62 PROCEEDINGS OP THE AMERICAN ACADEMY 



VI. 



RESEARCHES ON THE COMPLEX INORGANIC ACIDS. 

 By Wolcott Gibbs, M. D., 



Rumford Professor in Harvard University. 



(Continued from Vol. XVI. p. 139.) 



Presented May 24th, 1881. 



PHOSPHO-MOLYBDATES. 



The application of molybdic oxide to the separation and estimation of 

 phosphoric acid has given a special interest to the phospho-moljbdates, 

 and they have accordingly been studied more or less completely by 

 several chemists. The most thorough investigations which we possess 

 are those of Debray,* Rammelsberg,t and Finkener,J but particular 

 salts have been examined by others, and these will be noticed under 

 the appropriate special headings. 



Phospho-molybdates appear to be formed whenever phosphoric acid 

 or a soluble phosphate is brought into solution with a molybdate, the 

 presence of a free acid not being essential. They are also formed 

 when phosphates and molybdates are fused together, when molyb- 

 dates insoluble in water are dissolved in phosphoric acid, when 

 molybdic oxide is digested with an alkaline phosphate, and when in- 

 soluble phosphates and molybdates are treated together with a dilute 

 acid. As a class, they are better defined and more easy to obtain 

 pure than the phosplio-tungstates which in many respects they closely 

 resemble. When phospho-molybdates of fixed alkaline bases are 

 heated, they at first give off water of crystallization, and by careful 

 heating may be obtained anhydrous. In some cases, however, molyb- 

 dic oxide is volatilized even from salts containing fixed alkaline bases. 



* Bull. Soc. Chim., [2.] v. 404. 



t Rcnchte der Deutsclien Ciicm. Gescllschaft, Zehnter Jahrgang, p. 1776. 



} Ibid., Elfter Jahrgang, p. 1G38. 



