238 PROCEEDINGS OF THE AMERICAN ACADEMY 



in cold water. Hot water dissolves it only in a small proportion, but 

 gives a milky emulsion, which settles very slowly. For analysis the 

 salt was drained on a filter-pump, well washed with cold water, and 

 finally dried on woollen paper. Of this salt, — 



1.9695 gr. gave 0.0980 gr. (NHJ^O = 4.97% by titrition. 



1.1425 gr. " 0.0559 gr. " =4.89% " 



0.9301 gr. lost on ignition with WO^Naa 0.1225 gr. = 13.17% 



1.2722 gr. gave 0.1374 gr. P^O.Mg, = 7.97% PO3H3 



The analyses correspond fairly well with the formula 



24 M0O3 . 4 {H . PO . (OU)^} 4 (NHJP + 17 aq, 



} 



Found. 



79.88 ) 

 88.04 ^ g^ y 87.85 



4.89 4.97 

 7.22 



100.00 



The salt certainly contained a little phospho-molybdate, to which 

 the faint yellow tint was probably due. It is very difficult to obtain 

 a solution of phosphorous which is absolutely free from phosphoric acid. 

 With respect to the formula I remark that the number of molecules 

 of water may be purely accidental, and that there is at present no sxif- 

 ficient reason for rejecting the simpler expression 



12 M0O3 .2 (H . PO . (011)2} 2 (NHJ^O -f x aq. 



The type of the acid is then 



12 MoOj . 2 {H . PO . (OH),,} 2 Kfi. 



A solution of baric chloride boiled with the phosphoroso-molybdate 

 decomposes it more or less completely, giving a white very fine- 

 grained crystalline salt. Under the same circumstances argentic ni- 

 trate gives a nearly colorless flocky substance, which quickly becomes 

 darker, and finally assumes a dull violet color. Mercurous nitrate 

 yields a clear pale yellow flocky salt ; the phosphoroso-molybdate does 

 not reduce a solution of mercuric chloride even on boiling. Cupric 

 sulphate dissolves the salt to a clear blue liquid. Manganous sulphate 

 also dissolves it, forming a colorless solution. Alkaline hydrates dis- 

 solve it very readily to colorless liquids. The salt is readily decom- 



