COBALT. 47 



excess of oxygen. In order to remove this excess it was 

 melted under a known weight of an acid silicate of lead. 

 The results for cobalt varied from 29.32 to 29.38. The sul- 

 phate was purified by recrystallization. Marignac also ex- 

 perimented on the chloride. The weight of this salt varies 

 greatly with the moisture of the atmosphere when crystal- 

 lized, and attempts to desiccate it usually result in the 

 formation of some insoluble compound. Three analyses of 

 chloride appearing to contain one molecule of water, and 

 dried at 100°, performed by titration with silver solution, 

 gave cobalt at 29.42 to 29.51. Five experiments were made 

 in the same way on chloride either melted in a current of 

 chlorine or of chlorhydric acid gas, or calcined with ammo- 

 nium chloride. These determinations gave from 29.36 to 

 29.42. {Bihl Univ., Arch, des Sciences, \2,) 1, 1858, 374.) 

 [Marignac, in another investigation in the same volume, 

 takes Ag = 108; CI = 35.5.] 



J. Dumas : 59 (0 == 16). 



Determined by five experiments on the titration of cobalt 

 chloride with silver. The mean result for cobalt was 29.542 ; 

 extreme difiPerence 0.09 ; Ag = 108 ; CI = 35.5. The chlo- 

 ride was prepared by dissolving pure cobalt in aqua regia, 

 evaporating in the presence of excess of chlorhydric acid 

 and heating to redness in a current of chlorhydric acid gas. 

 In two of the determinations cobalt from a difiterent lot, 

 which had been heated in a vacuum was employed. [Annal. 

 de Chimie et de Physique, (3,) S5, 1859, 148.) 



W. J. Russell : 58.74 (0 = 16). 



Determined by fifteen experiments on the reduction of 

 cobalt oxide in hydrogen. The value is the mean ; the ex- 

 treme difference is 0.19. To obtain pure cobalt oxide 

 Claudet's salt was prepared, purified by recrystallization, 

 etc., reduced in hydrogen, the metal dissolved in nitric acid 

 and the resulting salt decomposed by heating in a stream 

 of carbon di-oxide. {Chem. Soc. Journ., (2,) 1, 1863, 57.) 



Schneider considers that no sufficient precautions were 

 taken to exclude air in these experiments, and that higher 

 oxides were formed. [Poggend. Annal., 130, 1867, 310.) 



E. VON SOMMARUGA : 60 (O = 16). 



Determined by seven experiments on the reduction of 

 purpureocobaltic chloride in a current of hydrogen. The 

 mean of the experiments is 29.965; four of them give a 



