566 Kenneth A. Miclde : 



being free from air. On making acid with H2S0^ very few 

 bubbles remained on an}- of the minerals, but more were on the 

 sulphides than the quartz and silicates. 



Behaviour of Minerals and Metals in saturated 

 Solutions of Gases. 



In water saturated with CO.^^. — Copper foil and other metals 

 and also all the minerals constituting the Broken Hill tailings 

 will float in water saturated with CO^, being brought to the 

 surface repeatedly by the CO^ bubbles. Bubbles form on all 

 the minerals, and are not confined to the sulphides. Very few 

 form on g}'psuni and fewer on the quartz than on the sulphides. 

 On addition of H2S0j^ no bubbles remained on the gypsum and 

 very few on the quartz, the garnet still having bubbles attached 

 to it. The action is similar with a saturated solution of SO2. 

 Hydrogen peroxide is also similar in its action to the saturated 

 solutions. Tlie manner in which bubbles of gas are formed in 

 a solution is very important as regards their subsequent attach- 

 ment to the minerals. A very rapid current of bubbles may 

 be evolved, but the bubbles may not attach themselves to 

 mineral particles, and thus may not be of any use in their 

 subsequent flotation. Sometimes the rapid evolution of a gas 

 is useful as in the case where flocculent masses of the sulphides 

 are held together by gas bubbles insufficient to carry them to 

 the surface, and the rush of bubbles to the surface getting 

 underneath these agglomerated sulphides causes them to be 

 carried to the surface. The condition that seems to be the best 

 for the attachment of the gas bubbles to minerals and metals 

 is when a saturated solution is slowly evolving bubbles of gas 

 that are being thrown out of solution by rise of temperature, 

 or lowering of pressure. This takes place to a certain extent 

 in all the flotation processes where a hot solution is used, the 

 dissolved air, COo, HgS and any other gases in solution being 

 driven out when the temperature is raised. In the case of 

 saturated solution of gas, bubbles will form on almost anything 

 introduced into the solution. A common example is the foi'ma- 

 tion of l)ul)bles on pieces of cork in soda water and on the sides 



