ACCURACY OF NEUMANN’S METHOD. to 
On THE ACCURACY oF NEUMANN’S METHOD FoR 
THE ESTIMATION or PHOSPHORUS. 
By H. 8. HALCRO WARDLAW, B.Sc., 
Science Research Scholar of the University of Sydney. 
(From the Physiological Laboratory of the University of Sydney.) 
[Read before the Royal Society of N. S. Wales, June 3, 1914. ] 
For the estimation of phosphates in the presence of any 
metals but those of the alkalies the customary procedure | 
entails two precipitations, each of which requires about 
twelve hours for completion. (1) The phosphate is pre- 
cipitated as ammonium phosphomolybdate by adding a 
solution of ammonium molybdate containing nitric acid. 
(2) The precipitate of ammonium phosphomolybdate is dis- 
solved in ammonium hydroxide and the phosphate is pre- 
cipitated from it as magnesium ammonium phosphate by 
the addition of magnesia mixture. This latter precipitate 
is ignited to magnesium pyrophosphate, from the weight of 
which the amount of phosphate may be calculated. This 
method was first employed by Sonnenschein. 
The tediousness of this process and the frequency with 
which estimations of phosphate are required for a number 
of purposes have led to many attempts to estimate the 
phosphate directly from the phosphomolybdate precipitate, 
either by weighing (Hggertz, Baxter, Baxter and Griffin, 
Chesneau), or volumetrically. These direct methods all 
have the drawback that there is some uncertainty as to 
the exact composition of the precipitate of ammonium 
phosphomolybdate obtained, so that although individual 
workers, performing their analyses under very uniform 
conditions, may have obtained satisfactory concordance in 
their results, these methods have not met with very general 
