45 
It was found that by the above procodure the phosphomolybdate 
is thrown down in four hours' time, leaving a clear supernatant liquid. 
In cases where it is possible it is best to let the precipitate stand over- 
night, although in all cases where duplicate determinations were made 
with some standing overnight and others four hours for the deposition 
of the yellow precipitate, closely agreeing results were obtained. The 
addition of excessive amounts of ammonium nitrate to the hydro- 
chloric acid extract does not offset the influence of the chlorids. It was 
found that the presence of chlorids caused an excessive precipitation 
of molybdic acid also. 
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