RICHARDS AND BAXTER. — ATOMIC WEIGHT OF COBALT. 63 



A small quantity of alkaline chloride was found in the residual cobalt, and 

 was determined in the usual way by lixiviating the metal and evaporating 

 the solution. This correction was of course subtracted from the original 

 weight of the cobaltous chloride, as well as from that of the metal. 



In the following table of results the specific gravity of cobaltous chlo- 

 ride is Assumed to be 2.94, the value given by Joule and Playfair.* This 

 necessitates a correction to the vacuum standard of +.000262 gram per 

 gram of chloride. Cobalt itself has a specific gravity too near that of 

 brass to need any correction of this kind. CI = 35.455. 



As the alkali had not been completely removed by the process of 

 crystallization to which the cobaltamine had been subjected, it is highly 

 probable that some silica also remained which was not removed from the 

 metal by leaching. This probability, together with the fact that the 

 ammonic chloride correction is undoubtedly somewhat too large, seems 

 sufficient to account for the fact that these results are slightly higher 

 than those obtained in the bromide series (58.995). At any rate the 

 evidence of this method is that the atomic weight of cobalt cannot be 

 greater than 59.05, for none of the probable errors would tend to make 

 this result too low. 



II. The Reduction of Cobaltous Oxide. 



At this point experimental difficulties in the preparation of the chlo- 

 ride, together with the belief that silica could not be completely removed 

 from the salt without introducing platinum, led to a search for a more 

 satisfactory method. In the hands of the early experimenters upon the 

 atomic weights of nickel and cobalt, reduction of the monoxide yielded 

 good results, — results less satisfactory in the case of cobalt than in that 

 of nickel, however, on account of the greater difficulty in preparing the 

 monoxide in a pure state. 



Russell, f the first investigator to work with cobaltous oxide, found that 

 the higher oxides of cobalt were reduced to the monoxide hy heating to 



* Landolt and Bornstein, Tabellen (1894), p. 134. 

 t Jour. Chem. Soc. (2.), I. 51 (1863). 



