MILK, BLOOD AND URINE 23 1 



EXPERIMENT STUDY XXXI 



Urine 



(i) Determine the amount of urea in normal urine by means of the 

 ureometer as in Experiment XIX, i. 



(2) Isolation of Urea from Urine. Evaporate 2-3 liters of urine in 

 a large evaporating dish in a hood until it is the consistency of sirup. 

 Cool and add concentrated nitric acid as long as crj^stals form. 

 Filter, with suction on a Buchner funnel. The crystalline product is 

 urea nitrate. Recrystallize and decolorize to light straw color with 

 potassium permanganate solution. Dissolve the urea nitrate in 

 water and add barium carbonate as long as effervescence occurs. 

 Filter off any excess of barium carbonate and evaporate the filtrate 

 to dryness. Extract the dry residue with hot alcohol, filter, evap- 

 orate the alcoholic extract to a small volume, cool, and allow the 

 urea to crystallize out. Filter off the crystals of pure urea and 

 examine them as in (i). 



/NH2 /NH2-HNO3 yNHa 



0C< +HN03->0C< +BaC03->0C< +Ba(N03)2 



^NH2 ^NH2 ^NH2 



Urea in urine Urea nitrate Urea 



(3) Albumin, Heller's Ring Test. Place 5 c.c. of dilute egg albumin 

 solution in a test tube or, better, a conical test glass. By means of a 

 pipette lowered to the bottom of the test tube let an equal volume of 

 pure concentrated nitric acid flow underneath the albumin solution 

 so as to keep the two layers. Note the cloudy precipitate form at 

 the junction of the two liquids. Repeat several times, diluting the 

 egg albumin solution ten times at each successive trial. Note the 

 delicacy of the test. This is used as a clinical test for albumin when 

 present in small amounts in urine in cases of the disease known as 

 Nephritis or Bright's Disease. 



(4) Glucose. To a sample of urine add about 0.5 per cent of glu- 

 cose, (a) Test the urine for glucose with Fehling's solution as de- 

 scribed under glucose (p. 114). (b) Test similarly, using Benedict's 

 modified Fehling's solution. (See Hawk, " Practical Physiological 

 Chemistry," p. 329, for details in regard to this test.) (c) Dilute the 

 urine with an equal volume of fresh urine five times and repeat with 

 each solution. 



