158 Inquiry) into the Laws of Afftnit^. 



All fuUftances which are in folution exert a mutual a£lIon, which increafes thehr 

 folubility. Hence the reafon why it is difficult to obtain, by a firft cryftallization, each 

 fait in a ftate of purity ; except in the cafe where it diflfers confiderably from the otheis in 

 its force of cryftallization. Hence aiife the uncryftallizable refidues which fucceed the 

 cryftaliizations wherein falts are found in the liquid, which poflefs but little force of 

 cohefion. But here alfo the confideration of the proportions and of the folubility will ftill 

 be ufeful to predidt the exiftence and compofition of an uncryftallizable refiduum. 



While the fubftances are in folution, the a£lion which they mutually exert renders it 

 eafy to expel an acid from a combination, though, according to the received opinion, it 

 ought to aflume the place of another, and which was fuppofed to be weaker. 



When infolubility is confidered, it muft not be regarded as an abfolute property, but as 

 a property relative to the liquid in which a precipitation is made. Thus a combination 

 infoluble in water may lofe this property when the water holds alkali in folution. 



In all the experiments I have defcribed, and in feveral others which t have thought it 

 ^felefs to defcribe, I perceived no change of faturation, either after the mixture of the 

 neutral falts, or after the feparation of the precipitates or cryftaliizations which took 

 vplace, except in the experiments P, Qj made with a metallic fubftance. This permanent 

 ftate of neutralization, after the change of bafes which took place, feems to indicate that 

 the acids have conftant relations of quantity, in the neutral falts they form, with different 

 alkaline or earthy bafes. So that if the fulphuric acid for example, be found in greater 

 proportion in the fulphate of pot-afh than in the fulphate of lime ; the muriatic acid with 

 which it may make an exchange of bafe will be found in the fame ratio of quantity 

 in the muriate of lime and in the muriate of pot-afh; a conclufion that would not agree 

 'with the proportions which have often been attributed by chemifts to the component parts 

 of the different non-metallic falts. Guyton has already made feveral very juft and im- 

 portant reflexions on this fubjcfl, and he quotes the obfervations of Richeter, with whofc 

 woik I am not yet acquainted. i^Annaks de Chimie, torn. xxv. p. 292). 



("To be continued.) ; 



The reader will perceive that I have fuppofed this treatife to have been concluded in a 

 former number ; into which error I was led by the want of any intimation in the Annals 

 that more was to be expefted. But every cultivator of fcience will rejoice with me that 

 thefe refearches, which fhew the wonderful fkill and acutenefs of their author, and muft 

 produce an almoft total revolution in our obfervations an4 reafoning on chemical efie£t$, 

 ace more exteofivc than we at iiift imagined.— N. 



VII. 



