14 PROCEEDINGS OF THE AMERICAN ACADEMY. 



dioxide, when heated to 130° with diluted sulphuric acid (sp. gr. 1.43), 

 or when boiled with concentrated hydrobrornic acid. The reaction 

 seemed to be more neatly effected with the latter reagent, and we 

 therefore heated tribrompyromucic acid with from four to five times 

 its weight of concentrated hydrobrornic acid with a return condenser. 

 When no further escape of carbonic dioxide could be detected, the 

 somewhat dark colored clear solution was cooled, and diluted with 

 water. A heavy crystalline precipitate was thus thrown down, which 

 could easily be purified by recrystallization from alcohol or ligroin. 

 The crude product obtained in this way amounted to about half the 

 weight of the tribrompyromucic acid taken. Analyses of the body 

 after several recrystallizations from alcohol showed that it had the 

 formula C4H 2 Br 2 0. 2 . For the analyses of this dibromcrotonolactone, 

 and of several of its derivatives, which we publish, we are indebted 

 to Mr. H. N. Herman, who made a preliminary study of this body 

 seme two years ago, but was unable to continue the investigation. 



I. 0.2472 grm. substance gave 0.1788 grm. C0 2 and 0.0209 grm. H 2 0. 

 II. 0.2394 grm. substance gave 0.3711 grm. AgBr. 



i. 



ii. 



65.96 



This same body may also be made directly from mucobromic acid 

 by the action of phosphorous iodide. Phosphorus is dissolved in five 

 times its weight of carbonic disulphide, equivalent weights of iodine 

 and mucobromic acid well ground together are then added, and the 

 nearly solid mass heated on the water bath with reverse cooler. The 

 reaction sets in slowly, and frequently only after a part of the car- 

 bonic disulphide has been allowed to escape through the cooler. 

 With no solvent present the reaction is violent and yields little or no 

 product. When the mass is completely liquefied, the rest of the car- 

 bonic disulphide is distilled off, the flask well cooled, and cold water 

 added in not too small quantity. On shaking, the crude lactone sepa- 

 rates in a granular condition. In this way it is easy to obtain a 

 product which amounts to two thirds of the weight of the mucobromic 

 acid taken, but it contains a decided percentage of iodine, and the 

 preparation of pure dibromcrotonolactone from it is a matter of great 

 difficulty. By fractional crystallization from various solvents we 

 found it impossible to eliminate the iodine, but on distillation with 



