Physics. — "Coritrihutions to the study of liquid crystals. \\\. Meltiru) 

 and congelation-])henomena lüith para-azoxy-anisol." By Dr. 

 W. J. H. Moll and Prof. L. S. Ornstein. (Communicated 

 by Prof. W. H. Julius). 



(Communicated in the meeting of September 29, 1917). 



In our seoond paper on the extinction of liquid crystals we observed, 

 that among others with para-azoxy-anisol there is, with regard to 

 the extinction, a ditference between the liquid crystalline condition 

 which arises by melting the solid crystals ("exsolid") and that which 

 arises in cooling the isotropic liquid ("exliquid"). Where with 

 para-azoxy-anisol we had stated the existence of two solid phases, 

 the question lay at hand whether in exsolid and exliquid we had 

 perhaps got two different liquid crystalline phases. To make this 

 ont a research after the exact position of the points of transition 

 was desirable. 



Method of Research. 



There we made use of a kind of radiation calorimeter, which is 



schematically represented in figure 1. 

 The substance to be examined (about 

 \ cm.') half filled a gold beaker 

 M with thin walls, against which 

 on the exterior on the one side a 

 brass wire, on theotheraconstantane 

 wire has been soldered. Tlie two wires 

 form a thermoelement, by the help 

 of which the temperature of the 

 beaker and its contents is measured ^) 

 and serve at the same time to hang 

 it within a brass cylinder. This 



1) Before we came to this way of fixing up the "thermobeaker", we had followed 

 the usual method for our determination of the temperature, i.e we liad placed a 

 thermometer and later on a thermoelement within the substance to be melted. Then 

 a number of "Schmutzeffecte" were produced, which on close investigation had to 

 be ascribed to convection currents. Our method is of course quite free from this 

 disturbance. 



