436 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



From the same point of view — that is, with reference to the supposed 

 heterogeneity of nickel— Kriiss and Schmidt^ carried out a series of frac- 

 tionations of the metal b}^ distillation in a stream of carbon monoxide. 

 Nickel oxide, free from obnoxious impurities, was first reduced to metal 

 by heating in hydrogen, after which the current of carbon monoxide was 

 allowed to flow. The latter, carrying its small charge of nickel tetra- 

 carbonyl was then passed through a Winkler's absorption apparatus con- 

 taining pure aqua regia, from which, by evaporation, nickel chloride was 

 obtained, and from that, by reduction in hydrogen, the nickel. Ten 

 such fractions were successively prepared and studied; first, by prepa- 

 ration of NiO and its reduction in hydrogen; and, secondly, in some 

 cases, by the reoxidation of the reduced metal, so as to give a synthetic 

 value for the ratio Ni : 0. The data obtained are as follows, the successive 

 fractions being numbered : 



> Zeit. anorg. Cliem., 2, 235. 1892. 



