54 UNIVERSITY OF COLORADO 



companies to carry the actual bromo-cyanide crystals. The 

 method of preparation is as follows: Bromo salts include potas- 

 sium bromide and bromate, roughly in quantities required for 

 the reaction. Assuming this to be ? 



2KBr+KBr0 3 +3KCN+3H 2 S0 4 ==3BrCN+3K 2 S0 4 +3H o 

 238+167+195+294=318+522+54. 



"Bromo salts imported from Germany are very impure, but 

 contain the correct mixture to satisfy the above reaction. The 

 charge used at Kalgoorlie to generate 100 lbs. of BrCN is : 



Mixed bromo salts 125 lbs. 



Cyanide (100$ 65 lbs. 



Sulphuric acid (70$ 147 lbs. 



"The salts are agitated in a wood or lead lined vat of about 

 200 gallons capacity, securely covered by a lid, through which a 

 revolving stirrer or paddle works. Above this is a small vat, in 

 which is stored the necessary charge of cyanide dissolved in 40 

 gallons of water. The vat is first f filled with water, the agitator 

 started, and the sulphuric acid added slowly and carefully. The 

 whole charge is now left to stand until cool, say, 1 hour, as the 

 great heat generated by the addition of the acid would destroy 

 the bromo-cyanide. When cool, the mixed bromo-salts are added 

 gradually and the solution of cyanide run in simultaneously with 

 constant stirring. The reaction commences almost immediately, 

 but is not thoroughly completed until after 6 hours' continuous 

 agitation." 



This method can be modified for laboratory use where the 

 bromo-salts are not available for testing the ores. 



ROASTING. 



Should none of the foregoing tests give satisfactory results 

 the ore may be roasted in the muffle, first to a dead roast; second, 

 in case of silver ores, by a chloridizing roast, as plain roasting 

 invariably interferes very seriously with silver extraction, and 

 almost as persistingly greatly increases the extraction of the gold. 



In a chloridizing roast the loss of gold by volatilization is 

 often very heavy, and should, in all cases, be determined in the 

 following manner: 



Mix the necessary amount of dry salt with the ore, and reduce 



