524 Prof. B, Meldola on the Theory of the 



true representatives of Kekule's type. In answer to this I 

 may point out that, as far as the experimental evidence at 

 present goes, the normal compounds and the analogous ethyl- 

 derivatives may be written on Kekule's type: — 



(p) N0 2 . C 6 H 4 . N 2 JNH . C 6 H 4 . N0 2 (p), 



m.p. 223°. 



(m) N0 2 . C 6 H 4 . N 2 JNH . C 6 H 4 . N0 2 (m), 

 m.p. 194°. 



(p) N0 2 . C 6 H 4 . N 2 JN(C 2 H 5 ) . C 6 H 4 . NO, (p), 



m.p. 191°-192°. 



(m) N0 2 . C 6 H 4 . N 2 JN(C 2 H 5 ) . C 6 H 4 . N0 2 (m), 

 m.p. 119°. 



(p) N0 2 . C 6 H 4 . N 2 .|N(C 2 H 5 j . C 6 H 4 . N0 2 (m), 



m.p. 187°. 



(m)N0 2 .C 6 H 4 .N 2 . 



N(C 2 H 5 ).C 6 H 4 .N0 2 ( P ). 



m.p. 174°-175°. 



The modes of decomposition of these compounds are ex- 

 plained by the above formulae by supposing the planes of 

 separation to be along the dotted lines ; and it further appears 

 that the isomerism of the three ethyl-derivatives of m.p's 148°, 

 114?-llb\ and 187° (Nos. 4, 7 and 8 in the table) may be 

 explained by the different formulas ascribed to these com- 

 pounds respectively. 



But although Kekule's formula may pass muster for the 

 normal compounds, we are not necessarily reduced to this as 

 a final expression ; and I am strongly inclined to the belief 

 that it will have to be abandoned also in the case of these 

 compounds. In the first place, as there is a great resemblance 

 in character between the normal and the mixed compounds, 

 analogy leads me to suppose that their constitutions are not 

 so widely different, as appears from the two modes of formu- 

 lation : — 



/N:N 

 X^ \Y and X.N 2 .NH.Y. 



H 



