18 CHEMICAL TRANSFORMATIONS 



of energy from one given form to another can only be estimated by 

 statement of corresponding changes in other forms of energy as a 

 result of the reaction. The two forms of energy in which such 

 changes of energy can best be expressed are heat energy and 

 mechanical work or dynamical energy, and it is for this reason that 

 energy exchanges are considered upon a thermo-dynamical basis. 



Energy equilibrium or reaction is determined by the values at any 

 given time of the potential factors of the various forms of energy, 

 by the facilities presented in the system for potential equalisation, 

 and by the manner in which energy is bound or related to par- 

 ticular forms of matter in the system. In so far as any particular 

 form of energy is free to distribute itself throughout the system 

 that particular form of energy tends to equalise its potential all 

 through the system, and hence the energy always passes from a 

 point of higher to a point of lower potential. Thus in any system 

 where redistribution is possible heat always passes from a position 

 of higher to one of lower temperature, electricity from a higher 

 to a lower electrical potential, a fluid or gas from a higher to a 

 lower level of pressure, and so on for every form of energy. In 

 any such change the velocity of equalisation is directly proportional 

 to the difference in potential, and inversely proportional to what 

 is termed the resistance. The resistance, however, means only that 

 the equalisation is opposed by the potential factor of some other 

 form of energy, and that this opposition has to be overcome in 

 effecting the equalisation. If the potential factor of this opposing 

 energy is sufficiently high the equalisation may be entirely stopped, 

 or its speed only may be lessened so that the equalisation takes 

 longer and proceeds with diminished intensity. 



It is impossible for equalisation of potential, or change 

 towards equalisation of potential, of any form of energy to take 

 place without conversion of a portion of the energy so changing 

 potential into other forms, and all physical measurements of 

 change in potential are based upon changes of the energy into 

 other forms. 



In any condition of equilibrium of a system there is a balance 

 between the intensity factors of the various forms of energy 

 capable of interacting with one another, and that balance is de- 

 pendent upon the facilities provided in the system for interaction 

 between the various forms of energy. Further, in the absence of 

 equilibrium the velocity or intensity of reaction is dependent on 



