Flotation of Minevdls, Part 11. 305 



The adsorption of oil by minerals. 



The effect of oils has long been known in protecting- minerals 

 from being wetted by Avater, owing to the oiling of their sur- 

 faces, and also the affinity of oils for metals and many metallic 

 substances. As no accurate method of measuring this affinity 

 or attraction has suggested itself, and as minerals may occur in 

 many different forms with varying jDhysical characters, no 

 attempt is made here to make a definite classification on this 

 basis. Tests were, however, carried out to show the amount of oil 

 absorbed by minerals, and the character of the resultant pro- 

 duct. 



Mixtures of the mineral to be tested, water, and oil (with and 

 without a small quantity of acid) in definite quantities were 

 taken and agitated thoroughly till the character of the resultant 

 product became constant. 



The results of these tests showed that while there are un- 

 doubtedly differences in the degree of attraction between a given 

 sulphide and various oils, and between various sulphides and a 

 given oil, the general behaviour between various sulphides and 

 various oils in the presence of water is practically the same in 

 characer, i.e., all sulphides will become attached to all oils in 

 preference to water. With the silicates and other rock minerals 

 usually found in the gangue material of ores, the character of 

 the product varies with different minerals. 



In the case of sulphides, bottles were taken containing 200 

 c.c. water, 5 gms. of the oil being used, and 0.5 gm. sulphuric 

 acid. Increasing amounts of the sulphides were added to each 

 bottle, and well agitated to bring the mineral into intimate 

 contact with the oil. 



The following is a summary of the results obtained from these 

 experiments : — 



In acidulated solution. 



In the first test zinc blende crushed to pass a 40-mesh sieve 

 was used with a heavy engine oil. 



The contents of the bottles were as follows: — 



Water, 20 c.c. ; oil, 5 gm. ; sulphuric acid, 0.5 gm. 



