MUTUAL PIlEClJ^ltATION-3 OF METALLIC OXIDES. 2^3 



t)ored, in great part, of oxide of filver, becaufe the precipi- 

 tation took place only where the alkali was poured in ; but this 

 precipitate was gradually covered with oxide of copper, and, 

 by agitation, it was in a little time replaced by the latter. An 

 addition of alkali having given me a precipitate of oxide of 

 filver which was not re-diilolved^ I filtered it, and obtained a 

 liquid perfedly colourlefs, which did not contain any more cop- 

 per. If it is wi(hed to avoid the potafti in the folution, a part 

 of the impure nitrate of filver may be decompofed feparately, 

 and the precipitate, well waftied, may be employed to feparate 

 thecopper of the other part. This fimple method of Separating 

 copper from a folution of (ilver may be very ufeful in labora- 

 tories, and even in large works. 



The oxide of filver alfo decompofes the nitrate of zinc j and 

 the oxide of manganefe the muriate of copper. 



In wiiat precedes I have, for Ihortnefs, fuppofed that the The preclpltatei 

 precipitates were pure oxides; but I am far from believing ?^^ "°' P""^^ ^''^ 

 this to be the cafe ; on the contrary, I confider nearly all of 

 them as true falts. Copper, for example, was always preci- 

 pitated of a bluilh-green, although the fhade varied with the 

 oxides which were precipitated 5 and it is now well afoer- 

 tained by Prouft and the younger BerthoIIet, that the green 

 and blue oxides of copper retain fome of the acid. 



Such are the fads as I have obferved them, and on which 

 alone I ftiall make fome refiedtions. Although they are too 

 few to have eiiabled me to lix on all the circumftances which 

 concurred in their produdion, the examination of them will, 

 however, develope fome of ihera. 



In fact, if we direct our attention fo the acidity of the dif- Inferences f.om 

 ferent falts noticed above, we fliall fee, ofT'^Sof 



]fi. That the iron which is but little oxided, and the highly the acidity. 



oxided mercury which precipitates the red oxide of iron, the Neutralization 



oxide of zinc, and that of copper, approach nearer to neutra- of the acids by 



, , ' ^ ^^ , oxides. 



iization than the latter. 



2d. That the zinc and manganefe which precipitate the cop- 

 per, neutralize the acids better than it *. 



* By neutrali^^ing the acids more or lefs, I mean that property 

 jjoffeffld by the metallic oxides, and fome earths, fuch as giucine 

 and alii mine, of approaching mo e or lefs, hx tiieir comb'nauons 

 with the acids, to the term of neutralization. 



Voi>. VIII. —August, ISO-i. T 2d, 



