Flotation of Minerals., 571 



Specific Gravity of Floated Materials. 



The specific gravity of some zinc concentrates from a Potter 

 (aoid) float was found to be 2.81. The specific gravity of zinc 

 blende is usually about 4. Two other samples of zinc con- 

 centrates from a process in which oil was used had a sp. gr. of 

 2.55 and 2.61 respectivelv. The low sp. gr. noted was due to 

 absorbed gases. 



A sample of some clean crystalline galena was crushed and 

 sifted, and 20 gms. of the material remaining on each sized 

 sieve was taken and added to 100 c.c. water. Half a gm. of 

 oleic acid was then added, and well shaken up with the galena. 

 The specific gravity of each sized mineral was then taken, and 

 resulted as follows : — - 



Spc. Gr. 



On 40 sieve 6.4 



On -60 sieve 6.1 



On 80 sieve ". 6.2 



On lOO sieve 5.8 



On 180 sieve 5.8 



Through 180 sieve (partial float) 3.9 



Same of the finest grained material began to float on violent 

 shaking. The s^^eciflc gravity of galena is 7.4. 



The Adsorption of Gases by Minerals. 



To ascertain if oxygen was absorbed from the air by an 

 acid and oil solution with minerals^ the following test was 

 carried out : — Fifty gm. zinc concentrates were added to 200 c.c. 

 water, and then 2 c.c. H5SO4 and 0.5 c.c. oleic acid was added. 

 This solution was agitated for \ hour, and allowed to stand 

 18 hours in an airtight vessel. An analysis of the gas above 

 the solution showed that it was composed of 14 per cent. COrt. 

 18 per cent, oxygen, and 68 per cent, nitrogen. No H^S could 

 be detected. Blank tests were made with (1) acid, and (2) oil 

 in the same proportion as above, the gas above the solution 

 in each case having the composition of atmospheric air. 

 Another test with clean "alena from Broken H'll. with the 



