100 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



solutions a green fluorescence which is greatly augmented 

 if ammonia and alcoholic ZnCl ? , solution are added. Acid 

 alcoholic solutions of urobilin also show a distinct absorption- 

 band between 6 and F. 



In constitution urobilin possesses the same acidic proper- 

 ties which characterize all the animal pigments. It forms 

 insoluble compounds with bases, and is completely precipi- 

 tated from its solution by saturation with (NH 4 ) 2 S0 4 (differ- 

 ing from urochrome). 



(a) To 50 c.c. of urine faintly acidified with H 2 S0 4 add 

 ammonium sulphate (in substance) to saturation. Filter off 

 the precipitate and dissolve it in alcohol containing a few 

 drops of concentrated HC1. What sort of a body is urobilin? 



(6) To 50 c.c. of urine add an equal mixture of neutral 

 and basic lead acetate until the precipitation is complete. 

 Filter and allow the precipitate to drain as dry as possible. 

 Then place it and the filter-paper in an evaporating-dish 

 half full of 95 per cent alcohol acidulated with HC1. Warm 

 over the water-bath until the alcohol is well colored. Filter 

 and examine the solution in the spectroscope. Now add a 

 few drops of NH 4 OH and a few c.c. of an alcoholic zinc 

 chloride solution. Note the fluorescence. In what way is 

 the coloring matter of the urine precipitated? 



(c) Shake 25 c.c. of urine with 2 to 3 drops of pure HC1 

 and 5 c.c. of chloroform. Remove the chloroform and 

 stratify upon it a few c.c. of a solution of zinc acetate in 

 alcohol. Notice the green ring; by shaking, the solution 

 becomes fluorescent. 



CARBOHYDRATES AND RELATED BODIES. 



Under apparently normal conditions, reducing sub- 

 stances of a carbohydrate nature appear in the urine in small 



