— 141 — 



in which the odour exhaled by the flowers is allowed to act upon 

 oxalic acid. Weehuizen has now successfully tested the practicabil- 

 ity of the colour reactions for indol indicated by Steensma 1 ) for 

 showing the presence of this combination in the scent of flowers. 

 The crushed flowers were extracted with alcohol for about 5 minutes, 

 and a little vanillin or p-dimethylamino benzaldehyde was dissolved 

 into the filtrate, whereupon after the addition of a few drops of con- 

 centrated hydrochloric acid the characteristic red colorations ensued. 

 When p-dimethylamino benzaldehyde was employed, the reaction could 

 be made still plainer by the addition of a trace of sodium nitrite. 

 As phloroglucinol gives the same colour reactions, another process, which 

 may be followed when this combination is present, is that of exposing 

 filtering paper or spun glass soaked in a 1 °/ solution of vanillin or 

 p-dimethylamino benzaldehyde in a mixture of equal volumes of alcohol 

 and concentrated hydrochloric acid, for a long time to the exhalations 

 of the flowers. When dried at ordinary temperature ared coloration 

 will then take place. The last-named process is also to be applied 

 when the alcoholic extracts of the flowers are coloured. 



In this manner the presence of indol could be shown in the white 

 flowers of Murraya exotica L. (Murraya sumatra?ia Roxb.) and in the 

 spadices of one of the numerous varieties of Caladium with variegated 

 leaves. 



x ) Zeitschr. f. physiol. Chem. 47 (1906), 25. 



