9-i PROCEEDINGS OP THE AMERICAN ACADExMY 



to the solution an alkaline tartrate, and then to render it alkaline with 

 an excess of sodic bicarbonate. The antimonious oxide may then be 

 determined by titrition with iodine. 



17:3 Animonic Antimonoso-moli/bdate. — This salt crystallizes from 

 a solution of antimonious oxide in 14 : 6 ammouic molybdate, in pale 

 greenish-yellow granular ci'ystals, but its preparation is rather uncer- 

 tain. It is insoluble in cold water : for analysis, the crystals were 

 simply washed and dried upon woollen paper. In this salt, 



0.7474 gr. gave by titrition with iodine 0.1618 gr. SboO. = 21.65 % 

 0.5287 gr. " 0.0399 gr. (NH^).© = 7.55 % 

 1.0869 gr. lost on ignition with MoO^Nag and WO^Nas 0.1851 gr. = 

 17.03 %. 



The analyses lead to the formula 



17 M0O3 . 3 SbaOs . 6 (NH4)„0 + 21 aq, 

 which requires : 



The molybdic oxide is estimated by diffei'ence. The solution from 

 which this salt of ammonium separated gave, after twenty-four hours, 

 a tine yellow crystalline precipitate with maugauous sulphate. The 

 formula given may be reduced to the type 



18 MoOg . 2 SboOg . 6 (Nn,).,0 + 21 aq, 



if we assume that one molecule of SboO., plays the part of, or replaces, 

 one molecule of molybdic oxide. In determining the water in this 

 salt I employed a mixture of equal molecules of sodic tungstate and 

 molybdate, which fuses at a temperature below that at which molybdic 

 oxide is given off. 



In formulating the arsenoso-tungstates and arsenoso-molybdates 

 I have assumed provisionally that normal arsenites are represented by 

 one or another of the three general formulas 



AsoOg . R.O, As„0, . 2 RoO, As.^Og . 3 R.0, 



the three plumbic arsenites forming appropriate special instances. 

 This view would establish a broad line of distinction between arsenites 



