Flotation of Minerals, Part II. 317 



filled with a saturated solution of carbon dioxide and standing 

 in a basin of the same solution. Bubbles of carbon dioxide 

 gas were at once evolved from both pieces of mineral, Tlie 

 bubbles on the oiled fragment grew to a larger size, and were 

 held more tenaciously, but more gas was given off from the 

 unoiled piece, as could be directly measured by the amount of 

 solution displaced in the funnel. 



These results show that the oil probably acts as an agent 

 by which the gas bubbles are more tenaciously attached, but 

 that it is the mineral itself which in the first place determines 

 the gas attachment. 



4, Some Broken Hill jig tailings were treated with dilute 

 sulphuric acid, and afterwards with water, to separate the 

 whole of the aeid. On immersing in a saturated solution of 

 carbon dioxide, bubbles of carbon dioxide gas collected on the 

 sulphide particles, but except in the case of a few garnet par- 

 ticles, they did not collect on the gangue. On dealing similarly 

 with the same tailings without the acid treatment, bubbles of 

 carbon dioxide collected on all the particles, there being no 

 marked distinction between the sulphide particles and the 

 gangue particles. This shows that the acid treatment tends to 

 prevent gas attachment in the case of the gangue particles, 

 while it does not to the same extent similarly prevent gas 

 attachment in the case of the sulphides. 



5. Some of the flotation product produced at one of the 

 Broken Hill mines by agitating zinciferous tailings with an 

 acidulated solution, and a small proportion of oleic acid, were 

 collected, as it came to the surface of the solution. This .product 

 was collected in a bottle until the bottle was completely filled, thus 

 displacing the air. The bottle was then stoppered, and the gas 

 contained in the flotation product gradually became disen- 

 gaged as the sulphide settled down. An analysis was made of 

 this disengaged gas, with the following results : — 



(1) Analysis of gas disengaged from first sample: — Nitrogen, 

 72 per cent. ; oxygen, 2 per cent. ; carbon dioxide, 26 per cent 



(2) Analysis of gas disengaged from second sample : —Nitro- 

 gen, 82 per cent. ; oxygen, 2 per cent.; carbon dioxide, 16 per 

 cent. 



