OP ARTS AND SCIENCES. 201 



by Wolff as 125-125°.5, although he adds in a more recent paper * 

 that impurities otherwise imperceptible may depress the melting 

 point from two to three degrees. In order to compare the two 

 acids, we have ourselves made the acetacrylic acid of Wolff from 

 /3-bromlaevulinic acid. In the preparation of the /3-bromlaevulinic 

 acid we followed with precision the directions of Wolff. The com- 

 plete purification of the crude acid was in our hands attended with 

 great loss of time and material, and, even after repeated recrystalli- 

 zation from carbonic disulphide, we failed to raise the melting 

 point above 58°, while Wolff gives 59° as the melting point of the 

 pure acid. Under these circumstances, we did not attempt to pre- 

 pare pure /3-bromlaevulinic acid in larger quantity, but decomposed 

 with sodic acetate in an acetic acid solution a preparation which 

 melted at 55-56°. The acetacrylic acid which we thus obtained 

 was to all appearance identical with that made from methylpyro- 

 mucic acid. As was to be expected, its melting point was some- 

 what low, 121-123°, but after several recrystallizations from benzol 

 melted at 123-124°. Wolff f describes the silver salt of his acid 

 as stellate needles, while the silver salt of our acid crystallized 

 in well formed six-sided plates. We convinced ourselves that the 

 same six-sided plates were formed by the addition of argentic 

 nitrate to a moderately concentrated solution of both acids, and 

 that on recrystallization these plates frequently formed dendritic 

 aggregations. These dendritic forms only were seen if an insuf- 

 ficiently purified acid was used. While it is very possible that the 

 acids which we had in our hands were in neither case absolutely 

 pure, we cannot doubt the identity of the material from the two 

 sources. 



In order to identify still further our product with Wolff 's acet- 

 acrylic acid, we dissolved it in chloroform and added at low tem- 

 perature one molecule of bromine. The color of the bromine was 

 discharged, and on evaporation a crystalline residue was obtained 

 which melted after recrystallization from a mixture of benzol and 

 carbonic disulphide at 107-108°. According to Wolff f the a/3-di- 

 bromlaevulinic acid melts at this point. With phenylhydrazine 

 our product also readily gave the corresponding hydrazone, identical 

 in every respect with the body described by Bender % and shortly 



* Ann. Chem. u. Pharm., CCLXIV. 245. 



t Ibid., p. 248. 



t Berichte der deutsch. chem. Gesellsch., XXI. 2494. 



