NICKEL AND COBALT. 167 



was CoO or NiO respectively. The anhydrous chlorides 

 were prepared from the hydrated salts by ignition in dry 

 chlorine or hydrochloric acid. With cobalt, the monohy- 

 drated chloride, dried at 100°, was also employed. For 

 nickel he gives the following values, referred probably to 

 O = 16, S = 32, Ag = 108, CI = 35.5 : 



From NiSO^ Ni = 58.4 to 59.0 



" NiCl.^ " = 58.4 ^' 59-28 



To cobalt these values are assigned : 



From CoSO^ Co = 58.6410 58.76 



" CoClo.Hp " =58.84 "59.02 



" CoCl, " = 58.72 " 59.02 



That is, contrary to Schneider's view, the two atomic 

 weights are approximately the same. The values for nickel, 

 however, run a little lower than those for cobalt ; a fact 

 which is probably not without significance. Marignac crit- 

 icizes Schneider's earlier paper, holding that the nickel 

 oxalate may have contained some free oxalic acid, and that 

 the cobalt salt was possibly contaminated with carbonate or 

 with basic compounds. In his later papers Schneider rejects 

 these suggestions as unfounded, and in turn criticizes Ma- 

 rignac. The purity of anhydrous NiSO^ is not easy to 

 guarantee, and, according to Schneider, the anhydrous chlo- 

 rides of cobalt and nickel are liable to be contaminated with 

 oxides. This is the case even when the chlorides are heated 

 in chlorine, unless the gas is carefull}^ freed from all traces 

 of air and moisture. 



Dumas' * determinations of the two atomic weights were 

 made with the chlorides of nickel and cobalt. The pure 

 metals were dissolved in aqua regia, the solutions were 

 repeatedly evaporated to dryness, and the residual chlorides 

 were ignited in dry hydrochloric acid gas. The last two 

 estimations in the nickel series were made upon NiClg 

 formed by heating the spongy metal in pure chlorine. In 

 the third column I give the NiCL, or CoCl 2, equivalent to 

 100 parts of silver : 



* Ami. Chem. Pharm., 1 13, 25. i860. 



