PUTREFACTION PRODUCTS OF PROTEIDS. 171 



REACTIONS OF SKATOL. 



(a) Skatol dissolves in concentrated hydrochloric acid 

 with a violet color. 



(6) If the aqueous solution be acidified with nitric acid 

 and then a few drops of potassium nitrite solution be added, 

 no red color results, as in the case of indol, but only a white 

 turbidity. 



3. Phenol. 



For the properties and reactions of this substance see 

 chapter on Urine, page 106. 



4- Paracresol, C 6 H 



This substance occurs mixed with other cresols (ortho- 

 and meta-) in coal-tar. In its general properties it resembles 

 phenol very closely, though it melts at a lower temperature 

 (36) and is far more difficultly soluble in water than phenol. 

 It is a stronger antiseptic than phenol and is less poisonous. 

 When introduced into the animal organism it appears in the 

 urine for the most part as paracresyl- sulphuric acid (which 

 also occurs in horse-urine), in part also as paraoxy-benzoic 

 acid. In addition to the paracresol small quantities of the 

 other cresols are also formed in the putrefaction of proteids. 



The reactions of paracresol in aqueous solution are very 

 similar to those of phenol. The color with ferric chloride 

 solution is, however, not pure blue, but a dirty grayish blue. 



5. Phenyl-acetic Acid, C 6 H 5 CH 2 C0 2 H. 



This substance crystallizes in large, extremely thin leaf- 

 lets which melt at 76.5. It is readily soluble in alcohol, 

 ether, and hot water, but only slightly soluble in cold water. 

 On oxidation with potassium bichromate and sulphuric acid 

 it yields benzoic acid. In the organism it is converted into 



