298 



mean value of the coefficient ^— at temperatures ot^/o»' the transition- 



dt 



point of the anisotropous liquid will appear to be smaller than that 



of the isotropous liquid above the transformationpoint. The following 



measurements were made to verify this conclusion by means of 



experiments. 



§ 2. The substances investigated here are in the first place the 

 following compounds often studied already, which have been purified 

 iiere wiili the utmost care : 



Ijara-Azoxy-Anisol : CH, 0. C,H,.:N, 0. C\ H,.OCH, ; 



t, = lire, and t, = 138° C. 



para-Azoxy-Phenetoh C,R, 0. C\ H,.N, 0. C\H,.OC,H, ; 



^ = 138°Cand<, = J68°C. 



and 



para-Anlsaldazme : CH,O.C,H,.CH:X.N:CH.L\HJ)CH, ; 

 ^=169°Cand<, = 180°C. 

 The last meulioned substance was prepared from p-anisaldehyde 

 and hydrazine-sulphate; it was purified by repeated crystallisation 

 from boiling benzene. 



Furthermore we choose: Ethyl-para- Azoxyhenzoate : C^HJJ.CO.C^ 

 HyN ^O.C^H^.CO.OC^H^, which was purified by recrystallisation 

 fi'om a mixture of chloroform and benzene. The beautifully crys- 

 tallized compound shows the transition-temperatures: <; ^ 114° C. 

 and /, =:12l°C. Finally we prepared, for other purposes also, a 

 quantity of Ethyl-para-Etho.cyheiizalamino-a-Metliylcinnamylate : C^H^ 

 O.C,h].CH:N.C\H,.CH:C(CH,).CO.OC,H, for the transitiontempe- 

 ratures we found: i, = 95° C. and ;, r=r li7°,8 C, which numbers 

 do not agree with those given in the literature on this compound. 

 The purity of the three first-named substances is above all doubt ; 

 as for the two last mentioned compounds the certainty is somewhat 

 less, but it is very probable that the impurities possibly intermingled 

 with them, are not of any considerable importance. Since the beha- 

 viour of the three first substances differs appreciably from that of 

 the last two, the resp. l<-^curves are placed in two different diagrams. 



