296 PROCEEDINGS OP THE AMERICAN ACADEMY 



other papers from this laboratory, as in them the yield rose but little 

 above 50 per cent of the theory. 



The amount of bromine separated as bromide of sodium in the prep- 

 aration of the substance was determined in two cases as follows : — 



I. 5 grs. of tetrabromdinitrobenzol yielded 3.707 grs. of argentic 



bromide, corresponding to 1.578 grs. of bromine. 

 II. 5 grs. of tetrabromdinitrobenzol yielded 3.G31 grs. of argentic 

 bromide, corresponding to 1.545 grs. of bromiue. 



The theoretical yield, if two of the atoms of bromine had been re- 

 moved, would be 1.653 grs. 



Percentage of bromiue found as bromide of sodium, — 



I. ii. 



95.43 93.48 



From these numbers it appears that essentially all the bromine is 

 removed as sodic bromide. 



The oil which formed the secondary product of the reaction was 

 not investigated further, as from the composition of the ester, and the 

 fact that all the bromine appeared as sodic bromide, there could be no 

 question that the nature of this action is the same as that with the tri- 

 brom compounds ; and in those cases* the study of the oils has show a 

 conclusively the mode of formation of the substances. There can be 

 no doubt, therefore, that the reactions which take place in this case 

 should be written as follows : — 



C 6 Br 4 (N0 2 ) 2 + 2 CHNa(COOC 2 H 5 ) 2 = 



NaBr+ C 6 Br 3 (N0 2 ) 2 CH(COOC 2 H 5 ),-f CHNa(COOC 2 H.) 2 = 

 C 6 Br 3 (N0 2 ) 2 CNa(c60C 2 H 5 ) 2 + CH 2 (COOC 2 H 5 ) 2 = 

 C 6 HBr 2 (N0 2 ) 2 CNa(COOC 2 H 5 ) 2 + CHBr(COOC,H 5 ) 2 . 



The brommalonic ester being converted afterward into tartronic or 

 acetylentetracarbonic ester. 



Properties. — The dibromdinitrophenylmalonic ester crystallizes 

 from alcohol usually in slightly yellow to colorless needles, which unite 

 into groups like pompons if the solution is dilute; seen under the mi- 

 croscope they consist of rather long rhombic plates with a decidedly 

 acute angle, about six times as long as their breadth, or even slen- 

 derer, either free or in radiating groups, the crystals branching so 

 as to give the effect of being arranged in curved lines. When less 

 well developed, the groups are made up of fine needles very much 



* These Proceedings, xxiv. 238, 265. 



