OF ARTS AND SCIENCES. 71 



Twenty-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, 

 leaviug 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 Mo0 3 . P 2 5 . 3 (NH 4 ) 2 + 12 aq, 



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

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



22 W0 8 . P 2 3 . 3 (NH 4 ) 2 -f 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 W0 4 Na 2 0.0873 gr. = 5.17% MI, 



and H 2 

 1.77G4 gr. gave 0.6200 gr. P 2 O r Mg 2 =4.17% PX>,-,. 

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

 1.2334 gr. « 0.6262 gr. NH 4 C1 = 4.23% (NH 4 ) 2 0. 



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 MoO s . P 2 5 . 3 (NH 4 ) 2 ; 



