80 



Popular Science Monthly 



Froth Flotation Saves Vast Quantities of Base Metals Formerly Wasted 



M>Tiads of glistening, dancing bubbles come surg- 

 ing along the surface of the liciuid, crowding each 

 other in their effort to reach the top with their 

 precious cargo of mineral wealth. When Sulman, 

 Pickard and Ballot discovered the froth process 



liquid itself by violent stirring. The 

 effectiveness of the two methods depends 

 upon the physical characteristics of the 

 ore. 



Even when the mineral-laden bubbles 

 reach the surface and burst, the metal 

 particles are not allowed to sink because 

 the bubbles directly underneath continue 

 to buoy them up. 



The floating of sulphides is greatly 

 assisted by adsorption, which may be 

 briefly defined as the tendency of gases 

 or dissolved substances to cling to the 

 surfaces of solid bodies. This results in a 

 relatively high concentration of the gas 

 or solution at the place of contact. The 

 tiny particles of gas attach themselves 

 to the solid particles, like barnacles to the 

 hull of a boat. This film of gas surround- 

 ing the ore particles does not, of itself, 

 possess sufficient buoyancy to raise the 

 heavy mineral. But when it coalesces, or 

 combines, with a few of the surrounding 

 bubbles, the weight of the mineral is more 

 than offset by the lifting power of the 

 bubbles, and it comes to the surface. In 



now in use, there was at Broken Hill, Australia, 

 a 12,000,000-ton hill of ore which could not be re- 

 covered by ordinary methods. This ore was saved. 

 When this issue reaches you, approximately 40,000,000 

 tons will have been treated since January 1917 



this way, the bubbles "lay to" and to- 

 gether boost an ore particle to the top. 



Carrie Everson's Contribution 



Adsorption was first applied by Carrie 

 Everson, who is regarded as the mother 

 of ore flotation, though she never received 

 any material reward for her discoveries. 

 She added the use of acid to the processes 

 already developed by her predecessors. 

 In her process, the acid, by combining 

 with the metal, was thought to liberate 

 gas which attacked the ore particles and 

 buoyed them up. As a matter of fact, the 

 acid gives the sulphides a clear surface to 

 which the oil will adhere. When left 

 standing, the ores often become oxidized 

 and thus hinder the action of oil in con- 

 centration. 



For years, a story has been told of the 

 accidental discovery of flotation. A Miss 

 Carrie Everson, a sister of an assayer loca- 

 ted in Denver, while washing some dirty 

 sacks, in which concentrate had been sent 

 to her brother, realized that the grease 

 and ore particles floated on the water. 



