136 PROCEEDINGS OF THE AMERICAN ACADEMY 



1959 100.00 



The salt dissolves readily in alkaline hydrates. Its chief interest 

 lies in the fact that it serves to establish the existence of a 6-atom 

 series of arsenio-tungstates. 



Acid 6 : 4 Ammonium Salt. — When amnionic arsenate AsO^NH^ 

 and neutral sodic tungstate are dissolved together, no precipitate is 

 formed at first, but after a short time a dense white crystalline salt is 

 thrown down, which after twelve hours becomes abundant. Boiling 

 water dissolves this salt readily, but it does not crystallize well from 

 the solution, forming only a thick white mass. If this mass be 

 dissolved in water, nitric acid added in excess gives a white crystalline 

 precipitate, but slightly soluble in the acid liquid and in water. Of 

 this salt, after washing with cold water, — 



0.8255 gr. gave 0.6013 gr. WO3 = 72.84% 



1.9486 gr. " 0.3980 gr. As,0,Mg2(NIIj2 + Hp = 12.36% As,0. 

 1.2494gr. " 0.2635 gr.NH.Cl =10.25% 



The analyses agree — though not very closely — with the formula 



6 WO3 . AS2O5 . 4 (NHJ2O . 2 H^O + 3 aq, 

 which requires : — 



1920 100.00 



The differences are, I think, not greater than may be expected in 

 cases in which the salt analyzed cannot be purified by recrystalliza- 

 tion. 



Normal 16 : 6 Silver Salt. — I obtained this salt by the following 

 process : 100 gr. neutral sodic tungstate and 25 gr. arsenic acid were 

 dissolved together and the solution boiled for some time, then filtered 

 and evaporated upon a water-bath. After a day much sodic arsenate 

 separated in crystals. The filtrate from these crystals deposited a 



