THE URINE. 381 



called PHOSPHATE DIABETES by TEISSIER. The statements in 

 regard to the amount of phosphate in the urine in rachitis and in 

 osteomalacia are somewhat contradictory. A diminished elimina- 

 tion of phosphoric acid has been observed by STOKVIS in arthritis. 



Quantitative estimation of phosphoric acid in the urine. This 

 estimation is most simply performed by titrating with a solution of 

 uranium acetate. The principle of the titration is as follows : A 

 warm solution of phosphates containing free acetic acid gives a 

 whitish-yellow precipitate of uranium phosphate with a solution of 

 a uranium salt. This precipitate is insoluble in acetic acid, but 

 dissolves in mineral acids, and on this account we always add in 

 titrating a certain quantity of sodium acetate solution. Potassium 

 ferrocyanide is used as the indicator, which does not act on the 

 uranium-phosphate precipitate, but gives a reddish-brown precipi- 

 tate or coloration in the presence of the smallest amount of soluble 

 uranium salt. The solutions necessary for the titration are : 1. A 

 solution of a uranium salt of which each c. c. corresponds to 0.005 

 grm. P 2 5 and which contains 20.3 grms. uranium oxide per litre. 

 20 c. c. of this solution corresponds to 0.100 grm. P 2 5 . 2. A solu- 

 tion of sodium acetate ; 3. A freshly-prepared solution of potas- 

 sium ferrocyanide. 



The uranium solution is prepared from uranium nitrate or acetate. Dis- 

 solve about 35 grms. uranium acetate in water, add some acetic acid to facilitate 

 solution, and dilute to one litre. The strength of this solution is determined 

 by titrating with a solution of sodium phosphate of known strength (10.085 

 grms. crystallized salt in 1 litre, which corresponds to 0.100 grm. P 2 O 5 in 

 50 c. c.). Proceed in the same way as in the titration of the urine (see below) 

 and correct the solution by diluting with water, and titrate again until 20 c.c. 

 of the uranium solution correspond exactly to 50 c. c. of the above phosphate 

 solution. 



The sodium-acetate solution should contain 10 grms. sodium acetate and 10 

 grms. cone, acetic acid in 100 c. c. For each titration 5 c. c. of this solution is 

 used with 50 c. c. of the urine. 



In performing the titration, mix 50 c. c. of filtered urine in a 

 beaker with 5 c. c. of the sodium acetate, cover the beaker with a 

 watch-glass, and warm over the water-bath. Then allow the ura- 

 nium solution to flow in from a burette, and, when the precipitate 

 does not seem to increase, place a drop of the mixture on a porce- 

 lain plate with a drop of the potassium-ferrocyanide solution. If 

 the amount of uranium solution employed is not sufficient; the color 

 remains pale yellow and more uranium solution must be added; 

 but as soon as the slightest excess of uranium has been used, the 

 color becomes faint reddish brown. When this point has been 

 obtained, warm the solution again and add another drop. If the 

 color remains of the same intensity, the titration is ended ; but if 



