OF ARTS AND SCIENCES. G9 



0.5905 gr. lost ou ignition with WO^Na^ 0.0432 gr. NH3 and ilfi 



1.7158 gr. gave 0.1027 gr. Tfi.^Ig, = 3.83% P^O^ 

 0.980G gr. " 0.05G7 gr. P^'o^Mg^ = 3.70% Pp^ 

 1.8903 gr. " 0.1321 gr. NII^'ci "=3.20% (NH,),0 



In these analyses, tlie first determination of the phosphoric oxide 

 was made by double precipitation only, without subsequent treatment 

 with ammonic sulphide; but in the second, this reagent was employed 

 in the manner above described. The ratio of M0O3 to PjO^ is almost 

 precisely 2-1: 1, and the analyses correspond closely with tlie formula 



24 M0O3 • P2O5 • 3 (NHJP + 24 M0O3 . pp. . 2 (Nig.O . H,0 



+ 16 aq, 

 which requires : — 



7762 100.00 lOO.-OO 



Acid salts of similar type occur frequently in the class of phospho- 

 molybdates, as in that of phospho-tungstates. 



24 : 1 Croceo-cohalt Salt. — The disposition of the cobaltamines to 

 form highly crystalline compounds, together with their well-defined and 

 various degrees of basicity, led me to study the relations of these bases 

 to the phospho-molybdic acids. This had already been done to a cer- 

 tain extent with the 5 : 1 atom series by Jorgensen, whose results I 

 shall cite in connection with that series. Neither roseo-cobalt nor 

 luteo-cobalt forms well-defined salts with 24 : 1 phospho-molybdic acid. 

 I had therefore recourse to croceo-cobalt,* the oxide of which may be 

 written 



Co2(NH8)8(NO,),0, or, briefly, CcO. 



The chloride of this series gives no precipitate with solutions of 7 : 3 

 amnionic molybdate, or of hydro-disodic phosphate ; but in an acid solu- 

 tion of these two salts a solution of the chloride throws down a beau- 

 tiful bright yellow highly crystalline salt, which msiy be washed with 

 cold water. The portion analyzed was dried on woollen paper only. 

 Of this salt, — 



* Proceedings of Amidcan Academy, Vol. X. p. 1. 



