Chapter IX

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