hitherto bat 

 little known, 



#170 MUTUAIv PaECIPlTATIONS OF METALLIC OXIDE?, 



VIII. 



On the thiitual Ptecipitatiovs of Metallic Oxides. By 

 J. L. Gay-Lussac* 



The fubje£l is JL HAT we have (Irli fo litUe Information on the miUaal pre- 

 cipitations of metallic oxides, can only be attributed to the 

 complication of the refults which they offer. Indeed, a little 

 reflection will convince us that the oxidation, the afi^nity, the* 

 reciprocal a6lion of the oxides, and the property which they 

 have of n^ii'tralizing the acids unequalTy, are fo many caufes 

 trtility of the which muft join in the produflioti of the phenomena. It wouldy 

 tnveftigawoa. neverihelefs, be very ufeful to know the order in which the me- 

 tallic oxides precipitate from their folutions: the chemical ana- 

 lyfes,and moreefpecially the purification of metalli'cfalts, would 

 thence become eafier. It was with this intention that I have 

 made fome experiments, and if they have not been fufficiently 

 numerous to have enabled me to diftinguifh the influence of 

 every caufe, they, at leaf^, fiiow that of forae, and will ferve 

 to draw the attention to a fubje6l which is ftiilobfcure and very 

 complicated. 



I fliall begin by relating the refults vvhich I have obtained, and 

 fliall afterwards endeavour to determine their caufes. 

 Experiments Having taken a folution of green muriate of iron, I added 



with the green jq j^ ^ jj^^ig ^ed muriate of the fame metal, and I poured potafh 



anJ red muriates . , . . . \ n r rr ■ , \ /• ,. 



«f iron. "1^0 ihs mixture m a quantity atlealt lufhcient to decompole •!! 



the red muriate feparately. After agitation, the firft portions of 

 alkali yielded a precipitate of iron very much oxidedjwithoutany 

 mixture of black oxide; but by adding more and more of the al- 

 kali, it finiQied by being compofed of the two oxides. The filtered 

 liquor was then perfectly limpid, and no longer produced a blue 

 with the pruffiates, nor a black with the gallic acid; this proves 

 that the very oxided iron had been precipitated from it. On 

 making the inverfe experiment, that is to fay, on putting-* 

 little green muriate of iron into a larger quantity of red muriate,- 

 and precipitating it by the alkali, the black oxide was retained 

 in the (olutJon to the lall, and was not precipitated until after 

 all the red oxide. Hence therefore it refults that thejblack oxide' 



♦ Fronj iht Annales de Chinme, No. 145. of Vol. XLIX. p. i\^ 



of 



