OF ARTS AND SCIENCES. 71 



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Tioeniy-two Atom Series. — In the paper already referred to, Ram- 

 melsberg has described several salts in which he found the ratio of 

 molybdic to phosphoric oxide as 22 : 1. Unfortunately, he has not 

 given the method of analysis which he employed, and in a question of 

 so much difficulty and delicacy it is, to say the least, extremely desira- 

 ble to know what degree of precision may be expected in the analyses. 

 As his results appear to be supported by my own, I shall adopt them, 

 leaving to the further progress of analytical chemistry the final settle- 

 ment of the few doubtful points. 



22 : 3 Ammonium Salt. — Rammelsberg found for the neutral salt 

 of this series the formula 



22 M0O3 . P2O5 . 3 (NHJP + 12 aq, 



which corresponds, except as regards the amount of water of crystalli- 

 zation, with a phospho-tungstate which I have already described, — 



22 WO3 . P2O5 . 3 (NHJ^O + 21 aq. " 



In one preparation of a yellow insoluble ammonium salt exactly 

 resembling the corresponding salt of the 24-atom series, — 



1.6885 gr., lost on ignition with WO^Na^ 0.0873 gr. = 5.17% Nllg 



and H2O 

 1.7764 gr. gave 0.6200 gr. PgO^Mg, = 4.17% P^O^. 

 1.9024 gr. " 0.6029 gr. " =4.01% " 



1.2334 gr. " 0.6262 gr. NH.Cl = 4.23% (NH,)^. 



The salt was dried for some time in pleno over sulphuric acid, and 

 had evidently lost water of crystallization. If we deduct the remain- 

 ing water, 0.94%, and calculate the analysis for an anhydrous salt, 

 we have for the formula 



22 M0O3 • ^'Po • 3 (NH,)P ; 



Calc'd. 



22 M0O3 3168 91.41 91.68 



PP, 142 4.09 4.05 



3(NH,)P 156 4.50 4.27 



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