THE JOURNAL OF PHARMACOLOGY. 103 



Quantitative Estimation of Phosphoric Acid. 

 I. Gravimetric. A given quantity of urine is ashed, and the estima- 

 tion is carried out by means of the ammonium molybdate method as follows : 

 Reagents required : 



A. Solution of ammonium molybdate, made by dissolving 100 gram- 

 mes of ammonium molybdate in enough water to measure one liter. This so- 

 lution is added under constant stirring, to one liter of nitric acid S/G i . 200. 



B. A concentrated solution of ammonium nitrate, made by dissolving 

 750 grammes of ammonium nitrate in enough water to make one liter. 



C. A dilute solution of ammonium nitrate made by dissolving 150 

 grammes of ammonium nitrate in enough water to make one liter. 



D. Magnesia Mixture, made by dissolving 55 grammes of crystalline 

 magnesium chloride, and 79 grammes of ammonium chloride in a mix- 

 ture of 650 Cc. of water and 350 Cc. of io;^f water of ammonia. 



E. Ammonia water 2>4fc, made by adding i part of lofo water of am- 

 monia to 3 parts of water. 



Execution of method in case of urine. 20 Cc. of urine are placed in a 

 platinum crucible, 0.5 — i.o gramme of a mixture of i part of potassium 

 nitrate and 3 parts of sodium carbonate are added, and the whole evapo- 

 rated to dryness. The dry residue is ashed, and the ash extracted with 

 warm water and a very small quantity of nitric acid. The solution thus 

 obtained is filtered into a beaker, washing the filter well. In operations 

 where great accuracy is required, the filter is also ashed, the ash extracted 

 in the same manner as before, and the liquid thus obtained added to the 

 first liquid. To the combined liquids 50 Cc. of ammonium molybdate 

 solution, and 15 Cc. of the concentrated solution of ammonium nitrate 

 are added, the mixture stirred well and set aside for at least six hours at 

 a temperature of about 6o°C. After this time, the liquid is removed 

 by decantion, allowing it to pass through a small filter, from the yellow 

 precipitate (ammonium phospho-molybdate) which has formed. The 

 precipitate still in the beaker, is washed with the dilute solution of 

 ammonium nitrate, and after allowing the precipitate to subside, the wash- 

 ings are passed through the same filter as before. Now dissolve the pre- 

 cipitate in ammonia water (2>^ ^ ) and pass the solution through the same 

 filter as the first washings. Wash the beaker and filter thoroughly with 

 ammonia water {2}4''/r) and incorporate these washings with the solution 

 already on hand. To this liquid now add 15 Cc. of solution of ammonium 

 chloride (1:8) and 15 Cc. of magnesia mixture, stir well, and set aside 

 for a period of twelve hours. After this time, transfer the precipitate 

 (ammonia-magnesium phosphate), to a filter of known ash, and wa.sh it 

 with amnionic water (2)4 fo) until the washings are free from chlorides. 

 Allow the precipitate to become thoroughly dry, transfer it, together with 

 the filter to a tared platinum crucible, and ignite. After cooling, moisten 



