None
SYSTEMATIC ANALYSIS 239 collecting it on asbestos in the perforated crucible, washing with alcohol (97 per cent), drying at about 110 degrees and weighing as such.* The determination of potassium and sodium in silicates in- volves first of all the decomposition of the silicates, and this may be brought about according to the nature of the case, by the action of hydrochloric acid, by hydrofluoric acid and sul- phuric acid (Berzelius), or by ignition in mixture with calcium carbonate and ammonium chloride (J. Lawrence Smith). The last method is of wide application and very direct in consequence of the fact that when the residue of the ignition is extracted with water the silica and all basic elements other than the alkali elements and calcium are precipitated by the calcium hydroxide produced in the process. The determination of potassium and sodium in feldspar will illustrate the method.f Experimental Process: Determination of Potassium and Sodium in Feldspar. — Process of Decomposition. Weigh out a portion of the finely ground material (0.5 grm.), put it into a roomy platinum crucible, mix it carefully with an equal weight of pure sublimed ammonium chloride, add eight times its weight (4 grm.) of calcium carbonate (prepared by precipi- tation with ammonium carbonate and of determined purity), and mix the whole with great care. Heat the covered crucible over a low flame so regulated that the ammonium chloride will be decomposed without vola- tilizing as such, while calcium chloride (the active agent in the attack upon the silicate) is formed and ammonia is set free. When the evolution of am- monia has ceased, raise the temperature and ignite for an hour in such fashion that only the lower half of the crucible (conveniently held in an ignition-plate J) is heated to low redness. Cool, transfer the fritted mass (using water if necessary) to a dish (preferably platinum), digest with water (75 cm.3) kept hot, pulverize with a pestle any large particles, settle the insoluble residue, decant upon a filter the clear solution now containing chlorides of the alkali elements and calcium, and wash the residue thor- oughly by decantation and afterwards upon the filter. Removal of Calcium. — To the filtrate, heated to boiling, add ammonium carbonate and ammonium hydroxide, filter the solution of alkali chlorides from the precipitated calcium carbonate and set the filtrate aside. Dis- * D. U. Hill. Am. Jour. Sci., 40, 75 (1915). f For the determination of lithium associated with potassium and sodium, see Treadwell-Hall : Analytical Chemistry, 3rd ed., Vol. II, p. 53. t See footnote on p. 78. 240 QUANTITATIVE CHEMICAL ANALYSIS solve the precipitate in hydrochloric acid and reprecipitate with ammo- nium carbonate and ammonium hydroxide, filtering and washing to recover any alkali chloride which may have been included in the former precipita- tion. Evaporate the combined filtrates, dry the residue thoroughly at 110 degrees and remove ammonium chloride by cautious ignition. Dis- solve the residue in a little water, and remove residual traces of calcium by treatment of the solution with ammonium oxalate and ammonium hydroxide, standing over night, filtering, and washing. Recovery of Alkali Chlorides. — Evaporate the filtrate in a dish or large crucible of platinum, dry the residue carefully and ignite gently to remove the ammonium salts. Moisten the residue with hydrochloric acid (to recover as chloride any alkali salt changed to carbonate in the ignition), ignite gently and weigh the alkali chlorides. Separation and Determination of Potassium. — Dissolve the alkali chlorides in a little water, add in water-solution a moderate (calculated) excess of chlorplatinic acid, H2PtCl6, and evaporate the solution on the water-bath until the residue will solidify when allowed to cool. To the cooled residue add a little absolute alcohol, disintegrate the solid mass by means of a stirring rod with rounded end, filter off the precipitate upon asbestos in a weighed filtering crucible, wash with alcohol until the wash- ings are colorless, dry in an air-bath at 140 degrees, and weigh as potas- sium chlorplatinate, K2PtCl6.* Calculate the potassium oxide in the silicate. Determination of Sodium. — Calculate the amount of potassium chloride which is equivalent to the potassium chlorplatinate weighed. Deduct this amount from the weight (previously found) of the alkali chlorides, to obtain by difference (if no other alkali chloride is present) the weight of sodium chloride, from which may be found the corresponding weight of sodium oxide. Determination of Fluorine. — Fluorine contained in a sili- cate, or in a fluoride mixed with silica, may frequently be ex- pelled in the form of silicon fluoride by the action of concentrated * Instead of collecting the potassium chlorplatinate upon asbestos, it may be filtered off and washed upon a paper filter, dissolved in hot water into a platinum dish or crucible, recovered by evaporation of the solution dry at 140 degrees and weighed. In the evaporation of this solution in pure water, however, the potassium chlorplatinate undergoes a slight hydrolysis with the formation of a product of decomposition, KHPtCl5OH, which contains a smaller proportion of potassium than that in potassium chlorplatinate, K2PtCl6. Experience shows that the error due to hydro- lytic decomposition of the chlorplatinate approximates very closely 0.04 per cent of its weight. SYSTEMATIC ANALYSIS 241 sulphuric acid. When such is the case, the determination of the fluorine may be made by collecting the silicon fluoride in a suitable absorption apparatus and weighing as such (Fresenius) ; or the determination may depend either upon the formation of potassium fluosilicate and free hydrochloric acid by the action of the silicon fluoride upon a 50 per cent alcoholic solution of potassium chloride and the acidimetric determination of the free acid (Penfield)* or upon the absorption of silicon fluoride in water and the direct titration of the fluosilicic acid, pro- duced by hydrolysis, with sodium hydroxide (Hilemari).^ Fluorine contained in a silicate not decomposable b}^ sulphuric acid may be converted to soluble sodium fluoride by fusion of the silicate with sodium carbonate. A refractory fluoride may be attacked similarly if mixed with silica which greatly facilitates the decomposition. Water .extracts from the product of fusion soluble sodium fluoride with sodium silicate and sodium car- bonate and, after the nearly complete neutralization of the solu- tion by means of hydrochloric acid, the larger part of the silica may be precipitated by prolonged action of ammonium carbon- ate, nearly all the remainder of the silica may be precipitated by zinc hydroxide in ammoniacal solution (Berzelius) and boiling until the free ammonia is expelled. | The filtrate from the pre- cipitated zinc oxide, basic carbonate, and silicate contains the sodium fluoride which by reaction with calcium chloride will yield the nearly insoluble calcium fluoride. Precipitated by itself, calcium fluoride is slimy and filterable only with the greatest difficulty, but if the precaution is taken to have present in the solution of the fluoride a little sodium carbonate, before making the precipitation with calcium chloride, the mixed precipitate of carbonate and fluoride thrown down from a hot solution may be filtered off and washed. After drying and igniting the precipitate, the calcium carbonate and calcium oxide of the residue are converted to the soluble acetate by * Treadwell-Hall: Analytical Chemistry, 3rd ed., Vol. II, p. 470. f Methods in Analysis, Gooch, p. 436. J For details, see Treadwell-Hall: Analytical Chemistry, 3rd ed., Vol. II, pp. 471, 481. 242 QUANTITATIVE CHEMICAL ANALYSIS treatment with dilute acetic acid, and the excess of acid is re- moved by evaporation. The dry residue is treated with water and the insoluble precipitate (now compact and washable) is transferred to a paper filter, washed, dried, ignited and weighed as calcium fluoride. The weight of the residue must, how- ever, be corrected for possible contamination with silica by cautious treatment with concentrated sulphuric acid, removal of the excess of acid by evaporation, ignition and weighing as calcium sulphate, CaSO4 o CaF2. Analysis of Substances Yielding Ammonia Ammonium Salts. — Ammonium chloride in solution and ammonium salts of acids made volatile by hydrochloric acid may be converted to weighable form by treatment with •hydro- chloric acid (to prevent hydrolytic decomposition of the chloride and loss of volatile ammonia), evaporation of the solvent and drying of the residue at 110 degrees. Ammonium chloride in solution containing a little hydrochloric acid may also be de- termined by treatment with chlorplatinic acid, evaporation of the solution to dryness, extraction of the residue with absolute alcohol, collection of the precipitate upon asbestos in the filter- ing crucible, drying at 130 degrees, and either weighing the ammonium chlorplatinate (NH4)2PtCl6, as such or weighing the residue of platinum after igniting very cautiously. All ammonium salts in solution are decomposed by sodium hydroxide, potassium hydroxide, or calcium hydroxide, and the ammonia thus set free may be volatilized from the boiling solution and absorbed in acid.* If the retaining acid is hy- drochloric acid, the ammonium chloride thus formed may be recovered by evaporation of the solution and determined grav- imetrically by one of the methods described above. If the absorption of the free ammonia is effected by a measured amount of standard acid, the excess of acid may be determined by titration with standard alkali, with methyl orange (not phenol- phthalein) as the indicator, and the difference between the acid * Treadwell-Hall: Analytical Chemistry, 3rd ed., Vol. II, p. 59. SYSTEMATIC ANALYSIS 243 taken and that found in the titration will be the measure of the ammonia. The ammonia liberated by the action of sodium hydroxide upon minute amounts of ammonium salts in solution, such as occur in drinking water, may be collected in an aqueous distillate and determined colorimetrically by use of "Nessler's reagent." * Organic Compounds. — Ammonia produced from nitroge- nous (organic) compounds by oxidation with potassium perman- ganate in presence of concentrated sulphuric acid and liberated by subsequent treatment with sodium hydroxide (Kjeldahl}\ may be thus determined and made the measure of the organic nitrogen. Indirect Analysis The relation of the equivalent weights of the substances in- volved when two compounds constituting a mixture are changed chemically, with the formation of definite products of reaction, makes it possible to determine by calculation the amounts of the original compounds when (I) the weight of the mixture is known and the combined weights of the products can be deter- mined or when (II) the two original compounds are susceptible to two different reactions each of which yields determinable products. In such cases, it is possible to express the relations in two equations involving two unknown quantities. The indirect determination of chlorides and bromides consti- tuting a mixture of known weight and the indirect determina- tion of nitrates and nitrites in solution (in absence of interfering substances) will serve to illustrate these indirect methods. Chlorides and Bromides. J — From a solution containing soluble chlorides and bromides, the chlorine and bromine may be precipitated, by silver nitrate, in the form of silver chloride and silver bromide. If the mixture of silver chloride and silver bromide is weighed and the amount of the combined silver * Treadwell-Hall: Analytical Chemistry, 3rd ed., Vol. II, p. 60. f Ibid., p. 62. J Gooch and Fairbanks: Methods in Analysis, Gooch, p. 459. 244 QUANTITATIVE CHEMICAL ANALYSIS determined, by electrolytic reduction and weighing, the data are at hand for the indirect determination of the amounts of chlorine and bromine originally present in the mixture of solu- ble chlorides and bromides. From the relations between the weight of the mixed silver salts (a), the weight of the silver (6), the ratio of the equivalent of silver to that of silver chloride (107.88 + 142.34 = 0.7526), and the ratio of the equivalent of silver to that of silver bromide (107.88 -f- 187.80 = 0.5744), may be derived two equations defining the amount of silver chloride (x) and the amount of silver bromide (y) in the mixed silver salts: x + y = a, 0.7526 x + 0.5744 y = b, whence, x = 5.6118 b -3.2233 a, y = 4.2233 a- 5.61186, and chlorine = ~~j±x = 0.2474s, 79.92 bromine = Ig7 gQ y = 0.4255 y. Experimented Process: Indirect Determination of Chlorine and Bromine.* — Dissolve a weighed portion (0.5 gran.) of a known mixture of sodium chloride and potassium bromide in water (300 cm.3), add a few drops of nitric acid and then, gradually and with constant stirring, a solution of silver nitrate until no further precipitation takes place. Heat the liquid to boiling and set the whole aside to cool in the dark. When the precipitate has settled, collect it in a weighed filtering crucible provided with a layer of asbestos upon which rests a perforated platinum disk covering the as- bestos and in contact with the wall of the crucible, so that the disk and the crucible may be made parts of an electrical circuit. Wash the pre- cipitate with water containing a few drops of nitric acid and then with a little pure water, dry at about 150 degrees, weigh and determine the weight of the mixed silver salts. * For direct determinations of chlorine and bromine in halide salts, see Gooch and Blumenthal: Am. Jour. Sci., 35, 54. Blumenthal: Ibid., 36, 93. Gooch and Cole: Ibid., 37, 257. For a direct determination of chlorine, bromine and iodine similarly associated, see Cole: Ibid., 38, 265. SYSTEMATIC ANALYSIS 245 Set the capped crucible upon cold metal and fuse the silver salts with a blow-pipe flame directed upon the mass from above. Cover the junction between cap and crucible with a rubber band, nearly fill the crucible with a 10 per cent solution of oxalic acid in 25 per cent alcohol, and pass an electric current (0.5 amp.) through the solution, between a platinum anode dipping in the liquid and the crucible used as the cathode. When the re- duction of the silver salts is judged to be complete, set the crucible (after removing the band and the cap) in the holding funnel of the filtering flask, wash well with water, ignite the residue at very low red heat, weigh, and determine the weight of the residue. Repeat the operation of electrolyzing and weighing until constancy of weight shows that the reduction of the silver salts to silver is complete. Calculate, by the method indicated above, the weight of sodium chloride and the weight of potassium bromide in the original mixture. Nitrates and Nitrites. — When nitrates and nitrites in solu- tion are acted upon by manganous chloride in presence of con- centrated hydrochloric acid the following reactions take place: 2 MN03 + 8 HC1 + n MnCl2 = 2 MCI + 4 H2O + 2 NO i i 2 MN02 + 4 HC1 + n MnCl2 = 2 MCI + 2 H2O + 2 NO + C12 + n MnCl2. The chlorine evolved in these reactions may be absorbed in potassium iodide (see pp. 194, 196), while the nitrogen oxide is passed on for measurement over a solution of sodium hydroxide (see p. 218). The weight of iodine set free by the chlorine may be determined titrimetrically and the weight of nitrogen oxide may be calculated from the measured volume of that gas. From the relations between the weight of nitrogen oxide (a), the weight of iodine (b), the equivalent weights of nitrogen oxide, nitric acid (NO o HN03) and nitrous acid (NO =c= HNO2), and the equivalent weights of iodine, nitric acid (3 I o HNO3) and nitrous acid (I =c= HNO2), may be derived two equations de- nning the unknown amounts of nitric acid (x) and of nitrous acid (y) corresponding to the nitrate and nitrite in the original solution : * * Roberts: Methods in Analysis, Gooch, p. 272. 246 QUANTITATIVE CHEMICAL ANALYSIS NO NO 30.01 30.01 = a or HN03 ' HN02" 63.02" 47.02 » 31 I _ 380.76 , 126.92 x ' TTXTO y ~ °> or AO r»o x "" /IT no y ~ "> HN03 ' HN02* 63.02 * 47.02 whence, x= 0.2486- 1.049 a, y = 2.35 a- 0.1856. The amounts of corresponding nitrates and nitrites are, of course, easily found from the values for nitric acid and nitrous acid thus determined. From the form of the expressions denning the values of the unknown quantities in the examples given, it is obvious that, while the accuracy of an indirect method of analysis depends upon the choice of reactions, the experimental error *is always more or less magnified in the process of computation. In general, a reliable direct method is preferable to an indirect method of determination. SYSTEMATIC ANALYSIS INTERNATIONAL ATOMIC WEIGHTS, 1914 247 0=16 0=16 Aluminium Al 27 1 Molybdenum Mo 96 0 Antimony Argon Sb A 120.2 39.9 Neodymium Neon Nd Ne 144.3 20.0 Arsenic As 74.96 Nickel Ni 58.68 Barium Ba 137.37 Nitrogen N 14.01 Bismuth. ... Bi 208.0 Osmium Os 190.9 Boron B 11.0 Oxygen 0 16.00 Bromine Br 79.92 Palladium Pd 106.7 Cadmium Cd 112.40 Phosphorus P 31.4 Caesium Ca 132.81 Platinum Pt 195.2 Calcium Ca 40 09 Potassium K 39 10 Carbon c 12 00 Proseodymium Pr 140 6 Cerium Ce 140 25 Radium . .. Ra 226 4 Chlorine a 35.46 Rhodium Rh 102.9 Chromium Cr 52 0 Rubidium . .. Rb 85 45 Cobalt Co 58 97 Ruthenium. Ru 101 7 Columbium Cb 93 5 Samarium .. Sm 150 4 Copper .. Cu 63 57 Scandium .... Sc 44 1 Dysprosium .... Dy 162.5 Selenium Se 79 2 Erbium Er 167 0 Silicon Si 28 3 Europium Eu 152 0 Silver Ag 107 88 Fluorine Fl 19 0 Sodium Na 23 00 Gadolinium Gallium Gd Ga 157.3 69 9 Strontium Sulphur Sr S 87.63 32 07 Germanium Glucinum Ge Gl 72.5 9 1 Tantalum Tellurium Ta Te 181.5 127 5 Gold.. Au 197 2 Terbium Tb 159 2 Helium He 3 99 Thallium Tl 204 0 Hydrogen H 1.008 Thorium Th 232.40 Indium .... In 114 8 Thulium Tm 168 5 Iodine I 126 92 Tin Sn 119 0 Iridium Ir 193 1 Titanium Ti 48 1 Iron Fe 55.84 Tungsten W 184.0 Krypton Lanthanum Lead Kr La Pb 82.92 139.0 207 10 Uranium Vanadium Xenon U V Xe 238.5 51.0 130 2 Lutecium Lu 174.0 Ytterbium.. Yb 172.0 Magnesium Mg 24 32 (Neoytterbium) Manganese Mn 54.93 Yttrium Yt 89.0 Mercury He 200.6 Zinc Zn 65.37 Zirconium 7,r 90.6 INDEX PAGE Acidic hydroxides 93 Acidimetry 115 Acids, determination of, acidimetric 115 differential 207 iodometric 202 liberated in hydrolysis of salts 203 Air, analysis 221 Air-drying .•••••. 32 Alkali carbonate, alkalimetric determination of 126 iodometric determination of 205 Alkali elements, determination of 238 Alkali hydroxide, alkalimetric determination of 126 iodometric determination of 204 Alkalimetry 115 Alumina, determination of, in limestone 235 Aluminium, gravimetric determination of 72, 96, 235 precipitation of, as basic acetate 99 as chloride 72 as hydroxide 96 separation of, from iron, glucinum, etc 73 from iron, etc 110 from nickel, cobalt, manganese, zinc, etc. 99 Ammonia, determination of 242, 243 substances yielding 242 Ammonium salts, determination of ammonia of 242 of nitrogen in 219 Analysis, colorimetric 222 gasometric 215 gas-analysis 220 gas-volumetric 217 gravimetric 32 electrolytic 49 precipitation 56 volatilization 34 volumetric 113 systematic 226 Antimony, gravimetric determination of 103, 104 iodometric determination of 171, 188, 192 Apparatus, absorption 37, 43, 45, 173 distillation 45, 187 drying 33, 37, 101 electrolytic 51, 52, -55 nitration 63, 64, 65, 66 gasometric 25, 216, 217, 218, 221 ignition 76, 80, 101 249 250 INDEX PAGE Apparatus, reduction 144, 145 sodium hydroxide 123 volatilization 37, 40, 43, 45 volumetric 24, 25, 27, 31, 123, 124, 216, 217, 218, 221 limit of error of 31 weighing 12, 21 Arsenic, determination of, gravimetric 103 iqdometric 188, 190 Arsenic trioxide, determination of 170 used as iodometric standard 158, 163 Arsenic trisulphide, precipitation of 103 pentasulphide, precipitation of 103 Arsenite, in iodometry, standard solution of 163 Atomic weights, table of 247 Balance, analytical 11 inequality of arms of 19 sensitiveness of 17 zero-point of 13 Barium, gravimetric determination of: precipitation as carbonate 90 as chloride .*. 71 as oxalate 88 as sulphate 79, 80 separation of, from calcium and magnesium 71 Barium hydroxide, standardization of .' 124 Basic acetate process 99 Basic hydroxides 96 Basic ions, grouping of 228 forms of precipitated by group reagents 229 Bismuth, gravimetric determination of: precipitation of, as basic carbonate 92 as sulphide 109 Boric acid, distillation of 45 gravimetric determination of 44 with calcium oxide as retainer 46 with sodium tungstate as retainer 47 volumetric determination of: acidimetric 127 iodometric 202 Brass, analysis of 230 Bromates, iodometric determination of 181, 199 Bromide and chloride, direct determination of 244 indirect determination of 243, 244 Bromide-ion, determination of 69 Bromine, evolved in reductions in iodometric determination of selenate 188, 197 of selenite 188 of tellurate 198 of vanadate 196 iodometric determination of 173 Burettes. 25 calibration of error of reading of 24 INDEX 251 PAGE Cadmium, gravimetric determination of: precipitated as carbonate 91 as phosphate 86 as sulphide 110 Calcium, determination of, in limestone 235 gravimetric determination of : precipitation of as carbonate 90 as oxalate 86, 236 as sulphate 81 separation of, from barium 71 volumetric determination of 133 Calcium oxide, retainer for boric acid 46 Calibration, of burettes 30 of flasks 29 of pipettes 30 Carbonates, decomposition of 38 precipitation of 89 Carbon, determination of, by combustion process 44 Carbon dioxide in carbonates. 38 gravimetric determination of 38 by loss on heating 38 by loss on heating with flux 39 by loss in action of acid 40 by direct weighing 42 Carbonic acid, iodometric determination of 208 Cerium dioxide, iodometric determination of 183, 188 Chlorates, iodometric determination of 194 oxidimetric determination of 154 Chloride and bromide, direct determination of 244 indirect determination of 243, 244 Chloride ion, gravimetric determination of 67 as silver chloride 67 in barium chloride 69 volumetric determination of: by precipitation 213 Chlorine, iodometric determination of 174, 193 Chromate, iodometric determination of 182, 200 Chromium, gravimetric determination of: precipitation as hydroxide 98 Cobalt, gravimetric determination of: precipitation as sulphide 112 separation of, from aluminium and iron 99 from manganese (and soluble sulphides) 108 from zinc 107 Colloidal suspensions 60 Colorimeters 223 Colorimetric processes 222 Combustion of organic substances 44 Comparison tubes 223 Copper, determination of, in brass 230, 231 in ore 209 gravimetric determination of: electrolytic 51, 53 precipitation as oxalate 89 as sulphide 105 252 INDEX PAGE Copper, separation of, from iron 231 from nickel 53, 231 volumetric determination of, iodometric 184, 209 oxidimetric 133 Cyanide-ion, volumetric determination of: by precipitation 212 Dehydration 32, 33 Desiccators 33 Dimethylglyoxime, use of, in determination of nickel 232 Distribution of solute between solvents • 56 Double weighing 19 Drying, by heating 33 in air. 32 in desiccators 33 Drying apparatus 33, 37 Electrodes, rotating 52 small, with weighable cell 54 stationary 50 Electrolysis, conditions of ^. 49 Electrolytic processes 49 for determination of chloride and bromide: of copper 51, 53 of copper and nickel 53 End-color with starch. 160 End-points in volumetric precipitation processes 160, 210, 212, 215 Experimental processes: analysis of brass 230 of limestone 233 of silicates (for alkali elements) 239 determination of acids, acidimetric 125 of alkali carbonate and hydroxide 126 of aluminium, as oxide 97 of arsenic acid, iodometric 191 of barium, as carbonate 90 as sulphate 80 of boric acid, iodometric 203 of calcium, as oxide: precipitated as oxalate 88 of carbon dioxide, in calcite: by loss on heating 39 on heating with flux 40 in action of acid 41 of chloride ion, in barium chloride 69 of chloride and bromide, by indirect process 244 of chromium, as oxide 98 of copper, electrolytic 51 iodometric in ore 209 oxidimetric 133 of copper and nickel, electrolytic 53 of ibdate, by action of iodide 175 of iodine in iodide, by action of iodate 179, 180 by volatilization and reoxidation of residue. 190 of iron, as ferric oxide 99 INDEX 253 PAGE Experimental determination of iron, in ferrous sulphate, oxidimetric. 135 in hematite 144 of lead, as sulphate 81 of magnesium, as oxide (precipitated as ammonium magnesium carbonate) 91 as pyrophosphate 84 as sulphate 48 of manganese, as pyrophosphate 86 as sulphate 49 of mercury, as sulphide 102 of nickel, electrolytic 53 of phosphorus in iron and steel 148 of potassium, in silicates 239 of silica by precipitation and volatilization 94 of silver, as chloride 70 as thiocyanate, volumetric 214 of sodium, in silicates 239 of sodium hydroxide and carbonate (in crude caustic soda).. 126 of sulphate ion, in copper sulphate 76 of sulphurous acid, by iodate process 209 of water of composition, in barium chloride 35 in copper sulphate 36 Standardization of solutions: of barium hydroxide 124 of hydrochloric acid 121 of iodine 164 of potassium permanganate 132 of sodium hydroxide 122 of sodium thiosulphate 166, 167 Ferric chloride, iodometric determination 184 Ferric hydroxide, precipitation of 99 Ferric oxide, determination of, in limestone 234 Ferric salts, oxidimetric determination of iron in 141 after reduction: by hydrogen sulphide 142 by stannous chloride 143 by sulphur dioxide 142 by titanous sulphide 143 by zinc 141 Ferrous oxide, determination of, in limestone 235 Filtration, by anthracene 66 by asbestos. 64 by paper 63 by platinum sponge 65 Fixed product in action of volatile reagent, determination of 48 Flasks, calibration of 29 Fluorine, gravimetric determination of 240 volumetric determination of 240 Formate, determination of, oxidimetric 138 Forms precipitated by group reagents ' 229 Gas analysis 220 Gasometric processes 215 254 INDEX PAGE Gas-volumetric methods 217 Glucinum, separation of, from aluminium 73 Gold chloride, iodometric determination of 183 Gravimetric analysis 32 Helianthin (methyl orange), indicator 116 Higher oxides, determination of, of lead 152 of manganese 153 Hydrochloric acid, in permanganate titrations 138 iodometric determination of 207 standardization of 121 Hydrogen, gravimetric determination of, in combustion process .... 44 Hydrogen dioxide, iodometric determination of 181 oxidimetric determination of 135 Hydroxides, precipitation of 92 Hypochlorites, iodometric determination of 181 Indicators 115, 129 methyl orange 116 phenolphthalein 118 starch 160 Indirect analysis «. 243 lodate, determination of 175 with periodate 177 reaction of, with iodine in strong hydrochloric acid 160, 178 with iodide in dilute acid 175 standard solution of 168 use of, in determination of copper 209 of iodide 177, 178, 179, 180 of iodine 180 of sulphurous acid 209 oxidations by, in presence of hydrochloric acid 208 Iodide, decomposition of, by nitrous acid 186 determination of, gravimetric 69 iodometric 177 lodide-iodate mixture, use of, in determinations: of alkali carbonate 205 of alkali hydroxide 204 of free acid 174, 202 of acid liberated in hydrolysis 203 Iodide-ion, determination of, gravimetric 69 Iodine, action of, in excess and titration of excess 172 upon basic hydroxides 205 determination of, after extraction from water solution 185 in solution 169 liberated from iodide: by antimonic acid 188, 192 by arsenic acid 187, 189 by bromates 181 by bromine 173 by chlorine 174 by chromates 182 by cupric salt 184 by ferric chloride 184 by gold trichloride 183 INDEX 255 PAGE Iodine, determination of, liberated from iodide : by hydrogen dioxide 181 by higher oxide of cerium 183 of lead 182 by hypochlorites 181 by molybdic acid 188 by permanganate 182 by iodate 174, 177 by selenic acid 188 by selenious acid 188 liberated from iodate 175, 177 liberated from periodate 176, 177 direct titration by 170 extraction of, from aqueous solution 185 reaction with, antimonite 171 arsenite 158 sulphide 172 sulphurous acid 156 thiosulphate 158 separation from bromine and chlorine 190, 244 standard solution of 164 volatilization of, with determination in distillate 186 by reoxidation of residue 189 lodometric processes 156 Iron, determination of, gravimetric 99 in brass 232 in ferric condition 99, 234 in ferrous condition 99, 235 in hematite 144 iodometric 184 oxidimetric 134, 141 separation of, as basic acetate 99 as hydroxide 99 as sulphide 110 Jones reductor , 145 Le Chatelier, principle of opposed actions 9 Lead, determination of, as sulphate 81 in brass 231 precipitation of, as sulphide 109 Lead higher oxides, determination of, iodometric 182 oxidimetric 152 Limestone, analysis of 233 Liquids, expansion and contraction of 25 Mass-action, Law of 6 Magnesium, determination of, as oxide (precipitated as ammonium magnesium carbonate) 90 as phosphate 83 as sulphate t 48 in limestone 237 Manganese, determination of, gravimetric: as phosphate 84, 86 as sulphate 48 256 INDEX PAGE Manganese, determination of, oxidimetric 136 precipitation of, as sulphide Ill Manganese higher oxides, determination of: iodometric 194 oxidimetric 153 Measurement of volume 24 correction of 26 Mercury, determination of, as mercurous chloride 70 as mercurous oxalate 88 as mercuric sulphide 101, 102 Methods, choice of 227 Methyl orange, use of, as indicator 116 behavior with acids and bases 117 Molybdate solution, preparation of 149 Molybdenum, determination of, iodometric 188 oxidimetric 148 precipitation of, as sulphide 1 10 Molybdic acid, determination of, gravimetric 110 oxidimetric 148 Nephelqmeter 224 Neutralization processes #.. 115 Nickel, determination of, gravimetric 112, 232 electrolytic 53 separations of, from aluminium, etc 99 from manganese 108 from zinc 107 Nitrates, determination of, gasometric 217 iodometric 194 oxidimetric 154 Nitrates and nitrites, indirect determination of 245 Nitrites, determination of, gasometric 245 iodometric 196 oxidimetric 136 Nitrogen, determination of, in air (with inert elements). 221 in ammonium salts 219 in organic substances 220 Normal solutions 113 Orthophosphate ion, determination of 81 Over-reduction and correction, in oxidimetric processes 150 Oxalates, oxidimetric determination of 133 Oxidation processes 129 Oxidations, by iodine 156-158, 189, 192 by permanganate 130 of ferrous sulphate of formates 138 of hydrogen dioxide 135 of manganous sulphate 136 of nitrous acid or nitrites 136 of oxalates 133 of reducing agent used in excess 152 for chlorate 154 for higher oxides 152, 153 for nitrates 154 INDEX 257 PAGE Oxidations, by permanganate: of reduction product 140 of ferric salt 141, 144 of molybdic acid 148 of uranyl sulphate 151 of vanadic acid 117 of reduction products sensitive to air 147 over-reduction and correction in 150 Oxides, precipitation of 86 determination of, oxidimetric, of lead 152 of manganese 153 Oxidimetry. 129 Oxygen, in air, determination of 221 Periodates, iodometric determination of 176, 177 Permanganate, use of, in oxidation processes 130 iodometric determination of 182 Phenolphthalein, use of, as indicator 118 Phosphates, precipitation of ;. 81 of ammonium cadmium 86 of ammonium magnesium 83 of ammonium manganese 84 of ammonium zinc 86 Phosphoric acid, determination of, volumetric, precipitated as phosphomolybdate 148 as uranyl phosphate 215 Phosphomolybdic acid, determination of 148 Phosphorus, determination of, in iron and steel 148 Pipettes, calibration of 30 Potassium, determination of 238, 239 Potassium permanganate, use of, in oxidations 130 in presence of hydrochloric acid. 138 standardization 131 Precipitates 57 colloidal 60 conditions affecting solubility of 58 definiteness of composition of 62 nitration of, by anthracene 66 by asbestos 64 by paper 63 by spongy platinum 65 insolubility of 58 purity of 61 separation of 62 subdivision of 58 washing of , 62 Precipitation, conditions affecting 58 medium of 58 of basic acetates, aluminic 99 ferric 99 of carbonates 89 of barium 90 of bismuth (basic) 92 of cadmium 91 of calcium. 90 258 INDEX PAGE Precipitation, of carbonates: of magnesium (ammonium) 90 of strontium 90 of zinc 91 of chlorides 67 of aluminium 72 of barium 71 of mercury (mercurous) 70 of silver 69 of hydroxides 92 acidic 93 silicic acid 93 tungstic acid 95 basic 96 aluminium 96 chromic 98 ferric 99 of oxalates 86 of barium 88 of calcium 86 of copper 89 of mercury *. 88 of strontium 88 of phosphates 81 of magnesium 83 of manganese 84 of sulphates 73 of barium 79 of calcium 81 of lead 81 of strontium 80 of sulphides 100 in acid solution 101 of antimony (tri) 103, 104 of arsenic (tri) 103 of arsenic (penta) 103 of bismuth 109 of cobalt 108 of cadmium 110 of copper (cupric) 105 of lead 109 of mercury (mercuric) 101, 102 of molybdenum 110 of nickel 108 of tin (stannpus) 109 of tin (stannic) 109 of zinc. 106, 107 in alkaline solution 110 of cobalt 112 of iron 110 of manganese Ill of nickel 112 Preparation of substances for analysis 226 for weighing 32 Principle of Le Chatelier 9 INDEX 259 PAGE Procedures, in gravimetric analysis 32 in volumetric analysis 113 Processes of analysis: dependent upon differences in solubility 56 electrolytic 49 empirical 10 iodometric 156 action of iodate in hydrochloric acid 208 action of iodide-iodate mixture 202 action of iodine on basic hydroxides 205 determination of free iodine 169 of iodine liberated: by bromine 173, 196 by chlorine 174, 193 by oxidizers 180 oxidation by iodine 170 following reduction 198 volatilization and determination of iodine 186 and reoxidation of residue 189 of neutralization (acidimetric and alkalimetric) 115 of oxidation 129 by permanganate 130 after over-reduction and correction 150 after reduction 140, 141 after reduction with protection from air 147 of excess of agent used in reduction 152 of precipitation, gravimetric 56 volumetric 210 of systematic analysis 226 of volatilization 34, 48 loss on heating 35, 36, 38, 39 loss in reaction 40 weighing of fixed product 48 weighing of volatile product 36, 42, 44 of weighing 14 Qualitative tests 227 Reactions, analytical 1 completion of 6 course of 1 non-reversible 4 reversible 4 successive 3 velocity of 5 Reduction, by hydriodic acid: of antimonic acid 188, 192 of arsenic acid 188, 190 of bromates 181 of chromates 182 of cupric salts 184 of ferric chloride 184 of gold trichloride 183 of hydrogen dioxide 181 260 INDEX PAGE Reduction, by hydriodic acid: of higher oxides, of cerium 182 of lead 182 of manganese 194 of nitrogen 186, 194, 196 of hypochlorites 181 of iodates 174, 175, 177 of molybdic acid 188 of periodate 176, 177 of permanganate 182 of selenic acid 188 of selenious acid 188 in oxidimetric processes 141, 147, 150 of ferric salts 141 by zinc 141, 144 by hydrogen sulphide 142 by sulphur dioxide 142 by stannous chloride 143 by titanous sulphate 143 of molybdic acid 148 of ^vanadic acid 147, 150 of uranyl sulphate .*. solution of arsenite 163 barium hydroxide 124 hydrochloric acid 120 iodate 168 iodine 164 potassium permanganate 131 silver nitrate 214 sodium hydroxide 121 sodium thiosulphate 165 INDEX 261 PAGE Stannic sulphide 109 Stannous sulphide 109 Starch indicator, end color of . . . 160 influence of iodide upon 161 preparation of 162 Strontium, gravimetric determination of, as sulphate 80 volumetric determination of 133 Sulphate ion, gravimetric determination of: as barium sulphate 73 in copper sulphate 76 Sulphides, iodometric determination of 172 precipitation of 100 in acid solution 101 in alkaline solution 110 Sulphuric acid, acidimetric determination of 125 iodometric determination of 208 Sulphurous acid, iodometric determination of 171 oxidation of, by iodine 156 Systematic analysis 226 Tellurate, iodometric determination of 198 Tellurous oxide, iodometric determination of 201 volumetric determination of, by precipitation 211 ThiosulphatCj iodometric determination of 170 reagent for iodine 158 standard solution of 165 standardization of 166, 167 Tin, gravimetric determination of 109, 230, 231 in brass 230, 231 Tin sulphides, precipitation of, with conversion to oxide 109 Tungsten trioxide, gravimetric determination of 95 Uranium, volumetric determination of 151 Uranyl sulphate, reduction and oxidation of 151 Vanadic acid, iodometric determination of 188, 196, 198 oxidimetric determination of 150 Volume, correction of 26 measurement of 24 variation of 25 Volumetric analysis 113 apparatus used in 24 Washing of precipitates 62 Water, gravimetric determination of 34 by loss on heating 35 by loss on heating with flux 36 by direct weighing 36 Weighing, correction of 19 double 19 method of equal swings 15 of oscillations 16 of substitution 19 operation of 14 262 INDEX PAGE Weighing, preparation for 32 process of 11 Weights, analytical 21 testing of 21 Weighable electrolytic cell 54 Zinc, gravimetric determination of: precipitated as basic carbonate 91 as ammonium phosphate 86 as sulphide 106 separation of, from iron 99, 1 10 from nickel and cobalt 107 from alkali and alkali-earth elements . . 107 THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. 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