OF ARTS AND SCIENCES. Ill 



and phosphate, an acid sodium salt is often precipitated immediately, 

 and almost always after standing a day or two. But it must be re- 

 marked that in this case the proportion of tungstic and phosphoric 

 oxides is not always that which existed in the original mixture. In 

 some cases I have fused the tungstate and phosphate together in 

 definite proportions in a large platinum crucible, but this method does 

 not present any special advantage. In other cases I have dissolved 

 tungstic oxide in solutions of alkaline phosphates. Finally, I have 

 in a few instances employed the original method of Scheibler. The 

 alkaline phospho-tungstates, when nob too highly acid, are usually 

 rather easily soluble in water, but in the act of solution they almost 

 always undergo a certain amount of decomposition, a white crystal- 

 line powder being formed which is comparatively insoluble. Some- 

 times the solution becomes milky at once, and remains so for a very 

 long time. In all cases it must be allowed to stand until it becomes 

 perfectly clear, and then poured upon the filter without disturbing the 

 precipitate, as the filtrate would otherwise be turbid. 



The alkaline phospho-tungstates are not decomposed by hydric sul- 

 phide except to a very limited extent. A current of the gas usually 

 produces a blue color from the reduction of a small portion of the 

 tungstic teroxide to the lower oxide W 2 5 . When an alkaline 

 sulphide is added to a solution of a phospho-tungstate a similar reduc- 

 tion is produced. The addition of chlorhydric acid then gives only a 

 small precipitate of tungstic sulphide. Zinc readily reduces a portion 

 of the teroxide to the blue oxide, but the reduction even after some 

 time is very far from complete. The relations of acid phospho-tung- 

 states to salts of the various alkaloids have already been pointed out 

 by Scheibler. In almost all cases nearly insoluble more or less dis- 

 tinctly crystalline precipitates are formed. I find that a beautiful heavy 

 white crystalline salt is thrown down when an acid phospho-tungstate, 

 as, for example, the sodium salt 24 W0 3 . P 2 6 . 2 Na 2 . 4 H 2 0, is 

 mixed with a solution of urea, or even with urine. In this last case 

 the precipitate contains also slightly soluble salts of potassium and 

 ammonium. It is possible that the reaction may be utilized in animal 

 chemistry. The phospho-tungstates also precipitate egg-albumen as 

 a white flocky substance, which may prove to be a definite salt, in 

 which case the high molecular weight of the acid would be of great 

 value in determining the equivalent of the compound. I have made 

 no experiments in this direction, and throw out the suggestion for what 

 it may be worth. 



Mercurous nitrate precipitates all the phospho-tungstates almost 



