Examination for Thorina—or Thoria.

Owing to the scarcity of Thorite, an opportunity has not been afforded of examining a specimen for Thorina before the Blowpipe. The following is the humid method given by BERZELIUS :

:

The finely powdered mineral is digested with hydrochloric acid; when the whole mass, with disengagement of chlorine, becomes yellow and gelatinous, and must be evaporated to dryness in a water bath. The dried mass is then to be treated with water, filtered, and sulphide of hydrogen passed through the liquid, by which some sulphides of lead and tin are thrown down. It is again filtered, the thorina precipitated with caustic ammonia, the precipitate filtered and edulcorated. It is now rendered impure only by the oxides of iron, manganese, and uranium. To free it from these, the precipitate is to be dissolved, while still moist, in dilute sulphuric acid, and the solution evaporated until very little of it remains. During the evaporation, a white slightly cohering soft mass is deposited in abundance; this is neutral sulphate of thorina. It has the curious property of being very slightly soluble in hot, particularly so in boiling water. The acid is then decanted off, the white salt thrown on a filter and edulcorated from the adhering mother liquor, dried, and strongly ignited, by which the earth is obtained pure and white. The decanted acid liquor, and the water of edulcoration, as they contain more thorina, are then to be evaporated to a small bulk, saturated with carbonate of potassa, and mixed with a boiling saturated solution of sulphate of potassa. On cooling, the excess of sulphate of potassa, with a double salt of sulphate of thorina and potassa, which is perfectly insoluble in a saturated solution of the former salt, crystallize out of the liquid. It is then washed with a solution of sulphate of potassa, dissolved in warm water, and precipitated with ammonia. The precipitate yields, on ignition, an earth slightly tinged yellow by a trace of manganese, which may be purified by treating it as in the first method. It is obtained perfectly isolated only after ignition.

B. EXAMINATION OF METALS AND THEIR OXIDES.

§ 1. CERIUM-Ce-LANTHANIUM-La-and DIDYMIUM-D -Presence in the Mineral Kingdom.

Cerium belongs to the rare metals, and is found in the following minerals, nearly always in company with more or less Lanthanium and Didymium :

a. With Fluorine, in neutral Fluoride of Cerium from Broddbo, Ce Fl mixed with Ce2 Fl3, besides Yttria and Water; in basic Fluoride of Cerium from Finbo [Ce2 Fl3 + 3 Ce2 03, H 0]; in Fluoride of Cerium from Rytterhyttan [ (Ce2 Fl3 + 3 H 0) + Ce2 O3, H0]; in Fluoride of Cerium with Fluoride of Yttrium from Finbo, Ce Fl, Y Fl, mixed with Silicic Acid; in Yttro-Cerite with Yttria and Lime;

b. In combination with Phosphoric Acid, in Cryptolite 3 Ce 0, P 05 together with a little oxide of Iron; in Monazitoid with Lanthanium, Lime, and Water; in Monazite with a mixture of Lime, Magnesia, and Binoxide of Tin;

c. As Protoxide with Carbonic Acid, in Carbonate of Cerium [Ce O, C 0]; in Parisite with Lanthanium, Didymium, Lime, et cetera ;

d. As Protoxide in Titanic Acid combinations, namely, with Lime, Thorina, Protoxides of Uranium, Iron, and Manganese, in Pyrochlore; and with Zirconia, Yttria, Lime, Protoxides of Manganese and Iron, and other bases, in Polymignite;

e. As Protoxide, in Silicious combinations, namely:-Singly, in Cerite [3 Ce 0, Si O2 + 3 aq]; with Protoxide of Iron, Lime, and Alumina, in Cerine and Allanite; with Yttria and Protoxide of Iron, in Gadolinite; with Protoxide of Iron, Yttria, Lime, Protoxide of Manganese, and Water, in Orthite; and with Yttria, Protoxides of Iron and Manganese, Alumina, Lime, together with a little Carbon and Water, in Pyrorthite. It is also found in Aeschynite, Fergusonite, Euxenite, Polykras, Bodenite, Tschewkinite, Mosandrite, and Tritomite.

Examination for Cerium, Lanthanium, and Didymium.

In minerals, in which no other coloring matter, or at most only traces of such exist, besides protoxide of cerium, as in Fluoride of Cerium, Yttro-Cerite, Carbonate of Cerium, and Cerite, the cerium is readily detected with fluxes. Red or dark yellow beads are obtained with borax and microcosmic salt in the oxidating flame, according as a large or small quantity has been dissolved, and the mineral contains a large or a small proportion of protoxide of cerium; these beads, on cooling, and also when subjected to the reducing flame, lose their color to such a degree, that the bead of microcosmic salt becomes perfectly colorless. If the mineral contains a slight trace of iron, the borax bead becomes greenish in the reducing flame.

Protoxide of cerium cannot be recognized in this way, in such minerals as contain at the same time protoxide of iron, uranium, or titanic acid, as, for instance, Pyrochlore, Polymignite, Cerine, Allanite, Gadolinite, Orthite, and Pyrorthite. The operator succeeds better with such minerals, by melting them in a finely powdered state, with from six to eight times their bulk of bisulphate of potassa, dissolving the fused mass in a large quantity of water, and boiling the solution for some time, in order to precipitate titanic acid, if the mineral contains any. If the substance contains a large quantity of titanic acid, and at the same time zirconia, and protoxide of iron, the titanic acid, with the zirconia, and a part of the protoxide of iron, remain behind. If the precipitation of the titanic acid takes place, it is to be separated by filtration, and the protoxide of cerium thrown down from the filtered solution, in the manner described at page 144; or, in a far shorter way, as follows :—

First, the fluid is boiled for a short time in a test tube; if it remains clear, the whole of the titanic acid has been separated; when this is the case, a crystal of sulphate of potassa, rather more than sufficient to saturate the liquid, must be suspended in it, and the whole heated anew. If the solution contains protoxide of cerium, it falls of a white color, as a double salt of sul

phate of potassa and cerium, as soon as the solution becomes saturated with the sulphate of potassa. This occurs even when the quantity of cerium present is exceedingly small, the solution at first being only slightly turbid, but subsequently, on allowing the vessel to stand undisturbed for some time, the undissolved portion of the sulphate of potassa becomes covered with a white light friable powder. If the mineral contains zirconia, without titanic acid, it will be thrown down along with the cerium double salt, as basic sulphate of zirconia and potassa, unless, in the commencement, care be taken to remove it from the aqueous solution of the fused mass. Thorina, in case it is present, will also be thrown down with the cerium. When lime is present in the mineral, a portion of it is dissolved in the treatment of the fused mass with water, as sulphate of lime, and is also separated by the sulphate of potassa. The resulting precipitate should therefore, after separation by filtration, be well edulcorated, and tested for cerium with borax; the double salt is by this means decomposed, the sulphuric acid and potassa separate as sulphate of potassa, and flow down the platinum wire, if the end with the loop be held higher than the other. The borax bead remains clear, provided it is not saturated, and by it a very small trace of oxide of cerium may be recognized, by the color given at page 90, Table II.

Before the Blowpipe the oxide of lanthanium behaves in the following manner :-It does not fuse with soda, which is absorbed by the charcoal, leaving the oxide behind as a dirty white mass. Borax dissolves it in considerable quantity. The bead is perfectly colorless, both while hot and after cooling, and it is only when it has been saturated to excess with oxide of lanthanium that the bead appears on cooling of a light rose color, which is rendered. perceptible by holding it against a white ground; flaming will not cause its opacity.

When the bead appears, while hot, of a yellow color, it is a sign that the oxide of lanthanium still contains oxide of cerium, in which case it may also be rendered opaque by flaming. Its behavior with microcosmic salt is as with borax.

In the year 1839, MOSANDER found that the oxide of cerium, which up to that time was supposed to contain only one metal, was

mixed with another, which he called Lanthanium, a name derived from the Greek word synonymous with lying concealed. In another research upon the oxide of cerium in 1842, he found that there was a third oxide in the compound, and he called the metal of this oxide Didymium, from the Greek meaning twins.

For separating the oxide of cerium from the oxide of lanthanium, MOSANDER has given two methods. According to one, the heated oxides are treated with dilute nitric acid, containing one part of acid to fifty parts of water, by which the oxide of lanthanium is dissolved, leaving the oxide of cerium nearly pure. By the other method, the mixed oxides are to be dissolved in hydrochloric acid, and potassa in excess added to the solution, which throws down the hydrated oxides; this precipitate is filtered off, suspended in caustic potassa in an appropriate flask or beaker, and chlorine gas transmitted through the menstruum, by which means the oxide of lanthanium is dissolved, while the oxide of cerium remains in the form of a heavy yellow or yellowish-red powder. If the whole of the oxide of cerium be not separated by this treatment, the operation of adding hydrochloric acid, followed by precipitation with caustic potassa, and the transmission of chlorine through the liquor holding the precipitate in suspension, must be repeated as above till the whole is removed.

Impure oxide of cerium is dissolved by sulphuric acid diluted with its weight of water; the solution is then mixed with fifty parts of pure water, and the liquid made to boil. During ebullition the solution becomes opaque, and deposits a sulphur-yellow precipitate which is perfectly pure basic sulphate of cerium. All the oxide of lanthanium which was mixed with the oxide of cerium, remains in the solution, which also contains a large quantity of the latter element. To obtain the last portions of the oxide of cerium, caustic soda is added to the acid liquor, and the precipitate which it occasions filtered off, washed, and dissolved in nitric acid, the solution evaporated, and the residuary salt ignited, after which the oxide of lanthanium is dissolved out by nitric acid. The residual oxide of cerium is then treated with sulphuric acid, and the solution diluted and boiled as above, when a precipitate of basic sulphate of cerium falls.