( 473 ) 



According to my research there is here no question of an isomor- 

 phism with an appearing hiatus. 



All this is quite in accord witli the deviating crystalline form of 

 Hydrazohenzene. 



It deserves attention that Billows') has investigated p-Azotoluene 

 and p-Hydrazotoluene. He finds : 



'p-Azotoluem> (143"^ C.)-Monoclino-prismatic 



n:h:c = 0,5687 : 1 : 1,7105 ; |3 = 89°.44'. 



p-Hydrazotoluene (128° C.)-Monoclino-prismatic 



a:h:c = 0,6279 : 1 : 2,0287 ; ^ = 89*^.49'. 



Notwithstanding these deviations, also that one where jOOlj of the 

 first substance plays the role of |100| at the second he declares 

 these compounds to be "isomorphons" 1 Of more than a mere morpho- 

 tropic relation there can be no question here, and the so called 

 isomorphogenous replacement of — N=N — by — NH — NH — does 

 not help us here. 



As Dihenzyl and Benzijl aniline can yield mixed crystals and as 

 according to Bruni the latter yields mixed crystals with Azohenzene 

 an analogy in form is to be suspected liere. This may indeed be 

 brought to light by assigning to Boekis' forms in Azohenzene: |100|, 

 |001J. jllOj, |201|, |403| respectively the symbols : |100|, |TOI|, |410|, 

 jlOlj, |103|, that is to say by calling the form which should be 

 \ïm\ with BoERis, jOOlj. 



Then we ha\'e : 



Azohenzene -. a -. h -. r = 2,1076 : 1 : 1,4220 ; /? = 76\32' 

 Benzyhmiline: a -. h : r = 2,1076 : 1 : 1,6422 ; /? = 76°.36V. 



Therefore, a relation which, having the mme ratio a -. h and an 

 equal angle ,:?, looks as if it ought to be considered as a case of 

 isomorphotropism bordering on isomorphism. 



It must, however, be pointed out immediately that this explanation 

 is not a raUonal one as the other forms of Azohenzene observed bv 

 BoERis obtain in this way very complicated symbols. 



It must also be observed that the meltingpoint of Benzylaniline 

 (364° C.) is lowered by addition of small quantities of Azohenzene. 



Whilst the BenzylanUine used melted at 36^° C. and the ylcoèmcr^??^ 

 at 68^ C, the following melting points t were found for mixtures : 



I) Billows, Rivi^ta di Minei-al. e Ciistall. ital. (1903). 30. 34—48. Abstract 

 Z. f. Kryst. 41. ±Ti. 



