i6o 



PHYSIOLOGICAL CHEMISTRY. 



melts, then turns brown and finally carbonizes as the temperature is 

 raised. Note the suffocating odor. What is it? < 



(c) Test the solubility of the crystals in water and in alcohol. 



(d) Grind up a crystal with four times its volume of dry sodium 

 carbonate and fuse on platinum foil. Cool the residue, transfer 

 it to a test-tube and dissolve it in water. Add a little dilute sul- 

 phuric acid and note the odor of hydrogen sulphide. Hold a piece 



FIG. 43. 



TAURINE. 



of filter paper, moistened with a small amount of lead acetate, over 

 the opening of the test-tube and observe the formation of lead sul- 

 phide. 



10. Preparation of Glycocoll. Concentrate the alcoholic filtrate 

 from the last experiment (9) until no more alcohol remains. The 

 glycocoll is present here in the form of an hydrochloride and may 

 be liberated from this combination by the addition of freshly pre- 

 cipitated lead hydroxide or by lead hydroxide solution. Remove 

 the lead by hydrogen sulphide. Filter and decolorize the filtrate 

 by animal charcoal. Filter again, concentrate the filtrate and set it 

 aside for crystallization. Glycocoll separates as colorless crystals 

 (Fig. 44, p. 161). 



11. Synthesis of Hippuric Acid. To some of the glycocoll pre- 

 pared in the last experiment or furnished by the instructor, add 

 a little water, about i c.c. of benzoyl chloride and render alkaline 

 with potassium hydroxide solution. Stopper the tube and shake 

 it until no more heat is evolved. Now render strongly alkaline 

 with potassium hydroxide and shake the mixture until no odor of 



