PHYSIOLOGICAL CHEMISTRY 



Benzoic acid has been detected in the urine of the rabbit and dog. It is 

 also said to occur in human urine accompanying renal disorders. The 

 benzoic acid probably originates from a fermentative decomposition of 

 the hippuric acid of the urine. Benzoic acid and glycocoll are synthe- 

 sized in the kidney and elsewhere 1 to form hippuric acid (see page 585). 

 Certain fruits and berries contain considerable benzoic acid; e.g., cran- 

 berries have been shown to contain 0.06 per cent. 2 



EXPERIMENTS 



1. Solubility. Test the solubility of benzoic acid in water, alcohol, and ether. 



2. Crystalline Form. Recrystallize some benzoic acid from hot water, ex- 

 amine the crystals under the microscope, and compare them with those re- 

 produced in Fig. 127. 



FIG. 127. BENZOIC ACID. 



3. Sublimation. Place a little benzoic acid in a test-tube and heat over a 

 flame. Note the odor which is evolved and observe that the acid sublimes in the 

 form of needles. 



4. Dissolve a little sodium benzoate in water and add a solution of neutral 

 ferric chloride. Note the production of a brownish-yellow precipitate (salicylic 

 acid gives a reddish-violet color under the same conditions). Add ammonium 

 hydroxide to some of the precipitate. It dissolves and ferric hydroxide is formed. 

 Add a little hydrochloric acid to another portion of the original precipitate and 

 stand the vessel away over night. What do you observe? 



NUCLEOPROTEIN 



The nubecula of normal urine has been shown by one investigator 

 to consist of a mucoid containing 12.7 per cent of nitrogen and 2.3 

 per cent of sulphur. This body evidently originates in the urinary 



1 Kingsbury and Bell: Jour. BioL Chem., 21, 297, 1915. 



2 Radin [quoted by Blatherwick (Arch. Int. Med., 14, 409, 1914) from unpublished data]. 



