OF ARTS AND SCIENCES. 79 



of arsenous oxide in quantity. It is well known that alkaline hydrates 

 also dissolve arsenous oxide in a proportion more than sufficient to 

 form definite salts, and that the solutions deposit crystals of arsenous 

 oxide on standing. 



9 : 1 Ammonic Arsenoso-tungstate. — A boiling strong solution of 

 12:5 sodic tuugstate dissolves arsenous oxide very readily, and in 

 large quantity. The solution on evaporation gives a colorless or very 

 pale yellow thick gummy mass, which on re-solution leaves octahedral 

 crystals of arsenous oxide. The solution of the sodic salt gives with 

 ammonic chloride, after standing some time, beautiful imle yellow 

 almost colorless prisms. These may be redissolved and recrystallized 

 without decomposition. Of this salt, 



1.2699 gr. lost on ignition 0.2750 gr. = 21.65% H^O, AsjOj, and NHg 

 1.3508 gr. gave by titrition with iodine 0.1034 gr. AsjOg = 7.65% 

 1.9457 gr. " 0.2713 gr. NH.Cl = &J^% (NHJ^O 

 0.9776 gr. « 0.7732 gr. ^¥©3= 79.09% by Hg^ (N03)2 and ignition. 



The analyses lead to the formula 



18 WO3 . 2 AS2O3 . 7 (NHJ2O + 18 aq, 



5260 100.00 



The salt may of course be regarded as a double salt, but in this 

 class of salts, as in the arseuio-tungstates and phospho-tungstates, I 

 am disposed to think that in all cases we have an even number of 

 molecules of tungstic oxide united with at least hvo molecules of ar- 

 senous oxide. Further investigations are of course required to settle 

 this question. Meantime, from the analogy of the baric salt, we may 

 write the formula provisionally as 



9 WO3 . AS2O3 . 4 (NIIJoO + 9 WOg . AS2O3 . 3 (NHJoO + 18 aq. 



9 : 1 Baric Arsenoso-tungstate. — A solution of sodic arsenoso- 

 tungstate obtained as above gives a white crystalline precipitate with 

 baric chloride which is nearly insoluble in water, and which was there- 



