122 



PRACTICAL PHYSIOLOGY. 



[XIX. 



and on lowering the collecting tube the water will stand at zero 



inside and outside the tube. 



((f.) Mix the urine gradually with the hypobromite solution by 

 gently tilting over the flask. Gas is rapidly given ofF, the COg is 

 absorbed by the caustic soda, while the N is collected in the 

 graduated measuring tube. 



(e.) Place the flask in a jar of water at the same temperature as 

 that in the tall jar, and slightly lower the measuring tube. After 



FlO. 63.— Steele's Apparatus for Urea. A. Flask for hypobromite ; B. Tube for 

 urine ; C. Burette ; D. Vessel with water ; £. Vessel with water to cool A. 



all eff'crvescence has ceased, and when the N collected in the col- 

 lecting tube has cooled to the temperature of the room— i.e., in five 

 to ten minutes — raise the collecting tube until the fluid inside and 

 outside stands at the same level. Eead off" the graduated tube; 

 this gives the percentage of urea. Or if the burette be graduated 

 in cc. read off" the number of cc. and calculate the amount of urea 

 from the amount of N evolved. 



It is to be remembered that other bodies in the urine, such as 

 uric acid (urates) and kreatinin — but not hippuric acid — also yield 



