Chapter 7

SILVER, GOLD, PLATINUM, CYANIDES, MERCURY.

SILVER--Detection 87 Dry assay 87 (1) Scorification 88 (2) Pot assays, average ores 90 " ores with metallic oxides 91 " ores with metallic sulphides 91 Explanatory notes on the fusion 93 The effect of charcoal, flour, &c. 94 The effect of nitre 95 The effect of mineral sulphides 95 (3) Cupellation 98 The loss of silver 101 Condition affecting the loss 102 Methods of correction 103 Lead required for cupellation 105 (4) Calculation of the results in ounces to the ton of 2240 lbs. Table 107 Ores with metallic particles 108 (5) Explanatory notes 110 (6) Examples of dry silver assays 113 Wet assays 116 Gravimetric method 117 Gay-Lussac's method 119 Volhard's method 121 A modified Gay-Lussac 123 Volhard's method applied to arsenic 124 GOLD--Detection 126 Amalgamation assay 126 Dry assay 127 (1) Size of charges 127 (2) Sampling 127 (3) Assay tons 131 (4) Small buttons, weighing 131 " " measuring 133 (5) Concentration in lead 136 Quartz ores 136 Ores with oxide of iron 138 Ores with metallic sulphides 139 (6) Cyanide charges, residues, &c. 140 (7) Cupellation 142 Cupels 142 Cupellation temperature 143 Cupellation loss 145 (8) Inquartation 146 (9) Flatting 149 (10) Parting, in flasks 151 " in test tubes 152 " in glazed crucibles 153 " Loss, &c. 154 (11) Check assays, surcharge 154 (12) Bullion assays in special apparatus 156 Silver, &c., in gold bullion 157 (13) Sampling of base bullion, &c. 157 CYANIDES--Commercial cyanides 160 Double cyanides 161 Prussic acid 162 Gold-dissolving power of cyanide liquor 162 Assay for cyanide strength 163, 165 Assay of commercial cyanide 167 Alkalinity of cyanides 167 Acidity of ores 168 Metals in cyanide liquors 169 Cyanicides 169 PLATINUM 170 IRIDIUM 171 MERCURY 171 Dry assay 172 Wet method 173