ATOMIC WEIGHTS 



231 



To the copper series I add the ratio Cu:Zn:: 100 :.t. 



Mean, 103.22, ± .0261 



Hence Zn = 65.601. 



Eichards and Eogers/ in their investigation of the atomic weight of 

 zinc, studied the anhydrous bromide. This was prepared by solution 

 of zinc oxide in hydrobromic acid, evaporation to drjmess, and subse- 

 quent distillation in an atmosphere of carbon dioxide. In some experi- 

 ments, however, the bromide was heated in an atmosphere of nitrogen, 

 mingled with gaseous hydrobromic acid. All water can thus be removed, 

 without formation of oxybromides. 



The zinc bromide so obtained was dissolved in water and precipitated 

 with a solution containing a known amount of silver in the form of 

 nitrate. The silver bromide was weighed on a Gooch crucible, and the 

 ratio 2AgBr : ZnBr, thus found. An excess of silver was always used, 

 and in one series of experiments it was estimated by precipitation with 

 hydrobromic acid. Deducting the excess thus found from the original 

 quantity of silver, the amount of the latter proportional to the zinc 

 bromide was found ; hence the ratio Ago : ZnBr,. The results, with 

 vacuum weights, are as follows : 



^ Zeitsch. anorg. Chciii., 10, 1. 1S95. 



