690 The Philippine Journal of Science 
The reactivity in this case is much less than in the cases pre- 
viously described, necessitating as it does a high temperature. 
The heat may activate the xylene as well as the hexaphenylethane, 
so that the problem of the reaction mechanism is more compli- 
cated. The general course of the reaction is analogous to the 
substitution of chlorine in the xylene ring. 
SUMMARY 
(1) An explanation of the constitution of hexaphenylethane 
based on the octet theory of valence has been proposed. 
(2) The physical and chemical properties of hexaphenylethane 
have been shown to be more satisfactorily explained by this 
theory than by the old affinity unit theory of valence. 
