RICHARDS AND ROGERS. 



ATOMIC WEIGHT OF ZINC. 



169 



was all evaporated to very small bulk, and the excess of silver precipi- 

 tated by hydrobromic acid and weighed upon a Gooch crucible in the 

 same way as the other portion of argentic bromide. By subtracting 

 this excess from the total silver originally weighed out, the weight 

 of silver equivalent to the zincic bromide could be easily found. Great 

 care was taken to exclude daylight, and to carry out all the precautions 

 necessary in accuiate work. The data are given below. 



SECOND SERIES. 

 The Ratio of Zincic Bromide to Argentic Bromide. 



THIRD SERIES. 

 The Ratio of Zincic Bromide to Silver and Argentic Bromide. 



The second series of results, excepting the last determination, is 

 undoubtedly affected by the presence of water in the zincic bromide ; 

 for the methods of drying and transference had not been perfected. 

 The third series was much more carefully made, but even here there 

 was a possibility of the retention of a small amount of water in some 

 of the analyses, hence this result also is probably somewhat too high. 



