PRINCIPLE OF LE CHAT ELI ER 9 



of this is given out in a year (Chap. XIII.). To enable mankind to 

 avail hiniscli' of this kind of energy, some means will have to 

 be devised for speeding up and eontrolhng the output. As 

 Professor Soddy puts it : " Primitive man froze on the site of 

 what are now coal mines, and starved within sound of the water- 

 falls that are now working to provide our food. The energy 

 was there, the knowledge to utilise it was not. So while we are 

 leading eramped lives and fighting among ourselves, whether in 

 peaee or war, for a modicum of the means of existence, science 

 tells us that, in the commonest materials that make up the frame- 

 work of the world, there is energy of a magnitude of which we ha\-e 

 no experience, and the means of livelihood of which we have no 

 standard. The energy is there. The knowledge that can utilise 

 it is not — not yet." 



Physiological availability. 



This introduces a further point. The energy-content of cellu- 

 lose is much the same as that of starch, yet as a source of energy 

 for man the former substance is useless, while the latter is perhaps 

 his main source of energy supply. An inorganic example may 

 make this clearer. Two lakes may be exactly similar except that 

 one has an outlet, while the other is surrounded by impassable 

 mountains. The water power, i.e. the stored energy of the former, 

 is utilisable, while the latter could not be tapped without arduous 

 engineering labours. The energy-contents of the radio-elements 

 (atomic energy) of cellulose (as human food) and of the undrained 

 lake are said to be non-available. Future scientists may discover 

 how to draw upon this surplus energy supply. 



Principle of Le Chatelier. 



" Every system in chemical equilibrium, under the influence of a 

 change of any single one of the factors of equilibrium, undergoes a 

 transformation in such direction that, if this transformation took place 

 alone, it ivould produce a change in the opposite direction of the 

 factor in question. The factors of equilibrium are temperature, 

 pressure and electromotive force, corresponding to three forms of 

 energy — heat, electricity and mechanical energy.'' 



The above is the principle as enunciated by Le Chatelier in 1884. 

 Consider the energy changes in the formation of water where 

 hydrogen and oxygen combine with the evolution of 68-3 Calories 

 for every gram molecule formed. The equation of the reaction 

 may be written 



2H2 + 02^ 2H0O + 136-6 Calories. 



