74 PROCEEDINGS OP THE AMERICAN ACADEMY 



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The salt is therefore the acid salt corresponding to a neutral salt 

 with the formula 



22 Mo0 3 . P 2 0. . 3 K 2 0. 



Rammelsberg's analyses agree better with the formula of the acid 

 salt given above than with that of the neutral compound assumed by 

 him. 



Twenty Atom Series. — The only salt of this series which I have 

 obtained is one of ammonium prepared like the salts already described, 

 having like these a fine yellow color and a very fine-grained crystalline 

 structure, and like them but slightly soluble in water. Of this salt, — 



1.0936 gr. lost on ignition with W0 4 Na 2 0.0729 gr. = 6.66% NH 3 



and H 2 

 1.8183 gr. lost on ignition with W0 4 Na 2 0.1155 gr. = 6.35% NH 3 



and H 2 

 0.8862 gr. gave 0.6153 gr. NH 4 C1 = 4.12% (NH 4 ) 2 

 1.3213 gr. gave 0.6224 gr. P 2 O r Mg 2 = 4.19% P. 2 5 

 1.5135 gr. gave 0.6349 gr. P 2 7 Mg. 2 = 4.31% P 2 5 



The salt was dried on a water-bath, and afterward over sulphuric 

 acid. The phosphoric oxide was precipitated twice, but not treated 

 with ammonic sulphide. The analyses lead to the formula 



60 MoO„ . 3 P 2 0. . 8 (NH 4 ) 2 . H 2 -f- 11 aq. 

 which requires : — 



If we calculate the composition of the mixed oxides of molybdenum 

 and phosphorus existing in this salt we have : — 



