78 H. S. H. WARDLAW. 
boil, and the phosphate was precipitated by the addition of 
40 cc. of 19% ammonium molybdate, the liquid being 
thoroughly shaken up for about one minute after the 
addition. The precipitation performed thus occurs in the 
presence of 107% ammonium nitrate at a temperature not 
lower than 70°—80° CO. and is complete in a few minutes. 
After standing for half an hour, the supernatant fluid was 
poured off through a thin 15 cm. filter, and the precipitate 
was washed four times by decantation with 150 cc. of ice- 
cold water each time (temperature 5°—8° O.), the filter 
being filled with iced water after each washing. The final 
washings were neutral to litmus. The filter, containing a 
small quantity of the precipitate, was then added to the 
main bulk in the flask, some water was put in, and N/2 
NaOH was run in until the precipitate was dissolved (19°0cc. 
required), 6°0 cc. excess being then added (total 25°0 cc.). 
The solution was diluted, the filter broken up by vigorous 
shaking, and the ammonia boiled off. The solution was 
then cooled, its volume was made up to 150 cc., 6 drops of 
0°5% alcoholic phenolphthalein added, and titrated with 
N/2 H,SO, (6°25 ce. required), 2°0 cc. excess were added, 
the CO, was boiled off, and the hot solution neutralised 
again with N/2 NaOH (1°25 ce. required). Thus the total 
volume of alkali used was 25°0 + 1°25 = 26°25 cc., and of 
acid, 6°65 + 2°0 = 8°65 cc. The difference between these 
two volumes, 17°6 cc., multiplied by 1°268 gives 22°3, 
according to Neumann the number of milligrams of P.O; 
present. | 
An attempt was first made to wash the precipitate by 
suction in the way recommended by Plimmer and Bayliss, 
but in every case it was found impossible to prevent visible 
amounts of the precipitate from passing through the filter. 
The precipitation was also tried in the presence of 15% 
ammonium nitrate according to Gregersen’s directions, but 
