URINE: QUANTITATIVE ANALYSIS. 



375 



FIG. 1 1 8. 



fill the tube with sodium hypobromite solution. 1 Close the opening 

 in the end of the tube with a rubber stopper, incline the tube to 

 allow air-bubbles to escape and finally invert the tube and fix the 

 stoppered end in the saucer-shaped vessel. By means of the grad- 

 uated pipette rapidly introduce i c.c. 

 of urine 2 into the hypobromite solution 

 through the side opening of the bulbed- 

 tube. Withdraw the pipette immedi- 

 ately after the urine has been intro- 

 duced. When the decomposition of 

 the urea is completed (10-20 minutes) 

 gently tap the bulbed-tube with the 

 finger in order to dislodge any gas 

 bubbles which may have collected on 

 the inner surface of the glass. The 

 atmospheric pressure should now be 

 equalized by attaching the funnel-tube 

 to the bulbed-tube at the side opening 

 and introducing hypobromite solution 

 into it until the columns of liquid in 

 the two tubes are uniform in height. 

 The graduated scale of the bulbed- 

 tube should now be read in order 

 to determine the number of cubic 



mnmimmmiiin 



MARSHALL'S UREA APPARATUS. 

 (Tyson.) 



a, Bulbed measuring tube ; b, 

 Centimeters of nitrogen gas evolved, saucer-shaped vessel ; c, graduated 

 T, r , i r pipette ; d. funnel-tube. 



By means of the appended formula 



the weight of the urea present in the urine under examination may 



be computed. 



Calculation. 3 By properly substituting in the following formula 

 the weight of urea, in grams, contained in the volume of urine de- 

 composed (i c.c. or more) may readily be determined: 



1 The ingredients of the sodium hypobromite solution should be prepared in the 

 form of tzvo separate solutions. When needed for use mix equal volumes of 

 solution a, solution b and water. 



(a) Dissolve 125 grams of sodium bromide in water, add 125 grams of bromine 

 and make the total volume of the solution i liter. 



(b) A solution of sodium hydroxide having a specific gravity of 1.250. This 

 is approximately a 22.5 per cent solution. 



Preserve both solutions in rubber-stoppered bottles. 



~ Ordinarily i c.c. of urine is sufficient ; more may be used, however, if its 

 content of urea is very low. 



3 0.003665 = coefficient of expansion of gases for i C. 354.5 = number of c.c. 

 of nitrogen gas evolved from i gram of urea. 



