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ing the process on a large scale, the common still is used; but for small experiments, the common retort and receiver may be employed. The specific gravity of alcohol, prepared in this manner, is 0.791 at 68°, or 0.796; but the alcohol of commerce is seldom under 0.837. Alcohol is a transparent fluid. It cannot be frozen. It is very volatile, and boils at 1731° It combines with water in various proportions, and forms spi. rits of different degrees of strength. A mixture of alcohol and water, or any liquor whose specific gravity is 0.920, is proof spirit. When spirits are under this, or weaker than 0.920, they are said to be under proof; when stronger, to be above proof. Alcohol is decomposed by passing its vapour through a red hot porcelain or metallic tube, affording several products. It is composed, according to the recent experiments of Saussure, of oxygen 37.85, carbon 43.65, azote 3.52, and ashes 0.04. Alcohol dissolves phosphorus and sulphur in small proportion; the fixed alkalies, and some of the salts. The strong acids decompose it. The colour of the flame of alcohol is tinged by various bodies. Alcohol is a proper solvent of resins and essential oils; but does not act on gummy matter.

SECTION I.

OF ETHERS.

SULPHURIC ETHER.

Experiment l. If a mixture of equal parts of sulphuric acid and alcohol be distilled in a glass retort, to which a large receiver is attached, a product will come over and condense, which is sulphuric ether.

Experiment 2. If to this fluid some chalk be added, and again distilled, the rectified or purified ether will. be the result.

Remark. "Ether is produced by the action of the acid on the alcohol: there remains in the retort a black carbonaceous matter. It is a colourless fluid, whose specific gravity, when pure, is 0.632 at 60°. It is very vulatile, and boils at 98 degrees, and in a vacuum at—20° It produces a considerable degree of cold by evaporation. According to Saussure, it is composed of 58.20 Carbon, 22.14 hydrogen, and 19.66 oxygen.

When passed through an ignited tube it is decomposed, and converted into oil, charcoal, water, and a great proportion of carburetted hydrogen gas. It receives some of the metallic oxyds, as those of gold and silver, and dissolves some metallic salts.

It is converted into sweet oil of wine by sulphuric acid. It is inflamed spontaneously by oxymuriatic acid. It dissolves several oleaginous substances, and unites with alcohol forming various preparations sold under the name of sweet spirit of vitriol, Hoffman's anodyne drops, golden tincture, &c.

NITRIC ETHER.

Experiment 1. If nitric acid and alcohol be mixed in proper proportion, on standing a yellow coloured fluid will form on the surface, which is nitric ether. Or,

Experiment 2. If a mixture of nitric acid of the specific gravity 1.283 and alcohol, be distilled in a retort, the product will be nitric ether.

Remark. From the retort should pass a tube, that goes to the bottom of a tall glass jar, half filled with a saturated solution of common salt in water. Several of these jars are connected together by tubes, and from these a tube passes to convey the gaseous products to the water trough. The ether condenses on the surface of the liquid in these jars. It contains at first a little nitrous and acetic acids, from which it is purified by agitation with chalk in a close phial, until it ceases to red. den vegetable blues. Nitric ether thus prepared has a pale yellow colour, and a very strong etherial odour.

Its taste is strong and quite peculiar. It is rather heavier than alcohol, but much more volatile than sulphuric ether. Hence it only moistens bodies for a moment, and produces a considerable cold by its evaporation. The heat of the hand is sufficient to make it boil. According to Thenard nitric ether contains 48.52 oxygen, 28.45 carbon, 14.49 azote, and 8.54 hydrogen..

MURIATIC ETHER.

Experiment 1. If a mixture of muriatic acid and alcohol be distilled in a retort connected with Woulfe's bottles, partly filled with water, a product will be obtained called muriatic ether.

Experiment 2. If a mixture of alcohol, and oxy-mu. riate of potash, according to Van Mons, be distilled the same product will be obtained.

Remark. If the temperature be as low as 709, the ether will assume the liquid state; but above this it takes the form of gas. Muriatic ether is composed of 36.61 carbon, 29.31 oxygen, and 10,64 hydrogen. In order to obtain it in a liquid state, the jars should be surrounded, with ice. The nature of this compound was first investigated by Gehlen in 1804, and Thenard, in 1807.

ACETIC ETHER.

Experiment 1. If a mixture of alcohol and acetic acid, according to the count de Lauraguais, be distilled, and the operation repeated twelve times, acetic ether will be obtained.

Remark. This compound was discovered by the count in 1759. It seems to be a kind of combination of acetic acid and alcohol. It boils at 1600 and when inflamed, it burns with a yellowish white flame, acetic acid being evolved.

Besides the ethers already enumerated, there are others lately discovered, which are formed by using other acids, as the phosphoric, &c. As they are but little

known, we refer the reader to the more extensive and voluminous work of Dr. Thomson.

SECTION III.

VOLATILE OILS.

As oils, properly speaking, are divided into two kinds, which are denominated by the terms fixed and volatile, we shall treat in this place of volatile or essential oils. From the products obtained, when the volatile oils are burnt, it has been concluded that they are compounds of hydrogen and carbon; but no exact analysis has been made of them.

They are distinguished by the following properties :

1. Liquid, as often liquid as water; sometimes viscid.

2. Very combustible.
3. An acrid taste and a strong fragrant odour.

4. Volatilized at a temperature not higher than 212 degrees.

5. Soluble in alcohol and imperfectly in water, 6. Evaporate without leaving any stain on paper.

Volatile oils are almost all obtained from vegetables, and they exist in every part of plants except the cotyledons of the seed, were they have never been found. They are sometimes obtained from plants by simple expression. But in general they are procured, by mixing the vegetable substances containing them with water and distilling.

The oil comes over along with the water, and swims on its surface in the receiver. In this way is obtained the essential oils of almost all vegetable substances, such as mint, peppermint, rosemary, lavender, &c. Volatile oils evaporate very readily in the open air; are soluble in alcohol; and are decomposed by sulphuric acid.

SECTION IV.

FIXED OILS.

To this class of oils belong such as require a higher temperature to volatilize them, at or above 600 degrees. They are insoluble in water and alcohol, and leave a greasy stain upon paper. Fixed, called also fat and expressed oils are obtained partly from animals, partly from vegetables by simple expression; such as whale oil, olive oil, linseed oil, &c. They gradually absorb oxygen when exposed to the air, and become solid. Some oils retain their transparency after they have become solids, such are drying oils, those that become opaque are called fat oils. The drying oils are those of linseed, nut, poppy and hempseed oils, which acquire. the property of drying more completely after they have been boiled, which is done either alone or with the addition of litharge, or other drying substance as it is termed. If they are set on fire, as is done in some cases, the oil becomes of more consistence, and approaches the nature of varnish. In this state they are used in the manufacture of printers' ink.

The combination of fixed oils with potash or soda, forms hard soap, and with oxyd of lead, the basis of the different plasters. Oils are composed essentially of hydrogen and carbon, some become rancid, and change their apparent, as well as chemical properties ; either by exposure to air or an increase of temperature; and if the temperature be considerable, or a high heat be used in their production, they become empyreumatic.

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