OF ARTS AND SCIENCES. 99 



ever, succeed in obtaining them by the action of hypophosphorous acid 

 upon phospho-molybdates, and the precise conditions necessary are 

 yet to be determined. It appears to be at least probable that classes 

 of phosphoroso-hypophospho-tungstates and phosphoroso-hypophospho- 

 molybdates will sooner or later be discovered. 



ARSENOSO-PHOSPHO-TUNGSTATES. 



The salts of this series are formed when solutions of orthophosphates 

 and arsenoso-tungstates are mixed, and when arsenous oxide is boiled 

 with a solution of an alkaline phospho-tungstate. The alkaline salts 

 are sometimes crystalline and sometimes gummy. The series is prob- 

 ably a very extensive one. 



Analytical Methods. — In these salts the arsenous oxide is best de- 

 termined by titrition with iodine after adding an excess of an alkaline 

 dicarbonate. After separating arsenous oxide as sulphide by sulphy- 

 dric acid, the phosphoric oxide may be determined by magnesia-mixture. 

 Phosphoric and tungstic oxides may be determined together by mer- 

 curous nitrate and mercuric oxide after separating arsenous oxide from 

 the solution as arsenous sulphide, dilute sulphuric acid being employed 

 in place of chlorhydric acid. Water is best determined by heating 

 over a radiator. 



32 : 14 : 3 : 10 Potassic Arsenoso-phosphn-tungstate. — This salt was 

 prepared by boiling potassic phospho-tungstate with an excess of 

 finely pulverized arsenous oxide. The filtered solution had a pale 

 greenish-yellow tint, and after standing twenty-four hours deposited a 

 mass of very minute greenish-yellow crystals. These were filtered off, 

 washed with cold water, and then drained by the filter-pump. The 

 drained mass was greenish yellow, and packed into a gummy solid. 

 The filtrate on evaporation gave a fresh quantity of the same salt, 

 which is rather soluble in cold, and very easily soluble in hot water. 

 Of this salt, 



0.9333 gr. lost by heating over a radiator 0.0398 gr. = 4.27% 

 0.9333 gr. gave 0.6094 gr. WO3 + P.O, = G5.29% 



1.0505 gr. " 0.2413 gr. AsoO., with iodine = 22.97^ 



0.845G gr. " 0.0472 gr. P.O.Mg., = 3.57% 



The analyses correspond fairly well with the formula 



32 WO3 . 14 AsoOj . 3 PoO, . 10 K,0 + 28 aq, 



