I/O PHYSIOLOGICAL CHEMISTRY. 



result. Compare this result with the result of the similar test on 

 skatole. 



Tests for Skatole. 



i. Herter's Para-dimethylaminobenzaldehyde Reaction. 1 

 To 5 c.c. of the distillate or aqueous solution under examination 

 add i c.c. of an acid solution of para-dimethylaminobenzaldehyde 2 

 and heat the mixture to boiling. A purplish-blue coloration is 

 produced 3 which may be intensified through the addition of a few 

 drops of concentrated hydrochloric acid. If the solution be cooled 

 under running water it loses its purplish tinge of color and becomes 

 a definite blue. The solution at this point may be Somewhat opal- 

 escent through the separation of uncombined para-dimethylamino- 

 benzaldehyde. Care should be taken not to add an excess of hy- 

 drochloric acid inasmuch as the end-reaction has a tendency to fade 

 under the influence of a high acidity. 



A rough idea regarding the actual quantity of skatole in a mix- 

 ture may be obtained by extracting this blue solution with chloro- 

 form and subsequently comparing this chloroform solution, by 

 means of a colorimeter (Duboscq), with the maximal reaction, ob- 

 tained with a skatole solution of known strength. 



2.. Color Reaction with Hydrochloric Acid. Acidify some of 

 the residue with concentrated hydrochloric acid. Note the pro- 

 duction of a violet color. 



3. Acidify some of the residue with nitric acid and add a few 

 drops of a potassium nitrite solution. Note the white turbidity. 

 Compare this result with the result of the similar test on indole. 



Tests for Phenol and Cresol. 



1. Color Test. Test a little of the solution with Millon's re- 

 agent. A red color results. Compare this test with the similar one 

 under Tyrosine ( see page 83 ) . 



2. Ferric Chloride Test. Add a few drops of neutral ferric 

 chloride solution to a little of the residual fluid. A dirty bluish- 

 gray color is formed. 



3. Formation of Bromine Compounds. Add some bromine 

 water to a little of the fluid under examination. Note the crys- 

 talline precipitate of tribromphenol and tribromcresol. 



1 Herter: Bacterial Infections of the Digestive Tract, 1907, p. 141. 

 2 Made by dissolving 5 grams of para-dimethylaminobenzaldehyde in 100 c.c. 

 of 10 per cent sulphuric acid. 

 8 If the color does not appear add more of the aldehyde solution. 



