ACTION OF ENZYMES 45 



than equilibrium, as a res alt of reaction energy will be set free, 

 and the energy so set free is the driving force towards equilibrium, 

 or a tendency towards chemical equilibrium. But whether there 

 will be any movement towards equilibrium or the reverse, and 

 the velocity of that movement, depend entirely upon how far 

 there is opposition to such movement, by the resistance of other 

 forms of energy present in, or brought to bear upon the system 

 by any agency such as a catalyst, or upon how far such resisting 

 forms of energy are diminished by the action of any such agent 

 which may be present in the system. 1 



Chemical energy is not peculiar in this respect, and does not 

 stand isolated from other forms of energy. Water standing in two 

 reservoirs, unconnected by a channel through which the water 

 can flow, will remain at a constant difference in hydrostatic pressure 

 for ever, and if there be a channel of communication between 

 them, the rate of flow, that is, the velocity with which the potential 

 difference is equated out, will vary not only with the difference in 

 potential but with the resistance to the flow of water in the con- 

 necting channel. Further, if there is a turbine, or properly con- 

 structed reversible pump, on the channel of communication between 

 the two reservoirs, then the water as it flows from the higher to 

 the lower level can be made to give out energy which by suitable 

 transforming machines can be changed into any form of energy ; 

 or conversely, if external energy is supplied to the pump, at a 

 sufficiently high potential, it can be made to work the pump in 

 the opposite direction, and the absorbed energy can so be utilised 

 to force the water in the opposite direction from the lower reservoir 

 to the higher reservoir, so that the difference in hydrostatic potential 

 increases instead of diminishing, as it would do if the system were 

 not operated upon by other forms of energy from without. 



Similarly in the case of electrical energy, if there is no path 

 of conduction between two charged conductors at different 

 potentials, there can be no equalisation of potential between the 

 two conductors ; if a path is provided the velocity of the energy 



1 Lest the reader should think that because these equations do not lead 

 directly to expressions for the velocity of reaction that they are therefore useless, 

 it may be pointed out, that they do give the conditions for equilibrium quite 

 truly when no energy is imparted to the system from without. For although 

 variations in resistance will alter the velocity with which equilibrium is reached, 

 at the equilibrium point itself the velocity becomes zero, and the resistance has 

 accordingly no effect upon the equilibrium point. 



