ON THE PHENOMENA AND THEORIES OF SOLUTION. 445 



and the resistance offered by gases in virtue of their elasticity and by 

 solids in virtue of their cohesion. 



But Berthollet seems to have regarded chemical affinity as very closely 

 connected with the cause of cohesion, if not identical with it. In the 

 English translation by B. Lambert, 1804, to which alone I have had 

 access, the following passages occur in the introduction, pp. xviii et seq. : 

 ' The first effect of affinity to which I call attention is that produced by 

 the cohesion of the particles which enter into the composition of a body ; 

 it is the effect of the reciprocal affinity of these particles which I dis- 

 tinguish by the name of the force of cohesion, and which becomes a 

 force opposed to all those tending to cause them to enter into another 

 combination, while it, on the contrary, tends to reunite them. 



' Every af&nity which tends by its action to diminish the effect ot 

 cohesion ought to be regarded as a force opposed to it, and of which the 

 result is solution. When, therefore, a liquid acts on a solid, the force of 

 solution can produce the liquefaction of the solid if it is superior to that 

 of cohesion ; but this effect sometimes takes place immediately and 

 sometimes it requires that the cohesion should be first weakened by 

 a commencement of combination ; there are circumstances in which the 

 liquid can only act on the surface of the solid and wet it ; finally the 

 solid cannot even be wetted when its affinity with the liquid does not 

 produce an effect greater than that of the mutual affinity of the parts of 

 this latter. 



' These two forces, therefore, according to their relations produce 

 different results, which must be distinguished, but which are not to be 

 attributed, in conformity with the opinion of some philosophers, to two 

 affinities, one of which they have considered as chemical and the other as 

 derived from the laws of physics,' &c. 



The same views with illustrative examples are expressed in Berthollet's 

 work on the ' Laws of Chemical Affinity.' On page 63 of the English 

 translation, by M. Farrell, 1804, we find this passage : ' Solvents act on 

 bodies which they dissolve by their affinity and quantity like all sub- 

 stances which tend to combine ; and whatever has been said of combina- 

 tion in general is applicable to them.' 



It seems pretty clear, therefore, that Berthollet regarded solution as 

 an act of chemical combination. He seems to have got some of his ideas 

 from Guyton de Morveau, who some years before had published experi- 

 ments on the adhesion of solids to liquids with the object of proving that 

 ' the adhesion of solids to liquids is in proportion to their affinity of 

 solution.' ' 



L. Gmelin (' Handbook,' vol. i. p. 112) summarises very clearly the 

 views prevailing up to his time : ' Cohesion appears to exert a much more 

 decided influence (than gravitation) on the decomposition of chemical 

 compounds — at least of the less intimate kind. The hitherto received 

 theory on this matter is as follows :— When a solid body dissolves in a 

 liquid, the cohesion of the solid acts in opposition to the dissolving power 

 of the fluid ; the two forces tend to equilibrate each other ; and in pro- 

 portion as the fluid takes up more and more of the solid, its tendency to 

 dissolve a further quantity — or in other words, its affinity for the solid — 

 diminishes, and ultimately becomes no greater than the cohesion of the 



• Footnote in Berthollet's Chemical Affinity, English ed. p. 43 ; and Ann. Chim. 

 vii. p. 32. 



