URINE. 115 



Quantitative Estimation. 



Reagents necessary: 



Hypobromite solution (see Appendix). 



In making use of the Doremus or similar ureometers, it is 

 advisable to so dilute the urine that the content of urea 

 will not exceed approximately 0.5 per cent. 



Rinse the ureometer first with water and then fill it with 

 the hypobromite solution, so that when the apparatus is per- 

 pendicular and no air is at the top, the amount of fluid in 

 the bulb covers the opening from it to the upright tube. 

 Then draw up into the pipette the exact amount of urine, 

 and placing it under the surface of the solution with the pipette 

 tip well into the space below the upright tube, force the urine 

 out of the pipette slowly, noting that the bubbles generated 

 all pass upward into the closed tube. Care must be taken 

 that the last drop of urine is expelled from the pipette with- 

 out allowing any air to escape from it also. Allow the reac- 

 tion and collection of gas to go on for half an hour, then make 

 a reading on the scale on the areometer of the apparatus. 

 The readings become more accurate when the whole appara- 

 tus is immersed in a beaker of water in such a manner that 

 the levels of the fluids in the two vessels correspond. The 

 figures on the scale of the instrument indicate grammes of 

 urea in 1 c.c. of the urine. 



URIC ACID (HOPKINS-FOLIN METHOD). 



The following method seems to combine considerable 

 accuracy with simplicity and rapidity of performance. It 

 is based upon the fact of the precipitation of the soluble 

 urates by saturation with ammonium salts (Hopkins); 

 and additional accuracy has been obtained by the previous 

 removal of certain substances, e.g., mucoids, phosphates 



