42 Laboratory Tests. 
in the flask or beaker (note amount of solution used). 
Now filter and finish the titration. As before, multiply 
the standard factor representing the strength of the cy- 
anide solution by the number of cubic centimeters of so- 
lution used; this product multiplied by one hundred 
gives the ore’s percentage in metallic copper. 
Note.—The final addition of cyanide solution 
should be added from the burette drop by drop, the flask 
containing the assay being well shaken each time until 
the blue or lilac tint can scarcely be discerned at the 
upper edge of the liquid when viewed against a white 
background. Many chemists titrate to a faint rose or 
pink tint (Furman). 
LABORATORY TESTS OF GOLD AND SILVER 
ORES. 
OBJECT OF TESTS. 
The following tests of gold and silver ore are made 
in order to determine the probable percentage of gold 
which may be extracted by the cyanide, chlorination and 
amalgamation processes. In testing by the cyanide pro- 
cess it should be borne in mind that the least amount 
of cyanide which it is possible to use, and yet extract 
all the gold, the more economic will be the process of 
treatment. In general, the finer the ore is crushed and 
the longer that it is leached, the greater will be the per 
cent. of extraction. The percentage of gold extraction 
by the chlorination process will depend not only upon 
the fineness of crushing but also upon the per cent. of 
free gold present, the amount of chlorine gas generated 
per ore charge and the time of agitation. Amalgama- 
tion tests, or assays, are made on gold and silver ores to 
determine the probable per cent. of gold and silver 
which may be extracted by the amalgamation process of 
milling. 
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