312 Kenneth A. Miclde: 



In acidulated solutions. 



1. The sulphides will adsorb oil in the same manner to form 

 oily magmas, plastic masses and coherent aggregations, as in the 

 case of waiter and oil without acid. The amount depends on the 

 extent of surface exposed by the minerals, as previously. 



2. The gangue minerals will not adsorb oils to nearly the 

 same extent as when no acid is present. 



3. The maximum amount of oil adsorbed by sulphides in a 

 stable manner when crushed to pass through an 80-mesh sieve 

 (linear inch) is in the neighbourhood of 10 to 15 per cent, of 

 their weight. This is shown by the absence of excess of oil on 

 the surface of the solution in the above tests when the percentage 

 of oil to mineral was at or near these values. The tendency of 

 the plastic magma to break up and form less coherent aggregates 

 at this point also indicates this limit of true adsorption. 



Conclusions. 



When finely divided metallic sulphides are vigorously agitated 

 with an excess of water and a small proportion of oil, the oil is 

 adsorbed by the sulphide particles. As shown by the previous 

 tests on the sized material, the quantity of oil adsorbed depends 

 upon the extent of the surface exposed. This being so, it seems 

 safe to assume that the adsorbed oil is evenly distributed over 

 the surface of the particles. When the quantity of oil adsorbed 

 is very small, the general appearance of the sulphide does not 

 differ from that of unoiled particles. With a sulphide such as 

 galena, which has been crushed to pass through an 80-mesh 

 (linear inch) sieve, this point of apparent difference is reached 

 when the proportion of oil adsorbed (in the case of oleic acid) is 

 between 0.05 and 0.10 per cent. Even with these small pro- 

 portions, various physical tests indicate that the particles are 

 oiled. This can be shoAvn by their aversion to become .wetted by 

 water, and by the fact that the odour of decomposed oil is 

 noticed on heating. 



Such a quantity as 0.1 per cent, cannot be separated by squeez- 

 ing, centrifugal force or other mechanical means, and any such 

 quantity of adsorbed oil as 0.1 per cent, may be regarded as a 



