172 THE UEINE. 



uranium solution, drop by drop, until a greenish color is produced. 

 The phosphoric acid has then been precipitated. Since 1 cubic 

 centimeter of the uranium solution ought to precipitate 0.005 

 gramme of P 2 6 , exactly 20 cubic centimeters should have been 

 used for the 50 cubic centimeters of sodium phosphate. If this is 

 not the quantity which has been used, first ascertain accu- 

 rately how much is needed and then dilute the uranium solution 

 so that 1 cubic centimeter precipitates 0.005 gramme of P 2 O 6 . If, 

 for instance, 17.5 cubic centimeters have been used instead of 20 

 cubic centimeters there must be added 2.5 cubic centimeters of 

 water for every 17.5 cubic centimeters of the uranium solution. 



The amount of P 2 O 6 in urine can now be determined in the 

 same manner, using urine instead of the sodium phosphate solu- 

 tion. Calculate the percentage of P 2 O 6 present, knowing that there 

 is 0.005 gramme for each cubic centimeter of uranium solution 

 which has been used. 



If it desired to determine the amount of phosphoric acid 

 combined with the alkaline earths (calcium and magnesium), as 

 distinguished from the phosphates of sodium and potassium, the 

 former class can be precipitated from 200 cubic centimeters of 

 urine by ammonium hydrate and, after settling, can be removed 

 by nitration. Wash the precipitate well with ammonium hydrate, 

 then pierce the filter and rinse the precipitate by a jet of water 

 into a beaker. Dissolve it in as small a quantity of acetic acid as 

 possible, add 5 cubic centimeters of the sodium acetate solution, 

 dilute to 50 cubic centimeters and titrate as in the preceding 

 operation. This gives the P 2 O 6 which was united with the calcium 

 and magnesium. If the total has been determined, the difference 

 represents the phosphoric acid originally combined with sodium 

 and potassium. 



SULPHATES. 



The sulphates of the urine are of two classes: (1) 

 those of which the base is a metal, like K 2 S0 4 and Na^SO^ 

 and (2) those in which a part or the whole of the base has 

 been replaced by an organic radical, like KC 6 H 5 S0 4 . 



