456 PRINCIPLES OF CHEMISTRY 



Which are diametrically opposite ; yet among these, dynamical equilibrium 

 establishes itself not by excluding one or other of the forces, but regulating 

 them all. So the chemist finds in the flame of the blast furnace, in the 

 formation of every salt, and, with especial clearness, in double salts and in 

 the crystallisation of solutions, not a fight ending in the victory of one side, 

 as used to be supposed, but the conjunction of forces ; the peace of dynamic 

 equilibrium resulting from the action of many forces and affinities. Car- 

 bonaceous matters, for example, burn at the expense of the oxygen of the 

 air, yielding a quantity of heat, and forming products of combustion, in 

 which it was thought that the affinities of the oxygen with the combustible 

 elements were satisfied. But it appeared that the heat of combustion was 

 competent to decompose these products, to dissociate the oxygen from the 

 combustible elements, and therefore to explain combustion fully it is neces- 

 sary to take into account the equilibrium between opposite reactions, between, 

 those which evolve and those which absorb heat. 



In the same way, in the case of the solution of common salt in water, it 

 is necessary to take into account, on the one hand, the formati6n of compound 

 particles generated by the combination of salt with water, and, on the other, 

 the disintegration or scattering of the new particles formed, as well as of 

 these originally contained. At present we find two currents of thought, 

 apparently antagonistic to each other, dominating the study of solutions : 

 according to the one, solution seems a mere act of building up or association ; 

 according to the. other, it is only dissociation or disintegration. The truth 

 lies, evidently, between these views ; it lies, as I have endeavoured to prove 

 by my investigations into aqueous solutions, in the dynamic equilibrium of 

 particles tending to combine and also to fall asunder. The large majority of 

 chemical reactions which appeared to act victoriously along one line have 

 been proved capable of acting as victoriously even along an exactly opposite 

 line. Elements which utterly decline to combine directly may often be 

 formed into comparatively stable "compounds by indirect means, as, for ex- 

 ample, in the case of chlorine and carbon ; and consequently the sympathies 

 and antipathies which it was thought 'to transfer from human relations to 

 those of atoms should be laid aside until the mechanism of chemical rela- 

 tions is explained. Let us remember, however, that chlorine, which does not 

 form with carbon the chloride of carbon, is strongly absorbed, or, as it were, 

 dissolved, by carbon, which leads us to suspect incipient chemical action even 

 in an external and purely surface contact, and involuntarily gives rise to 

 conceptions of that unity of the' forces of nature which has been so ener- 

 getically insisted on by Sir William Grove and formulated in his famous 

 paradox. Grove noticed that platinum, when fused in the oxyhydrogen 

 flame, during which operation water is formed, when allowed to drop into 

 water decomposes the latter and produces the explosive oxyhydrogen mixture. 

 The explanation of this paradox, as of many others which arose during the 

 period of chemical renaissance, has led, in our time, to the promulgation by 

 Henri Sainte-Claire Deville of the conception of dissociation and of equili- 

 brium, and has recalled the teaching of Berthollet, which, notwithstanding its 

 brilliant confirmation by Heinrich Rose and Dr. Gladstone, had not, up to 

 that period, been included in received chemical views. 



