324 Kenneth A. Midde : 



flask is completely filled with some of the flotation product, 

 and the flask is then stoppered, on standing it will be noticed 

 that the scum occupies a lesser volume, partly due to cooling 

 and partly to the bursting of the bubbles and disengagement of 

 the gases. For instance, in a large AVinchester quart bottle 

 originally completely filled with the flotation product, on stand- 

 ing the sulphides only occupied about 2 inches on the bottom 

 of the bottle. The remainder of the space (6 inches), except 

 for 5 inches of solution, was occupied by the disengaged gases. 



The different stages of oil and gas adsorptions are analogous 

 to a certain extent. In the case of the latter, where there is 

 insufficient gas to buoy the mineral to the surface, but aggre- 

 gates are formed (such as are brought about by weak chlorine 

 and nitric acid solutions in the cold), there is a similarity to 

 the aggregation stage in oil adsorptions, where a thin second- 

 ary film of oil is attached to the primary film. In the case 

 of gaseous aggregations, flotation can be brought about by 

 increasing the amount of attached gas — e.g., by adding a satu- 

 rated solution of carbon dioxide, the bubbles of the latter gas 

 becoming attached to the aggregates, and buoy them to the 

 surface. 



Thus the stages in producing flotation of a sulphide by oil 

 without the aid of gas are : — 



(1) Primary adsorption film. 



(2) Secondary attachments, which will form aggregates. 



(3) Oily magna formed by excess attachments. 



(4) Oil sufficient to bring about the production of magna 

 of such a specific gravity as w^ll float in water. 



Similarly the stages gone through in bringing about the 

 flotation of a sulphide wnth gas are: — 



(1) Primary adsorption fllm. 



(2) Aggregates formed by secondary attachments. 



(3) Fairly stable aggregates which float by the aid of heat 

 or reduced pressure. 



(4) A scuna or froth containing an excess of gas, which is 

 mostly disengaged by agitation, after buoying the aggregates 

 to the surface. 



