CHAPTER V 

 LIBERATION OF ENERGY 



(3) ENERGY OF SUBSTANCE IN SOLUTION 



" The problem of achieving perpetual motion contrary to the second law " 

 (of thermodynamics) " is that of bringing order and direction once more into 

 the chaotic rush of the molecules, to marshal and drill the mob so that once 

 more they can act together to produce a common effect." SODDY. 



Osmotic Pressure. 



The first process that affects food is that of digestion. Diges- 

 tion is merely the breaking down of the material supplied so that 

 it can pass through the absorbing medium in solution. It follows 

 (from this statement and from the physical state of the living 

 cell) that all energy manifested by an animal comes from sub- 

 stances in solution. No material is of any use for energy purposes 

 unless it is soluble, and until it is rendered soluble it cannot be 

 absorbed and utilised. 



That is, the available energy of a cell may be divided into : 



(1) The potential energy inherent in the various substances 

 that compose it. 



(2) The kinetic energy these substances have because they are 

 in solution. 



These two statements together imply that the mere solution 

 of a substance may so alter the state of that substance that 

 energy is set free. (Cf. heat evolved on diluting concentrated 

 H 2 SO 4 .) Further, it may be inferred from this that the physical 

 conditions which determine the character and behaviour of living 

 cells depend on the composition of the latter and on their environ- 

 ment. 



Far-reaching dicta such as these cannot be accepted without 

 question. First of all, has the solution of a substance any effect 

 on its energy content ? Does sugar, for instance, lose some of 

 its energy-content when dissolved in tea ? Does the bound 



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