72 PROCEEDINGS OF THE AMERICAN ACADEMY 



In another preparation, — 

 1.0324 gr. lost on ignition with W0 4 Na 2 0.0922 gr. — 8.93% "NH 3 



and H 2 

 2.0670 gr. gave 0.1255 gr. P 2 T M g 8 = 3 - 88 % P 2°s 

 2.0352 gr. « 0.1220 gr. " " = 3.84% " 



These analyses lead to the formula 



22 MoO s . P 2 0, 5 . 3 (NH 4 ) 2 -f- 9 aq, 

 which requires : — 



CalcM. 



17.21 



3.84 



8.77 8.93 



If from the analyses of the two salts above described we calculate 

 the composition of the combination of molybdic and phosphoric oxides 

 supposed to be isolated, and compare this with the percentages calcu- 

 lated upon the two hypotheses of a ratio of 22 : 1 and a ratio of 24 : 1, 



In both cases the phosphoric oxide was precipitated twice, but the 

 ammonia-magnesian phosphate was not treated with amnionic sulphide. 

 According to the results of Dr. Gooch already cited, the probable 

 error of this method does not exceed 1 % in excess of the quantity of 

 phosphoric oxide present. It appears, therefore, that the correction 

 to be applied to the phosphoric oxide in the above analyses does not, 

 at most, exceed 0.04%. The mean of Dr. Gooch's analyses would 

 require a deduction of 0.02% only. The yellow ammonium' salt 

 analyzed by Eammelsberg corresponds to the formula 



22 MoO„ . P 2 O s . 3 (NH 4 ) 2 -f 12 aq, 



which requires (Rammelsberg) 



