1914] 



Anton R. Rose and Katherine R. Coleman 



415 



ammonia apparatus is used and ammonia may be determined at the 

 same time. After the cylinder has been slightly warmed, 5 c.c. of 

 the sample and 30 c.c. of water warmed to 50-60° C. are introduced, 

 and then about 5 gm. of the soja bean flour added. At the end of 

 30 min., about 5 c.c. of a saturated sol. of sodium carbonate are 

 drawn into the cylinder containing the sample. The air current, 

 which is passed through the apparatus continuously after the addi^ 

 tion of the bean flour, is maintained until all the ammonia is trans- 

 ferred to the cylinder containing the Standard acid sol, after which 

 the excess of acid is titrated in the usual manner. Crude petroleum 

 is used to prevent the f rothing. 



The accompanying table (1-2) give the data on which these 

 two procedures are based. 



TABLE 2 



Comparative data pertaining to methods for the determination of urea^ 



In noting the difference in the readings on the colorimeter, the 



sign + is used in the accompanying table to indicate this Variation. 



With Folin's micro method and the micro-urease method the results 



are always in close agreement. The method of Benedict always 



gives a trifle more nitrogen than the macro-urease method unless 



every precaution is taken to have all the ammonia transferred from 



the urine cylinder to the Standard acid cylinder in the latter case. 



If the cylinders are warmed and sufficient time of aspiration 



allowed, these two methods will give identical answers. 



1 In this table the macro-urease data represent regulär routine work of the 

 laboratory, these and the Benedict data having been obtained by Mr. Bogen. The 

 micro determinations were made by Miss Coleman on the same samples at a 

 much later date. The samples are of urine and represent 100 c.c. in each case. 

 Rose. 



