310 Kenneth A. Miclde: 



sulphuric acid was added. Tlie appearance and character of the 

 products formed after agitating vigorously differed from one 

 another. The aggregations formed in the acidulated solution 

 were less flocculent and showed less tendency to float on agitation. 



Silicates and othep gangue minerals: — In ivater. 



The various silicates and other gangue constituents of sul- 

 phide ores when agitated with various proportions of oil and an 

 excess of water exhibit a lesser tendency to attach the oil than 

 the various metallic sulphides. This tendency to attach oil in 

 preference to water is very small in the case of the more acidic 

 minerals, and so great in the case of the more basic minerals 

 that their behaviour approaches that of some of the metallic 

 sulphides. For instance, with 40 gins, of quartz or orthoclase 

 felspar, 5 gms. of oleic acid and 200 gms. of water, nearly the 

 whole of the oil will separate and float on the surface of the 

 water, and the mineral particles sink in the water without any 

 sign of aggregation, a few scattered blobs of oil only being 

 carried down with the mineral. On the other hand, with 

 similar proportions of rhodenite and garnet, oil and water, the 

 minerals unite with the oil to form coherent aggregations, and 

 no oil separates as in the case of quartz and felspar. 



Calcite also produces coherent aggregations with oil which, on 

 agitation, readily attach air bubbles. 



In (icidulated solutions. 



The addition of small proportions of acid (0.5 gm. sulphuric 

 acid) to the water in all cases lessens the oil attachment. For 

 example, on agitating the above proportions of quartz and oleic 

 with acidulated water the quartz behaves as if no oil were pre- 

 sent. This is also the case with orthoclase felspar. 



With rhodonite and oleic acid, with acidulated water in the 

 same proportions as before, free oil separates and floats on the 

 surface of the solution. The product is a sandy pulp which is 

 freely miscible with the solution. This pulp has an appearance 

 very different from the product formed with the non-acidulated 

 water, oil and rhodonite in the same proportions. With mix- 



