gave, instead of the white chloride of niobium, the purest yellow pelopic acid, and this could always afterwards be obtained, but only by following strictly certain rules of manipulation and precaution. By the observation of a modified method, the white chloride could be obtained from the same acid.

From the preparation of both these chlorides, Rose concludes that the same metal is contained in them as is contained in the acids prepared from them by means of water. But these acids once formed cannot be converted into one another like their corresponding chlorides, or only by a very circuitous process.

The quantity of oxygen has not, up to the present time, been determined directly, but the yellow chloride of pelopium contains more chlorine than the white chloride of niobium, hence pelopic acid must contain more oxygen than niobic.

Niobic acid cannot, however, be converted into pelopic, even by the most powerful oxidizing agents; neither does this result ensue by either direct or indirect oxidation. The behavior of the two acids before the Blowpipe also varies considerably. Such a relation is so peculiar, that there is no analogy to it in the whole domain of Chemistry.

It appears, nevertheless, that by some, but only few, reducing means, from the acid analogous to the yellow chloride, a little oxygen could be removed.

The proportion of oxygen in both acids, as deduced from that of the chlorine in the chloride, is a very anomalous one, and only in the two degrees of oxidation of sulphur, is a similar case found.

It is still doubtful whether a small proportion of oxygen is not contained in the carefully prepared white chloride, which may therefore be regarded as an acid salt; but the quantity of oxygen, according to the most exact investigation, is so extremely small that it is hoped the chloride will be obtained perfectly free from it. As, under all circumstances, pelopic and niobic acids are oxides of the same metal, these substances must only have one appellation. ROSE has selected that of niobium. The highest state of oxidation of this metal, formerly pelopic, must thus be called niobic acid.

§ 22. TITANIUM-Ti-Presence in the Mineral Kingdom, and in the products of Smelting Furnaces.

It is found as an Acid [Ti O2] per se, and also in combination with bases, thus:

a. Per se, in Anatase, Arkansite, Brookite, and Rutile; the latter generally contains some Protoxides of Iron and Manganese; -Arkansite, according to the examination of WHITNEY, is pure titanic acid, with only a trace of iron, and not a niobate, as inferred by SHEPHARD, and has the crystalline form and specific gravity of Brookite. His trials make the specific gravity 4.085. Its insolubility in acids is strong presumptive proof that it is not titanic acid in combination with a base, since all the known titanates are soluble in acids;

Brookite Prismatic Titanic Ore-occurs in crystals of a hairbrown color, passing into deep orange-yellow, more or less translucent; streak yellowish-white; lustre brilliant, metallic adamantine. Insoluble and indecomposable in boiling hydrochloric acid, even when reduced to powder. Alone on charcoal it is infusible, but it is entirely soluble, and forms a brownish-yellow glass, with microcosmic salt. This species occurs with Anatase and Crichtonite, at Bourg d'Oisans, in Dauphiné, on the Tête-noire, in Savoy, and in large distinct crystals in Snowdon, in Wales. It is, however, a rare mineral;

b. In combination with Earths and Metallic Oxides; as with Lime and Silicate of Lime, in Titanite and Sphene; with Lime, Protoxides of Cerium, Uranium, Iron, Manganese, Tin, et cetera, in Pyrochlore; with Zirconia, Yttria, Oxides of Cerium, Iron, Calcium, and traces of Potassa, Magnesia, Silicic Acid, and Oxide of Tin, in Polymignite; with Protoxide of Iron, in many rich slags, exempli gratia, in Titaneisen, Crichtonite, Menaccanite, Nigrin, Iserine, Ilmenite, Volcanic Iron, Eisensand; and in all refractory Iron Ores whose slags are of a vitreous nature;

c. As a very small ingredient in some minerals, it is found in Cymophane, Kyanite, Achmite, and in some varieties of Mica.Titanium occurs likewise in Perowskite, Polykras, Aeschynite,

Euxenite, Yttrotitanite, Oerstedtite, Tschewknite, and Mosandrite.

When Titantiferous Iron Ores are smelted, the Titanium sometimes separates in the metallic state, and is observed upon the slags in small copper red crystals. It has been seen in beautiful perfect cubes upon a slag obtained from the smelting works near Frankfort-on-the-Maine.

Examination for Titanium.

The titanium contained in Anatase, Rutile, Titanite, and Sphene, can be detected by the behavior of these minerals with fluxes; id est, the first two comport themselves with borax, microcosmic salt, and soda, like titanic acid, the other two afford only the titaniferous color with microcosmic salt. In other minerals, where titanium forms an ingredient, it is somewhat difficult to detect it by the aid of the fluxes, as the other metallic oxides in combination hinder the reaction. If, however, ferruginous titanium ore be dissolved in microcosmic salt, and the glass, which exhibits the color of sesquioxide of iron only, treated for a long time in the reducing flame, a more or less brownish-red tinge is imparted to the assay, similar to that produced by ferruginous tungstic acid. The intrinsic quantity of titanium present, is deduced from the depth of color assumed by the glass. If the quantity present be great, the characteristic reaction of oxide of titanium-titanic oxide-will be obtained by treating with tin in microcosmic salt upon charcoal; but if only a small portion be present, this end is not attainable. Titanium, when forming an essential or appreciable ingredient in minerals, may be detected by a very simple method, as follows :-Fuse gradually the finely pulverized mineral in a platinum spoon, with from six to eight times its volume of bisulphate of potassa; dissolve out in hot water,-temperature about 200-8° Fahr. 93.8° C.,-and allow the solution to subside; decant off the clear supernatant liquor into a flask containing more hot water, and boil. If the mineral contained even small quantities of titanium, it will be deposited as a white powder,-titanic acid,-provided iron is not present in the state.

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of protoxide, otherwise it will have a yellow tinge, probably from holding some of the iron in combination. This precipitate is to be separated by filtration, and examined, without being edulcorated, with microcosmic salt, either on a platinum wire or charcoal. If the quantity be so small that no violet color is imparted to the microcosmic salt, the operator must add to the assay, treated on the wire, a small quantity of sesquioxide of iron, and when heated on charcoal, a piece of iron wire, and then heat the glass for some time in the reducing flame; it will appear, while hot yellow, and upon cooling red, analogous to oxide of nickel, or ferruginous tungstic acid. This reaction is produced immediately by the yellow precipitate, when heated with microcosmic salt. in the reducing flame.

When such a precipitate is dissolved in borax, the iron has no effect upon the color produced by the titanic acid.

Should the operator not be perfectly convinced of the absence of tungstic acid, the method with bisulphate of potassa will be the most decisive for the detection of the titanium, as the titanic acid is precipitated on boiling the solution,-and any tungstic acid remains dissolved, and can then be treated with microcosmic. salt, as previously given.

If Polymignite be smelted with even ten times its volume of bisulphate of potassa, and the fused mass treated with warm water, little or no titanic acid is dissolved; it remains behind, with zirconia and traces of protoxide of iron, as a white voluminous mass, and can readily be recognized by collecting on a filter, and then treating some of the precipitate with microcosmic salt. The metallic titanium found in ferruginous slags dissolves with difficulty in borax, but is pretty readily soluble in microcosmic salt. The crystals which the German author applied in this research had been examined under the lens and considered as pure, but the yellow microcosmic salt glass was, in the reducing flame, neither per se, nor with the addition of tin, of a fine violet color, but somewhat reddish, like the ferruginous titanic acid.

§ 23. CHROMIUM-Cr-Presence in the Mineral Kingdom.

Chromium occurs only in an oxidized state in nature, thus :— a. As Oxide [Cr2 O3] in a mechanical mixture with Quartz and various kinds of primitive rocks, in Oxide of Chrome, or Chrome Ochre; as Oxide, with Protoxide of Iron, Alumina, and Magnesia, in Chromate of Iron-Chrome Iron Ore

Fe O

Ore-[ Mg of +

b. As Chromic Acid [Cr 03] with Lead, in Chromate of Lead, and with Lead and Oxide of Copper in Vauquelinite. In addition to these, Oxide of Chromium and Chromic Acid form an extraneous ingredient in many Silicious combinations, to which many of them owe their beautiful green or blood-red color; as the precious Emerald, the Pyrope, et cetera.

Traces of Chromic Acid are present in Schiller Spar, and in some varieties of Serpentine. Chromium is also met with in Ilmenite, Wolchonskoite, Uwarowite, Pyrosklerite, Miloschine, Spinele, Chrysoberyle, Rothbleierz, and Melanochroite.

Examination for Chromium.

The presence of chromium in most of the above minerals is readily detected by their behavior with borax and microcosmic salt before the Blowpipe, the bead being of a beautiful green when perfectly cold. This color is produced by minerals which contain neither lead nor copper, particularly after treatment in the reducing flame. When the minerals contain oxides of lead or of copper, exempli gratia, Chromate of Lead and Vauquelinite, the glass bead affords, in the reducing flame, a grey or red color, the peculiar green of the Chromium being completely destroyed; in consequence of this, attention should be paid, in the examination of such minerals, to those colors only which they produce in the oxidating flame.

Minerals which contain little chromium, and a large quantity of other metals that yield coloring oxides, and afford no satisfactory chrome reaction with borax and microcosmic salt, can be