OF ARTS AND SCIENCES. 83 



tals of arsenous oxide. The filtrate from these does not yield crystals 

 on standing, but after evaporation upon the water-bath solidities to a 

 greenish gummy mass, readil}'^ soluble in water, often however leaving 

 a residue of arsenous oxide. The solution of this gummy salt gives a 

 white crystalline precipitate with baric chloride. The filtrate from 

 this, after evaporation and standing, yields an abundance of beautiful 

 very pale greenish crystals, which may be redissolved and recrystal- 

 lized without decomposition. In this salt, 



1.1230 gr. lost on heating 0.1126 gr. = 10.03% 

 1.0518 gr. gave 0.3258 gr. SO.Ba = 20.28% BaO 

 0.3919 gr. " 0.0678 gr. AsoO, =17.31% 

 0.5774 gr. " 0.0995 gr. " = 17.23% 



0.9729 gr. " 1.0383 gr. MoO.Ba = 51.74% MoOg 



The analyses lead to the formula 



8 M0O3 . 2 AS2O3 . 3 BaO + 13 aq, 



which requires : 



2241 100.00 99.32 



The arsenous oxide was determined in the first analysis by boiling 

 with a solution of sodic dicarbonate, filtering, and titrating with iodine ; 

 in the second, by direct titrition without previous filtration. The 

 baryta was separated by fusion with sodic carbonate, and weighed as 

 sulphate. The water was found by heating over a radiator until a 

 constant weight was obtained, as it was impossible to ignite with sodic 

 tuugstate without volatilization of arsenous oxide. 



The salt requires a very large quantity of water for solution. The 

 dry salt in fine powder boiled with argentic nitrate gives a beautiful 

 yellow crystalline salt. Thallous nitrate yields, under the same cir- 

 cumstances, a very pale yellow, also crystalline salt. The mercurous 

 salt is pale yellow, but not distinctly crystalline. 



12:5 Arsenoso-DioIi/bdate of Ainmoniiun. — When a solution of 

 zincous sulphate is added to one of the gummy arsenoso-molylxlate of 

 ammonium, no precipitate is found at first, but after a time colorless 



