116 PROCEEDINGS OF THE AMERICAN ACADEMY 



is exactly sufficient to saturate six molecules of orthophosplioi-ic acid, 

 but the salt certainly contains at least a part of the phosphorus as 

 metaphosphoric oxide. We may perhaps assume that the two modifi- 

 cations are equally divided between the bases, and the formula may 

 then be written 



22 WO3 . 3 (P2O3 . 3 K2O) . 6 POsNa . 2 KoO . 4 NagO + 42 aq. 



The subject of course requires further investigation. 



MONOMETAPHOSPHO-MOLYBDATES. 



The salts belonging to this series appear also to belong to two 

 different classes, which may be simply distinguished as crystalline and 

 gummy salts. Both these glasses are readily converted by acids into 

 orthophospho-molybdates. Up to the present time I have made only 

 a preliminary study of these compounds. 



10:2:5 Ammonic Monometaphospho-molyhdate. — When glacial 

 phosphoric acid is neutralized with ammonia, and the solution is mixed 

 with one of 14:6 ammonic molybdate, no precipitate is formed, but 

 on evaporation a thick, nearly colorless gummy mass is formed. On 

 standing for some time, this is almost comjoletely converted into a 

 crystalline mass. This may be drained, redissolved in water, in 

 which it is very soluble, and recrystallized several times from very 

 concentrated solutions. It then presents very beautiful, perfectly 

 colorless, flat tabular crystals. The solution gives at once, with nitric 

 acid, a precipitate of yellow orthophospho-molybdate ; with magnesia- 

 mixture and ammonia, a precipitate very different from ammonio- 

 magnesic orthophosphate. Argentic nitrate gives a flocky-crystalline 

 precipitate ; baric and thallous nitrates give beautiful white feathery- 

 crystalline salts ; mercurous nitrate gives a pale flocky-crystalline 

 precipitate, while cuprous sulphate forms none. Of this salt, 



1.4314 gr. gave 0.3002 gr. PoO-Mg^ = 13.41% Pg^s 

 0.8385 gr. " 0.1022 gr. (NH^)^ =12.19% 

 1.4016 gr. lost 0.2776 gr. = 19.81% 



The analyses agree with the formula 



10 M0O3 . 2 P2O. . 5 (NH4)20 + 9 aq, 

 which requires : 



