THE COLLOIDAL CONDITION 217 



rangement which constitutes the reaction. Clearly, the time 

 required for the substances to come into molecular contact will be 

 greatly diminished if they are mutually adsorbed in large quan- 

 tities on the extended surface area of some colloidal catalyst which 

 is present in the mixture rather than scattered throughout its 

 entire volume. The application of this principle to the catalysis of 

 hydrolytic reactions is not apparent, if it is considered that the 

 H 2 molecules which cause the hydrolysis are those of the solvent 

 itself; but is clear on the assumption (which is discussed in the 

 following chapter) that the water which enters into a colloidal 

 complex is in multimolecular form, represented by the formula 

 (H 2 O)n, in which the oxygen atoms are quadrivalent and, hence, 

 much more active chemically than as illustrated in the simple 

 solvent action of water. 



Hence, the surface adsorption of reacting bodies by a colloidal 

 catalyst may have a very important influence in decreasing the 

 time required to bring the reacting molecules into intimate con- 

 tact, and so increasing the velocity of the reaction. 



But the colloidal condition of the catalyst may also aid in 

 decreasing the " chemical resistance " which tends to slow up the 

 reaction. Chemical resistance may be understood to be the inter- 

 nal molecular friction of the densely packed atoms within the 

 reacting molecule, which tends to prevent the molecular rearrange- 

 ment and so to prolong the second period of the reaction time. To 

 overcome this friction and so decrease the reaction time, some form 

 of energy is necessary. If there be present in the solution in 

 which the reaction is taking place some colloidal catalyst, and if 

 the reacting bodies are concentrated at the surface boundaries 

 between the two phases of the colloidal system, they may be con- 

 ceived to be within the sphere of influence of the surf ace energy 

 of the dispersed particles of the catalyst, so that this may furnish 

 the energy necessary to overcome the chemical resistance of the 

 reacting bodies, and so to speed up the second portion of the 

 reaction time. 



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 



