596 Scientific Proceedings, Royal Dublin Society. 
kind only will evidently be that it will come to consist of a mixture 
of both forms in practically equal proportions.’ 
We may compare with this the fact that several optically active 
substances admit of transformation, within certain limits of tem- 
perature, into inactive mixtures or racemic combinations of the two 
isomers of opposite sense, the change being accompanied by loss of 
optical activity. Consequently one-half of the molecules must 
experience a change to the inverse configuration. ‘The converse of 
the change referred to never takes place. Thus dextro-tartaric 
acid is converted into a mixture of inactive meso-tartarie and 
racemic acids by heating at 165°-170°; similarly optically active 
mandelic and: aspartic acids become inactive at 180°. Loss of 
optical activity also occurs when active amylie alcohol is warmed 
with soda, or when active leucin or tyrosin is heated with baryta.’? 
The chemical and physical properties of the mixture composed 
of two enantiomorphously related isomers are those common to the 
latter, 7.¢., all except some effects on enantiomorphous compounds 
and the effect on a ray of polarized light. The mixture here ~ 
referred to is the disturbed or liquid mixture in which the groups 
have every variety of orientation. If comparison be made between 
the two enantiomorphously-related assemblages and the mixture 
of them in equal proportions when the disturbances have subsided 
so that the assemblages are homogeneous, supposing the mixture 
to become so, we have the following interesting fact :— 
Any enantiomorphous generic symmetry characterizing assem- 
blages of the unmixed groups must disappear in the homogeneous 
mixture, because its continuance would necessitate its presence in 
both kinds, which, although consistent with certain kinds of twinning, 
would not be consistent with the existence of a single continuous 
assemblage. Those influences which produce enantiomorphism in 
the unmixed assemblages will, therefore, in the mixture neutralize 
one another. At the same time influences which are similar, and 
not enantiomorphously related in both, will be likely, to some 
extent, to survive. 
1 Compare ‘‘ Stéréochimie ’’ par van ’t Hoff und Meyerhoffer, p. 44. 
2 Hantzsch, ‘‘Grundriss der Stereochemie,’’ p. 34. Comp. ‘‘Stéréochimie’’ par van ’t 
Hoff und Meyerhoffer, pp. 41, 42. ‘‘Die Lagerung der Atomeim Raume,”’ 1894 ed., 
p- 30. 
