CAT'ALYT'IC ACTION (Fr. catalytiqu•, from (;k. Kara? i'771:6C y ila)s. dissolving, from Kar(i, brio, down -I- to loose). A term applied in chemistry to the action of one substance upon a second. whereby the latter is subjected to elialige or decomposition. while the former, or acting substance, reiu:lins un altered. and doe, not combine with it. The phenomenon is also often spoken of as 'action if contact.' A well-known example of catalytic action is presented by the inversion of cane sugar—i.e. its decomposition into dextrose and levulose in the presence of acids. The quantity of acid employed fur produeing the inversion remains unchanged, none of the acid being actually used up: yet the reaction could not take place if the acid were not present. The true nature of catalytic action is as yet un known. It is now generally assumed. however. that catalytic agents do not rause reactions. but
only accelerate and thus render them appreci able. In certain eases it has even been possible to trace a quantitative relation between the nature and amount of the catalytic agent and the acceleration caused by it. (See REACTION, CHEMICAL.) The catalytic action of acid, (q.v.) is supposed to be due to the fact that in aqueous solution every acid dissociates, to a greater or less extent, into 'ions' charged with electricity, and it is the eleetro-positive hydrogen-ions (t) of the acid that are supposed to accelerate the reactions in question. It must he seen, however, that while this hypothesis is quite well founded on experimental facts, and thus certainly marks a step ahead. it does not by any means answer completely the question. What is the cause of catalytic action?