274 PROCEEDINGS OP THE AMERICAN ACADEMY 



To convert the tribrombenzol into the dinitro compound, 25 grs. of 

 it were added to 100-120 grs. of nitric acid* of specific gravity 1.52, 

 (made from potassic nitrate and sulphuric acid in the laboratory.) 

 warmed gently until the solid had dissolved, and allowed to stand 

 about two hours, when tbe tribromdinitrobenzol crystallized out in 

 large white prisms. The yield was essentially quantitative. 



Bromdinitroph enylacetacetic Ester, 

 C 6 H 2 Br(N0 2 ) 2 CH 3 COCHCOOC. 2 H s . 



Preparation. — This substance was made by the action of an alco- 

 holic solution of sodium acetacetic ester on a benzol solution of the 

 tribromdinitrobenzol in the proportion of about four molecules of the 

 former to one of the latter. For this purpose 15 grs. of tribromdini- 

 trobenzol were dissolved in about 200 c.c. of benzol, and mixed with 

 20 grs. of acetacetic ester previously treated with 3 grs. of sodium 

 dissolved in about 20 c.c. of absolute alcohol. At first there was very 

 little change of color, but on standing at ordinary temperatures the 

 liquid turned first yellow and then red (whereas with malonic ester 

 the red color appeared instantaneously). In order to complete the 

 reaction, the mixture was heated on the steam bath for about one 

 hour, at the end of which time it had become nearly black, and a con- 

 siderable precipitate of sodic bromide had formed. It was then mixed 

 with from one and a half to two litres of water, and the reddish benzol 

 solution, which was precipitated, removed from the dark red aqueous 

 liquid ; the latter was then acidified with dilute sulphuric acid,- taking 

 care to avoid a large excess ; this decomposed the red sodium salt of 

 the new substance, which was set free in the form of a yellowish oil, 

 and extracted by shaking the liquid with ether twice. On distilling 

 off the ether a dark reddish brown oil was left, which, when cold, was 

 treated with very little alcohol, and upon stirring became filled with 

 crystals, the quantity of which increased on standing for twelve or 

 more hours. When the quantity of the crystals did not increase 

 further, the pasty mass was sucked out on the pump, first adding a 

 little alcohol, if necessary, and by washing with a small quantity of 

 cold alcohol all the very soluble red oil was removed from the crys- 

 tals, which were nearly or quite insoluble in cold alcohol, and were 

 next purified by crystallization from hot alcohol until they showed the 

 constant melting point 96°. An additional quantity of the substance 

 can be obtained from the benzol solution by distilling off the benzol 



* These Proceedings, xxii. 374. 



