110 PROCEEDINGS OP THE AMERICAN ACADExMY 



The phosphoric oxide was determined as before by evaporation with 

 nitric acid to convert the pyrophosphoric into orthophosphoric acid. 

 The analyses corresjiond to the formula 



22 WO3 . 9 PaO^K, + 49 aq, 



8963 100.00 



22 : 9 : 13 Potassic Pyrophospho-tungstate. — This salt was obtained 

 by boiling tungstic oxide for some time with potassic pyrophosphate. 

 After filtration and standing a white crystalline salt separated, which 

 was well drained on the filter-pump, and then washed with cold water 

 in which it is but slightly soluble. In much boiling water it dissolves 

 on boiling to a clear liquid. The solution gives a white crystalline 

 precipitate with argentic nitrate, — no precipitate at first with cupric 

 sulphate. On boiling, a very pale blue crystalline salt separates, 

 which does not contain tungsten, and is either a cupric pyrophosphate 

 or a double salt of potassium and copper. The solution of the pyro- 

 phospho-tungstate gives a dense white distinctly crystalline precipitate 

 with mercurous nitrate, and a turbid solution with baric chloride yield- 

 ing on boiling a white feathery crystalline salt. No precipitate is 

 formed with manganous sulphate, but after a short time the solution 

 becomes turbid. In this salt, 



1.6112 gr. gave 1.2119 gr. oxides = 75.22% 



1.9796 gr. " 1.4894 gr. " =75.23% 



1.6421 gr. " 0.3862 gr. P.O-^s = 15.06% 



1.2433 gr. lost by direct ignition 0.1299 gr. = 10.45% 



The analyses agree closely with the formula 



22 WO3 . 6 P.O.K^ . 3 P20,Il4 . K2O . H.O + 42 aq, 



so that the type is, as in other cases, 



22 WO3 . 9 P^O.H, . 2 R2O. 



The formula requires : 



