OF ARTS AND SCIENCES. 237 



The structural formula of such an acid will be similar to that 

 already giveu ia the case of the hypophospho-molybdate described. 

 Further investigation may, however, show that the more complex 

 formula must be admitted. I coutent myself with proving that 

 there is at least one class of hypophospho-tungstates. In computing 

 the direct results of the analyses I have assumed that, as in the 

 case of the corresponding molybdenum compounds, the complex 

 2 {Hj . PO . OH} is oxidized to Ffi^ wholly at the expense of two 

 molecules of WO3 reduced to W.,05, which last is then again oxidized 

 to 2 WO3 by heating in air. This assumption appears to be justified 

 by the changes of color observed on heating the salt. The actual loss 

 of weight observed then corresponds to water and hydrogen only, the 

 percentage of hydrogen being calculated from that of P^O^Hg. 



When tungstic hydrate in excess is boiled with a solution of sodjc 

 hypophosphite, it dissolves very readily, giving a pale blue solution 

 which yields on evaporation a thick syrupy liquid. This solution 

 gives precipitates with BaCl.,, NH^Cl, and KBr, and will furnish a con- 

 venient starting-point for further investigation. It does not oxidize 

 readily in the air, even after long standing. A solution of dimethyl- 

 arsinic acid gives with one of 12:5 acid sodic tungstate a beautiful 

 colorless crystalline precipitate. I have not studied this compound, 

 from want of proper facilities for work of the kind. It will, I think, 

 prove to be a dimethyl-arsino-tungstate, coming under the general 

 formula 



m WO3 . 2 {(CHg), . AsO . OH} n Na,0, 



and we may reasonably expect an extensive series of analogous com- 

 pounds, in which other radicals take the place of methyl. 



PHOSPHOROSO-MOLYBDATES. 



Since phosphorous acid is now to be regarded as hydryl-phosphinic 

 acid with the formula 



{H.PO.(OH)J, 



the existence of a class of phosphoroso-molybdates and of phosphoroso- 

 tungstates appeared, to say the least, a probable inference from that 

 of the hypophospho-compounds already described. 



Phosphoroso-mohjhdate of Ammonium. — When a solution of phos- 

 phorous acid — as prepared by the reaction of phosphorous chloride with 

 water — is added to one of 14: 6 acid ammonic molybdate, a very pale 

 yellow indistinctly crystalline precipitate is formed, which is insoluble 



