274 SALTS 



1 atom arsenic acid 7*75 



1 atom soda . 4 



8 atoms water . 9 



20-75 



|Q. Bmarseniate of soda. I formed this salt 

 by adding to a solution of 20*75 parts of arseni- 

 ate of soda, 7*7^ parts of arsenic acid. The so- 

 lution does not crystallize readily ; but by per- 

 severance I obtained crystals of the bisalt to the 

 very last drop. 



This salt, as Mitcherlich has shown, has the 

 same form with biphosphate of soda. The crys- 

 tals redden vegetable blues, and do not undergo 

 any visible change from several weeks' exposure 

 to the air ; they are exceedingly soluble in water ; 

 when heated, they do not, like arseniate of soda, 

 undergo the watery fusion. 25*125 grains of 

 these crystals were exposed to a heat slowly 

 raised to redness : the salt fused into a white 

 enamel, and lost 5*625 grains of its weight. It 

 is obvious from this, and from the method of pre- 

 paring it, that the constituents of the salt are 



2 atoms arsenic acid 15-5 



1 atom soda . . 4 

 5 atoms water 5 625 



25-125* 



* The analysis of the arseniate of soda, which I puhlished some years 

 ago in the Annals of Philosophy, Vol. XV. p. 82, is very incorrect. I 



9 



