( 473 ) 



of the homologous series is plainly visible here. In what follows 

 there will be described, firstly, the thermic, and then the microscopic 



behaviour of these substances. 



§ 2. The Thermometric Behaviour of these Substances. 



Cholesterol- Laurate exhibits the following phenomena: The isotropous 

 fusion L of this substance has still, at lOO 3 the consistency of gly- 

 cerol, and gradually thickens on cooling. At 87°. 8 C. (= t 3 ) there 

 suddenly occurs a peculiar violet and green opalescence of the phase, 

 which commencing at the surface, soon embraces the whole phase. 

 The still transparent thin- jelly-like mass quite resembles a coagulating 

 colloidal solution; the opalescence is analogous to that often noticed 

 in the separation of two liquid layers. 



As the cooling proceeds, the opalescence colours disappear and the 

 mass gradually becomes less transparent and also more liquid. It is 

 then even thinner than the isotropous fusion L. This doubly-refracting 

 liquid A now solidifies at 82°. 2 C. (= t { ) to a crystalline mass S, 

 accompanied b}' a distinct heat effect. 



If, however we start with the solid phase S and subject the same 

 to fusion, the behaviour is apparently quite different. The substance 

 softens and yields after some time a thick doubly-refracting mass, which 

 will prove to be identical with the phase A. On heating further the 

 viscosity decreases, and at about 86' it becomes very slight. There 

 is, however, no sign of opalescence this time. The turbid mass may 

 be heated to over 90°, without becoming clear and now and then A 

 seems as if solid particles are floating in the liquid phase. At 90°. 6 C. 

 (== t h ) everything passes into the isotropous fused mass L. The micros- 

 copical investigation shows, that between A and L another stable, 

 less powerfully refracting liquid phase B is now traversed, and that, 

 owing to retardation occurring, the phase S may be kept for a few 

 moments adjacent to L, when A and B have already disappeared. 



This is therefore, a case where a substance may he heated << few 

 degrees above its actual melting point without melting. 



It should, however, be observed that the order of the temperatures 

 is here quite irreconcilable with the phenomena considered possible 

 up to the present, with homogenous substances ; the temperature of 

 90°.6, at which these crystals disappear in contact with L finds no 

 place in the ;>£-diagram of Fig. 1. Such a position of the said 

 temperatures might be possible, when the system could be regarded 

 as containing two components, for instance, if there was question 

 of tautomeric forms which are transformed into each other with 

 finite velocities. I think it highly probable that in all these substances, 



