ZINC. 



153 



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



Zn. 



.7767 

 .7758 

 .5927 

 .5924 

 .2277 

 .2281 

 .8770 

 .8784 

 9341 

 9347 



Cu. 



.7526 

 .7526 

 5737 

 5737 

 .2209 

 .2209 

 .8510 

 .8510 

 .9038 

 .9038 



Ratio. 



103-13 

 103.08 



I03-3 1 

 103.26 

 103.08 

 103.26 

 103.05 

 103.22 

 103.36 

 103.42 



Mean, 103.22, =fc .0261 



Richards and Rogers,* 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 dryness, 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 oxy bromides. 



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 2 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 Ag 2 : ZnBr 2 . The results, with 

 vacuum weights, are as follows : 



Series A. 



ZnBr. 2 . AgBr. Ratio. 



1.69616 2.82805 59.976 



1.98198 3.3 45o 59-978 



1.70920 2 84949 59-984 



2.35079 3-9'94i 59.978 



2.66078 4-4375 l 59.9 6 i 



Mean, 59.975, .0034 



*Zeitsch. Aiiorg. Chem., 10, i. 1895. 



