MancJiester Memoirs, Vol. xlvii. (1903), No. IJJ. 



XII. I. On a Higher Oxide of Cobalt. 11. A Method 

 for the Volumetric Determination of Cobalt. 



By R. L. Taylor, F.C.S., F.I.C. 



Received and irad March 31st, igoj. 



I. On a Higher Oxide of Cobalt. 



In a paper read before this Society last year,* I 

 described a rapid method for the separation of cobalt 

 from nickel. This method, which is a modification of 

 Rose's, consists in mixing the somewhat dilute but per- 

 fectly neutral solution of the two metals with barium or 

 calcium carbonate and an excess of bromine water, and 

 allowing to stand, with occasional shaking, for about five 

 or ten minutes, when the cobalt is precipitated as a black 

 oxide. I pointed out that Rose's original method was 

 unsuccessful because he used a solution which was 

 strongly acid, and 1 showed that the precipitation of the 

 cobalt was greatly retarded by the carbonic acid which 

 was produced by the action of the free acid upon the 

 added carbonate. 



At that time I had in my mind the idea that, if the 

 composition of the precipitated oxide was uniform, it 

 would be possible to use the reaction as a means for the 

 volumetric determination of cobalt by the method indi- 

 cated by Bunsen.f This depends upon the fact that any 

 oxide of cobalt higher than the monoxide CoO would 

 dissolve in a mixture of hydrochloric acid and potassium 

 iodide, liberating an amount of iodine which would 



* Memoirs^ Vol. xlvi., (1902), No. 11. 

 \ Ann. Chem. Pharm., LXXXVL, 265. 



July JOth, igoj. 



