298 THE ATOMIC WEIGHTS. 



was prepared, which, after sublimation in dry chlorine, was also reduced 

 by hydrogen. One hundred parts of gold are precipitated by the quanti- 

 ties of niclvel and cobalt given in the third columns respectively. In tlie 

 cobalt series I include one experiment by Weselsky, which was published 

 by liiin in a paper presently to be cited : 



•4360 grm. nickel precipitated .964S grm. gold. 45.191 



•4367 " .9666 " 45.179 



•5189 " I. 1457 " 45-291 



.6002 " 1.3286 " 45.175 



•5890 grm. cobalt precipitated 1.3045 grm. gold. 

 •3147 " .6981 



.5829 " I. 2913 



.5'ii " 1.1312 " 



.5821 " 1.2848 



•559 " I. 241 



Mean, 45. 151, dr .025 



Weselsky's paper,* already quoted, relates only to cobalt. He ignited 

 the cobalticyanides of ammonium and of phen3dammonium in hydrogen, 

 and from the determinations of cobalt thus made deduced its atomic 

 weight. His results are as follows : 



•7575 gi'm. (NH^)gCo.^Cyj2 gave .166 grm. Co. 21.914 per cent. 



■SH3 " .113 " 21.972 " 



Mean, 21.943, =t .029 



.8529 grm. (CgIl8N)6'^02'^yi2 g''^^^ .1010 grm. Co. 11.842 per cent. 



.6112 " .0723 " U.829 " 



.7140 " .0850 " 11.905 " 



.9420 '« .1120 " 11.890 " 



Mean, 11.8665, ± .0124 



Next in order is the work done by Leef in the laboratory of Wolcott 

 Gibbs. Like Weselsky, Lee ignited certain cobalticyanides and also 

 nickelocyanides in hydrogen and determined the residual metal. The 

 double cyanides chosen were those of strychnia and brucia, salts of very 

 high molecular weight, in which the percentages of metal are relatively 

 low. A series of experiments with purpureocobalt chloride was also 

 carried out. In order to avoid admixture of carbon in the metallic resi- 

 dues, the salts were first ignited in air, and then in oxygen. Reduction 

 by hydrogen followed. The salts were in each case covered by a porous 

 septum of earthenware, through which the hydrogen diffused, and whicli 

 served to prevent the mechanical carrying away of solid particles ; fur- 



*Ber. d. Detitsch. Chem. Gesell., 2, 592. 1868. 

 t Am. Journ. Sci. and Arts (3), 2. 44. 1S71. 



