n 



ESTIMATION OF OXYGEN IN WORKING 

 CYANIDE SOLUTIONS 



It is a well-known fact that in the cyanide process, as ordi- 

 narily used, the solution must contain oxygen in order to dissolve 

 the gold. Realizing the importance of this, about ten years ago 

 the Chemical and Metallurgical Society of South Africa offered a 

 gold medal to anyone who should find a method of actually deter- 

 mining the oxygen in a working cyanide solution. This medal was 

 awarded to Mr. Andrew F. Crosse, in January, 1899. 



The following description of his method is adapted and con- 

 densed from Mr. Crosse's articles published in Volume 2 of the 

 Transactions of the Chemical and Metallurgical Society of South 

 Africa, pages 396, 419, and 476. 



ESTIMATION OF OXYGEN IN WORKING CYANIDE SOLUTIONS. 



By A. F. Ceosse. 



The ordinary working cyanide solution contains substances 

 which prevent the direct application of Thresh's well-known 

 method for the determination of oxygen dissolved in water, as de- 

 scribed in Sutton's Volumetric Analysis, pages 277-283. By pre- 

 liminary treatment, however, these substances can be either re- 

 moved or neutralized without affecting the oxygen present in the 

 solution, leaving it amenable to Thresh's method. This method is 

 based on the fact that iodine is liberated when potassium nitrite 

 and sulphuric acid are brought together in water containing free 

 O, 16 parts of O liberating 254 parts of I. 



Apparatus Necessary: 



1 "Winchester quart" white glass bottle, with accurate fitting 



glass stopper and of known capacity — about 1\ litres. 

 1 smaller glass bottle — 16 oz. 

 1 50 cc. burette, for ZnS0 4 solution. 



1 rubber stopper with two holes, to fit large bottle. 



2 293 cc. Thresh's separatory tubes, ground glass stoppers. 



