ANALYSIS OF URINE 



553 



(3) Equally good results are given by Folin's method : 



5 c.c. of urine are heated with 20 gm. of crystallised magnesium chloride, 

 5 c.c. of concentrated hydrochloric acid, a 

 few c.c. of thick paraffin and a few drops of 

 alizarin red, under a reflux condenser of a 

 U-shaped pattern, shown in Fig. 75, in a 200 

 c.c. conical or round bottom flask. The mix- 

 ture is heated so as to drive off water into the 

 condenser. As soon as the drops falling from 

 the condenser produce a distinct bump the 

 heating is lessened so that condensed drops fall 

 about every 20 seconds. The heating is con- 

 tinued in this way for i hour. If the solution 

 becomes alkaline during the hydrolysis of the 

 urea, a few c.c. of the acid water in the con- 

 denser are tipped into the flask. 



When the hydrolysis is complete, the con- 

 tents of the flask are washed into a 700 or 

 1000 c.c. round bottom flask ; the ammonia is 

 distilled off as in Kjeldahl's method, and col- 

 lected in 50 c.c. of -iN acid, but not more 

 than 10 c.c. of caustic soda (40 per cent.) 

 should be added to make the contents of the 

 flask alkaline, as magnesium hydroxide is pre- 

 cipitated and causes bumping. The distilla- 

 tion requires about i hour. 



The amount of *iN acid neutralised, less 

 the amount of *iN acid found for the am- 

 monia which is included in this estimation, 

 per 5 c.c. gives the amount of urea : 



i c.c. 'iN alkali 



0014 gm urea nitrogen = '003 

 gm. urea. 



FIG. 75. 



Allantoine. 



AlUntoine is present in human urine in only minute quantities, but in dogs 

 and many other animals it takes the place of uric acid. Allantoine is hydrolysed 

 by hydrochloric acid in the same way as urea; it is readily estimated by 

 difference between the hydrolysis value with hydrochloric acid as above and 

 the urea value by means of urease, both with 5 c.c. of urine. 1 



1 Biochem. J., 1914, 8, 70. 



