2*7^ MUTUAL PRECIPITATIONS OF METALLIC OXIDES. 



3d. That the oxide of filver which precipitates thofe of zinc 

 and copper, neutrahzes the acids better than them. 

 Alumine is pre- If, befides, we refleft, that alumine, whofe folutions are 

 taHk oxide's™^' '^'*^''y ^^''^> '^ precipitated by feveral metallic oxides which 

 neutralize the acids better than it; that, according to the e»- 

 and by glucine. periments of Vauquelin, glucine decompofes aluminous falts, 

 and that its folutions are more neutral than thofe of alumine, 

 Magnefia preci- although they are not entirely fo ; and, finally, that magnefia, 

 rid oxider^"^^ ^'^'^"^ neutralizes the acids perfedly, precipitates the pre- 

 ceding earths, and a very great number, not to fay all, the 

 oxides from their folutions; we cannot abftain from allowing 

 that, if the property poffeflTed by the metallic oxides and feve- 

 ral earths of neutralizing the acids unequally, is not the only 

 caufe of the decompofitions which I have detailed, it is at lead 

 one of the principal. 

 The affinity for We may alfo conclude from the fame experiments, that the 

 *luk! '^ """^ ^^ metals which have a great or a weak affinity for oxigen, do 

 not enjoy any particular property with refpedl to their mutual 

 precipitations; for we fee that iron, in a flate of great oxida- 

 tion, is precipitated by a number of oxides which it precipi- 

 tates when it is lefs fo ; and, that there are feveral oxides 

 which contain lefs oxigen than that of zinc, which precipitate 

 the latter, while tliere are others which are precipitated by it. 

 The affinity of the different metals for oxigen is therefore 

 rejected as the caufe of the mutual precipitations of their 

 oxides; but can the greater or lefs oxidation of the fame metal 

 occafion a variation in the affinity of the oxide for the acids ? 

 This opinion has been promulgated by Cit. Berthollet in his 

 The ftate of the Chemical Statics *, and he has grounded it upon feveral fa6ts, 



nityoftheox- means whatever, forms another fait with lefs acid. This hap- 

 ides for the ^^^^ j^ j]^g oxigenated muriate of mercury, which, by expo- 

 fure to light, or by being brought into contad with iron, is 

 changed into white muriate by abandoning fome of its acid.' 

 Although thefe, and other fimilar fads, are capable of a dif- 

 ferent interpretation, other confiderations, which I fliall omit 

 here, becaufe they would lead me too far, induce me to par- 

 ticipate in the opinion of Citizen Berthollet; but I do not be- 



* A tranflation of which will be publiflied by Mawman, in the 

 Poultry, about the middle of the prefent montU. 



lieve 



