ON CHEMICAL ATTRACTION. 



19S 



accords with and explains the phenomena of chemical com- 

 bination. 



Berthollet, in liis researches on this subject, has ascribed Cohesion suf>- 



many phenornena to the operation of the homosjeneous at- P<^^*"'' t" «<>• 



, . , . . , . . , difv the action 



traction, which unites integrant jjarticles, or, a.« it is termed of chemical af- 



by him, cohesion. He considers it as a powerful cause in fi"''?- 

 modifying combination; and especially, he attributes many 

 of tiK' results of complex affinity to its influence; he sup- 

 poses, that Bergman's Tables dr) not represent the real or- 

 der of the affinities of bodies, but rather, the degree of co- 

 hesion possessed by the compound when formed*. 



The following illustration is given of the mode of oper<t- Instanced in 



tion of this force of cohesion. " If a solution of sulphate sQlphate of 



^ . potash and 



*' of potash be mixed with muriate of lime dissolved in a muriate of 



" small quantity of water, the lime brought into contact ^'°*** 



" with the sulphuric acid will be more powerfully influenced 



** by the force of cohesion, than the potash. It is therefore 



" a force in addition to those which preexisted, and deter- 



•' mines the combination of the sulphuric acid with the lime, 



" and the precipitation of the new compound f." 



A? this paragraph comprehends much of thendoctrine of Ti'i"; instance 

 the influence of cohesion in modifying chemical union, it 

 deserves particular notice, and it will be of advantage to 

 make a few observations on it. 



It may be inquired, what is to be understood by the lime The lime does 



b, - , . -11 II- ■ 1 ^ t 1 not exert a 



emg brought into contact with the sulphuric acid r Ische- strontrer force 



niical contact or chemical union intended ? It is difficult to of cohesion 

 J ... . I/. 1 • I ■ I • II than the potash 



determine this qufStion. It chemical union be not inte. idea before decofn- 



by the word contact, it is improper to say, that the lime will position hj« 

 be more powerfully influenced by the force oP cohesion, than 

 the potash; for muriaie of lime is more solublethan sulphate 

 of potash. Let us suppose, that chemical union is intended, 

 and we shall still observe a manifest iir propriety in the ac- 

 count of the influence of cohesion which follows;^'' 



It is said, that cohesion is a force, in addition to those A povrer that 



which preexisted, and determines the combination of the *^.?f^ "°l/*^' 



*_ till an eiiect 



sulphuric acid and the lime, and the precipitation of the has taken pjaflft 



new compound. Now jt is to be observed, that this new caniiut have \ 

 ' pioduced tll« \ 



force can only be exerted, when *• the lime is brought into elfect- 



» See Rewarches, p. 106. f ibid, p. 105. 



O S '• contact 



