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8. Bromide of Sodium-Na Br.

When heated in a test tube, with bisulphate of potassa, or strong sulphuric acid, this salt affords yellowish brown vapors of bromine.

9. Sulphate of Magnesia-Mg O, S 03+7 aq.

The constituents of this salt are recognized in the same manner as those of alum.

In a bulb tube, it yields a large quantity of water, which does not react acid.

It is infusible with soda on platinum foil; the base, therefore, appears to be an alkaline earth.

The anhydrous salt, held with the forceps in the blue flame, tinges the outer flame, sometimes feebly, but evidently yellow, from an admixture of soda.

Solution of cobalt communicates to it a beautiful, but feeble rose tint. The base is consequently magnesia.

When the mass is fused with soda, on charcoal, in the reducing flame, it produces, when laid on silver foil and moistened with water, a black stain of sulphide of silver. It gives, with soda and silicic acid, the peculiar hepatic tint. The acid is, therefore, sulphuric, and the salt consists of sulphate of magnesia, which is sometimes contaminated with a little sulphate of soda.

10. Chloride of Lithium-Li Cl.

This salt imparts a reddish color to the Blowpipe flame.

11. Celestine.

Celestine decrepitates strongly, when heated in a bulb tube, but yields no water. The test with soda on platinum foil may be dispensed with, as this substance is instantly recognized as an earthy salt. It should be proved, however, whether it tinges the outer flame. A fragment held in the forceps, and treated with

the point of the blue flame, fuses, and communicates a reddish tint to the exterior flame. The color, which is much clearer than that given by a salt of lime, is similar to that produced by lithia, but not so beautiful. This shows the presence, therefore, of lithia or strontia.

A specimen is next treated with soda on charcoal, in order to ascertain if it is absorbed with the flux by the support. It fuses with it, the compound undergoes a strong ebullition, and sinks into the charcoal, as a strong hepatic mass. By this means it is at once determined, that the salt is either sulphate of baryta, or sulphate of strontia; but as it has been already found to tinge the outer flame red, and also that it is not very difficultly fusible, it may be considered as almost certain that it is not Heavy Spar, but Celestine.

If a specimen be ignited for a long time, on charcoal, in the reducing flame, the sulphide of strontium so formed treated with hydrochloric acid, and the resulting salt evaporated to dryness, and moistened with spirit,-as has been already more fully given under the head of Examination for Strontia,-the presence of strontia is recognized with certainty, by the red color of the alcoholic flame.

12. Calcareous Spar.

This salt is readily recognized from its external character. The method of procedure is similar to the foregoing.

Heated in a bulb tube it does not yield water.

Held in the forceps, and strongly heated in the apex of the blue flame, it does not melt, but appears luminous, and tinges the outer flame a feeble carmine-red. During the refrigeration, it generally becomes of a blackish-green color, which shows the presence of iron or manganese.

The ignited fragment, when moistened, and laid upon litmus paper, reacts alkaline.

From this behavior, the conclusion may be drawn, that the substance under examination is an alkaline earth, and this earth, lime, in combination with carbonic acid.

A fragment, next, should be dissolved on the platinum wire, with borax, to ascertain if it effervesces or not during solution, and to notice the color communicated to the borax glass. Calcareous Spar dissolves with effervescence, the carbonic acid escaping, and the glass has generally a feeble iron tinge. If a larger proportion be dissolved, the glass crystallizes during the refrigeration, presenting a number of sharp edges. By this means, it has now been discovered that the salt is a carbonate, containing a little oxide of iron, and that the base apparently is lime. A separate test for manganese determines whether the salt under investigation may not probably contain this metal also.

When a portion is treated with soda on charcoal, it is not dissolved; the soda is absorbed by the charcoal, and an infusible mass remains, which may be considered as lime.

13. Pseudo Apatite.

This mineral occasionally occurs in a locality not far from Freiberg, on the sides of small lodes, accompanying various silver ores, particularly dark Ruby Silver, and also with Iron Pyrites, in druses on gangues, as an apparently changed natural product, of an hexagonal prismatic form, and a color partly yellowish-white, partly reddish-yellow; its fracture is almost earthy.

Many of the crystals, particularly the dark colored, when ignited in a bulb tube, decrepitate, and yield a small quantity of water only.

The fragments remaining in the bulb tube vitrify on the edges only, when intensely heated at the apex of the blue flame,— strongly phosphorescing at the same time, and when cold appearing of a lighter color. During the heating, the exterior flame is colored deeply yellow, from the presence of soda; with careful observation, however a dark green tinge may be evidently observed, shewing the presence of phosphoric acid. If the fragment held in the forceps be moistened with sulphuric acid, and then heated, the green tinge of the exterior flame becomes more decided, and notwithstanding the yellow color of the soda, may be recognized

as the reaction of phosphoric acid. It yields a regulus of phosphide of iron, with boracic acid and iron.

From the preceding investigation, it may be seen that the salt is a phosphate. Its behavior to vitreous fluxes and cobalt solution should now be examined, in order to be able to come to a conclusion as to the remaining constituents, particularly the bases.

This mineral dissolves slowly in borax forming a glass, which sometimes becomes streaked with opalescent lines, when a moderate quantity of the mineral is present; with a still larger quantity, the glass becomes turbid during refrigeration. The reddishyellow crystals give with borax a yellowish tinge, from oxide of iron.

It readily dissolves, with a slight effervescence, in microcosmic salt, and yields a glass colored by oxide of iron, which becomes turbidly streaked only when a large quantity of the substance is added; when nearly saturated, it becomes, per se, during refrigeration, turbid, and exhibits imperfect facets. When perfectly saturated, an almost milk white bead is obtained.

With an equal weight of soda, the powdered mineral fuses on charcoal to a bead, which, under a continued blast, becomes infusible, and loses its orbicular form. A larger addition of soda is absorbed by the charcoal. If another portion of the powdered mineral be fused with soda on charcoal in the reducing flame, and the fused mass laid on a moistened silver plate, a black stain of sulphide of silver is produced.

When fused with soda and saltpetre on a platinum foil, it gives no reaction; manganese is, therefore, absent.

Cobalt solution communicates a grey color to the powdered mineral.

From the behavior to borax, microcosmic salt, soda, and solution of cobalt, it can be seen that the mineral contains phosphoric, and also carbonic acid; because it dissolves in microcosmic salt with effervescence; and sulphuric acid, because, when fused with soda, it blackens silver. It may also be seen that the coloring ingredient is oxide of iron, and that the base is not alumina, as it gives a grey color, instead of a blue, with solution of cobalt.

If these Blowpipe reactions be compared with those of other combinations of phosphoric acid which occur in nature, it will be found that they resemble most those of Apatite.

We know, however, that apatite is a combination of phosphate of lime and chloride of calcium; the latter being often replaced by fluoride of calcium. It is therefore necessary that the mineral should be directly examined for chlorine, hydrofluoric acid, lime, and other bases.

As we have already seen, under Examination for Chlorine, no certain reaction for this element can be produced in the dry way. If however, it be treated with nitric acid, it readily dissolves, with effervescence; if this solution be diluted with distilled water, it will be rendered slightly turbid on the addition of nitrate of silver; consequently, it is not perfectly free from chlorine.

When fused in a glass tube, closed at one end, with an equal quantity of bisulphate of potassa, faint marks are produced on the surface of the glass, at a small distance from the mixture, which remain when the closed end is cut off, the tube washed with water, and dried. The mineral must, therefore contain hydrofluoric acid.

The test for lime and other earths must be performed with the help of the moist way. It may, however, be considered nearly certain, that the principal constituent is lime, as the mineral forms during refrigeration, when fused with microcosmic salt, imperfect facets; an admixture of other earths can only be detected, however, by recourse to the moist way.

For this purpose, a small portion must be treated with hydrochloric acid, and the earths precipitated as described under Lime, and more especially under Apatite. The mineral readily dissolves with the production of heat and evolution of gas,--with the escape of carbonic acid; the solution, when diluted with water and spirit of wine, gives, with dilute sulphuric acid, an evident precipitate, which affords the reaction of gypsum before the Blowpipe, after being edulcorated; the solution, filtered from the gypsum, gives, with ammonia, a slight gelatinous precipitate, which, on further examination, behaves as ferruginous alumina.

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