PHYSIOLOGICAL CHEMISTRY 



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same way as the second and containing 10 c.c. NjlQ acid and some ammonia free 

 water, follows this, otherwise all the ammonia would not be caught by the acid. 

 The tubing connected with this tube goes to a Bunsen's air-pump e attached to a 



a 



FIG. 247. Folin's apparatus for estimating ammonia. 



tap /. A quick stream of air (600-700 litres per hour) is made to pass through 

 the apparatus for 1 hours. The acid in the two last test tubes is then washed 

 into an Erlenmeyer flask and titrated with jV/10 alkali. For titrating, Folin 



FIG. 248. Shaffer's method of estimating ammonia in urine. 



recommends 2 drops of a 1 per cent, solution of Alizarin red (for 200-300 c.c. 

 fluid), the titration being carried on till a pink (not a violet) colour just appears. 

 This indicator gives a better end-point than methyl orange. 



Shaffer's vacuum distillation method of estimating ammonia in urine is as accurate 

 as Folin's and much more rapid. 



2E 



