[walker] separation OF NICKEL AND COBALT 97 



could be used for the separation of nickel from most of the elements 

 ordinarily met with in the course of chemical analysis. This method 

 was still further developed by Prettner, who compares its accuracy 

 with other methods for the separation and determination of nickel.^ 



As developed by these investigators the precipitation occurs in a 

 hot ammoniacal solution. In case iron be present the addition of 

 tartaric acid is necessary to prevent its precipitation along with the 

 nickel. Most of the nickel separates in a few minutes; but to secure 

 the best results the solution must stand for 24 hours. Not more 

 than 99% of the nickel separates in the first hour. By allowing an 

 interval of 24 hours the error usually does not exceed one half of one 

 per cent of the nickel present. The accuracy of this method is there- 

 fore about the same as that of the red lead method. The time neces- 

 sary for an analysis of the same degree of accuracy is greater in the 

 case of the dimethylglyoxime method. 



University of Toronto. 

 June 3rd, 1915. 



1 Chemiker Zeitung XXXIII, p. 396 and p. 4n. 



