URINE 569 



drop of a solution of potassium ferrocyanide 1 on a porcelain test-tablet produces 

 instantaneously a brownish-red coloration. 2 Take the burette reading and 

 calcu'ate the P 2 O 6 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 P 2 O 6 in the 50 c.c. 

 of urine used. To express the result in percentage of P 2 O 6 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 equivalent to 0.148 per cent. 



Calculate, in terms of P205, the total phosphate content of the 24- 

 hour urine specimen. 



Interpretation. The excretion of phosphoric add is extremely 

 variable but on the average the total output for the 24 hours is about 

 2.5 grams expressed as PzOs. Ordinarily the total output is mainly in 

 the form of phosphates and is distributed between alkaline and earthy 

 phosphates in the ratio of 2 : i but this is likewise inconstant. The 

 greater part of the phosphate excretion arises from the ingested food, 

 either from the preformed phosphates or more especially from the 

 organic combinations as phospho- and nucleoproteins. The | ex- 

 cretion is consequently very largely dependent upon the phosphorus 

 content of the diet. Some of the phosphoric acid results from the 

 breakdown of the tissues of the body, and this endogenous phosphoric 

 acid excretion is increased in conditions of increased metabolism as in 

 fevers. The findings in pathological conditions have been somewhat 

 contradictory due to lack of control of diet. The so-called "phos- 

 phaturias" nearly always represent decreased acidity and not in- 

 creased phosphate content of the urine. Such conditions are, however, 

 significant as indicating a possible tendency to the formation of phos- 

 phatic calculi. 



2. Earthy Phosphates. Principle. The earthy phosphates are 

 precipitated by making the urine alkaline. The precipitate is filtered 

 off, dissolved in acid and titrated with uranium acetate. 



Procedure. To 100 c.c. of urine hi a beaker add an excess of ammonium 

 hydroxide and allow the mixture to stand 12-24 hours. Under these conditions 

 the phosphoric acid hi combination with the alkaline earths, calcium and mag- 

 nesium, is precipitated 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 phos- 

 phates 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 



x Cochineal in 30 per cent alcohol may be used as an indicator. If employed it is added 

 directly to the urine after the uranium acetate titration produces no further precipitate. 

 A green color is the end reaction. The use of cochineal is more convenient but rather less 

 accurate than the procedure involving the use of the ferrocyanide. 



2 A 10 per cent solution of potassium ferrocyanide is satisfactory. 



