OF ARTS AND SCIENCES. 155 



Action of Alcoholic Sodic Hydrate upon Pyromucic 

 Tetrabromide. 



By acting upon pyromucic tetrabromide with an alcoholic solution 

 of potassic hydrate, Toennies obtained a dibrompyromucic acid melt- 

 ing at 186°. In the preliminary paper already referred to,* he gives 

 no description of the conditions under which the decomposition was 

 effected, and, as far as we are aware, he has never published any more 

 extended account of his work. 



The pyromucic tetrabromide we prepared according to his directions 

 by exposing pyromucic acid to the vapors of bromine. The bromine 

 was quite rapidly absorbed, and the acid was converted into a volumi- 

 nous porous mass from which the excess of bromine could readily be 

 expelled by a short exposure to the air. The formation of this addi- 

 tion product, however, was not the only reaction which took place, since 

 hydrobromic acid was invariably evolved in no insignificant quantities, 

 and the product therefore contained also 8-monobrompyromucic acid 

 and its tetrabromide. For the purification of the pyromucic tetrabro- 

 mide we have found glacial acetic acid (99.5 per cent) more advan- 

 tageous than the mixture of ligroin and ether recommended by 

 Toennies. 



Since the purification of large quantities of the tetrabromide was at 

 best a matter of difficulty, we have used in our work the crude product* 

 more especially since the isolation of the products formed from it 

 presented no greater difficulties. Instead of using an alcoholic solu- 

 tion of potassic hydrate for its decomposition, we have taken sodic 

 hydrate, since the sodium salts of the acids formed seemed to be some- 

 what less soluble in alcohol than the potassium salts. We have found 

 that the best results may be obtained by using a decided excess of a 

 concentrated solution of the alkaline hydrate, taking care tiiat the 

 temperature does not rise above 25°. The greater part of the sodium 

 salts formed separates at once, and may be filtered off upon the pump. 

 The sodium salt dissolved in water and acidified with hydrochloric acid 

 yields an acid, usually more or less colored, wliich is readily soluble 

 in cold water, more readily in hot, and whose melting-point is quite 

 constant (l."36-138°). This consists essentially of a mixture of two 

 isomeric dibrompyromucic acids, although it frequently contains small 

 quantities of 8-monobromi)yroinncic and tribrom|)yromucic acids. The 

 aqueous solution filtered from these acids contains also oxalic acid. 



* Bericlite der deutsclicn cliem. Gescllsch., xi. 1086. 



