When alcohol is poured over powdered soda compounds and lighted, the flame exhibits a reddish-yellow color, particularly if the alcohol is stirred up with a glass rod, or if the alcohol is nearly consumed.

Fused upon charcoal, soda compounds are absorbed by the coal. The sulphide, chloride, iodide, and bromide of soda yield a white sublimate around the spot where the substance is laid, but this sublimate is not so copious as that of the potash compounds, and disappears when touched with the reduction flame, communicating a yellow color to the external flame. The presence of soda in compounds must likewise be confined by reactions in the wet way.

(c.) Ammonia (NH^{4}O).—In the fused state, and at the usual temperature, ammonia is a pungent gas, and exerts a reaction upon litmus paper similar to potash and soda. Ammonium is considered by chemists as a metal, from the nature of its behavior with other substances. It has not been isolated, but its existence is now generally conceded by all chemists. The ammonia salts are volatile, and many of them sublimate without being decomposed.

The salts of ammonia, on being heated in the point of the blue flame, produce a feeble green color in the external flame, just previous to their being converted into vapor. But this color is scarcely visible, and presents nothing characteristic. When the ammonia salts are mixed with the carbonate of soda, and heated in a glass tube closed at one end, carbonate of ammonia is sublimed, which can be readily recognized by its penetrating smell of spirits of hartshorn.

This sublimate will render blue a slip of red litmus paper. This can be easily done by moistening the litmus paper, and then inserting the end of it in the tube. By holding a glass rod, moistened with dilute hydrochloric acid, over the mouth of the tube, a white vapor is instantly rendered visible (sal ammoniac).

(d.) Lithia (LiO).—In the pure state, lithia is white and crystalline, not easily soluble in water, and does not absorb moisture. It changes red litmus to blue, and at a low red heat it melts. Lithia or its salts, exposed to the point of the blue flame, communicates a red color to the external or oxidation flame, in consequence of a reduction, sublimation, and re-oxidation of the lithia. An admixture of potash communicates to this flame a reddish-violet color, and the presence of soda that of a yellowish-red or orange. If the soda, however, is in too great proportion, then its intense yellow hides the red of the lithia. In the latter case the substance under test must be only imperfectly fused in the oxidation flame, and then dipped in wax or tallow. By exposing it now to the reduction flame, the red color imparted to the external flame by the lithia becomes visible, even if a considerable quantity of soda be present. A particular phenomenon appears with the phosphate of lithia, viz., the phosphoric acid itself possesses the property of communicating to the flame a bluish-green color. By its combination with lithia it still exhibits its characteristic color, while the latter presents likewise its peculiar tint. Then we perceive a green flame in the centre of the flame, while the red color of lithia surrounds it.

The silicates, which contain only a little lithia, produce only a slight hue in the flame, and often none at all. We have to mix one part of the silicate with two parts of a mixture composed of one part of fluorspar and one and a half parts of bisulphate of potassa. Moisten the mass with water so that the mass will adhere, and then melt it upon a platinum wire in the reduction flame, when that of oxidation will present the red color of lithia.

The Borates of lithia produce at first a green color, but it soon yields to the red of lithia. When alcohol is poured over lithia or its compounds, and inflamed, it burns with a deep red color, particularly if the fluid is stirred up with a glass rod, or when the alcohol is nearly consumed. This color presents the same modifications as the corresponding ones communicated to the blowpipe as mentioned above.

The salts of lithia are absorbed by charcoal when fused upon it. The sulphide, bromide, iodide, and chloride of lithia produce upon the charcoal a greyish-white sublimate, although not so copiously as the corresponding compounds of potash and soda. This sublimate disappears when touched by the reduction flame, while the oxidation flame gives the characteristic color of lithia.

SECOND GROUP.—THE ALKALINE EARTHS, BARYTA, STRONTIA, LIME, AND MAGNESIA.

In the pure state, the alkaline earths are caustic, cause red litmus paper to become blue, and are more or less soluble in water. Their sulphides are also soluble. The carbonates and phosphates of the alkaline earths are insoluble in water. By igniting the carbonates, their carbonic acid is expelled, and the alkaline earths are left in the caustic state. The alkaline earths are not volatile, and their organic salts are converted, by ignition, into carbonates.

(a.) Baryta. (BaO).—This alkaline earth does not occur free in nature, but combined with acids, particularly with carbonic and sulphuric acids. In the pure state, baryta is of a greyish-white color, presents an earthy appearance, and is easily powdered. When sparingly moistened with water, it slakes, becomes heated, and forms a dry, white powder. With still more water it forms a crystalline mass, the hydrate of baryta, which is completely soluble in hot water. Pure baryta is infusible; the hydrate fuses at a red heat, without the loss of its hydratic water; if caustic baryta is exposed for too great a length of time to the flame, it absorbs water, originated by the combustion, and becomes a hydrate, when it will melt. Salts of baryta, formed with most acids, are insoluble in water; for instance, the salts with sulphuric, carbonic, arsenic, phosphoric, and boracic acids. The salts of baryta, soluble in water, are decomposed by ignition, except the chloride.

Carbonate of baryta loses its carbonic acid at a red heat, becomes caustic, and colors red litmus paper blue.

By exposing baryta or its compounds upon a platinum wire, or a splinter of the substance held with the platinum tongs, to the point of the blue flame, a pale apple-green color is communicated to the external flame. This color appears at first very pale, but soon becomes more intense. This color is most visible if the substance is operated with in small quantities. The chloride of barium produces the deepest color. This color is less intense if the carbonate or sulphate is used. The presence of strontia, lime, or magnesia, does not suppress the reaction of the baryta, unless they greatly predominate.

When alcohol is poured over baryta or its salts, and inflamed, a feeble green color is communicated to the flame, but this color should not be considered a characteristic of the salt.

Baryta and its compounds give, when fused with carbonate of soda upon platinum foil, a clear bead. Fused with soda upon charcoal, it is absorbed. The sulphate fuses at first to a clear bead, which soon spreads, and is absorbed and converted while boiling into a hepatic mass. If this mass is taken out, placed upon a piece of polished silver and moistened with a little water, a black spot of sulphide of silver is left after washing off the mass with water.

Borax dissolves baryta and its compounds with a hissing noise, as well in the flame of oxidation as in that of reduction. There is formed a clear bead which, with a certain degree of saturation, is clear when cold, but appears milk-white when overcharged, and of an opal, enamel appearance, when heated intermittingly, or with a vacillating flame, that changes frequently from the oxidating to the reducing flame. Baryta and its compounds produce the same reactions with microcosmic salt.

Baryta and its compounds fuse when exposed to ignition in the oxidizing flame. Moistened with the solution of nitrate of cobalt, and heated in the oxidation flame, it presents a bead, colored from brick-red to brown, according to the quantity used. This color disappears when cold, and the bead falls to a pale grey powder after being exposed awhile to the air. When heated again, the color does not appear until fusion is effected. If carbonate of soda is fused upon platinum wire with so much of the sesquioxide of manganese that a green bead is produced, this bead, when fused with a sufficient quantity of baryta, or its compounds, after cooling, will appear of a bluish-green, or light blue color.

(b.) Strontia (SrO).—Strontia and its compounds are analogous to the respective ones of baryta. The hydrate of strontia has the same properties as the hydrate of baryta, except that it is less soluble in water. The carbonate of strontia fuses a little at a red heat, swells, and bubbles up like cauliflower. This produces, in the blowpipe flame, an intense and splendid light, and now produces an alkaline reaction upon red litmus paper. The sulphate of strontia melts in the oxidation flame upon platinum foil, or upon charcoal, to a milk-white globule. This fuses upon charcoal, spreads and is reduced to the sulphide, which is absorbed by the charcoal. It now produces the same reactions upon polished silver as the sulphate of baryta under the same conditions. By exposing strontia and its compounds upon platinum wire, or as a splinter with the platinum tongs, to the point of the blue flame, the external flame appears of an intense crimson color. The deepest red color is produced by the chloride of strontium, particularly at the first moment of applying the heat. After the salt is fused, the red color ceases to be visible in the flame, by which it is distinguished from the chloride of lithium. The carbonate of strontia swells up and produces a splendid white light, while the external flame is colored of a fine purple-red. The color produced by the sulphate of strontia is less intense. The presence of baryta destroys the reaction of the strontia, the flame presenting the light green color of the baryta.

If alcohol is poured over powdered strontia and inflamed, the flame appears purple or deep crimson, particularly if the fluid is stirred with a glass rod, and when the alcohol is nearly consumed.

The insoluble salts of strontia do not produce a very intense color. Baryta does not prevent the reaction of the soluble salts of strontia, unless it exists greatly in excess. In the presence of baryta, strontia can be detected by the following process: mix some of the substance under examination with some pure graphite and water, by grinding in an agate mortar. Place the mixture upon charcoal, and expose it for a while to the reduction flame. The substance becomes reduced to sulphide of barium and sulphide of strontium, when it should be dissolved in hydrochloric acid. The solution should be evaporated to dryness, redissolved in a little water, and enough alcohol added that a spirit of 80 per cent. is produced. Inflame the spirit, and if strontia is present, the flame is tinged of a red color. This color can be discerned more distinctly by moistening some cotton with this spirit and inflaming it.

If strontia or its compounds are fused with a green bead of carbonate of soda and sesquioxide of manganese, as described under the head of baryta, a bead of a brown, brownish-green, or dark grey color is produced. Carbonate of soda does not dissolve pure strontia. The carbonate and sulphate of strontia melt with soda upon platinum foil to a bead, which is milk-white when cold, but fused upon charcoal they are absorbed. Strontia or its compounds produce with borax, or microcosmic salt, the same reactions as baryta. When they are moistened with nitrate of cobalt, and ignited in the oxidizing flame, a black, or grey infusible mass is produced.

(c.) Lime, Oxide of Calcium (CaO).—Lime does not occur free in nature, but in combination with acids, chiefly the carbonic and sulphuric. The phosphate occurs principally in bones. The hydrate and the salts of lime are in their properties similar to those of the two preceding alkaline earths. In the pure state, the oxide of calcium is white; it slakes, produces a high temperature, and falls into a white powder when sprinkled with a little water. It is now a hydrate, and has greatly increased in volume. The hydrate of lime is far less soluble in water than either those of baryta or strontia, and is less soluble in hot water than in cold. Lime, its hydrate and sulphide of calcium, have a strong alkaline reaction upon red litmus paper. Lime and its hydrate are infusible, but produce at a strong red heat a very intense and splendid white light, while the hydrate loses its water. The carbonate of lime is also infusible, but at a red heat the carbonic acid is expelled, and the residue becomes caustic, appears whiter, and produces an intenser light. The sulphate of lime melts with difficulty, and presents the appearance of an enamelled mass when cold. By heating it upon charcoal it fuses in the reducing flame, and is reduced to a sulphide. This has a strong hepatic odor, and exerts an alkaline reaction upon red litmus paper. By exposing lime, or its compounds, upon platinum wire—or as a small splinter of the mineral in the platinum tongs—to the point of the blue flame, a purple color, similar to that of lithia and strontia, is communicated to the external flame, but this color is not so intense as that produced by strontia, and appears mixed with a slight tinge of yellow. This color is most intense with the chloride of calcium, while the carbonate of lime produces at first a yellowish color, which becomes red, after the expulsion of the carbonic acid. Sulphate of lime produces the same color, but not so intense. Among the silicates of lime only the tablespar (3CaO, 2SiO^{3}) produces a red color. Fluorspar (CaFl) produces a red as intense as pure lime, and fuses into a bead. Phosphate and borate of lime produce a green flame which is only characteristic of their acids. The presence of baryta communicates a green color to the flame. The presence of soda produces only a yellow color in the external flame.

If alcohol is poured over lime or its compounds and inflamed, a red color is communicated to the flame. The presence of baryta or soda prevents this reaction. Lime and its compounds do not dissolve much by fusion with carbonate of soda. If this fusion is effected on charcoal, the carbonate of soda is absorbed and the lime remains as a half-globular infusible mass on the charcoal. This is what distinguishes lime from baryta and strontia, and is a good method of separating the former from the latter. Lime and its compounds fuse with borax in the oxidizing and reducing flames to a clear bead, which remains clear when cold, but when overcharged with an excess or heated intermittingly, the bead appears, when cold, crystalline and uneven, and is not so milk-white as the bead of baryta or strontia, produced under the same circumstances. The carbonate of lime is dissolved with a peculiar hissing noise. Microcosmic salt dissolves a large quantity of lime into a clear bead, which is milky when cold. When the bead has been overcharged with lime, by a less excess, or by an intermittent flame, we will perceive in the bead, when cold, fine crystals in the form of needles. Lime and its compounds form by ignition with nitrate of cobalt, a black or greyish-black infusible mass.

(d.) Magnesia (MgO).—Magnesia occurs in nature in several minerals. It exists in considerable quantity combined with carbonic, sulphuric, phosphoric, and silicic acids, etc. Magnesia and its hydrate are white and very voluminous, scarcely soluble in hot or cold water, and restores moistened red litmus paper to its original blue color. Magnesia and its hydrate are infusible, the latter losing its water by ignition. The carbonate of magnesia is infusible, loses its carbonic acid at a red heat, and shrinks a little. It now exerts upon red litmus paper an alkaline reaction. The sulphate of magnesia, at a red heat, loses its water and sulphuric acid, is entirely infusible, and gives now an alkaline reaction. The artificial Astrachanit (NaO, SO^{3} + MgO, SO^{3} + 4HO) fuses easily. When fused on charcoal, the greater part of the sulphate of soda is absorbed, and there remains an infusible mass.

Magnesia and its compounds do not produce any color in the external flame, when heated in the point of the blue flame. The most of the magnesia minerals yield some water when heated in a glass tube closed at one end.

Magnesia, in the pure state, or as the hydrate, does not fuse with soda. Some of its compounds are infusible likewise with soda, and swell up slightly, while others of them melt with soda to a slightly opaque mass. Some few (such as the borate of magnesia) give a clear bead with soda, though it becomes slightly turbid by cooling when saturated with magnesia, and crystallizes in large facets.

Magnesia and its compounds give beads with borax and microcosmic salt similar to those of lime. By igniting magnesia or its compounds very strongly in the oxidizing flame, moistening with nitrate of cobalt, and re-igniting in the oxidation flame, they present, after a continued blowing, a pale flesh-color, which is more visible when cold. It is indispensable that the magnesia compounds should be completely white and free of colored substances, or the color referred to cannot be discerned. In general the reactions of magnesia before the blowpipe are not sufficient, and it will be necessary to confirm its presence or absence by aid of reagents applied in the wet way.

THIRD GROUP.—THE EARTHS, ALUMINA, GLUCINA, YTTRIA, THORINA, AND ZIRCONIA.

The substances of this group are distinguished from the preceding by their insolubility in water, in their pure or hydrated state—that they have no alkaline reaction upon litmus paper, nor form salts with carbonic acid. The earths are not volatile, and, in the pure state, are infusible. They cannot be reduced to the metallic state before the blowpipe. The organic salts are destroyed by ignition, while the earths are left in the pure state, mixed with charcoal, from the organic acids. The most of their neutral salts are insoluble in water; the soluble neutral salts change blue litmus paper to red, and lose their acids when ignited.

(a.) Alumina (Al^{2}O^{3}).—This earth is one of our most common minerals. It occurs free in nature in many minerals, as sapphire, etc.; or in combination with sulphuric acid, phosphoric acid, and fluorine, and chiefly silicates. Pure alumina is a white crystalline powder, or yellowish-white, and amorphous when produced by drying the hydrate, separated chemically from its salts. Alumina is quite unalterable in the fire; the hydrate, however, losing its water at a low red heat. The neutral salts of alumina, with most acids, are insoluble in water. Those soluble in it have an acid reaction upon litmus paper, changing the blue into red.

The sulphates of alumina eliminate water when heated in a glass tube closed at one end. By ignition, sulphurous acid (SO^{2}) is given off, which can be recognized by its smell, and by its acid reaction upon blue litmus paper, when a small strip of it moistened is brought within the orifice of the tube; an infusible residue is left in the tube.

The greater part of the alumina compounds give off water with heat; the most of them are also infusible, except a few phosphates and silicates.

Pure alumina does not fuse with carbonate of soda. The sulphates, when exposed upon charcoal with soda to the reducing flame, leave a hepatic residue. The phosphates melt with a little soda, with a hissing noise, to a semi-transparent mass, but they are infusible with the addition of soda, and give only a tough mass. This is the case, likewise, with the silicates of alumina. Fluoride of aluminium melts with carbonate of soda to a clear bead, spreads by cooling, and appears then milk-white. Borax dissolves the alumina compounds slowly in the oxidizing and reducing flames to a clear bead, which is also clear when cold, or heated intermittingly with a vacillating flame. The bead is turbid, as well in the heat as the cold, when an excess of alumina is present. When the alumina compound is added to excess in the powdered form, the bead appears crystalline upon cooling, and melts again with great difficulty.

Alumina and its compounds are slowly dissolved in the microcosmic salt to a bead, clear in both flames, and when hot or cold. When alumina is added to excess, the undissolved portion appears semi-transparent. Alumina melts with bisulphate of potash into a mass soluble in water. When the powdered alumina compounds are strongly ignited in the oxidizing flame, then moistened with nitrate of cobalt, and re-ignited in the oxidizing flame, an infusible mass is left, which appears, when cooled, of an intense blue color. The presence of colored metallic oxides, in considerable quantity, will alter or suppress this reaction. The silicates of the alkalies produce, in a very strong heat, or continued heat, with nitrate of cobalt, a pale blue color. The blue color produced by alumina is only distinctly visible by daylight; by candle-light it appears of a dirty violet color.

(b.) Glucina. (G^{2}O^{3}).—Glucina only occurs in a few rare minerals, in combination with silica and alumina. It is white and insoluble in the pure state, and its properties generally are similar to those of alumina. The most of its compounds are infusible, and yield water by distillation. Carbonate of soda does not dissolve glucina by ignition. Silicate of glucina melts with carbonate of soda to a colorless globule. Borax and microcosmic salt dissolve glucina and its compounds to a colorless bead which, when overcharged with glucina, or heated with the intermittent flame appears, after cooling, turbid or milk-white. Glucina yields, by ignition with nitrate of cobalt, a black, or dark grey infusible mass.

(c.) Yttria (YO) occurs only in a few rare minerals, and usually in company with terbium and erbium. Its reactions before the blowpipe are similar to the preceding, but for its detection in compounds it will be necessary to resort to analysis in the wet way.

(d.) Zirconia (Zr^{2}O^{3}).—This substance resembles alumina in appearance, though it occurs only in a few rare minerals. It is in the pure state infusible, and at a red heat produces such a splendid and vivid white light that the eyes can scarcely endure it. Its other reactions before the blowpipe are analogous to glucina. Microcosmic salt does not dissolve so much zirconia as glucina, and is more prone to give a turbid bead. Zirconia yields with nitrate of cobalt, when ignited, an infusible black mass. To recognize zirconia in compounds we must resort to fluid analysis.

(e.) Thorina (ThO).—This is the rarest among the rare minerals. In the pure state it is white and infusible, and will not melt with the carbonate of soda. Borax dissolves thorina slowly to a colorless, transparent bead, which will remain so when heated with the intermittent flame. If overcharged with the thorina, the bead presents, on cooling, a milky hue. Microcosmic salt dissolves the thorina very tardily. By ignition with nitrate of cobalt, thorina is converted into an infusible black mass,

CLASS II.

FOURTH GROUP. CERIUM, LANTHANIUM, DIDYMIUM, COLUMBIUM, NIOBIUM, PELOPIUM, TITANIUM, URANIUM, VANADIUM, CHROMIUM, MANGANESE.

The substances of this group cannot be reduced to the metallic state, neither by heating them per se, nor by fusing them with reagents. They give by fusion with borax or microcosmic salt, colored beads, while the preceding groups give colorless beads.

(a.) Cerium (Ce).—This metal occurs in the oxidated state in a few rare minerals, and is associated with lanthanium and didymium, combined with fluorine, phosphoric acid, carbonic acid, silica, etc. When reduced artificially, it forms a grey metallic powder.

(a.) Protoxide of Cerium (CeO).—It exists in the pure state as the hydrate, and is of a white color. It soon oxidizes and becomes yellow, when placed in contact with the air. When heated in the oxidation flame, it is converted into the sesquioxide, and then is changed into light brick-red color. In the oxidation flame it is dissolved by borax into a clear bead, which appears of an orange or red while hot, but becomes yellow upon cooling. When highly saturated with the metal, or when heated with a fluctuating flame, the bead appears enamelled as when cold. In the reduction flame it is dissolved by borax to a clear yellow bead, which is colorless when cold. If too much of the metal exists in the bead, it then appears enamelled when cooled.

Microcosmic salt dissolves it, in the oxidation flame, to a clear bead, which is colored dark yellow or orange, but loses its color when cold. In the reduction flame the bead is colorless when either hot or cold. Even if highly saturated with the metal, the bead remains colorless when cold. By fusing it with carbonate of soda upon charcoal in the reduction flame, the soda is absorbed by the charcoal, while the protoxide of the metal remains as a light grey powder.

(B.) Sesquioxide of Cerium (Ce^{2}O^{3}).—This oxide, in the pure state, is a red powder. When heated with hydrochloric acid, it produces chlorine gas, and is dissolved to a salt of the protoxide. It is not affected by either the flame of oxidation or of reduction; when fused with borax or microcosmic salt, it acts like the protoxide. It does not fuse with soda upon charcoal. In the reduction flame it is reduced to the protoxide, which remains of a light grey color, while the soda is absorbed by the charcoal.

(b.) Lanthanium (La.)—This metal is invariably associated with cerium. It presents, in its metallic state, a dark grey powder, which by compression acquires the metallic lustre.

The oxide of lanthanium (LaO) is white, and its salts are colorless. Heated upon charcoal, it does not change either in the oxidation flame or that of reduction. With borax, in the flame of oxidation or reduction, it gives a clear colorless bead. This bead, if saturated, and when hot, presents a yellow appearance, but is clouded or enamelled when cold. With microcosmic salt the same appearance is indicated. It does not fuse with carbonate of soda, but the soda is absorbed by the charcoal, while the oxide remains of a grey color.

(c.) Didymium (D).—This metal occurs only in combination with the preceding ones, and it is therefore, like them, a rare one.

Oxide of Didymium (DO).—This oxide is of a brown color, while its salts present a reddish-violet or amethyst color. The oxide is infusible in the oxidation flame, and in that of reduction it loses its brown color and changes to grey. With borax in the oxidation flame, it fuses to a clear dark red or violet bead, which retains its clearness when highly saturated with the oxide, or if heated with a fluctuating flame.

The reactions with microcosmic salt are the same as with borax.

It does not melt with carbonate of soda upon charcoal, but the oxide remains with a grey color, while the soda is absorbed by the charcoal.

(d.) Columbium, (Tantalum—Ta).—This rare metal occurs quite sparingly in the minerals tantalite, yttrotantalite, etc., as columbic acid. In the metallic state, it presents the appearance of a black powder, which, when compressed, exhibits the metallic lustre. When heated in the air it is oxidized into columbic acid, and is only soluble in hydrofluoric acid, yielding hydrogen. It is oxidized by fusion with carbonate of soda or potash.

Columbic Acid (Ta^{2}O^{3}) is a white powder, and is infusible. When heated in the flame of oxidation or reduction, it appears of a light yellow while hot, but becomes colorless when cold. With borax, in the flames of oxidation and reduction, it fuses to a clear bead, which appears by a certain degree of saturation, of a yellow color so long as it continues hot, but becomes colorless when cold. If overcharged, or heated with an intermittent flame, it presents an enamel white when cool.

It melts with microcosmic salt quite readily in both of the flames, to a clear bead, which appears, if a considerable quantity of columbic acid be present, of a yellow color while hot, but colorless when cold, and does not become clouded if the intermittent flame be applied to it.

With carbonate of soda it fuses with effervescence to a bead which spreads over the charcoal. Melted with more soda, it becomes absorbed by the charcoal.

It yields, moistened with a solution of nitrate of cobalt, and exposed to the oxidation flame after continued blowing, an infusible mass, presenting while hot a light grey color, but after being cooled that of a light red, similar to the color presented by magnesia under the same circumstances. But if there be some alkali mixed with it, a fusion at the edges will be manifest, and it will yield by cooling a bluish-black mass.

(e.) Niobium (Ni).—This metal occurs as niobic acid in columbite (tantalite). Niobic acid is in its properties similar to columbic acid. It is white and infusible. By heating it either in the flames of reduction or oxidation, it presents as long as it continues hot, a greenish-yellow color, but becomes white when cool. Borax dissolves it in the oxidation flame quite readily to a clear bead, which, with a considerable quantity of niobic acid, is yellow when hot, but transparent and colorless when cold. A saturated bead is clear when either hot or cold, but becomes opaque when heated intermittingly.

In the flame of reduction, borax is capable of dissolving more of the niobic acid, so that a bead overcharged and opaque in the oxidation flame appears quite clear when heated in the flame of reduction. A bead overcharged in the flame of reduction, appears by cooling dim and bluish-grey.

Microcosmic salt dissolves in the flame of oxidation a great quantity of it to a clear bead, which is yellow while hot, but colorless when cold.

In the flame of reduction, and in presence of a considerable quantity of niobic acid, the bead appears while hot of a light dirty blue color, and when cold, of a violet hue; but by the addition of more niobic acid, the bead, when hot, is of a dirty dark blue color, and when cold, of a transparent blue. In the presence of the oxides of iron, the bead is, while hot, of a brownish-red color, but changing when cool to a dark yellow.

This acid fuses with an equal quantity of carbonate of soda upon charcoal, to a bead which spreads very quickly, and is then infusible. When fused with still more soda, it is absorbed.

When moistened with nitrate of cobalt, and heated in the flame of oxidation, it yields an infusible mass which appears grey when hot, and dirty green when cold; but if the heat has been too strong, it is fused a little at the edges, which present a dark bluish-grey color.

Pelopium (Pe).—This metal occurs as an acid in the mineral columbite (tantalite), and is very similar to the two preceding metals.

(f.) Pelopic Acid (PeO^{3}).—This acid is white, and appears yellow when heated, but resumes its white color when cold. Borax dissolves it in the oxidation flame to a clear colorless bead, which appears, when overcharged and heated intermittingly, enamel-white when cold. This is likewise the case in the flame of reduction, but when overcharged the color is light grey, when the bead is cooled.

Microcosmic salt dissolves it in the flame of oxidation, to a clear yellow bead, which loses its color when cold. In the reduction flame, when the bead is highly saturated, a violet-brown color is produced. In presence of the oxides of iron, the reactions are like those of niobic acid. With carbonate of soda, the reactions are similar to those of niobic acid. By heating with nitrate of cobalt, it yields a light grey infusible mass.

(g.) Titanium (Ti).—This metal occurs occasionally in the slags of iron works, in the metallic state, as small cubical crystals of a red color. It is a very hard metal, and very infusible. Titanic acid occurs in nature crystallized in anatase, arkansite, brookite, and rutile. Titanium is harder than agate, entirely infusible, and loses only a little of its lustre, which can be regained by fusion with borax. It does not melt with carbonate of soda, borax, or microcosmic salt, and is insoluble in every acid except the hydrofluoric. By ignition with saltpetre it is converted into titanic acid, which combines with the potassium, forming the titanate of potassium.

Titanic Acid (TiO^{2}) is white, insoluble, and, when heated, it appears yellow while hot, but resumes upon cooling its white color.

Borax dissolves it in the oxidation flame to a clear yellow bead, which when cool is colorless. When overcharged, or heated with the intermitting flame, it is enamel-white after being cooled. In the reduction flame, the bead appears yellow, if the acid exists in small quantity, but if more be added, then it is of an orange, or dark yellow, or even brown. The saturated bead, when heated intermittingly, appears when cold of an enamelled blue. By addition of the acid, and by heating the bead on charcoal in the reduction flame, it becomes dark yellow while hot, but dark blue, or black and opaque when cold. This bead appears, when heated intermittingly, of a light blue, and when cold, enamelled.

Microcosmic salt fuses with it in the oxidation flame to a clear colorless bead, which appears yellow only in the presence of a quantity of titanic acid, though by cooling it loses its color. In the reduction flame this bead exhibits a yellow color when hot, but is red while cooling, and when cold of a beautiful bluish-violet. If the bead is overcharged, the color becomes so dark that the bead appears opaque, though not presenting an enamel appearance. By heating the bead again in the oxidation flame the color disappears. The addition of some tin promotes the reduction. If the titanic acid contains oxide of iron, or if some is added, the bead appears, when cold, brownish-yellow, or brownish-red.

By fusion with carbonate of soda, titanic acid is dissolved with effervescence to a clear dark yellow bead, which crystallizes by cooling, whereby so much heat is eliminated, that the bead, at the instant of its crystallization, glows with great brightness. A reduction to a metal cannot, however, be effected. By ignition with a solution of nitrate of cobalt in the oxidation flame, it yields an infusible yellowish-green mass.

(h.) Uranium (U).—This rare metal occurs in the form of protoxide along with other oxides, in the mineral pitch-blende; as peroxide in uranite and uran-mica, associated with phosphoric acid and lime.

In the metallic state it presents the appearance of a dark grey mass, which is infusible, and remains unchanged when under water, or when exposed to dry air, but, when heated in the oxidation flame, it becomes oxidized, with lively sparkling, to a dark green mass, composed of the protoxide and peroxide.

The protoxide of uranium (UO) is black, uncrystalline, or forms a brown powder. When exposed to heat it is converted partially into peroxide, when it has a dark green color.

The peroxide of uranium (U^{2}O^{3}) is of an orange color, while its hydrate is of a fine yellow color, and in the form of a powder. The salts are yellow.

By heating it in the oxidation flame, it acquires a dark green color, and is partly reduced to protoxide. In the reduction flame it presents a black appearance, and is there completely reduced to protoxide.

Borax dissolves it in the oxidation flame to a clear dark yellow bead, which is colorless when cold, if the metal is not present in great quantity. If more of the metal, or peroxide, be added, the bead changes to orange when hot, and light yellow when cold. When heated with the intermittent flame, it requires a large quantity of the peroxide to produce an enamel appearance in the cooled bead.

In the flame of reduction the bead becomes of a dirty green color, being partly reduced to protoxide, and appears, with a certain degree of saturation, black, when heated intermittingly, but never enamelled. The bead appears on charcoal, and with the addition of tin, of a dark green color.

It fuses with microcosmic salt in the oxidation flame to a clear yellow bead, which is greenish-yellow when cold. In the reduction flame it produces a beautiful green bead, which increases when cold.

When fused upon charcoal with the addition of tin, its color is darker. Carbonate of soda does not dissolve it, although with a very small portion of soda it gives indications of fusion, but with still more of the soda it forms a yellow, or light-brown mass, which is absorbed by the charcoal, but it is not reduced to the metallic state.

(i.) Vanadium (V).—This very rare mineral is found in small quantity in iron-ores, in Sweden, and as vanadic acid in a few rare minerals. The metal presents the appearance of an iron-grey powder, and sometimes that of a silver-white mass. It is not oxidized either by air or water, and is infusible.

Vanadic Acid (VO^{3}) fuses upon platinum foil to a deep orange liquid, which becomes crystalline after cooling. When fused upon charcoal, one part of it is absorbed, while the rest remains upon the charcoal and is reduced to protoxide similar in appearance to graphite.

A small portion of it fuses with borax in the oxidation flame to a clear colorless bead, which appears, with the addition of more vanadic acid, of a yellow color, but changes to green when cold.

In the reduction flame the bead is brown while hot, but changes, upon cooling, to a beautiful sapphire-green. At the moment of crystallization, and at a degree of heat by which at daylight no glowing of the heated mass is visible it begins to glow again. The glow spreads from the periphery to the centre of the mass, and is caused by the heat liberated by the sudden crystallization of the mass. It now exhibits an orange color, and is composed of needle crystals in a compact mass.

Microcosmic salt and vanadic acid fuse in the oxidation flame to a dark yellow bead which, upon cooling, loses much of its color.

In the reduction flame the bead is brown while hot, but, upon cooling, acquires a beautiful green color.

Vanadic acid fuses with carbonate of soda upon charcoal, and is absorbed.

(k.) Chromium (Cr) occurs in the metallic state only in a very small quantity in meteoric iron, but is frequently found in union with oxygen, as oxide in chrome iron ore, and as chromic acid in some lead ores.

In the metallic state it is of a light grey color, with but little metallic lustre, very hard, and not very fusible. Acids do not act upon it, except the hydrofluoric; fused with nitre, it forms chromate of potassa. It is unaltered in the blowpipe flame.

Sesquioxide of Chromium (Cr^{2}O^{3}).—This oxide forms black crystals of great hardness, and is sometimes seen as a green powder. Its hydrate (Cr^{2}O^{3} + 6HO) is of a bluish-grey color. It forms with acids two classes of isomeric salts, some of which are of a green color, and the others violet-red or amethyst. The neutral and soluble salts have an acid reaction upon blue litmus paper, and are decomposed by ignition.

Sesquioxide of chromium in the oxidation and reduction flames is unchangable. When exposed to heat, the hydrate loses its water, and gives a peculiarly beautiful flame. In the oxidation flame borax dissolves the sesquioxide of chromium slowly to a yellow bead (chromic acid) which is yellowish green when cold. Upon the addition of more of the oxide, the bead is dark red while hot, but changes to green as it becomes cold.

In the reduction flame the bead is of a beautiful green color, both while hot and when cold. It is here distinguished from vanadic acid, which gives a brownish or yellow bead while hot.

With microcosmic salt it fuses in the oxidation flame to a clear yellow bead, which appears, as it cools, of a dirty-green, color, but upon being cool is of a fine green color. If there be a superabundance of the oxide, so that the microcosmic salt cannot dissolve it, the bead swells up, and is converted into a foamy mass, in consequence of the development of gases.

In the reduction flame it fuses to a fine green bead. The addition of a little tin renders the green still deeper.

Sesquioxide of chromium fuses with carbonate of soda upon platinum foil to a brown or yellow bead, which, upon cooling, appears of a lighter color and transparent (chromate of sodium).

When fused with soda upon charcoal, the soda is absorbed, and the green oxide is left upon it, but is never reduced to the metallic state.

Chromic Acid (CrO^{3}) crystallizes in the form of deep ruby red needles. It is decomposed into sesquioxide and oxygen when heated. This decomposition is attended with a very lively emission of light, but this is not the case if the chromic acid has been attained by the cooeperation of an aqueous solution, unless the reduction is effected in the vapor of ammonia. Before the blowpipe chromic acid produces the same reactions as the sesquioxide.

(l.) Manganese (Mn).—This metal occurs in considerable abundance, principally as oxides, less frequently as salts, and sometimes in combination with sulphur and arsenic. It is found in plants, and passes with them into the animal body. In the metallic state, it is found frequently in cast iron and steel. It is a hard, brittle metal, fusible with difficulty, and of a light grey color. It tarnishes upon exposure to the air and under water, and falls into a powder.

Protoxide of Manganese exists as a green powder; as hydrate separated by caustic alkalies, it is white, but oxidizes very speedily upon exposure to the air. The protoxide is the base of the salts of manganese. These salts, which are soluble in water, are decomposed when heated in the presence of the air—except the sulphate (MnO, SO^{3}), but if the latter is exposed to ignition for awhile, it then ceases to be soluble in water, or at least only sparingly so.

Sesquioxide of Manganese (Mn^{2}O^{3}) Occurs very sparingly in nature as small black crystals (Braunite) which give, when ground, a brown powder. When prepared by chemical process, it is in the form of a black powder. The hydrate occurs sometimes in nature as black crystals (manganite). By digestion with acids, it is dissolved into salts of the protoxide. With hydrochloric acid, it yields chlorine.

The prot-sesquioxide of manganese (MnO + Mn^{2}O^{3}) occurs sometimes in black crystals (hausmannite). Prepared artificially, it is in the form of a brown powder.

Peroxide of Manganese (MnO^{2}) occurs in considerable abundance as a soft black amorphous mass, or crystallized as pyrolusite, also reniform and fibrous. It is deprived of a part of its oxygen when exposed to ignition. It eliminates a considerable quantity of chlorine from hydrochloric acid, and is thereby converted into chloride of manganese (ClMn).

Most of the manganese compounds which occur in nature yield water when heated in a glass tube closed at one end. The sesquioxide and peroxide give out oxygen when strongly heated, which can be readily detected by the increased glow which it causes, if a piece of lighted wood or paper is brought to the mouth of the tube. The residue left in the tube is a brown mass (MnO + Mn^{2}O^{3}).

When exposed to ignition with free access of air, all manganese oxides are converted into (MnO + Mn^{2}O^{3}), but without fusion. Such, at least, is the statement of some of the German chemists, although it will admit perhaps of further investigation.

Manganese oxides fuse with borax in the oxidation flame to a clear and intensely colored bead, of a violet hue while hot, but changing to red as it cools. If a considerable quantity of the oxide is added, the bead acquires a color so dark as to become opaque. If such be the case, we have to press it flat, by which its proper color will become manifest.

In the reduction flame the bead is colorless. A very dark colored bead must be fused upon charcoal with the addition of some tin. The bead must be cooled very suddenly, for if it cools too slowly, it then has time to oxidize again. This may be effected by pushing it off the platinum wire, or the charcoal, and pressing it flat with the forceps.

The oxides of manganese fuse with microcosmic salt in the oxidation flame, to a clear brownish-violet bead, which appears reddish-violet while cooling. This bead does not become opaque when overcharged with manganese. As long as it is kept in fusion a continued boiling or effervescence takes place, produced by the expulsion of oxygen, in consequence of the fact that the microcosmic salt cannot dissolve much sesquioxide, while the rest is reduced to protoxide, is re-oxidated, and instantly again reduced. If the manganese is present in such a minute quantity as not to perceptibly tinge the bead, the color may be made to appear by the contact of a crystal of nitre while hot. The bead foams up upon the addition of the nitre, and the foam appears, after cooling, of a rose-red or violet color. In the reduction flame the bead sometimes becomes colorless.

The oxides of manganese fuse with carbonate of soda upon platinum foil or wire, to a clear green bead, which appears bluish-green and partially opaque when cold (manganate of soda NaO + MnO^{3}). A very minute trace of manganese will produce this green color. The oxides of manganese cannot be reduced upon charcoal with carbonate of soda before the blowpipe. The soda is absorbed, and (MnO + Mn^{2}O^{3}) is left.

GROUP FIFTH.—IRON, COBALT, NICKEL.

The oxides of this group are reduced to the metallic state when fused with carbonate of soda upon charcoal in the reduction flame. Metals when thus reduced form powders, are not fusible or volatile in the blowpipe flame, but they are attracted by the magnet.

Furthermore, these oxides are not dissolved by carbonate of soda in the oxidation flame, but they produce colored beads with borax and microcosmic salt.

(a.) Iron.—It occurs in great abundance in nature. It is found in several places in America in the metallic state, and it likewise occurs in the same state in meteors. It occurs chiefly as the oxide (red hematite, brown hematite, magnetic oxide, etc.), and frequently in combination with sulphur. Iron also forms a constituent of the blood.

Metallic iron is of a grey color, and presents the metallic lustre vividly when polished. It is very ductile, malleable, and tenacious. It is very hard at common temperatures, but soft and yielding at a red heat.

In dry and cold air, iron does not oxidize, but when the air is dry and moist, it oxidizes rapidly. This likewise takes place with great rapidity when the metal is heated to redness. When submitted to a white heat iron burns with brilliant scintillations.

Protoxide of Iron (FeO).—This oxide does not occur pure in nature, but in union with the peroxide of iron and other substances. It presents the form of a black powder, and has some metallic lustre, is brittle, and fuses at a high temperature to a vitreous looking mass. It is attracted by the magnet, and of course is susceptible of becoming magnetic itself. It forms with water a hydrate, but this passes so rapidly into a state of higher oxidation, that it is difficult to keep it in the pure state.

Magnetic Oxide of Iron (FeO + Fe^{2}O^{3}).—This peculiar oxide is of a dark color, and is magnetic, so that tacks or small nails adhere to it when brought in contact with it. It is the variety of the oxide termed "loadstone." It is found frequently crystallized in octahedrons in Scandinavia and other places. Magnetic oxide of iron is produced when red-hot iron is hammered.

Sesquioxide of Iron (Fe^{2}O^{3}).—This oxide is found native in great abundance as red hematite and specular iron, crystallized in the rhombic form. In the crystalline state it is of a blackish-grey color, and possessed of the metallic lustre. When powdered, it forms a brownish-red mass. When artificially prepared, it presents the appearance of a blood-red powder. It is not magnetic, and has less affinity for acids than the protoxide. Its hydrate is found native as brown hematite.

By exposing the peroxide of iron to the oxidation flame, it is not acted upon, but in the reduction flame it becomes reduced to the magnetic oxide.

The oxides of iron are dissolved by borax in the oxidation flame to a clear dark-yellow or dark-red bead, which appears lighter while cooling, and yellowish when cold. In the presence of a very small quantity of iron, the bead appears colorless when cold. If the iron is increased, the bead is opaque while cooling, and of a dirty dark-yellow color when cold. In the reduction flame, and fused upon platinum wire, the bead appears dark green (FeO + Fe^{2}O^{3}). By the addition of some tin, and fused upon charcoal, the bead appears bluish-green, or not unlike that of sulphate of iron.

Microcosmic salt dissolves the oxides of iron in the oxidation flame to a clear bead, which, by the addition of a considerable quantity of iron, becomes of an orange color while hot, but gets lighter while cooling, presenting finally a greenish hue, and gradually becoming lighter, till, when cold, it is colorless. If the iron is increased, the hot bead presents a dark red color, but while cooling a brownish-red, which changes to a dirty-green, and, when cold, to a brownish-red color. The decrease of the color during the transition from the hot to the cold state is still greater in the bead formed by the microcosmic salt.

In the reduction flame no change is visible if the quantity of iron be small. By the addition of more iron, the hot bead appears red, and while cooling, changes to yellow, then green, and, when cold, is of a dull red. By fusing the bead on charcoal with a small addition of tin, it exhibits, while cooling, a bluish-green color, but, when cold, is colorless.

The oxides of iron are not dissolved in the oxidation flame by fusion with carbonate of soda. By ignition with soda upon charcoal in the reduction flame, they are absorbed and reduced to the metallic state. Cut out this portion of the charcoal; grind it with the addition of some water in an agate mortar, for the purpose of washing off the carbon particles, when the iron will remain as a grey magnetic powder.

(b.) Cobalt (Co) occurs in combination with arsenic and sulphur, and associated with nickel and iron. It is found occasionally in combination with selenium, and there are a traces of it in meteoric iron. In the metallic state it is of a light, reddish-grey color, rather brittle, and only fusible at a strong white heat; at common temperatures it is unalterable by air or water. At a red heat, it oxidizes slowly and decomposes water; at a white heat it burns with a red flame. Cobalt is soluble in dilute sulphuric or hydrochloric acid by the aid of heat, whereby hydrogen is eliminated. These solutions have a fine red color.

Protoxide of Cobalt (CoO).—It is an olive-green powder, but, by exposure to the air, it becomes gradually brown. Its hydrate is a rich red powder. The solution of its salts is red, but the aqueous solution is often blue.

When heated in the oxidation flame, the protoxide is converted into the black proto-sesquioxide (CoO + Co^{2}O^{3}). In the reduction flame it shrinks and is reduced without fusion to the metallic state. It is now attracted by the magnet and acquires lustre by compression.

Borax dissolves it in the oxidation flame, and produces a clear, intensely colored blue bead, which remains transparent and of the same beautiful blue when cold. This blue is likewise manifest even if the bead be heated intermittingly. If the cobalt exists in considerable quantity, the color of the bead is so intense as to appear almost black.

This reaction of cobalt is so characteristic and sensitive that it can detect a minute trace.

With microcosmic salt the same reaction is exhibited, but not so sensitive, nor is the bead so intensely colored when cold as that with borax.

By fusion with carbonate of soda upon a platinum wire, with a very small portion of cobalt, a bright red colored mass is produced which appears grey, or slightly green when cold. By fusion upon platinum foil the fused portion floats down from the sides, and the foil is coated around the undissolved part, with a thin, dark-red sublimate. When fused upon charcoal, and in the reduction flame, it is reduced with soda to a grey powder, which is attracted by the magnet, and exhibits the metallic lustre by compression.

Sesquioxide of Cobalt (Co^{2}O^{3}).—It is a dark brown powder. Its hydrate (2HO + Co^{2}O^{3}) is a brown powder. It is soluble only in acetic acid as the acetate of the sesquioxide. All other acids dissolve its salts to protoxide, the hydrochloric acid producing chloric gas. By ignition in the oxidation flame, it is converted into the proto-sesquioxide (CoO + Co^{2}O^{3}) and produces with reagents before the blowpipe the same reactions as the protoxide.

(c.) Nickel (Ni).—This metal occurs invariably associated with cobalt, and in analogous combinations, chiefly as the arsenical nickel. In the metallic state it is greyish, silver-white, has a high lustre, is hard, and malleable both cold and hot. At common temperatures, it is unalterable either in dry or moist air. When ignited, it tarnishes. It is easily dissolved by nitric acid, but very slowly by dilute sulphuric or hydrochloric acid, producing hydrogen.

Protoxide of Nickel (NiO).—It is in the form of small greyish-black octahedrons, or a dark, greenish-grey powder. Its hydrate is a green powder. Both are unalterable in the air, and are soluble in nitric, sulphuric, and hydrochloric acids, to a green liquid. The protoxide is the base of the salts of nickel, which in the anhydrous state are yellow, and when hydrated are green. The soluble neutral salts change blue litmus paper to red. By ignition in the oxidation flame, protoxide of nickel is unaltered. In the reduction flame and upon charcoal, it becomes reduced, and forms a grey adherent powder, which is infusible, and presents the metallic lustre by compression, and is magnetic. Borax dissolves it in the oxidation flame very readily to a clear bead, of a reddish-violet or dark yellow color, but yellow or light red when cold. If there is but a small quantity of the oxide present, it is colorless. If more of the oxide be present, the bead is opaque and dark brown, and appears, while cooling, transparent and dark red. By the addition of a salt of potassa (the nitrate or carbonate) a blue or a dark purple colored bead is produced. The borax bead, in the reduction flame, is grey, turbid, or completely opaque from the reduced metallic particles. After a continued blast, the bead becomes colorless, although the particles are not fused. If the nickel contains cobalt, it will now be visible with its peculiar blue color. Upon charcoal, and by the addition of some tin, the reduction of the oxide of nickel is easily effected, while the reduced nickel fuses with the tin.

The oxide of nickel is dissolved by microcosmic salt in the oxidation flame to a clear bead, which appears reddish while hot, but yellow and sometimes colorless when cooling. If a considerable quantity of nickel be present the heated bead is of a brown color, but orange when cooled. In the reduction flame, and upon platinum wire, the color of the bead is orange when cold; but upon charcoal, and with the addition of a little tin, the bead appears grey and opaque. After being submitted to the blowpipe flame all the nickel is reduced, and the bead becomes colorless.

Carbonate of soda does not affect it in the oxidation flame, but in the reduction flame and upon charcoal, it is absorbed and reduced, and remains, after washing off the carbon, as a white metallic powder, which is infusible, and has a greater attraction for the magnet than iron.

Sesquioxide of Nickel (Ni^{2}O^{3}).—It is in the form of a black powder, and does not combine with other substances, unless it is reduced to the protoxide. It exhibits before the blowpipe the same behavior as the protoxide.

GROUP SIXTH.—ZINC, CADMIUM, ANTIMONY, TELLURIUM.

The substances of this group can be reduced upon charcoal by fusion with carbonate of soda, but the reduced metals are volatilized, and cover the charcoal with sublimates.

(a.) Zinc (Zn).—This metal is found in considerable abundance, but never occurs in the pure metallic state, but in combination with other substances, chiefly as sulphide in zinc blende, as carbonate in calamine, and as the silicate in the kieselzinc ore; also, with sulphuric acid, the "vitriol of zinc."

Zinc is of a bluish-white color and metallic lustre, is crystalline and brittle when heated 400 deg.F., but malleable and ductile between 200 deg. and 300 deg.. It will not oxidize in dry air, but tarnishes if exposed to air containing moisture, first becomes grey, and then passes into the white carbonate. It decomposes in water at a glowing heat. It is dissolved by diluted acids, while hydrogen is eliminated. It melts at about 775 deg., and distills when exposed to a white heat in a close vessel. When heated over 1000 deg. in the open air, it takes fire, and burns with a bluish-white light, and with a thick white smoke of oxide of zinc.

Oxide of Zinc (ZnO).—In the pure state, oxide of zinc is a white powder, infusible, and not volatile. It is readily soluble in acids after being heated strongly. Its soluble neutral salts, when dissolved in water, change blue litmus paper to red. Its salts, with organic acids, are decomposed by ignition, and the carbonate of zinc remains.

The oxide of zinc turns yellow by being ignited in the oxidation flame, but it is only visible by daylight; this color changes to white when cold. It does not melt, but produces a strong light, and it is not volatile.

It disappears gradually in the flame of reduction, while a white smoke sublimates upon the charcoal. This sublimate is yellow while hot, but changes to white when cold. The cause of this is, that the oxide is reduced, is volatilized, and re-oxidized, by going through the external flame in the form of a metallic vapor.

Borax dissolves oxide of zinc in the flame of oxidation easily to a clear bead, which is yellow while hot, and colorless when cold. The bead becomes, by the addition of more oxide, enamelled, while cooling. If the bead is heated with the intermittent flame, it is milk-white when cold. When heated in the flame of reduction upon platinum wire, the bead at first appears opaque, and of a greyish color, but becomes clear again after a continued blast.

When heated upon charcoal in the reduction flame, it is reduced to a metal; but, at the same moment, is volatilized, and sublimes as oxide of zinc upon the charcoal, about one line's distance from the assay. This is likewise the case with the microcosmic salt, except that it is more easily volatilized in the reduction flame.

Carbonate of soda does not dissolve the oxide of zinc in the flame of oxidation. In the reduction flame and upon charcoal, the oxide of zinc is reduced to the metallic state, and is volatilized with a white vapor of the zinc oxide, which sublimes on the charcoal and exhibits a yellow color while hot, and which changes to white when cold. By a strong heat the reduced zinc burns with a white flame.

Moistened with a solution of cobalt oxide, and heated strongly in the flame of oxidation, zinc oxide becomes of a yellowish-green color while hot, and changes to a beautiful green color when cold.

(b.) Cadmium (Cd).—This is one of the rare metals. It occurs in combination with sulphur in greenockite, and in some ores of zinc. It was detected first in the year 1818, and presents itself as a tin-white metal of great lustre, and susceptible of a fine polish. It has a fibrous structure, crystallizes easily in regular octahedrons, presenting often the peculiar arborescent appearance of the fern. It is soft, but harder and more tenacious than tin; it can be bent, filed, and easily cut: it imparts to paper a color like that of lead. It is very malleable and ductile, and can be hammered into thin leaves. It is easily fused, and melts before it glows (450 deg.). At a temperature not much over the boiling point of mercury, it begins to boil, and distills, the vapor of the metal possessing no peculiar odor. It is unalterable in the air for a long time, but at length it tarnishes and presents a greyish-white, half metallic color. This metal easily takes fire when heated in the air, and burns with a brownish-yellow vapor, while it deposits a yellow sublimate upon surrounding bodies. It is easily soluble in acids with the escape of hydrogen, the solutions being colorless. Its salts, soluble in water, are decomposed by ignition in free air. Its soluble neutral salts change blue litmus paper to red. The salts, insoluble in water, are readily dissolved in acids.

Oxide of Cadmium (CdO).—This oxide is of a dark orange color. It does not melt, and is not volatile, not even at a very high temperature. Its hydrate is white, loses in the heat its hydratic water, and absorbs carbonic acid from the air when it is kept in open vessels.

Cadmium oxide is unaltered when exposed upon platinum wire in the flame of oxidation. When heated upon charcoal in the flame of reduction it disappears in a very short time, while the charcoal is coated with a dark orange or yellow powder, the color of which is more visible after it is cooled. The portions of this sublimate furthest from the assay present a visible iridescent appearance. This reaction of cadmium is so characteristic and sensitive that minerals (for instance, calamine, carbonate of zinc) which contains from one to five per cent. of carbonate of cadmium, will give a dark yellowish ring of cadmium oxide, a little distance from the assay, after being exposed for a few moments to the flame of reduction. This sublimate is more visible when cold, and is produced some time previous to the reduction of the zinc oxide. If a vapor of the latter should appear, it indicates that it has been exposed too great a length of time to the flame.

Borax dissolves a considerable quantity of cadmium oxide upon a platinum wire to a clear yellow bead, which, when cold, is almost colorless. If the bead is nearly saturated with the cadmium oxide, it appears milk-white when intermittingly heated. If the bead is completely saturated, it retains its opalescent appearance. Upon charcoal, and in the flame of reduction, the bead intumesces, the cadmium oxide becomes reduced to metal; this becomes volatilized and re-oxidized, and sublimes upon the charcoal as the yellow cadmium oxide.

In the oxidation flame, microcosmic salt dissolves a large quantity of it to a clear bead, which, when highly saturated and while hot, is yellowish colored, but colorless when cold. By complete saturation, the bead is enamel-white when cold.

Upon charcoal, in the flame of reduction, the bead is slowly and only partially reduced, a scanty sublimate being produced on the charcoal. The addition of tin promotes the reduction.

Carbonate of soda does not dissolve cadmium oxide in the oxidation flame. In the reduction flame, upon charcoal, it is reduced to metal, and is volatilized to a red-brown or dark, red sublimate of cadmium oxide upon the charcoal, at a little distance from the assay the charcoal presenting the characteristic iridescent appearance. This reaction is still more sensitive if the cadmium oxide is heated per se in the reduction flame.

Antimony (Sb).—This metal is found in almost every country. It principally occurs as the tersulphide (SbS^{3}), either pure or combined with other sulphides, particularly with basic sulphides. Sometimes it occurs as the pure metal, and rarer in a state of oxidation as an antimonious acid and as the oxysulphide.

In the pure state, antimony has a silver-white color, with much lustre, and presents a crystalline structure. The commercial and impure metal is of a tin-white color, and may frequently be split in parallel strata. It is brittle and easily pulverized. It melts at a low red heat (810 deg.), is volatilized at a white heat, and can be distilled. At common temperatures it is not affected by the air. At a glowing heat it takes fire, and burns with a white flame, and with white fumes, forming volatile antimonious acid. Common acids oxidize antimony, but dissolve it slightly. It is soluble in aqua regia (nitro-hydrochloric acid).

Sesquioxide of Antimony (Sb^{2}O^{3}).—In the pure state this oxide is a white powder, is fusible at a dull red heat to a yellow liquid, which, after cooling, is greyish-white and crystalline. If it is heated excluded from the air, it can be volatilized completely; it sublimes in bright crystals having the form of needles. It occurs sometimes in nature as white and very bright crystals. It takes fire when heated in the open air, and burns with a white vapor to antimonious acid. It fuses with the ter-sulphide of antimony to a red bead. It is distinguished from the other oxides of antimony by the readiness with which it is reduced to the metallic state upon charcoal, and by its easy fusibility and volatility.

The sesquioxide is the base of some salts—for instance, the tartar emetic. It is not soluble in nitric acid, but is soluble in hydrochloric acid. This solution becomes milky by the addition of water. A part of the salts of the sesquioxide of antimony are decomposed by ignition. The haloid salts are easily volatilized, without decomposition. Its soluble neutral salts change blue litmus paper to red, and are converted, by admixture of water, into insoluble basic and soluble acid salts.

Antimonious acid (antimoniate of sesquioxide of antimony, Sb^{2}O^{3} + Sb^{2}O^{5}) is of a white color, but, when heated, of a light yellow color, but changes to white again when cold. It is infusible and unaltered by heat. It forms a white hydrate, and both are insoluble in water and nitric acid. It is partly soluble in hydrochloric acid, with the application of heat. The addition of water causes a precipitate in this solution.

Antimonic Acid (Sb^{2}O^{5}).—In the pure state this acid is a light yellow-colored powder. Its hydrate is white, and is insoluble in water and nitric acid. It is sparingly soluble in hot concentrated hydrochloric acid. It forms salts with every base, some of which are insoluble, and others sparingly so. Notwithstanding that antimonic acid is insoluble in water, it expels the carbonic acid from the solutions of the carbonates of the alkalies. Antimonic acid and its hydrate changes moistened blue litmus paper to red.

Behavior of Antimony and its Oxides before the Blowpipe.

Metallic Antimony fuses easily upon charcoal. When heated to glowing, and then removed from the flame, it continues to glow for awhile, and produces a thick white smoke. The vapor crystallizes gradually, and coats the assay with small crystals which iridesce like mother of pearl (sesquioxide of antimony). It is not volatile at the temperature of melted glass. Ignited in an open glass tube, it burns slowly with a white vapor, which condenses upon the cool part of the tube, and exhibits some indications of crystallization. This vapor consists of the sesquioxide, and can be driven by heat from one place to another, without leaving a residue. If the metallic antimony contains sulphide of antimony, there is a corresponding portion of antimonious acid produced, which remains as a white sublimate after the sesquioxide is removed.

Sesquioxide of antimony melts easily, and sublimes as a white vapor. It may be prepared by precipitating and drying. When heated, it takes fire previous to melting, glows like tinder, and is converted into antimonious acid, which is now infusible. When heated upon charcoal in the flame of reduction, it is reduced to the metallic state, and partly volatilized. A white vapor sublimates upon the charcoal, while the external flame exhibits a greenish-blue color. Antimonious acid is infusible, produces a strong light, and is diminished in volume when heated in the external flame, during which time a dense white vapor sublimes upon the charcoal. It is not, however, in this manner reduced to the metallic state like the sesquioxide.

Antimonic acid, when first heated, becomes white, and is converted into antimonious acid. Hydrated antimonic acid, which is originally white, appears at first yellow while giving off water, and then becomes white again, while oxygen is expelled, and it is converted into antimonious acid.

The oxides of antimony produce, with blowpipe reagents, the following reactions: borax dissolves oxides of antimony in the oxidation flame in considerable quantity to a clear bead, which is yellow while hot, but colorless when cold. If the bead is saturated, a part of the oxide is volatilized as a white vapor. Upon charcoal, in the oxidation flame, it is completely volatilized, and the charcoal is covered with a white sublimate. Heated upon charcoal in the reducing flame, the bead is of a greyish color, and partially, if not wholly opaque, from the presence of reduced metallic particles. A continued heat will volatilize them, and the bead becomes clear. The addition of tin promotes the reduction.

Microcosmic salt dissolves the compounds of antimony in the flame of oxidation with intumescence, to a clear light-yellow colored bead, which when cold is colorless. Heated upon charcoal in the reduction flame, the bead is first turbid, but soon becomes transparent. The addition of tin renders the bead greyish while cooling, but a continued blast renders it transparent. Soda dissolves the compounds of antimony upon platinum wire in the oxidation flame, to a clear colorless bead, which is white when cold.

Upon charcoal, both in the oxidation and reduction flames, the antimony compounds are readily reduced to the metal, which is immediately volatilized, and produces a white incrustation of oxide of antimony upon the charcoal. If the antimony compounds are heated upon charcoal in the flame of reduction, with a mixture of carbonate of soda and cyanide of potassium (KCy), there are produced small globules of metallic antimony. At the same time, a part of the reduced metal is volatilized (this continues after the assay is removed from the flame) and re-oxidized. A white incrustation appears upon the charcoal, and the metallic globules are covered with small white crystals. If this white sublimate upon the charcoal is moistened with a solution of cobalt-oxide, and exposed to the reduction flame, a part of it is volatilized, while the other part passes into higher oxidation, and remains, after cooling, of a dirty dark-green color.

(d.) Tellurium (Te).—This is one of the rare metals. It occurs very seldom in the metallic state, but often with bismuth, lead, silver, and gold. Tellurium, in the pure state, is silver-white, very bright, of a foliated or lamellar structure, brittle, and easily triturated. It is inclined to crystallize. It is soluble in concentrated sulphuric acid without oxidation. The solution is of a fine purple color, and gives a precipitate with the addition of water.

Tellurium in the Metallic form.—By the aid of heat it is oxidized in sulphuric acid, a portion of the oxygen of the acid oxidizing the metal, while sulphurous acid gas escapes. This solution is colorless, and is tellurous acid, dissolved in sulphuric acid. It melts at a low red heat, and volatilizes at a higher temperature. If tellurium is heated with free access of air, it takes fire, and burns with a blue color, the flame being greenish at the edges, while a thick white vapor escapes, which has a feeble acidulous odor.

Tellurous Acid (TeO^{2}) is of a fine, granulous, crystalline or white earthy mass, which is partly soluble in water. The solution has a strong metallic taste, and an acid reaction upon litmus paper. Heated in a tube closed at one end until it begins to glow, it fuses to a yellow liquid which is colorless, crystalline, and opaque when cold. Beads of it remain usually transparent like glass. Heated upon platinum wire in the flame of oxidation, it melts, and is volatilized as a white vapor. When heated upon charcoal in the oxidation flame, it melts, and is reduced to the metallic state, but volatilizes and a sublimate of white tellurous acid is formed upon the charcoal. The edge of this deposit is usually red or dark-yellow.

Heated upon charcoal in the flame of reduction, it is rapidly reduced, the external flame exhibiting a bluish-green color.

Borax dissolves it in the oxidation flame upon platinum wire to a clear colorless bead which turns grey when heated upon charcoal, through the presence of reduced metallic particles. Upon charcoal, in the reduction flame, the bead is grey, caused by the reduced metal. After a continued blast, tellurium is completely volatilized, and the bead appears clear again, while a white sublimate is deposited upon the charcoal.

With microcosmic salt, the same reactions are produced.

With carbonate of soda, tellurous acid fuses upon platinum wire to a clear colorless bead, which is white when cold. Upon charcoal it is reduced, and forms tellur-sodium, which is absorbed by the charcoal, and metallic tellurium, which is volatilized, and deposits upon the charcoal a white incrustation (tellurous acid).

If tellurous acid, finely powdered charcoal, and carbonate of soda are mixed together, and the mixture be well ignited in a closed tube, until fusion is effected, and a few drops of boiled water are brought into the tube, they are colored purple, indicating the presence of tellur-sodium.

Telluric Acid (TeO^{3}) forms six-sided prismatic crystals. It has not an acid, but rather a metallic taste. It changes blue litmus paper to red; is slowly soluble in water, and rather sparingly. Exposed to a high temperature, but not until glowing, the crystalline acid loses its water, and acquires an orange color, but still it preserves its crystalline form, although no longer soluble in water, and is in fact so much changed in its properties as to present the instance of an isomeric modification.

If telluric acid is heated gently in a closed tube, it loses water and turns yellow. Heated still more strongly, it becomes milk-white, oxygen is expelled, and it is converted into tellurous acid. The presence of oxygen can be recognized by the more lively combustion which an ignited splinter of wood undergoes when held in it. Telluric acid produces the same reactions with the blowpipe reagents as tellurous acid.

SEVENTH GROUP.—LEAD, BISMUTH, TIN.

The oxides of these metals are also reduced to the metallic state by fusion with soda upon charcoal in the flame of reduction, but they are volatilized only after a continued blast, and a sublimate is thrown upon the charcoal.

(a.) Lead (Pb).—This metal occurs in considerable quantity in nature, chiefly as galena or lead-glance (sulphide of lead). Likewise, but more rarely, as a carbonate; also as a sulphate, and sometimes combined with other acids and metals.

In the metallic state, lead is of a bluish-grey color, high lustre, and sp. gr. 11.4. It is soft, and communicates a stain to paper. It is malleable, ductile, but has very little tenacity. It melts at about 612 deg.. Exposed to the air it soon tarnishes, being covered with a grey matter, which some regard as a suboxide (Pb^{2}O), and others as simply a mixture of lead and protoxide. At a glowing heat it is oxidized to a protoxide, and at a white heat it is volatilized. It is insoluble in most acids. It is, however, soluble in nitric acid, but without decomposing water.

(L.) Protoxide of Lead (PbO).—It is an orange-colored powder, which melts at a glowing temperature, and forms a lamellar mass after cooling. Protoxide of lead absorbs oxygen from the atmosphere while melting, which is given off again by cooling. Being exposed for a longer while to the air, it absorbs carbonic acid and water, and becomes white on the surface. It is soluble in nitric acid and caustic alkalies. It forms with most acids insoluble salts. It is slightly soluble in pure water, but not in water which contains alkaline salts. This hydrate is white.

([beta].) Red Oxide of Lead (PbO^{2}, PbO).—It forms a puce-colored powder. It is insoluble in caustic alkalies. Hydrochloric acid dissolves it and forms a yellow liquid, which is soon decomposed into chloride of lead and chlorine. It is reduced by ignition to the protoxide.

([gamma].) Peroxide of Lead (PbO^{2}).—It is a dark-brown powder. It yields with hydrochloric acid the chloride of lead and chlorine gas. When heated it liberates oxygen, and is reduced to the protoxide.

Lead combinations give the following reactions before the blowpipe: Metallic lead tarnishes when heated in the oxidation flame, and is instantly covered with a grey matter, consisting of the protoxide and the metal. It fuses quickly, and is then covered with a yellowish-brown protoxide until all the lead is converted into the protoxide, which melts to a yellow liquid. In the reduction flame and upon charcoal, it is volatilized, while the charcoal becomes covered with a yellow sublimate of oxide. A little distance from the assay, this sublimate appears white (carbonate of lead). Protoxide of lead melts in the flame of oxidation to a beautiful dark yellow bead. In the flame of reduction, and upon charcoal, it is reduced with intumescence to metallic lead, which is volatilized by a continued blast, and sublimates on charcoal, as mentioned above.

Red oxide of lead turns black when heated in the glass tube closed at one end, and liberates oxygen, which is easily detected by the introduction of an ignited splinter, when a more lively combustion of the wood proves the presence of uncombined oxygen. The red oxide in this case is reduced to the protoxide. Heated upon platinum foil, it first turns black, is reduced to the protoxide, and melts into a dark yellow liquid. In the reduction flame, upon charcoal, it is reduced to the metal with intumescence. After a continued blast, a yellow sublimate of protoxide is produced upon the charcoal, and at a little distance off, around this sublimate, a white one of carbonate of lead is produced. This sublimate disappears when touched by the flame of reduction, while it communicates an azure blue-tinge to the external flame. This is likewise the case with the peroxide of lead.

The different oxides of lead produce with the blowpipe reagents the same reactions.

Borax dissolves lead compounds with the greatest readiness upon platinum wire in the oxidation flame to a transparent bead, which is yellow when hot, but colorless after being cooled. With the addition of more of the lead oxide, it becomes opalescent. When heated by the intermittent flame, and with still more of the oxide, it acquires a yellow enamel after cooling. Heated upon charcoal, in the flame of reduction, the bead spreads and becomes opaque. After a continued blast, all the oxide is reduced with effervescence to metallic lead, which melts and runs towards the edges of the bead, while the bead again becomes transparent.

Microcosmic Salt dissolves oxides of lead upon platinum wire in the flame of oxidation easily to a clear, colorless bead, which appears, when highly saturated, yellow while hot. A saturated bead becomes enamel-like after cooling. The bead appears in the flame of reduction, and upon charcoal, of a greyish color and dull. By the addition of more oxide, a yellow sublimate of protoxide is produced upon the charcoal. By the addition of tin, the bead appears of a darker grey, but it is never quite opaque.

Carbonate of Soda dissolves oxide of lead in the flame of oxidation upon platinum wire quite readily to a transparent bead, which becomes yellow when cooling, and is opaque. Upon charcoal in the flame of reduction, it is rapidly reduced to metallic lead, which yields, after a continued blast, a yellow sublimate of oxide upon the charcoal.

(b.) Bismuth (Bi).—This metal occurs mostly in the metallic state, and less frequently as the sulphide. In the pure metallic state, it is of a reddish-white color and great lustre. It crystallizes in cubes. It is brittle, and may be readily pulverized. It melts at 476 deg., and is volatilized at a white heat. It is soluble in nitric acid, and forms the nitrate of bismuth.

([alpha].) Oxide of Bismuth (Bi^{2}O^{3}).—This oxide is a light yellow powder, fusible at a red heat, insoluble in caustic potash and ammonia. It is the base of the salts of bismuth. Its hydrate is white, and easily soluble in acids. The addition of water causes these solutions to become milky, because they are decomposed into a soluble acidulous and an insoluble basic salt of bismuth.

([beta].) Peroxide of Bismuth (BiO^{2}) is a dark-colored powder, completely soluble in boiling nitric acid, and yielding oxygen; produces, with hydrochloric acid, chlorine gas. It can be heated up to the temperature of 620 deg. without being decomposed; but, exposed to a temperature of 630 deg. it yields oxygen. Mixed with combustible substances, it glows with brightness.

([gamma].) Bismuthic Acid (Bi^{2}O^{5}) is a brown powder similar to the peroxide, but is converted by boiling nitric acid into a green, scarcely soluble substance (Bi^{2}O^{3}, Bi^{2}O^{5}). Its hydrate is of a red color.

BLOWPIPE REACTIONS.—Metallic bismuth is converted, when exposed upon platinum wire to the flame of oxidation, into a dark brown oxide, which turns light yellow while cooling. It is slowly volatilized when heated, and a yellow sublimate of oxide is produced upon the charcoal.

Oxide of bismuth melts upon platinum foil in the flame of oxidation very easily into a dark-brown liquid, which changes to a light yellow while cooling. By too strong a heat, it is reduced and penetrates the platinum foil.

Upon charcoal, in the flame of oxidation and of reduction, it is reduced to metallic bismuth, which melts into one or more globules. By a continued blast they are slowly volatilized, and produce a yellow sublimate of oxide upon the charcoal, beyond which a white sublimate of carbonate of bismuth is visible. These sublimates disappear in the flame of reduction, but without communicating any color to it.

Borax dissolves oxide of bismuth upon platinum wire, in the flame of oxidation, easily to a clear yellow bead, which appears colorless after cooling. By the addition of more oxide, the hot bead becomes orange. It turns more yellow while cooling, and when cool is opalescent. Upon charcoal in the flame of reduction, the bead becomes turbid and greyish colored. The oxide is reduced with intumescence to the metallic state, and the bead becomes clear again. The addition of tin promotes the reduction.

Microcosmic Salt dissolves oxide of bismuth upon platinum wire, in the flame of oxidation, to a yellow bead, which becomes colorless after cooling. By the addition of more oxide, the bead is yellowish-brown while hot, and colorless after cooling, but not quite transparent. This bead becomes enamelled when heated by the intermittent flame; also, by the addition of still more of the oxide, after it is cooled.

Upon charcoal, in the flame of reduction, and particularly with the addition of tin, the bead is colorless and transparent while hot, but while cooling becomes of a dark-gray color and opaque.

Oxide of bismuth is reduced, by fusion with carbonate of soda, as well in the oxidating as in the reducing flame, instantly to metallic bismuth.

As the above mentioned higher oxides of bismuth are converted by ignition into oxide of the metal and free oxygen, they have the same behavior before the blowpipe.

As bismuth occurs mostly in the metallic form, it is necessary to know how to distinguish it from metals similar to it. Its brittleness distinguishes it from lead, zinc and tin, as they are readily flattened by a stroke of the hammer, while bismuth is broken to pieces. Bismuth, in this latter respect, might perhaps be mistaken for antimony or tellurium; but, by the following examination, it is easy to separate bismuth from antimony or tellurium.

1. Neither bismuth nor antimony sublimates when heated in a glass tube closed at one end. At a temperature which is about to fuse the glass, tellurium yields a small quantity of a white vapor (some tellurium is oxidized to tellurous acid by the oxygen of the air in the tube). After that, a grey metallic sublimate settles on the sides of the tube.

2. Heated in an open tube, antimony yields a white vapor, which coats the inside of the glass tube, and can be driven by heat from one part of the tube to another without leaving a residue. The metallic globule is covered with a considerable quantity of fused oxide. Tellurium produces, under the same circumstances, an intense vapor, and deposits on the glass a white powder, which melts by heat into globules that run over the glass. The metallic globules are covered by fused, transparent, and nearly colorless oxide, which becomes white while cooling. By a high temperature, and with little access of air, metallic tellurium sublimes with the deposition of a grey powder. Bismuth produces, under similar treatment, scarcely any vapor, unless it is combined with sulphur. The metal is enveloped by fused oxide of a dark yellow color, which appears light yellow after being cooled. It acts upon the glass, and dissolves it.