2c5 Rtfearcbes refye&'mg 



the force of cohefion produces a different effect, according 

 to the properties of the folvent. 



Q. 1 mixed an aqueous folution of plombate of foda with 

 the water of fulphate of foda; a flight precipitate only was 

 produced, though the fulphuric and muriatic acids, if added, 

 would have produced an abundant precipitate : when the ex- 

 periment was made with the muriate, the precipitate was 

 much more abundant than with the fulphate of foda. 



On the firft view, thefe effects may appear to be contrary 

 to the principles I have cftablifhed. For the fulphate of lead 

 is much lefs foluble than the muriate of lead ; fo that it 

 might be expected that a more abundant precipitate would 

 be obtained in the experiment made with fulphate of foda 

 than with muriate of foda. This happens otherwifc becaufei 

 fulphate of lead is much more foluble in foda, as I have af- 

 certained, than muriate of lead with excefs of oxide, fuch as 

 is precipitated in the preceding experiments. And the pre- 

 cipitation is not a direct confequence of the force of cphefion, 

 but arifes from the excefs of the force of cohefion beyond 

 that of the folvent. 



12. Thefe obfervations may be reduced to the following 

 refuks. 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; 

 moll infoluble combination is formed and feparated inde- 

 pendently of the proportions, which have an influence only 

 upon the ftate of thofe fubftances which remain in ijojution. 

 The refult of a mixture of different faline fubftances may 

 therefore be foretold from the mere confederation of folubilitv. 

 In this cafe, the adopted theory of the quiefcent and divellent 

 affinities does not miflcad us as to the principal refult; that 

 is to fay, the formation of the infoluble fait. But, as it is 

 not deduced from facts of a fuperior order, it will demand as 

 many experiments as particular facls. The doctrine does 

 not reft upon any foundation from which we can foretel the 

 mutual actions of fubftances prefented to each other; and 

 again, it has the difadvantage of affording no indication re- 

 fpecting the properties; which the remaining fluid portion 

 ought to exhibit when fubjected to evaporation or to the 

 action of a new fubftanee. Though this certain relation in 

 the refults may be productive of doubt as to the theory in 

 the foregoing cafe, it is not the fame when there is but a 

 fmall difference between the folubility of the combinations 

 taat may be formed. The proportions of the fubftances, in 

 4 quantity. 



