to Inquiry info the Lanvs of JJiniiy. 



A R T I C L E V. 



On Cohefton and Cryjlalltzation. 



The cohefion of the particles of a body is owing to the mutual affinity of thofe particles : 

 it is a force which muft be overcome by the action of the fubftance which has a tendency 

 to combine with thofe parts, or to decompofe their combination. It is known that clay, 

 the particles of which have formed a ftrong cohefion by deficcation, is no longer attacked 

 by an acid which would be capable of diflblving it when in another ftate. 



The mutual affinity of the faline particles is the caufe of cryftallization ; and this modi- 

 fies the chemical a£tion in a manner which deferves attention. The author makes fomc 

 remarks on this fubje£l:, as well as on the force which produces cryftallization in a faline 

 folution. It eftablifhes a limit to which the degree of faturation of the fait in water can , 

 arrive j fo that if the water does not diflblve a greater quantity of it, this is not in confe- 

 quence of its affinity being fatisfied, but becaufe it is no longer fufficiently powerful to 

 overcome the refiftance of the cryftallization. From thefe and numerous other confidera- 

 tions, Cit. Berthollet concludes that the force of cohefion, which has hitherto been confi- 

 dered merely as an obftacle to folution, determines the quantities of fubftances which may 

 be brought into aftion in a liquid ; and thus modifies the conditions of chemical action. 

 It is this alfo which caufes thofe feparations that take place, either by cryftallization or 

 precipitation, and determines the proportions of the combinations which are formed by 

 reparation from the liquid, when the folubility or infolubility depends upon thefe pro- 

 portions* 



A R T I C L E VI. 



' ' On the Elafiicity of Subftances which exert a Chemical ABion, 



"When any fubftance efcapes in a gafeous ftate, in proportion as it is difengaged from 

 an intimate combination, the whole of that part which aflumes the elaftic ftate, ccafes to 

 afford any refiftance ; fo that the fubftance no longer afts in the ratio of its mafs. The 

 fubftance prefented may in this cafe render the decompofition complete ; and it will be 

 fufficient to ufe fimply that quantity which would have been requifite for immediately 

 forming the combination in which it is to enter, or at leaft a fmall excefs only will be 

 neceflary. 



This happens, as Cit. Berthollet obfervcs, with the carbonic acid, when it forms a 

 carbonate, and another acid is prefented to it. This laft acid, which a£ts in proportion to 

 its mafs, may, even with an affinity inferior to that of the carbonic acid, fucceffively expel 

 it from the tombination, even till none fliall remain, provided it be employed at firft in a 

 quantity rather greater than would have been neceflary for immediately forming its com- 

 bination with the bafis; 



From all thefe fafts prefented by the author, it follows that elafticity prodnces efFefls 

 analogous to thofe of the force of cohefion, by modifying, in an oppofitc dirc£tion> the 

 effects of the affinity proper to each fubftance. 



4 ' ARTICLE 



