OP ARTS AND SCIENCES. 169 



broraacetylen and muconic acid when heated with baric hydrate. The 

 reaction with argentic oxide they wrote: — 



2 C,H,Br,03 + 2 Ag.fi = C,H,Br3Ag30, + AgBr + 11,0 + CO,. 



In the course of the investigations upon mucic acid and its deriva- 

 tives, which were begun in Limpricht's* laboratory in 1868, muco- 

 bromic acid received more or less attention. Although it was found 

 to be the only product when pyromucic acid was treated with wafer 

 and an excess of bromine at ordinary pressures, Limpricht and Del- 

 briick showed that it was completely decomposed when heated in a 

 sealed tube to 120° with bromine and water, provided that three mole- 

 cules of bromine, at least, were used to one of mucobromic acid. As 

 products of the decomposition, they found, beside carbonic dioxide and 

 hydrobromic acid, tribromethylenbromide, CgHBr^, perbromatbylen- 

 bromide, C^Brg, tetrabrombutyric (?) acid, C^H^Br^O,, and dibrom- 

 fumaric (?) acid, C Ji^^r fi^. The marks of interrogation appear in 

 Limpricht's original paper. Limpricht and Lessing also found in one 

 experiment that, by the reduction of mucobromic acid, a liquid was 

 formed which boiled at about 120° and contained 84.8 per cent of 

 carbon, 8.8 of hydrogen, and the remaining 6.4 per cent was oxygen. 

 They were, however, unable to repeat the experiment with a like 

 result. 



In attempting the preparation of mucobromic acid, Mr. 0. R. Jack- 

 son and I found that we were unable to obtain a satisfactory yield by 

 following the method given by Schmelz and Beilstein or by Lim- 

 pricht. Schmelz and Beilstein say that the quantity of water taken 

 is not a matter of indiiference, but neither they nor Limpricht make 

 any specific statements as to the amount which they found to be most 

 advantageous. They agree, however, that the bromine should be 

 added slowly as long as it is taken up in the cold, that the solution 

 should then be heated and bromine added as long as the color con- 

 tinues to disappear. 



According to this method, we were unable to get more than 25 per 

 cent of the theoretical yield; and at the same time we were obliged to 

 use quite a large excess over the amount of bromine calculated from 

 the equation : — 



C,H,03 + 4 Br, -f 2 H,0 = C,B,Brfi, + CO, + 6 HBr. 



* Berichte d. deutsch. chem. Gesellsch., ii. 211; iii. 90, 671; iv. 805; Zeitschr. 

 fur Chem., 1869, 599; Ann. Chem. u. Pharm., clxv. 253. 



