GIBBS. — COMPLEX INORGANIC ACIDS. 265 



there is no sufficient evidence that it forms here an integrant molecule 

 Po07Mn, as in sodio-mauganous pyrophosphate, PgOyMn . Na^. I re- 

 gard the question, however, as still an open one, since the molecule 

 PoOjMn, assuming its existence, may be decomposed by mercu- 

 rous nitrate and give a corresponding mercurous integrant molecule 

 P207Hg2, and since the salt is decomposed by water like the other 

 salts of this series. It appears also from the above that the pyro- 

 phospho-molybdates do not correspond in composition to the pyro- 

 phospho-tungstates. At least I have not found in them the molybdenum 

 molecule corresponding to the tungstic molecule, 22 WO3 . 9 P2O7. 

 It must, however, be remarked that, as I shall show, the pyrophospho- 

 tuucrstates which contain manganese do not contain this molecule. 



Mangano-sodiG Py7-ophospho- Tungstates. 



These salt? are very easily formed by boiling manganous pyrophos- 

 phate with acid tungstates. Dark sherry-wine colored solutions are 

 formed, which in cooling deposit crystals in abundance. 



14 : 1 : 3 : 6 Mangano-sodic Pyrophospho-7\ingstate. This salt is 

 formed more conveniently by mixing a solution of 12 : 5 sodic tung- 

 state with manganous pyrophosphate and digesting for some hours in 

 a closed bottle heated in a water bath. The pyrophosphate must be 

 in excess. It dissolves rather slowly to a fine deep orange-colored 

 li(;[uid, which after evaporation deposits beautiful crystals, which may 

 be redissolved and recrystallized. In spite of the employment of an 

 excess of manganous pyrophosphate, it is rather difficult to obtain a 

 solution of the salt which is perfectly saturated with the manganous 

 salt. The crystals have a brownish orange color. They effloresce in 

 dry air, though not rapidly, but in pleno over sulphuric acid they lose 

 water in relatively large quantity. Of this salt, analyzed by IMr. G. 

 "VV. Patterson: 



1,4176 grams lost on ignition with WOiNao 0.2032 gram - 14.34^ 

 water. 



1.2375 grams gave 0.0611 gram PjO^Mgo = 3.16% PA . 

 \ 1.0476 grams gave 0.1041 gram PAMn., = 4.97% MnO. 

 ( 1.0476 grams gave 0.7650 gram WO, -F PA = 73.05%. 



The analyses lead to the formula, 



14 WO3 . P0O5 . 3 MnO . 6 NagO -f- 36 aq., 

 which requires: 



