URINE: QUANTITATIVE ANALYSIS. 



377 



graduated portion. Now allow i FlG - II9 - 



c.c. of urine 1 to flow from tube B 



into tube A and after the evolution 



of gas bubbles has ceased (10-20 



minutes) take the reading of the 



graduated scale on tube A. 



In common with all other meth- 

 ods which are based upon the de- 

 composition of urea by means of 

 hypobromite solution, this method 

 is not absolutely correct. It is, 

 however, sufficiently accurate for 

 ordinary clinical purposes. 



Calculation. Observe the reading 

 on the graduated scale of tube A. 

 This tube is so graduated as to rep- 

 resent the weight of urea, in grams, 

 per cubic centimeter of urine. If we 

 wish to compute the percentage of 

 urea present this may be done very 

 readily by simply moving the deci- 

 mal point two places to the right, e. 

 g. t if the reading is 0.02 gram the 

 urine contains 2 per cent of urea. 



3. Folin's Method. This is one 

 of the most accurate methods yet 

 devised for the determination of 

 urea in the urine. The procedure 



is as follows: Place 5 c.c. of urine in a 200 c.c. Erlenmeyer 

 flask and add to it 5 c.c. of concentrated hydrochloric acid, 20 grams 

 of crystallized magnesium chloride, a piece of paraffin the size of a 

 hazel nut and 2-3 drops of a i per cent aqueous solution of " aliz- 

 arin red." Insert a Folin safety tube (Fig. 121, p. 379) into the 

 neck of the flask and boil the mixture until each drop of reflow from 

 the safety tube produces a very perceptible bump; the heat is then 

 reduced somewhat and continued one and one-half hours. The 

 contents of the flask must not remain alkaline and to obviate this, 

 at the first appearance of a reddish tinge in the contents of the 



1 If the content of urea in the urine under examination is large, the urine 

 may be diluted with water before determining the urea. If this is done it must 

 of course be taken into consideration in computing the content of urea. 



HUFNER'S UREA APPARATUS. 



