134 PROCEEDINGS OP THE AMERICAN ACADEMY 



the calculated quantity of pure phosphoric acid, but the experiment 

 was unsuccessful. 



AVhea a solution of hydro-disodic phosphate is heated, and freshly 

 prepared tungstic oxide is added, in small portions at a time, the oxide 

 is readily dissolved with formation of a colorless or faintly bluish liquid. 

 The solution gave crystalline precipitates with baric chloride and 

 argentic nitrate, but the salts formed proved on analysis to be only mix- 

 tures. An ammonium salt was prepared by adding ammonic nitrate 

 and nitric acid to the solution of the sodium salt. The ratio of tung- 

 stic to phosphoric oxide in the white crystalline salt formed was as 

 20:1 very closely ; but this does not lead to any inference as to the 

 formula of the sodium salt in solution. Tribasic sodic phosphate also 

 dissolves tungstic oxide readily, and the same is true as regards am- 

 monic phosphate ; but I could not obtain definite salts from either 

 solution. Potassic phosphate dissolves tungstic oxide very slowly, 

 and only by long boiling. No definite compound was formed in this 

 case. 



When hydro-disodic phosphate and tungstic oxide are fused together 

 the latter dissolves and forms a colorless fused mass. This is soluble 

 in water, but, as in the other cases, gives no single well defined salt. 

 I have made no experiment to determine whether phospho-tung- 

 states of the lower orders dissolve freshly precipitated tungstic oxide 

 so as to form the higher terms in the series. The extraordinary 

 amount of time and labor which I have already spent upon the subject 

 must be my excuse for leaving this and many other interesting points 

 to other investigators. There is no part of the subject which will no* 

 amply repay a new and careful study. 



ARSENIO-TUNGSTATES. 



When solutions of alkaline tungstates and arsenates are mixed it 

 frequently happens that white crystalline precipitates are formed, the 

 supernatant liquid becoming strongly alkaline. These precipitates are 

 arsenio-tungstates, and, as might be expected, correspond in a general 

 way to the class of phospho-tungstates already described. They appear 

 to be as a rule less well defined than these last, and, so far as I have 

 been able to discover, exhibit no character of special interest. In 

 analyzing the few salts of this series which I have studied, I have em- 

 ployed tlie same methods which I have used for the analysis of the 

 phospho-tungstates. Only the conditions are necessarily in some re- 

 spects different. Arsenic and tungstic oxides were precipitated together 



