118 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



of ammonia-free air into the cylinder; the acid in the second 

 flask absorbs the ammonia liberated by the urine and carried 

 over by the current of air sucked through the system. Suc- 

 tion should be continued for about two hours. 



N 

 The collection flask should finally be titrated with ^ NaOH 



and the amount necessary for neutralization subtracted from 

 the number of cubic centimeters of acid originally taken. 

 The remainder, when multiplied by 0.0017, gives the amount 

 (grams) of ammonia in 25 c.c. of urine. 



PROTEIN. 



Quantitative Estimation. 



Of the numberless methods which have been suggested 

 for the quantitative determination of the total protein in 

 the urine, the following has received perhaps the most marked 

 approbation from the clinicians. It is based upon the quan- 

 titative precipitation by picric acid in the presence of an 

 organic acid, of all forms of proteins which appear in the 

 urine under abnormal conditions. The results obtained 

 are sufficiently accurate if the urine does not contain over 

 0.4 per cent protein. When more than this is present, the 

 urine must be diluted with water in such amounts as to allow 

 the percentage to fall below that figure. 



The procedure is as follows : 



Fill the albuminometer to the mark "u" with urine acidi- 

 fied with a few drops of dilute acetic acid, and add Esbach's 

 reagent to "R ". Stop the end of the tube with a cork. By 

 inverting several times the contents of the tube can be thor- 

 oughly mixed without producing any froth on the top of the 

 mixture. Allow the corked tube to stand upright for 24 

 hours and then read off the height of the precipitate on the 

 scale, which indicates directly the number of grammes of dry 

 protein contained in a liter of the urine. 



