THE URINE. 345 



c. c., we have then 20.5 - {(39.6 - 20.5)x0.08( = 20.5 - 1.53 = 

 18.97, and the corrected quantity of mercury solution is therefore 

 '18.97 c. c. If the measured c. c. of the filtrate (in this case 25.8 c. c.) 

 corresponds to 10 c. c. of the original urine, then the amount of 

 urea is 18.97 X 0.01 = 0.1897 = 18.97 p. m. urea. 



Besides the urea other nitrogenized constituents of the urine 

 are precipitated by the mercury solution. By the titration we 

 really do not obtain the quantity of urea, but, as PFLUGER has 

 shown, the total quantity of nitrogen in the urine expressed ad 

 urea. As the urea contains 46.67 p. c. N, the total quantity of 

 nitrogen in the urine may be calculated from the quantity of urea 

 found. 



The results obtained by LIEBIG-PFLUGER'S titration method 

 for the total nitrogen, PFLUGER has shown, correspond well with 

 the results obtained by KJELDAHI/S method, which was first (1861) 

 used by ALMEN for 1 urea determinations, and modified by PFLUGER 

 and BORLAND. This method consists in heating the urine a cer- 

 tain time with an excess of concentrated or fuming sulphuric acid 

 (5 c. c. urine and 40 c. c. sulphuric acid) until all the nitrogen has 

 been converted into ammonia, and after the addition of an excess 



of caustic soda the ammonia is distilled into ^ sulphuric acid and 



the amount of ammonia distilled over is determined by titration. 



BUNSEN'S UREA DETERMINATION. The principle of this 

 method consists in heating the urine or urea solution in a sealed 

 glass tube to a high temperature with an alkaline barium-chloride 

 solution. The urea splits into carbon dioxide and ammonia, which 

 may be determined separately. This method has been very care- 

 fully tested by PFLUGER and his pupils BORLAND and BLEIBTREU, 

 and essentially improved. They found that very accurate results 

 can be obtained by this method if the other nitrogenized constit- 

 uents of the urine are first precipitated by a mixture of hydro- 

 chloric acid and phospho-tungstic acid, and then the filtrate made 

 faintly alkaline with milk of lime, and lastly heated with alkaline 

 barium-chloride solution in a sealed tube. The carbon dioxide 

 and the ammonia can be determined (by distilling with magnesia 



and receiving the distillate in acid and titrating). In the last 



