From these considerations, it would appear that the colloidal condition of such catalysts as enzymes, etc., has much to do with their ability to increase reaction velocities, both by reducing the time necessary for the reacting bodies to come into molecular contact and by furnishing the energy to overcome the chemical resistance to the molecular rearrangement which constitutes the reaction itself. Evidence in favor of the accuracy of this view of the nature of the catalytic action of colloidal substances is afforded by the facts that catalysts accelerate the velocity of reversible reactions in either direction and that they do not change the point of final equilibrium, in any case; that is, they do not affect the nature or direction of the reaction, but only accelerate a chemical change which would otherwise take place more slowly because of the stability (or chemical resistance) of the molecules involved, or their inability to come quickly into intimate molecular contact. These facts and principles have been clearly established in many studies of the nature of enzyme action (enzymes are typical colloidal catalysts) and probably apply equally well to the action of other types of colloidal catalysts. On the other hand, the catalytic action of certain inorganic and non-colloidal substances, such as the action of acids in accelerating the hydrolysis of carbohydrates, etc., may be conceived to be due to chemical influences upon the internal molecular resistance, which are similar in their effects, but entirely different in their mechanism, from the physical effects of the surface boundary phenomena of the colloidal catalysts. INDUSTRIAL APPLICATIONS OF COLLOIDAL PHENOMENA