OP ARTS AND SCIENCES. 863 



pyroinucic acid could be formed by tbe action of heat upon pyromucic 

 tetrabrornide, when bromine must be eliminated as well as hydrobromic 

 acid. Since we had noticed that hydrochloric acid invariably was 

 evolved in the preparation of ethyl pyromucic tetrachloride, it seemed 

 to us not improbable that the ^ dichlorpyromucic acid was in fact the 

 yd acid which had been formed in a similar way from the tetrachloride 

 of the 8 chlorpyromucic ether necessarily contained in the crude 

 product. 



CI CI 



We found, however, that no x dichlorpyromucic acid was formed 

 on heating ethyl 8 chlorpyromucic tetrachloride, and that our product 

 in this case contained the /?8 acid alone, so that the molecule of 

 chlorine, which had been eliminated in the reaction, had taken its 

 chlorine atoms from the y and 8 positions. We hoped also to get 

 further evidence as to the structure of the ^ dichlorpyromucic acid by 

 reducing it to a chlorpyromucic acid, or by substituting the chlorine of 

 the x dichlorsulphopyromucic acid by hydrogen; but in neither case 

 have we yet succeeded in obtaining well characterized products. 



While it seems to us probable that the % dichlor pyromucic acid is 

 geometrically isomeric with the /38 acid, we have as yet been unable 

 to convert one acid into the other. Both acids volatilize unchanged 

 when heated, and the ordinary reagents which usually effect conver- 

 sion in such cases have failed to bring abont any perceptible isomeri- 

 zation. While lack of material has to a great degree limited our work 

 with the x acid, we have studied the behavior of the fi8 acid under a 

 variety of conditions with purely negative results. If tlie two acids 

 are in fact geometrically isomeric, the simultaneous appearance of both 

 forms in the distillation of ethyl pyromucic tetrachloride with the 

 escape of large quantities of hydrochloric acid shows that the conver- 

 sion of one acid into the other is effected with difficulty, while the 

 formation of the (3d acid alone from the ethyl 8 chlorpyromucic tetra- 

 chloride under similar conditions is especially worthy of note. Since 

 pyromucic acid apparently contained two pairs of carbon atoms doubly 



