CHAPTER XXII. 



URINE: QUANTITATIVE ANALYSIS. 

 I. Protein. 



1. Scherer's Coagulation Method. The content of coagulable 

 protein may be accurately determined as follows : Place 50 c.c. of 

 urine in a small beaker and raise the temperature of the fluid to 

 about 40 C. upon a water-bath. Add dilute acetic acid, drop by 

 drop, to the warm urine, to precipitate the protein which will sep- 

 arate in a flocculent form. Care should be taken not to add too 

 much acid; ordinarily less than twenty drops is sufficient. The 

 temperature of the water in the water-bath should now be raised to 

 the boiling-point and maintained there for a few minutes in order 

 to insure the complete coagulation of the protein present. Now 

 filter the urine 1 through a previously washed, dried and weighed 

 filter paper, wash the precipitated protein, in turn, with hot water, 

 95 per cent alcohol and with ether, and dry the paper and precipitate, 

 to constant weight, in an air-bath at 110 C. Subtract the weight 

 of the filter paper from the combined weight of the paper and 

 precipitate and calculate the percentage of protein in the urine 

 specimen. 



Calculation. To determine the percentage of protein present in 

 the urine under examination, multiply the weight of the precipitate, 

 expressed in grams, by 2. 



2. Esbach's Method. This method depends upon the precipi- 

 tation of protein by Esbach's reagent 2 and the apparatus used in 

 the estimation is Esbach's albuminometer (Fig. 117, p. 367). In 

 making a determination fill the albuminometer to the point U with 

 urine, then introduce the reagent until the point R is reached. Now 

 stopper the tube, invert it slowly several times in order to insure the 



1 If it is desired the precipitate may be filtered off on an unweighed paper, and 

 its nitrogen content determined by the Kjeldahl method (see p. 381). In order 

 to arrive at correct figures for the protein content it is then simply necessary to 

 multiply the total nitrogen content by 6.25 (see p. 412). Correction should be 

 made for the nitrogen content of the filter-paper used unless this factor is. 

 negligible. 



2 Esbach's reagent is prepared by dissolving 10 grams of picric acid and 20 

 grams of citric acid in i liter of water. 



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