July, 1958
VOLUMEEFFECTS ON MIXINGIN LIQUIDBi-BiCl, SYSTEMS
that are known to undergo polymerization catalyzed by electrophilic reagents. On the basis of data available, it is not possible t o indicate a mechanism by which surface modification takes place when silica is ground in the presence of hydrocarbons such as benzene and cyclohexane. In view of the energy required to break the silicon-to-oxygen bond it seems probable that under grinding conditions highly reactive sites are formed. Thus, temperatures of short duration
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843
approaching 1000" have been noted during friction of silica surfacesQand the ball-milling of quartz jn a calorime,ter has indicated quartz t o have a specific surface energy of 107,200 ergs/sq. cm.l0 I n view of these high energy requirements, it appears probable that a dual thermal-ionic process is operating during the grinding of silica in the presence of various organic compounds. (9) F. P. Bowden, Nature, 166, 330 (1950). (10) A. I
