OP ARTS AND SCIENCES. 75 



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It will be seen that the ratio is here very nearly as 20 : 1. This may 

 however be merely accidental, and farther researches are necessary to 

 fully establish the existence of a 20-atom series. 



According to Debray a solution of argentic nitrate gives with one of 

 phospho-molybdic acid a precipitate which soon becomes crystalline, 

 and which has the formula 



20 M0O3 . P2O5 . 7 Ag.p + 24 aq. 



Such a salt would possess a twofold interest, first, as another evi- 

 dence of the existence of a 20-atom series of phospho-molybdates, and, 

 secondly, as showing that the acid of the series may unite with more 

 than six atoms of base. On mixing the two solutions as above, I ob- 

 tained a precipitate in small indistinct crystals of a greenish yellow color. 

 These crystals were soluble in hot water, but the solution was quickly 

 decomposed with precipitation of a white powder. Under the micro- 

 scope with a high power and transmitted light the salt appeared to 

 consist of small tabular crystals mixed with a few long yellow prisms 

 of very different habitus. Of this compound, — 



1.3604 gr. lost by ignition with WO^Na, 0.0G92 gr. water == 5.08 c;^ 

 2.1099 gr. gave 0.8287 gr. AgCl = 31.63% Ag^O 

 0.6733 gr. gave 0.2619 gr. AgCl = 31.44% Ag.p 

 2.1099 gr. gave 0.0928 gr. PgO^Mg^ = 2.81% Ffi. 



The phosphoric oxide was determined in the filtrate from the ar- 

 gentic chloride by double precipitation and treatment with amnionic 

 sulphide. The ratio of the molybdic to the phosphoric oxide is as 

 21 : 1, but the formula which most nearly represents the analysis is 



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