R. H. Lee—Atomic Weights of Cobalt and Nickel. 51 
ease of cobalt already cited. His analyses of the sulphate of 
nickel gave results varying from 29-2 to 29°5, while those of the 
chloride gave results varying between 29-4 and 29°64. Marignac 
does not give his method of obtaining pure salts of nickel. 
The subject was next investigated by Dumas,* who deter- 
mined the quantity of chlorine in nickelous chloride, and ob- 
tained for the equivalent of nickel as a mean of five analyses 
the number 29514. The author does not give the process by 
which the nickel was obtained free from cobalt. 
Russell+ took up the subject of the atomic weight of nickel, 
together with that of cobalt, in 1868. Pure nickelous oxide 
was first ignited in a current of carbonic di-oxide, and after- 
ward in pure hydrogen. His results were as follows: 
lst specimen, mean of 3 determinations 100 parts of oxide, gave 78°596 Ni. 
> ee “ “ “ “ “ 78584 
3. “ “e ts ‘“ “ 78598 “ 
4.4 ‘“ “ “ “ “ 78592 * 
The mean of all the determinations gave for the quantity of 
nickel in 100 parts of the oxide 78°5925, and for the atomic 
weight of. ni¢kel 58-74. : 
In 1866, Sommaruga§ determined the atomic weight of nickel 
by ascertaining the quantity of sulphuric acid in pure crys- 
tallized double sulphate of nickel and potassium. The mean of 
Six analyses gave for the equivalent of nickel the number 
-29°018, with a probable error of +0-079. 
Winkler,| in 1867, employed the method of reduction already 
~ described. The mean of four analyses gave for the equivalent 
____ 29°527, with a probable error of 0-056. 
_ With these preliminary statements I pass to an account of 
ty own methods and results. Metallic nickel of commerce was 
issolved in nitro-sulphuric acid, and the nitric acid eee by 
e traces 
of copper and arsenic removed by a long continued current of 
sulphydric acid gas. The iron in the filtrate was then oxydized 
; € vy I 
nickelous sulphate then converted into nickel-cyanide of potas- 
* Ann. de Chimie et de Physique, 3d series, vol. lv, p. 148. 
+ Ann. der Pharmacie, vol. exxvi, p. to 336. 
Second purification. : 
' Sitzungsberichte der Weinen Akad., vol. liv, p. 50. 
| Zeitschrift fiir Analyt. Chemie, 1867, p. 18. 
