27. Oxides of titanium.
Nothing certain is known respecting the oxides of titanium. An observation of Richter, quoted by Berzelius (An. of Philos. 3—251), if it could be relied upon, furnishes an important fact, namely, that a solution of muriate of titanium containing 84.4 oxide, gave 150 muriate of silver. Now 150 muriate of silver contain 28 acid; hence 28 acid must have combined with 84.4 oxide; but if 28 ∶ 84.4 ∷ 22 ∶ 66 nearly for the weight of an atom of the oxide. This would indicate 59 for an atom of the metal.
28. Oxides of columbium.
The white oxide or acid of columbium is found in combination with the oxides of iron and manganese in proportion nearly as 4 of the acid to 1 of the aggregate oxides. The two minerals, columbite and tantalite, though yielding these substances nearly in the same proportions, are found to differ remarkably in specific gravity, the former being about 5.9 and the latter about 7.9. Dr. Wollaston concludes however, from the agreement of the white oxides extracted, that they must be the same. The white oxide of columbium is insoluble in the mineral acids; it unites with potash by fusion, and may be precipitated by most acids. Some of the vegetable acids, the oxalic, the tartaric, and the citric dissolve the white oxide. When the alkaline solution of columbium previously neutralized by an acid is treated with infusion of galls, an orange precipitate is produced which is characteristic of columbium. Nothing certain has been determined respecting the proportions of metal and oxygen; but from the great proportion of the columbic acid found with the oxides of iron and manganese, together with the great sp. gravity of the compound, one may pretty clearly infer the great weight of the atom of columbium. Supposing the white oxide or acid to consist of 1 atom metal + 3 oxygen and that the columbite is formed by 1 atom of acid to 1 of oxide, we should have 128 acid + 32 oxide. This would give 107 for the weight of an atom of metal, and 128 for that of the tritoxide or columbic acid; but it is unnecessary to dwell upon such conjectures.
In a recent memoir of Messrs. Gahn, Berzelius, and Eggertz (An. de Chimie, Octo. 1816), it is maintained as probable that there is only one oxide of columbium or tantalum, and that 100 metal take 5.485 oxygen, or 121 metal take 7 oxygen. If this be correct, the atom of columbium must be 121 and the protoxide 128.
(See also An. de Chimie, 43—271; Philos. Trans. 1802; Nichols. Journ. 2—129; ibid. 3—251; ibid. 25—23).
29. Oxides of cerium.
The mineral cerite is of the sp. gr. 4.53, and constituted of 50 or 60 per cent. of oxide of cerium, with silex, lime, and iron. This mineral being calcined and dissolved in nitro-muriatic acid, the solution is to be neutralized by caustic potash, and then treated with tartrate of potash. The precipitate, well washed and afterwards calcined, is pure oxide of cerium. This oxide, which is white, when calcined in the open air becomes red and acquires more oxygen. These oxides, particularly the white, are soluble in most acids; the red oxide with muriatic acid gives oxymuriatic acid.
The experiments hitherto made on this subject scarcely enable us to decide respecting the proportions of metal and oxygen, nor the relative weights of these oxides.
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,