in hydrochloric acid, but dissolves at once on the addition of nitric acid. In most acids it is soluble at the boiling temperature.

THE SULPHATE (Ni2SO, +7aq) and the double sulphate (KNISO +3aq) are soluble.

THE CARBONATE is produced by the action of the acid or neutral carbonates of potassium or ammonium on solutions of nickel salts, and also by allowing the hydrate to absorb carbonic acid gas from the air. It is also produced by the carbonates of the second subdivision, but only at the boiling temperature. It is a pale green precipitate.

Its formula is that of the mixed hydrate and carbonate. When precipitated at the boiling temperature, it is sometimes of the formula Ni, CO,, 6NiHO, after drying in the air, or in vacuo.

It is soluble in excess of carbonate of ammonium, forming a greenish-blue solution. It is but very slightly soluble in a concentrated solution of carbonate of sodium. It is readily soluble in most acids.

THE OXALATE is produced by the action of oxalic acid, but by the alkaline oxalates only after the lapse of some time. It is a greenish-white precipitate.

Its formula is Ni, C, O,+2aq.

It dissolves readily in hydrate or carbonate of ammonium, but less easily in other ammonium salts. It is insoluble in water, slightly soluble in solution of oxalic acid; but it dissolves with comparative rapidity in the stronger acids.

THE FERROCYANIDE is produced by the action of ferrocyanide of potassium. It is a green precipitate.

Its formula is Ni, Cfy; but it generally retains a portion of its precipitant.

It is soluble in hydrate of ammonium, forming a red solution; but the ammonium salts in general do not dissolve it.

THE FERRICYANIDE is produced by the action of ferricyanide of potassium; it is a reddish-brown precipitate.

THE PHOSPHATE is produced by the action of phosphate of sodium; it is a pale green precipitate.

Its formula is probably Ni, HPO

It is insoluble in water, but soluble in strong acids.

The other special reagents of the present and of the first and second groups, give no characteristic reactions with protosalts of nickel.

The means usually employed for the recognition of the protosalts of nickel are these,-the blowpipe reaction, the precipitation of the hydrate, of the cyanide, of the sulphide, and of the ferro- and ferricyanides.

SESQUI-SALTS OF NICKEL.

These salts are, as has been stated, unstable in the extreme. The only insoluble salts known are the sesquioxide ([Ni2], O1) and the hydrate (Ni, H, O3). When the hydrate is dissolved in acids, proto-salts of nickel are immediately formed. The sesquioxide may be obtained by moderately heating the protonitrate. It is also formed when hydrate of nickel comes in contact with a hypochlorite,——

4(NiHO)+CaClO=(Ni2), O,+CaC1+2H, O. If the solution decanted from the precipitated oxide be boiled, a further precipitation occurs; but the precipitate is now the hydrate (Ni, H, O3).

SALTS OF ZINC.

Solution for the reactions:-sulphate of zinc (Zn, SO1) in water.

The metal zinc differs from the preceding metals in many of its chemical characters: it forms only one series of salts, protosalts, of which the chloride (ZnCl) or the oxide (ZnO) may be taken as representatives. Two other combinations of zinc and oxygen are supposed to exist, the suboxide (ZnO), and the peroxide (Zn,O,); but their existence is somewhat problematical at present.

Most zinc salts, when heated before the blowpipe on charcoal, leave the white infusible residue of protoxide (Zn,O), which incandesces strongly, and when removed from the flame appears slightly yellow while hot, and becomes white on cooling. The metal itself being volatile below a white heat, if the oxide be reduced to the metallic state by exposure to the inner flame of the blowpipe, it volatilizes, and, passing through the highly

heated air which surrounds the blowpipe flame, oxidizes again, and is deposited on a more distant and cooler part of the charcoal as an "incrustation." The oxide, if moistened with a solution of nitrate of cobalt, and again strongly heated in the oxidizing flame, is found, after cooling, to have assumed a green colour. Zinc salts impart no colour to the flame; and when fused with borax on a platinum wire, the bead, if saturated with zinc, remains clear in the outer flame, but in the reducing flame becomes milk-white; and if very intensely heated, the zinc salt is reduced to the state of metal, and alloys with the platinum. The metal zinc itself burns in the blowpipe flame with an intense bluish or greenish white light.

The principal insoluble salts are the cyanide, the chromate, the hydrate, the sulphide, the carbonate, the oxalate, the ferrocyanide, the ferricyanide, and the phosphate.

THE CYANIDE is produced by the action of cyanide of potassium; it is a white precipitate.

Its formula is ZnCy.

It is soluble in excess of its precipitant, and in excess of the hydrates of potassium or ammonium, and in most ammonium salts; it is insoluble in water, but dissolves in acids, even in acetic.

THE CHROMATE is produced by the action of the chromate of potassium on solutions of zinc salts. It is a precipitate of a fine yellow colour.

Its composition appears to vary.

It is soluble in hydrate of potassium,-chromate of potassium and hydrate of zinc being formed, both of which are dissolved by the excess of the precipitant.

The Hydrate is produced by the action of the hydrate of potassium or ammonium; it is a white gelatinous precipitate. The ammonium salt does not precipitate the whole of the zinc. Its formula is ZnHO.

It is soluble in excess of its precipitants, and in ammonium salts; it is dissolved by most acids.

The Sulphide is produced by the action of the sulphides of

potassium or ammonium on solutions of zinc salts, or by passing sulphuretted hydrogen gas into an alkaline solution of zinc, while from neutral solutions of zinc this gas precipitates but a small part of the metal present, and from acid solutions none at all; the acetate of zinc, however, is an exception, being completely thrown down by hydrosulphuric acid, whether a neutral solution, or one acidified with acetic acid be taken. It is a white precipitate.

The formula of this precipitate is ZnHS,O,; i. e. it is a hydrate in which half the oxygen is "replaced" by sulphur: the hydrate has, it will be remembered, the formula ZnHO. In order to avoid fractions, the formula of the so-called sulphydrate of zinc may be thus written,-Zn, H, SO, or Zn, S, H2O.

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It is insoluble in excess of its precipitants, slightly soluble in acetic acid, but readily soluble in stronger acids.

THE SULPHATE (Zn, SO1+7aq) and the double sulphate (KZnSO,+3aq) are soluble.

THE CARBONATE is produced by the action of the carbonates of potassium or ammonium, but is only partially precipitated, except after boiling the solution, because, the precipitate being a mixed hydrate and carbonate, some carbonic acid is liberated, which retains a portion of the carbonate of zinc in solution. Its formula is Zn, CO,, 3ZnHO.

It is somewhat soluble in excess of carbonate of sodium, more so in carbonate of ammonium, and readily dissolves in the common ammonium salts. It dissolves in 44,642 parts of water, but separates when the solution is heated, and does not redissolve on cooling. It is readily soluble in most acids, and to some extent even in carbonic acid.

THE OXALATE is produced by the action of oxalic acid or oxalate of potassium on solutions of zinc salts. It is a white precipitate.

Its formula, when dried in the air, is Zn, C2O̟1+2aq.

4

It dissolves readily in hydrate or carbonate of ammonium, but less easily in other ammonium salts; it is scarcely soluble in water, but dissolves in hydrochloric acid.

THE FERROCYANIDE is produced by the action of ferrocyanide of potassium; it is a white precipitate.

Its formula is Zn, Cfy +1 aq.

It is partially soluble in excess of its precipitant, soluble in hydrate of ammonium and other ammonium salts, and slightly soluble in dilute acids.

THE FERRICYANIDE is produced by the action of ferricyanide of potassium: it is a precipitate of an orange-brown colour.

Its formula is Zn, Cfy2.

It dissolves readily in hydrate of ammonium and other ammonium salts.

THE PHOSPHATE is produced by the action of phosphate of sodium; it is a white semigelatinous precipitate, changing to a crystalline powder.

Its composition is Zn, HPO, when the precipitant has been added in excess; but if the solution of the zinc salt preponderate, its formula is Zn ̧ PO.

These precipitates are soluble in the hydrate and other salts of ammonium; they are insoluble in water, but soluble in acids. The other special reagents of the two preceding groups exert no characteristic action on solutions of zinc salts.

The chief means employed for the recognition of zinc salts are these, the blowpipe reactions on charcoal and with nitrate of cobalt, together with the formation of the hydrate and sulphide.

SECTION III.-Salts of the compound bases, which may be volatilized and destroyed by ignition.

SALTS OF MORPHINE, QUININE, AND STRYCHNINE.

In addition to the elementary basic radicals which this third group contains, we here introduce a few of that large class of compound basic bodies of which so great a number exists, but of which few are of sufficiently frequent occurrence to warrant consideration in an analytical work. They occur in nature, or in natural products. Morphine is found in opium, the inspissated juice of the Papaver somniferum; quinine in the bark of the Cinchona lancifolia and the allied trees; and strychnine in the seeds of the Strychnos nux-vomica and other species of Strychnos: and in those substances