OP ARTS AND SCIENCES. 361 



bromine to 8 chlorpyromucic acid and of chlorine to ethyl 8 broniijyro- 

 mucate. Although we readily prepared in this way trisubstituted 

 acids, the products in neither case were homogeneous, tribrom- or 

 trichlorpyromucic acids being formed together with the acid containing 

 both halogens. 



;Sy-DlCHLOR-8-NlTROPTROMUCIC AciD. 



Hill and Palmer* have shown that f3y dibrompyromucic acid is 

 easily converted into a sulphouic acid by means of sulphuric acid, and 

 that the sulpho group in this acid may readily be replaced by the nitro 

 group. /3y dichlorpyromucic acid was dissolved in fuming sulphuric 

 acid, and the barium salt of the sulphonic acid isolated in the usual 

 way. Since a more complete study of the salt did not fall within the 

 plan of our work, we precipitated the barium exactly with sulphuric 

 acid, and evaporated the dilute solution of the acid first at 100° and 

 afterwards in vacuo over sulphuric acid. The crystalline somewhat 

 deliquescent acid thus obtained was dissolved in several times its 

 weiirht of fuming: nitric acid, to which half its volume of concentrated 

 sulphuric acid had been added. After the action was finished, the 

 nitric acid was partially expelled, the residue diluted with water, and 

 extracted with ether. The ether was then shaken with a dilute solu- 

 tion of sodic carbonate, and the acid precipitated from this alkaline 

 solution by the addition of hydrochloric acid. The ethereal solution 

 proved to contain no substance which invited further investigation. 



The ^y-dichlor-S-nitropyromucic acid is readily soluble in alcohol, 

 ether, or hot benzol. Hot water dissolves it freely, and on cooling the 

 greater part of the acid is deposited in flattened leafy prisms which 

 melt at 189-190°. 



0.2168 grra. substance dried over HgSO^ gave 0.2756 grm. Ag. CI. 



Calculated for 

 CjHCUNOs. , Found. 



CI 3L42 31.42 



TVe have as yet made no further study of this acid. 



Theoretical Considerations. 



The acids melting at 168-169° and 155-156°, which in the pre- 

 ceding pages we have called the /3y and /3S dichlorpyromucic acids, are 

 without doubt identical in structure with the two dibrompyromucic 

 acids described by Hill and Sanger. f Their physical properties and 



* These Proceedings, xxiii. 201, 205. 

 t These Proceedings, xxi. 137. 



