Flotation of Minerals. 575 



The wetted mineral is placed in tiask D, and the tap and 

 tube E is inserted after filling with air-free water. The capil- 

 lary tube C is filled with air-free water, and wired on to the 

 tap E at F. The Ijurette B is filled with mercury by connect- 

 ing to the water pump, and then the capillary tube C is wired 

 on at H. A screw clip is also used at H for preventing air 

 getting into tube C when the burette B is disconnected. The 

 flask A is then connected to the water pump at P. On lower- 

 ing the pressure in A, the gas in the mineral in flask D is 

 drawn over into the burette B, where it can be caught by 

 closing the tap K. The flask D can be immersed in a water 

 bath and heated. The excess of water drawn over into the 

 burette B from the flask D can be drawn oft' by lowering the 

 pressure in A without allowing any of the gas to escape. 

 Very little gas is lost in solution in the water in this manner, 

 as the water collecting in A is under reduced pressure. 



