Inquiry Into the Lawt of jiflnity, i^f 



On the firft view, thefe efFe£ls may appear to be contrary to the principles I have 

 eftabliflied. For the fulphate of lead is much lefs foluble than the muriate of lead } fo that 

 it might be expefted that a more abundant precipitate would be obtained-in the experiment 

 made with the fulphate of foda than in that with the muriate of foda. This happens 

 otherwife becaufe the fulphate of lead is much more foluble in foda, as I have afcertained> 

 than the muriate of lead, with excefs of oxide, fuch as is precipitated in the preceding ex- 

 periments. And the precipitation is not a direiSt confequence of the force of cohefion, but 

 arifes from the excefs of the force of cohefion beyond that of the folvent. 



12. The obfervations which I have prefcnted in this memoir may be reduced to the 

 following refults. In the complex affinities, or double affinities, the force of cohefion, 

 when confiderable, and differing much in its intenfity among the combinations which may 

 be formed, determines a change of bafes, in fuch a manner that the moft infoluble com- 

 bination is formed and feparated independently of the proportions, which have an in- 

 fluence only upon the ftate of thofe fubftances which remain in folution. The refult o£ 

 a mixture of different faline fubftances may therefore be foretold from the mere con- 

 fideration of folubility. 



In this cafe the adopted theory of the quiefccnt and divellent affinities does not miflead us, 

 as to the principal refult, that is to fay, the formation of the infoluble fait. But as it is not 

 deduced from fa£ls of a fuperior order, it will demand as many experiments as particular 

 fa£ls. The doctrine is not eftablifhed upon any foundation from which we can foretel the 

 mutual aflions of fubftances prefented to each other j and again it has the difadvantage of 

 affiarding no indicarion refpefting the properties which the remaining fluid portion ought 

 to exhibit when fubjc^led to evaporationj or to the a£lion of a new fubftance. 



Though this certain relation in the refults may be produftive of doubt as to the theory in 

 the foregoing cafe, it is not the fame when there is 'but a fmall diftance between the folu- 

 bility of the combinations that may be formed- The proportions of the fubftances, in 

 quantity, then determine the formation of the different falls, either by a firft cryftallization, 

 or by cryftallizations which, by fubtra£ting fpme of the parts, muft alter the proportion, 

 and occafion a difference in the difpofition of the remaining principles to cryftallize in the 

 fucceffive formation of the falls. It is here that the application of the theory of the 

 quiefcent and divellent affinities may produce many errors, by leading us to conclude from 

 the commencement of the phenometion that the fubfequent effe£ts will be all of the- fame 

 defcriplion, though in reality a fucceffion of oppofite combinations may be eftablifhed, 

 according to the forces which are made to aft at the moment of their refpectivc- fcparations. 



The joint confideration of the difference of folubiHty, and of the proportions employed, 

 or which vary at the^different periods of ah o|)t4raiion, muft cifinfequently be Our folfe guide 

 in the explanation of the fucceffive formation of different falts w Kiel* have no grea^ 

 difference in folubility. It is true, neverthelefs, that the mutual action of the fubftances 

 therafelves may produce fome difference in the refults,. which would, be indicated by the 

 preceding obfervations;. 



AU 



