39 PHYSIOLOGICAL CHEMISTRY. 



a drop of the mixture when removed by means of a glass rod and 

 brought in contact with a drop of a solution of potassium ferrocya- 

 nide on a porcelain test-tablet produces instantaneously a brownish- 

 red coloration. 1 Take the burette reading and calculate the P 2 O 5 

 content of the urine under examination. 



Calculation. Multiply the number of cubic centimeters of uran- 

 ium acetate solution used by 0.005 to determine the number of 

 grams of P 2 O 5 in the 50 c.c. of urine used. To express the result 

 in percentage of P 2 O 5 multiply the value just obtained by 2, e. g., 

 if 50 c.c. of urine contained 0.074 gram of P 2 O 5 it would be equiva- 

 lent to 0.148 per cent. 



Calculate, in terms of P 2 O 5 , the total phosphate content of the 

 twenty-four hour urine specimen. 



2. Earthy Phosphates. To 100 c.c. of urine in a beaker add an 

 excess of ammonium hydroxide and allow the mixture to stand 

 12-24 hours. Under these conditions the phosphoric acid in com- 

 bination with the alkaline earths, calcium and magnesium, is pre- 

 cipitated as phosphates of these metals. Collect the precipitate 

 on a filter paper and wash it with very dilute ammonium hydroxide. 

 Pierce the paper, and remove the precipitate by means of hot water. 

 Bring the phosphates into solution by adding a small amount of 

 dilute acetic acid to the warm solution. Make the volume up to 

 50 c.c. with water, add 5 c.c. of sodium acetate solution and de- 

 termine the P 2 O 5 content of the mixture according to the directions 

 given under* the previous method. 



Calculation. Multiply the number of cubic centimeters of uran- 

 ium acetate solution used by 0.005 to determine the number of 

 grams of P 2 O 5 in the 100 c.c. of urine used. Since 100 c.c. of 

 urine was taken this value also expresses the percentage of P 2 O 5 

 present. 



Calculate the quantity of earthy phosphates, in terms of P 2 O 5 , 

 present in the twenty-four hour urine specimen. 



The quantity of phosphoric acid present in combination with the 

 alkali metals may be determined by subtracting the content of 

 earthy phosphates from the total phosphates. 



3. Total Phosphorus. Sodium Hydroxide and Potassium Nit- 



Inasmuch as I c.c. of the uranium solution should precipitate 0.005 gram of 

 P 2 O 5 , exactly 20 c.c. of the uranium solution should be required to precipitate 

 50 c.c. of the standard phosphate solution. If the two solutions do not bear 

 this relation to each other they may be brought info proper relation by diluting 

 the uranium solution with distilled water or by increasing its strength. 

 1 A ten per cent solution of potassium ferrocyanide is satisfactory. 



