78 PROCEEDINGS OP THE AMERICAN ACADEMY 



in which formula the phospho-molybdic acid is regarded as tribasic. 

 Debray gives the same formula, without details of analysis, and 

 Rammelsberg has very recently again analyzed the salt, confirming 

 the results of Zenker. Tbe salt in question is particularly interest- 

 ing, first, because the number of atoms of molybdic oxide is uneven ; 

 and secondly, because the basicity of the acid appears to be 3, and not 

 6, even when the salt has separated from neutral solutions. 



Jorgensen * has described two well-defined crystalline salts belonging 

 to this series and having according to his notation respectively the 

 formulas 



Co 2 (NH 3 ) 10 C1 2 . (5 Mo0 3 . 2 P0 4 H) 

 and 



Co s (NH 8 ) 10 Cl a . (5 MoO s . 2 P0 4 NH 4 ). 



I should write these 



5 Mo0 8 . P 2 O s . Co 2 (NH 3 ) 10 Cl 2 O 2 . H 2 

 and 



5 Mo0 3 . P 2 5 . Co 2 (NH 3 ) 10 Cl 2 O 2 (NH 4 ) 2 O. 



It will readily be seen that both salts correspond to the acid repre- 

 sented by the formula 



5 Mo0 3 . P 2 5 . 3 H 2 0. 



Acid 10 : 5 Ammonium Salt. — When ammonic phosphate is dis- 

 solved in boiling water, and molybdic oxide is added in small portions 

 at a time, the oxide readily dissolves, but a greater or less quantity 

 of a white insoluble crystalline salt is formed. The filtrate deposits on 

 evaporation large colorless crystals, which appear to be either trimetric 

 or monoclinic. Of these crystals, — 



1.1126 gr. lost on ignition with W0 4 Na 2 0.2076 gr. = 18.66% NH 3 



and H 2 0. 

 1.2962 gr. " " " 0.2425 gr. = 18.71% " 



1.21 G5 gr. " " " 0.2247 gr. = 18.47% " 



0.9263 gr. gave 0.1912 gr. P 2 7 Mg 2 = 13.20% P 2 5 

 1.0540 gr. " 0.2196 gr. " =13.32% " 

 1.1824 gr. " 0.3018 gr. NH 4 C1 = 12.41% (NH 4 ) 2 

 1.0183 gr. " 0.2563 gr. « =12.23% 



1.6430 gr. " 0.4168 gr. " = 12.32% " 



* Journal fiir prakt. Chemie, [2.] xviii. 209. 



