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were afterwards found, and in the most entire state of preservation. These had been extracted from the body through the incision into the left flank, as described by Herodotus, and the inside of the body was filled with cedar-dust and aromatics. The ears were remarkably preserved, and their form rendered entire by small dossils of linen being placed into the cavity of the outer ear, and the brain had been extracted through the nostrils, which were somewhat disfigured by the operation. No papyrus was found either between the legs or on the inside of the arms, as is sometimes the case; nor were there any amulets, scarabæi, &c. to be seen. The mummy of Osiri is to be regarded valuable, inasmuch as it affords another proof of the certainty of hieroglyphical literature—his character was found to correspond, as far as possible, with the description upon the case.

It is to be hoped that the trustees of the British Museum will relax from their determination not to allow any of the specimens contained that national collection to be unrolled, as much curious if not useful information may be obtained by such a research. The Museum ought to possess specimens of mummies in every state and condition, and they should be exhibited in the Gallery of Egyptian Antiquities, in the first, second, third, and fourth series of bandages arranged also according to their condition in life; and their history, as depicted upon the cases containing them, detailed. In this way, the collection, for which lately the Government have so liberally supplied the means for the purchase of Mr. Sams's collection, and various articles from Mr. Salt's, will be rendered truly useful.

A POPULAR COURSE OF CHEMISTRY.

No. IV.

CHEMICAL AFFINITY. The elements and their compounds are the materials with which we have to experiment; some of them are very powerful and dangerous substances, and Sir Humphry Davy has well compared these to the refractory spirits of Arabian romance, which, although occasionally subject to the skill of the magician, would often suddenly escape from control, and endanger his

person.

All experiments should be undertaken with some degree of caution, for chemical action is frequently amazingly sudden and vehement; in spite of every precaution, the most experienced chemists sometimes meet with accidents, and they are almost certain to happen to the juvenile operator. If he mixes substances together rashly and incautiously, an unexpected result takes place, perhaps a torrent of fumes, or a blaze of flame, is evolved; he loses his presence of mind, becomes alarmed at the spirit which he has thus unwittingly conjured into existence, and, being ignorant of the means of subduing it, he is half suffocated, scalded, scorched, or otherwise injured. Many accidents of this kind have happened in consequence of the ignorance and awkwardness of the young operator, and Chemistry is often denounced as a dangerous and disagreeable study; with a very little care, however, experiments may be performed without injury to himself, or annoyance to others.

Experiments should always be made in a room exclusively devoted to their performance, divested of any valuable furniture, yet well stored with chemical preparations and apparatus, so as to constitute a laboratory, within whose charmed precincts, the young chemist will find hours and days rapidly and imperceptibly glide away!; for the “ beginning of chemistry is pleasure, its progress knowledge, its objects truth and utility."

Most of the preparations which are requisite for the pursuit of this fascinating science, may now be readily procured at the shops of those who designate themselves “operative chemists," and thus great facilities for the study of chemistry are afforded to the juvenile student. The scene is vastly changed since the time of the alchymists, who were obliged to prepare all their own compounds, or even within the last thirty years, when there was much difficulty in purchasing “chemicals.” In those days the possession of any larger quantity than a few drops or grains, of some substances, was only to be acquired by long and anxious labour over the furnace, crucible, or distillatory apparatus; and experimenters had to sacrifice much time in preparing the materials for their experiments. There were but

very few shops where chemicals were sold, and that at a most exorbitant rate; oil of vitriol, for example, being charged at the rate of thirteen shillings per pound, to obtain which quantity the maker had to work for upwards of seventy hours. The process being gradually improved and expedited, the result became more copious, and it fell to halfa-crown per pound, but even then the supply was limited. At the present day, about fifty thousand tons of oil of vitriol are annually manufactured, and it is sold at the rate of five farthings per pound. Spirit of salt, or

it;

muriatic acid, was formerly sold at a much higher price than oil of vitriol, and could only be very sparingly procured; but at present it is so abundantly produced in certain processes of manufacturing chemistry, that it is of less value than that of the glass bottles necessary to contain

therefore torrents of muriatic acid are daily allowed to run to waste, and it is a matter of no small difficulty with the manufacturer to find out a place where to throw it away. A few years ago carbonate of soda was a valuable preparation, and sold for twelve shillings per pound; it may now be bought, dry and pure, for ninepence, or, in the crystalline state, for twopence per pound.

About thirty years ago a single grain of the metal potassium was a wonder; there were but few chemists who could elicit it from its combination with oxygen, and it could not be purchased at any rate, therefore its marvellous properties were almost exclusively exhibited in the laboratory or lecture-room of the noble Institution in which its discovery was made. As analytical chemistry advanced, the facilities for procuring potassium somewhat increased, and it could be sparingly purchased at the rate of about five shillings per grain, although many persons refused to part with it even at that price. It gradually became more abundant, and its price lowered in proportion, until at the present day it is kept in the shops as a common preparation, and sold for about fifteen shillings per ounce; a pound of potassium is now no uncommon quantity.

Although it has been stated that the room destined for the laboratory should be well stored with chemical preparations and apparatus, yet no extensive or extravagant outlay of money in their purchase is meant; on the contrary, a multitude of the most beautiful and instructive experiments can be made, with

very

limited means, and without any costly showy apparatus. It is better for the juvenile student to obtain a few “chemicals” as he requires them, rather than to fill his bottles and shelves at once with a host of articles selected from a catalogue. Those who are desirous of knowing how a regular laboratory should be fitted up, will find ample directions in Faraday's excellent work on Chemical Manipulation, which is also replete with valuable instructions concerning the art of making experiments.

To perform experiments with neatness, safety, and success, requires long and laborious study. A beginner must not expect anything like

. great precision in the results of his first attempts; nor must he be discouraged by repeated failures, but endeavour assiduously to ascertain the cause of them, and thus he will gradually, yet securely, acquire much valuable practical information. Chemistry is a science of experiment; facts are the data from which conclusions are to be drawn, for no reasoning, à priori, can enable us to judge as to the result of any chemical operation.

But now, to commence the more immediate subject of the present paper ; and this must be done by referring for a moment to Mechanical Attraction.

Mechanical Attraction principally exists between bodies of similar natures; or, where it takes place between solids and fluids, the bodies undergo no change of their respective natures; thus two pieces of lead by strong pressure unite with each other, and form one mass, which has precisely the same characters and habitudes of either piece of metal

separately. If a piece of lead be dipped into water, oil, or spirits of wine, and withdrawn, a drop of any of these fluids will be attracted by the lead, but they are not changed in their characters by this proceeding, for the attraction is merely mechanical, and mechanical means will instantly destroy it; thus the capillary attraction of a cloth or piece of blotting paper, will instantly draw any of these fluids from the surface of the solid lead.

Melt some lead in a ladle, and lay a little lump of tin upon its surface, it will float there, because it is much lighter than the lead; it will soon melt, and when this happens remove the ladle from the fire and let the metals cool. It will be found that, although the tin was the lightest metal of the two, it is not discoverable as a distinct stratum at the surface; that, cut the lump of mixed metals where you will, it presents an uniformity of composition, and nowhere can the tin and the lead be separately seen.

Take an ale-glass nearly full of water, and cautiously pour upon its surface some spirits of wine, coloured red with cochineal; this will float upon the water as a distinct stratum, (which the colour renders very evident, and it is employed for no other purpose,) for spirits of wine is lighter than water. Cover the glass with a card, or saucer, so as to prevent evaporation; take another ale-glass, about one-quarter full of water coloured with cochineal, and fill it up cautiously with colourless spirits of wine, which is best done by letting it run from the pipe of a funnel over which a bit of muslin is tied, this pressed against the sides of the glass, and nearly touching the water, will enable you to pour on the spirit without disturbing the water. Cover up this glass, as well as the former, and leave them for a day or two. At first the liquids preserve their respective situations, in virtue of their different relative weights; but, in the course of time, the lighter spirit will be drawn down through the heavier water, and the heavier water will rise through the lighter spirit, as will be evident from the red colour being diffused throughout the whole contents of both glasses, and when the action has arrived at its maximum, no repose will cause the spirit and water to separate into two distinct strata.

Now these are cases exactly analogous to the experiment with lead and tin, which has been already mentioned, some power of Attraction, very different from mere Mechanical Attraction, is here operating, to cause lighter substances to descend through heavier, and vice versa. It is Chemical Attraction,—the lead has a chemical attraction for the tin, the water has a chemical attraction for the spirits of wine; the substances, therefore, although of opposite weights and properties, are enabled mutually to penetrate and combine with each other, in opposition to the laws of gravity, and, when thus chemically combined, they will not separate, by any mechanical means. Every part of the lead, upon analysis, is found to contain tin, and the strength of the diluted spirit is found to be the same from whatever part of the glass it is taken for examination. Chemical Attraction is often called Heterogeneous Attraction, its distinguishing feature being, that it takes place between the particles of dissimilar bodies, causing their union, and producing a new and distinct class of compounds; when substances thus attract each other, they are

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said to possess mutual affinity,,hence chemical attraction is far more commonly called Chemical Affinity.

To take another instance of this power of attraction. Let us refer to the metals gold and mercury; the one a solid metal of a fine yellow colour, the other a liquid metal of a silvery whiteness. Bring them into contact, they attract each other with a very considerable force; and that this is not merely mechanical, but chemical, is soon proved by the change of physical characters which the metals undergo by being left for a short

a time in contact; the gold loses its solidity and colour, and the mercury its liquid form, -the resulting compound is a soft, unctuous mass, of the colour of mercury. That form of gold-leaf called “dentists', gold" is convenient for this experiment, it is very much thicker than common gold-leaf, and therefore more tangible; a little disc of it, about half an inch in diameter, presented to a globule of mercury about the size of this letter (0) will present the result; or several leaves of ordinary gold-leaf may be rubbed with a similar globule in the palm of the hand, with the point of the finger, and the desired compound is produced. Such compound is called an amalgam*, and no mechanical means enable us to separate the metals after they are thus once combined; but heat will destroy the chemical attraction existing between the two metals; the mercury, being volatile, flies away in fumes, leaving the fixed gold in its metallic state. The amalgam, when rubbed upon the surface of a clean plate of copper, adheres to it, and presents a silvery-looking surface, but no gold will appear: expose the amalgamated plate to heat, the mercury volatilizes, and leaves the gold in firm and close contact with the copper; and upon this principle depends the art of water-gildingt. Gilt metal buttons are an example of it, they are made of discs of clean copper, to which the amalgam of gold is applied, then heated to expel the

mercury, and the noble metal is left in the state called “dead gold,” which may be polished to the full extent of its splendour, by rubbing it forcibly with a smooth hard steel, or agate, tool, called a burnisher.

Silver has a strong attraction for mercury, and forms an amalgam which is not distinguishable in appearance from that of gold, but yielding up silver by heat, and therefore applied for silvering the surface of copper. In experiments with mercury it often happens that coin and plate become accidentally spotted with it, thus a sovereign instantly becomes white, and no longer passable; heat it carefully in the flame of a spirit-lamp, the mercury volatilizes, and the coin will assume its proper lustre by a little friction. When mercury is accidentally spilt, persons often endeavour to collect the scattered globules in a silver tablespoon, which becomes of course totally spoiled by uniting with the mercury; but heat will volatilize it as in the case just mentioned, and

The term amalgam is used to denote originated from the circumstance of this the compound of mercury with other metals; “ solutive water” being employed to disbut when they unite with each other to the solve gold. exclusion of mercury, as in the case of lead and tin, the term alloy is applied to the # The highly-ornamental buttons worn compound.

on full-dress coats, furnish examples of + Mercury was called hydrargyrum by gold in its dead and burnished state, the the alchymists, the term signifying water former is the appearance as it comes from of silver ; perhaps the term water-gilding the fire, the latter the result of friction.

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