Flotatio^i of Mivendx. 561 



vite, serpentine would not float. In the case of the sulphides 

 H^S is given off to a greater or lesser extent in every case. A 

 sample of copper matte would not float in acid solution. To 

 show the amount of acid required a small test with a sample 

 of the South Mine, Broken Hill, tailings was carried out, taking 

 10 gms. of the tailings, and 50 c.c. water, and adding different 

 amounts of acid and heating to about 95 deg. C. 



With a .36 per cent. H^SO^ solution no float took place. 



With a .72 per cent. HgSO^ solution a small scum formed. 



With a .9 per cent. H^SOj^ solution a poor float was obtained. 



With a 1.4 23er cent. H^SO^ solution a good float was obtained. 

 These tailings contain much calcite, and therefore use up more 

 acid than most of the other companies' tailings. 



Undtr reduced pressure. — The same lot of crystalline particles 

 tried with water alone were tried under reduced pressure in an 

 acid solution ranging from 1 up to 10 per cent. H2S0^-. The 

 bubbles formed as before, but were of a dift'erent nature, appear- 

 ing to be larger, and coming away from the minerals more 

 readily. Fewer bubbles were on the quartz and gypsum than 

 on the other minerals. In an air-free, dilute H^SO^ solution, 

 on fragments of the various minerals being dropped in bubbles 

 form on their surface. In the case of quartz and rhodonite and 

 the other silicates a few bubbles were carried down, but on 

 shaking these oft" no more fonned. This also was the case with 

 copper foil. Bubbles formed on the sulphides, garnet, and tour- 

 maline even after those first formed were detached. Some 

 cubical fragments of galena were coated with lead chromate and 

 sulphate respectively and immersed in an air-free acid solution, 

 under reduced pressure. Only a very, few bubbles formed on 

 these particles. Most of the sulphides will not float in the cold 

 with dilute acid. The zinc blende in a sample of South Mine 

 tailings kept coming up to the surface, but fell back again. The 

 carbonates are attacked by very dilute acid solutions under re- 

 duced pressure. It is interesting to note that siderite and mag- 

 nesite are attacked by cold acid under reduced pressure. 



Some Broken Hill Proprietary's zinc concentrates, washed free 

 fi-om soluble salts, were boiled in a 2 per cent. H2SO4 solution. 

 The following metals went into solution, Fe, Al, Zn, Mu, and 

 II 2 S was given off. A sample of the working solution from this 



