Vauquelin precipitates the oxide of palladium from the muriate by potash; it appears of a red brown colour, and is probably a hydrate; when washed and dried in a moderate heat, it becomes black, it loses 20 per cent. by a red heat and becomes metallic. This would give 25 oxygen on 100 metal; but as he finds the sulphuret to be 100 metal with 24 or 30 sulphur, nearly agreeing with Berzelius, it is very probable that a moderate heat does not free the oxide from water, and that consequently a part of the 20 per cent. loss is water. I dissolved 3 grains of palladium in a small excess of nitro-muriatic acid and obtained 240 grain measures of nitrous gas; the same quantity was obtained a second time, and to the solution (slightly acid) were added by degrees 200 measures of oxymuriatic acid gas; after agitation no smell was perceived, but by increasing the quantity of gas a permanent smell of oxymuriatic acid was produced, and when 200 more had been added the smell was sensible for some days in an open jar, a presumption that no higher oxide is to be obtained. Now 240 nitrous gas = .32 of a grain, corresponding to .28 of oxygen, and 200 oxymuriatic acid = .64 of a grain, corresponding to .15 oxygen; the sum of the two portions of oxygen = .43, which must have combined with 3 grains of palladium; if .43 ∶ 4 ∷ 7 ∶ 50 nearly. Or 100 metal combine with 14 oxygen, as determined by Berzelius. I find the sulphuret to accord with this determination; and by carefully saturating the excess of acid in the nitro-muriate of palladium and then finding the quantity of lime water necessary to precipitate a certain weight of palladium, as well as the quantity of test muriatic acid necessary to dissolve the precipitated oxide, I am confirmed in the opinion that the atom of palladium must weigh 50 nearly, and its oxide 57, which there is every reason to believe is the protoxide. 6, 7, _and_ 8. _Oxides of Rhodium, Iridium, and Osmium._ Nothing certain has yet been determined respecting the oxygenation of these very rare metals. 9. _Oxides of Copper._ There are two oxides of copper according to the results of Proust, Chenevix, Berzelius and others, the proportions of which are given nearly the same by all, and so as to leave no reasonable doubt concerning their accuracy. 1. _Protoxide._ This oxide is _orange_, and contains 12½ oxygen on 100 copper: it is obtained by precipitating a portion of copper from the solution of any cupreous salt, by means of iron, then mixing this copper with a rather greater portion of the deutoxide and triturating them well. This being done, the mixture is to be dissolved in muriatic acid, and the orange oxide may then be precipitated by an alkali.