SILVER, POTASSIUM, ETC. 21 



sake of completeness. It will obviously receive but little 

 weight in our final discussion. 



In estimating the atomic weight of bromine the earlier 

 experiments of Balarcl, Berzelius, Liebig, and Lowig may all 

 be rejected. Their results were all far too low, probably be- 

 cause chlorine was present as an impurity in the materials 

 employed. Wallace's determinations, based upon the anal- 

 ysis of arsenic tribromide, are tolerably good, but need not 

 be considered here. In the present state of our knowledge, 

 Wallace's analyses are better fitted for fixing the atomic 

 weight of arsenic, and will, therefore, be discussed with ref- 

 ference to that element. 



The ratios with which we now have to deal are closely 

 similar to those involving chlorine. In the first place there 

 are the analyses of silver bromate by Stas.* In two careful 

 experiments he found in this salt the following percentages 

 of oxygen : 



20.351 



20.347 



Mean, 20.349, zh .0014 



There are also four analyses of potassium bromate by 

 Marignac.f The salt was heated, and the percentage loss of 

 oxygen determined. The residual bromide was feebly alka- 

 line. We cannot place much reliance upon this series. 

 The results are as follows : 



28.7016 

 28.6496 

 28.6050 

 28.7460 



Mean, 28.6755, ± .0207 



When silver bromide is heated in chlorine gas, silver 

 chloride is formed. In 1860 Dumas| employed this method 



* Aronstein's Translation, pp. 200-206. 



f See E. Mulder's Overzigt, p. 117; or Berzelius' Jahresbericht, 24, 72. 



J Ann. Chem. Pharm., 113, 20. 



