JACKSON AND PHINNEY. — PICRYLMALONIC ESTER. 107 



ing at 143° and 122°) discovered by W. B. Bentley * and one of us. It 

 seems more doubtful whether it is related to the isomerism of the formyl- 

 phenylacetic esters discovered by W. Wislicenus,t of the dibenzoylace- 

 tones t and the benzoates of oxymethylenacetone § of Claisen, and the 

 benzalanilinacetacetic esters of R. Schiff,1[ since both of our isomeres can 

 be dissolved in alkaline solutions without alteration, whereas one of the 

 most marked differences between the isomeres in these other cases con- 

 sists in the fact that one dissolves in alkalies and the other does not. 



Our present knowledge of these substances is not sufficient to allow us 

 to make a final statement in regard to the cause of this isomerism, but 

 the following discussion may be given for what it is worth. The fact 

 that each form has been converted into a salt, and set free from this un- 

 altered upon acidification, would indicate that it is a case of chemical 

 rather than physical isomerism ; and, if this is true, as the symmetrical 

 nature of the substance would forbid stereometric isomeres, the only 

 probable explanation which we have been able to find is that the isom- 

 erism depends on differences of structure in the malonic group, as indi- 

 cated by the following formulas : — 



I. CeH2(N02)3CH(COOCoH5)2. 



n. c.h,(no,).c1^Xoc:h.. 



In other words, that the isomerism is analogous to that of the bodies 

 studied by W. Wislicenus, Claisen, and R. SchifF. There are, however, 

 objections to this explanation, and, as we have said already, the whole 

 subject needs further investigation before any theory can be found 

 satisfactory. 



Properties of the Trinitrophenylmahmc Ester melting at 64°. — Crys- 

 tallized from alchohol, it forms white plates, usually bounded by four or 

 six sides. In the four-sided form there are two unlike opposite angles, 

 one obtuse the other acute, which give a very characteristic appearance 

 to the crystals. The six-sided form is produced by two planes trun- 

 cating the similar angles in the four-sided form. Both these forms 

 resemble a kite in shape. Occasionally much more complex crystals 

 w^ere observed, having a parallel-sided projection arising from the middle 

 of the obtuse end, and also terminated by an obtuse angle ; this form had 

 a general resemblance to the "spade" in playing cards. The plates 



* These Proceedings, XXVI. 82. § Ber. d. chem. Ges., XXV. 1785. 



t Bar. d. chem. Ges., 1895, p. 767. T Bar. d. cliem. Ges., XXXI. 601. 



% Ann. Chem., CCLXXVII. 188. 



