Both Vauquelin[16] and Hisinger[17] agree that the protocarbonate of cerium, when exposed to a red heat, yields 57 or 58 oxide, which the former says is the red oxide, being changed by the calcination. Hisinger finds the percarbonate to consist of 36.2 acid and 63.8 oxide: also that the muriate of cerium consists of 100 acid and 197.5 oxide; but Vauquelin remarks that the sulphate, nitrate, and muriate of cerium are always more or less acid, however dried; and he found the protoxalate of cerium to yield 45.6 red oxide by calcination, on a mean of 3 experiments not much differing from each other. Supposing all these facts accurate, they may be reconciled by a few suppositions by no means improbable. Let the atom of cerium be 22, the protoxide 29, and the red oxide 32½ (that is, 1 oxy. + 2 protox. = 65); and let the protocarbonate be 1 atom of acid, 1 of oxide, and 1 of water; the percarbonate, 1 acid 1 oxide; the oxalate, 1 acid (40) and 1 oxide; and the muriate, saturated with base, 3 oxide and 2 acid. Then it will be found that, [Footnote 16: An. de Chimie, 54--28] [Footnote 17: An. of Philos.--4--356] The decomposed protocarbonate will yield 57.5 red oxide; The decomposed percarbonate will yield, 36.7 acid, 63.3 oxide; The decomposed oxalate will yield 47 red oxide; and The muriate will yield 100 acid (22), and 197.7 oxide. All of which agree very nearly with the results above obtained. Hence it appears to me very probable that the several atoms of the metal and the oxides are as stated above; and that, 100 cerium + 31.8 oxygen = 131.8 protoxide, white. ---------- + 47.7 ------ = 147.7 intermediate, red. Hisinsger, from some of the same data united to other hypothetical facts than those assumed above, deduces the two oxides very different; viz. 100 metal + 17.4 oxygen for the protoxide, and 100 + 26.1 for the peroxide. SECTION 14. EARTHY, ALKALINE AND METALLIC SULPHURETS.