330 PROCEEDINGS OP THE AMERICAN ACADEMY 



(3 Chlorpyromucic Acid. 



Hill and Sanger* found no difficulty in preparing ft brompyro- 

 mucic acid by the reduction of either of the two dibrornpyroniucic 

 acids described by them. The corresponding dichlorpyromucic acida 

 we found to be much more refractory, and we succeeded in preparing 

 the j3 chlorpyromucic acid only after many unsuccessful attempts. 

 The fSy dicblorpyromucic acid, which was the more accessible, proved 

 to be the more difficult of reduction, so that almost the whole of the 

 material for this investigation was made from the y8S dichlorpyromucic 

 acid. When zinc dust is added to a cold ammoniacal solution of this 

 acid, no perceptible reaction takes place, and even after long standing 

 no essential change can be detected. Even when the ammoniacal 

 solution is boiled with a large excess of zinc dust the reduction is but 

 slowly effected, and long continued heating is necessary to complete 

 the reaction. We have fouud it advantageous to dissolve the acid in 

 about twenty times its weight of dilute amnionic hydrate, to add an 

 equal weight of zinc dust, and to boil for eight or ten hours, taking 

 care to keep the solution strongly ammoniacal. The filtered solution 

 is then cooled and acidified with dilute sulphuric acid, the acid which 

 separates removed by filtration, the filtrate extracted with ether, and 

 the residue left upon the evaporation of the ether added to the main 

 product. The crude acid thus obtained melted at about 130°, and 

 evidently contained unaltered /38 dicblorpyromucic acid. We there- 

 fore dissolved it in dilute amnionic hydrate, and added to the ammoni- 

 acal solution calcic chloride as long as a sparingly soluble calcium salt 

 was promptly precipitated. The filtered solution then gave, when 

 acidified with hydrochloric acid, a crystalline acid, which after recrys- 

 tallization from hot water melted at 145-146°, and proved upon 

 analysis to be a chlorpyromucic acid. From the sparingly soluble 

 calcium salt, which had been removed by filtration, we obtained only 

 unaltered fi& dichlorpyromucic acid, which in its turn was treated with 

 zinc dust. In this way we found it possible to obtain from the /?S di- 

 chlorpyromucic acid at least 80 per cent of the theoretical amount of 

 pure /3 chlorpyromucic acid. Zinc dust, even after long boiling, seems 

 to have but little action upon /3y dichlorpyromucic acid in ammoniacal 

 solution, but sodium amalgam slowly reduces it at 100°. In order to 

 effect complete reduction, it proved to be necessary to use a large ex- 

 cess of sodium in the form of a one per cent amalgam, and the reaction 

 was then completed after heating for three hours on the water bath. 



* These Proceedings, xxi. 147. 



