W. J. Craw on the Determination of Phosphoric Acid. 393 
Arr. XX XVII.—On the Determination of Phosphoric Acid by 
Molybdate of Ammonia; by Wm. J. Craw, Assistant in the 
Yale Analytical Laboratory. 
[Read before the Berzelian Society of Yale College, March 30th.] 
Tue determination of phosphoric acid has always been one of 
the most important, and most difficult, problems of analytical 
alumina, the alkalies and alkaline earths. Several of these com- 
binations are decomposed with very great difficulty, the phos- 
phate of alumina, in particular, resisting nearly every effort to 
reduce it to its component parts. 
Althongh good methods have been proposed for the analysis of 
many of the simple phosphates, that of phosphate of lime, for 
instance, yet it usually happens, that several of these occur 
together, and, until very recently, no process has been devised 
which could effect the separation of phosphoric acid from al 
the bases previously mentioned, when in company. 
A great amount of labor has been spent by chemists, within 
the last few years, in the effort to overcome this difficulty. Nu- 
merous ways have been tried with greater or less success, but 
most of these contain inherent difficulties, which in many cases, 
means phosphoric acid could be separated and determined quan- 
titatively, which were completely successful. For this purpose 
a large quantity of the molybdate solution is prepared as fol- 
lows: 1 part of molybdic acid is dissolved in 8 parts of ammonia 
and 20 of nitric acid. The phosphate is dissolved in. nitric acid 
aud there is added to it a qnautity of molyhdie acid equal to 
about 30 times that of the phosphoric acid. The solution with 
* Vide’Erdmann’s Journal fiir Prak. Chem, vol. lili, p. 339. ~ 
Secoxp Series, Vol. XIII, No. 39.—May, 1852. 50 
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