OP ARTS AND SCIENCES. 219 



H — C = C — H 



I I 

 II — C = C — H 



just as the various compounds of the aromatic series were derived 

 from benzol. As the formula which naturally suggested itself for 

 mucobromic acid he gives, — 



HOC = COHO 



1 I 

 BrC = CBr 



although I am at a loss to know precisely how this formula is to be 

 interpreted. This hypothesis received temporary support from the 

 discovery of the so-called tetraphenol by Limpricht and Rohde ; * but 

 further experiments made in Limpricht's laboratory failed to sustain 

 it, and in the subsequent detailed account of these investigations t no 

 allusion is made to it. In this paper Limpricht described the forma- 

 tion of fumaric acid by the action of bromine and water upon pyro- 

 mucic acid, as well as the substance C^H^Og, which he called fumaric 

 acid aldehyde, and regarded as the product from which mucobromic 

 acid was derived by substitution. In 1877 Baeyerf showed that this 

 latter substance was in fact the half-aldehyde of fumaric acid, in that 

 it could be converted into fumaric acid by the action of argentic 

 oxide. At the same time he pointed out the difficulty of supposing 

 that mucobromic acid, which empirically was a substitution-product 

 from this aldehyde, could be formed from it by the direct action of 

 bromine. 



In 1878, Wallach and Bischo£P§ published a paper upon the action of 

 alkalies upon the /3 dichloracrylic acid, which Wallach 1[ had previously 

 made by the reduction of chloralid. In a subsequent paper || upon 

 the same subject, they assumed that the structure of the dibromacrylic 

 acid from mucobromic, which 0. R. Jackson and I ** had shortly be- 

 fore described in a preliminary notice, was established quite surely by 

 its ready conversion into malonic acid, and Wallach was therefore led 

 to append a note containing a suggestion which he had previously 



* Berichte der deutsch. chem. Gesellsch., iii. 90. 

 t Ann. Cliem. u. Pliarm., clxv. 278. 

 } Rerichte der deutsch. chem. Gesellsch., x. 1362. 

 § Ibid., xi. 751. 

 T Ihid., viii. 1580. 

 II Il)id., xii. 57. 

 ** Ibid., xi. 1671. 



