ELECTRICAL AND OTHER FAC TORS 245 



It is probably significant that the substances which 

 effect the greatest variety of contact catalyses, carbon 

 and the metals, especially platinum, belong in the class 

 of metallic conductors.' In such conductors, according 

 to the electron theory, there is ready transfer of electrons 

 from atom to atom, hence their electrical conductivity, 

 and other properties correlated with this peculiarity 

 (optical, etc.). It might be expected that such sub- 

 stances would also facihtate the transfer of electrons to 

 or from molecules with which they are in contact, and 

 thus furnish the conditions necessary for chemical 

 reaction. In other words, factors characteristic of the 

 metallic state may enter in contact-catalysis; for 

 example, the formation of local electrical circuits between 

 different parts of the metaUic surface, or oscillation 

 phenomena of a frequency corresponding with that of 

 the combination-electrons of the interacting substances 

 (resonator effects). An example of the former ty})e of 

 influence was seen in the simple experiment described 

 above, in w^hich the contact of a nobler metal or carbon 

 accelerates or "catalyzes" the formation of ferricyanide 

 filaments from zinc. Combinations of two contact 

 catalyzers seem often to be more effective than either 

 one alone; thus Shenstone found that "platinized 

 charcoal" was extremely effective in oxidizing alcohol, 

 "converting spirits of wine into \inegar in a lew hours," 

 and other cases of a similar kind are described by Bancroft 

 in a recent review.^ Presumably the two comj)onrnls 

 differ in their potential-difference against the medium, 



^ Contrast, e.g., the lack of catalytic power in colloidal silica (cf. 

 Taylor, Trans. Amer. Eleclrochcm. Soc, op. cit., p. 150). 



^Journal of Physical Chemistry, XXI (1917), 644; cf. pp. 607 iT. 



