OP ARTS AND SCIENCES. 335 



The reaction was then precisely analogous to that by means of 

 which mucobromic acid was formed from (3 brompyromucic acid : 



C 5 HX10 3 + 3 Br 2 + 2 H 2 = C 4 H 2 BrC10 3 + Co 2 + 5 HBr. 



With the material which for the moment was at our disposal, we were 

 unable to study the decomposition of the mucochlorbromic acid by 

 alkalies. We shall hope in the future to prepare in this way a chlor- 

 bromacrylic acid, and compare it with the acid of the same composi- 

 tion already described by Mabery and Loyd.* 



(3y DlCHLORPYROMUCIC ACID. 



Hill and Sanger f had shown that in the decomposition of pyromu- 

 cic tetrabromide or of ethyl pyromucic tetrabromide by alcoholic sodic 

 hydrate, two isomeric dibrompyromucic acids are formed in not widely 

 unequal quantities. There was, therefore, every reason to expect that 

 two isomeric dichlorpyromucic acids could be found in the product 

 formed in a similar way from ethyl pyromucic tetrachloride. Since 

 we had found that a low temperature was essential to the preparation 

 of a pure product, we allowed the ethyl pyromucate to absorb chlorine 

 at 0° until a constant weight was reached, expelled the excess of chlo- 

 rine by a current of dry air, and decomposed the product at once with 

 an excess of an alcoholic solution of sodic hydrate. The best results 

 were obtained when the tetrachloride was slowly added to a concen- 

 trated sodic hydrate solution, taking care to keep the mixture cold. 



The sodium salts formed are sparingly soluble in alcohol, and after 

 a short time can be removed by filtration. The alcoholic solution was 

 freed from the excess of sodic hydrate by means of carbonic dioxide, 

 and, after removing the sodic carbonate by filtration, distilled. The 

 sodium salts left on distillation appeared to be identical with those 

 already obtained and were therefore added to the main portion. The 

 alcoholic distillate grew turbid when mixed with water, and gradually 

 deposited a small quantity of a colorless oil which had a peculiar aro- 

 matic odor. The quantity of this oil was so small that no investiga- 

 tion of it has as yet been made. 



The sodium salt which was obtained from the tetrachloride was 

 dried, dissolved in hot water, and acidified with hydrochloric acid. 

 In this way an acid was obtained which crystallized in finely felted 

 needles which usually melted at 155°. After two recrystallizations 

 from benzol the acid melted at 108-169°, and further recrystalliza- 



* These Proceedings, xvi. 238. 

 t These Proceedings, xxi. 150. 



