76 PROCEEDINGS OF THE AMERICAN ACADEMY 



The only conclusion which can fairly be drawn from the analysis is 

 that there is at least one phospho-molybdate in which the number of 

 atoms of base exceeds three. It is certain that the salt does not rep- 

 resent a perfectly definite and homogeneous compound, and it may 

 possibly be a mixture of the 20-atom salt, 20 Mo0 3 . P 2 0, . 6 Ag 2 0, 

 and an acid molybdate of silver, 2 Mo0 3 . Ag 2 0, nearly in atomic pro- 

 portions. By dissolving the salt in nitric acid and evaporating, Debray 

 obtained another salt in small brilliant yellow crystals. For this salt 

 he proposes the formula 



20 MoO a . P,0 5 . 2 Ag 2 + 7 aq, 



but as usual he has given no analyses. 



Eighteen Atom Series. — I have myself met with no salts belonging 

 to this series, but according to Finkener* there are sodium salts corre- 

 sponding to the general formula 



18 Mo0 3 • P 2°s (3 — a) Na 2 + (25 + x) aq. 



These salts are yellow and easily soluble. 



Sixteen Atom Series. — 16:3 Ammonium Salt. — In preparing the 

 5 : 3 atom ammonium salt a white crystalline precipitate was formed, 

 insoluble in cold, but soluble with decomposition in much boiling water, 

 and easily soluble in ammonia. In this salt dried over sulphuric 

 acid, — 



0.5100 gr. lost by ignition with W0 4 Na 2 0.0722 gr. = 14.16% NH 3 



and H 2 

 1.1653 gr. gave 0.1259 gr. NH 4 C1 = 5.25% (NH 4 ) 2 

 0.8114 gr. gave 0.0658 gr. P 2 7 Mg 2 = 5.19% P 2 5 



The analysis corresponds with the formula 



16 Mo0 3 . P 2 5 . 3 (NH 4 ) 2 + 14 aq, 

 which requires, — 



Calc'd. Found. 



16 M0O3 2304 80.73 80.65 



P 2 5 142 4.97 5.19 



3 (NH 4 ) 2 156 5.46 5.25 



14H 2 ' 252 8.84 8.91 



2854 100.00 



Loc. cit., p. 1639. 



