Flotation of Minerals. 



567 



of a glass. On addition of acid the hubbies have a tendency 

 to select the sulphides on which to form. Some zinc concen- 

 trates obtained from Central Mine tailings, Broken Hill, by a 

 HoSO^ float were washed well, dried and then floated in water 

 with atmospheres of different gases above the water. 

 Tlie following arrangement of apparatus was used: — 



FigA 



The zinc concentrates were placed in flask B, and boiled for 

 a considerable time till the concentrates sank to the bottom, 

 Tlie flask was then filled to the top with boiling water. Flask 

 C was filled with the gas to be used. The beaker D contained 

 a saturated solution of the gas used, and the beaker A was 

 half filled with air-free water. Some of the water in B was 

 then syphoned into A, the space being taken up with the gas 

 from r. B was then boiled, and shaken up, after closing the 

 clamp E. 



The gases tried were H^S, nitrogen, CO^, SO5, oxygen, hydro- 

 gen, water vapour and air. Flotation took place in every case, 

 the scum formed in the case of H^S having a slightly dif- 

 ferent appearance from the others. Tliis treatment was equiva- 

 lent to boiling the sulphide in a saturated solution of the gases 

 named, and at the same time preventing all the gas being 

 driven off before the solution became hot. 



