568 Kenneth A. Mickle: 



The Action of Chlorine 



If particles of minerals are dropped into chlorine water, 

 "bubbles form on the sulphides if oiled or unoiled, fewer form- 

 ing on quartz and other silicates. Under reduced pressure in 

 chlorine water the galena and zinc blende are thickly coated 

 •with bubbles, the galena being attacked by the chlorine, 

 since the faces rapidly tarnish. Very few bubbles come 

 off the quartz and pyrite. A sample of Broken Hill 

 Proprietary zinc concentrates was washed till free from 

 soluble salts, and stood for half an hour with a dilute 

 chlorine water solution. On analysing the solution it was 

 found that considerable amounts of Pb, Fe, and Zn, and a 

 lesser amount of Al had gone into solution. SO4 was present 

 in the solution, but no free chlorine. With these metals going 

 into solution fiee sulphur must be liberated to some extent. 

 If a sample of Broken Hill tailings is washed with CI water 

 it is noticed that the sulphide particles have a tendency to 

 agglomerate and become buoyant, and are thus well prepared 

 for subsequent flotation either by film flotation or otherwise. 

 If a sample of tailings is shaken up with CI water-, and then a 

 minute amount of some light oil, as petrol or gasolene, is added 

 with a little HjSO^, a good flotation takes place in the cold 

 if calcite is present to evolve CO^- If instead of adding acid, 

 water saturated with carbon dioxide is added, the same result 

 is obtained. On some tailings a good flotation with CI water 

 and H2SO4 is obtained in the cold without the addition of 

 any oil. 



Film Flotation. 



Film flotation is the term used to describe flotation when 

 the mineral separated floats on the surface of the liquid to the 

 depth of the thickness of one particle only, and not as a 

 coherent scum as in the case of the Potter and other processes. 

 In film processes, as the De Bavay, the sidphides, after being 

 wetted, are brought into contact with the air, and fed on to 

 the surface of water, and remain floating as a film and not 

 as a scum. A sample of zinc blende obtained by film flotation 



