by pouring gradually hydrochloric acid on fulminating silver, till the filtered liquid was no longer troubled. Its taste is sharp; it reddens the blue turnsole paper; does not precipitate nitrat of silver; it neutralizes the bases, and then acquires the property of colouring of a deep red the perchloride of iron. From the results obtained, these chemists were led to suppose that the chlorine in this acid was combined with hydrogen; and to ascertain this they instituted the following experiment :

They put a known weight of fulminating silver with water into a vessel with three openings, c, Fig.2, placed in a water bath, and hydrochloric acid was then poured on the fulminate by the tube,f. To facilitate the volatilization of the hydrocyanic acid, a current of hydrogen gas was supplied by the tube, b, from the bottle, a, which contained zinc and diluted sulphuric acid. The hydrogen gas traversed a tube, d, containing fragments of marble and a little water, and then escaped across a solution of nitrat of silver contained in the vessel, e. By this means these chemists expected to obtain cyanide or prussiat of silver; but to their surprise no precipitation took place, although they had previously ascertained that the same solution of silver gave an abundant precipitate when hydrocyanic acid was poured into it. In conclusion, these chemists remind the reader, that all the fulminating compounds detonate with great facility, even in water; and that the experimenter should not use glass rods to stir the liquid, in which they may be suspended without being dissolved. By using these rods they caused some fulminating silver and barytes to detonate in a porcelain vessel: owing to a great part of the fulminate being in a state of solution, and it being hardly warm, no serious consequences resulted from this accident, which might otherwise have been fatal.

CHEMISTRY AS A SCIENCE. Art. XI.

METALS, FORMING ALKALIES WITH

OXYGEN.

WE have hitherto treated of substances, most of which were unknown to our readers, but we now come to speak of a class of bodies, some of which are extremely familiar to them, namely, metals; but, in the first instance, of metals which have perhaps scarcely ever been heard of by some of our readers, and have yet only been obtained in such small quantities, as to have been put to no use. Chemists apply the term metals to a numerous class of undecompounded substances, distinguished by the following general properties, though some of them do not possess all these properties: They are of a peculiar lustre, which belongs to the smallest particle of them; they are opaque, fusible, conductors of electricity and heat; are malleable, that is, extend or spread out when struck with the hammer; are ductile, that is, may be drawn into wire; and when exposed in combination to the action of electricity, they separate at the negative pole. With gold, silver, iron, copper, lead, &c. every European is intimately acquainted; they have been known, in fact, from the most remote antiquity; but potassium, sodium, lithium, calcium, and others, were only discovered very lately, and by the application of very powerful instruments. In describing each of these substances more particularly, we shall advert shortly to its history; and shall, therefore, now only observe, that those which have been longest known are still the most useful. So great were the advantages which the discovery of them conferred on the early inhabitants of the world, that the first metallurgists, like the first improvers of agriculture, were deified; and Vulcan, in the ancient mythology, was of a rank at least equal to Ceres. Those who love trifling discussion have, indeed, raised a question, whether the taming of animals, or the discovery of metals, has had the most influ

ence on the improvement of society: this may, however, be safely asserted, that neither would have been so beneficial without the other, and both have been eminently serviceable. Without the metals, many of the arts and sciences could hardly have existed; and without the taming of animals, the means of subsistence must always have been small and precarious.

The class of metals of which we are now to speak, was discovered only a few years ago, and with their properties we are yet very imperfectly acquainted. Prior to 1807, the substances which are probably known to our readers by the names of potash and soda, and another alkaline substance called lithia, obtained from a mineral called petalite, were considered and classed by chemists as a distinct species of substances called alkalies, which were simple and undecompounded. Prior, also, to that period, the earthy and stony substances of the globe had been all reduced, chemically speaking, to a certain and not a large number of substances, which were called earths and metals. At that period, however, Sir Humphry Davy succeeded in decomposing potash. He placed thin pieces of potash, slightly moistened, on a plate of platinum, attached to the negative end of a powerful galvanic battery, and brought a platinum wire from the positive end of the battery to its upper surface. The potash was gradually decomposed, oxygen gas was evolved at the extremity of the positive wire, while globules of a white metal like mercury appeared at the opposite side, in contact with the plate of platinum. SirHumphrey verified this fact by numerous experiments, and all the chemists of Europe have adopted his opinion, that these globules are a peculiar metal forming the basis of potash, which, in fact, is a compound of it and oxygen. This metal Sir Humphrey named potassium. In 1808, the same illustrious chemist succeeded, by the same means, in decomposing the alkali called soda; and the metal he then obtained he called sodium. He

afterwards decomposed lithia, lime, barytes, strontian, and several of the substances previously considered as undecomposed earths, by the aid of his galvanic battery; but though he succeeded in showing, by producing an amalgam between the bases of these earths and mercury, that their bases were metals, he can hardly be said to have obtained these metals in sufficient quantity for examination, or have made us acquainted with their properties. In fact, they have such an intense affinity for oxygen, that they instantly combine with it, and and regenerate the earths from which they were obtained. The discoveries of Sir H. Davy were, however, deemed sufficient to authorize the conclusion, that the substances which were previously classed as earths are all metallic oxides, or metals combined with oxygen. Little more is known of the bases of most of these substances than the bare fact, that when they are exposed to the action of the galvanic battery, in contact with mercury, an amalgam of that metal is obtained. We shall enumerate the properties of these metals, as far as they have been investigated; but must remind our readers, that they have never been put to any use, and have only been obtained in very small quantities; while their compounds, with oxygen or the alkalies, and earths, are extensively employed in the arts, and form the whole solid materials of the globe. In compliance with the systematic arrangement laid down, we shall at present say no more of these important compounds than may be sufficient to lead our readers to a knowledge of their real or supposed metallic bases. We shall in the present article confine ourselves to the alkalies and alkaline earths.

If wood be burnt to ashes, and these ashes be afterwards washed with water till it comes off free from any taste, and the water be afterwards filtered and evaporated to dryness, the substance which remains is the potash of commerce. When heated to redness, some im

purities are burnt_off, and then it is called pearl-ash. Pure potash is obtained from this, by mixing it with twice its weight of quick lime, and ten times its weight of pure water. The mixture is to be boiled for some hours in a clean iron vcssel, or allowed to remain for fortyeight hours in a glass vessel, shaking it occasionally; then pass it through a filter, and boil it in a silver vessel till it is, when cold, as thick as honey. Pour on it a quantity of alcohol, equal in weight to onethird of the pearl-ash, shake the mixture, boil it for a minute or two, and then pour it into a glass vessel, and cork it up. The mixture gradually separates into two portions, the upper of which is pure potash dissolved in alcohol. Decant the solution into a silver basin, and evaporate it rapidly till a crust forms on the surface, and the liquid below will become solid on cooling. Pour it in a porcelain vessel, and, when cold, a white concrete substance is formed, which is pure potash. This is a remarkably acrid and corrosive substance, is employed for a variety of purposes, and was known, at least in its impure state, to the ancient Gauls and Germans.

Soda resembles potash so much, that the two were confounded together up to the year 1736, when Du Hamel proved that soda is the base of common salt, and is different from potash. It is obtained by burning a certain species of plants, called salsola, which grows on the sea shore. It is then called kelp, or barilla, the plant from which it is procured bearing this name in Spain, and is very impure. To obtain it pure, the same process is followed as for obtaining potash. Lithia is a caustic substance, which has only been obtained by a few chemists, from subjecting a mineral called petalite, of which it forms a component part, to analysis. Lime is well known to our readers; but what is called quick-line, in common life, is the lime of the chemist. Barytes is an earth obtained from the mineral

called ponderous spar, or sulphate

of barytes, by decomposing the mineral. It resembles lime in its properties, but is of a greyish white colour, is more caustic, and, when taken into the stomach, is a violent poison. Strontian is an earth obtained from exposing a mineral, which was first found in the leadmine of Strontian, in Argyleshire, and hence its name, and subsequently in several other parts of the world, to a violent heat, when mixed with charcoal-powder. The earth thus obtained is of a greyish white colour, having a strong acrid and alkaline taste, and a resemblance to lime. We have already pointed out the mode in which the metallic bases of these several substances were discovered, and we have only now to enumerate their properties, as far as they have been investigated.

Potassium, the metallic base of potash, is white, with a lustre like silver, or mercury; it is lighter than water at the temperature of 50° it is solid, soft, and may be moulded with the fingers; at 136 it becomes perfectly fluid; at a heat a little below redness it rises in vapour; at 32° it is hard and brittle ; when exposed to the air it absorbs oxygen, and in a short time is covered with a crust of potash, which absorbs moisture rapidly, and is converted into a solution of potash. When heated in oxygen gas to the temperature at which it begins to evaporate, it burns with a brilliant white light, producing intense heat. When thrown on water, it decom− poses this fluid, swimming on the surface, and setting fire to the hydrogen gas as it is evolved. On all fluids which contain water or much oxygen, or chlorine, it acts with great readiness, and has such power over other substances, that Sir Humphrey Davy says, it may be compared to the alkahest, or universal solvent of the alchymists. Sodium, the base of soda, resembles potassium in most of its properties. It is distinguished from potassium, however, by remaining soft at the temperature of32o,and by requiring a much higher temperature to melt it. It is also somewhat heavier

than potassium, though still lighter than water; and when thrown on this fluid it decomposes it, producing a violent effervescence, but it does not catch fire like potassium. Lithium, the base of lithia, is said to resemble sodium; but it must be observed, that some chemists who have made the attempt, did not succeed in obtaining the metallic base of lithia. Calcium, the base of lime, was obtained in such small quantities, that it has not been investigated. It is said to be heavier than water, to burn brilliantly, and that quick lime is the product of the combustion. Barium, the base of barytes, is of a dark grey colour, not so brilliant as cast iron; it effervesces violently in water, and a solution of barytes results. Of strontium, the base of strontian, nothing is known; but it has been demonstrated by Sir Humphrey Davy, that the base of stronţian is a metal to which he has given this name. The compounds of these metallic bodies which are of importance, such as potash, soda, and lime, will be again brought under the notice of the reader.

ANALYSIS OF THE ASHES OF VESUVIUS. BY M. VAUQUELIN. THESE ashes are in very fine dust, (probably from having existed in the volcano in the state of vapour mingled with the vapour of water and with air,) but they contain a few larger particles interspersed.

Their colour is gray, like woodashes, whence they, no doubt, derived their name: they have no sensible taste.

A certain quantity of these ashes having been shaken in long glass tubes with water, and the liquor decanted at the end of two minutes, afterwards at the end of four, and so on doubling every time to 16 minutes, we obtained powders of different sizes; but the largest, even seen through the microscope, exhibited nothing recognizable.

Thirty grammes of the ashes, shaken with distilled water occasionally for a week, gave to

that fluid, after concentration by evaporating, very decided alkaline properties. Evaporating to dryness left some sulphate of lime and muriate of ammonia.

Before the blow-pipe these ashes melt, but not easily, into a very shining black glass, much resembling obsidian, or the glass of vol

canoes.

The ashes heated alone in a retort, gave a white sublimate of muriate of ammonia.

Mixed with a quarter of its weight of chlorate of potash, (dry) and heated in a retort, whose beak was dipped under mercury, thirty grammes of the ash gave twenty cubic centimetres of carbonic acid. The ash was digested with diluted nitric acid; it swelled, and became gelatinous. After many days of digestion, the acid was further diluted with warm water, poured off clear, and evaporated alone in a porcelain dish. It gave an ill crystallized salt, of a yellowish white colour, with an astringent taste, and slightly deliquescent.

As I supposed this salt to contain nitrate and sulphate of lime, and other non-deliquescent salts, I added strong alcohol, which dissolved one portion and left another unacted upon. In the latter, I found nitrate of potash and sulphate of lime; in the former, the alcohol, which was somewhat watery, had retained, I conjectured, a portion of the nitrate of potash. I therefore first precipitated the alumina and iron by ammonia, then evaporated the liquid, and, when dry, calcined it strongly, to decompose the nitrate and oxalate of ammonia. An alkaline residue remained, which, on saturation with nitric acid, gave nitrate of potash. It is therefore plain, that the ashes of Vesuvius contain a sensible quantity of potash. This alkali is evidently combined in the ashes with silica and alumina, otherwise it would have dissolved by mere digestion with water; besides, this combination is also proved by the gelatinous state produced on digestion with nitric acid. I proceeded by the usual me

thods to separate the silica, alumina, and oxide of iron, which are the three principal ingredients in these ashes. The silica composes about 55 per cent, the alumina 15, and the oxide of iron 16.

I also found some slight traces of copper and manganese, but neither gold, copper, nor antimony,

I did not think it worth while to ascertain the proportion of the different elements more exactly, as they no doubt vary considerably at different times of eruption.

CHEMICAL SOCIETY.

By inserting the following letter, we shall show to our Correspondent that we approve of his plan, and are ready to do what lies in our power to promote it.

To the Editor of the Chemist. SIR,-You must be aware, that the majority of the readers and admirers of your little Work is composed of persons who can deyote but a small portion of time to chemistry, and who at the same time are not in circumstances to lock up part of their capital in apparatus, &c. for prosecuting the study of that science; would it then not be advisable for you, who appear so much the encourager of beginners, to form, as it were, a nucleus for a society of young chemists, who might, at their common expense, purchase chemical tests, instruments, &c. as they want them, and that without bringing down ruin on any of them. I should like the society to be respectable and select, and to meet at a stipulated number of times every week,

I have the honour to be,
Sir,
Your most obedient,
A. W.

May 7th.

the oil of salt, which has not only had the effect of completely laying the dust, but it has operated also as a cement, making the pavement at once firm and smooth. Mr. Gilmore has tried his discovery on a part of the turnpike-road near Birtley, when the experiment succeeded to the extent of his wishes. He lately applied a quantity of the oil of salt to that part of Dean-street, which is the only part of Newcastle which has yet been M'Adamized, and the effect has been such as we have described. The dust has been laid much more efficiently than it had previously been by water; besides that it gives the pavement a firm and compact body, while the expense will, in all probability, be less than by an application of water.-Tyne Mercury.

THE GUIDING LIGHT OF
NATURE.

A DR. TODD has sent a paper to the Royal Society, which has been read, on the light emitted by the glow-worm and the fire-fly. In the former the light is of a fine topaz yellow colour, with a tinge of green, and is so vivid that within a few inches the hour on a watch may be read. The light of the fire-fly is of a pale yellowish tint, with continual flashes of vivid light. This animal may be seen shining in full moonlight. Dr. Todd supposes the light to be animal light, analogous to animal heat, and separated by the animal, like the heat, from its combinations with matter. He adopts the opinion that the use of this light is to guide the male insects to the female, as the males always approach light. We had at first some doubts as to the purpose for which these lights were given, and thought there might perhaps be some worthy magistrates who look after the worms and exhibit their lanterns, and their "Beware of bad houses," till we remembered that every female is supposed to shine; and as all cannot be vicious even among insects, we concluded it was the guiding light of nature.