OP ARTS AND SCIENCES. 213 



Properties. It crystallizes from glacial acetic acid in rosettes of a 

 vivid yellow color without the orange shade of curcumin, which are 

 made up of very characteristic rhombic plates ; melting-point, 154°. 

 It is more soluble in glacial acetic acid than in any other solvent, 

 especially when the acid is hot; less soluble in alcohol than curcumin; 

 slightly soluble in ether and benzol; essentially insoluble in ligroine 

 and carbonic disulphide. Strong sul^jhuric acid dissolves it, becoming 

 blood-red in transmitted light, green like rosauilin in reflected light ; 

 the red color is somewhat more jDurple than that produced by cur- 

 cumin. Sodic hydrate in aqueous solution acts upon it very slowly, 

 and not rapidly, even if dissolved in dilute alcohol ; the red solution 

 thus obtained gives w^ith hydrochloric acid a viscous brown mass with 

 a low melting-point, which seems to be impure monacetcurcumin. 

 Sodic carbonate and alcohol give an orange solution looking like that 

 of potassic dichromate. According to the formula given by us to cur- 

 cumin in our first paper, this substance should be a mixed anhydride 

 of curcumin and acetic acid, with the other acetyl group attached to 

 the phenol oxygen, as in the monacet-compound, — a constitution 

 which would be expressed by the following formula: — 



Q^U^X^CU.;) (OC2H3O) (CgHeCOOC.HgO). 



That the carboxyl group is affected by the introduction of the 

 second acetyl is shown by the fact that alkaline reagents act upon it 

 only after some time, and then evidently decompose it ; whereas the 

 monacet-compound is attacked by them instantly, and the action con- 

 sists only in the formation of a salt : but, on the other hand, the sub- 

 stance is more stable than acid anhydrides are usually, as is shown by 

 this very action with alkalies, and by the fact that it can be boiled 

 with water for many hours without undergoing any change in melt- 

 ing-point, or the formation of any soluble acid. 



Action of Phosphoric Oxychloride on Curcumin, 



Of all the reactions of curcumin, which we have observed, this is 

 by far the most striking, and we have decided therefore to describe 

 it at some length, although we have not succeeded in determining the 

 nature of the substance formed. If a few drops of phosphoric oxy- 

 chloride are added to some curcumin suspended in ligroine, its orange- 

 yellow color is converted instantly into a rich reddish purple, which in 

 reflected light appears bronze-green with a metallic lustre, between 

 the colors of rosanilin and Hofmann's violet. To prepare the substance 

 in quantity, the curcumin was rubbed in a mortar with phosphoric 



