PHOSPHOROUS 75 



Calculation. The weight of the BaS(>4 precipitate should be 

 multiplied by 2, since only one-half (125 c.c.) of the total volume 

 (250 c.c.) of fluid was precipitated by the barium chloride. The 

 remaining calculation should be made according to directions 

 given under Total Sulphates, page 73. 



Calculate the quantity of ethereal sulphates, expressed as SOs, 

 in the twenty-four-hour urine specimen. 



PHOSPHORUS 



Total Phosphates (Uranium Acetate Method) 



Principle. Standard uranium acetate is run into a measured 

 quantity of urine until all of the phosphate has been precip- 

 itated as insoluble uranium phosphate. An excess of uranium is 

 indicated by a reddish coloration with potassium ferrocyanide. 

 This method is accurate and gives practically the total phosphorus 

 of urine inasmuch as the latter exists generally almost entirely 

 as phosphates. 



Procedure. To 50 c.c. of urine in a small beaker or Erlenmeyer 

 flask add 5 c.c. of a special sodium acetate solution and heat the 

 mixture to the boiling-point. From a burette, run into the hot 

 mixture, drop by drop, a standard solution of uranium acetate 

 until a precipitate ceases to form and a drop of the mixture when 

 removed by means of a glass rod and brought into contact with 

 a drop of a solution of potassium ferrocyanide on a porcelain test- 

 plate produces instantaneously a brownish-red coloration. Take 

 the burette reading and calculate the P2O5 content of the urine 

 under examination. 



Calculation. Multiply the number of cubic centimeters of 

 uranium acetate solution used by 0.005 to determine the number 

 of grams of P2Os in the 50 c.c. of urine used. To express the result 

 in percentage of P20s multiply the value just obtained by 2, e.g., 

 if 50 c.c. of urine contained 0.074 gm. of P2Os it would be equiv- 

 alent to 0.148 per cent. 



Calculate, in terms of ?2O5, the total phosphate content of the 

 twenty-four-hour urine specimen, 



