PHOSPHORIC ACID IN BLOOD 173 



Preparation of the Reagent. Sufficient of the above solution 

 to contain 30 to 35 gins, of sodium molybdate (or this amount of 

 dry sodium molybdate dissolved in a small amount of water) 

 is measured into a precipitating jar or large beaker (2 liters), and 

 250 c.c. of a mixture of equal parts of concentrated HC1 and water 

 are added with stirring. 500 c.c. of water are mixed with the 

 solution and 40 to 50 c.c. of saturated strychnine sulfate solution 

 slowly added with stirring. 200 c.c. more of the dilute acid and 

 500 c.c. more water are added and, after mixing, the turbid solu- 

 tion is allowed to stand over night or longer if convenient. Next 

 day the precipitate has settled and most of the liquid may be poured 

 off clear. The remainder is filtered through a hardened, phos- 

 phorus-free filter. For use in the determination, 25 c.c. of this 

 solution are taken without further additions. 



Standard Phosphate Solution. 5 c.c. of the standard acid 

 potassium phosphate solution (containing 0.15 mg. of HaPO-i) 

 are measured into a 25 c.c. glass-stoppered graduated flask, a 

 drop of phenolphthalein is added, and the amount of alkali used 

 in neutralizing the digestion mixture above run in. The solution 

 is then made just acid with the 25 per cent H^SO.*, cooled, made 

 up to the mark with water, and well mixed. 



Precipitation. 25 c.c. portions of the strychnine molybdate 

 reagent are measured into each of two 50 c.c. glass-stoppered, 

 graduated flasks. 5 c.c. of the standard solution are run into one 

 of the flasks, which is kept gently rotating during the addition, 

 and 5 c.c. of the test solution similarly added to the other. When 

 the solutions are well mixed they are allowed to stand at least three 

 minutes, then filled to the mark, and mixed by inverting several 

 times, after which they are ready to be compared in the nephelom- 

 eter. 



Reading. The nephelometer tubes are filled with the solu- 

 tions to the same height and to the point at which, when the 

 tubes are in position in the nephelometer, the meniscus is just 

 out of reach of the light. The jacket on the standard tube is set 

 at a convenient point and readings are made as usual. 



Plasma 



0.5 c.c. of plasma is measured with a 0.5 c.c. Ostwald pipette 

 into a large test-tube, glass beads and 1.5 c.c. of the sulfuric- 



