion of the latter is expelled by careful evaporation, and the saline mass afterwards ignited in a covered platinum crucible, into which small fragments of carbonate of ammonia are from time to time introduced. The joint weight of the neutral salts thus obtained is then determined. In order to convert these sulphates into chlorides, the mass is moistened with water, mixed with pure chloride of ammonium, and heated in a covered cru- cible until the excess of the latter salt is expelled ; this operation is repeated until the weight is constant, when the chlorides are separated by means of bichlo- ride of platinum. Or the solution of the sulphates maybe precipitated by a solution of pure acetate of baryta, the precipitate filtered off) the filtrate evaporated to dryness, and the residue ignited. From the carbonized mass, water dissolves the alkalies as carbonates, which are con- verted into chlorides by treatment with hydrochloric acid. 2* 18 SULPHATE OF SODA-AMMONIA. 5. SULPHATE OF SODA AND AMMONIA.* NaO, S03; NH4O, S03 + 4HO. To determine the amount of soda, a weighed portion of the salt dried at 50° is gradually and carefully heated to redness in a platinum crucible, a fragment of carbonate of ammonia being held in the latter, at the end of the operation, to complete the removal of the excess of sulphuric acid. From the weight of sul- phate of soda obtained, that of the soda is calculated. The sulphuric acid is determined in another weighed portion of the salt, which is dissolved in warm water and precipitated by chloride of barium. From the weight of the sulphate of baryta, after filtering, wash- ing and igniting, the amount of sulphuric acid is cal- culated. The quantity of the ammonia may be estimated ac- cording to two different methods. a. The weighed salt is dissolved in the smallest pos- sible quantity of water, and the soluion mixed with excess of an alcoholic solution of bichloride of platinum, which precipitates the ammonia in the form of ammo- mo-chloride of platinum. When the precipitate is completely separated, it is filtered off', washed with alcohol, dried, and carefully ignited (see No. 1). From the weight of the residual platinum, that of the ammo- nia is calculated. 100 parts of platinum correspond to 26.37 of ammonia. In order to ascertain that the platinum does not contain any sulphate of soda or chloride of sodium which may have been precipitated by the alcohol, it is washed with water and again weighed. * To prepare this salt, .two equal portions of dilute sulphuric acid are taken, the one neutralized with carbonate of soda, then mixed with the other, ammonia added to neutralization, and the solution evaporated to the crystallizing point. SULPHATE OF POTASSA AND MAGNESIA. 19 5. By distilling the weighed salt with a moderately concentrated solution of soda, the ammonia is evolved, and may be combined with hydrochloric acid. This is best effected in a small flask furnished with a fun- nel-tube by which the solution of soda is introduced, and a long condensing-tube, the end of which dips into moderately-strong hydrochloric acid. The liquid is retained in ebullition until one-half has distilled over. The hydrochloric solution is carefully evapo- rated to dryness in a weighed dish, over a water-bath, and the -residue of chloride of ammonium weighed ; or it may be converted into ammonio-chloride of plati- num, which is then treated as above. After determining the soda, the ammonia, and the sulphuric acid, the quantity of the water may be ascer- tained by difference. It may also be controlled by mixing a weighed portion of the powdered salt, in a platinum crucible, with an excess of freshly-burnt lime, free from water and carbonic acid ; the mixture is covered with a layer of lime, the whole weighed, and very strongly ignited over a gas burner. The loss of weight represents the joint amount of the am- monia and water. 6. SULPHATE OF POTASSA AND MAGNESIA.* KO, S03; MgO, S03H-6HO. This salt loses all its water at 133°. The sulphuric acid is determined by precipitation by chloride of barium (see No. 3). For the estimation of the magnesia, another weighed quantity of the salt is dissolved in water, mixed with * This salt 'is easily obtained in crystals, by mixing a boiling saturated solution of 1 part of sulphate of potassa, with a saturated solution of 1^ part of sulphate of magnesia. 20 SULPHATE OF POTASSA AND MAGNESIA. chloride of ammonium, subsequently with ammonia, and the magnesia precipitated as phosphate of mag- nesia-ammonia by adding phosphate of soda. The precipitation is not complete till after the lapse of twelve hours, when the precipitate is collected on a filter and washed with a mixture of 3 parts of water and 1 part of caustic ammonia, in which it is perfectly insoluble. After drying, it is ignited, being thus converted into 2 MgO, P05 which contains 36.44 per cent, of mag- nesia. The potassa may be determined by difference. If a direct estimation be required, as is frequently the case, especially in the analysis of minerals, the salt is dissolved in water, and the sulphuric acid and mag- nesia precipitated by a hot saturated solution of hy- drate of baryta. The excess of baryta is removed from the filtered liquid by adding a mixture of ammo- nia and carbonate of ammonia, the filtrate saturated with hydrochloric acid, evaporated, the chloride of potassium feebly ignited and weighed. If both potassa and soda be present, they are sepa- rated as in No. 4. From the mixed precipitate of magnesia and sulphate of baryta, the former is dissolved by diluted sulphuric acid, and afterwards precipitated and determined as above. Another method consists in mixing the solution of the double sulphates of magnesia, and the alkalies with freshly precipitated carbonate of baryta, and passing washed carbonic acid through the mixture for a con- siderable time. The sulphate of baryta which is then produced is filtered off, the solution evaporated to dry- ness, and the mass heated nearly to redness. A mix- ture of carbonate of baryta, magnesia, and alkaline carbonate is thus obtained, from which the latter may be extracted with water, converted into chloride, and weighed. EPSOM-SALT AND GLAUBER'S SALT. 21 7. CAKBONATE OF POTASSA AND MAGNESIA.* KO, C02; 2(MgO, C02) + 9 HO." When ignited, this salt loses three-fourths of its car- bonic acid, and the whole of its water, leaving a mix- ture of carbonate of potassa and magnesia, which may be separated by water, and quantitatively determined, the potassa for this purpose being converted into chlo- ride of potassium. The magnesia should not be washed longer than is necessary, since it is not entirely insolu- ble in water. (Magnesia is more soluble in hot water, and on this account cold is preferable.) The total quantity of carbonic acid contained in the salt is determined by expelling it in an apparatus arranged for the quantitative determination of carbonic acid. The amount of water may then be inferred by difference. The joint weight of the water and carbonic acid may be determined by fusing a quantity of vitrified borax in a platinum crucible, weighing when cool, intro- ducing the salt, again weighing, and fusing over the gas flame until all the carbonic acid is evolved, and the fused borax becomes clear. The loss of weight expresses the joint amount of water and carbonic acid. 8. EPSOM-SALT AND GLAUBER'S-SALT. MgO, S03+7 HO and NaO, SO3 + 10 HO. One hundred parts of pure sulphate of magnesia give, by the method described in No. 6, 45.12 parts of phosphate of magnesia. A specimen of Epsom-salt * Obtained in crystals on mixing a solution of chloride of magne- sium with a warm saturated solution of bicarbonate of potassa. 22 PHOSPHATE OF SODA AND AMMONIA. adulterated with Glauber's salt will give a proportion- ally smaller quantity of the phosphate. Since 45.12 parts of 2 MgO, PO5 correspond to 100 parts of crys- tallized sulphate of magnesia, a specimen of the latter which yields, for example, only 40 parts of 2 MgO, PO5 would contain only 88.3 per cent, of true Epsom- salt, and 11.7 per cent, of Glauber's-salt. In order to test Epsom-salt for Glauber's-salt, the specimen is mixed with powdered charcoal, dried, and heated in a crucible to bright redness. If sulphate of soda be present, water will dissolve out of the cold mass sulphide of sodium, which, when treated with hydrochloric acid, is converted into chloride of sodium, with evolution of sulphuretted hydrogen. Or the solution of the salt to be tested may be pre- cipitated by hot saturated baryta-water, filtered, the excess of baryta precipitated from the solution by a mixture of ammonia and carbonate of ammonia, and the filtrate evaporated, when, if any Glauber's-salt have been present, carbonate of soda will be left. 9. PHOSPHATE OF SODA AND AMMONIA* NaO, NH40, HO, P05+8 HO. A weighed quantity of the salt is gradually and cautiously heated in a platinum crucible, the heat being finally raised to ignition, and continued till the salt is in a state of tranquil fusion. The ammonia and water are thus expelled, their joint amount being indicated by the loss of weight. The fused residue is NaO, P05. * Six parts of crystallized phosphate of soda are dissolved, with the aid of heat, in 2 parts of water, and in this solution 2 parts of chloride of ammonium are dissolved. Tlie filtered liquid deposits crystals of the new salt which are purified by solution in hot atu- mouiacal water and recrystallization. PHOSPHATE OF MAGNESIA AND AMMONIA. 23 The determination of the ammonia is effected as in No. 5, with another portion of the salt. In order to determine the phosphoric acicl, the salt is dissolved in water and mixed with chloride of am- monium, ammonia and sulphate of magnesia, the pre- cipitatate being treated as in No. 6. The ignited 2MgO, P05 contains 63.55 per cent, of phosphoric acid. For the direct determination of the soda, a weighed quantity of the salt is dissolved in water, and the phos- phoric acid precipitated by acetate of lead. From the filtered liquid, the excess of oxide of lead is removed by a mixture of ammonia and carbonate of ammonia, the solution heated to ebullition, filtered, evaporated to dryness and the residual acetate ignited, with access of air, until the carbonate of soda is colorless. Asa control for the determination of the phosphoric acid, the phosphate of lead may be decomposed by heating with dilute sulphuric acid, and the phosphoric acid precipitated from the filtrate by sulphate of mag- nesia, as directed above. 10. PHOSPHATE OF MAGNESIA AND AMMONIA* 2 MgO, NH40, P05+ 12 HO. By ignition the salt is converted into 2 MgO, P05. The ammonia is determined by dissolving the salt in the smallest possible quantity of hydrochloric acid, mixing the solution with bichloride of platinum and alcohol, and treating the ammonio-chloride of platinum, as in No. 5. In order to separate and determine the phosphoric * Prepared by precipitating a solution of sulphate of magnesia to which much chloride of ammonium has been added, by phos- phate of soda, and washing the precipitate with dilute ammonia. 24 PHOSPHATE OF MAGNESIA AND AMMONIA. acid and magnesia, the ignited salt is fused in a plati- num crucible, over a spirit-lamp, with 4 parts of car- bonate of potassa and soda.* The mass is digested with water, the residual magnesia washed, ignited and weighed. The alkaline solution is neutralized with acetic acid, and the phosphoric acid precipitated by acetate of lead. The precipitate is filtered off, washed, dried, detached as far as possible from the filter, which is incinerated in a porcelain crucible, in which the precipitate is then gently ignited and weighed. Since its composi- tion is variable, the quantity of the phosphoric acid cannot be calculated from it. In order to determine this acid, the precipitate is dissolved in warm dilute nitric acid, and the oxide of lead separated by sulphuric acid, alcohol being afterwards added to complete the precipitation. The sulphate of lead is filtered off, washed, ignited and weighed. From the amount of this precipitate, that of the phosphoric acid may be calculated. The phosphate of magnesia and ammonia may also be dissolved in acetic acid, the phosphoric acid pre- cipitated by acetate of lead, the excess of oxide of lead removed from the filtrate by adding a mixture of ammonia and carbonate of ammonia, heating and filter- ing. The solution, which contains acetate of magnesia, is evaporated, and the residue ignited, until the mag- nesia is perfectly white. Another method of separating phosphoric acid and magnesia consists in dissolving the ignited salt in a little hydrochloric acid, boiling the solution for some time in order to convert the phosphoric acid into the tribasic form, and mixing it, first, with solution of * Consisting of equivalent proportions of KO, C02 and NaO, CO2, or 13 parts of the former, and 10 of the latter. Also easily obtained by igniting Seignette-salt free from lime, dissolving, and evapo- rating to dryness. CHLORIDES OF POTASSIUM, SODIUM, ETC. 25 sesquichloride of iron, and afterwards, with excess of acetate of ammonia ; if the solution be now boiled for some time, all the phosphoric acid and iron are pre- cipitated, and the magnesia remains in solution. The filtered liquid is evaporated, to dryness, the residue heated till all ammoniacal salt is expelled and moistened with sulphuric acid to convert the magnesia into sul- phate. The excess of acid is expelled by heat, and the residual salt gently ignited ; from the weight of this residue. that of the magnesia, and consquently of the phosphoric acid, is calculated. 11. THE CHLORIDES OF POTASSIUM, SODIUM, AND MAGNESIUM. In the analysis of minerals which are decomposed by hydrochloric acid, there is .frequently obtained, after the separation of the other constituents, a mixture of the above-mentioned chlorides. The solution, if con- taining, as is generally the case, ammoniacal salts, ^is evaporated to dryness, and the mass gently ignited in a platinum crucible until the latter are volatilized. The magnesia and alkalies are then separated according to one of the following methods : — I. The mass is moistened with a concentrated solu- tion of carbonate of ammonia, dried and ignited, during which operation, a fragment of carbonate of ammonia is held within the partially closed crucible. This pro- cess is repeated until a constant weight is obtained. A mixture of magnesia and alkaline chlorides is left, from which the latter may be extracted by water. This method is more difficult of execution in proportion as more alkaline chlorides are present. II. The residue containing the three chlorides is mixed in a platinum crucible, with some water and a 3 26 CHLORIDES OF POTASSIUM, SODIUM, ETC. quantity of finely -powdered oxide of mercury; the mixture is digested for some time, dried, and ignited in a covered crucible, when all the chloride of magne- sium is decomposed and converted into magnesia. III. The chlorides are dissolved in a little water, and the solution boiled for a long time with freshly preci- pitated carbonate of silver, when all the chloride of magnesium is decomposed. The precipitate is filtered off) washed, and the precipitated carbonate of magnesia dissolved out with dilute hydrochloric acid. IY. The solution of the bases is mixed with some sal-ammoniac and ammonia in excess, and the mag- nesia precipitated by phosphate of ammonia (see No. 6). From the filtrate the ammonia is expelled by evapo- ration, and the excess of phosphoric acid precipitated by acetate of lead as a compound of phosphate and chloride of lead. The excess of oxide of lead is pre- cipitated by a mixture of ammonia and carbonate of ammonia; the liquid digested, and the precipitate filtered off. The alkalies are then obtained by evapo- ration. Y. The chlorides are converted into nitrates by heating with about six times their weight of nitric acid. The solution is evaporated, the salts moistened several times, digested with crystals of oxalic acid whereby all the nitric acid is decomposed. From the residual mixture of magnesia and alkaline carbonates, the latter are extracted with water. VI. The magnesia may be precipitated by sesqui- carbonate of ammonia and ammonia, and washed with the same. If potash is present in this precipitate it may be dissolved out with water after ignition. VII. Should the three bases be in form of sulphates, the process indicated in No. 4 must be adopted, or they are weighed after ignition, dissolved in a little water, the solution weighed, about one half poured ofi^ and the remainder weighed. From one portion the mag- BONE-ASH. 27 nesia is precipitated by ammonia and phosphate of soda, and from the other potassa by bichloride of pla- tinum. 12. DOLOMITE AND BITTER-SPAR. CaO, C02; MgO, C02. The mineral dried at 100° is dissolved in dilute nitric acid, the solution afterwards heated, in order to oxidize any protoxide of iron, neutralized with ammonia, heated to ebullition till it no longer smells of ammonia, and rapidly filtered from any precipitate of sesquioxide of iron. The lime is then precipitated by oxalate of am- monia. When the precipitate has subsided, after being digested for some time, it is filtered off, washed, dried and ignited ; it is then moistened with carbonate of ammonia, again dried, and gently heated. It is weighed as carbonate of lime. Or it may be moistened with concentrated sulphuric acid, the excess of acid being expelled by evaporation and subsequent ignition, and weighed as sulphate of lime. After the filtered liquid has been mixed with excess of ammonia, the magnesia is precipitated by phosphate of soda, and the precipitate treated as in No. 6. The quantity of carbonic acid contained in the min- eral may be determined by loss. It may also be ascer- tained directly by means of the apparatus arranged for the quantitative determination of carbonic acid. 13. BONE-ASH. 3CaO,PO5 with 3MgO,P05 and CaO,C02. A mass of white burnt bone is dissolved in dilute nitric acid, the solution digested for some time to expel 28 BONE-ASH. all the carbonic acid, and the phosphates of lime and magnesia precipitated by ammonia. When the pre- cipitate has separated, the solution, which contains the lime previously in combination with carbonic acid, is rapidly filtered, and the precipitate thoroughly washed with ammoniacal water. From the filtrate, the lime is precipitated by oxalate of ammonia, and the precipitate treated as in No. 12. The precipitate of phosphates of lime and magnesia is dissolved in the smallest possible quantity of hydro- chloric acid, and the lime precipitated by neutral oxa- late of potassa. The mixture is digested for some time at a gentle heat, to promote the separation of the precipitate, and the clear supernatant fluid is then cau- tiously neutralized with carbonate of potassa, in order to precipitate the oxalate of lime dissolved by the liberated oxalic acid ; as soon as it has completely separated, the precipitate is filtered off'. From the fil- trate, which contains all the phosphoric acid and mag- nesia, the latter is precipitated by ammonia as phos- phate of magnesia-ammonia, which is treated as in No. 6. From the liquid filtered from this precipitate, which must contain free ammonia, the phosphoric acid is precipitated by sulphate of magnesia. The very small quantity of fluoride of calcium con- tained in bones can only be detected qualitatively ; in the precipitate obtained by saturating the solution of bone-ash in nitric acid with ammonia. Bone-ash may also be analyzed in the following manner : The finely-powdered substance is heated for a long time, nearly to boiling, with an excess of dilute sulphuric acid, the greater part of the water is then evaporated, and the mass mixed with twice its volume of absolute alcohol, which dissolves the phosphoric acid. The mixture is filtered, and the sulphates washed with alcohol. From these the sulphate of magnesia APATITE. 29 and a part of the sulphate of lime are extracted with water, and separated as in No. 12. The sulphate of lime remaining undissolved is ignited and weighed. The phosphoric acid solution is mixed with water, the alcohol evaporated, and the phosphoric acid then pre- cipitated by sulphate of magnesia and ammonia as in No. 6. A third method, based upon the insolubility of phosphate of binoxide of tin in nitric acid, is as fol- lows : The weighed bone-ash is heated in a flask, with moderately strong nitric acid, and several times its weight of pure tin (tin-foil), the weight of which must be accurately known ; the contents of the flask are heated to ebullition, diluted with water, and the binox- ide of tin, which contains the whole of the phosphoric acid, is filtered off, washed, dried, ignited and weighed. The difference between the weight of this precipitate and that of the binoxide of tin which should be fur- nished, by the amount of metal employed, is due to phosphoric acid. The separation of the lime and mag- nesia contained in the solution is effected as in No. 12. A fourth method, applicable in general for the sepa- ration of phosphoric acid from bases, consists in dis- solving the substance to be analyzed in a small quan- tity of nitric acid, adding nitrate of silver, some car- bonate of silver, and shaking the mixture. All the phosphoric acid combines with the oxide of silver and is precipitated, while the bases remain in solution and may be separated from the excess of silver by hydro- chloric acid. • 14. APATITE. 3 (3 CaO, P05) + CaCl (or + CaF). For the determination of the chlorine, a weighed por- tion of the mineral (which need not be powdered) is 5* 30 APATITE. dissolved in dilute nitric acid,* and the chlorine pre- cipitated by nitrate of silver. In order to detect the small quantity of fluorine which is contained in some specimens of apatite, the finely powdered mineral is mixed, in a platinum cru- cible, with concentrated sulphuric acid, and the crucible covered with a glass plate coated with a thin film of wax, through which some characters have been written with a needle; the crucible is then heated with a flame so small as not to melt the wax. If fluorine be pre- sent, the characters are found etched upon the glass after the removal of the wax. The quantity of the fluorine is inferred from the loss of weight in the whole analysis. The phosphoric acid and lime may be determined by the methods described in the analysis of bone-ash. The following process may also be employed. The mineral is dissolved in nitric acid, in a dish, and so much pure mercury added that, after saturating the acid, a portion still remains undissolved. The mixture is then evaporated to perfect dryness on the water-bath. Should it still emit an odor of nitric acid, this acid must be completely expelled by adding more water, and again evaporating to dryness. The mass is treated with water, filtered through the smallest possible filter, and the residue, which contains all the phosphoric acid, well washed. The solution contains, besides the excess of the mer- cury-salt, the whole of the lime. The suboxide of mercury is precipitated by hydrochloric acid. Any protoxide of mercury which may have been formed, is precipitated from the filtrate by ammonia. If the mine- ral contain iron, or other bases precipitable by ammo- * Many compact apatites, when treated with nitric acid leave a small quantity of crystalline powder, which is cryptolite (phos- phate of protoxide of cerium). HEAVY SPAR, CELESTJNE, AND GYPSUM. 31 nia, these will remain behind on igniting this preci- pitate. From the solution, which should be filtered rapidly, and with as little exposure to air as possible, the lime is precipitated by oxalate of ammonia. The filter with the mercury-residue, which contains the phosphoric acid, is well dried, and the contents thrown into a platinum crucible in which they are mixed with carbonate of potassa and soda ; the filter is rolled up and buried in a mixture. The crucible is now heated (but not to redness) under a chimney with a good draught, until the mercury is volatilized, after which the mass may be heated to redness and fused. It is then dissolved in water, an excess of hy- drochloric acid added, and the phosphoric acid precipi- tated by ammonia and sulphate of magnesia. 15. BARITE, CELESTITE, AND GYPSUM, BaO, S03.— SrO, S03.— CaO, S03 + 2 HO. The water in gypsum is determined by ignition. The salts of strontia and lime are converted into car- bonates by action of a solution of carbonate of ammo- nia at ordinary temperature, while the sulphate of baryta remains unaltered. At a boiling heat or with carbonate of soda the decomposition is not so complete. The mixed salts must be finely powdered and well washed with cold water. Nitric acid dissolves the strontia and the lime, but does not act upon the sulphate of baryta. The latter can be decomposed by fusing with four times its weight of carbonate of potassa and soda. The mass is then treated with boiling water, the carbonate of baryta filtered off' while hot, and washed with boiling water. 32 HEAVY-SPAR, CELESTINE, AND GYPSUM. The filtered solution is carefully neutralized with hydrochloric acid, the sulphuric acid precipitated by chloride of barium, and the precipitate treated as in No. 3. The earthy carbonates are dissolved in dilute nitric acid, taking care to obtain a nearly neutral solution, which is then evaporated to perfect dryness in a flask capable of being closed. The saline mass is treated with about twice its volume of a mixture of equal volumes of ether and absolute alcohol, with which it is allowed to digest, in the closed flask, for a long time, being frequently shaken, but not heated. The mix- ture dissolves the nitrate of lime only. The mixture is filtered, and the undissolved nitrate of strontia washed with absolute alcohol in a closely covered funnel. The alcoholic solution is diluted with water, the greater part of the alcohol evaporated, and the lime precipitated, as in No. 12, by oxalate of ammonia. The nitrate of strontia is dried at 100° and weighed, or may be converted into a sulphate with sulphuric acid. To separate carbonates of baryta and strontia they are dissolved in nitric acid, the solution concentrated and the baryta precipitated by freshly -prepared hy- drofluo-silicic acid, previously mixed with an equal volume of alcohol. The silico-fluoride of barium is collected on a weighed filter, washed with weak spirit, and dried. The filtrate containing the strontia is mixed with sulphuric acid, evaporated to dryness, the sulphate of strontia ignited, and weighed. If baryta and lime only are to be separated, the solution is largely diluted, the baryta precipitated by sulphuric acid, and the lime separated from the filtrate by oxalate of ammonia, after previously neutralizing with ammonia. ALUMINA-ALUM. S3 For the separation of baryta and strontia, neutral chromate of potassa rnaj also be employed, which pre- cipitates all the baryta as chromate; the latter is washed, dried, ignited and weighed. It is necessary, however, that the solution should be perfectly neutralized and largely diluted. The strontia may afterwards be pre- cipitated by neutral carbonate of ammonia. The neutral salts of lime, mixed with a solution of arsenious acid, give with ammonia a precipitate of arsenite of lime. The salts of strontia and baryta treated in the same way do not form a precipitate. On. the other hand, the presence of strontia in a salt of lirne may be shown by a clear solution of sulphate of lime. 16. ALUMINA-ALUM. KO, S03; A1203, 3 S03 + 24 HO. A weighed quantity of the pure salt is dissolved in water, and the sulphuric acid precipitated by chloride of barium (see No. 3). From the solution filtered from the sulphate of ba- ryta, the alumina is precipitated, together with the excess of baryta which has been added, by a mixture of carbonate of ammonia and free ammonia. After gently heating for some time, the precipitate is filtered off,. the solution evaporated, and the saline mass heated till all the chloride of ammonium is volatilized. The gently-ignited residue is chloride of potassium. The precipitate containing alumina and baryta is dis- solved in dilute hydrochloric acid, and the baryta pre- cipitated by sulphuric acid. From the solution filtered from the sulphate of baryta, the alumina is precipitated by carbonate of ammonia, or better, by sulphide of ammonium, either of which effects a more complete precipitation than caustic ammonia. 3-t ALUMINA-CHROME-ALUM. The precipitated hydrate of alumina is well washed, for which purpose hot water is to be preferred, and strongly ignited in order to expel the water. The water contained in the alum is determined by loss. It may also be estimated directly by carefully exposing the salt for a very long time to a gradually increasing heat, which must finally be raised to dull redness. 17. IRON- AMMONIA- ALUM.* NH40, S03; Fe203, 3 S03 + 24 HO. At a strong red heat, this salt is entirely decom- posed, leaving pure sesquioxide of iron. The determination of ammonia is effected as in No. 5 ; that of sulphuric acid according to No. 3. In order to control the determination of the sesqui- oxide of iron, another portion of the salt is dissolved in water, and the sesquioxide precipitated by ammonia. The precipitated hydrate is washed, dried, and ignited. 18. ALUMINA-CHEOME-ALUM.t KO,S03; The sulphuric acid is precipitated by chloride of barium as in No. 3. * Powdered red or brown iron-stone is digested with concen- trated sulphuric acid ; the white sulphate thus produced is dis- solved in water, the solution mixed with sulphate of ammonia, filtered and allowed to crystallize. f Three parts of finely-powdered bichromate of potassa are mixed with 15 parts of water, and 1 part of concentrated sulphuric acid is gradually added, so that no evolution of heat may ensue; sul- phurous acid gas is then passed through the solution, which is ALUMINA CHROME-ALUM. 35 The alumina, sesquioxide of chromium, and excess of baryta are, precipitated from the filtrate by carbonate of ammonia mixed with caustic ammonia. After long standing, the precipitate is filtered oft' and thoroughly washed. The filtrate is evaporated, the residue heated to expel chloride of ammonium, and the residual chloride of potassium gently ignited in a covered crucible. The mixed precipitate is taken and washed off while wet from the filter, dissolved in dilute sulphuric acid, and the sulphate of baryta, filtered and washed. An excess of caustic potassa is added to the solution, which is then saturated with chlorine gas, and the Fig. 2. oxide of chromium forms a yellow solution of chro- mate of potassa. kept cool, so that its temperature may not rise above 4(P, until the odor of the gas begins to be perceptible. After some time, octohe- dra of pure chrome-alum are formed, which may be set aside. The mother-liquor is mixed with an equal volume of a solution of com- mon alum, saturated at 40°, when the salt in question separate! in yellowish octohedra. 36 WAVELL1TE AND PHOSPHATES OF ALUMINA. Only a small quantity of alumina is dissolved which may be precipitated by gentle digestion witl^ carbonate of ammonia. The solution of alkaline chromate filtered from the alumina is carefully mixed with excess of hydrochloric acid and some alcohol, and heated until it has a pure emerald-green color. The sesquioxide of chromium is precipitated from the hot solution by caustic ammo- nia, washed, dried, ignited, and weighed. 19. WAVELLITE AND PHOSPHATES OF ALUMINA IN GENERAL. A1203,P05 + 12HO. I. The mineral, which is only slightly soluble in hydrochloric acid, is finely pulverized and fused with caustic potassa in a silver crucible, and then dissolved in hydrochloric acid, and tartaric acid added to the solution until it gives no precipitate with excess of ammonia. Chloride of ammonium and sulphate of magnesia are then added, and the solution well closed allowed to stand for 24 hours, and the precipitated phosphate of magnesia-ammonia treated as in No. 6. It contains basic tartrate of magnesia, which after igni- tion is re-dissolved in hydrochloric acid, heated for a long time, and again precipitated by ammonia. II. The freshly-precipitated alumina is dissolved in the smallest possible quantity of caustic soda, the solu- tion diluted, heated to ebullition, and a solution of silicate of soda added as long as any precipitate of silicate of alumina is produced. Lastly, in order to precipitate the whole of the silicic acid, a concen- trated solution of sal ammoniac is added, the solution again boiled and filtered. From the filtrate, the phos- SPINEL. 37 phoric acid is precipitated by ammonia and sulphate of magnesia. The silicate of alumina is decomposed by concen- trated hydrochloric acid, the mass evaporated to dry- ness on the water-bath, the residue moistened with hydrochloric acid, the alumina-salt extracted with water, and the alumina precipitated by carbonate of ammonia. III. The weighed alumina containing phosphoric acid is dissolved in concentrated nitric acid, and the solution heated with about the same quantity (accu- rately weighed) of pure tin (tin-foil). The mixture is diluted with water, heated until boiling, and the bin- oxide of tin which has combined with the whole of the phosphoric acid is filtered off, washed, and ignited. The difference between the weight of this precipitate and that of the binoxide of tin which should have been furnished by the metal employed represents the phos- phoric acid. The alumina is then precipitated from the solution by sulphide of ammonium. Or chloride of tin is added to the solution of phos- phate of alumina, heated to boiling, and the oxide of tin and all the phosphoric acid precipitated by sul- phate of soda. If sesquioxide of iron is present, a portion of it is thrown down. The accuracy of this method is not yet determined. 20. SPINEL. (ALUMINA AND MAGNESIA IN GENERAL.) MgO,Al203. The mineral is very finely pulverized in a steel mortar separated from the iron with hydrochloric acid, and then fused with at least six times its weight of 4 38 ALUMINA AND SESQUIOXIDE OF IRON. bisulphate of potassa.* It should be kept in a state of fusion for a long time, without the disengagement of too much sulphuric acid. The mass is then dis- solved in water containing a little hydrochloric acid, chloride of ammonium added, and the alumina pre- cipitated by ammonia. In order to free it from any magnesia, the fluid is heated to boiling until no more ammonia is given oft'.f The gelatinous alumina is fil- tered, and allowed to partially dry upon the funnel when it may be completely washed. It is ignited and weighed. The magnesia is precipitated by phosphate of soda and ammonia. Many specimens of spinel con- tain a little protoxide of iron and silica. The red spinel contains sesquioxide of chromium, which may be separated from the alumina as in No. 18. 21. ALUMINA AND SESQUIOXIDE OF IRON. The mixture of the two is dissolved in hydrochloric acid, the greater part of the excess of acid evaporated, the splution mixed with an excess of pure solution of potassa and heated nearly to the boiling point. The alumina is thus dissolved, the sesquioxide of iron being left behind of a dark brown color. The solution is filtered off, acidulated with hydrochloric acid, and the alumina precipitated by sulphide of ammonium. The sesquioxide of iron, which contains some potassa, is dissolved in hydrochloric acid, re-precipitated by ammonia, and ignited. This method of separation is unsafe, and unless re- peated more than once, incomplete. It is better to heat * Prepared by heating equal parts of neutral sulphate and con- centrated sulphuric acid to a dull red heat until the the mixture flows quietly. f The same process as in the separation of alumina and lime. ALUMINA AND SESQUIOXIDE OF IRON. 39 the acid solution to ebullition, to add sulphite of soda, in order to reduce the sesquioxide of iron to the state of proto-sesquioxide, replace the solution over the lamp, boil for some time and then neutralize with car- bonate of soda, and afterwards boil with excess of caustic soda until the precipitate is black and pul- verulent. The tendency to bumping preceding the actual ebul- lition of the fluid, may be guarded against by means of a spiral coil of platinum wire placed in the liquid, or by constant agitation of the latter ; when ebullition has opce set in, there is no further need of these pre- cautions. Remove the liquid now from the gas, allow to deposit, pass the clear fluid through a filter, which must not be over-porous, boil the precipitate again with a fresh quantity of solution of soda, then wash it by decantation and. afterwards on the filter with hot water. Acidify the alkaline filtrate with hydrochloric acid, boil with some chlorate of potassa (to destroy any traces of organic matter), concentrate by evaporation, and precipitate the alumina by sulphide of ammonium or ammonia. The boiling of the precipitated oxides with the solution of soda is best effected in a large silver or platinum dish. The soda must be free from alumina and silica. Or the very dilute solution of both bases may be neutralized with carbonate of soda, mixed with sulphite of soda and heated until no sulphurous acid is given off. All the alumina is precipitated, while the iron remains in solution. The precipitate is ignited. The solution of iron is concentrated, mixed with some chlorate of potassa and hydrochloric acid and heated. After the sulphur has been filtered off the iron is precipitated by ammonia. The separation may be obtained by placing the mixed precipitate, ignited in a porcelain boat, which is placed in a tube of the same material heated to red- ness, through which a current of dry hydrogen is 40 ALUMINA AND SESQUIOXIDE OF IRON. passed, and which it is necessary to maintain until it is completely cool. Then there should be substituted in place of the current of hydrogen, a current of hy- drochloric acid gas, which transforms the iron into volatile chloride and leaves the alumina, which is weighed. A complete description of this process of separation of iron and alumina may be found in the article on silicates. The apparatus is arranged as fol- lows: L is a gas furnace upon which is placed a salt bath I. In the bottle H there is placed some fresh chloride of sodium, on which is poured concentrated hydrochloric acid. Fig. 3. Then the bottle H is placed in cold water and sul- phuric acid gradually poured upon it, taking care that the mixture does not become heated, and stopping when vapors of hydrochloric acid begin to form. It PHOSPHOEIC ACID AND SESQUIOXIDE OF IRON. 41 is sufficient to- heat this mixture to 50° or 60° to evolve a steady current of hydrochloric acid gas. The amount of sesquioxide of iron may be inferred from the loss of weight, and the result controlled by collecting the chloride of iron which passes over and weighing it. 22. PHOSPHORIC ACID AND SESQUIOXIDE OF IRON.* In order to separate phosphoric acid from sesqui- oxide of iron, the compound is ignited with at least an equal weight of carbonate of potassa and soda (No. 10), the resulting mass exhausted with water, the solution supersaturated with hydrochloric acid and then with ammonia, and the phosphoric acid precipitated by sul- phate of magnesia. The residual sesquioxide of iron retains some alkali. Or the sesquioxide of iron containing phosphoric acid is dissolved in hydrochloric acid, precipitated by ammonia, and digested with excess of sulphide of am- monium (without previous filtration), until all the sesquioxide is converted into sulphide of iron. When the liquid is no longer green, but of a pure yellow color, it is filtered off, and the phosphoric acid imme- diately precipitated by sulphate of magnesia. For the accurate quantitative separation of a small quantity of phosphoric acid from a large quantity of sesquioxide of iron, the latter is dissolved in hydro- chloric acid, and the solution heated to ebullition with sulphite of soda till its color has changed to a bright green, when all the sesquioxide of iron is converted * For analyses for practice, the phosphate of sesquioxide of iron is prepared by precipitating sesquichloride of iron with phosphate of soda. Or a mixture of phosphates may be prepared by precipi- tating a solution containing sesquichloride of iron, chloride of calcium, chloride of magnesium, and chloride of manganese. 4* 42 HEMATITE. L1MONITE. into protoxide. The solution is boiled till it no longer smells of sulphurous acid, neutralized with carbonate of soda, and, in order to produce a little sesquioxide of iron, mixed with a very little chlorine- water, the quantity of which must be regulated according to the amount of phosphoric acid which is present. The solution must now be mixed with an excess of acetate of soda, when phosphate of sesquioxide of iron sepa- rates as a white precipitate. Chlorine- water is then added, drop by drop, until the liquid has assumed a reddish color, when it is boiled, so that the precipitate may collect, and be filtered. From this precipitate the phosphoric acid is separated by sulphide of ammo- nium, as directed above. Or it may be dissolved in hydrochloric acid, boiled with sulphite of soda, and afterwards with excess of caustic soda, till the precipitate is converted into black proto-sesquioxide of iron, which is filtered off. The solution is acidified, and the phosphoric acid precipi- tated as above. 23. HEMATITE, Fe203, AND LTMONITE, Fe2O3, 3 HO. For the determination of the water, weighed frag- ments of the ore are heated to redness, for a long time, in a platinum crucible. If the mineral decrepitates, it must first be finely powdered. In order to determine the oxygen, the fragments of ignited limonite or of hematite are heated to redness in a weighed bulb-tube of very infusible glass (the bulb being as small as possible), through which a stream of dry hydrogen, free from arsenic, is transmit- ted as long as any water is formed. In order to purify hydrogen it is passed through the U tubes containing pumice or fragments of porcelain HEMATITE. LIMONITK. 43 dipped in a solution of acetate of lead, sulphate of sil- ver, and caustic potassa; the first absorbs the sulphuric Fig. 4. • acid, the second absorbs the combinations of hydrogen with phosphorus and arsenic, and the last thecarburet- Fig. 5. 44: ' MAGNETITE. ted hydrogen. The reduction must be effected at the highest temperature of the gas-lamp, for otherwise the reduced iron, even when cool, may reoxidize and sometimes inflame in the air. It is safer to reduce the oxide in a small porcelain boat, placed in a tube of porcelain, which is heated by a charcoal fire, or over the gas furnace. The reduced iron is heated in a stream of hydro- chloric acid gas. Silicic acid, which is often contained in limonite, is then left undissolved, and may be weighed. 24. MAGNETITE.* FeO, Fe2O3. To determine the amount of oxygen which is com- bined with the iron, the proto-sesquioxide is reduced by hydrogen, as in No. 23. " If the substance contain only proto-sesquioxide of iron, the whole of the iron may be determined by dis- solving in hydrochloric acid, heating with some chlo- rate of potassa, to convert all the protochloride into sesquichloride, and adding ammonia to precipitate the sesquioxide of iron, which is washed, dried, ignited, and weighed. If other constituents be present the total amount of iron may be determined as follows: The substance is dissolved in an excess of hydrochloric acid, the proto- chloride converted into sesquichloride by addition of chlorate of potassa, and all free chlorine expelled by- boiling. The solution is then diluted with water until the flask is more than half-full; a weighed strip of bright sheet-copper is placed in the solution, the flask closed by a cork furnished with a narrow glass tube, * Forge-scales have a similar composition. MAGNETITE. 45 and the liquid heated to ebullition. It is 'retained at this temperature until the dark-brown color originally observed has changed to a pale yellowish-green. The whole of the iron is now contained in the solution as protochloride, in consequence of the formation of sub- chloride of copper. The orifice of the little tube is closed air-tight, and the solution allowed to cool some- what. The flask is then filled with hot water, the liquid poured off' from the undissolved copper, which is to be washed, first with dilute hydrochloric acid, then re- peatedly with water, dried, and weighed. The atomic weight of copper is to that of iron as the quantity of copper dissolved is to that of the iron sought. In order to determine directly the amount of pro- toxide and sesquioxide of iron present in. a substance, it must be dissolved in hydrochloric acid. The follow- ing is the method adopted: The compound is dissolved in an excess of concentrated hydrochloric acid, in a flask filled with carbonic acid, and afterwards closed; the flask is then nearly filled up with water, previously boiled, and a weighed strip of copper introduced; the closed flask is placed in water, which must be gradually heated to boiling, the subsequent process being con- ducted and the result calculated as directed above. Or the weighed substance is placed in a flask closed with a cork, and furnished with tubes for ingress and egress, and with a funnel-tube passing to the bottom of the flask, which is to be filled with carbonic acid. Hydrochloric acid is then added through the funnel- tube, and the solution assisted by heat, whilst carbonic acid is allowed to stream through the apparatus. The solution is afterwards diluted, through the funnel-tube, with boiled water, and a milky mixture of carbonate of baryta with water gradually added; this precipitates the whole of the susquioxide of iron, while the protox- ide remains in solution. When the supernatant liquid has become clear, it is decanted through the egress- 46 SIDERITE. tube, the precipitate again mixed with water, and after the clear liquid has been again decanted, quickly thrown upon a filter, and rapidly washed, air being excluded, with water which has been previously boiled and al- lowed to cool. The iron precipitate is dissolved in dilute hydro- chloric acid, the baryta separated by sulphuric acid, and the sesquioxide of iron precipitated by ammonia. The solution, which contains the protoxide of iron, is mixed with hydrochloric acid and chlorate of potas- sa, and concentrated by evaporation; the baryta is then precipitated by sulphuric acid, and afterwards the ses- quioxide of iron by ammonia. 25. SIDERITE. FeO, CO,,, frequentlv containing MnO, CO^— CaO, CO2, "and MgO, CO2. I. The best method of analysis, which is especially applicable where but little manganese is present, is the following: A weighed portion of the powdered ore, previously dried, is dissolved in hydrochloric acid, with the aid of heat, nitrate or chlorate of potassa be- ing added from time to time, so that the whole of the protoxide of iron is sure to be converted into sesqui- chloride. The solution, which must still be acid, so that chloride of ammonium may be formed, is diluted, and gradually neutralized with dilute ammonia, until it has acquired a dark brown-red color, and a small quantity of hydrated sesquioxide of iron is precipi- tated. The whole of the sesquioxide of iron is then separated by neutral succinate of ammonia, while prot- oxide of manganese, lime, and magnesia remain in solution. The precipitated succinate of sesquioxide of iron is rapidly filtered off, washed with cold water, SIDERITE. 47 dried, and gradually heated to redness in a porcelain crucible, with free access of air; till it is converted into pure sesquioxide of iron. The filtrate is feebly acidulated with hydrochloric acid, evaporated to dryness, and heated till all ammo- niacal salts are expelled. The residue is then dissolved in a small quantity of water, with addition of hydrochloric acid, the solution saturated with chlorine, and the manganese precipitated as hydrated sesquioxide by addition of ammonia. The liquid is rapidly filtered off, so that no carbonate of lime may be precipitated, and the manganese-precipi- tate washed, dried, and ignited, when it is converted into brown proto- sesquioxide. The lime and magnesia in the filtrate are separated as in No. 12. Or the manganese may be precipitated by sulphide of ammonium, the sulphide of manganese rapidly fil- tered off, and dissolved in hydrochloric acid. When all the sulphuretted hydrogen has been expelled by evaporation, the solution is heated with carbonate of soda, when the manganese is precipitated as carbonate, which, after ignition, leaves the brown proto-sesqui- oxide. From the solution filtered from the sulphide of man- ganese, the lime and magnesia are precipitated as in No. 12. II. The acid solution is largely diluted with water, and carbonate of soda gradually added (drop by drop, when the solution is neutral), with constant stirring, until all the sesquioxide of iron is precipitated. The other bases remain dissolved in the free carbonic acid. The manganese is then best precipitated by hypochlo- rite of soda, in the cold. III. When a larger quantity of manganese is present, the solution, which must contain the iron entirely in the form of sesquichloride, and must not be too acid, 48 SIDERITE. is gradually mixed with carbonate of baryta, which precipitates the sesquioxide of iron only. When a slight excess of carbonate of baryta has been added, and the solution well stirred, it is filtered. The washed precipitate is dissolved in dilute hydrochloric acid, the baryta precipitated by sulphuric acid, and the sesqui- oxide of iron by ammonia. From the solution which contains the other three bases, the dissolved baryta is first precipitated by sul- phuric acid, and the solution treated as in No. 12. IV. The diluted solution, obtained as in I, is neu- tralized with carbonate of soda till it has a dark brown- red color, mixed with a saturated solution of acetate of soda, and chlorine gas passed into it which precipitates the manganese, or it is heated to ebullition, when the whole of the sesquioxide of iron is precipitated. The filtrate is neutralized with carbonate of soda, mixed with hypochlorite of soda (containing bicarbo- nate of soda), and allowed to stand in a closed vessel for twenty-four hours, when the manganese is precipi- tated as hydrated sesquioxide, which is ignited and weighed as proto-sesquioxide. From the filtered liquid the lime and magnesia are separated as above. V. The solution of oxide of iron is precipitated by ammonia, the liquid boiled as long as ammonia is given off, and the oxide of iron filtered off, which is now free from lime, magnesia, and manganese. It may be fil- tered with free access of air, for the fluid contains no free ammonia. The solution is concentrated by evapo- ration and the three bases precipitated by an excess of carbonate of potassa, and boiled until ammonia ceases to be disengaged. It is then filtered, the precipitate dissolved in nitric acid, evaporated to dry ness, and the saline mass care- fully raised to a dull red heat. The lime and mag- BOG IRON ORE. 49 nesia may be separated, by very dilute nitric acid from the oxide of manganese, which is insoluble in the acid. 26. BOG IRON-ORE. Fe203, 3 HO, with MnO, A1203, CaO, MgO, Si03, P05, As05. If the amount of iron only is to be determined, the process with copper may be employed, as in the case of magnetic iron; or the ore may be subjected to the dry assay. The complete analysis is effected in the following manner: — The mineral, dried at 100°, is ignited, and the water determined. Another portion, which has not been ignited, is coarsely powdered, and dissolved in hydrochloric acid ; the solution is evaporated to perfect dryness on the water-bath, the mass dissolved in warm dilute hydro- chloric acid, and the sand and silicic acid removed by filtration. The latter may, after ignition and weigh- ing, be separated from the sand by boiling with carbo- nate of soda. The hydrochloric solution is boiled with an alkaline sulphite, until it no longer smells of sulphurous acid, to reduce the sesquichloride of iron to protochloride, and the arsenic acid to arsenious acid, which is then pre- cipitated by sulphuretted hydrogen, as tersulphide of arsenic; sometimes mixed with a little sulphide of copper. The solution is boiled till the sulphuretted hydrogen is completely expelled, precipitated by carbonate of soda, mixed with an excess of caustic soda, and boiled until the precipitate becomes pulverulent. The solution is filtered off. It contains all the alu- 5 50 WET ASSAY OF IKON. mina and part of the phosphoric acid, which are sepa- rated as in No. 19. The precipitate, consisting of proto-sesquioxide of iron, carbonate of protoxide of manganese, carbonate and phosphate of lime and magnesia, is dissolved in hot nitric acid; the solution is neutralized, as far as possible, with carbonate of soda, mixed with acetate of soda, and boiled, when all the phosphoric acid and sesquioxide of iron are precipitated. In order to sepa- rate these, the precipitate is treated as in No. 22. The filtrate contains the protoxide of manganese, lime, and magnesia, which are separated as in No. 25. 27. WET ASSAY OF IRON. (Volumetric Method.) The process for determining in the moist way with great accuracy, and without a complete analysis, the amount of iron contained in an ore, consists in ascer- taining the number of measures of a solution of per- manganate of potassa of known strength which may be decolorized by the solution of protoxide of iron obtained from a given quantity of the ore.* One equiv.= 1/980 grms. of crystallized perman- r * To prepare the permanganate of potassa, 10 parts of very finely powdered pyrolusite are mixed with 7 parts of chlorate of potassa, the mixture saturated with a very concentrated solution of 10 parts of hydrate of potassa and the wet mass gradually heated in an earthen crucible to dull redness, so that it cinders together, but does not fuse. When cool, it is powdered, treated, in a flask, with a considerable quantity of hot water, and washed carbonic acid gas passed into it until the color of the solution has changed to a purple-red, and the excess of potassa is converted into the carbo- nate. It is then allowed to stand until the solution becomes clear, which is poured off from the precipitate and evaporated to the point of crystallization. The salt is then purified by recrystalli- zation. WET ASSAY OF IRON". 51 ganate of potassa converts the protoxide of iron from 10 equivs. = 3'500 grms. of pure iron into sesquioxide. So that if 19-80 grms. of the salt be dissolved in 1 litre (=1000 grms. or 1000 cub. cent.) of water ; 100 cub. cent, of this solution will correspond to 3'50 grms. of iron. It must be kept in a well-stoppered bottle. An equivalent quantity (say 3*5 grms., or half that amount) of the ore to be tested is dissolved in concen- trated hydrochloric acid, in a capacious flask, by the aid of heat. If the insoluble residue of foreign mat- ters, such as clay, silica, &c., be not very considerable, it is unnecessary to filter the solution. The iron must now be entirely reduced to the state of protoxide, either by mixing the solution with several times its volume of a saturated solution of sulphurous acid, and boiling so long as any trace of that gas is perceptible ; or, bet- ter, by allowing a piece of zinc, free from iron, to remain in the liquid until its color is changed to a pale green. It is then decanted from the zinc, the latter thoroughly rinsed, the solution diluted with the washing- Fig. 6. Fig. 7. Fig. 8. Fig. 9. Fig. 10. The figures 6, 7, 8, 9, 10 represent the burette, the pipette, and the graduated vessels used in volumetric analysis. water, and mixed with some more hydrochloric acid ; the solution of permanganate of potassa is then drop- ped in from a burette (see Alkalimetry), until the 52 IRON ASSAY. yellow color which the solution then acquires is changed to a clear red by adding another drop of the perman- ganate. The number of cubic centimetres of the manganese-solution which have been employed, at once indicates the percentage of iron in the ore. Instead of the"crystallized permanganate of potassa, the crude solution originally obtained in the prepa- ration of that salt may be employed, provided it be first graduated — that is, quantitatively tested as to its oxidizing power. For this purpose, 3'5 grms. (or half that quantity, T75 grms.) of pure iron-wire are dis- solved in a capacious flask by concentrated hydro- chloric acid, with the aid of heat. The solution is diluted with several times its volume of cold water, and the solution of permanganate dropped into it, as directed above. When the quantity of solution em- ployed has been read off, the whole is diluted with so much water, that 100 cub. cents, may correspond to 3'5 grms. of iron. It must be kept in a well-stoppered bottle. 28. IRON ASSAY. The weighed iron-ore, in the state of fine powder, roasted or not, as the case may be, is mixed with dried borax, and the mixture exposed for an hour, in a cov- ered crucible lined with charcoal, to the most intense heat of a wind-furnace with a good draught; the quan- tity of borax varies according to the nature of the iron-ore. The greater the quantity of extraneous mat- ter which is present, the more borax it requires. For 10 grms. of iron-ore, 3 grms. of borax may be taken as the minimum, 10 grms. as the maximum. In a well conducted assay, all the iron is found reduced to a sin- gle well-fused button. If the iron ore contained phos- phoric acid the crude iron will contain phosphorus. CHALCOPYRITE. 53 29. SULPHATE OF COPPER. (Blue Vitriol.) CuO,S03 For analysis, the salt is purified by recrystallization. To determine the water, a weighed quantity of the dry salt, in the state of fine powder, is heated to about 200°, until it has become perfectly white, and has ceased to lose weight. It is then dissolved in water, and the sulphuric acid precipitated by chloride of barium, as directed in No. 3. For the determination of copper, another weighed portion of the salt is dissolved in from 50 to 100 times its weight of water, in a dish or a wide-mouthed flask; the solution is heated until boiling, and the oxide of copper precipitated by caustic potassa, which should not be added in too large excess. The brownish-black precipitate is filtered off, washed with hot water, dried, and weighed. To determine the amount of oxygen in the oxide of copper, a freshly-ignited portion is introduced into a weighed bulb-tube, and its weight carefully ascertained ; a stream of dry hydrogen, free from arsenic, is then passed through the tube, the bulb of which is heated to redness with a large flame. When no more aqueous vapor is perceptible, and the oxide is completely re- duced to the metallic state, it is allowed to cool in the stream of gas, and weighed as soon as the hydrogen in the tube has been replaced by atmospheric air. 30. CHALCOPYRITE. Cu2S, Fe2S8. The powdered mineral is introduced into a flask, placed obliquely, and gradually mixed with concen- 5* 54 CHALCOPYRITE. trated nitric acid in small portions at a time ; the con- tents of the flask are then heated until either the whole is dissolved, or the metals have passed into solution together with a portion of the sulphur, and the un- oxidized sulphur has separated in the form of a yellow powder, or in fused drops of a clear yellow color. The solution is diluted with water, and decanted from any undissolved sulphur, which is well washed, dried in a porcelain crucible, at a gentle heat, and weighed. It is then burnt in order to ascertain whether it contains any metals or quartz, &c. Should the sulphur "be separated in a pulverulent state, it must be collected on a weighed filter, washed, and dried at a very gentle heat. From the filtered solution, that portion of the sul- phur which has been converted into sulphuric acid is precipitated by chloride of barium, and the sulphate of baryta treated as in No. 3. Protracted washing with hot water is necessary, since the precipitate has carried down some nitrate of baryta. In order to avoid this, the mineral may be dissolved in concentrated hydrochloric acid, with gradual addi- tion of nitric acid, or chlorate of potassa. The excess of baryta having been removed from the liquid filtered from the sulphate of baryta by means of sulphuric acid, a slow stream of sulphuretted hydro- gen is passed through the filtrate, until the odor of the gas is distinctly perceptible. The precipitated sulphide of copper is thrown, as rapidly as possible, upon a dried and weighed filter, and well washed with water containing sulphuretted hydrogen. It is then dried in the funnel at 200°, weighed, a portion of it introduced into a weighed bulb-tube, which is afterwards again weighed, and heated in a stream of hydrogen until it no longer loses any sul- phur. It is thus converted into Cu2S, which contains the same amount of copper as the protoxide. The SPHALERITE. 55 weight obtained is calculated upon the whole quantity of sulphide of copper. Or the filter with its contents may be allowed to dry in the funnel, the precipitate detached, and thrown into a beaker ; the filter is then completely incinerated, the ash added to the sulphide of copper, and the latter oxidized with agua-regia till the sulphur separates of a pure yellow color. From the filtered solution, the protoxide of copper, as in No. 29, is precipitated at a boiling heat by caustic potassa, ignited and weighed. The solution filtered from the sulphide of copper, containing the iron in the form of protoxide, is heated nearly to boiling, in a flask, concentrated if necessary by evaporation, and treated at the same time with chlorate of potassa in small portions, until all the prot- oxide of iron is converted into sexquioxide, which is then precipitated by ammonia, washed, dried, and ignited. Notwithstanding the solubility of oxide of copper in caustic ammonia, this reagent will not effect its com- plete separation from sesquioxide of iron, since the latter carries down with it a considerable quantity ~of oxide of copper which cannot be extracted by ammonia. 31. SPHALERITE, OR BLENDE. ZnS. The solution is effected just as in the case of chalco- pyrite. -The mineral must be very finely powdered, and very concentrated acid must be employed. After the sulphuric acid which is produced has been precipitated by chloride of barium, and the excess of baryta has been removed, the solution is saturated with sulphuretted hydrogen, in order to precipitate any cop- per and cadmium which often occur in small quantities 56 SPHALERITE. in this mineral. The precipitatate, after being filtered off and washed, is treated as in No. 36. The first filtrate, which contains the zinc and gene- rally a little iron, is heated to ebullition, and mixed, first with some hypochlorite of soda to peroxidize the iron, then with excess of ammonia, until all the oxide of zinc is redissolved, and the sesquioxide of iron pre- cipitated ; the latter is then washed and ignited. It cannot be obtained by this method perfectly free from oxide of zinc. From the filtrate, the zinc is precipitated by sulphide of ammonium. The precipitate should not be filtered off until it has separated from the liquid; it is washed with water containing a little sulphide of ammonium, and digested (together with the filter), while yet moist, with concentrated hydrochloric acid, the solution fil- tered off) and the oxide of zinc precipitated, at the boiling-point, by carbonate of soda. The precipitate is washed, dried, ignited, and weighed as pure oxide of zinc. Or it may be dried as sulphide of zinc, removed from the filter as much as possible, which is burned, and the ashes added to the sulphide, mixed with a little sulphur, placed in a weighed bulb tube, and ignited in a current of hydrogen, and then weighed as sulphide of zinc. Sesquioxide of iron may be more completely sepa- rated from oxide of zinc by means of succinate of am- monia, as described in No. 25, or by carbonate of baryta (No. 25, III.) If, as has been proposed, the solution were mixed with acetate of soda, so as to convert the iron and zinc into acetates, and treated with sulphuretted hydrogen, not only zinc, but iron also would be precipitated. SMITIISOXITE. 57 32. SMITHSON1TE. ZnO, C02. This mineral generally contains small quantities of protoxides of iron, manganese, lead, and cadmium, together with lime, magnesia, and silicic acid. It is dissolved in hydrochloric acid, the solution evaporated to dry ness, the mass digested with concen- trated hydrochloric acid, diluted, heated, and the silicic acid filtered off. The solution, which must be acid, is saturated with sulphuretted hydrogen, which precipitates the lead and cadmium. This precipitate is oxidized with concentrated nitric acid, a little sulphuric acid being also added, evapo- rated to dryness, and the sulphate of cadmium sepa- rated from the sulphate of lead by water. (See Lead and Bismuth.) The filtrate is boiled, to expel the sulphuretted hy- drogen, and treated with chlorate of potassa to perox- idize the iron. From the solution, which must still contain free chlorine, the sesquioxides of iron and manganese are precipitated by excess of caustic am- rnonia, and separated as in No. 25. The zinc is precipitated from the filtered solution, as sulphide, by addition of sulphide of ammonium, and the precipitate treated as in No. 31. The solution is rapidly filtered off) with as little exposure to air as possible, and the lime precipitated by oxalate of am- rnonia ; the magnesia is afterwards separated by phos- phate of soda. IF a specimen of this mineral consist of carbonate and silicate of zinc, their relative quantities may be approximately determined by igniting the finely-pow- dered mineral, and digesting it with a mixture of car- bonate of ammonia and free ammonia, which dissolves 58 BRASS. the oxide of zinc previously in combination with car- bonic acid, leaving the silicate untouched. 33. BRASS. The alloy is dissolved in hydrochloric acid with gradual addition of nitric acid, the solution diluted, and the copper precipitated by sulphuretted hydrogen. (See No. 30.) The excess of sulphuretted hydrogen is expelled from the filtrate by boiling, and the oxide of zinc pre- cipitated from the hot solution by carbonate of soda. (See No. 31.) Oxide of zinc cannot be entirely separated from oxide of copper by even a very large excess of caustic potassa. Too little zinc is usually obtained by the above pro- cess, because a portion is carried down with the sul- phide of copper. The separation is more completely effected by neutralizing the diluted solution of the alloy with ammonia, and digesting with a slight excess of solid hydrate of potassa until it has lost its color and ammoniacal odor. The oxide of copper is then filtered off, and washed with hot water. From the alkaline solution, the zinc is precipitated by sulphide of ammonium, or boiling with carbonate of soda. Another accurate method is the following: The so- lution of both metals is saturated with sulphurous acid and the copper precipitated as white subsulphocyanide by sulphocyanide of potassium. After it has digested for some time, the subsulphocyanide is filtered, a little sulphur added and ignited in hydrogen gas,* when it * The precipitate with filter ash should be placed in a porcelain crucible, and strongly ignited by a stream of hydrogen, by means of the gas blowpipe. OXIDES OF MANGANESE, IRON> AND ZINC. 59 is converted into Cu2S. The oxide of zinc is heated and precipitated with carbonate of soda. This method may be used also for the separation of iron and copper. The brass sometimes contains traces of tin. It is then dissolved in hot nitric acid, which leaves the bin- oxide of tin (containing a little copper) untouched. In order to detect a small quantity of lead which frequently occurs in brass, the sulphide of copper pre- cipitated by sulphuretted hydrogen is oxidized with fuming nitric acid, the mass dried, and treated with water, which leaves thq sulphate of lead undissolved. Should this contain sulphur, it must be burnt off. Or the brass may be dissolved in nitric acid, a little sulphuric acid added, the solution evaporated to dry- ness, and the mass treated with water. If the brass be placed in a little porcelain boat, and heated to redness in a porcelain tube through which a rapid stream of hydrogen is passed, all the zinc rnay be volatilized. 34. OXIDES OF MANGANESE, IRON, AND ZINC. The solution, which must contain the iron in the form of sesquioxide, is mixed with carbonate of soda until a permanent precipitate begins to appear; it is then boiled with acetate of soda, when all the sesqui- oxide of iron is precipitated. The filtrate is mixed with acetic acid, and the zinc precipitated by sulphuretted hydrogen. The manganese may be precipitated, after neutrali- zation, with an alkaline hypochlorite, or by boiling with an alkaline carbonate. 60 CADMIUM AND ZINC. 35. CADMIUM AND ZINC. The alloy of the two metals is dissolved in hydro- chloric acid, the solution, which must be decidedly acid, is largely diluted, and saturated with a slow stream of sulphuretted hydrogen, which precipitates all the cadmium in the form of a yellow sulphide. The latter is thrown upon a weighed filter, and dried at 100° till of constant weight. It is more accurate to dissolve the sulphide of cad- mium in hydrochloric or nitric acid, and to precipitate the oxide of cadmium from the solution, as white car- bonate, by means of carbonate of soda. The precipi- tate is washed, dried and ignited, when it is converted into the brown oxide. Previously to the incineration of the filter, the precipitate should be detached, as far as possible. The filtrate is boiled to expel the sulphuretted hy- drogen, and the zinc precipitated from the hot liquid by carbonate of soda. Another method of separation consists in decom- posing the solution of the two metals by considerable tartaric acid, and then adding caustic soda to distinctly alkaline reaction, dilute with considerable water, and boil for some hours. The cadmium is alone precipi- tated. The zinc may be precipitated from the filtered solution by sulphide of ammonium. 36. CADMIUM AND COPPER. 'Both metals may be precipitated from a weak acid solution by sulphuretted hydrogen, the washed pre- cipitate washed off from the filter, boiled with dilute sulphuric acid, when all the cadmium will be dissolved. Or the washed precipitate of both metals, with the GALENITE. 61 filter, is dissolved in hydrochloric acid with a little chlorate of potash, the solution saturated with potassa, and then hydrocyanic acid added until the precipitate is again dissolved. From this solution of the double cyanides the cadmium may be precipitated by sulphu- retted hydrogen, and the copper will remain. The sul- phide of cadmium is treated as in No. 35. The solu- tion of copper is boiled with aqua regia, and while hot the copper precipitated by caustic potassa. The copper maybe separated from cadmium as from zinc, by sulphocyanide of potassium, as in No. 33. 37. GALENITE. PbS. The finely-powdered mineral, placed in a capacious dish, is gradually moistened with fuming nitric acid until it is entirely converted into white sulphate of lead ; a few drops of sulphuric acid are added, to insure complete conversion, the mass ignited and weighed. If the residue, previously to ignition, be treated with water, and filtered, only traces of lead are found in the solution. If the galena contain copper, iron, or silver, they will be detected in the solution, the first two by ammonia, and the silver by hydrochloric acid. If the galena be oxidized with more diluted nitric acid, the residue consists of a mixture of sulphate of lead and sulphur, while the solution contains nitrate of lead, from which the lead may be precipitated by sulphuric acid, or, more completely, by oxalate of am- monia, after neutralization. By igniting the dried residue, the sulphur is volatilized, and sulphate of lead remains. When boiled with a solution of carbonate of soda, 6 62 WHITE LEAD. the sulphate of lead is converted into carbonate, which, after washing, is completely dissolved by nitric acid. Sulphate of lead is dissolved to a great extent by a mixture of tartrate of ammonia and free ammonia. From this solution it may be completely precipitated by sulphide of ammonium as black sulphide of lead, or by chromate of potassa, in the form of yellow chro- mate of lead. The sulphate of lead may be reduced to the metallic state by fusion with four times its weight of cyanide of potassium. 38. WHITE LEAD. 2(PbQ, OO2)-fPbO,HO frequently mixed with BaO, SO.,,— CaO, SO3;— CaO, CQ2, or PbO, S03. Pure white lead is perfectly soluble in dilute nitric acid. The oxide of lead may be determined by igni- tion, after drying at 100°. In order to estimate the water, a specimen, whjch has been dried at 100°, is ignited in a tube to which a weighed chloride-of-calcium tube is attached. The carbonic acid, which is expelled at the same time, is determined by loss. White lead sometimes contains a small quantity of basic acetate of lead, indicated by the odor of acetone which is per- ceived when the specimen is ignited. White lead adulterated with chalk is likewise dis- solved, with exception of traces of impurities, by nitric acid. From the diluted solution, the lead is precipi- tated by sulphuretted hydrogen, the sulphide of lead collected upon a weighed filter, washed, dried at 100°, and weighed. From the solution, after neutralizing with ammonia, the lime is precipitated by oxalate of ammonia. If barite be present in the specimen, it is left be- PYROMORPHITE. 63 hind on treatment with nitric acid. After washing and igniting, it is weighed and analyzed as in No. 15. Gypsum would also be in great measure left behind on dissolving in nitric acid. It may, however, be en- tirely dissolved and separated from any barite pre- sent at the same time, by boiling with a large quan- tity of dilute nitric acid. The amount of gypsum present may be inferred from that of the sulphate of baryta obtained by precipitating the solution with chloride of barium. Sulphate of lead would also be left undissolved by dilute nitric apid. After washing, it becomes black when treated with sulphide of ammonium ; it is soluble in tartrate of ammonia mixed with free ammonia. In a mixture of sulphate of lead and sulphate of baryta, the former may be converted, by digestion with sul- phide of ammonium, into sulphide of lead, which can be transformed into chloride by treatment with con- centrated hydrochloric acid, and may then be dissolved out by water. 39. PYROMORPBITB. 3(3PbO,P05)-r-PbCl* In many varieties, the chloride of lead is replaced by chloride of calcium, in others, a part of the phos- phoric acid is replaced by arsenic acid. The green varieties contain traces of sesquioxide of iron and ses- quioxide of chromium or chromic acid. Those specimens which are free from lime are finely * May be artificially obtained in crystals, by fusing in a porce- lain crucible an intimate mixture of 1 part of fused phosphate of soda, and 7 parts of chloride of lead ; the mass is very gradually heated to about the fusing-pointof the latter ; it is then allowed to cool, and the liquid portion decanted from the crystals. 64 PYROMORPHITE. powdered, and dissolved in caustic potassa. The lead is precipitated from the solution by sulphide of ammo- nium, filtered, dried, and as much removed from the filter as possible. The filter is then burned and the ashes added to the precipitate, which is then mixed with a little sulphur, strongly heated in dry hydrogen gas, and then weighed as sulphide of lead. The filtered solution is acidified with hydrochloric acid, which precipitates any sulphide of arsenic, to be treated as directed in the article upon copper-nickel. (No. 65.) The liquid filtered from the sulphide of arsenic is concentrated by evaporation, supersaturated with am- monia, and the phosphoric acid precipitated by sulphate of magnesia. (See No. 9.) The chlorine is determined in another portion, by dissolving in nitric acid, and precipitating by nitrate of silver. For the determination of lime, the mineral is dis- solved in nitric acid, and the lead precipitated from the diluted solution by sulphuretted hydrogen. The solution filtered from the,sulphide of lead is neutralized with ammonia, and the lime precipitated by oxalateof ammonia. The filtrate is concentrated by evaporation, mixed with ammonia, and the phosphoric acid preci- pitated by sulphate of magnesia. Those specimens which are free from lime, but which contain arsenic acid, maybe analyzed in the following manner. The mineral, in a state of very fine powder, is digested with moderately dilute sulphuric acid, the greater part of the water evaporated, the mass mixed with alcohol, and the sulphate of lead thrown upon a filter and washed with spirit of wine. The filtrate is evaporated to expel -the alcohol, arid a stream of sul- phuretted hydrogen passed through it, while it is heated to about 50°. It is afterwards allowed to cool while the gas is still passing, and, when saturated with SILVER AND LEAD. 65 sulphuretted hydrogen, set aside in a closed vessel for twenty-four hours, after which the precipitated penta* sulphide of arsenic is filtered off. The filtered solution is treated with ammonia which precipitates the iron as sulphide, occasionally mixed with a small quantity of sesquioxide of chromium. The phosphoric acid is precipitated from the filtrate, after concentration, by sulphate of magnesia and ammonia. In order to separate the sesquioxide of chromium, the mineral is digested with a mixture of concentrated hydrochloric acid and alcohol, the solution filtered) evaporated to expel the alcohol, and the sesquioxide of chromium precipitated from the hot solution by am*- monia. It still contains a little phosphoric acid* 40. SILVER AND LEAD, I. By cupellation. II. The solution of the two metals in nitric acid is diluted with much water, heated nearly to the boiling- point, and the silver precipitated as chloride of silver by hydrochloric acid. (See No. 1.) The filtered solution is allowed to cool, the greater part of the acid neutralized with ammonia, and the lead precipitated by sulphuretted hydrogen. (See No. 39.) III. The diluted nitric solution of the two metals is mixed with dilute hydrocyanic acid, which precipitates the silver as cyanide. When this has accumulated, leaving the solution clear, it is collected upon a filter which has been dried at 120°, washed, dried at that temperature, and weighed. From the filtrate, after neutralizing the larger excess of acid, the lead may be precipitated by sulphuretted 66 SILVER AND COPPER. hydrogen, or if the solution be concentrated by evapo- ration, by sulphuric acid in the presence of alcohol. IV. Another method consists in precipitating the solution of the two rnetals by a slight excess of car- bonate of soda, and digesting the precipitate with cyanide of potassium, which dissolves the silver in the form of a double cyanide, leaving the carbonate of lead untouched. Since, however, itcontains some alkali, it must be dissolved in nitric acid, and precipitated by sulphuretted hydrogen or sulphuric acid. From the solution containing the silver, the latter may be preci- pitated as cyanide by nitric acid. V. The solution of the lead and silver in nitric acid is neutralized with an akali, mixed with an akaline formate, and heated to boiling, when all the silver is precipitated in the metallic state. 41. SILVER AND COPPER. (Silver-coin.) The alloy is dissolved in moderately strong nitric acid, the silver precipitated from the hot solution by dilute hydrochloric acid with violent agitation, and the chloride of silver treated as in No. 1. The oxide of copper is precipitated from the filtrate by caustic potassa at a boiling heat, washed, dried, ignited and weighed, the filter being completely incin- erated apart from the precipitate. If the alloy contain gold also, it is left behind by the nitric acid as a brown powder. If it be present in very small quantities — as, for example, in all old silver coins — the small insoluble residue is filtered off; thor- oughly washed, the filter incinerated, and the ash fused before the blowpipe with carbonate of soda, when the gold appears in small globules. SILVER ASSAY. 67 When frequent quantitative determinations of silver are made, as in mints, the test is made either by cupel- lation, which consists in fusing the weighed alloy with several times its weight of pure lead in a small bone earth cupel in a current of air, when the lead and cop- per are oxidized and absorbed by the cupel, while the pure silver remains as a fused button. Or, more ac- curately, by volumetric analysis. In order to prepare pure silver, it is precipitated from the solution by hydrochloric acid or chloride of sodium, in the form of chloride which is well washed and fused in a porcelain capsule. A fragment of zinc is placed upon the fused mass, and some dilute hydro- chloric acid poured over it. After twenty -four hours, the chloride of silver is completely reduced ; the spongy masses of silver are rinsed out, rubbed to a fine powder under water, and digested with dilute hydrochloric acid, to remove any zinc. It is then thoroughly washed and fused with borax to a reguline mass. Or the dry chloride of silver may be mixed with an equal quantity of anhydrous carbonate of soda, and the mixture introduced into a crucible, the bottom and sides of which are coated with as thick a layer as possible of carbonate of soda. The crucible is then heated for a length of time to low redness, and after- wards to the fusing-point of silver. 42. SILVER ASSAY. From argentiferous galenite tetrahedrite, chalcopy- rite, &c., even when intimately mixed with gangue, the whole of the silver, concentrated in a small quan- tity of lead, may be extracted in the following manner : 68 GOLD AND COPPER. One hundred grms. of galenite, finely powdered, are fused with 30 grms. of nitre and 100 grms. of litharge. Or 1 part of the ore is fused together with 30 to 50 parts of litharge. Or 1 part of ore may be fused with 3 parts of anhy- drous acetate of lead and 2 parts of potashes, under a layer of common salt. In the button of lead obtained, the silver is deter- mined by cupellation, or in the moist way. 43; GOLD AND COPPER. (Coins.) li The alloy is dissolved in a mixture of hydrochlo- ric and nitric acids, care being taken that none of the latter shall remain undecomposed after the solution is effected ; the liquid is heated with oxalic acid, which precipitates all the gold in the metallic state. For the complete precipitation of the gold, the solution must be dilute, and not contain a large excess of hydrochlo- ric acid, or alkaline chlorides. It is washed, dried, transferred to a porcelain crucible, the filter completely incinerated, and the gold, together with the ashes, ig- nited and weighed* From the filtrate the copper may be precipitated by sulphuretted hydrogen, or by potassa at a boiling heat. II. The gold is first precipitated by a solution of pure protosulphate of iron, and the copper is after- wards separated from the solution, either by sulphu- retted hydrogen, or by a piece of bright iron placed in the liquid, which must not be too acid, and should be heated nearly to boiling. The precipitated copper is washed, dried, and ignited in air, when it is converted into oxides GOLD AND SILVER. 44. GOLD AND SILVER. I. From an alloy containing less than about 15 per cent, of silver, aqua regia dissolves all the gold, while the whole of the silver is left as chloride ; for this pur- pose, however, the metal must be employed in a very thinly laminated state. The solution is evaporated, to expel as much of the nitric acid as possible; and di- luted with water, to effect the complete separation of the chloride of silver. From the solution the gold is precipitated by oxalic acid, or by protosulphate of iron. II. If the alloy contain more than 80 per cent, of silver, pure nitric acid dissolves the whole of the silver, and leaves the gold. Here also the alloy must be thinly laminated. The silver is precipitated by hydrochloric acid. The gold is well washed, and dissolved in aqua- regia, to ascertain if any trace of silver be left in it. III. When the quantity of silver present in the alloy is between 15 and 80 per cent., it cannot be entirely extracted by nitric acid, neither can all the gold be dissolved out by aqua regia, since the metal becomes covered with a thick layer of chloride of silver. Such an alloy should be fused in a porcelain crucible with 3 times its weight of pure lead. From this alloy, nitric acid then dissolves all the lead and silver, leaving pure gold. From the solution filtered from the gold, the silver is precipitated by hydrocyanic acid ; or, after diluting largely, and heating nearly to boiling, by hydrochloric acid. IV. Silver and gold in alloys of these metals may also be separated by concentrated sulphuric acid, whatever may be the relative proportion of the two metals. The thinly laminated alloy is heated with the acid in a capacious dish, until all evolution of gas 70 AMALGAMS. ceases, and the acid begins to evaporate. The sulphate of silver which is produced is then dissolved in the requisite quantity of hot water, and the solution de- canted from the gold, which, for greater certainty, is once more heated with a small quantity of sulphuric acid ; afterwards thoroughly washed, ignited, and weighed. Y. All such alloys may be also conveniently ana- lyzed by fusion with bisulphate of potassa. 45. AMALGAMS. The following amalgams may be analyzed by heating very gradually in a porcelain crucible, finally raising the heat to redness, till the mercury is entirely vola- tilized, and the tin or copper oxidized. To insure complete oxidation, the mass is ultimately moistened with concentrated nitric acid, and again ignited. The amalgam of silver leaves the latter in the metallic state. In order to estimate the mercury also directly, the fol- lowing method is adopted : — I. AMALGAM OF COPPER.*— The amalgam is dis- solved in aqua regia, the solution neutralized, though not completely, with potassa, mixed with formate or sulphite of potassa or soda, and allowed to stand for some time at a temperature between 50° and 60°. All the mercury is thus precipitated as subchloride. Above 60°, metallic mercury would also be separated. The subchloride of mercury is collected upon a filter, * Tins amalgam, which is semi-fluid at 100O,but solid and crys- talline at the ordinary temperature, is obtained when copper, which has been precipitated by zinc, is moistened with nitrate of suboxide of mercury, and triturated in a warm mortar with mer- cury, added by degrees, until the amalgam has the consistence of butter. AMALGAMS. 71 which has been dried at 100° and weighed, and its weight determined after drying at 100°. From the filtered solution the oxide of copper is pre- cipitated, at a boiling heat, by caustic potassa. II. AMALGAM OF TIN (amalgam for mirrors). — This is dissolved in aqua regia, the solution mixed with am- monia in slight excess, afterwards with an excess of sulphide of ammonium, and digested for a long time in a closed vessel. The bisulphide of tin which is formed dissolves in the sulphide of ammonium, and the black sulphide of mercury separates ; it is collected upon a weighed filter, washed with weak sulphide of ammonium, and dried at 100°. From the solution in sulphide of ammonium the bi- sulphide of tin is precipitated by dilute hydrochloric acid, filtered off, washed, dried, and roasted, together with the filter, in a porcelain crucible, with free access of air. A gentle heat is at first applied, which is gra- dually increased, till the whole of the precipitate is converted into white binoxide of tin; a fragment of carbonate of ammonia is held in the ignited crucible at the end of the operation. III. AMALGAM OF SILVER.* — The amalgam is dis- solved, by the aid of heat, in nitric acid, so that the solution may contain the whole of the mercury in th (together with various extraneous substances, in varia- ble quantities, including silica, iron, nickel, cobalt, zinc, copper, bismuth, lead, manganese, arsenic, antimony, sulphur, lime, and manganese ; sometimes also selenium and vanadium). PREPARATION OF PURE SESQUIOXIDE OF URANIUM. — The finely-powdered ore is digested with moderately dilute sulphuric acid, with gradual addition of nitric acid, until it is converted into a white powder, and partly dissolved. The greater excess of sulphuric acid is then evaporated, the mass digested with much water, and the cold solution, after subsidence of the residue, filtered off. The residue consists of silica, sulphate of lead and basic sulphate and arsenate of bismuth. The solution is then heated to about 60°, and sul- phuretted hydrogen-gas passed through it, at this temperature, for some time; the solution is afterwards allowed to cool while the gas is still passing, and, when URANIN1TE. 193 fully saturated, set aside in a covered vessel for twenty- four hours. The sulphuretted hydrogen is then ex- pelled by a gentle heat, and the precipitate filtered oft'. The precipitate contains arsenic, antimony, copper, and the rest of the lead and bismuth. The solution is then heated to ebullition, and fuming nitric acid gradually added to the boiling liquid, until all the protoxide of iron is reconverted into sesquioxide, and the solution has acquired a pure yellow color. It is then precipitated by an excess of ammonia, and the yellowish-brown precipitate filtered off. Part of the nickel, cobalt, zinc, lime and magnesia remain in solution, but the remainder is precipitated together with the sesquioxides of uranium and iron. The washed precipitate is treated with a hot, pretty strong solution of carbonate of ammonia containing free ammonia, with which the precipitate is digested, at a moderate heat, until it has the appearance of hy- drated sesquioxide of iron. The solution of uranium is rapidly filtered off, while hot, and the residue of hydrated sesquioxide of iron (still containing uranium) is washed, the washings being received apart fronflhe filtrate. The solution (which is yellow, or colored reddish by the cobalt) deposits on cooling, if sufficiently con- centrated, crystals of the pure double carbonate of ammonia and sesquioxide of uranium, which may be collected, and washed several times with cold water. When ignited, this salt leaves pure dark green proto- sesquioxide of uranium. The mother-liquor is mixed with the washings and sulphide of ammonium carefully added, drop by drop, as long as it produces a dark brown precipitate, which is immediately filtered off. The precipitate consists of the sulphides of cobalt, nickel and zinc. The yellow filtrate is then boiled till the greater part 17 194 URANIN1TE. of ammoniacal salt is volatilized, and all the sesqui- oxide of uranium precipitated. The pure yellow precipitate, uranate of ammonia is filtered off, and, when the filtrate begins to pass through turbid, washed with solution of sal-ammoniac. When ignited, it leaves dark green proto-sesqui- oxide of uranium. By digesting this with dilute hydrochloric acid, any lime and magnesia may be extracted. In order to prepare protoxide of uranium from the uranate of ammonia, it is dissolved in hydrochloric acid, the solution mixed with an excess of pure sal- ammoniac, and about an equal quantity of pure com- mon salt ; it is then evaporated to dryness, and the mass heated in a covered crucible until the sal-ammo- niac is volatilized, and lastly, until the common salt fuses. On dissolving it in water, the protoxide of uranium is left as a heavy crystalline powder. The common salt only serves to shield the oxide from the action of air. When the quantity is very small, the uranate of ammonia is calcined and the proto-sesquioxide is dis- solved in hydrochloric acid with a few drops of nitric acid; the addition of chloride of potassium forms a substance U2 O2 01 + R 01. It is evaporated to dryness and the yellow salt ignited in a current of hydrogen. In order to extract from the hydrated sesquioxide of iron the small quantity of sesquioxide of uranium which is chemically combined with it, it is dissolved in the smallest possible quantity of hydrochloric acid, the solution neutralized with carbonate of ammonia, and added, drop by drop, with constant stirring, to a mixture of carbonate of ammonia and sulphide of ammonium, when all the iron is separated as sulphide, and the sesquioxide of uranium remains in solution; the latter may be precipitated by boiling the filtrate. Or the sesquioxide of iron may be reduced in a SELENIFEROUS DEPOSIT. 195 stream of hydrogen, and the reduced pyrophoric mass allowed to fall, immediately, into dilute hydro- chloric acid, which dissolves the iron, leaving the uranium a protoxide. In order to detect selenium, arsenic, and vanadium in pitch-blende, it is ignited with J of its weight of a mixture of carbonate of soda and nitre. The sele- nates, vanadates and arsenates of the alkalies may then be extracted with water. 105. SELENIFEROUS DEPOSIT FROM SULPHURIC ACID CHAMBERS. (Sulphate of lead, selenium, selenide of mercury, selenates selenites, &c.) The dry mass is rubbed to a thin paste with a mix- ture of about equal parts of sulphuric acid and water, and boiled for a long time, concentrated nitric acid or chlorate of potassa being added at intervals, to oxidize the free selenium, until all the reddish color has dis- appeared. The mixture is then diluted with water and filtered. The solution contains, besides iron, copper, mercury and a little lead, all the selenium as selenious and selenic acids. It is mixed either with about as much common salt as amounts to half the weight of the deposit originally employed, or with J of its volume crude of fuming hydrochloric acid, and boiled down to about J of its original bulk. The hydrochloric acid reduces the selenic acid to selenious acid. On cooling, the solution is poured off from any sulphate of potassa and common salt which may have been deposited ; these are washed several times with water, and the solution saturated with sulphurous acid gas, evolved from a mixture of powdered charcoal and concentrated sulphuric acid. 196 SELENI FERGUS DEPOSIT. The selenium is thus precipitated of a fine red color. Its separation is promoted by digestion, and ultimately by boiling for a quarter of an hour, when it becomes black, and collects into a dense hard mass. It is well washed and dried. The filtered liquid is boiled once more with hydro- chloric acid, and again treated with sulphurous acid, in case it should still contain selenium. The selenium thus obtained contains still small quantities of lead, copper, and iron, and especially mer- cury. On distilling it in a small retort or bent tube closed at one end, the first- mentioned impurities are left behind as selenides. In order to free it from mercury, the distilled sele- nium is dissolved in aqua-regia, the greater excess of acid evaporated, so that no nitric acid may remain, the solution mixed with excess of carbonate of soda, eva- porated to dryness, and the saline mass ignited to expel the mercury. The mass is redissolved in water, the solution boiled with hydrochloric acid, and the selenium again preci- pitated by sulphurous acid. Or the ignited mass may be mixed with about an equal weight of chloride of ammonium, and heated in a retort till the greater part of that salt has sublimed, when the selenium is reduced, and remains behind on dissolving the saline mass in water. The selenium may also be at once extracted, and obtained free from mercury, by fusing the deposit, with an equal weight of carbonate of soda and about £ of nitre, in a crucible. When the mass is in a state of tranquil fusion, it is poured out, so as to leave the oxide of lead, as far as possible, at the bottom of the crucible. It is then dissolved in water, the solution acidulated with sulphuric acid, the precipitated sul- phate of lead filtered off, and the filtrate treated, as above, with hydrochloric acid and sulphurous acid. SELENIUM SOOT. 197 It is necessary in this process that all the nitric acid from the nitre should either be expelled or decomposed, for otherwise part of the selenium will escape preci- pitation. Or the solution of the fused saline mass is saturated with hydrochloric acid, chloride of ammonium added, evaporated to dryness, and the mass heated in a retort until the chloride of ammonium begins to sublime, when all the selenium is reduced. 106. SELENIUM SOOT.* (Selenium with Selenides, Coal, Sand, &c.) The black mass is moistened with sulphuric acid, thoroughly washed, fully dried and distilled from a porcelain or hard glass retort, with a strong heat, until most of the selenium passed over nearly pure. The residue consisting of selenides, coal and other im- purities, is dissolved in hydrochloric acid with gradual addition of nitric acid, and while hot the copper and iron are precipitated by caustic soda, the solution filtered, and the selenium precipitated by saturating with sulphurous acid, or reduced by adding an excess of chloride of ammonium, evaporating to dryness and heating until the chloride of ammonium begins to sub- lime, when the alkaline salt is washed out. If the selenium is precipitated directly from the solution containing copper more or less of this metal is thrown down. In order to detect and separate the sulphur in the selenium, it is dissolved in very strong nitric acid, the * It collects in the chimneys where the copper ores are roasted at Mansfeld. It contains from 30 to 40 per cent, of selenium after it is washed and dried. 17* 198 CLAUSTHALTTE. solution mixed with hydrochloric acid, heated for some time to boiling, and the sulphuric acid precipitated by chloride of barium. The excess of baryta in the fil- tered solution is then precipitated by sulphuric acid, and afterwards the selenium by sulphurous acid. In order to prepare selenious acid, the selenium is dissolved in nitric acid, carefully evaporated to dryness, and the acid sublimed in a retort. To prepare selenic acid, the selenious acid is satu- rated with pure carbonate of copper and chlorine passed into it until all the selenious salt is dissolved. The solution is then again saturated with carbonate of cop- per, concentrated by evaporation, and the selenate of copper precipitated by alcohol, the chloride of copper remaining in solution. The precipitate is first washed with alcohol, then dissolved in water and the copper precipitated by sulphuretted hydrogen. 107. CLAUSTHALITE. (SELENIDE OF LEAD.) PbSe. The analysis is best effected, like that of tetrahedrite (No. 63), by means of chlorine-gas (Fig. 21). After the decomposition, the bulb is again weighed, in order to ascertain the amount of lead present. The greater part of the selenium is volatilized in the form of the solid chloride ; only a small quantity of the liquid chloride passes over at first. These are conducted into water, which is afterwards saturated with chlorine, in order to convert all the selenious acid into selenic acid ; the latter is then precipitated by chloride of barium, and the selenium determined as selenate of baryta; 100 parts of the latter correspond to 28.2 of selenium. CLAUSTHALITE. 199 If the metallic selenides are mixed or combined with the metallic sulphides, as, for example, in the na- Fig. 21. tive selenide of mercury which contains sulphide of mercury, the sulphuric acid and selenic acid formed in the analysis are precipitated together by chloride of barium, the precipitate ignited and weighed. A weighed quantity is then heated in a bulb-tube, through which a stream of dry hydrogen is passed, when the selenate of baryta is reduced, with great facility, to the state of selenide of barium, while the sulphate of baryta remains unaltered. The selenide of barium is then ex- tracted with dilute hydrochloric acid. In the same way the other metallic selenides which occur as minerals may be analyzed, viz., the selenide of silver and lead, the selenide of cobalt and lead, and the selenide of mercury and lead. In order to obtain the selenium from the selenide of lead occurring in many places in the Hartz, the mineral is powdered, treated with dilute hydrochloric acid to remove the calcareous spar and spathic iron-ore, well 200 CAST IRON. washed and dried. It is then very intimately mixed with an equal weight of carbonate of potassa contain- ing charcoal (calcined bitartrate of potassa), covered with coarse charcoal-powder in a crucible, the cover of which is then luted on, and exposed for an hour to a moderate red heat. When cool, the mass, which contains all the selenium as selenide of potassium, is quickly powdered in a warm mortar, thrown on a filter, and washed with well-boiled hot water, as long as the washings are colored ; during this operation, the funnel should always be kept full of water, so that the mass may not come in contact with the air. The yellowish-red solution of selenide of potassium begins immediately to deposit upon its surface a film of selenium, the whole of which separates, after some days, in the form of a thin reddish-black crust; only a small quantity remains in solution in an oxidized state. It may afterwards be precipitated by heating the solution with sulphurous and hydrochloric acids. Since selenide of lead frequently contains selenide of silver, the carbonaceous mass remaining after the extraction of the selenide of potassium may be fused with carbonate of potassa and some nitre. A metallic button of argentiferous lead is thus obtained, from which the silver may best be separated by cupellation. 108. CAST-IEON. For the detection and estimation of the foreign sub- stances, the total weight of which does not usually exceed 5 per cent.; it is best to employ separate portions of iron. I. CARBON. — The total amount of carbon may be determined by burning the iron, in the state of very fine filings, with the aid of a slow stream of pure CAST IRON. 201 oxygen, as in organic analysis; the carbonic acid which is produced being collected in a weighed potash bulb (Fig. 22). The whole amount of carbon may be determined more accurately by dissolving the iron in water, with 5 parts of iodine. The residue is filtered through as- bestos and afterwards ignited in a current of oxygen gas. Or it may be heated in a proper apparatus with six times its weight of bichromate of potassa and an excess of moderately concentrated sulphuric acid, when all the carbon is converted into carbonic acid. The iron may be treated at once in a similar manner. Fig. 22. Another quantity of the iron-filings is dissolved in dilute sulphuric acid, when the combined carbon is evolved in combination with hydrogen, while the graphite is left undissolved. In this operation, the gas may be conducted through a solution of acetate of lead, when the presence of sulphur is indicated by the precipitation of sulphide of lead. The residue insoluble in the acid is well washed, dried at 200°, and burnt, as above, in oxygen-gas. From the amount of carbonic acid, that of the graphite is calculated. II. SILICON. — The residue from the first carbon- determination, which contains all the silicon in the form of silicic acid, is dissolved in concentrated hydro- 202 CAST IRON. chloric acid, the solution evaporated to dry ness on the water-bath, the mass digested with dilute hydrochloric acid, and the silicic acid filtered off. III. PHOSPHORUS. — From the solution filtered from the silica, the phosphoric acid is separated as in No. 22. If the iron contain arsenic, it is obtained as arsenic acid, together with the phosphoric acid. Or a larger quantity of iron is dissolved in aqua- regia, precipitated with ammonia, filtered, dried without washing, mixed with about an equal portion of car- bonate of soda, heated to redness for half an hour, the mass completely dissolved in water, the solution concen- trated and the phosphoric acid precipitated as in No. 9. The amount of phosphorus may be less accurately determined by heating the fine iron-filings to redness with 2 parts of nitre and 1 part of carbonate of soda, extracting the mass with water, acidifying the solution with hydrochloric acid, and adding excess of ammonia and sulphate of magnesia. IV. ARSENIC. — The presence of arsenic may be de- tected by dissolving the iron in dilute sulphuric acid, filtering off the black residue, and digesting it with sulphide of ammonium. From the filtered solution Fig. 23. dilute sulphuric acid precipitates the pentasulphide of arsenic. The precipitate is dissolved in aqua-regiat the CAST IRON". 203 nitric acid expelled by evaporation, and the arsenic reduced in Marsh's apparatus. The solution of iron filtered from the black residue is neutralized with carbonate of soda, mixed with a few drops of sesquichloride of iron, and then with acetate of soda, when arseniate of sesquioxide of iron is precipitated, may be easily decomposed by sulphide of ammonium. For the quantitative determination of the arsenic, the cast-iron is dissolved in hydrochloric acid, with gradual addition of nitric acid, the solution filtered from the carbon, and heated with sulphurous acid till all the sesquichloride of iron is converted into pro- tochloride; the excess of sulphurous acid is then expelled by heat, and the solution saturated with sulphuretted hydrogen, and allowed to stand for twenty- four hours in a closed vessel ; the excess of gas is afterwards evaporated, and the precipitate filtered off. V. COPPER. — This metal is contained in the preci- pitate produced as above, by sulphuretted hydrogen. After drying, it is distilled in a tube, when sulphide of copper remains behind. Or the sulphide of arsenic may be dissolved out by solution of potassa, or more completely, by solution of monosulphide of potassium. VI. MANGANESE. — The solution filtered from the precipitate produced by sulphuretted hydrogen, in Y. is heated to the boiling-point, and the protoxide of iron entirely converted into sesquioxide by adding chlorate of potassa or hydrochlorite of soda. The oxide of manganese and sesquioxide of iron are then separated from each other by means of bicarbonate of soda, as in No. 25. VII. ALUMINUM. — The alumina is contained in the sesquioxide of iron which is then precipitated and may be separated from it as in No. 21. VIII. MAGNESIUM AND CALCIUM remain, together with the protoxide of manganese, in the solution fil- 204: CAST IRON. tered from the precipitate produced by bicarbonate of soda. (See No. 25.) IX. CHROMIUM AND VANADIUM.— A large quantity of the iron-filings is ignited with 2 parts of nitre and 1 part of carbonate of soda, the mass extracted with water, and the solution treated as in No. 100, when phosphoric and arsenic acids may likewise be sought. It is safer to employ for this purpose the carbonaceous residue obtained by dissolving a large quantity of the iron in dilute sulphuric acid. X. MOLYBDENUM. — Sometimes this metal is ex- tracted, together with the arsenic, by sulphide of ammonium, from the black carbonaceous residue; in such a case, it is reprecipitated, together with the pentasulphide of arsenic, an adding an acid to the solution. If this precipitate be distilled in a tube, the sulphide of molybdenum is left behind. If the cast-iron is rich in molybdenum, it is dis- solved in aqua-regia and the molybdenum precipitated by hydrosulphuric acid, placing in the acid solution at the same time a piece of zinc, which renders the precipitation complete. XL SULPHUR. — The sulphur may be determined ap- proximately by evolving it as sulphuretted hydrogen, as in No. 1, when the iron is dissolved in dilute sulphuric acid. Or it exists as sulphuric acid in the solutions obtained at III. and VI., and may be precipi- tated by chloride of barium. Or a large quantity of iron may be dissolved in aqua-regia, and the sulphuric acid formed may be precipitated from the diluted so- lution by chloride of barium. XII. NICKEL AND COBALT may be detected in the solution from which the copper has been removed by sulphuretted hydrogen. This solution is r-eoxidized, and the sesquioxide of iron precipitated by carbonate of baryta, after which the nickel and cobalt are pre- cipitated by sulphide of ammonium. ASH OF THE REFINING HEARTH. 205 For the detection of most of the admixtures, it is best to employ the black residue which is left on dis- solving the iron in dilute sulphuric acid, and which can easily be prepared in considerable quantity. It con- tains silicic acid, carbon, carbide of iron, phosphide of iron, arsenide of iron, compounds of chromium and vanadium with iron, molybdenum, &c. The total amount of the carbon (phosphorus, arsenic, chromium, &c. ?) in iron may be separated by digesting the fine iron-filings with a solution of chloride of copper, when all the uncornbined iron is dissolved, and copper precipitated in its stead. When the solution has been poured off, the precipitated metal is digested, out of contact of air, with a neutral solution of sesquichloride of iron which redissolves the metallic copper. When this residue is digested with potassa, the latter dissolves a newly formed brown humus-like substance, together with phosphoric acid, arsenic acid, and silicic acid. Almost the whole of the silicic acid may be determined in this residue. It is yet to be ascertained whether this residue can be analyzed by heating in chlorine-gas. 109. ASH OF THE REFINING-HEARTH. Crystallized=8 FeO, Si02. The analysis of pure crystals picked out of the mass is simple and easy, since they consist essentially only of protoxide of iron and silicic acid. They are finely powdered, and treated with hydrochloric acid and some concentrated nitric acid until they are completely gela- tinized, the analysis being conducted as in the case of Lievrite. The sesquioxide of iron obtained is calculated as protoxide. 18 206 ASH OF THE REFINING HEARTH. The quantitative analysis of the ordinary compact slag is far more difficult and -complex, since it may contain, in addition to the above principal constituents, small variable quantities of the protoxides of copper, nickel, cobalt, and manganese, besides the oxides of chromium, molybdenum and vanadium, together with alumina, potassa, lime, magnesia, arsenic and phos- phoric acids. Several of these constituents can only be discovered by a qualitative analysis, for which a large amount of slag is employed. The process is conducted as fol- lows : — A pound of the slag, powdered as finely as possible, is intimately mixed with a.i equal weight of nitre, and as much carbonate of potassa,* and exposed for an hour, in a crucible, to a moderate red heat. The mass is finely powdered, boiled out with water, the solution filtered off, and the residue washed several times with hot water. The solution may contain, besides alkaline carbonates and nitrites, vanadic acid, chromic acid, molybdic acid, arsenic acid, phosphoric acid, silicic acid, and alumina. A yellow color indicates the presence of chromic acid. It is now carefully mixed with nitric acid, so that it may still remain alkaline, and any silica which may be precipitated is filtered off. A yellow color at this stage of the process denotes the presence of vanadic acid. The liquid is then evaporated to crystallization, and the greater part of the alkaline nitrate allowed to crystallize out in as cool a place as possible. The mother-liquor is poured off from the crystals, which are washed several times with a little perfectly cold water ; the washings are mixed with the mother-liquor, and acetate of lead added as long as any precipitate is produced. This precipitate contains all the substances * Perhaps smaller quantities of both might be employed. ASH OF THE REFINING HEARTH. 207 above enumerated, in combination with oxide of lead. It is filtered off and washed once or twice. Chromic and vanadic acids cannot be completely separated from oxide of lead by means of sulphuric acid. The precipitate is therefore treated, while still moist, with a mixture of fuming hydrochloric acid and strong alcohol, with which it is heated nearly to ebul- lition, when all the lead and silica are separated in an insoluble state, and the metallic acids are converted into green chlorides, and dissolved together with the phosphoric and arsenic acids. The chloride of lead is filtered off and washed with alcohol ; the green solu- tion is evaporated to the consistency of a syrup, mixed with a slight excess of a concentrated solution of po- tassa, and chlorine passed into it until the metallic oxides have redissolved in the form of acids, imparting a yellow color to the solution.* The liquid is then neutralized with ammonia, concentrated as far as pos- sible by evaporation, allowed to cool, and a fragment of chloride of ammonium placed in it, so large as not to be entirely dissolved. The vanadic acid is thus almost completely precipitated as an ammonia salt, in the form of a white or yellow crystalline powder. After twenty-hours it is filtered off and washed, first with a saturated solution of sal-ammoniac, afterwards with alcohol. It may be purified by dissolving in boiling water with the addition of^some ammonia.f * Phosphate of alumina may precipitate here, and must be ana- lyzed separately. (See No. 19.) f It is possible that, if molybdenum be present, a yellow com- pound of phosphoric acid, molyLdic acid and ammonia might be precipitated here. It is insoluble in hot dilute nitric acid. This circumstance might be made use of for separating the molybdic acid at once from the solution after treatment with chlorine. The solution would be mixed with ammonia, and afterwards boiled, with addition of nitric acid in slight excess, when the compound would separate as a yellow powder. It contains 3 per cent, of phos- phoric acid. 208 ASH OF THE REFINING HEARTH. When dry, it is very gradually heated in a shallow platinum dish to expel the ammonia, and the residual vanadic acid is fused at a low red heat. If pure, it solidifies, on cooling, to a dark brown-red, very crystalline mass. The solution filtered from the vanadate of ammonia is mixed with ammonia, and afterwards with a solution of chloride of magnesium, which precipitates all the phosphoric, and most of the arsenic acid. After twenty-four hours, the precipitated double salts are fil- tered oft', washed with dilute ammonia, dissolved in hydrochloric acid, the solution heated to 50°, and the arsenic precipitated by a stream of sulphuretted hydro- gen-gas. In the filtrate from the sulphide of arsenic, the phosphoric acid may again be precipitated as a double salt by adding ammonia. The solution filtered from the magnesia precipitate, which still contains the chromic and molybdic acids, is saturated with sulphuretted hydrogen and heated, when all the chromium is precipitated as green sesqui- oxide. From the solution filtered from this precipitate, the molybdenum is precipitated by dilute sulphuric acid as a brown sulphide of molybdenum, from which, when heated in a tube, a mixture of sulphur and sul- phide of arsenic sublimes, while black lustrous MoS2 remains behind. The residue of sesquioxide of iron which is left after ignition with nitre and alkali, and extraction with water, is partly dissolved by digestion with con- centrated hydrochloric acid, and if sulphuretted hydro- gen be passed through the solution, the copper will be precipitated. The solution filtered from the precipitate is heated to the boiling-point, and a sufficient quantity of chlorate of potassa gradually added, to convert the protochloride of iron into sesquichloride. The small quantities of nickel, cobalt, and manganese which are GLASS. 209 present may be detected by precipitating the solution either with excess of ammonia or with carbonate of lime, when those metals remain in solution and may be precipitated by sulphide of ammonium. 110. GLASS. Silicates of CaO, and KO or NaO, frequently also, of PbO. Two analyses are made, one by fusion with an alkaline carbonate, for the determination of silicic acid ; the other by decomposing the glass with hydro- fluoric acid, in order to estimate the alkali. I. The very finely-powdered glass fused with three times its weight of carbonate of potassa and soda (No. 10), the mass softened in water, dissolved in dilute hydrochloric acid, evaporated to dryness, redis- solved in water, acidulated with hydrochloric acid, the silica filtered off and washed. From the solution, the small accidental impurities of sesquioxide of iron, oxide of manganese, and alumina, which are usually contained even in white glass, are precipitated by ammonia, after the solution has been mixed with some chlorine-water to perox- idize the protoxide of manganese. The lime is afterwards precipitated by oxalic acid, and the solution filtered from the oxalate of lime is tested for magnesia, which may, moreover, have been precipitated with the alumina. If the glass contain oxide of lead, that metal is pre- cipitated by sulphuretted hydrogen from the solution filtered from the silicic acid. II. For the determination of alkalies, a second quan- tity of the very finely-powdered glass is decomposed by hydrofluoric acid, or by ignition with carbonate of baryta, as in the analysis of feldspar, the subsequent 18* 210 CLAY. process being also conducted as in that analysis, so that the other bases may, if necessary, be again deter- mined here. 111. CLAY. 3 A12O3, 4 Si02 + 6 HO, with variable quantities of KO, MgO, FeO; MnO, Feldspar, Sand, &o. The water is determined by igniting the clay pre- viously dried at 100°. I. The clay is heated with concentrated sulphuric acid, the greater excess of acid evaporated, the residue dissolved in concentrated hydrochloric acid, by the aid of heat, and the silicic acid filtered off. If the clay contain an admixture of sand or feldspar, the silica is dissolved in a boiling concentrated solution of carbo- nate of soda, when the sand and feldspar remain un- dissolved. The hydrochloric solution is considerably diluted, and gradually neutralized with carbonate of soda, as in No. 25, so that sesquioxide of iron and alumina are precipitated, while protoxide of manganese, lime, and magnesia, remain in solution as bicarbonates. The separation of alumina and sesquioxide of iron is then effected as in No. 21, that of the other bases as in No. 25. II. The clay is fused with three times its weight of carbonate of potassa and soda (see No. 10), the fused mass dissolved in dilute hydrochloric acid, the solu- tion evaporated to dryness, the residue dissolved in water containing hydrochloric acid, and the solution filtered off'. The separation of the other bases contained in the solution is then effected as in I. III. For the determination of the alkali, a separate portion of the clay is decomposed by fusion with hy- LIMESTONE. 211 drate or carbonate of baryta, and the process conducted as in No. 80, the baryta and the other bases being pre- cipitated from the solution by a mixture of ammonia and carbonate of ammonia; after gently heating, the precipitate is filtered off, the solution evaporated, and the residue ignited, when chloride of potassium and chloride of sodium are left. Or the analysis may be made with a mixture of hydrofluoric acid and hydro- chloric acid. 112. COMMON LIMESTONE, HYDRAULIC LIMESTONE, MARL. Carbonates of CaO, MgO, FeO, MnQ, with Clay con- taining alkali, and sometimes 3 CaO, PO5. I. For the detection of the alkali, large fragments of the mineral, when it contains carbonate of lime in pre- dominating quantity, are placed in a charcoal fire, and heated for half an hour to whiteness, when the clay, which contains the alkali, is decomposed. The ignited mass is carefully freed from adhering ash, powdered, exhausted with water, the solution mixed with some carbonate of ammonia, evaporated, the pre- cipitated carbonate of lime filtered off, the solution acidified with hydrochloric acid, evaporated todryness, and the residual chloride of potassium or sodium heated to dull redness. If both salts be present, they are separated by bichloride of platinum. II. From a portion of the mineral which has been dried at 100° and weighed, the water is expelled by ignition in a glass tube, and its quantity determined by collecting it in a weighed chloride-of-calcium tube. III. The carbonic acid may be expelled from ano- ther portion of the mineral by nitric acid in the appa- ratus employed for testing potashes, and its amount determined directly by the loss of weight. (Fig. 24.) 212 IODIDE, BROMIDE, AND CHLORIDE OF SODIUM. Or a weighed quantity of the substance is fused with about four parts, accurately weighed, of vitrified borax, in a platinum crucible, when all the carbonic Fig. 24. acid is expelled, and its amount may be determined from the loss of weight, or if the water is expelled at the same time it must be taken into account in the calculation. (See No. 7.) IV. Another very finely powdered portion is di- gested with very dilute nitric acid, which dissolves the carbonates, together with the phosphate of lime, leav- ing the clay, which is filtered off, ignited and weighed. It is then analyzed as in No. 111. The separation of the other constituents present in the solution is effected as in No. 13. 113. IODIDE, BROMIDE, AND CHLORIDE OF SODIUM. The solution is mixed with nitrate of protoxide of palladium, when all the iodine is precipitated as dark brown iodide of palladium, the bromide of palladium IODIDE, BROMIDE, AND CHLORIDE OF SODIUM. 213 remaining in solution because chloride of sodium is present. After the lapse of twelve hours, the precipi- tate is collected upon a weighed filter, dried over oil of vitriol, or at a temperature not exceeding 80°, and weighed. The excess of palladium in the filtrate is separated by means of sulphuretted hydrogen, in order to pre- vent the formation of a precipitate containing palladium upon the subsequent addition of nitrate of silver. The excess of sulphuretted hydrogen is then removed from the solution by sulphate of sesquioxide of iron, and the filtrate mixed with nitrate of silver, when a pre- cipitate of chloride and bromide of silver is formed, which is collected, washed, dried, and fused. A quan- tity of this precipitate, weighed in a bulb-tube, is fused in a current of dry chlorine until bromine vapor ceases to be evolved, and the tube changes no longer in weight. Before weighing, every trace of chlorine must be removed from the bulb. A simpler method consists in pouring water over the weighed mixture of bromide and chloride of silver, adding a few drops of hydrochloric acid, and a frag- ment of zinc. In twenty-four hours the silver is com- pletely reduced; it is rubbed to powder, boiled with water containing hydrochloric acid, afterwards washed with pure water, ignited and weighed. The difference between the equivalents of chlorine and bromine is to the equivalent of bromine, as the difference between the amounts of chloride and bromide of silver employed, and the amount of chloride which the reduced silver ought to yield, is to the amount of bromine present. Itor example: 200 parts of a mixture of equal weights of chloride and bromide of silver gave, when reduced, 132,73 of silver, which would yield 176.31 of chloride of silver. Difference between the equivalents of chlorine and 214 CRUDE COMMON SALT. bromine=44.5. Difference obtained=23.69. Then 44.5 : 80=23.69 : x (=42.5 bromine). By the same indirect method, the amount of iodine contained in a mixture of iodide with chloride or bro- mide of sodium may be determined. The iodine may also be determined in a mixture of chloride and iodide of potassium or sodium, by adding a solution of sulphate of copper mixed with sulphurous acid, when the iodine is precipitated as white subiodide of copper, which is then washed. This method is also applicable for the approximative separation of iodine and bromine. In order to detect iodic acid with nitric acid (in nitrate of soda), a little silver is dissolved in it. All the iodine remains as insoluble iodide of silver. 114. CRUDE COMMON SALT. I. A weighed quantity of the moist salt is dried for some time at about 100°, then heated to about 300° in a covered crucible, and the water determined from the loss. II. For the estimation of the sulphuric acid, the salt is dissolved in water (when any insoluble impurities are left), the solution slightly acidified with hydrochloric acid and precipitated by chloride of barium. III. The lirne is determined in a larger quantity of the salt, by precipitating it from its solution by oxalate of ammonia, and filtering off the oxalate of lime when it has subsided. IV. The filtrate is concentrated by evaporation and mixed with ammonia and phosphate of soda to preci- pitate the magnesia; after the lapse of twenty-four hours, the precipitate is filtered off and washed with ammonia. INCRUSTATIONS FROM SALT-PANS. 215 V. The very small quantity of potassa which is usually present, may be detected by concentrating the solution of a large quantity of the salt so that a great part of the chloride of sodium may crystallize out ; the potassium is then precipitated from the mother-liquor with bichloride of platinum. VI. The bromine may be detected by passing chlo- rine into the mother-liquor obtained from a large quantity of the saline solution, and agitating the liquid with ether, which takes up the bromine, and thence acquires a yellow color. The bromine may then be converted into bromide of ammonium by adding am- monia. VII. In order to detect the iodine, the mother-liquor is mixed with some starch-paste, and weak chlorine- water added drop by drop ; or the vapor of bromine or of nitrous acid may be allowed to flow on to the surface of the mixture. For the quantitative determination of iodine and bromine, see No. 113. 115. INCRUSTATIONS FROM SALT-PANS. NaCI — NaO, SO,,— CaO, SO3,— MgO, SO,,— CaO, C02, MgO,C02. I. A weighed portion is heated nearly to redness in order to determine the water. II. Another portion is finely powdered and boiled with water, the residual carbonates of lime and mag- nesia filtered off, washed with hot water, and the two bases separated as in No. 12. This residue sometimes contains iron and manganese. III. The filtrate is mixed with chloride of ammo- nium, and the lime precipitated by oxalate of ammo- nia. (See No. 12.) . 216 MINERAL WATERS, WELL WATERS, ETC. IV. The solution filtered from the precipitate is mixed with ammonia, and the magnesia precipitated by phosphate of soda. (See No. 6.) V. Another portion of the incrustation is dissolved in hot dilute hydrochloric acid, and the sulphuric acid precipitated by chloride of barium (No. 3). VI. A smaller quantity is dissolved in dilute nitric acid, and the chlorine precipitated by nitrate of silver (No. 1). VII. The sodium and soda are calculated from the loss. VIII. In order to detect a small quantity of sulphate of potassa, a large quantity of the incrustation is finely powdered, boiled with an excess of hydrate of baryta, the solution filtered off, the lime and baryta precipitated by a mixture of ammonia and carbonate of ammonia, the filtrate acidified with hydrochloric acid and evaporated to dryness ; the residue is ignited, dissolved in water, and the solution treated with bi- chloride of platinum. In this process also, the soda which previously existed as sulphate, may be obtained in the form of carbonate. 116. MINERAL WATERS, WELL-WATERS, SALINE SPRINGS. It is supposed that the analyst has an unlimited quantity of water at his disposal, so that separate portions may be employed for the determination of most of the individual constituents. For the estima- tion of those substances which are present in large quantity, small portions of water must be employed, larger quantities being taken for such constituents as exist in small proportion. I. The specific gravity is first determined, in order to ascertain, by calculation, the weight of 10, 50, or MINERAL WATERS, WELL WATERS, ETC. 217 100 cub. cents, or grain measures of water, so that the quantities of water employed may be determined by measure. II. Carbonic acid and sulphuretted hydro yen- gases. — The apparatus represented by Fig. 25 is used to deter- mine the quantity of the air (nitrogen and oxygen) existing in the water. Fig. 25 A flask of the capacity of 2 or 3 litres is filled with the water as well as a tube suitable to collect the gases. When the apparatus is thus completely filled with water, the extremity of the bent tube is fastened under a graduated bell-glass full of mercury, and arranged over a mercury trough. The water is gently heated until it boils, and the air passes off* with the stream and the quantity is seen in the graduated bell-jar. The apparatus just described gives sufficiently exact results, when only the relation of the nitrogen and oxygen dissolved in the water is to be determined. It presents serious difficulties when carbonic acid is also to be determined ; the water which is condensed in the. tube being found in a sufficient quantity 19 218 MINERAL WATERS, WELL-WATERS, ETC. to dissolve this acid again in part or wholly. This difficulty may be avoided by making a very simple modification. A flask of the capacity from 400 to 500 cubic centimetres is used arranged as before. Fig. The apparatus being completely free from air, a caoutchouc tube is placed upon the end of the delivery tube to pass to the top of the small graduated bell- glass and kept there at a certain height. The height is regulated on the supposed volume of gas that boiling furnishes. It is at first gradually heated so as to cause a small quantity of water to pass out from the flask, the volume of which is accurately measured and subtracted from the first volume taken ; the delivery tube is then placed under the bell-jar, after which the temperature is gradually increased till the boiling point is reached. The bell-jar being nearly MINERAL WATERS, WELL-WATERS, ETC. 219 filled with gas and water which are evolved, the heat is instantly removed ; a vacuum results from this which causes the return of condensed vapor into the flask. This absorption taking place, it is again heat- ed. A certain quantity of gas is evolved which is added to that which the bell-glass already contains; when this is nearly full, the lamp is removed to determine the new absorption. This operation is re- peated three or four times until the volume of the gas remains stationary. The caoutchouc tube is drawn down the bell-jar into the mercury so that the upper portion contains only the gases which were in solution in the water with a very small quantity of this liquid, which may be greatly diminished by intro- ducing at the end of the operation some fragments of fused chloride of sodium. At length the gases con- tained in the bell-glass are measured, and the pro- portion of carbonic acid is determined by absorbing it by means of potassa. Fig. 27. UJ Sulphuretted hydrogen. — The water may contain sulphur in two forms, either combined with hydrogen 220 MINERAL WATERS, WELL WATERS, ETC. in the state of free hydrosulphuric acid, or combined with an alkaline metal (sulphide of sodium, potas- sium, &c.). The sulphur of the hydrosulphuric acid, and that of the alkaline sulphides are in general determined at the same time by a method depending upon the decora- position of these compounds by free iodine and upon the coloration that the slightest possible trace of iodine in excess communicates to starch. A standard solu- tion of iodine is made containing 1.27 grams of the iodine to a litre. 1 litre of this solution precipitates 0.16 gr. of sulphur, consequently, 1 cubic centimetre of it precipitates 0.00016 gr. A definite volume of sulphur water being placed in a flask a small quantity of starch is added to it; by means of a graduated cylinder, Fig. 27, the standard solution of iodine is gradually poured into the water, shaking the flask ; a drop of iodine in excess colors the liquid permanently blue. III. The total weight of the fixed constituents is ascer- tained by evaporating a measured quantity of the water to dryness, and carefully heating the residue to about 200°. Should the water contain much chloride of magnesium, an error will result from the partial decomposition of that salt, hydrochloric acid and magnesia being produced ; this may, however, be avoided by dissolving a weighed quantity of pure ignited carbonate of soda in the water before eva- porating. IV. The carbonates of protoxide of iron, protoxide of manganese, lime and magnesia, held in solution by free carbonic acid, are precipitated when a large quantity of water is boiled for an hour in a flask. The pre- cipitate is filtered off', dissolved in hydrochloric acid, the sesquioxide of iron precipitated by ammonia, and the protoxide of manganese, lime and magnesia sepa- rated as in No. 25. MINERAL WATERS, WELL-WATERS, ETC. 221 V. The silicic acid is left undissolved on treating the residue obtained by evaporation, with dilute hy- drochloric acid. Should the water contain carbonate of soda, it must be acidulated with hydrochloric acid previously to evaporation. If gypsum be present, a large quantity of water must be employed to redis- solve it. VI. Boracic acid may be detected by mixing the water with carbonate of soda, concentrating by eva- poration to a small bulk, and acidifying with hydro- chloric acid; if turmeric-paper be dipped in this solution, and dried, it will become brown if boracic acid be present. VII. The presence of nitric acid may be detected by adding to the partially evaporated water or to the residual salts, a few drops of water, colored with a solution of sulphate of indigo, and mixed with some hydrochloric acid, which has been boiled. On boiling, the solution will be decolorized. Some other bodies, especially free chlorine, have the same bleaching effect. Or if the concentrated solution is mixed with several times its volume of pure strong sulphuric acid, the mixture allowed to cool, and then a few drops of a concentrated solution of sulphate of protoxide of iron cautiously added so that the fluids do not mix, a red- dish purple or dark-brown stratum is produced ac- cording to the quantity of the acid present. Or the very concentrated solution may be heated with metallic copper and concentrated sulphuric acid, when yellowish red vapors of nitrous acid make their appearance. Or the dry residue may be mixed with anhydrous sulphate of copper or oxide of lead, and heated in a tube. If pieces of paper moistened with sulphate of protoxide of iron are held in the tube, they will be colored yellow or brown if nitric acid is-present. A very sensitive reaction consists in mixing the salt 19* 222 MINERAL WATERS, WELL-WATERS, ETC. with some starch paste containing iodide of potassium and sulphuric acid. A small piece of bright zinc is placed in the mixture which reduces the nitric acid to nitrous, and gives the iodine reaction. VIII. The chlorine is precipitated by nitrate of silver after acidifying the water with nitric acid ; the precipitate is treated as in No. 1. IX. Bromine and iodine, present only in very small quantity, can only be detected and estimated in large quantities of water, or in the mother-liquid. They are recognized as in Nos. 113 and 114. If the quantity of iodine present is very small a few drops of pure iodide of potassium and hydrochloric acid are added to the water, and the amyl reaction made. In order to concentrate the bromine, the water may be evaporated to dryness, and all the bromide of sodium, with but little chloride, extracted from the residue by absolute alcohol. When the alcohol has been evapo- rated or distilled oft) the residue is dissolved in water, and a small quantity of nitrate of silver added, with constant stirring, so that only about \ of the chlorine may be precipitated as chloride of silver ; the precipi- tate which contains all the bromine is weighed, and a certain portion of it analyzed as in No. 114. X. The sulphuric acid is precipitated by chloride of barium from the water slightly acidified with hydro- chloric acid. XI. Potassa and soda. — The water is evaporated to about one-half, and mixed, without filtering, with ex- cess of baryta- water ; the mixture is allowed to cool, and carbonate of ammonia added ; in this way, the sul- phuric acid, lime, and excess of baryta are precipitated. The filtrate is acidified with hydrochloric acid, evapo- rated to dryness, and the residue, which is a mixture of chloride of sodium, chloride of potassium, and chloride of magnesium, is then cautiously heated to redness. The three metals are separated as in No. 11. MINERAL WATERS, WELL-WATERS, ETC. 223 XII. Carbonate of soda. — The water is boiled for a long time, the precipitated earthy carbonates filtered off, and the filtrate divided into two equal parts. In one of these, previously acidified slightly with nitric acid, the chlorine is determined by precipitation with nitrate of silver. The other portion is mixed with a slight excess of hydrochloric acid, evaporated to dry- ness, and the residue heated nearly to redness ; it is then dissolved in water and precipitated by nitrate of silver. The difference between this amount of chloride of silver and the former, corresponds to the quantity of carbonate of soda which was contained in the water. XIII. Lime. — In the solution filtered from the pre- cipitate obtained in IV., the lime is precipitated by oxalate of ammonia, after addition of ammonia. (See No. 12.) XIV. Magnesia. — The solution filtered from the lime-precipitate is concentrated by evaporation, al- lowed to cool, mixed with concentrated ammonia, and the magnesia precipitated by phosphate of soda. (See No. 6.) XV. Lithia. — The lithia is best obtained from the mother-liquid according to the method given in XL The solution filtered from the precipitate is mixed with phosphate of soda, evaporated to dryness, and the residue treated with a very small quantity of water, when phosphate of soda and lithia is left, which should, however, be tested for magnesia. Or the mother-liquor may be evaporated to dryness with excess of carbonate of soda, the residue extracted with hot water, the filtered solution mixed with phos- phate of soda and evaporated to dryness. XVI. Strontia may be sought in the ferruginous and calcareous stalactites and ochreous deposits from waters containing carbonic acid. XVII. Phosphoric acid. — The foregoing remark ap- 224 SOILS. plies also to the phosphates. Or a large quantity of water may be evaporated to a small bulk, mixed with ammonia, the precipitate filtered off, dissolved in nitric acid, and tested for phosphoric acid with molybdate of ammonia. XVIII. Arsenic acid, in combination with lime or sesquioxide of iron, must likewise be sought, in the stalactites or ochres from such waters, with the aid of Marsh's apparatus. (See Poisoning by Arsenic.) XIX. Antimony and copper, to be tested for in the deposit, by sulphuretted hydrogen. XX. Fluorine, also contained in the deposit as fluoride of calcium. Or it may be sought in the pre- cipitate obtained by ammonia in XVIL, a part of which should be dried and moistened with concentrated sulphuric acid in a platinum crucible covered with a glass-plate coated with wax and marked in order to test for fluorine. (See No. 82.) 117. SOILS. The ordinary constituents of soils, which differ much in different soils, and are very variable in quan- tity, are salts of chlorine, sulphuric acid, phosphoric acid, silicic acid, carbonic acid, nitric acid, with potassa, soda, ammonia, lime, magnesia, alumina, protoxide of manganese and protoxide of iron, together with sand and organic matters consisting of the debris of plants, and of the humous substances produced by their decay. Some of these constituents are soluble in water. Others are insoluble in water, but soluble in dilute acids, as, for example, the carbonates and phosphates of lime and magnesia. The remainder are insoluble even in dilute acids; SOILS. 225 these consist of quartz and of particles of feldspar, mica, and hornblende arising from the disintegration of different kinds of rock. The soil to be examined is collected from different parts of the field, well powdered, allowed to dry in the air, and uniformly mixed. It is most convenient to determine the greater num- ber of the constituents in separate portions of the soil. I. Water. — A weighed portion of air-dried soil is heated to 100°, and retained at that temperature till its weight is constant. In this way the amount of hygro- scopic water is ascertained. In order to determine the combined water in the salts, clay, &c., the soil may be heated to 200° or 300°, when the ammonia also may be expelled. II. Organic matters. — The dry soil is ignited with access of air, moistened with carbonate of ammonia, and again heated nearly to redness. The loss in weight (ammonia and nitric acid being taken into ac- count) indicates the total amount of organic matter. The amount of nitrogenized organic matter can only be determined by ultimate analysis, when the ammonia and nitric acid must not be neglected in the calcula- tion. Certain organic substances, such as fatty and resinous matters, may be extracted from the dried soil by hot alcohol and ether. The humous substances may be extracted by boiling the soil with solution of potassa; they are separated, though not completely, from the brown filtered solution, in the form of a brown precipitate, on adding hydro- chloric acid. III. Ammonia. — The soil is distilled with solution of soda, and the ammonia collected and determined as in No. 5. IV. Nitric acid. — The analyst must be satisfied with the qualitative detection of nitric acid. The soil is ex- 226 SOILS. tracted with water, the filtered solution evaporated to a small bulk, and the reactions made, given under nitric acid, No. 116. V. The constituents soluble in water. — A large quan- tity of the air-dried soil, from 1000 to 2000 grammes, is heated nearly to ebullition, with water, for a consider- able time; the residue is filtered off and thoroughly washed with hot water. The whole liquid is evaporated to about its original volume, carefully weighed or measured, and separate portions of it, weighed or measured off, are employed for the determination of the following constituents. a. The total weight of the portion soluble in water is ascertained by evaporation to dry ness. b. Sulphuric acid is precipitated by chloride of barium from the solution acidified with hydrochloric acid. c. Chlorine is precipitated by nitrate of silver, after acidification with nitric acid. d. Silicic acid. — The solution is mixed with hydro- chloric acid, evaporated to dryness, the residue ex- tracted with dilute hydrochloric acid, and the silica filtered off. e. Lime, magnesia, alumina, protoxide of iron, andprot- oxide of manganese may be contained in the filtrate from d; they may be separated as in No. 81. /. Potassa and soda. — The solution is mixed with hydrochloric acid, evaporated to dryness, the residue dissolved in a little water, baryta- water added in excess, the mixture digested for some time, filtered off, and the baryta and lime precipitated from the filtrate by carbonate of ammonia. The solution filtered from these can contain only potassa and soda, which are es- timated as chlorides, and are separated as usual. g. Phosphoric acid, which can only be present if the solution contain no lime, &c., is precipitated as phos- phate of magnesia-ammonia. SOILS. VI. Constituents insoluble in water, but soluble in dilute hydrochloric acid. — From 50 to 100 grms. of the residue obtained in V. (previously washed, dried, and uniformly mixed), are weighed off, mixed with water, in a flask, to a thin paste, heatejd, and hydro- chloric acid gradually added until the effervescence ceases ; the mixture is then heated for some time, with frequent agitation, the insoluble residue filtered off and well washed. The solution is concentrated by evaporation, weighed or measured, and divided into separate portions for the different determinations. If the soil contain much organic matter, it must be feebly ignited with access of air previously to the extraction with hydrochloric acid. a. Silicic acid. — The solution is evaporated to dry- ness with addition of some nitric acid. b. Sulphuric acid. — From a weighed portion of the acid solution, filtered from the silica, the sulphuric acid is precipitated by chloride of barium. c. Alkalies. — Another portion of this solution is treated as in V.,/, with baryta- water. d. Phosphoric acid, lime, magnesia, alumina, protoxide of manganese, and protoxide of iron, are separated and determined in the greater portion of the solution filtered from the silica; according to the method given in No. 26. e. The carbonic acid, may be determined in a separate portion of the washed soil, as in alkalimetrical exa- minations. /. A small quantity of copper and arsenic some- times contained in the soil may be determined by a special experiment. (See No. 26.) VII. Constituents insoluble in dilute hydrochloric acid. — A small quantity (about 5 or 10 grms.) of the residue obtained in VI., is heated with several times its weight of concentrated sulphuric acid, until the greater part of the acid has been expelled. By this 228 ASHES OF PLANTS. treatment the clay is decomposed. The nearly dry residue is digested with dilute hydrochloric acid, the solution filtered off, and analyzed as above, omitting the determination of silicic acid. The residue left by hydrochloric acid is boiled for a long time with a concentrated solution of carbonate of soda, which dissolves the silica separated by the sul- phuric acid. The filtered solution is acidified with hydrochloric acid, evaporated to dryness, and the silica filtered off. The portion insoluble in carbonate of soda may be a mixture of sand, feldspar, and other minerals not decomposed by sulphuric acid, which maybe separated to some extent with the aid of a magnifier. In order to decompose them they must be treated as in the analysis of feldspar, No. 80. The greater part of the residue obtained in VI., pre- viously to treatment with sulphuric acid, may be mechanically separated, with tolerable accuracy, into its constituents, by levigation. The residue is stirred up with much water by means of a feather, and the finer suspended portions, consisting chiefly of clay,N are repeatedly poured off until only the grains of sand, feldspar, &c., remain behind. - 118. ASHES OF PLANTS.* Salts of KO, NaO, CaO, MgO, A1203, Fe2O3 and MnO, with 01, F, SO3, CO2, and SiO2. Manganese does not occur in all ashes, and is seldom present in sufficient quantity to determine. Fluorine has been hitherto found only in the stalks of some of the Oraminacese. Alumina is an essential con- stituent of the ashes of the Lycopodiacese, but is * By Professor Stadeler. ASHES OF PLANTS. 229 seldom present in appreciable quantity in other ashes. Even iodine, bromine, oxide of copper, and titanic acid have been found, though generally in very minute quantities, in some ashes. The process of analysis differs according as the ashes do or do not contain more phosphoric acid than is requisite to combine with the sesquioxide of iron, protoxide of manganese, lime, magnesia, and alumina. To the former (containing more phosphoric acid) belong those of seeds, to the latter, those of woods, succulent plants, &c. I. Ashes of seeds. — About 50 grms. of the seeds which have been dried in the air, or at 100°, are thoroughly carbonized by gentle ignition in a pla- tinum crucible; the carbonaceous mass is powdered, moistened with water, and exposed for some time to the air, when the sulphides are converted into sulphates ; it is then digested with concentrated acetic acid, water added, the mixture filtered, and the residue washed with hot water till the washings are only slightly acid to test papers. The carbonized mass is thus entirely, or almost entirely, freed from metallic chlorides; it is introduced, while yet moist, into a pla- tinum crucible, and incinerated as far as possible by a protracted gentle ignition. (At a bright red heat, phosphide of platinum is formed and the crucible corroded.) Finally, a few drops of concentrated nitric acid are added to the ash, which is then ignited in the crucible, the cover of which is placed against its mouth, until the last traces of carbon are burnt off, and a perfectly white ash remains. This ash is added to the saline mass obtained by evaporating the acetic solution ; the mixture is gently ignited to decompose the acetates, and weighed. The ash is dissolved by nitric acid in a carbonic acid apparatus, and the carbonic acid determined from the loss. 20 230 ASHES OF PLANTS. ,The solution is mixed with 10 or 12 volumes of water, and the residue, consisting of undissolved silica (sometimes also of sand) and charcoal, is collected upon a filter (previously dried at 100°), weighed, carefully removed from the filter, and digested with very dilute solution of soda, which readily dissolves all the silica, except that present in the form of sand j the residue of sand and charcoal is collected upon the filter previously employed; its weight, after being dried at 100°, is deducted from the total weight of the ash. The weight of the silicic acid is determined from the loss. From the filtered solution containing the saline constituent, the chlorine is precipitated by nitrate of silver, an excess of the precipitate removed by hydro- chloric acid, the sulphuric acid precipitated by chloride of barium, and the excess of baryta separated by careful addition of sulphuric acid. The filtrate is evaporated to dryness, the residue treated with concentrated hydrochloric acid, and di- gested with it for some time, in order completely to expel the nitric acid, and to convert any pyrophos- phoric acid into the tribasic form. The hydrochloric acid is expelled as far as possible, a sufficient quantity of water afterwards added, and the solution filtered from the undissolved silica, which is ignited, weighed, and calculated together with that previously obtained. From the solution, the iron, manganese, alumina, lime, and magnesia, are precipitated by ammonia as phosphates, which are collected, after six or eight hours, upon a filter, ignited and weighed. The pre- cipitate is dissolved by digestion with concentrated hydrochloric acid, the free acid nearly neutralized with soda, and the solution mixed with acetate of soda, when the phosphates of sesquioxide of iron and alumina are precipitated. These are ignited and weighed, and if necessary (unless the ignited precipitate has a pure ASHES OF PLANTS. 231 brown color), separated according to No. 19. — From the filtrate, the lime is precipitated by oxalate of am- monia, and the magnesia as phosphate of magnesia- ammonia, by merely adding an excess of ammonia ; the phosphoric acid previously in combination with the lime is calculated from the loss. — If manganese be present, it is precipitated together with the phosphate of magnesia-ammonia, to which it imparts a gray or black color after ignition. The separation is effected as in No. 26. The solutions from which the phosphates have been precipitated by ammonia, now contain only the alka- lies and the remainder of the phosphoric acid. The latter is precipitated (together with sulphuric acid) by chloride of barium, and the excess of baryta removed by sulphuric acid or by neutral carbonate of am- monia ; the filtrate is evaporated to dryness, the residue ignited, and the alkalies weighed as chlorides or sul- phates. For their separation, see No. 4. — The preci- pitate produced by chloride of barium is exhausted with nitric acid, sulphuric acid added to effect the complete separation of the baryta, and the phosphoric acid precipitated from the filtrate, previously mixed with an excess of ammonia, as phosphate of magnesia- ammonia. II. Ashes of wood, vegetables, &c. — Of those vegetables which yield a large amount of ash, 50 grms. may be taken for examination ; but of the different kinds of wood, which are usually poorer in mineral constituents, and of the Graminacede, the ash of which contains much silica, about 100 grms. should be employed. The substances are carbonized in a platinum crucible, and the mass thrown immediately into a flat porcelain dish, where it generally smoulders for a long time, and is, for the most part, converted into ash. The incineration is completed in the platinum crucible. The analysis of these ashes only differs from that 232 GUANO. of the preceding in that these contain a larger quan- tity of the alkaline earths than is necessary to com- bine with the phosphoric acid, so that the total amount of that acid is separated upon adding am- monia. The precipitate is immediately filtered off, and the filtrate mixed, first with sulphide of ammonium, to precipitate the manganese, then with oxalic acid for the lime, and lastly with phosphate of ammonia to separate the magnesia. Any excess of phosphoric acid may be separated, as directed above, from the alkalies, which are then weighed as chlorides or sul- phates. The stalks of the Graminacese usually leave an ash which cannot be completely decomposed by nitric or hydrochloric acid. The weighed silicate remaining undissolved, is decomposed most conveniently with hydrofluoric acid, and the bases, previously in combi- nation with silicic acid, may then be estimated in the solution. The silicic acid is determined from the loss. In this case, the determination of the charcoal and sand must, of course, be omitted. (See also for other, and, in part, newer and better methods, Liebig's and Kopp's Jahresbericht; 1850, p. 603; 1857, p. 582 and 584; 1859, p. 693.) 119. GUANO. Guano consists of the partially decomposed excre- ment of sea-birds. It contains a great many sub- stances, some soluble, others insoluble in water. The constituents upon which depend its important action and application as a manure are: organic, chiefly nitrogenized matters ; salts of ammonia ; phosphates, especially phosphate of lime ; and salts of the alka- lies. The amount of these constituents indicates the GUANO. 283 value of the guano. It is important to test this manure, since different specimens consist not only of various kinds of genuine guano of different degrees of richness, but samples also come into the market which are adulterated with common earth, loam, lime, sand, pebbles, and crude common salt or Glau- ber's salt. Genuine guano presents the appearance of a moist yellowish-brown earth, mixed here and there with white fragments or lumps. Very few and rare speci- mens are white. It has a peculiar excrementitious or urinous odor, and a feeble penetrating saline taste. It is chemically tested in the following manner : — I. The guano is mixed, in a dish, with hydrate of lime (slaked lime stirred with water to a thin cream), when it should emit, especially when heated, a power- ful odor of ammonia. In order to compare different specimens, the same quantity, say J oz. of each, is taken. Since the value depends partly upon the amount of ammonia present, the better sorts of guano will evolve the stronger odor of that gas. II. Two ounces (or from 50 to 60 grins.) of guano, finely powdered and uniformly mixed, are weighed in a counterpoised porcelain capsule, and heated on a water-bath until it is perfectly dry and suffers no far- ther diminution of weight. The loss of weight expresses the amount of moisture contained in the guano. Good guano loses only between 8 and 15 per cent, of water, but if fraudulently moistened, it may lose 20 per cent., or even more. III. Half an ounce (or from 15 to 20 grms.) of guano is weighed, and heated over a large spirit-lamp, or gas-burner, in a porcelain or platinum crucible, with free access of air, until all organic matter has burnt off', and the guano is converted into a white or grayish ash. Good guano, when treated in this way, leaves from 30 to 35 per cent, of ash, while bad guano leaves 20* 234: GUANO. from 60 to 80 per cent., and that which has been fraud- ulently adulterated leaves still more. The ash of gen- uine guano, whether of good or bad quality, is always white or grayish ; a yellow or reddish color bespeaks an admixture of clay or earth. Good guano, when first heated, evolves white vapors, with a powerful odor of ammonia. IV. A similar quantity of guano is mixed, in a dish, with several times its volume of water ; heat is then applied, and the mass thrown upon a small filter (pre- viously dried in the water- bath and weighed) ; the residue on the filter is washed with hot water till a small portion of the washing- water is not rendered tur- bid by adding chloride of calcium and ammonia. The filter, with the washed guano, is then thoroughly dried in a water-bath and weighed. The better the quality of the specimen, the less insoluble residue will be obtained. Gfood samples of guano leave from 40 to 45 per cent., those of bad quality as much as 70 or 80. If the guano be adulterated with common salt or with Glauber's salt, it will behave to this test like a genuine specimen, but furnish a greater quantity of ash in Ex- periment III. V. The guano under examination, may be treated with moderately strong hydrochloric acid. Good guano effervesces but slightly ; a specimen of guano adulte- rated with chalk, would effervesce strongly, and would leave a proportionally larger quantity of ash in Ex- periment III. VI. The ash obtained in III. is dissolved in dilute hydrochloric acid, which should give rise only to slight effervescence, if the guano be unadulterated. The so- lution is filtered from the residue, the latter washed, dried, thoroughly burnt, together with the filter in a weighed crucible, over the spirit-lamp, and weighed. This insoluble residue, consisting partly of sand, GUANO. 235 amounts, in good (undried) guano; to only 1 or 2 per cent. VII. The filtered hydrochloric solution is mixed with a slight excess of ammonia. The precipitate thus produced consists almost entirely of phosphate of lime. It is filtered off, washed, dried, and ignited ; its quan- tity in good guano amounts to 20 or 25 per cent. VIII. The filtrate from this precipitate should fur- nish only slight indications of lime on addition of oxalic acid ; but if the guano be adulterated with chalk, this reagent will produce a very considerable precipi- tate. This solution ought therefore to contain only the alkaline salts, amounting to 5 or 10 per cent, of the original undried guano. In order to determine them directly, which is generally unnecessary for practical purposes, the solution must be mixed with some more chloride of ammonium, and evaporated to dryness; the residue is heated to volatilize the excess of chloride of ammonium, and to convert the sulphates into chlo- rides, weighed, and farther treated as in No. 4. IX. The aqueous solution, which was obtained in the lixiviation-test (IV.), and of which a fresh quantity may be prepared so as to be saturated, has a brown color and a saline taste. When evaporated it evolves ammonia, emits a urinous odor, and leaves a brown crystalline mass, consisting chiefly of sulphates of potassa and soda, chloride of ammonium, oxalate and phosphate of ammonia. This solution exhibits the following reactions : — When mixed with hydrate of potassa, it smells strongly of ammonia. With chloride of ammonium, ammonia, and sulphate 9f magnesia, it gives an abundant pulverulent precipi- tate or phosphate of magnesia-ammonia. When acidified with acetic acid and tested with chloride of calcium, it gives a copious precipitate of oxalate of lime. 236 GUANO. After addition of excess of hydrochloric acid, it gives, with chloride of barium, a considerable precipi- tate of sulphate of baryta. X. When guano is exahusted with cold water, and the residue digested with a weak solution of caustic soda, uric acid is extracted. The solution is filtered, and feebly acidulated with hydrochloric acid, when the uric acid is precipitated. After being filtered off and washed, it is easily soluble in caustic potassa, and may be reprecipitated by hydrochloric acid. If it be dissolved in warm dilute nitric acid, the solution evapo- rated to dryness, and the residue moistened with carbonate of ammonia, a fine purple-red color is pro- duced. XI. The quantity of organic matter can be estimated directly only by an ultimate organic analysis. In good undried guano it amounts, taking the ammonia into account, to about 50 per cent. XII. The exact determination of the nitrogen re- quires also an ultimate analysis. This element should amount to 12 or 14 per cent.; bad samples contain only from 1 to 6 per cent. The quantity of nitrogen, may, however, be approximately determined by the following method, which therefore allows us to ascer- tain rapidly the value of different specimens of guano. It depends upon the circumstance that when guano is treated with a solution of chloride of lime(hypochlorite of lime), the nitrogen of the organic matter and of the ammoniacal salts is evolved as gas.* Instead of col- lecting and measuring the gas evolved, which would be scarcely practicable, on account of the violent effer- vescence, the volume of water which is expelled by the gas is ascertained by means of the simple apparatus * Farther experiments are required to show that all the nitrogen is here evolved in the gaseous state, and to ascertain how the various nitrogen-compounds behave with chloride of lime. GUANO. 237 represented in the figure ; it consists of a flask capable of containing about J pint, provided with a narrow Fig. 28. gas-delivery-tube bent twice at right angles. One limb, rather the shorter of the two, is passed, air-tight, through the cork of the flask, and bent upwards to prevent, as far as possible, the escape of bubbles of gas. This tube descends nearly to the bottom of the flask. A second very narrow short tube is also passed through the cork, and serves for the escape of air when the cork is introduced. The longer limb of the delivery-tube dips into a tall cylinder or tube, which is graduated to cubic centimeters, or cubic inches. The flask is half-filled with solution of chloride of lime ;* 1 grm. of guano is then weighed in the small glass vessel (the end of a test-tube) in which a few small shot have been placed, in order that it may float upright. With the aid of the handle of iron-wire shown in the figure, the tube is let down so as to float upon the surface of the solution of chloride of lime; the cork with the tube is * This solution must be carefully prepared and kept in a dark place, in a closed vessel. It must contain an excess of hydrate of lime, and therefore need not be perfectly clear. 238 OXALATE AND PHOSPHATE OF LIME. then tightly adjusted, the orifice of the smaller tube closed with wax, and the flask shaken so that the little vessel may fill and sink. A volume of liquid equal to that of the nitrogen evolved from the guano then flows into the graduated cylinder ; when no more liquid passes over, the cylinder is depressed so as to bring the liquid to the same level as that in the generating- flask ; the wax plug is then removed, the cork with- drawn, and the liquid still contained in the delivery- tube is allowed to run into the cylinder, where the whole is carefully measured. 1 grm. of good guano evolves between 70 and 80 cub. cents, of gas. 120. OXALATE AND PHOSPHATE OF LIME. A mixture of these two salts dissolves in^nitric acid without effervescence, and is precipitated from the solution by ammonia. If it be digested, when freshly precipitated, with acetic acid, the phosphate of lime may be dissolved, while the oxalate is left. If the mixture be previouly ignited, it dissolves in nitric acid with effervescence, and ammonia then pre- cipitates from the solution only the phosphate of lime, while the lime which had been in combination with oxalic acid remains in solution, and may be precipitated by oxalate of ammonia, and quantitatively determined. Phosphate of lime, when freshly precipitated, may be recognized by the yellow color which it assumes when moistened on the filter, with nitrate of silver. It is analyzed as in No. 13. If the two salts be dissolved in the smallest possible quantity of hydrochloric acid, and the solution mixed with an excess of acetate of soda, the oxalate of lime is precipitated, while the phosphate remains in solu- tion ; from the latter, the lime may be precipitated -by OXALATE AND PHOSPHATE OF LIME. 239 oxalate of ammonia, and afterwards the phosphoric acid by sulphate of magnesia and ammonia, as in No. 9. When the mixture of the two salts is treated with concentrated sulphuric acid, oxalic acid is converted into carbonic acid and carbonic oxide, so that by employing the apparatus described in the article upon alkalimetry, its amount may be inferred from the loss of weight. By gently heating the mixture with an excess of finely-powdered binoxide of manganese or neutral chromate of potassa, or with binoxide of lead and di- lute sulphuric acid, all the oxalic acid is converted into carbonic acid, the quantity of which may be determined by the use of the apparatus above alluded to. 2 equivs. of carbonic acid correspond to 1 equiv. of oxalic acid. If binoxide of lead be employed in this operation, the quantitative determination of the phosphoric acid may be effected at the same time; for this purpose, the mixture is digested for some time, to liberate the whole of the phosphoric acid; several volumes of alcohol are then added, in order to separate the sul- phate, of lime, the solution filtered, and the residue washed with alcohol. From the filtrate, after the evaporation of the alcohol, the phosphoric acid may be precipitated by sulphate of magnesia and ammonia. A very accurate method of estimating oxalic acid consists in converting it into carbonic acid by means of a solution of terchloride of gold, weighing the reduced gold, and calculating thence the amount of oxalic acid ; 3 equivs. of the latter reduce 1 equiv. of gold = 197. For this purpose the mixture of the two salts is dissolved in the smallest possible quantity of hydro- chloric acid (a large excess impedes the reduction in gold), mixed with an excess of a solution of terchloride of gold, or better, of sodio-chloride of gold, diluted with much water, and heated to ebullition. The re- 240 ALKALIMETRY. duced coherent gold is easily washed ; it is to be dried, ignited, and weighed. The excess of gold is removed from the solution by sulphuretted hydrogen, or by boiling with oxalic acid, and the phosphoric acid and lime are then separated and estimated as in No. 13. 121. ALKALIMETRY. The specimens of potashes and soda-ashes met with in commerce contain very variable quantities of foreign substances. The amount of carbonated alkali, upon which their value alone depends, varies between 40 and 95 per cent. The potashes contain chiefly chloride of potassium, sulphate, silicate, and phosphate of potassa, and carbo- nate, phosphate, ajid silicate of lime. The soda generally contains chloride and sulphide of sodium, sulphate, silicate and hyposulphite of soda, and often also hydrate of soda. The amount of alkaline carbonate present in the sample, may be determined by several methods. I. By the standard solution test, i. e., by exactly neu- tralizing a weighed portion with dilute sulphuric acid of known strength. In order to prepare the test-acid, a known quantity, say 70 grms. of concentrated sulphuric acid, are diluted with 600 grms of water. 5 grms. of pure anhydrous carbonate of soda are weighed, dissolved in hot water, and the solution colored blue with a little tincture of litmus. The test-acid is then added to the solution, from a burette, very carefully as the point of neutralization is approached, until the color is just changed to red, and ALKALIMETRY. 241 streaks which are made with the liquid upon litmus- paper, remain red after drying. The number of measures of acid employed is then observed, and the whole of the test-acid is diluted with so much water, that exactly 100 measures are required to neutralize 5 grms. of pure carbonate of soda. This stock of test-acid is preserved in a well-stopped bottle. It indicates immediately the percentage of caustic or carbonated alkali in a specimen of potashes or soda, provided that a quantity of the sample be employed, which is equivalent to 5 grms. of carbonate of soda. 100 measures of test acid saturate 5.000 grms. of oarb. of soda. 100 " " " 2 935 " of soda. 100 " " " 6.487 " of carb. of potassa. 100 " " « 4.421 " of potassa. So that if 6'487 grms. of a sample of potashes be taken, the number of measures of acid employed will express, directly, the percentage of carbonate of potassa, or if 4.421 grms. be used, of anhydrous potassa, con- tained in the specimen. Instead of sulphuric acid, pure crystallized oxalic acid may be very conveniently employed for preparing the test-solution. An equivalent of the acid (63 grms.) Fig. 29. is introduced into a flask of 1 litre capacity, which is then two-thirds filled with water ; the acid is allowed 21 242 ALKALIMETRY. to dissolve, and so much water added that the whole solution may measure 1 litre or 1000 cubic centime- tres, at 17.5° C. One hundred cub. cents, of this test-acid will then exactly neutralize TV of an equivalent proportion of either alkali. It is therefore necessary to weigh out y'g of an equivalent proportion (in grammes) of the anhydrous alkali to be tested, that is, 6*92 grms. of potashes, or 5'32 grms. of soda-ash. In order to obtain perfectly accurate results, the process is conducted as follows : The solution of alkali to be tested, is intro- duced into a flask colored, with tincture of litmus, and the test-acid poured into it from a burette, until the color changes from blue to violet, and the effer- vescence is very feeble. The solution is now heated to ebullition, and more acid added until the color has become decidedly red. 5 or 10 cub. cents, of the test- acid are then added in excess ; the alkali will be now supersaturated. By boiling, agitating, and finally suck- ing out with a glass tube, the last traces of carbonic acid are removed r -now required to determine exactly how far tne neutralization of the alkali has been exceeded ; for this purpose a standard solution of caustic soda is employed, of such strength that it is exactly neutralized by an equal volume of the test- acid ;* this solution is added from a burette graduated to T*$ cub. cent., when the red color rapidly changes to violet, and then suddenly to pure blue. The num- ber of cubic centimetres of soda-solution employed, is then deducted from the volume of test-acid previously added ; the remainder gives the percentage of pure alkaline carbonate. * This solution of soda must be perfectly free from carbonic acid. In order to preserve it in that state, the bottle is closed with a cork, through which passes an ordinary chloride-of-calcium- tube, open at both ends, and filled with a mixture of Glauber's salt and quicklime in powder. ALKALIMETRY. 243 The dropping-tubes or burettes employed for these analyses with standard solutions, are made of different forms. The commonest is that represented in Fig. 30 «, Fig. 30. and consists of a glass tube, closed at one end, about 0.25 metre (or 12 inches) long, and 0.01 metre (or f inch) in diameter ; into the lower part of this tube is cemented another, very much narrower, which is fixed parallel with the larger tube ; the extremity of the small tube is bent outwards and sharply cut off, so that the liquid may be conveniently poured from it. The whole of the vessel is divided into known volumes, and it is preferable to take from 25 to 50 cub. cents., and to divide these into fractional parts. The zero should be placed at the top of the scale, below the level of the orifice of the spout. Another form is that shown in Fig. 30 b, which consists of a single divided tube furnished at the top with a spout, and with an orifice for pouring in the liquid. A third form of burette, which is the most suitable 244 ALKALIMETRY. and convenient, and can be very easily made by the analyst himself, is that represented by the adjoining figure. It consists of a glass tube, about 0.01 metre Fig. 31. in diameter, which is divided into 25 or 50 cubic cen- timetres, and drawn out to a point at the lower ex- tremity. To this open point is attached a narrow tube of vulcanized caoutchouc, about an inch long, and in the lower end of this tube is inserted a short glass tube drawn out to a narrow point and cut smoothly off; this tube serves for dropping the liquid out, and is ALKALIMETRY. 245 tightly connected with the graduated tube in such a manner that a considerable interval may be left between the ends of the two tubes. Upon this part of the caoutchouc tube is fixed a clamp made of thick brass wire, shown with its actual dimensions, in the accompanying figure, so constructed that the caout- Fig. 32. chouc tube may be opened by pressing upon the two ends of the clamp, and closed when the pressure is removed. In order to use this tube, it is fixed in a stand, in a vertical position, above the vessel contain- ing the liquid to be tested. By pressing upon the ends of the little clamp, the caoutchouc tube is opened, and the liquid allowed to flow out, even in single drops, if required. At the commencement of the operation, the tube is filled with the test-liquid, a portion of which is then made to flow out, by pressing upon the clamp until it stands exactly at the zero of the scale. II. By determining the carbonic acid evolved. The carbonic acid is liberated from a weighed por- .tion of the alkali, in an apparatus which is previously weighed (together with the acid used to effect the decomposition), and the carbonic acid determined from the loss of weight. The apparatus employed for this purpose may be 21* 246 ALKALIMETRY. arranged in different ways. That represented in the adjoining figure, of about J its real dimensions, will render apparent the general principle, upon which they are constructed, and will itself fully answer the pur- pose. It consists of a small light flask, closed by a cork perforated with two holes, in one of which is inserted a tube filled with fragments of chloride of calcium, and in the other, a narrow glass tube, running Fig. 33. nearly parallel with the inner wall of the flask, and reaching almost to the surface of the liquid ; above the cork, this tube is bent at right angles. The specimen to be examined is weighed in the flask, the latter about one-third filled with water, and the small tube full of acid introduced with a pair of pincers ; this tube must be of such a length that it cannot fall down in the flask, but may assume the position indicated in the figure. Sulphuric acid is to be preferred for effecting the decomposition of the carbonate, and should be employed in quantity more than sufficient to expel the whole of the carbonic acid. (B'or the carbonates of lime, baryta, and lead, nitric ALKALIMETRY. 247 acid must be employed). — The cork, with the chloride- of-calcium-tube, and the bent tube is then introduced, air-tight, into the neck of the flask, the whole appara- tus accurately weighed, and the orifice of the bent tube perfectly closed with a small cork or with wax. The flask is then carefully inclined so that a small quantity of the acid may run out of the tube and de- compose the carbonate. The carbonic acid which is evolved escapes through the chloride-of-calcium-tube, in which any water which may have been carried off with it is retained. No fresh acid is allowed to flow out of the tube until the effervescence caused by the first portion has ceased, and does not recommence upon gentle agitation. When, at length, the effervescence has entirely ceased, so that the salt is completely de- composed, the plug is removed from the small tube and suction applied, by the mouth, to the tube contain- ing chloride of calcium, until the air passing through the flask no longer tastes of carbonic acid. In very exact experiments, a second chloride-of-calcium4ube must be attached to the small bent tube, to retain the moisture of the air. 1. Potashes. — The amount of water is ascertained by heating the specimen, for some time, to about 200°. For this purpose from 2 to 5 grms. of potashes may be taken. In order to determine immediately, without calcula- tion, the percentage of potassa in carbonate of potassa, by means of the above apparatus, 3.14 grms. of the specimen must be taken. Since 3.14 grms. of pure carbonate of potassa evolve 1.00 grm. of carbonic acid, the number of centigrammes of carbonic acid evolved will represent the percentage of carbonate of potassa. 2. Soda. — 2.41 grms. of soda are employed. This is the quantity of pure carbonate of soda which evolves 1.00 grm. of carbonic acid. Should caustic soda be contained in the specimen, 248 VALUATION OF MANGANESE ORES. which may be known by the alkaline reaction of the solution after adding an excess of chloride of barium, the following modification of the process is necessary : 2.41 grms. of the anhydrous sample are mixed with about 8 parts of pure quartz-sand, and about J part of powdered carbonate of ammonia; the mixture is moist- ened with water, and, after some time, gently heated till all water and ammonia are expelled. The dry residue is then treated, as usual, in the above appa- ratus. In order to prevent any inaccuracy arising from the presence of sulphide of sodium or hyposulphite of soda in the specimen, a solution of chromate of potassa is added previously to the evolution of carbonic acid, in order to oxidize these impurities. 122. VALUATION OF MANGANESE ORES. Good manganese ore, which consists almost entirely of binoxide of manganese, is crystalline, yields a black powder, and, after being dried at a gentle heat, gives no water, or only traces, when heated to redness. Man- ganese ore, however, generally contains foreign mine- rals, especially the hydratedsesquioxide of manganese. In order to determine the amount of binoxide, or, in other words, of available oxygen, several methods may be employed. I. A weighed quantity of the manganese ore, pow- dered as finely as possible, is introduced into the appa- ratus employed for the quantitative estimation of car- bonic acid (Fig. 34), where it is brought in contact with sulphuric acid and a solution of oxalic acid, when sul- phate of protoxide of manganese is produced, since all the available oxygen, which may be regarded as in VALUATION OF MANGANESE ORES. 249 combination with the protoxide of manganese, is evolved in the form of carbonic acid. Fig. 34. One equiv. of pure binoxide of manganese = 43.6, yields 2 equivs. = 44 of carbonic acid. So that 0.99 grm. of binoxide of manganese evolves 1.00 grm. of carbonic acid. It is best to employ three times, that quantity of the manganese ore, viz : 2.97 grms., which are mixed with a solution of 2.5 grms. of neutral oxalate of potassa ; the sulphuric acid is allowed to flow into this mixture, and the amount of carbonic acid evolved is divided by 3. The quotient expresses the percentage of binoxide of manganese contained in the ore. II. The finely-divided manganese ore is weighed, and mixed with water, in a flask capable of being tightly closed ; several bright strips of copper, previ- ously weighed, are then introduced, and a quantity of hydrochloric acid added. The flask is then closed with a cork and narrow tube, and the contents digested until all the manganese has dissolved, care being taken that no chlorine is evolved. The liquid is then heated 250 CHLORIMETRY. to ebullition for a quarter of an hour, the flask closed air-tight, and allowed to cool; the solution is poured off, the residual copper washed, first with very dilute hydrochloric acid, then with pure water, dried, and weighed. 2 equivs. of copper = 63.4 parts, require for their conversion into subchloride, 1 equiv. = 71 parts of chlorine. Then 63.4 : 71 as the amount of copper dissolved is to x (the amount of chlorine sought). 1.22 grms. of pure binoxide of manganese evolve 1.00 grm. of chlorine, and therefore are capable of effecting the solution of 1.78 grms. of copper. 123. CHLORIMETRY. The "bleaching powder''1 of commerce is a variable mixture of bypochlorite of lime and chloride of cal- cium, with hydrate of lime. When treated with an acid, it evolves the whole of the chlorine in a free state. In order to determine its value, i. e., the amount of available chlorine which it contains, different methods are employed. I. Fourteen grms. of pure arsenious acid are dis- solved in solution of potassa, and so much water added Fig. 35. CHLORIMETRY. 251 that the liquid may occupy 2000 divisions of the graduated burette. 100 measures, therefore, of this solution contain 0.7 grm. of arsenious acid, and the solution of chlorine which is required to convert this into arsenic acid, contains 0.5 grm. of chlorine, since 1 equiv.= 99 of arsenious acid, requires, for its conver- sion into arsenic acid, 2 equivs.= 71 of chlorine. Five grras. of chloride of lime are weighed off, inti- mately mixed with water, by trituration, rinsed into a cylindrical (Fig. 36) glass, and so much water added that the whole may occupy 200 measures of the burette. Figs. 36. 37. 39. One hundred measures of the arsenic-solution are then, by aid of the pipette (Fig. 37), introduced into a beaker, diluted with water, an excess of hydrochloric acid added, and the liquid coloured with one or two drops of sulph-indigotic acid. The solution of chloride of lime is well mixed by agitation, introduced into the burette (Fig. 39), and added to the colored arsenic-solution until the color just disappears. The solution of chloride of lime required to produce this effect contains 0.5 grm. of chlorine. For example, if 90 measures of the solution of chlo- ride of lime had been employed, the 5 grms. of chloride 252 ANALYSIS OF NITRE. of lime would have contained 1.111 grms. of chlorine, or 22.22 per cent. Perfectly pure chloride of lime (Ca C1 + CaO, CIO), which is never met with in commerce, contains 48.9 per cent, of available chlorine. II. A weighed quantity of chloride of lime is mixed with water, in a flask, an excess of protochloride of iron, free from sesquichloride, added, and afterwards some hydrochloric acid. Several bright weighed strips of copper are then introduced, and the solution boiled until the protochloride at first formed is converted into subchloride; the copper is then withdrawn, washed, dried, and weighed. The calculation is effected as in No. 121. 124. ANALYSIS OF NITRE. In order to determine the amount of moisture in crude nitre, from 5 to 10 grms. of the specimen, pre- viously reduced to powder and dried by exposure to air, are heated to about 150°. The determination of the quantities of the foreign salts present in the specimen, such as sulphates and chlorides, lime and magnesia, by the ordinary methods, would occupy too much time ; it would be preferable to estimate them by means of standard solutions of the reagents, i. e., by measuring the quantities of the latter required to effect complete precipitation. The appearance of the fracture is regarded as an indication of the quality of the nitre ; in pure nitre, the fracture is lustrous, and exhibits a well-defined crystalline appearance; but if not more than 2 per cent, of common salt be present, it is granular and dull. An admixture of nitrate of soda (Chili salt- petre) has the same effect. Another method, which is likewise, however, inac- ANALYSIS OF NITRE. 253 curate, but is most readily applied in practice, depends upon the circumstance that a solution of pure nitre, at the temperature at which it is saturated, is still capa- ble of dissolving other salts, especially chloride of sodium. 400 grms. of the powdered specimen are shaken with 500 cub. cents, of a solution of pure nitre; the salt is then filtered off, again washed with 250 cub. cents, of a saturated solution of nitre, dried at 100°, and weighed. The loss of weight expresses the amount of the foreign salts. Since this process is liable to error from many causes, and gives the amount of pure nitre, on an average, 2 per cent, too high, these 2 per cent, must not be neglected in calculating the amount of impurity present. The following process is more accurate, which con- sists in converting the nitre contained in any specimen into carbonate of potassa, the amount of which is then determined by means of the standard acid, as in testing potashes. 9.475 grms, of pure nitre furnish a quantity of car- bonate potassa, which is capable of saturating 100 measures of the acid mentioned in the testing of pot- ashes ; so that if this amount of impure nitre be em- ployed, the number of measures of acid indicate at once the percentage of pure nitrate of potassa in the specimen. One-fourth of the above quantity (2.369 grms.) of the crude nitre is weighed out, intimately mixed with 1 grm. of ignited lamp-black, or finely pulverized graphite,* and with 12 grms. of ignited and finely-pow- dered common salt, which serves to moderate the vio- * If common coal is used cyanide of potassium and cyanate of potassa may be formed. Pure graphite may be prepared by mix- ing Ceylon graphite with ^ of chlorate of potassa to which con- centrated sulphuric acid is added, and then warmed until no acid fumes are given off. The mass is then shaken with water, the graphite washed and ignited. 22 254 GUNPOWDEK. lence of the combustion. The mixture is introduced into a platinum crucible, and heated to redness over a large spirit-lamp or gas-burner. Near the close of the operation a little chlorate of potassa is scattered in the crucible in case the saltpetre happens to contain any sulphates. When cool, it is dissolved in water, and the standard acid added in the manner directed for testing samples of potashes. The number of mea- sures of acid employed is multiplied by 4, in order to obtain the percentage of pure nitre in the specimen. In following this method it is impossible to deter- mine the weight of the expelled carbonic acid by means of the apparatus generally employed for this purpose, on account of the large quantity of common salt which has been added. The simplest method for the analysis of nitre con- sists in fusing the weighed quantity of nitre with twice its weight of fused bichromate of potassa, until all the nitric acid is driven off. The loss in weight shows the quantity and also amount of pure nitrate of potassa. 125. GUNPOWDER. I. For the estimation of moisture, 5 or 6 grms. of powder are dried over sulphuric acid, or in the air- bath at 100°. II. A similar quantity of powder is moistened with water, triturated in a mortar, rinsed into a filter, and thoroughly washed. The solution of nitre thus ob- tained is evaporated to dryness in a small weighed porcelain dish, the dry residue heated for some time to 200°, or even till the nitre fuses, and its weight determined. III. In order to determine the sulphur, 5 grms. of powder are intimately mixed with 5 grms. of anhydrous HYDROCYANIC ACID. 255 carbonate of soda, 5 grms. of nitre, and 20 grms. of decrepitated chloride of sodium, and the mixture heated to redness in a platinum crucible. When cool, the mass is dissolved in water, the solution slightly acidified with nitric acid, and the sulphuric acid pre- cipitated by chloride of barium. (See No. 3.) The amount of carbon may be inferred by differ- ence. In order to determine its quality, and to ascer- tain whether it has been completely or incompletely carbonized, the mixture of sulphur and carbon is boiled with a solution of protosulphide of potassium, which dissolves the sulphur, leaving the carbon, which must be well washed and dried. The sulphide of potassium should not contain any free potassa, since this might dissolve an imperfectly carbonized char- coal.— Bisulphide of carbon may also be employed for the extraction of the sulphur. The sulphur as well as the coal may be completely oxidized by boiling with a solution of permanganate of potassa. The oxide of manganese is after wards, dis- solved by hydrochloric acid, and the sulphuric acid precipitated by chloride of barium. 126. HYDROCYANIC ACID. In order to determine the strength of a solution of pure hydrocyanic acid, a weighed quantity of it is treated with solution of nitrate of silver, which is added gradually, and with frequent agitation, until no further precipitation takes place, and the odor of hydrocyanic acid has entirely disappeared. The precipitated cyanide of silver is collected upon a filter (previously dried at 120° and weighed), washed, dried at 120°, and its weight determined. For the estimation of the amount of hydrocyanic acid in the aqua amygdalarum amararum and aqua 256 HYDROCYANIC ACID. faurocerasi, they must first be mixed with ammonia, then with nitrate of silver, and lastly with nitric acid. If hydrochloric acid be contained in the solution, together with hydrocyanic acid, they are both precipi- tated from a weighed portion of the solution by nitrate of silver, and the precipitate weighed upon a filter dried at 120°. Another weighed portion of the solution is mixed with solution of borax and evaporated to perfect dryness. In this way, all the hydrocyanic acid is volatilized, and the hydrochloric acid converted into chloride of sodium. The dry residue is dissolved in water, the solution acidulated with nitric acid, and the chlorine precipitated by nitrate of silver. Another method, which may be executed with great rapidity, and suffices for the determination of the hydro- cyanic acid in any solution, whether bitter almond- water or laurel-water, &c., or for ascertaining the quan- tity of cyanogen in crude cyanide of potassium, depends upon the circumstance that 1 equiv. of cyanide of potassium forms, with 1 equiv. of cyanide of silver, a soluble compound which is not decomposed by an ex- cess of alkali, but from which nitrate of silver precipi- tates the cyanide, or if a little solution of chloride of sodium be previously added, the chloride of silver. The weighed solution, containing hydrocyanic acid is mixed with solution of potassa till it has a strongly alkaline reaction, and a standard solution of silver is then added till a permanent precipitate begins to ap- pear. 1 equiv. of silver employed in the standard solution corresponds exactly to 2 equivs. of hydro- cyanic acid. Ten grms. of pure silver are dissolved in nitric acid, the solution evaporated to perfect dryness, and diluted with so much water, that the whole solution may occupy 1000 cub. cents. 100 cub. cents, of this solu- tion, which contain therefore 1 grm. of silver, repre- FERROCYANIDE OF POTASSIUM. 257 sent 0.5 grm. of anhydrous hydrocyanic acid, or 0.481 cyanogen, or 1.206 of cyanide of potassium. 127. FERROCYANIDE OF POTASSIUM. 2 K Cy -f-Fe Cy + 8 HO=K2 Cfy + 3 HO. The water is determined by heating the finely-pow- dered salt for some time to about 200°. The cyanogen can be directly determined only by an organic analysis, i. e., by a combustion. For the determination of the amount of iron, the salt is intimately mixed with 1J parts of nitre, and as much carbonate of soda, and the mixture gradually heated to redness in a platinum crucible. On dissolving the fused mass in water, the iron remains behind in the form of sesquioxide, which is washed, ignited, and weighed. Since it is liable to contain a small amount of alkali, it should be dissolved in hydrochloric acid, reprecipitated by ammonia, washed and ignited. In order to determine the potassium and iron, the salt is dissolved in water, and the solution precipitated by acetate of lead. The precipitate of ferrocyanide of lead is filtered off* and washed. From the solution, which contains all the potassium as acetate of potassa, the excess of lead is precipitated by sulphuretted hydrogen or sulphide of ammonium, the filtered solution evaporated, the residue ignited, the carbonate of potassa converted, by hydrochloric acid, into chloride of potassium, and weighed in that form, after gentle ignition. The ferrocyanide of lead is decomposed by digestion with sulphide of ammonium, the solution of ferrocyanide of ammonium filtered off, 258 EXAMINATION FOR ARSENIC evaporated, and the residual mass ignited, with access of air, until only pure sesquioxide of iron is left. Ferrocyanide of potassium may probably also be decomposed by beating with bisulphate of ammonia. The residue after ignition would then consist of a mixture of sesquioxide of iron and sulphate of potassa, from which the latter might be extracted with water. Or, to insure an accurate result, the ignited residue might be dissolved in hydrochloric acid, the sesqui- oxide of iron precipitated by ammonia, the solution evaporated, and the residual sulphate of potassa ig- nited and weighed. 128. EXAMINATION FOR ARSENIC IN CASES OF POISONING. When poisoning by arsenic is suspected, the poison must be sought in the contents of the stomach and in- testines, in the substance of these organs even, and in other entire organs, as the liver, spleen, and lungs; an examination must also be made of the vomited matters, and of the surrounding objects, upon which these may have fallen ; the urine and faeces should also be tested for arsenic. The nature of the case will decide in which particular direction the arsenic is to be looked for. It may also sometimes be necessary to examine the remaining portions of suspected food, or the ves- sels, in which the food has been contained, or even the vessel or paper which may have been used to contain the arsenic. When the body has been long interred, and is far advanced in putrefaction, and the wood of the coffin has rotted away, it becomes necessary to test the surrounding earth for arsenic which may have been derived from the body. The chemical investigation must be preceded by a IN CASES OF POISONING. 259 very careful examination of the contents of the stomach and intestines, or of the vomited matters. The sub- stances to be examined are spread out in new and clean porcelain dishes, turned over with perfectly clean glass rods or spatulas, and examined with the help of a lens. The analyst should seek especially for small white hard particles or grains of undissolved arsenious acid, which may be carefully picked out with a pair of pin- cers. These must be looked for especially in the folds of the mucous coat of the stomach and intestines. By stirring up the contents with distilled water, or better, with spirit, and pouring off the lighter organic mat- ters, it is often possible to separate a considerable quantity of the heavy arsenic-powder. In a judicial investigation of this description, the aim of all chemical operations is to obtain the arsenic in its elementary solid state, as the so-called metallic arsenic. In this form alone it is possessed of such highly characteristic properties as to render it impossible to confound it with any other substance, and to allow it to be distinctly recognized even when in almost impon- derable quantities. Moreover, all evidence of its pre- sence is insufficient, unless it can be laid before the tribunal in this form ; and all other forms and states of combination must be considered as affording inconclu- sive testimony as to the existence of arsenic in the substance under examination. This preparation or isolation of arsenic in its metallic state, even in the smallest, almost imponderable quantities, is very sim- ple and easy. Great difficulties, however, present themselves, when it is necessary to extract these traces of arsenic, which are diffused through a whole body, from the great mass of organic matter, and to convert them into some form of combination, from which the arsenic can be extracted in the metallic state. It is most convenient, in considering the process 260 EXAMINATION FOE AKSENIC employed for the chemical examination, to regard three different cases as possible : — I. The arsenious acid is found in the solid state in the contents of the stomach and intestines, or in the vomited matters. II. The poison is intimately and invisibly mixed with, or dissolved in, the contents, &c., and can there- fore no longer be found, or separated by mechanical means, in the solid state. III. The stomach and intestines are empty or no arsenic can be detected in them, since it has already been absorbed into the mass of the blood, or into the substance of the different organs. I. The arsenic is still to be found in the solid state, and may be picked out or separated by levigation from the contents of the stomach, &c.* This case is the easiest of the three, since it is only to be proved that the substance found is really arsenic. This may be known by the grains or particles exhibiting the follow- ing characters, after having been properly freed from organic matter : — 1. The particles are generally milk-white, more rarely clear and semi-transparent, hard, and brittle. 2. A particle of arsenious acid, however small, when introduced into a small tube closed at one end, and heated in the edge of the spirit-flame, volatilizes and recondenses farther up the tube, in the form of a white sublimate which may be seen, especially when exam- ined with a lens, by sunlight, to consist of very lus- trous octohedral crystals. 3. A small fragment placed upon red-hot charcoal, is volatilized, emitting a powerful odor of garlic (on red-hot glass or porcelain it volatilizes without garlic odor, because it is not reduced to the state of metal). * Poisoning sometimes happens from commercial metallic arse- nic (fly-poison, cobalt, &c.)« Brownish-black grains or particles should then be looked for, which are easily recognized as arsenic. IN OASES OF POISONING. 261 4. A particle of the substance is placed in the end of a very narrow tube (Fig. 40), and above it several Fig. 40. splinters of freshly-ignited charcoal so that they may occupy about J inch of the tube. This part of the tube is now held horizontally, in the flame of the spirit- larnp, in such a manner that the spot where the arse- nious acid is placed may remain without the flame. When the charcoal is heated to redness, that portion of the tube is also brought into the flame when the volatilized arsenious acid, passing over the red-hot charcoal, is reduced, and the metallic arsenic deposited beyond the charcoal, in the form of a dark, lustrous, metallic ring. By a gent]e heat, this metallic incrus- tation may be carried still farther up the tube. If the incrustation be chased hither and thither in the tube it is oxidized, or at least partly, and converted into small shining, colorless, volatile crystals of arse- nious acid. If the tube be cut off, just before the part which contains the metallic ring, and the latter then gently heated, the characteristic garlic odor of arsenic may be perceived on approaching the nose to the ori- fice of the tube. 5. This reduction of arsenic to the metallic state may be effected with greater ease and certainty by dissolving a small quantity of the substance in water containing hydrochloric acid, and testing the solution in Marsh's apparatus, in the manner to be presently described more particularly. 6. A particle of the arsenious acid is heated in a small glass tube, closed at one end, with a piece of dry 262 EXAMINATION FOR ARSENIC acetate of potassa about as large as a pin's head, when the indescribably offensive and characteristic odor of kakodyl should be evolved. 7. One or more fragments are finely powdered, under distilled water, the powder rinsed into a small beaker-glass with 20 or 30 drops of water, and the mixture heated nearly to ebullition until the powder is dissolved. A part of this solution is mixed, in a small test-tube, with several drops of solution of nitrate of silver, and afterwards with very dilute ammonia, added drop by drop. In this way, if the substance were arsenious acid, a considerable bright yellow pre- cipitate of arsenite of silver will be produced. — An- other portion of the liquid, mixed with several drops of a clear solution of ammonio-sulphate of copper, gives a fine yellowish- green precipitate of arsenite of copper. A third quantity of the solution, mixed with a few drops of hydrochloric acid, and afterwards with several times its volume of sulphuretted-hydrogen- water, gives a bright yellow precipitate of tersulphide of arsenic, which redissolves perfectly on adding am- monia. Of all these reactions, the reduction to the metallic state in Nos. 4 and 5 is the most necessary, because it is most characteristic and conclusive. The others are to be viewed rather in the light of superfluous confir- mations, and are only employed when a considerable quantity of substance is at the analyst's disposal. II. Arsenic can no longer be perceived by the eye, or mechanically separated, in the solid state, but is contained in a state of solution, or of intimate mixture, in the contents of the stomach, &c. In this case, which is more difficult and of more frequent occur- rence than the preceding, the problem consists in dis- solving and destroying, by appropriate reagents, the whole mass of the organic matter composing the con- tents, the vomited matters, the food, and even the IN CASES OF POISONING. 263 stomach and intestines themselves. This is always necessary before the arsenic can be detected with cer- tainty. It is indispensably necessary that this operation should be preceded by a most careful examination of the reagents to be employed, in order to ascertain whether they contain, as is not unfrequently the case, a small quantity of arsenic. This is equally requisite whether the reagents have been purchased or have been prepared by the analyst himself. The distilled sulphuric acid, the hydrochloric acid, and the zinc must especially be examined. This is most conveni- ently effected in Marsh's apparatus, which will be pre- sently described, and which is invaluable as allowing the reagents, which are employed in it, to be so readily and surely tested. "Without such previous proof of the absence of arsenic in the reagents, upon which the chemist must lay great stress in his depositions, the detection of arsenic in investigations of this descrip- tion cannot be brought forward in evidence, since it might have been derived from the reagents employed. It should farther be observed and stated in evidence, that the investigation was conducted with new utensils and vessels which had not been used before ; and it is advisable, moreover, to insure perfect satisfaction, that it should not be carried out in an ordinary chemical laboratory, or, at all events, that the laboratory should be well cleared before the judicial inquiry is entered upon. If arsenic should be found in an examination con- ducted with all these precautions it is still necessary to reflect that it might occur in the body quite acci- dentally ; especially after the administration of certain medicinal remedies, such as the antimonial compounds, preparations of phosphorus, phosphoric, sulphuric, and hydrochloric acids, which may contain arsenic from carelessness in their preparation. Even the hy- 264 EXAMINATION FOR ARSENIC drated sesquioxide of iron, administered as an antidote in a suspected case of poisoning, might have contained arsenic, unless prepared with great care. Or the arsenic may have been administered as a remedy (especially as a secret medicine). When bodies have been exhumed, it becomes necessary to test the earth with which the coffin has been in contact, since it sometimes happens that soils, especially such as are ferruginous, contain appreciable quantities of arsenic, which might have entered into the body. Various methods are employed for the modification or destruction of the organic matters, with a view to the extraction of the arsenic. 1. When the substance is in the form of a paste, as in the contents of the stomach and in the faeces, chlorine-gas is passed to saturation. The chlorine is prepared by means of sulphuric acid and manganese, which have been previously tested, and is washed by passing through a small but high column of water. In order to assist the action, the mass may, at the same time, be gently heated. Lastly, when it is completely saturated with gas, coagulated, and bleached, the mix- ture is heated nearly to ebullition to expel the excess of chlorine, and the solution, which must contain the arsenic, is filtered through paper free from smalt. 2. The stomach and intestines, with their contents, are cut into fine shreds, placed in a porcelain dish, and the whole mass uniformly mixed. About J is then set aside in a clean covered glass, in case any accident should happen to the remainder. The mass is then treated with a moderately concentrated solution of potassa, and heat applied until it is entirely or almost entirely dissolved. Only a small quantity of potassa is necessary for this purpose, and the potassa should therefore be gradually added to the mixture, so as to avoid an excess, which would interfere with the sub- sequent operations. The solution is afterwards slightly IN CASES OF POISONING. 265 acidified with dilute sulphuric acid, and chlorine-gas is passed, to saturation, into the mass thus coagulated, as in 1. 3. The organic matter cut into shreds, is treated with about as much pure concentrated hydrochloric acid as is equal to the weight of the dry substances contained in the mass ; enough water is then added to form a thin paste. The dish is heated on a water- bath, the contents stirred every five minutes, and about 30 grs. of chlorate of potassa (free from lead) added to the hot liquid until it has become clear yellow, homo- geneous, and limpid. After being heated for some time longer, the solution is strained through a moist- ened filter of white paper, free from smalt, the residue washed upon the filter with hot water till the washings are no longer acid, the whole liquid poured together into a porcelain dish, and evaporated to about 1 pound upon the water-bath. The solution obtajned by one of these methods is poured into a cylindrical glass or into a flask, and a slow stream of sulphuretted hydrogen gas passed into it to complete saturation. All the arsenic is thus pre- cipitated as sulphide, Its precipitation is much pro- moted if the liquid be heated for about half an hour to 50° or 60°, while the gas is passing, and allowed to cool before the stream of gas is discontinued. When saturated, the liquid is allowed to remain for twenty- four hours in a closed vessel. The precipitate which is then deposited has generally, even if much arsenic be present, a dirty, undecided, grayish-brown color.* The greater portion of the solution is poured off, and the precipitate thrown upon the smallest possible filter of Swedish paper; free from smalt, upon which it is _* If lead, copper, mercury, or antimony were present, the preci- pitate would also contain the sulphides of these metals, for which it would have to be particularly examined. 23 266 EXAMINATION FOB ARSENIC well washed. The filtrate, before being thrown away, should, for greater certainty, again be saturated with sulphuretted hydrogen gas and set aside for some time in a closed vessel. This precipitate always contains, in addition to sul- phide of arsenic, certain sulphuretted organic matters which are precipitated with it, and must be completely destroyed; this is best effected in the following man- ner:— The filter containing the precipitate is placed in a somewhat capacious crucible of genuine porcelain, and digested with concentrated nitric acid until the whole is converted into a homogeneous mass. The free ni- tric acid, of which more may be added if necessary, is neutralized with pure carbonate of soda, and the solu- tion carefully evaporated to dryness. It is important that the mass should contain a sufficient quantity of nitrate of soda, which is easily insured. It is gradu- ally heated over a large spirit-lamp, or gas-burner, until the salt fuses ; it blackens at first, but afterwards fuses, quietly and without deflagration, to a clear color- less liquid. The whole of the organic matter is now burnt, and the arsenic converted into arsenate of soda. Pure concentrated sulphuric acid is then gradually dropped upon the cooled saline mass in the crucible, and a gentle heat applied, until, after addition of an excess of acid, the nitric and nitrous acids are com- 2>letely expelled, and the mass is converted into bisul- phate of soda. If nitric acid containing hydrochloric acid had been originally employed for the oxidation of the sulphuretted hydrogen precipitate, a loss of arsenic might now result, from its volatilization as chloride of arsenic. The purity, in this respect, of the nitric acid and carbonate of soda, must therefore have been previously ascertained. The acid saline mass is now dissolved, in the crucible itself, with the smallest quantity of hot water, and the solution introduced into Marsh's apparatus. IN CASES OF POISONING. 267 4. The organic matter is introduced, together with the whole of the liquid, into a capacious tubulated retort, and about an equal weight of rock-salt, or of fused common salt, in small fragments, added. The retort is connected with a tubulated receiver, furnished with a delivery-tube which dips into water. A quan- tity of (tested) sulphuric acid, sufficient to decompose the whole of the chloride of sodium, is then poured upon the mass through a funnel tube passed into the tubulure of the retort. When the intumescence and evolution of hydrochloric acid have ceased, the con- tents of the retort are heated to boiling, the receiver being kept thoroiighly cool. All the arsenic is thus distilled off as chloride, especially towards the last, in proportion as the contents of the retort become more concentrated, on which account the distillation should be carried pretty far. The arsenic is converted into chloride, even when it exists in the mass, in the form of sulphide. The distillate may be at once introduced into Marsh's apparatus. It is safer, since some organic matter might possibly have passed over, to precipitate the arsenic from the solution by sulphuretted hydro- gen, and to treat the precipitate as directed above. In the same way the small quantity of arsenic contained in the water in which the hydrochloric acid was con- densed, may be precipitated. This method seems to be the most simple and sure, to distil the mass directly with concentrated hydrochloric acid, instead of salt and sulphuric acid, and the arsenic passes over as chloride. Marsh's apparatus has the following simple con- struction : a is a two-necked bottle capable of holding £, or at most 1 pint. Both necks are fitted with new perforated corks, which must be perfectly tight. Through one of these, the funnel tube b is passed air- tight, and through the other, the bent tube c, which is expanded at c into a bulb about an inch in diameter. 268 EXAMINATION FOR ARSENIC This bulb serves to collect the particles of liquid which are thrown up from the contents of the bottle, and Fig. 41. which drop down again into the latter, from the ob- liquely cut end of the tube. The other end of this tube is connected, by means of a cork, with the tube d, about 6 inches long, which is filled with fused pure chloride of calcium, free from powder, destined to re- tain the moisture. In the opposite end of the tube d, is fixed, air-tight, another tube e, made of glass free from lead, 12 inches long, and at most J-% inch in in- ternal diameter. It should be made of rather thick glass, and somewhat drawn out at the end. It must be observed that the funnel-tube d is indispensably necessary. If a two-necked bottle cannot be procured, one with a single neck must be provided with a cork bored with two holes. •>._ . A better form of apparatus than the one just de- scribed is shown in Fig. 42, which differs from it in having the large tube filled with asbestus to prevent impurities being carried over mechanically by the cur- rent of gas. Several ounces of granulated zinc are introduced IN CASES OF POISONING. 269 into the bottle, which is then half-filled with distilled water : when the apparatus is all arranged, distilled Fig. 42. concentrated sulphuric acid is added in small portions by the funnel tube b, very gradually, so that the mix- ture may not become too hot, lest sulphuretted hydro- gen should be formed. The evolution of hydrogen is allowed to proceed until it is judged that all atmos- pheric air is expelled, and that the apparatus is per- fectly filled with hydrogen. The narrow delivery-tube is then heated to redness at e, for at least half an hour, by a spirit lamp with a double draught, or a powerful gas-burner, the evolu- tion of hydrogen being constantly maintained by adding acid from time to time. In this way, the acid and zinc are tested for any trace of arsenic which might be present. If they are pure, no incrustation will be deposited at the ignited spot, e. If arsenic be present, a metallic mirror is obtained at this portion of the tube, and the acid and zinc cannot be used ; even the apparatus must then be carefully cleaned, or, better, replaced by a new one. In the same manner any arsenic might be detected in the hydrochloric acid, the chlorate of potassa (after having been com- pletely converted by fusion into chloride of potas- 23* 270 EXAMINATION FOE ARSENIC si urn), the nitre, and the hydrate of potassa (for the third case), which must first be converted into sul- phate by adding sulphuric acid. The quantities em- ployed for testing should not be too small ; at least an ounce of each reagent should be taken. When the reagents have been tested in this manner, and shown to be absolutely free from arsenic, the examination of the substance may be proceeded with. The solution to be tested, containing any arsenic which may have existed in the body, is poured through the funnel tube b into the apparatus filled with hydrogen, and from which hydrogen is being evolved, the tube e being already heated to redness at the same spot. In order that none of the liquid may remain in the tube b, the latter is rinsed with about the same quantity of pure water, care being taken that no air is poured in with it. If arsenic be present, there will soon appear, in the portion of the tube e, beyond the heated spot, a dark stain, which is at first brownish, and afterwards becomes lustrous and gradually increases until, when large quantities of arsenic are present, it forms an opaque metallic mirror. At the same time the gas issuing from the tube e may be kindled, and a dish of white genuine porcelain held in the flame, which should not be too feeble; lustrous black or brownish spots of metallic arsenic will then be deposited, and a great many may sometimes be obtained. When the heated portion of the tube is not very long, more or less arsenetted hydrogen escapes decomposition and fur- nishes the above-mentioned spots. No imitation of porcelain (stone-ware or delf) should be employed for this purpose, since the glaze of these materials very often contains lead, the reduction of which might pro- duce dark spots even though no arsenic were present. If a large quantity of arsenic be contained in the mix- ture, so that many thick arsenic-spots can be obtained, IN CASES OF POISONING. 271 they may be easily recognized by means of the charac- teristic reactions given above, after they have been dissolved in a few drops of nitric acid, and the greater excess of acid has been expelled by a very gentle heat. If only traces of arsenic be present, the spots are so feeble that their nature may remain uncertain. The only indication which is perfectly conclusive, is the production, in the red-hot tube, of a metallic mirror, which must volatilize when gently heated, and re-con- dense upon a cool part of the tube, at the same time imparting to the evolved gas the peculiar garlic odor. When the arsenical mirror no longer increases, and the flame ceases to deposit the spots, the operation is discontinued. It is then very convenient to draw the tube e gently out, while it is still red-hot and soft, and to close it, when the metallic mirror is obtained in a tube, which may be sealed also at the other end, and laid before the authorities. If the analyst have reason to believe that a large quantity of arsenic is present, it is well not to employ the whole quantity of liquid at once, but to divide it into several portions, and to make use of a much lon- ger tube e, so as to obtain the arsenic-mirror in several places. The tube is then cut with a file into as many pieces as there are mirrors of arsenic. That which contains the most characteristic mirror is sealed at both ends and produced in court; the remaining mir- rors are subjected to the tests given at p. 260, among which the ready volatility and alliaceous odor are the most characteristic and decisive. If after heating the tube for one hour, no stain or mirror make its appearance, and no traces of spots have been obtained from the flame, the absence of arsenic may be inferred, provided that proper care has been taken in the former part of the examination, so that the arsenic cannot have been lost through neg- ligence or awkwardness. 272 EXAMINATION FOR ARSENIC It is very important, in connection with this test (Marsh's) to remember that antimony also, whether as teroxide, or as antimonic acid, and especially when in solution in the form of a salt, yields under the same conditions as arsenic, a gaseous antimonetted hydrogen, which deposits upon the heated tube, and upon porce- lain, a mirror and spots very similar to those obtained with arsenic. This fact assumes so much greater im- portance, when it is remembered that preparations of antimony, especially tartar emetic, are administered as internal remedies, so that, in such cases, metallic mir- rors are obtained, similar to those of arsenic, but con- sisting, not of that metal but of antimony. On the other hand, it must not be forgotten that commercial arsenic, as it is employed for poisoning, frequently contains antimony. If the question be merely whether a metallic mirror consist of arsenic or antimony, it may be readily de- cided. The arsenic may be easily recognized by the reactions mentioned above, while the antimony-mirror presents very different characters. The antimony- mirror has a lighter color, and is more lustrous than that of arsenic; the antimony spots are darker and have often a tinge of blue. Antimony is not nearly so easily volatilized as arsenic, and although both mirrors may be chased from one part of the tube to another, there is a great difference in the heat necessary in the two cases. A very striking difference between the two deposits is seen in their behavior when heated ; the mirror of antimony, before volatilizing, fuses into small lustrotfs globules, which may, in all cases, be seen with the aid of a lens; the arsenic, however, exhibits no sign of fusion. The most characteristic distinction is the pro- duction of the garlic odor when the arsenic is volatilized while the antimony passes off in vapor without any perceptible odor. If that portion of the tube which contains the mirror be heated while the hydrogen is IX CASES OF POISONING. 273 still passing, the gas issuing from the orifice of the tube will have a distinct garlic odor if the deposit consist of arsenic, but will be inodorous if antimony only be present. The following reactions may also be applied to distinguish arsenic and antimony. The arsenical spots deposited upon porcelain disap- pear when moistened with a concentrated alkaline solution of hypochlorite of soda ; those of antimony, however, are not affected by this reagent. If the spots consist of arsenic and antimony, the latter not exceed- ing 5 per cent., the spots will also be entirely dissolved. Spots or mirrors of arsenic disappear when moistened with a drop of nitric acid, and gently warmed, forming a clear solution. If a drop of nitrate of silver be added to the solution, and a glass rod moistened with caustic ammonia be held over the liquid, but not allowed to touch it, the mixture assumes a yellow color, from the formation of a precipitate of arsenite of silver. Some- times, if too strong an acid or too great a heat have been applied, the precipitate consists of reddish-brown arsenate of silver. This characteristic color is always produced by nitrate of silver, when the arsenic spots are dissolved by placing the capsule over a vessel containing solution of chloride of lime and sulphuric acid. It is true that spots and mirrors of 'antimony also disappear when treated with nitric acid, the antimony, however, is not dissolved, but merely converted into white oxide, which gives no reaction with solution of nitrate of silver. The antimony dissolves in a mixture of one drop of nitric acid and one drop of hydrochloric acid ; if the greater excess of acid be carefully evapo- rated, and sulphuretted hydrogen-water be dropped upon the residue, a fiery-red precipitate of sulphide of antimony is produced. If the spot had consisted of arsenic, a lemon-yellow precipitate would have been obtained. If the spots be moistened with sulphide of ammonium 274 EXAMINATION FOR ARSENIC and dried at a very gentle heat, the arsenic becomes yellow, the antimony orange. The yellow spots of sulphide of arsenic are not affected by hydrochloric acid, while those of sulphide of antimony disappear on gently heating. If sulphuretted hydrogen gas be passed through the tube containing the metallic mirror, and heat applied, the metal is converted into a sulphide. If the mirror consist of antimony, black, or partly orange-red, sulphide of antimony is produced, while arsenic gives a yellow sulphide. The color, however, is not the only distinc- tion between these compounds, another is afforded by their unequal volatility, sulphide of arsenic being far more volatile than that of antimony. Moreover, antimony, and arsenic, in the form of sul- phides, may be separated by cyanide of potassium, according to the method given in No. 62. The presence of antimony in the precipitated sul- phides may also be ascertained by oxidizing them as directed at p. 266. In that case, the fused mass, before treatment with sulphuric acid, should be dissolved in water, when the antimony would remain undissolved in the form of antimonate of soda. Or the precipitate by sulphuretted hydrogen may be washed with a concentrated solution of carbonate of ammonia, which is poured over it several times. The sulphide of arsenic is dissolved while the sulphide of antimony remains undissolved. If there is a consider- able quantity of the precipitate, a portion may be dissolved in aqua regia, the solution treated with sul- phurous acid to reduce the arsenic acid to arsenious, concentrated by evaporation, a piece of bright copper foil placed in it, and then warmed. Antimony and arsenic are reduced and cover the copper with a steel-colored coating, which is easily removed if the copper is heated with caustic ammonia. It is then easily determined which of the metals is present. If both, they may be IN CASES OF POISONING. 275 separated by heating the substance carefully in a slow current of hydrogen. All the arsenic will be sublimed. If hydrogen gas containing arsenic, is passed into a solution of nitrate of silver contained in a Liebig's bulb tube, it forms a precipitate of metallic silver, and arsenious acid, which is easily found in the liquid. Antimonetted hydrogen forms in a solution of silver, a precipitate of antimonide of silver. If a mixture of arsenetted and antimonetted hydrogen from the Marsh apparatus is conducted into a solution of silver, a mixture of antimonide and metallic silver are precipi: tated. If this precipitate is washed with hot water and then boiled with a concentrated solution of tartaric acid, the antimony alone is dissolved and is then easily recognized by hydrosulphuric acid after acidifying with hydrochloric acid. (See also No. 61.) III. If no arsenic was found in the stomach and intestines, it must be supposed to have been partly carried away in the vomited matters and faeces, and partly absorbed into the mass of the blood, and into those organs which are rich in blood. In this case, the same process is employed as in the preceding, the arsenic being sought, according to the same method, in the liver, spleen, lungs, heart, and kidneys. If urine were found in the bladder, or faecal matter in the large intestines, they should be examined first. The urine must not be introduced at once into Marsh's apparatus since the frothing to which it gives rise would interfere with the progress of the experiment ; the urine should therefore be slightly acidified, with hydrochloric acid, sulphuretted hydrogen passed through it, and the sub- sequent process conducted as in the second case. Investigations of this description are in the highest degree laborious, troublesome, and disgusting, when the body to be examined has been interred for months or years, and has passed into a state putrefaction. In such a case, it is frequently no longer possible to dis- 276 EXAMINATION FOR ARSENIC tinguish or separate individual organs, and the analyst is then necessitated to examine the whole mass of putre- fied organs, or the whole of the soft parts which dry up under some particular local circumstances, and even the bones. When this is the case, the body should not be laid in a bath of chlorine- water or solution of chloride of lime, in order to destroy the offensive odor, since arsenic may thereby be extracted and lost. If chlorine-gas be employed to disinfect the body, it must be evolved by means of distilled sulphuric acid free from arsenic. All the soft parts, especially those which may have formed parts of the abdominal viscera, are carefully separated from the bones, and treated as in the second case. The following is another convenient process to be especially preferred for the treatment of bodies which have been exhumed entire after some months' interment. The entire soft parts are treated in a large dish of genuine porcelain, with moderately strong nitric acid, which has been previously tested for arsenic; the dish is then heated upon a sand-bath, and its contents well stirred, until the organic matters are so far destroyed and dissolved as to form a homogeneous pasty mixture. This is now neutralized with a solution of pure hydrate or carbonate of potassa, and about as much finely- powdered nitre (previously tested) added, as is equal in weight to the soft parts. The whole is now evapo- rated to dryness, with constant stirring, and the dry mass introduced by degrees, in small portions, into a new clean Hessian crucible heated to dull redness. In this manner, the whole of the organic matter is burnt, and the arsenic, if present, converted into arsenate of potassa. In this process, it is important, and not very easy, to add the proper quantity of nitre. If too little nitre be employed, part of the organic matter may . remain unburnt, and arsenic may be volatilized from the carbonaceous mass ; on the other hand, too much IN CASES OF POISONING. 277 nitre would interfere with the subsequent treatment of the mass. It is better to make a preliminary test with a small portion of the mixture, by introducing it into a small red-hot crucible, and observing whether the mass is perfectly white after deflagration. If it be black and carbonaceous, more nitre must be added. The mass, which now consists essentially of carbo- nate, nitrate, and nitrite of potassa, and may also contain arsenate of potassa, is dissolved in the smallest possible quantity of boiling water, and the solution, without filtering off from the suspended phosphate of lime and silica, gradually mixed, in a porcelain dish, with a slight excess of sulphuric acid. The pasty saline mass thus produced is carefully heated till all the nitrous and nitric acids are expelled, a point to which great attention must be paid. On cooling, the mass is stirred up with a little cold water, and the solution poured off from the large deposit of sulphate of potassa. The latter is washed several times with cold water, the washings mixed with the first solution, and the liquid, treated as above, with sulphuretted hydrogen. The pre- cipitate then only requires to be oxidized with nitric acid, with the precaution that the acid must be entirely removed by evaporation before the solution is intro- duced into Marsh's apparatus. It is rarely of importance to the evidence that the weight of arsenic existing in a body should be deter- mined. Such an estimation can only be relative, since it is impossible to extract and weigh the whole of the arsenic contained in all the parts of a body. In such a case, a somewhat longer reduction-tube should be employed, into which is introduced a closely twisted spiral of pure bright copper, about two inches in length ; this spiral is accurately weighed with the tube. The latter is then heated in two places, one nearer the evolution-bottle, for the deposition of a mirror; the other, at some distance, where the strip of copper is 24 278 EXAMINATION FOB PHOSPHORUS. placed, which combines with all the remaining arsenic, forming steel-gray arsenide of copper. The increase of weight of the tube indicates the amount of arsenic, which is calculated as arsenious acid. 129. EXAMINATION FOR PHOSPHORUS IN CASES OF POISONING. Since phosphorus has been used to poison mice, &c., and the poisonous action of friction matches has become extensively known, phosphorus has not ^infrequently been resorted to as an agent for causing death. It is often necessary, therefore, to examine some article of food, or the contents of a stomach, for this substance. It is obvious that, in cases of the kind, his whole attention must be directed to the separation of the phosphorus in ihefree state, or to producing such reac- tions as will enable him to infer the presence of free phosphorus ; since the mere finding of phosphorus in form of phosphates would prove nothing, as phosphates invariably form constituents of animal and vegetable bodies. A. Detection of Unoxidized Phosphorus. I. Test in the first place the suspected matters as to whether free phosphorus is recognizable by its odor or by its luminosity in the dark, exposing, for this pur- pose, the materials to the air, as much as is necessary, by rubbing, stirring, or shaking. II. A portion of the substance is placed, according to the plan of J. Scherer, in a small flask; suspend in it, above the substance, by aid of the loosely fitted cork, a slip of filter paper moistened with neutral solution of nitrate of silver, and warm the whole to 85° to 105° DETECTION OF UNOXIDIZED PHOSPHORUS. 279 Fah. In case the paper is not colored black after some time, unoxidized phosphorus cannot be present, and it is then unnecessary to proceed further by the methods III. and TV. The operator may go on to (VL). If, on the other hand, the paper blackens, this is no certain evidence of the presence of phosphorus, because various substances, viz., hydrosulphuric acid (detectable by means of a slip of paper moistened with solution of lead or terchloride of antimony), formic acid, products of putrefaction, &c., may produce the same result. Proceed then with the substance as directed in III. and IV. III. The luminosity of phosphorus, of all its charac- ters, furnishes the most striking evidence of its presence in the free state. A large sample of the substance is accordingly examined by the following well-proved and admirable method of E. Mitscherlich. Mix the substance under examination with water and some sulphuric acid, and subject the mixture to distillation in a flask, A. (See Fig. 43.) This flask is connected with an evolution-tube b, and the latter again with a glass cooling or condensing tube, c c c, which passes through a perforated cork, a, in the bottom of a cylinder, B, into a glass vessel, C. Cold water runs from D, through a stopcock, into a funnel, i, which extends to the bottom of B ; the warmed water flows off throuh g* Now, if the substance in A contains phosphorus, there will appear, in the dark, in the upper part of the condensing tube at the point r, where the aqueous vapors, distilling over, enter that part of the tube, a strong luminosity, usually a luminous ring. If you take for distillation 5 oz. of a mixture containing only ?!0th of a grain of phosphorus, and accordingly only 1 * Instead of this vertical condenser, an ordinary glass one used for distillation may be substituted. 280 EXAMINATION FOR PHOSPHORUS. part of phosphorus, in 100,000 parts of mixture, you may distil over 3 oz. of it— which will take at least half an hour — without the luminosity ceasing ; Mitscherlich, in one of his experiments, stopped the distillation after Fig. 43. half an hour, allowed the flask to stand uncorked a fortnight, and then recommenced the distillation : the luminosity was as strong as at first. If the fluid contains substances which prevent the luminosity of phosphorus in general, such as ether, alcohol, or oil DETECTION OF UNOXIDIZED PHOSPHORUS. 281 of turpentine, no luminosity is observed so long as these substances continue to distil over. In the case of ether and alcohol, however, this is soon effected, and the luminosity accordingly very speedily makes its appearance ; but it is different with oil of turpentine which exercises a lasting preventive influence upon the manifestation of this reaction. a. After the termination of the process, globules of phosphorus are found at the bottom of the receiver, C. Mitscherlich obtained from 5 oz. of a mixture con- taining ^ grain of phosphorus, so many globules of that body that the one-tenth part of them would have been amply sufficient to demonstrate its presence. In medico-legal investigations these globules should first be washed with alcohol and then weighed. A portion may afterwards be subjected to a confirmatory exami- nation, to make quite sure that they really consist of phosphorus : the remainder, together with a portion of the fluid which shows the luminosity upon distillation, should be sent in with the report. The experiment should be made in a perfectly dark room, best at night. If it is made in the daytime the room should be darkened by aid of curtains or blinds, so that no reflections whatever from the surfaces of the glass vessels or of the fluids moving in them shall oc- casion mistakes. It is advisable, even, especially when very minute traces of phosphorus are searched for, to pass the evolution-tube through a screen, at 5, to pre- vent such reflections being occasioned by the light of the lamp by which the flask is heated. The residue of the distillation is further examined according to (VI.) for phosphorous acid. The distil- late, also, may be tested in the same manner to confirm the presence of phosphorus, or of phosphorous acid arising from its oxidation. IV. Another sample of the substance may be exa- mined, according to experiments made by Neubauer 24* 282 EXAMINATION FOR PHOSPHORUS. and Fresenius, in the following manner. It is brought into a flask with doubly-perforated stopper, water is added, if necessary, and dilute sulphuric acid to aid reaction. Washed carbonic acid gas* is now slowly conducted through the mixture by means of a glass tube passing through the cork and reaching nearly down to the bottom of the flask. From a short tube above the current of gas is led through one or two V-formed tubes which contain neutral solution of ni- trate of silver. When the flask is filled with carbonic acid it is warmed in a water-bath. The experiment is kept up for several hours. If free phosphorus be present, a portion of it volatilizes unoxidized in the stream of carbonic acid, and on passing into the silver- solution produces there an insoluble black precipitate of phosphide of silver, together with phosphoric acid. Since a black insoluble precipitate may be caused by various volatile reducing agents or by hydrosulphuric acid, its appearance is not proof of the presence of phosphorus, though its non-formation demonstrates conclusively that free phosphorus is absent. a. A PRECIPITATE formed in the silver solution in the above experiment is collected on a filter (which has been previously washed with dilute nitric acid and water), and is well washed with water. The phosphide of silver, which may be contained in this precipitate, is detected by the method of Blondlot, improved by Dussard. a, Fig. 44, is an apparatus for evolving hy- drogen ; b is filled with fragments of pumice-stone drenched with concentrated potassa-lye ; c is a common spring clamp ; d a clamp that can be nicely adjusted by means of a screw or wedge ; e is a platinum jet which is kept cool by means of moistened cotton. This platinum jet is essential, since the flame would be colored yellow if burned directly from a glass tube. * The apparatus, Fig. 41, may be conveniently employed. DETECTION OF UNOXIDIZED PHOSPHORUS. 283 At the outset it is needful to test the sulphuric acid and zinc to demonstrate that they yield hydrogen free from phosphuretted hydrogen. For this purpose allow the gas to evolve until air is displaced from the appa- Fig. 44. ratus, then close c until the acid has been forced into/ then close d, open c, and lastly open d, cautiously in- flaming the gas at the jet and properly regulating its issue. If the flame, when examined in a rather dark place, is colorless, exhibits no trace of a green cone in its interior and no emerald-green tinge when a porce- lain dish is depressed into it, the hydrogen is pure. After verifying this result by a second trial, the preci- pitate to be examined is rinsed into/, care being taken that it passes completely into a, and the flame is again observed as before. In case but a minimum of phos- phide of silver be present the green inner cone and 284 EXAMINATION FOR PHOSPHORUS. emerald-green coloration of the flame will be percep- tible. b. The SOLUTION filtered from the silver precipitate, is freed from excess of silver by hydrochloric acid, filtered through a well purified filter, strongly concen- trated in a porcelain capsule, and finally tested for phosphoric acid by means of molybdate of ammonia or magnesia mixture. In this manner we have most plainly detected the phosphorus of a common match mixed with a large quantity of putrefied blood, and in presence of those substances which prevent luminosity in the method of Mitscherlich. V. When enough phosphorus is present to weigh, its estimation is practicable by adopting Scherer's modification of the process of Mitscherlich. The mass, acidified with sulphuric acid, is distilled in an atmos- phere of carbonic acid gas. For this purpose it is best to fit into the cork of the flask in which the mixture is distilled, a second tube through which pure carbonic acid may be transmitted into the distilling apparatus, until it is completely filled, when the stream of gas may be cut off and the process continued as usual. The receiver may consist of a flask with a doubly perforated cork, the opening of which passes over the end of the condensing tube, the other carrying a bent glass tube which is connected with a U tube containing solution of nitrate of silver. When the distillation is finished, globules of phos- phorus are found in the receiver, which, after again establishing a gentle stream of carbonic acid, are united by gently heating and then are washed and weighed as described (III. a.). The solution poured off from the globules is luminous in the dark, when shaken, though not to the same degree as in Mitscherlich1 s process. The phosphorus in this liquid may be deter- mined, after oxidation, by nitric acid or chlorine, as SILICATES. 285 phosphoric acid ; though, only, when the operator is certain that none of the contents of the distilling flask, which usually contain phosphoric acid, have spirted into the condenser. The entire quantity of phospho- rus is obtained by adding to that, thus determined, what exists in the U tube. Its contents are treated with nitric acid, the silver thrown down by hydrochlo- ric acid, filtered through a washed filter, concentrated, precipitated as phosphate of ammonia-magnesia, and weighed as phosphate of magnesia. B. Detection of Phosphorous Acid. VI. In case free phosphorus itself has not been detected by the above methods, it is needful to look for the first product of its oxidation, viz., phosphorous acid. To this end the residue of the distillation (II. a.), or (V.), or also the residue of (IV.) is brought into the apparatus, Fig. 44, and tested as described (IV. a.) as to any green coloration of the evolved hydrogen. If the phosphorous reaction appears, it is sufficient ; other- wise organic matters may have hindered its production. If, therefore, the flame is not colored, the clamp is closed, and a U tube containing neutral solution of nitrate of silver is affixed to the apparatus and the gas is allowed to stream slowly through the silver solution for many hours. In presence of phosphorous acid, phosphide of silver is formed, which is filtered off and examined as directed in (IV. a.). 130. SILICATES.* A few silicates are directly attacked by acids, while others cannot be decomposed by acids, except by the addition of a base, as, for example, lime. * Methods of Sainte-Claire Deville, as given by Messrs. Grandeau and Troost. 286 SILICATES. By modifying the composition of a silicate, it may always be rendered decomposable by an acid. For example, a silicate containing the following elements : Silica, Lime, Alumina, Magnesia, Iron, Potassa, Manganese, Soda. This combination occurs in porphyry, gneiss, and granite. In the first place it is necessary to observe the action of heat upon the silicate, and if there is a loss in weight, to determine its nature, whether it consists of water or fluorine. Fig. 45. In most cases, the water contained in a silicate evaporates at a red heat, and it is only necessary to SILICATES. 287 heat it over a lamp fed by bellows. The water from talcose minerals is only driven off at a white heat. This temperature may be obtained by using the lamp represented in Fig. 43. The apparatus is com- posed of three principal pieces: a bottle A communi- cating with the tube E with the reservoir I of spirits of turpentine or the lamp proper, which communi- cates by the double tube G with an apparatus for the distribution of air forced by the bellows K, which feeds at the same time the tube H.* Generally when minerals lose their volatile matter, only at the temperature attained by the large lamp, it is those containing fluorine, and it is then necessary first to examine the nature of the volatile matter. The calcination is carried on until neither water nor fluorine remains. It should be noticed whether any material is lost in * Fig. 46 shows the interior construction of the lamp. The annular space 0 0 is closed on all parts, above and at the side by Fig. 46. a thick plate ; below by a copper plate raised externally in such a manner as to form a little cup around the lamp in which water is poured. For the management of this lamp we refer to the article by M. H. Deville, Annales de Chimie et de Physique, 3d series, vol. xlvi. 288 SILICATES. the operations of calcination or not. The substance is introduced in small fragments into a weighed cruci- ble, after which the whole is weighed, then placed over a gas lamp for several minutes, in order to eva- porate the water and see if there is any loss indicated by the balance. It is heated -until the weight is constant, and then taken from the smaller lamp and placed over the larger one, Fig. 45 ; at this temperature it may be fused, decrepitated, change its color, all of which should be carefully noted; when it is certain that the mineral does not lose any more in weight we may proceed to the analysis. The silicate is decomposed by the means of lime ;* there should be the least possible amount of it added, still, it is necessary to employ such a quantity that in pulverizing the glass obtained and treating it with acids the silica will take the gelatinous form. To decompose bottle glass it is necessary to add from 10 to 20 per cent, of carbonate of lime, window glass a little more of it. Wollastonite, amphibole, and pyroxenes 35 per cent, of their weight ; feldspar re- quires 55 per cent., and some substances containing a large proportion of alumina and silica, as disthene, require 75 per cent. As a general rule the quantity of lime to be added is in proportion to the amount of silica contained in * [To prepare it, white marble is dissolved in nitric acid, evapo- rated to dryness, ignited in a platinum crucible until the nitrate begins to decompose, and caustic lime is formed on the surface. It is then treated with distilled water and the thick liquid boiled for some time. It is then filtered, and, when cold, an excess of concentrated carbonate of ammonia is added. This is decanted and washed for some time with warm water over a funnel covered with a piece of cotton cloth. If there remains any nitrate of am- mouia in the carbonate of lime, it will form nitrate of lime during the desiccation or at the commencement of the calcination, and the loss of weight which is thus caused in the carbonate will be an error.] SILICATES. 289 the substance to be analyzed ; the maximum should correspond to the pure silica which requires 110 to 112 per cent. When an analysis is to be made the quantity of silica is only known approximately by experiments with the blowpipe. With this uncertainty it is better to use too much lime than too little, but a large excess must not be used, for most silicates contain bases some- what votatile, as potash and soda, which if set free will cause loss. The silicate is ground, passed through a silk sieve ; it is not necessary to carry this sifting very far, at least if the silicate is not very hard or with very great diffi- culty decomposed, in which case it would be better to pulverize it in a small steel crusher than to employ an agate mortar. When the steel crusher or mortar is used, it is necessary to digest the powder obtained in nitric acid, wash with water, and ignite gently to bring the ma- terial to its original purity; when this is done the substance is placed in the crucible and weighed, and the proper amount of carbonate of lime added. The mixture being weighed, it should be mixed as thoroughly as possible with a little strip of platinum. All the dust adhering to the platinum should be brush- ed into the crucible with a small feather, then the feather passed around the interior of the crucible in such a manner as to bring all together at the bottom, and at the same time passed between the crucible and the powder, so as to detect the mixture. During this time the powder has absorbed a little moisture ; the crucible is placed for a moment over the small lamp* and heated to such a temperature that * Ordinary gas lamp without bellows. The lamp with turpen- tine and bellows is termed the larger, and the gas lamp with only bellows attached, the smaller. 25 290 SILICATES. each part of the surface of the matter becomes incan- descent, allowed to cool, again weighed, and a difference is always found, provided the carbonate contains hygro- scopic water. The material being thus prepared, it is heated for fifteen or twenty minutes over the smaller lamp (gas lamp fed by bellows) in such a manner that the car- bonate acts upon the silicate without fusing; after having thus expelled the carbonic acid, the substance is placed over the large lamp, and it is necessary that the glass produced should be well fused, homogeneous, and if it is colored, transparent; all the peculiarities should be observed, and the weight thus produced should be determined. The glass should then be detached from the crucible with the greatest possible care, in such a manner as not to lose any of it, placed in an agate mortar, covered with sheepskin, and ground with care, but not too fine. The pulverized glass is then placed in a weighed pla- tinum crucible, heated to 200° or 800°; and the glass to be analyzed weighed. The glassy material moistened with water is treated with nitric acid, being stirred constantly with a glass rod, so as to prevent the mixture forming a compact mass at the bottom of the crucible. When all that is found upon the glass rod is detached, and it is heated over the lamp to be sure that nothing remains, the crucible is placed upon the sand-bath and heated to such a temperature that no more nitric acid is given off and nitrous vapors begin to form. If the material contains any iron or manganese, it is necessary to wait until the color becomes uniformly red or black, and then there should be added enough of a concentrated solution of nitrate of ammonia to moisten the entire mass, which is heated over the sand-bath, covering the crucible with a funnel ; after a moment it is uncovered and odor observed. If the SILICATES. 291 smell of ammonia is distinctly perceived, the process is continued ; if it is not, a drop of ammonia is added with a glass rod, the mixture stirred, and notice is taken if the smell of ammonia remains and if a pre- cipitate is formed; generally there is no precipitate, and it is then certain that all the alumina has been precipitated by the calcination. It is left to digest on the sand-bath until it is also certain that the nitrate of ammonia has penetrated the whole mass, then a little water is added, and the liquid decanted, to prevent accident, on a filter. Water is again placed in the capsule, boiled, de- canted, and washed a dozen times in order to be sure that the boiling water penetrated the entire mass ; when the decanted liquid leaves no residue if evapo- rated on platinum foil, the washing is discontinued. The material submitted to analysis is then divided into two portions — first, the portion soluble in nitrate of ammonia, and secondly, the insoluble portion left in the capsule. The insoluble portion in the capsule is treated with nitric acid, whic his left to digest slightly heated; nitric acid dissolves the alumina and the peroxide of iron. If manganese is not present, the silica which remains is white; if present, it is black. The silica is washed, and the washings evaporated in a platinum crucible and ignited. The mixture of alumina and oxide of iron is weighed. If the silica contains peroxide of manganese, it is washed with dilute sulphuric acid, adding a crystal of oxalic acid. The oxalic acid decomposes the binoxide of manganese and converts it into peroxide, which dissolves in sulphuric acid; the sulphate of mangan- ese is washed; the sulphate mixed with sulphuric acid in a platinum crucible is heated to 300° to 400°, and the sulphate of manganese weighed ; the silica re- mains in a state of purity after all these treatments 292 SILICATES. and washings, as much in the capsule as upon the fil- ter, which is used for decantations. All these decanta- tibns should be made upon the same filter. The filter is again placed over the silica in the cap- sule, the whole gently dried upon the sand-bath, then moderately calcined, when the silica should become white. The crucible and its cover are placed upon the balance, and quickly weighed. Inasmuch as the crucible cools, the weight that it is necessary to place on the side of the silica to obtain an equilibrium di- minishes more and more, by reason of the cooling of the surrounding air; on the other hand, as this cooling takes place, the silica absorbs the moisture to such an extent that its weight is changed and augmented even so as to be seen. The crucible is then placed again warm upon the balance, the weights taken away from the side where the silica is, until the increase of weight of the silica ceases to be rapid. At the moment the balance is at rest, the weight is noted, which gives the weight of the silica. At this point in the analysis the weight has been found; first of the silica, secondly of the mixture of alumina and iron containing a little manganese. To be sure that the silica is pure, it is dissolved in very dilute hydrofluoric acid ; if quite pure it will leave no perceptible residue, except the ash of the filter. It is evaporated with a little sulphuric acid, and should leave no residue. After having weighed the crucible which contains the material after the ignition of the alumina and iron, the mixture is carefully removed and placed in a small platinum boat, previously weighed in a small corked tube; the boat is heated to redness, and again weighed with its case or tube. The boat is then intro- duced into a platinum or porcelain tube, by aid of a SILICATES. 293 small wire which conducts the boat to the part of the tube, where it should be heated. The tube is then heated to redness and a current of hydrogen passed through it.* When the iron is reduced, the stream of hydrogen is replaced by a current of hydrochloric acid gas, which is continued for an hour or two. Fig. 48 shows the arrangement of this part of the analysis. There may be placed at the extremity of the tube a small flask, in which all volatile materials will condense if any escape from the tube. When the current of hydrochloric acid * Fig. 47 represents a convenient apparatus for hydrogen. Fig. 47. A and B are two bottles of four or five litres capacity, and tuhn lated at the bottom. By means of a rubber tube E they are united in such away as to put them in communication. The mouth of the bottle B is closed by a cork, which is pierced by a glass tube terminated with the stopcock R. The bottle B is filled with frag- ments of glass to the level of the smaller tube, and a larger part of the space above with zinc. The bottle A is filled with water and hydrochloric acid. By opening the stopcock R, the acidulated water passes to the zinc, and the hydrogen is only given off when the gas is used. 25* 294 SILICATES. has passed long enough, which may be known by its producing no more protochloride of iron, it is stopped, the hydrogen again passed to expel the vapor of hy- drochloric acid, and the tube left to cool before taking the boat from it. This is placed again in the case or tube and weighed ; the weight it has gained gives the weight of the alumina. Fig. 48. The separation of the alumina would be complete if the mass was perfectly pure, which is not the case, if the material which comes from the nitrates is not sufficiently washed. In this case, the material which has been treated with nitric acid, then with hydrochloric acid, may contain lime left with^the alumina. The lime is found as chloride of calcium. The alumina is moistened with a small quantity of water, which is decanted, SEPARATION OF THE IRON AND MANGANESE. 295 washed several times, dried, ignited in the boat, and weighed in the glass tube. There should be no change of weight, and a drop of oxalate of ammonia should give no precipitate in the washings if the alumina was pure. In the case of a precipitate a diminution of weight in the alumina would be found at the same time. The alumina is washed, dried, and weighed. The last weight obtained is taken for the definite weight of the alumina, and the difference from the first weight di- vided by two gives the weight of the lime (CaO = 28, CaCl = 56). To verify this weight, all the lime contained in the washings is precipitated by oxalate of ammonia, ignited, weighed, and this gives directly the weight of the lime. To determine by difference the quantity of iron and manganese which exists in the material at the same time with the alumina, we take from the entire quan- tity used for analysis : 1st, the weight of the pure alumina; 2d, the weight of the lime; the difference gives the weight of the mixture of iron and manga- nese. Separation of the Iron and Manganese. If the substance does not contain manganese, or if it is not necessary to determine the manganese sepa- rately, the analysis of the material insoluble in nitrate of ammonia is finished. But if the iron and the man- ganese are to be separated, recourse may be had to the following method : — Into a platinum tube a current of vapor of water, furnished by a retort containing distilled water and a few drops of hydrochloric acid, is passed. This vapor will be condensed in the tube, and will take with it into the flask or globe all the chloride of iron and man- ganese produced by the evaporation. This washing done, the waters are placed in a small crucible, and a few drops of sulphuric acid added, evaporated to 296 ANALYSIS OF MATERIALS dryness, and the sulphates gently calcined until the weight is constant; the mixture of sesquioxide of iron and sulphate of manganese is then weighed, a little water poured upon the sulphate, decanted and washed upon a filter, which is ignited with the peroxide of iron and weighed. This weight is the oxide of iron, which, taken from the weight previously obtained, gives that of the sulphate of manganese. By adding the red oxide of manganese deducted from the weight of the sulphate with the oxide of iron, the exact total weight of manganese and iron is known, which have been calculated by difference at the time when the pure alumina was weighed. This verification dispenses with the direct weight of the sulphate of manganese. If, however, it is deemed desirable to determine it, the sulphate from the washing should be evaporated, and the manganese may be weighed in this form. The preceding operations may be verified in the following manner : — 1st. The alumina should be colored or slightly tinged with gray ; it should be soluble in bisulphate of potassa in large excess. 2d. The oxide of iron, tested with the blowpipe with carbonate of soda in the oxidizing flame, should give no green color. 3d. The sulphate of manganese, treated with the sul- phate of ammonia, a little nitric acid and ammonia, should give no precipitate. Analysis of the Materials soluble in Nitrate of Ammonia. They contain 1st, lime; 2d, magnesia, and sometimes manganese; 3d, potassa, 4th, soda. The liquid contains at first a certain quantity of lime, which has been introduced to decompose the mineral. A quantity of pure crystallized oxalate of SOLUBLE IN NITRATE OF AMMONIA. 297 ammonia should be weighed out, sufficient to precipi- tate more than the quantity of lime present. It suf- fices for this purpose to multiply the weight of the lime by 2J and to place this weight of pure pulverized oxalate in the liquid which is stirred and left to settle. When the liquid is clear, there should be added two or three drops of oxalate of ammonia, and if there is a precipitate, it is certain there was lime in the mate- rial to be analyzed. There is added, successively and in quantities estimated approximately, solid oxalate of ammonia and a few drops of the dissolved oxalate, in such a manner as to be sure to have an excess of oxalate of ammonia and to add the least possible quan- tity of the solution of the oxalate so as not to increase the quantity of the liquid. It is left to settle for eight or ten hours and then decanted upon a filter. All the oxalate of lime is placed on the filter, by washing it little by little with warm water. The precipitate is then dried, ignited a sufficient number of times, and weighed. This determines the weight of the lime. From this weight increased by that which has already been found, the weight of the lime added to decompose the mineral is subtracted. This gives the weight of the lime existing in the original substance. The liquid which remains is evaporated in a platinum capsule, until the fluid is concentrated and syrupy. It contains considerable nitrate of ammonia, a little oxa- late of ammonia, and nitrates of magnesia, manganese, potassa, and soda. It is covered with a glass in such a way as to transform the capsule into a closed vessel, and the saline mixture is heated. The nitrate of am- monia is converted into nitrous oxide, the oxalate is decomposed and volatilized, and there remains in the capsule and on the glass those substances which it is necessary to heat to 300° with the gas or alcohol lamp. 1st, nitrates and subnitrates of magnesia and manga- nese; 2d, nitrate of potassa; 3d, nitrate of soda. 298 ANALYSIS OF MATERIALS A little water is added and a trace of pure tartaric acid, which being evaporated to dryness is disengaged with the vapors of nitric acid. The interior of the capsule will be filled with beautiful crystals of vola- tilized oxalic acid; it is heated to dull redness by covering the capsule in such a way that the carbonic acid may not be burned in the interior. In this ope- ration the oxalic acid has driven off the nitric acid and changed the nitrates into oxalates ; these at a red heat are converted into carbonates, and if by chance a small quantity of nitrate has escaped during the reduc- tion, the carbonic oxide and tartaric acid would have eliminated it, so that there would remain only carbo- nates. Water is now added to the magnesia and manga- nese remaining in the capsules, and the alkaline car- bonates are dissolved. It is decanted upon a very small filter, because it is not necessary to wash the carbonate of magnesia much ; it is remarkably soluble, particularly in cold water, and therefore the washing water should be boiling hot when used. The mixture of carbonate of magnesia and manga- nese is heated to redness and thus converted into magnesia and red oxide. The mixture is weighed in the same capsule in which the evaporation has been made. It is then treated with a boiling concentrated solution of nitrate of ammonia, and heated until no more ammoniacal fumes are given off. It is decanted, and the insoluble material washed, if any exists, and should be of a brown color. The capsule is then heated to redness and weighed. The difference be- tween these two weights gives the magnesia, and what remains in the capsule gives the weight of the manganese, the ammoniacal fluid containing the mag- nesia is placed aside to be examined as directed hereafter. The soluble carbonates of soda and potassa are treated with hydrochloric acid for experiment in a SOLUBLE IN NITRATE OF AMMONIA. 299 glass closed with a stopper. This glass is put in a warm place for ten or twelve hours, so that all evolu- tion of the hydrochloric acid may cease in the liquid ; the stopper is washed, the liquid in the glass evaporated, and the washing waters are also evaporated in a plati- num crucible ; the water and excess of hydrochloric acid are driven off, and a mixture of chloride of potas- sium and sodium is obtained, which always crystallizes in cubes when the chloride of sodium is in excess. Sometimes these chlorides have a slight red color, caused by a small quantity of nitrate left in the car- bonates, but any error is prevented by heating the chlorides to such a temperature as to decompose the chloride of platinum formed. The chlorides become black by the presence of the platinum, but this metal from the vessels does not alter the weight of the chlorides. The alkaline chlorides being weighed, a small quan- tity of water is added, and some chloride of platinum, if there is any potassa. The mixture of chloride of platinum and alkaline salts is evaporated to a syrupy- consistency, and treated with pure alcohol. The resi- due consists of the double chloride of platinum and potassium, and some chloride of sodium. It is dried and calcined in order to reduce the platinum. The chlorides of potassium and sodium are separated by water; the mixture is again ignited and weighed. The material which remained in the crucible is the platinum which proceeds from the double chloride. From the weight obtained we deduct that of the chlo- ride of potassium which it contains; by subtracting from the weight of the alkaline chlorides the weight of the chloride of potassium, the weight of the chloride of sodium is obtained. Having these weights it is easy to determine that of the potassa and soda. The following verifications may then be made : 1st. The lime which has been heated till cessation of loss SOO VOLATILE MATERIALS IN SILICATES. of weight should be soluble in nitrate of ammonia, with no other residue but the ashes of the filter. 2d. By adding ammonia-phosphate of soda to the ammo- niacal solution of magnesia, the bulky precipitate of phosphate of ammonia and magnesia is formed. 3d. The manganese is verified as above stated. 4th. The chlorides of sodium and potassium are evaporated, gently ignited, and when treated with a mixture of alcohol and ether should not give any substance capa- ble of coloring the flame red, which would indicate the presence of lithia. The materials which are decomposed by acids are treated directly in the same manner as those that are rendered decomposable by lime ; but it is necessary to do this in such a manner that the silica is always sepa- rated in a gelatinous mass. If not, it is necessary to ignite it with lime to bring it into this state. Thus our condition is that the substance can be decomposed by acid, producing gelatinous silica. The glass re- sulting from the decomposition of the mineral by lime, • should have for its weight the sum of the weights of the materials used, and the lime added. The difference should be one milligramme, or two milligrammes at most ; it is more frequently nothing. Examination of the volatile materials in silicates. It has been seen at the commencement of the analy- sis of the silicates that it is necessary to heat the sub- stance to a very high temperature to expel the volatile materials. The water is freed at the temperature ob- tained by the small lamp ; but when it is necessary to use the large lamp, the presence of fluorides is indi- cated. The better way to make the presence of water in a mineral evident, is to place the material in a platinum tube, and pass a current of dry gas through the tube VOLATILE MATERIALS IN SILICATES. 301 at a red heat ; a tube containing chloride of calcium is arranged to receive the water. This method is not always adopted, because it is frequently possible to determine other things with the water, but is some- times useful. In case there is only water, as in the zeolite, the ignition and loss of weight indicate the amount of water. When there is any evolution of volatile materials at a high temperature, these are, as stated, fluorides. There are a large number of fluorides, but we shall consider only those which may be expelled by calcina- tion; the fluoride of silicium, the fluoride of boron, and the alkaline fluorides. All the fluosilicates may be decomposed by heat, and all the fluorides, mixed with a sufficient quantity of silica, are changed into fluoride of silicium ; there- fore the fluoride of silicium may be determined at once, and it will be easy to determine the other fluorides. When a substance contains fluoride of silicium in a large quantity, topaz for example, and when it is desir- able to collect and determine this fluoride, the following method may be used : take three platinum crucibles, a large, medium, and small one. In the small one, which has been weighed, the material to be ignited is placed and weighed ; over the small crucible, covered with its lid, the medium crucible is inverted so as to form a cap, and finally the two crucibles thus arranged are placed in the large crucible ; the whole are weighed together in such a way that the weight of the appa- ratus, less that of t]ne topaz, may be ascertained. Then pour between the last two crucibles a certain quantity of carbonate of lime and weigh it. This gives the weight of the apparatus, the topaz, and the carbonate of lime. The whole is heated to a red heat, the carbonate of lime is reduced to quicklime, and it is heated for a long time over the large lamp until the fluoride of 26 302 VOLATILE MATERIALS IN SILICATES. silicium is completely expelled. "When it is certain that the loss of the topaz is terminated, the crucible is taken from the fire and weighed ; there should be no loss except of the carbonic acid of the lime and the water. The quantity of the carbonate of lime being known, and therefore that of carbonic acid, it follows that the loss of weight, that of the carbonic acid being deducted, depends entirely upon the quantity of water which may have passed through the lime without being absorbed. This done, the crucible is slightly inclined, the lime taken out with the greatest care, generally rendered compact and adhering to the crucible by the presence of the fluoride of calcium and the silicate of lime. When a sufficient quantity of lime has been taken out to free the medium crucible, this is withdrawn, and then the interior crucible is free ; it is weighed, and the loss of weight gives the fluoride of silicium which is evolved. It is necessary to prove that this is fluoride of sili- cium. The composition of fluoride of silicium is SiF3; if it .is passed through the lime, it forms SiO2,CaO-h 3CaF, a mixture of fluoride of calcium and silicate of lime, which gives an excess of lime again. It is ne- cessary to take all the substance around the medium crucible into the large crucible and boil it with nitrate of ammonia, which does not decompose the fluoride of calcium and silicate of lime. The quicklime is thus disposed of, and fluoride of calcium and silicate of lime remain in the proportions indicated above Si02CaO-f CaF. The substance treated with sulphuric acid should be completely converted into sulphate of lime and fluoride of silicium. Therefore, after having treated it with nitrate of ammonia and washed it, sulphuric acid is added until no vapors are given off; the sulphate of lime thus formed is treated with boiling water and VOLATILE MATERIALS IN SILICATES. 308 acid until wholly dissolved. This washing is done on a filter, so that the sulphate may be acted upon more readily by the hot water. The residue on the filter is ignited, and should consist of only a very small quan- tity of silica. Fluoride of silicium and fluorine may be in excess, so that it may be possible to suppose an expulsion of free fluorine and fluoride of silicium. But this is not probable, because generally the silica is in excess of the fluorine, and cannot be set free without combining •with the silica ; the topaz containing a large quantity of fluorine, and but little silica, only sets free fluoride of silicium. Admitting, however, that an excess of fluorine may exist, it is at the same time supposed that it contains no water. A sufficient quantity of silica is added so that only fluoride of silicium will be set free, and two estimates are made ; in the first the material alone is determined, and in the second the loss of the substance to which the silica has been added. The difference gives the amount of silicium necessary to neutralize the fluorine, and the quantity of free fluorine existing in the mate- rials is deducted from it. EQUIVALENT WEIGHTS OF THE ELEMENTS. Aluminum Al Antimony Sb Arsenic As Barium Ba Bismuth * Bi Boron . . . B Bromine : •'%• j Br Cadmium Cd Caesium Ca3 Calcium i Ca Carbon C Cerium Ce Chlorine .......... Cl Chromium Cr Cobalt Co Columbium Cb Copper Cu Didymium D Erbium E Fluorine . i F Glucinum G Gold i Au Hydrogen i H Indium ^n Iodine I Iridium „ ' Ir Iron . Fe Lanthanum La H = l. 13.7 122 75 68.5 208 11 80 56 133 20 6 46 . 35.5 26.24 29.5 47 31.7 48 56.3 19 9.3 196.6 1 35.9 127 99 28 46.4 EQUIVALENT WEIGHTS OF THE ELEMENTS. 30'5 Lead .. • - - . Pb H=l. 103.5' Li 7 Magnesium • . Mg 12 Manganese • . • . Mn 27.5 Mercury • .- .- Hg 100 Molybdenum - .- .- Mo 48 Nickel ..-...• Ni Nitrogen . ..... N 14 Osmium Os 996 O 8 Palladium Pd 53.3 Phosphorus - . P 31 Platinum - . . Pt 98.7 Potassium . . . . . . . „ . . K 39.1 Ehodium . . . Eh 52.2 Eubidium .......... Eb 85.4 Euthenium Eu 52.2 Selenium Se 39.7- Silicium ... ... Si 14 Silver ...;... AD- 108 Sodium Na 23 Strontium Sr 43.75* Sulphur S 16 Tantalum ;» . . . . . . . . . Ta 91 Tellurium M ... Te 64 Thallium -* Tl 204 Thorium, Th 115.7- Tin , Sn 59 Titaaium Ti 25 Tungsten W 92 Uranium u 60; y 51 3 Yttrium Y 309 Zinc Zn 326 Zirconium Zr 44.8- 26* EQUIVALENT WEIGHTS OF COMPOUND BODIES. H ( KO, S03, A1203, 1 474.6 \ 3S03-f24HO j Alumina . . ,, . . A1203 78.8 Ammonia . . .... NH3 17 carbonate of . ._ 2NH40, 3C02 118 Ammonium . . . . NH4 18 NH Cl 53.5 NH 0 26 NH4Cl,4PtCl 223.2 Antimonious acid BbO. 153' Arsenate of magnesia-ammonia . 2MgO,NH40,As05+HO 190 Arsenic acid .... As05 115 Arsenious acid .... As03 99 Barium, chloride of . BaCl 104 silicofluoride of . 3BaF, 2SiF3 419.1 Baryta ..... BaO 76.5 carbonate of . BaO, C02 98.6 /•] i miYi •") t P ^^ BaO, CrO 1070 j.zi / .0 Berylla (glucina) . ' . ' . Biborate of soda ; ' . ' •'. Be'203 3 NaO, 2B03-hlOHO 52.2 190.8 Binoxalate of potassa . . . , KO, 2C20,+3UO 146.2 Bismuth, teroxide of . __ . . Bi03 232 Bitartrate of potassa . . • KO, HO T 188.2 Cadmium, oxide of . . * '• ' CdO 64 Calcium, chloride of . CaCl 55.5 Carbonic acid .... CO2 22 Chromate of lead PbO, Cr03 162.4 Chromic acid .... Cr03 50.7 Chromium, sesquioxide of . Cr203 77.4 Cobalt, protoxide of . , , -,_, . CoO 37.5 Copper, protoxide of . . , CuO 39.7 — i suboxide of . * .' * ^ Cu,0 71.4 Cyanide of silver ' ; • . • i AgCy 134 26 Ferrocyanide of potassium » 2KCy, FeCy=KaCfy 184.4 EQUIVALENT WEIGHTS OF COMPOUND BODIES. 307 Ferrocyanide of potassium con- taining water of crystallization Fluoride of calcium Hydrochloric acid Iodide of palladium of potassium Iron, protoxide of sesquioxide of Lead, acetate of chloride of / 2KCy, FeCy-f-3HO ) \ =K2Cfy+3HO } CaF HC1 Pdl KI FeO Fe208 PbO, A-|-3HO PbCl PKO H=-l. 211.4 39 36.5 180.4 166.3 36 80 189.5 139.2 m»7 red oxide of » . Lime _., : . ' . , - ., carbonate of . : • . Magnesia . , ; . . Manganese, peroxide of PbO, Pb203 CaO CaO, C02 MgO MnO, MnO Mil f> • t 342.5 28 50 20 43.6 mo MiiO OK a Mercury, protochloride of . protoxide of . . subchloride of suboxide of Molybdenum, biuoxide of . Molybdic acid .... Nickel, protoxide of . Nitrate of baryta of lead .... HgCl HgO Hg2cr Hg20 Mo02 Mo03 NiO BaO, N05 PbO, N05 "KTl "NTO 135.5 108 285.5 208 62 70 37.6 130.5 165.7 A rrC\ NT> i ^n i of soda .... of strontia Nitric acid .... NaO, N05 SrO, N06 N05 rirv ivrrj 1 /U.I 85 105.8 54 /«o Oxalic acid . . '. . * C203 qtrr) p f\ 36 />q aPhosphate of magnesia 2MgO, P05 OMnf) pf) 111 1 qq crystallization Phosphoric acid 2NaO,HO,POs+24HO P05 KO 358 71 47 2 •• bichromate of KO, 2Cr03 TTO r*n 148.6 /•Q 0 — — — chlorate of • . . chromate of . hydrate of . . ;.:'* Potassium, chloride of . . KO, C106 KO, Cr03 KO, HO KC1 122.7 97.9 56.2 74.7 80S EQUIVALENT WEIGHTS OF COMPOUND BODIES. Potassium, platino-chloride of . Silicic acid .. Silicium, terfluoride of Silver, chloride of oxide of . Soda carbonate of ... carbonate of, containing water of crystallization, . hydrate of . Sodium, chloride of . Stannic acid Strontia ....... Sulphate of ammonia of baryta . .. ^ of copper . of lead of lime .. ., » of potassa .. of protoxide of iron. . of soda . . . of strontia . Sulphide of antimony of arseniq. . of copper, . of lead of mercury of molybdenum. . of silver . ' '.' -- of zinc * Sulphuretted: hydrogen /' • Sulphuric aeid, . . .' « — — r- Ohydrated) Sulphurous^ acid . '. Tin, protoxide of * Titanic acid, ." Tungstic. afiid, . Water . . . ." Zinc,,Qxide of . KC1, PtCl2 SiO, SiF, AgCl AgO NaO NaO,CQ2 NaO, COo-flOHO, NaO, HO NaCl. Su02 SrO/ NH40, S034-H0 BaO, S03 CuO,S03-h5HO. PbO, S03 CaO, S03 KO, S03 FeO, S034-7HO ' NaO, SO SrO, S03 SbS3 AsS3 CuS PbS HgS MoS2 AgS, ZnS HS S03 BP, S0ff SnO' Ti02 W08 HO ZuO , ERR ATU,M.t Page 287, 4th line from top for Fig. 43 r^/Big. 45. INDEX. Acid, arsenic, 224 arsenious, 224 boracic, 221 carbonic, 217, 227 columbic, 176 hydrocyanic, 255 molybdic, 181, 185 nitric, 221, 225 phosphoric, 223, 226 phosphorous, detection, 285 silicic, 221, 226, 227 sulphuric, 222, 226 tantalic, 177 tartaric, 80, 81 titanic, 171, 172, 173, 176 tungstic, 178 vanadic, 185, 187 Alkalies, 16, 227 and magnesia, 25 Alkalimetry, 240 Alkaline earths, 31 Alum, 33 iron-ammonia, 34 Alumina, 33, 228 and baryta, 33 and chromium sesquioxide, 35 and fluorine, 153 and glucina, 151 and iron sesquioxide, 38 and magnesia, 37 and phosphoric acid, 37 and potash, 148 chrome-alum, 34 phosphates of, 36 Aluminum with iron, 203 Amalgams, 70 Ammonia, 225 and magnesia phosphate, 23 Ammonia — and soda phosphate, 22 estimation, 18, 23 nitrate of, 296 and soda sulphate, 18 Amphibole, 150 Analysis of nitre, 252 volumetric, 50, 52 Antimony, 224 and arsenic, 88 and tin, 90 and potassa tartrate, 80 and copper, 82 and iron, 84 and lead, 80, 83 and silver, 84 and tin, 87 chloride, 95 estimation, 80 sulphide, 81 Apatite, 29 Aqua amygdalarum amararum, 255 laurocerasi, 255 Argentan, 97 Arsenic, 95, 227 and antimony, 88 and arsenious acid, 224 and cobalt, 104 and iron, 202 and lead, 77 and nickel, 98 and tin, 78 antimony, and tin, 90 chloride, 95 poisoning by, 258 sulphide, 91 with iron, 202 310 INDEX. Ashes of plants, 228 of seeds, 229 Ash of refining hearth, 205 Assay of iron, 50, 52 silver, 67 Barite, 31 Baryta and alumina, 33 and strontia separation, 33 estimation, 31 Bell metal, 72 Berthierite, 84 Beryl, 151 Bismuth and copper, 76 lead and tin, 74 Bitter spar, 27 Black cobalt ore, 107 Bleaching powder, 2;5Q Blende, 55 pitch, 195 Blondlot, plan to detect phos- phorus, 282 Blue vitriol, 53 Bog iron-ore, 49. Bone-ash, 27 Boracic acid, 14£, 221 Bournonite, 82 Brass, 58 Bromide of sodium, 212 Bromine, 222 Bronze, 72 Brown iron ore, 185 Cadmium and copper, 60 . > and zinc, 60 Calcium with iron, 203 Carbon estimation, 200 Carbonate of lead, 62. of potassa and magnesia, 21 of soda, 223 of ainc, 57 Carbonates in water, 220 Carbonic acid estimation, 21, 27, 217, 227 Cast-iron, 200 Celestite, 31 Cements, 211 Cerite, 158 Cerium oxide, 160 Chalcopyrite, 53 Chloride of lime valuation, 2501 of lithium, 170 of silver, 14 of sodium, 13, 212, 214, of tantalum, 178 of thorium, 168 of zirconium, 157 Chlorides of mercury, antimony, and arsenic, 95 of potassium, sodium, and magnesium, 25 Chlorimetry, 250 Chlorine, 222, 226 and bromine, 222 estimation, 14 Chrome-alum, 34 iron-ore, 187 yellow, 189 Chromic acid and lead, 189 Chromite, 187 Chromium estimatiop, 65. with iron, 204 Chrysolite, 144 Cinnabar, 72 Clausthalite, 198 Clay, 210 Cobalt and arsenic, 104 and manganese, 1,07 and iron, 106 ores, black, 107 speiss, 104 with iron, 204 Cobaltite, 104 Coins, gold and copper, 68 Coin, silver, 66 Columbic acid, 176 Columbite, 176 Common limestone, 211 salt, 214 Compounds, equivalent weights. of, 306 Copper, 203, 224, 227 amalgam, 70 and antimony, 82 and arsenic, 76 and bismuth, 76, INDEX. 311 Copper — and cadmium, 60 and gold, 68 and iron, 54 and lead, 82 and tin, 72 and silver, 66 and zinc, 69 estimation, 53 nickel, and zinc, 97 sulphate, 63 sulphide, 53, 82 with iron, 203 Cryolite, 155 Datolite, 145 Detection of unoxidized phospho- rus, 278 Didymium oxide, 160 Dolomite, 27 Dussard, plan to detect phospho- rus, 282 Earthy ore of cobalt, 107 Elements, equivalent weights of, 304 Epidote, 150 Epsom salt, 21 Erbia, 167 Equivalent weights of elements, 304 weights of compound bodies, 306 Examination of volatile matters in silicates, 300 Feldspar, 147 Ferrocyanide of potassium, 257 Fluorine, 153, 224 and alumina, 153 and lime, 154 and sodium, 155 estimation, 30 Fluorite, 154 Gadolinite, 164 Galenite, 61 Garnet, 150 German silver, 97 Glass, 209 Glauber's-salt, 21 Glaucina and alumina, 151 Glucina, 151 preparation, 162 Gold and copper, 68 and silver, 69 coins, 68 Graminacese, 232 Green, schweinfurt, 76 Guano, 232 Gun-metal, 72 Gunpowder, 254 Gypsum, 81 Hematite, 42 Hydraulic limestone, 211 Hydrocyanic acid, 255 Hydrogen purification, 42 sulphuretted, 219 Idocrase, 150 Ilvaite, 143 Incrustations from salt-pans, 215 Indium, 133 combinations of, 136 preparation of, 136 properties of, 136 purification of, 135 separation of, 1 34 Iodide of sodium, 212 Iodine, 222 Iridium, 112, 133 combinations, 137 preparation, 136 separation, 134 Iridosmine, 118 Iron-ammonia-alum, 34 and antimony, 84 and cobalt, 106 and copper, 54 and magnesia, 144 and manganese, 47 and titanium, 172, 174 assay, 50, 52 cast, 200 estimation, 49 812 INDEX. Iron — meteoric, 109 nickel and cobalt, 110 ore, bog, 49 brown, 185 chrome, 187 sesquioxide and alumina, 38 and phosphoric acid, 41 and protoxide, 44 titanic, 172 zinc and manganese, oxides, 59 Lanthanum oxide, 160 Lead and antimony, 80, 83 and arsenic, 77 and chromic acid, 189 and copper, 82 and silver, 65 and tin, 73 and vanadic acid, 188 bismuth, and tin, 74 carbonate of, 62 estimation, 62 molybdate of, 181 phosphate of, 83 selenide of, 198 vanadate, 187 white, 62 Lime, 223 and fluorine, 154 chloride of, 250 estimation, 27, 31 oxalate and phosphate of, 238 sulphate of, 31 Limestone, 211 Limonite, 42 Lithia, 169 Lithium, chloride, 170 Magnesia, 223 and alkalies, 25 and alumina, 37 and ammonia phosphate, 23 and iron, 144 and lime, 27 and lithia, 169 and manganese, 46 Magnesia — and phosphate of ammonia, 23 and potassa, sulphate, 19 and sesquioxide of iron, 46 estimation, 19, 25, 28 carbonate of potassa and, 21 sulphate of, 21 of potassa and, 19 Magnesium, chloride of, 25 with iron, 203 Magnetite, 44 Manganese and iron, 47, 179, 203 and lime, 46 and magnesia, 46 and zinc, 59 cobalt or nickel, 107 ore, valuation of, 248 with iron, 203 Marl, 211 Marsh's test for arsenic, 272 Materials soluble in nitrate of ammonia, 296 Menaccanite, 172 Mercury, 70 and copper, 70 chloride, 95 oxide of, with oxide of lead, 72 protoxide, 72 Meteoric iron, 109 Microcosmic salt, 22 Mineral waters, 216 Minium, 72 Mitscherlich's plan to detect phos- phorus, 278 Molybdate of lead, 181 Molybdenite, 184 Molybdenum with iron, 204 Molybdic acid, 183, 208 Natrolite, 141 Neubauer and Fresenius, plan to detect phosphorus, 282 Niccolite, 98 Nickel, and arsenic, 98 and cobalt, 99 and copper, 97 INDEX. 313 Nickel— and iron, 204 and zinc, 97 cobalt and iron, 99 pure preparation, 98 speiss, 98 with iron, 204 Niobite, 176 Nitrate of ammonia, 296 Nitre, analysis of, 252 Nitric acid, 221, 225 Olivine, 144 Ores, black cobalt, 107 brown iron, 185 chrome iron, 187 manganese, 248 platinum, 111, 114 red silver, 84 tellurium, 138 Organic matters in soil, 225 Orthoclase, 147 Osmium, 113 Oxalate and phosphate of lime, 238 Oxide of cerium, 159, 160 of didymium, 160 of lanthanum, 160 Oxides of manganese, iron, and zinc, 59 of thallium, 129 Oxygen estimation, 42, 53 Palladium, 111 Permanganate of potash prepara- tion, 50 Pewter, 73 Phosphate and oxalate of lime, 238 of alumina, 36 of magnesia and ammonia, 23 of soda and ammonia, 22 Phosphoric acid, 223, 226 and alumina, 37 and arsenic acid, 63 and magnesia, 24 and oxide of lead, 63 and sesquioxide of iron, 41 27 Phosphoric acid — estimation, 23 separation from bases, 29 Phosphorous acid, detection, 285 Phosphorus, poisoning by, 288 with iron, 202 Pitch-blende, 195 Plant ashes, 228 Platinum metals and ore, 111, 114 residues, 121 Poisoning with arsenic, 258 poisoning with phosphorus, 278 Potash and alumina, 148 Potashes, 247 Potash permanganate, 50 Potassa, 222, 226 and antimony, tartrate, 80 and magnesia, carbonate, 21 sulphate, 19 and soda, tartrate, 16 Potassium, chloride of, 25 ferrocyanide, 257 Powders, bleaching, 250 Proustite, 86 Pyrargyrite, 84 Pyromorphite, 63 Pyroxene, 150 Red silver-ore, 84 Rhodium, 112 Rochelle-salt, 16 Ruthenium, 113 Rutile, 175 Saline springs, 216 Salt pans, incrustations from, 215 Scheelite, 181 Scherer's plan to detect phospho- rus, 278 Schreibersite, 109 Schweinfurt green, 76 Selenium and selenides, 195, 198 soot, 197 Seeds, ashes of, 229 Seignette salt, 1 6 Selenide of lead, 198 314 INDEX. Siderite, 46 Silicates, 150, 209, 285 volatile matters in, 300 Silicic acid, 142, 221, 226, 227 Silicon with iron, 201 Silver and antimony, 84 and arsenic, 84 and copper, 66 and gold, 69 and lead, 65 and mercury, 71 assay, 67 chloride, 14 coin, 66 ore, red, 84 pure preparation, 67 Slags, 205 Smithsonite, 57 Smaltite, 103 Soda, 222, 226, 247 and ammonia, 18 carbonate of, 223 phosphate, 22 sulphate, 18 and lime, 147 and potassa estimation, 16 tartrate, 16 estimation, 14 sulphate, 15 Sodium, chloride, 13 iodide, bromide, and chloride, 212 potassium, and magnesium chlorides, 25 Sodium and fluorine, 155 Soft solder, 73 Soils, 224 Solder, 73 Soot, selenium, 197 Spathic iron, 46 Specular iron ore, 42 Speiss cobalt, 103 nickel, 98 Sphalerite, 55 Sphene, 171 Spinel, 37 Springs, saline, 216 Strontia, 223 Strontia — and baryta estimation, 33 and lime, 31 estimation, 31 Sulphate of baryta, 31 of copper, 53 of lime, 31 of potassa and magnesia, 19 of soda, 15 and ammonia, 18 of Strontia, 31 of thoria, 168 Sulphide of antimony, 81 of arsenic, 91 of copper, 53, 82 . of lead, 61 of zinc, 55 Sulphur and iron, 204 estimation, 63, 81, 83, 95 Sulphuretted hydrogen, 219 Sulphuric acid, 222, 226, 227 Tantalic acid, 176, 177 Tantalite, 177 Tantalium chloride, 178 Tartar emetic, 80 Tartaric acid estimation, 80, 81 Tartrate of antimony and potassa, 80 of soda and potassa, 16 Tellurium and bismuth, 140 ore, 138 Tetradymite, 140 Tetrahedrite, 91 Thallium, 126 detection, 129 estimation, 130 estimation volumetric, 132 Thomsonite, 141 Thoria, sulphate, 168 Thorite and thoria, 167 Thorium, chloride, 168 Tin, 73 amalgam of, 71 and antimony, 87 and arsenic, 78 and copper, 72 and lead, 73 INDEX. 315 Tin— arsenic, and antimony, 90 bismuth, and lead, 74 Titanic acid, 171, 172, 173 iron, 172 Titanite, 171 Titanium and iron, 172, 174 Topaz, 153 Triphylite, 168 Tungstic acid, 179, 181 and lime, 181 Type metal, 80 Ulexite, 146 Uraninite, 192 Uranium oxide, 192 Vanadate of lead, 187 Vanadic acid, 185, 187 Vanadinite, 187 Valuation of manganese ores, 248 of soda, 247 Vanadium, 185 with iron, 204 Vegetable ashes, 231 Vitriol, blue, 53 Volatile matters in silicates, 300 Volumetric analysis, 50, 52 Water estimation, 15, 216, 225 Wavellite, 36 Weights of compounds, equiva- lent, 306 of elements, equivalent, 304 Well waters, 216 Wet assay of iron, 50 White lead, 62 Widmannstatten'a figures, 109 Wolframite, 178 Wood ashes, 231 Wulfenite, 181 Yellow chrome, 189 Yttria, 165 and erbia separation, '166 Zinc blende, 55 and cadmium, 60 ' . and copper, 59 • and iron, 64 and nickel, 97 carbonate, 57 iron and manganese, 59 sulphates of iron, copper, and, 58 sulphide, 55 Zinkenite, 83 Zircon, 156 Zirconia, 156 and iron, 157 and silver, 157 Zirconium chloride, 157 THE END. CATALOGUE OF PRACTICAL AND SCIENTIFIC BOOKS, PUBLISHED BY HENRY CAREY BAIRD, INDUSTRIAL PUBLISHER, TsTo- 4O6 •W-A^LnXTTTT STREET, PHILADELPHIA. iHf3 Any of the Books comprised in this Catalogue will be sent by mail, free of postage, at the publication price. This Catalogue will be sent, free of postage, to any one who will furnish the publisher with his address. A RMENGAUD, AMOUROUX, AND JOHNSON.— THE PRACTICAL •^ DRAUGHTSMAN'S BOOK OF INDUSTRIAL DESIGN, AND MACHINIST'S AND ENGINEER'S DRAWING COMPANION: Forming a complete course of Mechanical Engineering and Architectural Drawing. From the French of M. Armengaud the elder, Prof, of Design in the Conservatoire of Arts and Industry, Paris, and MM. Armengaud the younger and Araou- roux, Civil Engineers. Rewritten and arranged, with addi- tional matter and plates, selections from and examples of the most useful and generally employed mechanism of the day. By WILLIAM JOHNSON, Assoc. Inst. C. E., Editor of "The Practical Mechanic's Journal." Illustrated by 60 folio steel plates and 50 wood-cuts. A new edition, 4to. . $10 00 A RROWSMITH.— PAPER-HANGER'S COMPANION : A Treatise in which the Practical Operations of the Trade are Systematically laid down: with Copious Directions Prepara- tory to Papering ; Preventives against the Effect of Damp on Walls; the Various Cements and Pastes adapted to the Seve- ral Purposes of the Trade ; Observations and Directions for the Panelling and Ornamenting of Rooms, &c. By JAMES AKKOWSMITH, Author of "Analysis of Drapery," &c. 12mo., cloth * ... $1 25 HENRY CAREY BAIRD'S CATALOGUE. •DflJRD.— THE AMERICAN COTTON SPINNER, AND MANA- •° GER'S AND CARDER'S GUIDE : A Practical Treatise on Cotton Spinning ; giving the Dimen- sions and Speed of Machinery, Draught and Twist Calcula- tions, etc. ; with notices of recent Improvements : together with Rules and Examples for making changes in the sizes and numbers of Roving and Yarn. Compiled from the papers of the late ROBERT H. BAIKD. 12mo. . . . $1 50 •pAKER.— LONG-SPAN RAILWAY BRIDGES : Comprising Investigations of the Comparative Theoretical and Practical Advantages of the various Adopted or Proposed Type Systems of Construction; with numerous Formulae and Ta- bles. By B. Baker. 12mo. . . . . $2 00 TDAKEWELL.— A MANUAL OF ELECTRICITY— PRACTICAL AND -° THEORETICAL : By F. C. BAKEWELL, Inventor of the Copying Telegraph. Se* cond Edition. Revised and enlarged. Illustrated by nume- rous engravings. 12mo. Cloth . . . . $2 00 "DEANS.— A TREATISE ON RAILROAD CURVES AND THE LO- ° CATION OF RAILROADS : By E. W. BEANS, C. E. 12mo. (In press.) •pLENKARN.— PRACTICAL SPECIFICATIONS OF WORKS EXE- •° CUTED IN ARCHITECTURE, CIVIL AND MECHANICAL ENGINEERING, AND IN ROAD MAKING AND SEWER- ING: To which are added a series of practically useful Agreements and Reports. By JOHN BLENKABN. Illustrated by fifteen large folding plates. 8vo $9 00 •pLINN.— A PRACTICAL WORKSHOP COMPANION FOR TIN, D SHEET-IRON, AND COPPER-PLATE WORKERS : Containing Rules for Describing various kinds of Patterns used by Tin, Sheet-iron, and Copper-plate Workers ; Practical Geometry; Mensuration of Surfaces and Solids; Tables of the Weight of Metals, Lead Pipe, etc. ; Tables of Areas and Cir- cumferences of Circles ; Japans, Varnishes, Lackers, Cements, Compositions, etc. etc. By LEKOT J. BLTNN, Master Me- chanic. With over One Hundred Illustrations. 12mo. $250 B HENRY CAREY BAIRD'S CATALOGUE. 3 OOTH.— MARBLE WORKER'S MANUAL: Containing Practical Information respecting Marbles in gene- ral, their Cutting, Working, and Polishing ; Veneering of Marble ; Mosaics ; Composition and Use of Artificial Marble, Stuccos, Cements, Receipts, Secrets, etc. etc. Translated from the French by M. L. BOOTH. With an Appendix con- cerning American Marbles. 12mo., cloth. . . $1 50 DOOTH AND MORFIT.— THE ENCYCLOPEDIA OF CHEMISTRY, 13 PRACTICAL AND THEORETICAL : Embracing its application to the Arts, Metallurgy, Mineralogy, Geology, Medicine, and Pharmacy. By JAMES C. BOOTH, Melter and Refiner in the United States Mint, Professor of Applied Chemistry in the Franklin Institute, etc., assisted by CAMPBELL MORFIT, author of "Chemical Manipulations," etc. Seventh edition. Complete in one volume, royal 8vo., 978 pages, with numerous wood-cuts and other illustrations. $5 00 DOWDITCH.— ANALYSIS, TECHNICAL VALUATION, PURIFI- D CATION, AND USE OF COAL GAS : By Rev. W. R. BOWDITCH. Illustrated with, wood engrav- ings. 8vo $6 50 -D OX.— PRACTICAL HYDRAULICS: A Series of Rules and Tables for the use of Engineers, etc. By THOMAS Box. 12mo. . . . . . $2 00 •DUCKM ASTER.— THE ELEMENTS OF MECHANICAL PHYSICS : By J. C. BUCKMASTER, late Student in the Government School of Mines ; Certified Teacher of Science by the Department of Science and Art ; Examiner in Chemistry and Physics in the Royal College of Preceptors ; and late Lecturer in Chemistry and Physics of the Royal Polytechnic Institute. Illustrated with numerous engravings. In one vol. 12mo. . $1 50 BULLOCK.— THE AMERICAN COTTAGE BUILDER : A Series of Designs, Plans, and Specifications, from $200 to to $20,000 for Homes for the People ; together with Warm- ing, Ventilation, Drainage, Painting, and Landscape Garden- ing. By JOHN BULLOCK, Architect, Civil Engineer, Mechani- cian, and Editor of "The Rudiments of Architecture and Building," etc. Illustrated by 75 engravings. In one vol. 8ro $3 59 HENRY CAREY BAIRD'S CATALOGUE. DTJLLOCK. — THE RUDIMENTS OF ARCHITECTURE AND BUILDING : For the use of Architects, Builders, Draughtsmen, Machin- ists, Engineers, and Mechanics. Edited by JOHN BULLOCK, author of "The American Cottage Builder." Illustrated by 250 engravings. In one volume 8vo. . . . $3 50 T>URGH.— PRACTICAL ILLUSTRATIONS OF LAND AND MA- a RINE ENGINES : Showing in detail the Modern Improvements of High and Low Pressure, Surface Condensation, and Super-heating, together with Land and Marine Boilers. By N. P. BURGH, Engineer. Illustrated by twenty plates, double elephant folio, with text. $21 00 BURGH.— PRACTICAL RULES FOR THE PROPORTIONS OF U MODERN ENGINES AND BOILERS FOR LAND AND MA- RINE PURPOSES. By N. P. BURGH, Engineer. 12mo. . . . $2 00 •DURGH.— THE SLIDE-VALVE PRACTICALLY CONSIDERED : By N. P. BURGH, author of " A Treatise on Sugar Machinery," "Practical Illustrations of Land and Marine Engines," "A Pocket-Book of Practical Rules for Designing Land and Ma- rine Engines, Boilers," etc. etc. etc. Completely illustrated. 12mo $2 00 •pYRN.— THE COMPLETE PRACTICAL BREWER : Or, Plain, Accurate, and Thorough Instructions in the Art of Brewing Beer, Ale, Porter, including the Process of making Bavarian Beer, all the Small Beers, such as Root-beer, Ginger- pop, Sarsaparilla-beer, Mead, Spruce beer, etc. etc. Adapted to the use of Public Brewers and Private Families. By M. LA FAYETTE BTRN, M. D. With illustrations. 12mo. $1 25 TDYRJT.— THE COMPLETE PRACTICAL DISTILLER : Comprising the most perfect and exact Theoretical and Prac- tical Description of the Art of Distillation and Rectification ; including all of the most recent improvements in distilling apparatus ; instructions for preparing spirits from the nume- rous vegetables, fruits, etc. ; directions for the distillation and preparation of all kinds of brandies and other spirits, spiritu- ous and other compounds, etc. etc. ; all of which is so simpli- fied that it is adapted not only to the use of extensive distil- lers, but for every farmer, or others who may wish to engage in the art of distilling By M. LA FAYETTE BYRN, M. D. With numerous engravings. In one volume, 12mo. $1 50 HENRY CA11EY BAIRD'S CATALOGUE DYENE.— POCKET BOOK. FOE EAILROAD AND CIVIL ENGI- U NEEES : Containing New, Exact, and Concise Methods for Laying out Railroad Curves, Switches, Frog Angles and Crossings; the Staking out of work; Levelling; the Calculation of Cut- tings; Embankments; Earth-work, etc.' By OLIVER BYRNE. Illustrated, 18mo,, full bound $1 75 DYENE.— THE HANDBOOK FOE THE AETISAN, MECHANIC, AND ENGINEEE : By OLIVER BYRNE. Illustrated by 185 Wood Engravings. Svo. $5 00 TjYENE.— THE ESSENTIAL ELEMENTS OF PEACTICAL ME- •^ CHANICS: For Engineering Students, based on the Principle of Work. By OLIVER BYRNE. Illustrated by Numerous Wood Engrav- ings, 12mo. $3 63 •DYENE.— THE PEACTICAL METAL-WOEKEE'S ASSISTANT: Comprising Metallurgic Chemistry ; the Arts of Working all Metals and Alloys; Forging of Iron and Steel; Hardening and Tempering ; Melting and Mixing ; Casting and Founding ; Works in Sheet Metal ; the Processes Dependent on the Ductility of the Metals ; Soldering ; and the most Improved Processes and Tools employed by Metal-Workers. With the Application of the Art of Electro-Metallurgy to Manufactu- ring Processes ; collected from Original Sources, and from the Works of Holtzapffel, Bergeron, Leupold, Plumier, Napier, and others. By OLIVER BYRNE. A New, Revised, and improved Edition, with Additions by John Scoffern, M. B , William Clay, Wm. Fairbairn, F. R. S., and James Napier. With Five Hun- dred and Ninety-two Engravings ; Illustrating every Branch of the Subject In one volume, Svo. 652 pages . $7 00 •nYENE.— THE PEACTICAL MODEL CALCITLATOE: For the Engineer, Mechanic, Manufacturer of Engine Work, Naval Architect, Miner, and Millwright. By OLIVER BYRNE. 1 volume, 8vo., nearly 600 pages . . . . $4 50 •DEMEOSE.— MANUAL OF WOOD CAEVING : With Practical II- lusttations for Learners of the Art, and Original and Selected de- signs. By WILLIAM BEMROSE, Jr. With an Introduction by LLEWELLYN JEWITT, F. S. A., etc. With 128 Illustrations. 4to., cloth $3 00 HENRY CAREY BAIRD'S CATALOGUE. TDAIRD.— PROTECTION OF HOME LABOR AND HOME PRO- B DUCTIONS NECESSARY TO THE PROSPERITY OF THE AMERICAN FARMER : By HENRY CAREY BAIRD. 8vo., paper . 10 •DAIRD.— STANDARD WAGES COMPUTING TABLES: An Improvement in all former Methods of Computation, so ar- ranged that wages for days, hours, or fractions of hours, at a spe- cified rate per day or hour, may be ascertained at a glance. By T. SPANGLER BAIRD. Oblong folio $5 00 B B ISHOP.— A HISTORY OF AMERICAN MANUFACTURES: From 1608 to 1866 : exhibiting the Origin and Growth of the Prin- cipal Mechanic Arts and Manufactures, from the Earliest Colonial Period to the Present Time ; with a Notice of the Important In- ventions, Tariffs, and the Results of each Decennial Census. By J. LEAXDER BISHOP, M. D. ; to which are added Notes on the Principal Manufacturing Centres and Remarkable Manufactories. By EDWARD YOUNG and EDWIN T. FREEDLEY. In three vols. 8vo $10 00 OX.— A PRACTICAL TREATISE ON HEAT AS APPLIED TO THE USEFUL ARTS : For the use of Engineers, Architects, etc. By THOMAS Box, au- thor of "Practical Hydraulics." Illustrated by 14 plates, con- taining 114 figures. 12mo $4 25 HABINET MAKER'S ALBUM OF FURNITURE : Comprising a Collection of Designs for the Newest and Most Elegant Styles of Furniture. Illustrated by Forty-eight Large and Beautifully Engraved Plates. In one volume, cblong $5 00 APMAN.— A TREATISE ON ROPE-MAKING : As practised in private and public Rope-yards, with a Description of the Manufacture, Rules, Tables of Weights, etc., adapted to the Trade ; Shipping, Mining, Railways, Builders, etc. By ROBERT CHAPMAN. 24mo •>»'... • $150 pALVERT.— LECTURES ON COAL-TAR COLORS AND ON RE- U CENT IMPROVEMENTS AND PROGRESS IN DYEING AND CALICO PRINTING. Embodying Copious Notes taken at the last London International Exhibition, and Illustrated with Numerous Patterns of Aniline and other Colors. By F. GRACE CALVERT, F. R. S., F. C. S. 8vo., cloth $1 50 CH HENRY CAREY BAIRD'S CATALOGUE. . 7 pRAIK.— THE PRACTICAL AMERICAN MILLWRIGHT AND ^ MILLER. Comprising the Elementary Principles of Mechanics, Me- chanism, and Motive Power, Hydraulics and Hydraulic Motors, Mill-dams, Saw Mills, Grist Mills, the Oat Meal Mill, the Barley Mill, Wool Carding, and Cloth Fulling and Dress- ing, Wind Mills, Steam Power, &c. By DAVID CRAIK, Mill- wright. Illustrated by numerous wood engravings, and five folding plates. 1 vol. Svo. . . . . $5 00 PAMPIN.— A PRACTICAL TREATISE ON MECHANICAL EN- U GINEERINGt Comprising Metallurgy, Moulding, Casting, Forging, Tools, Workshop Machinery, Mechanical Manipulation, Manufacture of Steam-engines, etc. etc. With an Appendix on the Ana- lysis of Iron and Iron Ores. By FRANCIS CAMPIN, C. E. Tc which are added, Observations on the Construction of Steam Boilers, and Remarks upon Furnaces used for Smoke Preven- tion ; with a Chapter on Explosions. By R. Armstrong, C. E., and John Bourne. Rules for Calculating the Change Wheels for Screws on a Turning Lathe, and for a Wheel-cutting Machine. By J. LA NICCA. Management of Steel, including Forging, Hardening, Tempering, Annealing, Shrinking, and. Expansion. And the Case-hardening of Iron. By G. EDE. Svo. 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