106 ©N THE NATURE OF PRECIPITATES* 



any direct experiment on this fubject, it is known, and I have 



myfclfobfcrved it, that the aqueous folution of barites poured 



into a folution of alcaline pruffiate, decompofes it by fimpl« 



affinity. 



Objection to the It is not the fame with the laft conclufion of Mr. Henry ; 



fcarites ap- ^ or tnou g n thefe acid folutions of barites are decompofed by 



proaehes to the the alcaiine pruffiates, precifelv like the metallic folutions by 



metals; ^ Q wa ^ Q f ( | ou ] 3 i e affinity, or the concurrence of divellent 



forces which determine the exchange of bales, it in norefpect 



follows that barites is on that account removed from the 



fceciufe the pre- earths, or approached to the metals. If that were the cafe, 



c.pitation is by the famc muft be affe rted f all fubftances, which prefent the 



double affinity, , * , 



*nd happens fame phenomenon, and it would no doubt be a matter of fur- 



with other prize to find this reafonin? lead us to allimilate to the metals 



earths and alka- !. * 'J - j , 



Iies > lime, jlrontian, magnejia, potu/fr, Joda, and even ammonia, 



fince the Pruffic acid can take all thefe bafes from their fol* 

 vents when the fum of the divellent affinities is in its fa- 

 vour, 

 namely potato j I have proved this in the cafe of potajli by the experiment 

 already related, where it is feen that it takes the Pruffic acid 

 from the lime, and yields to it the carbonic acid, 

 foda j This effect is Hill fpeedier with carbonate ot'foda, and pruf- 



fiate of lime, 

 ftrontianj The folution of nitrate of Jlrontian, is likewife decompofed 



by the pruffiate of lime. 

 lime j If a few drops of pruffiate of lime be poured into a folution 



of fulphate of ammonia in five or fix minutes, a whitifh frothy 

 film of the thicknefs of about a quarter of an inch thick fwims 

 at the furface, and is at laft depofed in fmall flakes, 

 magnefia j Laftly, fulphate of magnefia mixed with pruffiate of lime 



becomes clouded, and a precipitate is formed, 

 and becaufe the Let us therefore return to the true caufe of thefe pheno- 

 order of affinity mena> t he adion of the double affinities in which we frill 

 Mifrin&ivc cha- trace trie fimple elective attractions, the order of which is to- 

 wtter of bodies, tally independent of that feries, or arrangement in which we 

 place luch fubftances as have feveral other properties in com- 

 mon. ' Therefore the ftation which barites holds before pot- 

 ato in the columns of the attractions of pruffic acid, ought 

 no more to be applied in its claffification, than the pofition of 

 lime before the fixed alcalis in the columns of the oxalic, tar- 

 farous, and boracic acids, &c« With much more foundation 

 * it 



