None
All anamonium 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 eflfected 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 anmionium 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 Uberated 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 mdirect 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.^ — 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. t Ibid., p. 62. t Gooch and Fairbanks: Methods in Analysis, Gooch, p. 459. and 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 -^ 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: z + y = a, 0.7526 X + 0.5744 2/ = 6, whence, X = 5.61186 -3.2233 a, 2/ = 4.2233 a -5.6118 6, chlorine = ' . x = 0.2474 x, bromine = 'g^ y = 0.4255 y. Experimentdl Process: Indirect Determination of Chlorine and Bromine.* — Dissolve a weighed portion (0.5 grm.) of a known mixture of sodium chloride and potassium bromide in water (300 cm.^), 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 GkxKjh and Blmnenthal: 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 fimnel 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 MNO3 + 8 HCl + n MnClg = 2 MCI + 4 H2O + 2 NO + 3 CI2 + n MnCla, 1 I 2MNO2 + 4HC1 + nMnCl2 = 2MC1 + 2H2O + 2N0 + CI2 + 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 (6), the equivalent weights of nitrogen oxide, nitric acid (NO o HNO3) and nitrous acid (NO =c= HNO2), and the equivalent weights of iodine, nitric acid (3 I =0= HNO3) and nitrous acid (I =0= HNO2), may be derived two equations de- fining 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 HNOa ' HN02^ ' 63.02 ' 47.02 31 , I , 380.76 , 126.92 , ^ + xjAfrr2/ = 0, or -K^7^x + -r;^-^y = b, HNO3 ' HNOa^ ' 63.02 ' 47.02 whence, a: =0.248 6- 1.049 a, y = 2.35 a -0.185 6. 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 defining 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 247 INTERNATIONAL ATOMIC WEIGHTS, 1914 0=16 0=16 Aliirriinium Antimony Al Sb A As Ba Bi B Br Cd Cs Ca C Ce CI Cr Co Cb Cu Py Er Eu Fl Gd Ga Ge Gl Au He H In I Ir Fe Kr La Pb Lu Mg Mn Hg 27.1 120.2 39.9 74.96 137.37 208.0 11.0 79.92 112.40 132.81 40.09 12.00 140.25 35.46 52.0 58.97 93.5 63.57 162.5 167.0 152.0 19.0 157.3 69.9 72.5 9.1 197.2 3.99 1.008 114.8 126.92 193.1 55.84 82.92 139.0 207.10 174.0 24.32 54.93 200.6 Molybdenum Neodymium Neon Mo Nd Ne Ni N Os Pd P Pt K Pr Ra Rh Rb Ru Sm Sc Se Si Ag Na Sr S Ta Te Tb Tl Th Tm Sn Ti W U V Xe Yb Yt Zn Zr 96.0 144.3 Argon 20.0 Arsenic Nickel 58.68 Rariiim Nitrogen 14.01 Bismuth Osmium 190.9 Boron Oxygen 16.00 Bromine ^^ .7 O'-'" Palladium 106.7 Cadmium Phosphorus 31.4 Caesium Platinum 195.2 Calcium Potassium 39. la Carbon Proseodymium Radium 140.6 Cerium 226.4 Chlorine Rhodium 102.9 Chromium Rubidium 85.45 Cobalt Ruthenium 101.7 Columbium Samarium 150.4 Copper Scandium 44.1 Dysprosium Erbium Selenium 79.2 Silicon 28.3 Europium . : Silver 107.88 Fluorine Sodium 23.00 Gadolinium Strontium 87.63 Gallium Sulphur 32.07 nprmanium Tantalum 181.5 Glucinum Tellurium 127.5 Gold Terbium 159.2 Helium Thallium 204.0 Hydrogen Thorium 232.40 TndiiiTn. Thiilium 168.5 Iodine Tin 119.0 Iridium Titanium 48.1 Iron Tungsten 184.0 Krypton Uranium 238.5 Lanthanum Vanadium 51.0 Lead Xenon 130.2 Lutecium Ytterbium 172.0 Magnesium Manganese (Neoytterbium) Yttrium 89.0 Mercury Zinc 65.37 Zirconium 90.6 INDEX Pagb Acidic hydroxides 93 Acidimetry j^. 115 Acids, determination of, aci^imetric 115 diff^ntial 207 iodometric 202 liberated in hydrolysis of salts 203 Air, analysis 221 Air-drjring 32 Alkali carbonate, alkalimetric determination of 126 iodometric determination of 205 Alkali elements, determination of 238 Alkali hydroxide, alkaUmetric 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, glucinimi, etc 73 from iron, etc 110 from nickel, cobalt, manganese, zinc, etc. 99 Anmionia, 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 volimietric ,^.^ 11,3 systematic 'ijm B^ '^''' • • ^^ Antimony, gravimetric determination of jyi^BC^'. 103, 104 iodometric determination of r'^iX ffi^tSB, 192 Apparatus, absorption 37; '4u^^'46> 173 distillation 45, 187 drying 33, 37, 101 electrol3i;ic 51, 52, 55 filtration 63, 64, 65, 66 gasometric 25, 216, 217, 218, 221 Ignition 76, 80, 101 249 250 IXDEX Paqb A[)paratii8, reduction 144, 145 sodium hjrdroxide 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, ^avimetric 103 lodometric 188, 190 Arsenic trioxide, determination of 170 used as iodometric standard 158, 163 Arsenic trisulphide, precipitation of 103 [)entasulphiae, precipitation of 103 Arsenite, in io<lometry, 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 Bariimi 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 196 in iodometric determination of selenate 188, 197 of selenite 188 of tellurate 198 of vanadate 196 iodometric determination of 173 Burettes 25 calibration of 30 error of 31 reading of 24 •St INDEX 251 Paob 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 bariimi 71 volimietric 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 volmnetric determination of: by precipitation 213 Chlorine, iodometric determination of 174, 193 Chromate, iodometric determination of 182, 200 Chromimn, 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 detennination 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 heatmg 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 volvunetric 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 alkah carbonate and hydroxide 126 of aluminium, as oxide 97 of arsenic acid, iodometric 191 of barimn, 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 barimn chloride 69 of chloride and bromide, by indirect process 244 of chromiiun, as oxide 98 of copper, electrolytic 51 iodometric in ore 209 oxidimetric 133 of copper and nickel, electrolytic 53 of iodate, bjr 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 Pagb Experimental determination of iron, in ferrous sulphate, oxidimetric. 135 in hematite 144 of lead, as sulphate 81 of magnesium, as oxide (precipitated as anmioniiun magnesiiun 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 siUca by precipitation and volatilization 94 of silver, as chloride 70 as thiocyanate, volimietric 214 of sodimn, 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 barimn hydroxide 124 of hydrochloric acid 121 of iodine 164 of potassium permanganate 132 of sodimn 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 platinmn sponge 65 Fixed product in action of volatile reagent, determination of 48 Flasks, calibration of 29 Fluorine, gravimetric determination of 240 volmnetric 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 hj^drochloric 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 Uberated 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 Uberated 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 lodate 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 bromme 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, pavimetric 99 m 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 48 in limestone 237 Manganese, determination of, gravimetric: as phosphate 84, 86 as sulphate 48 256 INDEX Pact 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 mcrcurous 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 110 Molybdic acid, determination of, gravimetric \ 110 oxidimetric 148 Nephelometer 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, pasometric 217 iodometric 194 oxidimetric 154 Nitrates and nitrites, indirect determination of 245 Nitrites, determination of, pasometric 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 134 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 Paob Oxidations, by permanganate: of reduction product 140 of ferric salt 141, 144 of molybdic acid 148 of uranyl sulphate 151 of vanadic acid 147 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 Phospnates, precipitation of 81 of ammonium cadmium 86 of ammoniiun magnesiimi 83 of ammonium manganese 84 of ammoniiun zinc 86 Phosphoric acid, determination of, volumetric, precipitated as phosphomolybdate 148 as uranyl phosphate 215 Phosphoinolybdic acid, determination of 148 Phosphorus, determination of, in iron and steel 148 Pipettes, calibration of 30 Potassimn, 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 filtration of, by anthracene 66 by asbestos 64 by paper 63 by spongy platinmn 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 calcimn 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 bariimi 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 cadmimn 1 10 of copper (cupric) 105 of lead 109 of mercury (mercuric) 101, 102 of molybdenimi 110 of nickel 108 of tin (stannous) 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 Pagh 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 alkaUmetric) 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 weighmg 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 Pags 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 151 Reduction products sensitive to action of air 147 Representative reactions of separation 230 Reverse titration in determination of sulphur dioxide 171 Selenates, iodometric determination 188, 197 Selenites, iodometric determination 188 Separations and determinations 226 Sihca, gravimetric determination 94 in limestone 235 in silicates 93 volatilization of 95 Silicates, analysis of .•••••. 