170 METHODS FOR THE ANALYSIS OF BLOOD 



PHOSPHATES OF THE BLOOD 



Method of Marriott and Haessler 1 



Principle. Phosphates are precipitated from serum with 

 magnesia mixture. The precipitate is separated and dissolved 

 in hydrochloric acid. The hydrochloric acid solution of phos- 

 phates is then subjected to a colorimetric estimation. 



Procedure. Dilute 1 c.c. of clear serum with about 5 c.c. of 

 water in a small beaker. Add 2 drops of 0.1 N hydrochloric acid 

 and 1 c.c. of magnesia mixture. Then with stirring, run in slowly 

 2 c.c. of 10 per cent ammonia (one part concentrated ammonia 

 to nine parts of water), and allow to stand over night in a cool place. 



The precipitate is filtered off on a small Gooch crucible, the 

 mat being prepared as for the calcium determination. Wash the 

 precipitate and beaker four times, each time with about 5 c.c. of 

 the 10 per cent ammonia, then once with 95 per cent alcohol 

 made just alkaline with ammonia, and finally with 5 c.c. of 

 ether. Suction is kept on for several minutes in order to dry the 

 mat. The crucible is then returned to the beaker and 10 c.c. of 

 0.01 N hydrochloric acid are run in andallowed to percolate through 

 the crucible. The beaker is covered with a rubber dam or put in a 

 desiccator over water and allowed to stand for a couple of hours 

 or over night. The asbestos is then stirred up in the acid and the 

 suspension transferred to a centrifuge tube and centrifuged. 

 A 6 c.c. aliquot portion of the clear liquid is pipetted off and used 

 for colorimetric determination. This is carried out exactly as for the 

 calcium determination except that the ferric thiocyanate solution is 

 diluted to 40 or 50 c.c. A standard of magnesium ammonium 

 phosphate solution is used in place of calcium oxalate. Each 

 tube is diluted to the mark with 0.01 N hydrochloric acid, and the 

 contents are mixed by inverting several times, the ends of the 

 tubes being closed with a clean rubber stopper. 



Calculation. The calculation of results is as follows: If 1 c.c. 

 of serum were used and a 6 c.c. aliquot portion of the dissolved 

 precipitate taken for colorimetric determination, the color in the 

 Nessler tube corresponding to that resulting from the addition 

 of 0.9 c.c. of the standard phosphate solution, then 



0.9 X 0.02 X-/X i f a = 3.0 mg. phosphorus per 100 gms. cf serum. 

 1 Marriott and Haessler: Jour. Biol. Chem., 1917, 32, 241. 



