232 ACIDIFIABLE COMBUSTIBLES. 



Now, it is evident from this experiment, that 

 19*5 grains of anhydrous binarseniate of soda 

 contain exactly 4 grains of soda ; for the 13*5 

 grains of nitric acid in 41 %5 grains of nitrate of 

 lead require 8 grains of soda to neutralize them. 

 To accomplish this neutralization, (after the 

 oxide of lead had been separated) it was neces- 

 sary to add only 18 grains of carbonate, contain- 

 ing 4 grains of soda ; consequently, 4 grains had 

 been already combined with it, and these 4 

 grains could only have been derived from the 

 binarseniate of soda. 19*5 grains of anhydrous 

 binarseniate of soda, then, are composed of 



Arsenic acid 15*5 

 Soda 4-0 



These 1,5*5 grains of arsenic acid neutralized 28 

 grains of protoxide of lead, which are equivalent 

 to 2 atoms ; consequently, 15*5 grains of arsenic 

 acid must be equivalent* to 2 atoms. Thus, we 

 see that the atomic weight of arsenic acid is 7*75. 

 2. Let us now investigate the constitution of this 



tion of ar- . 



senic acid. acid. Into a small green glass retort, previously 

 weighed and the weight marked upon it with a 

 diamond, 4*75 grains of clean metallic arsenic 

 were introduced, and about an ounce of rather 

 strong nitric acid was poured over it. A moder- 

 ate heat being applied, the arsenic dissolved with 



