GIBBS. — COMPLEX INORGANIC ACIDS. 263 



The salt is nearly insoluble in cold water. Boiling water dissolves 

 it, but the salt is decomposed, giving a jjide yellow fiocky precipitate 

 and a sherry wine colored solution. On standing a short time, the so- 

 lution as it cools becomes pale yellow, and finally almost colorless, 

 while the precipitate gradually becomes brighter yellow and crystal- 

 line, and the original salt appears to be again formed by recombination. 

 Both the precipitate formed in the decomposition by boiling water and 

 the wine-yellow solution give reactions with argentic nitrate which 

 differ from one another as well as from the yellow crystalline silver 

 salt formed by digesting the pyrophospho-molybdate of manganese 

 and sodium with argentic nitrate. 



In the analysis the solution of the salt was boiled with mercurous 

 nitrate and mercuric oxide. The precipitate contained only molybdic 

 and phosphoric oxides, and was free from manganese. There is 

 therefoi-e reason for assuming, as I have done, that all the manga- 

 nese is basic, and that none is present in the form of the molecule 

 PaO^Mn. 



Mangano-ammonic Pyrophospho-Molybdates. 



When manganous pyrophosphate is digested for some time with a 

 strong solution of 14:6 acid ammonic molybdate, a buff-yellow very 

 slightly soluble compound is formed. This is to be well washed, 

 dried on woollen paper, and afterward in pleno over sulphuric acid. 

 Of this salt, analyzed by Mr. G. W. Patterson: 



0.7830 gram lost on ignition with WO^Nag 0.0778 gram NHg -f H„0 



= 9.94%. 

 0.6554 gram lost on ignition with WOiNao 0.0645 gram NHg -f H2O 



= 9.84%. 

 0.8590 gram gave 0.0338 gram NH3 = 3.92%. 

 0.7191 gram gave 0.0285 gram NH3 = 3.97%. 

 0.8725 gram gave 0.0881 gram PoOyMg, = 6.46% P0O5. 

 0.8725 gram gave 0.2841 gram PAMug = 12.62% MnO. 



The analyses lead to the formula, 



20 M0O3 . 2 PA . 10 MnO . 5 (NH^)^© -\- 10 aq., 

 which requires : 



