318 Proceedings of the Royal Irish Academy, 



Dibenzyl-dichromone was prepared by boiling di-a-phenylaoetyl-aceto- 

 resoreinol-dimethyletlier with couceiitraied hydriodic acid. Jts yield was 

 better than that of dichromone, the substance beiug less contaminated by 

 impurities. It consists of yellowish-white prismatic needles, which melt at 

 223-224" C, and give a faint yellow solution in sulphuric acid, with a well- 

 marked heliotrope fluorescence. 



Experimental. 



A. — Dicliro'riio^ie. 



Dichromone was obtained by the action of hydrobromic acid on the 



methyl and the ethyl esters of dimethoxyisophthaloyl-dipyruvic acid, on the 



one hand, and on diformyl-aceto-resorcinol-dimethylether, on the other hand. 



CO CO 



I. A mixture of 2 g. of methyl dimethoxyisophthaloyl-dipyruvate and 

 80 c.c. of hydrobromic acid (sp. g. 1'46) was heated to 126' 0. for 8 hours. 

 On addition of the reaction product to a concentrated solution of sodium 

 bisulphite a dark-coloured tarry precipitate was obtained. The mixture was 

 extracted with chloroform, and the chloroform solution was dehydrated over 

 anhydrous potassium carbonate. A greenish residue was obtained by 

 evapoiating the chloroform. It was recrystallised twice from a mixture of 

 alcohol and acetone ; but this treatment was insufficient to separate it from 

 a green dye with which it was intimately mixed. When, however, ether 

 was added to a chloroform solution of the mixture a colourless substance was 

 precipitated. This substance, which proved to be dichromone, was re- 

 crystallised from alcohol. It melted at 176-177° C, and gave on analysis the 

 following results : — 



0-1739 substance gave 0-4281 COa and 0-0438 H,0, 

 coi-responding to C 67-14, H 2*8. 

 Ci^H^O^ requires C 67-10, H. 2-8. 



iJichromone crystallises in long straw-coloured silky needles. It is 

 scarcely soluble in ether, light petroleum, or ligroin ; sparingly soluble in 

 benzene, xylene, carbon disulphide, or cold alcohol ; and readily soluble in 

 hot alcohol, chloroform, or acetone. It is insoluble in cold aqueous alkali, but 

 is decomposed by hot alkali. Its solution in concentrated sulphuric acid has 

 a' faint yellow coloiu-, and an intense emerald-green fluorescence. This 

 fluorescence is much impaired by the presence of even a small amount of 



