IS THE ORGANISM A THERMODYNAMIC 



MECHANISM? 



By JAMES JOHNSTONE, D.Sc, University, Liverpool 



Let us consider the chemical reactions represented by the 

 following equations : 



(i) CH, + 20 2 = CO, + 20H 2 + 213,800 gram-calories ; 



Methane 



(2) HC1, aq. + NaOH, aq. = NaCl, aq. + OH 2 + 13,700 grm.-cal. ; 



(3) 2C 2 H 2 + 50 2 = 4CO, + 2OH, + 310,000 grm.-cal. ; 



Acetylene 



(4) CS, = C + S, + 28,700 grm.-cal. 



Carbon disulphide 



The first two reactions are typical examples of processes 

 which occur commonly in organic and inorganic systems. The 

 first represents an oxidation, and the second a neutralisation. 

 When methane burns completely in oxygen carbon dioxide and 

 water are formed, and a certain quantity of heat is evolved. 

 When very dilute hydrochloric acid is added to very dilute 

 caustic soda a neutral salt, also in dilute solution, is formed. 

 If quantities of each of the reacting substances equal to the 

 molecular weights, in grams, represented by the formulae take 

 part in the chemical changes, quantities of heat represented by 

 the numbers given on the right-hand sides of the equations are 

 evolved. The reactions are exothermic. In most chemical 

 changes the " intrinsic energy " contained in the substances 

 before they react is greater than is the intrinsic energy con- 

 tained in the products formed by the reaction, and the balance 

 of energy appears as evolved heat. The 213,800 gram-calories 

 of equation (1) are the heat of combustion of a gram-molecular 

 weight of methane; and the 13,700 grm.-cals. of equation (2) are 

 the heat of neutralisation of gram-molecular weights of hydro- 

 chloric acid and sodium hydrate. 



Equations (3) and (4) represent also exothermic reactions. 

 In the first of these acetylene burns completely in oxygen ; and 

 in the second one carbon disulphide is decomposed into its 

 elements. When acetylene burns in this way 310.000 gram- 



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