ADVANCED CHEMICAL PHYSIOLOGY 289 



phate which has formed through a small filter, wash well with dilute 

 ammonia (about 1 per cent.) and dry at 100. To estimate the P 2 O 5 

 present as pyrophosphate the precipitate and filter paper are incinerated 

 in a weighed crucible heating, after initial burning is complete, to bright 

 redness for fifteen to thirty minutes. This converts the ammonium 

 magnesium phosphate into magnesium pyrophosphate. Crucible is 

 cooled and weighed. 



Magnesium pyrophosphate X 0-638 = P 2 O 5 . 



Magnesium Citrate Mixture. Dissolve 400 gms. citric acid in 500 

 c.c. water by the aid of heat. Add to the hot solution 20 grm. 

 magnesium oxide (light). Cool, add 400 c.c. of 0-880 ammonia and 

 then water to 1,500 c.c. Allow to stand twelve to twenty-four hours 

 and filter. 



Total Phosphates. Neumann's Wet Ash Method. 10 c.c. urine are 

 placed in a 500 c.c. combustion flask and 10 c.c. concentrated sulphuric 

 acid plus 5 c.c. concentrated nitric acid are added. The mixture is 

 then carefully heated in a fume chamber until contents are colourless. 

 If there is much delay in the decolorisation, 34 c.c. of nitric acid 

 may be cautiously added and the flask again heated. When oxidation 

 is complete allow to cool, add 150 c.c. water and 30 c.c. ammonium 

 nitrate solution (50 per cent.), put on a water bath and heat to about 

 75 (as hot as the hand will bear), and then add 10-20 c.c. ammonium 

 molybdate solution (10 per cent.). Shake for about two minutes and 

 return to the water bath until the yellow precipitate of ammonium 

 phosphomolybdate settles (takes about half an hour). Filter off the 

 yellow precipitate with aid of suction through asbestos in a Gooch 

 crucible, wash rapidly and well with 1 per cent, nitric acid, dry in a 

 hot-water oven, cool and weigh. 

 0-1 gm. Am. phosphomolybdate = 0-00374 gm. P 2 O 5 or 0-00163 gm. P. 



If preferred the precipitate of phosphomolybdate, washed free from 



N 

 acid, is dissolved in a known volume of -~- NaOH, solution washed 



into the original combustion flask with about 200 c.c. of water, a few 

 drops of phenolphthalein solution added and the solution boiled for 

 about fifteen minutes to get rid of ammonia (test the steam with glazed 

 litmus paper). Cool rapidly in running water and titrate excess of 



N 

 alkali with -^ H 2 SO 4 . 



1 c.c. -g- H 2 SO 4 = 1-268 mg. P 2 O 5 or 0-5536 mg. P. 



Total phosphates less inorganic phosphates gives the amount of 

 organic phosphate present. 



NOTE. Protein must first be removed if present. This is best 

 clone by boiling the urine acidified with acetic acid in a flask, cooling 

 and filtering. 



Inorganic Sulphates (Folin). 35 c.c. of urine are diluted with 

 100 c.c. of water in an |Erlenmeyer flask (of 250 c.c. capacity) 

 and 10 c.c. of dilute hydrochloric acid (1 part HC1 (cone.) to 4 

 parts water) added. A burette containing a 5 per cent, solution of 

 barium chloride is then placed over the mouth of the flask and 10 c.c. 

 of_the reagent allowed to drop into the contents of the flask at a slow 



X 



