6 PROCEEDINGS OF THE AMERICAN ACADEMY 



Other specimens contained the following percentages : — 



Bromine 54.87 58.51 58.57 



To confirm this result, which points to the taking up of four atoms 

 of bromine, we determined the increase of weight caused by the 

 bromine. For this purpose carbonic disulphide and bromine in excess 

 were added to a weighed amount of curcumin, and the product weighed 

 after drying it a little below 100°. 



I. 0.252 g. of curcumin gained 0.354 g. 

 II. 0.218 g. gained 0.300 g. 



These results correspond to the following percentages of bromine in 

 the product, — 



Calculated for Ci^UuBr^O^. Found. 



I. n. 



Bromine 56.66 58.41 57.91 



And there is therefore no doubt that the substance contains four atoms 

 of bromine. To decide whether it was an addition or substitution 

 product, we determined the amount of hydrobromic acid given off, 

 as in every preparation an evolution of this gas was observed. For 

 this purpose the gases formed in the reaction were allowed to pass 

 through water, and finally the carbonic disulphide and excess of 

 bromine were removed, at first from the curcumin, and afterward 

 from the absorbing water, by a sti'eam of air ; the hydrobromic acid 

 collected in the water was then determined as argentic bromide. One 

 gramme of curcumin was used in each case, and in the following com- 

 parison of results the amounts found are compared with the calculated 

 amount if the curcumin had given off two molecules of hydrobromic 

 acid, — 



Two Molecules HBr. I. II. 



0.66 0.185 0.28 



From this it appears that the hydrobromic acid is produced by an 

 insignificant secondary reaction, and that the substance is an addition 

 product, and therefore has the formula Cj^Hj^Br^O^.* We may add 

 that some experiments to determine directly the number of molecules 

 of bromine added pointed to two molecules as the probable amount, but 

 the results are not definite enough to make them worth publishing. 



Properties. It is a white or whitish amorphous substance, melting 

 in the neighborhood of 185° with decomposition, but it has no definite 



*The high percentages of bromine obtained in the analyses may be ac- 

 counted for by this secondary reaction. 



