232 PROCEEDINGS OF THE AMERICAN ACADEMY 



XVII. 



RESEARCHES ON THE COMPLEX INORGANIC ACIDS. 



By Wolcott Gibbs, M. D., 



Rumford Professor in Harvard University. 



(Continued from Vol. XVII. p. 90.) 

 Presented May 9th, 1883. 



The compounds which I have hitherto described may be embraced 

 under the general formula 



7» R 0,3 . 2 W.p, . p ^'\0. 



in which m may represent any even number from 10 to 48 inclusive, 

 p the number of molecules of base (old style), R an atom of tungsten 

 or molybdenum, and R' one of phosphorus or arsenic. I shall now 

 proceed to show that these results may be generalized in a variety of 

 different ways, and, further, that there are other typical formulas, per- 

 haps less general than that above given, but still embracing many 

 interesting and instructive special cases. 



HYPOPHOSPHO-MOLYBDATES. 



Hypophospho-molyhdate of Ammonium. — When solutions of 14:6 

 acid ammonic molybdate and sodic hypophosphite are mixed, no 

 precipitate is formed, but the liquid takes a fine blue color from the 

 partial reduction of molybdic teroxide to Mo.^O^. On addition of 

 chlorhydric acid and stirring for a short time, a large quantity of a 

 crystalline salt separates. This is to be filtered off, well drained by 

 the filter-pump, and washed with cold water, in which it is not very 

 soluble. When perfectly pure and free from Mo^Og the salt presents 

 colorless prismatic crystals, which are readily soluble in hot water. 

 The solution, at first pale blue, speedily assumes a deeper tint; with 

 cold water a colorless strongly acid solution may be obtained, and 



