842 PROCEEDINGS OF THE AMERICAN ACADEMY. 



criticism one should rather classify the investigations according to the 

 methods used in them. 



The most direct method of determining the atomic weight of nickel is 

 obviously the reduction of nickelous oxide, for in this way the ratio 

 between nickel and oxygen, the usually accepted standard of atomic 

 weights, is settled at once. Russell, Zimmermann, Mond Langer and 

 Quincke, Schlitzenberger, and Krtlss and Schmidt * used this method 

 with varying degrees of success. Of these five investigations the third 

 was hastily undertaken only to show that nickel which has been vapor- 

 ized as nickelcarbonyl is essentially similar to the ordinary material ; 

 the fourth included only two determinations made with oxide undoubt- 

 edly containing traces of sulphate, and the last was hopelessly faulty for 

 reasons already discussed. Hence as exact criteria we may reject these 

 three at once, and turn back to the much more carefully executed work 

 of Russell and Zimmermann. 



Russell showed that when the higher oxides of nickel and cobalt are 

 ignited in an inert atmosphere, oxygen is driven off and the monoxide re- 

 mains. His materials were contained in a Rose crucible of platinum ; and 

 after igniting the oxides in a stream of carbon dioxide, he reduced tliem in 

 a stream of hydrogen. His nickelous oxide was very carefully freed from 

 all extraneous matter except the insidious impurities derived from his 

 glass vessels, against which no precautions were taken. A careful study 

 of his work shows that this is the most serious cause of error likely to 

 affect his final result, but that it was probably in part counteracted by the 

 presence of occluded gases in the oxide ; l^ence we have good reason to 

 believe that this result is probably somewhat, but not much, too high. 



Zimmermann followed essentially the same method as Russell. From 

 ten exceedingly concordant analyses he deduced the value 58.694t for 

 nickel, a value slightly lower than Russell's 58.743. His work also was 

 carried out with great care, and the effort was made to avoid the occlu- 

 sion of alkaline impurities by precipitating the final hydroxide of nickel 



Result. 

 * 1863 Russell, Jour. Cliem. Soc, [2], I. 51, Ni = 58.743 



1886 Zimmermann, Annalen (Liebig's), CCXXXII. 324, Ni = 58.694 

 1890 Mond, etc. Jour. Cliem. Soc, LVII. 753, Ni = 58.580 



1892 Scliutzenberger, Compt. Rend., CXIV. 1149, Ni = 58.515 



1892 Kriiss and Schmidt, Zeitschr. Anorg. Cliem., 11. 235, Ni = 57.5 to 64. (!) 

 t Kriiss and Alibegoff, who published Zimmermann's result, after his death, 

 unwisely omitted to apply the correction to the vacuum standard. This omission 

 has been supplied above. 



