1889-90.1 ARSENIC AND SULPHUR. 141 



ARSENIC AND SULPHUR AS METALLURGICAL AGENTS 

 IN THE TREATMENT OF CANADIAN AURIFEROUS 

 AND ARGENTIFEROUS ORES. 



By R. Dewar. 



[Read ijth Alarch, i8go.) 



We are all too well aware of the direful results on amalgamation caused 

 by the presence, in the ore operated on, of arsenic and more especially 

 sulphur, as their capacities for neutralizing the mercury and thus render- 

 ing it useless to hold the gold or silver that passes over it, are very great. 

 These troublesome elements are got rid of at the present time by roast- 

 ing, but this causes expense, and metallurgists even hint at a loss of the 

 precious metals by this treatment. I differ with them so far as to say, 

 that if there is any loss, which there may be, the same is so minute that 

 practically there is none. 



The chlorination process as it is variously applied according to the 

 different patents granted for it, has a drawback in the treatment of these 

 ores, in its restriction to those only in which the metals are in a state of 

 fine division, therefore in ores like some of ours in which the metals are 

 in larger bodies, it is rendered useless ; but in any case the ores must 

 first be roasted to get rid of the arsenic and sulphur, as they form trouble- 

 some salts with the chlorine. Now, it is quite apparent that if part of 

 the treatment could be dispensed with, it would be the means of increas- 

 ing the returns in a great many mines at present in operation. Why 

 then could we not dispense with the chlorination, and do the work with 

 the roasting alone .-* It may seem impossible at first as the roasting is 

 merely a preliminary to the chlorination which is the principal. 



There is a law of metallurgy which has been greatly neglected, and I 

 may say has not been paid the attention or given the research due to it. 

 That law expressed is that when a metal is alloyed with one or more of 

 the other metals, the resultant alloy has a lower melting point than the 

 mean of the several melting points of the constituents taken together. 

 Let us take an example, for instance, an alloy of i part lead, i part tin, 

 and 2 of bismuth, the melting point of lead is 325°C, tin 227'8°C, bis- 

 muth 259°C ; their sum is 8ii, their mean, 270°C. This will melt at 

 ioo°C, which is just I70°C below the mean. Is this not sufficient proof 

 for this law ? Let us take another example, that of an alloy of lead and 

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