50 R. H. Lee—Atomic Weights of Cobalt and Nickel. 
The probable error of the mean is here -+-0°0088, and the 
sgt weight of cobalt 59°15, with a probable error of +'146. 
method of analyzing the chloride of purpureocobalt has 
already been described. The results of my analyses are as — 
follow 
No, Salt taken. Cobalt. Cobalt, p.c. At. weight. 
0°9472 gr. 0°2233 gr. 23°575 59°07 
2. 078903 “ 0°2100 * 23°587 59°11 
3 06084 ‘ 071435 “ ' 23°586 59°11 
£ 0°6561 “ 071547 “ 23°579 59°08 
5 0°6988 “ 0°1647 “ 23 ed 59°05 
6 07010 “ 0°1653 “ 23°5 59°09 
Mean, 23° S708 59°09 
The probable error of the mean is here +0°004, and the cal- 
culated atomic weight 59°09, with a probable error of +0146. 
The mean of my eighteen determinations of the atomic atcha 
of cobalt is 59°10. For the sake of comparison I give here the — 
results obtained by other observers, in tabular form, reduced to 
the modern scale of atomic weights : 
Rothhoff, 59°10 Dumas, 59°08 Winkler, 58°99 §& 
Schneider, 60°00 Russell, 58°74 Weselsky, 58°96 F 
. 58°84 to 59°02 
Marignac, 
58°72 to 58°84 Sommaruga, 59°93 Lee, 59°10 F 
EI) 
Nickel—The atomic weight of nickel was also first deter- 7 
82 
mined by Rothhoff* in 1826, by determining the amount of 
chlorine in a weighed quantity of nickelous chioride. A single 
ex _ gave for the equivalent 29-60, a number which is _ 
probably too high, in consequence of the imperfection of the 
processes known at that time for the separation of nickel from 
cobalt. Erdmann and Marchand ees up the subject in 1852.¢ — 
Nickelous oxide prepared by various processes was reduced in — 
a current of hydrogen and the sdb weighed. No data are 
given, but the authors state that their results varied between 
was obtained by reducing ‘the oxide with pure hydrogen. In this 
manner Schneider obtained as the mean of four analyses the 
number 29-02. 
Marignac,§ in ath determined the atomic weight of nickel 
facials precisely 'similar to those employed by him in the 
Pogg. Amn., ci, p. 387. 
Bibliothique Universelle de Geneve, Nouvelle Series, vol. i, p. 373. 
