72 PROCEEDINGS OF THE AMERICAN ACADEMY 



of tribromdiuitrol)enzol, that is, 36 to 45 per cent of the theoretical, 

 if both the nitric and fuming sulphuric acids were of the best quality. 

 To prove that this violent boiling was the cause of the large yields, in 

 one experiment the mixture was allowed to stand in the cold for a 

 week, and then kept barely at the boiling point for seven hours, when 

 it yielded only 18 per cent of the tribromtriuitrobenzol. 



The Nitrite of Brointrinitrophenylmalonic J^sle?', 

 C6HBr(N02)3CN02(COOC2H5)2. 



This substance was prepared as follows : — 3 gr. of bromtrinitro- 

 phenyhnalouic ester* were mixed with about 10 gr. of nitric acid, 

 specific gravity 1.38, and warmed in a dish for three minutes on the 

 water bath, when both the undissolved organic substance and the 

 acid became intense blood-red ; the mixture was then allowed to cool, 

 the acid liquid poured off, and the solid residue warmed once more for 

 two minutes with about the same volume of fresh acid. After this, 

 the acid was decanted off, and the solid crystalline product washed 

 with water till free from nitric acid, which changed it from a deep 

 blood-red to a pale reddish-white color. The puritication of this sub- 

 stance gave us much trouble at first on account of its slight stability, 

 since even the short warming necessary to dissolve it in alcohol was 

 sufficient to decom])ose it partially, while longer heating wTth alcohol 

 produced complete decomposition ; but at last we obtained satisfactory 

 results from the following method. The crude substance, after the 

 thorough washing with water mentioned above, was dissolved in warm 

 chloroform, in which it is freely soluble, but even with this solvent 

 care must be taken to warm the mixture for as short a time as pos- 

 sible ; it was advisable, therefore, to achieve the solution rather by the 

 use of a larger qu ;ntity of eliloroform than by using a smaller volume 

 at a higher temperature. This chloroform solution was then diluted 

 with about its own volume of common alcohol, when the substance 

 graduRlly separted in well formed white prisms, and was obtained 

 pure after two of these crystallizations. It must be dritd in vacuo, 

 as it decomposes on the water bath ; in fact, even the temperature of 

 a steam radiator (about 70°) was sufiicient to bring about a partial 

 decomposition. 



A small additional amount of this substance could be obtained from 

 the rei! nitric acid mother lifjuors formed in its preparation, either by 

 adding water or by evaporating them to dryness ; but tliis (luantity is 



* Mellingut 104°. These Proceedings, XXIV. 258. 



