This muriate loses 55 of water. What remains is a yel low de-hydrated muriate, which again becomes green in the air, by absorbing water.

The de-hydrated muriate, when fire is applied to it, does not melt: those parts only which touch the glass are decomposed there is then an extrication of simple muriatic acid and oxygenated acid : the salt not decomposed is sublimed under the form of pearl-like flowers of a golden yellow. These flowers in two days absorb humidity, and become green. The muriatic acid dissolves them with difficulty.

100 parts of muriate of nickel gave, by means of carbonate of potash, from 61 to 62 of carbonate; which supposes from 33 to 34 of oxide.

Sulphates of Nickel.-There are two, the one simple and the other potashed. The first crystallizes in hexaëdral prisms terminated by an irregular pyramid; the second in rhomboidal prisms.

The simple sulphate loses 46 parts out of the 100 of water. The de-hydrated residue again becomes green on absorbing humidity. When strongly heated for an hour, and at a red heat, in a luted retort, it is partly reduced to the state of sulphate with an excess of base: water takes away that part 'which has not lost its acid.

100 parts of this sulphate gave 64 of carbonate of a clear

green.

The potashed sulphate loses 24-100dths of water. The residue acts like that of the simple sulphate. The potashed sulphate only gives from 27 to 28 of carbonate for 100.

The two sulphates of nickel are transparent, of a fine eme rald green; they are unalterable in the air. M. Proust thinks that the sulphate of potash is united to that of the nickel in a constant proportion.

Extraction of the Nickel on a large Scale.-Let there be an ample solution of ore first calcined, and afterwards vitriolized with the residues of ether. It is requisite to sepa rate the nickel from iron, copper, arsenic, bismuth, and cobalt. The iron is at the maximum: in this state it has little affinity for the acids. We may then precipitate it to

the

the state of arseniate, by means of potash, which we must add gradually. Ammonia, or a prussiate, afterwards proves if all the iron has been precipitated.

Into the filtered solution we make a current of sulphuretted hydrogen to pass; the copper, bismuth, and the whole of the arsenic are precipitated in the form of sulphurets.

When the sulphuretted hydrogen occasions no more precipitate, we reduce the liquor in order to crystallize it. The potashed sulphate of nickel, less soluble than the potashed sulphate of cobalt, is the first to crystallize. On repeating the crystallizations, we succeed in separating the two salts: as to the last portions of the salt of nickel, washing them in cold water takes off the sulphate of cobalt they contain.

All these crystallizations require a bason of fine silver, if we wish to proceed smoothly.

We ascertain that a salt of nickel is pure, when the precipitate dissolved in ammonia abandons this solvent without our finding any cobalt in it.

When we precipitate a sulphate of nickel, we must not be too sparing of the potash without this precaution we might run the risk of precipitating sulphate with excess of base; which would alter the purity of the precipitate.

Carbonate of Nickel.-100 parts heated in a retort give from 54 to 65 of greenish gray oxide at the minimum. When we heat it in contact with the air, the oxide is black.

The minor oxide becomes carbonate when exposed to the air.

Hydrate of Nickel.-All the salts of nickel when thrown into boiling potash are changed into green hydrate; boiling does not alter the shade of them. Potash neither dissolves the hydrate nor the oxide of nickel.

The hydrate heated is reduced to gray oxide.

The oxide is in the state of hydrate in the saline combinations. The alkalis precipitate it in this state.

Major Oxide of Nickel.-The carbonate and hydrate rise to the maximum, when we put them in contact with the oxygenated muriatic acid. It is more difficult to oxidize the gray oxide.

The

The dry major oxide of nickel is black; when in a mass its fracture is vitreous.

This oxide, preserved in ammonia, gives out bubbles, returns to the state of gray oxide, and is dissolved in the alkali.

It gives a considerable quantity of oxygenated acid, with a muriatic acid at 15°. The solution is greenish yellow: crystals are formed upon cooling.

The oxides of nickel are reduced like those of cobalt. They are melted in the same way, with this difference only, that the cobalt gives a larger globule.

This metal has taken a surcharge of sulphur from 46 to 100; but the author has still his doubts on this subject. Arsenite and Arseniate.-They are formed like those of cobalt, and are of a fine apple-green colour. The arsenite heated in the tube loses its colour with water, sets at liberty some white oxide, and passes to the olive-green. Charcoal is necessary in order to take away all the arsenic.

When heated in a platina spoon, the arsenic is speedily dissipated. An oxide at the minimum remains.

The arseniate heated in a gun-barrel loses its colour with water; becoming of a hyacinth and transparent appearance: but at a red heat it passes to the clear yellow, and remains unalterable.

In the spoon the arseniate becomes white, reddens without melting, or emitting the smallest arsenical fumes: we must avoid flame in order to decompose it.

RECAPITULATION.

M. Proust concludes from the foregoing facts, and from those he has published in other memoirs, that cobalt, nickel, and most of the other known metals, have only two degrees of oxidation distinctly marked: he has not asserted, however, that a metal can only absorb two proportions of oxygen: he only says that it is not yet time to admit all the oxides hitherto spoken of, and in which we have neither seen the quantity of oxygen ascertained, nor the combinations which they are susceptible of forming with the acids; and he adds that colour is not a sufficient character by which to distinguish them.

8

1

There

There are only two metals which have as yet presented to the author more than two oxidations: these are tin and lead: notwithstanding this, the quantity of oxygen in the oxide of tin (the base of aurum musivum) is not yet known, nor that of the oxide in the nitrate of lead which has been boiled with plates of this metal.

It seems that the different oxides of one and the same metal may be intermediately dissolved, and form true combinations. Thus the green oxide of cobalt is a combination of blue and black oxide.

May not minium be a combination of brown oxide and of oxide at 9 in 100, and analogous to the foregoing?

Finally all the magnetic ores of iron and the attractable sands are mixtures or combinations of this order: if this were not the case, what could prevent the minor oxide from rising to the maximum? The oxide of the gun-barrel which has served to decompose the water is also in the same case; it is formed of the two oxides.

LXIV. The mean Motions of the Sun and Moon, of the Sun's Perigee, the Moon's Perigee and Node; the Times of their several Revolutions, both in respect to the Equinox and to the fixed Stars, and in respect to each other: deduced from the New Tables of the Sun and Moon lately published by the French Board of Longitude. By JAMES EPPS, Esq.

To Mr. Tilloch.

SIR,

SHOULD YOU

HOULD you think the enclosed paper deserving a place in your Magazine, it is at your service. It contains the result of very tedious though not difficult calculations; and, as it exhibits an interesting view of the modern solar and lunar astronomy, will, I think, prove acceptable to your astronomical readers. I am, sir, yours &c.

No. 4, Commercial Road,

May 14, 1808.

JAMES EPPS.

The