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centrated sulphuric acid and pour into the funnel. As soon as the decomposition of the water and that of the muriate takes place, flashes of fire will be seen to issue from the bottom of the vessel, having a green colour.

If a ribbon be impregnated by a solution of gold, and hung in a jar containing this gas, the gold will be revived, and will gild the ribbon.

CHLORINE.

This gaseous body is now generally regarded as an elementary substance : but it was lately considered as a combination of muriatic acid with

oxygen, and was hence called oxygenated muriatic

acid gas.

It is obtained by heating a mixture of muriatic acid and black oxide of manganese over a lamp: the chlorine will be evolved. In this process, according to the present theory respecting the elementary nature of chlorine, the oxide of manganese and muriatic acid decompose each other : the oxygen of the oxide unites to the hydrogen of the muriatic acid to form water, leaving the other constituent of the acid, viz. the chlorine, disengaged.

Chlorine is rapidly dissolved by water, the solution being of a pale yellow colour : it has a nauseous taste, and an extremely suffocating smell. When the gas is perfectly free from moisture, it has no action on vegetable colours, but, dissolved in water, it destroys them entirely.

From this property, it is extensively employed in shortening the process of bleaching linen, and also paper; but it is said that it is apt to injure

the case.

the durability of the substances bleached, and no doubt, except due care is employed, this must be

Prints that have been stained by smoke and dust may also be whitened by it, as it does not act upon the printing ink.

Chlorine has likewise been found extremely efficacious in destroying the putrid effluviæ in prisons, and hospitals, and preventing the infection of the small-pox. But when used for this purpose, a small quantity only is diffused through the air, for, when taken into the lungs by itself, it is fatal to animal life ; and, indeed, in preparing it, great precaution should be used not to inhale it, as it is extremely dangerous if not sufficiently diluted.

Notwithstanding its unfitness for respiration, it supports combustion in a remarkable degree. Some bodies, as phosphorus, and several of the metals, are spontaneously ignited when plunged into a vessel of chlorine; on this account it is now reckoned one of the supporters of combustion, a property, which was lately supposed to be only enjoyed by oxygen. In this view, combustion is regarded only as the result of intense chemical action, and it is supposed that the compounds of chlorine have less capacity for caloric than their .constituent principles, and, consequently, that caloric is evolved at the moment of their formation.

Chlorine is known to combine with oxygen in three different proportions, forming

1. Oxide of Chlorine, or Euchlorine, a gaseous body, not acid, having a smell less irritating than chlorine.

2. Oxychloric Acid, which does not exist independent of water or a base.

3. Chloric Acid. -Chloric acid cannot be obtained unmixed with water. It is colourless and

sour ; acts on metals, and combines with alkalies, forming chlorates.

Chlorate of potash was formerly called oxymuriat of potash. It is a soluble white salt. When heated it gives out oxygen, and the residue is chloride of potassium. It forms extremely explosive compounds with phosphorus, sulphur, and charcoal. A grain, with a minute portion of phosphorus, laid upon an anvil, and struck with a hammer, makes a very loud report; but this experiment should not be attempted by the young student. From its detonating quality, it had been imagined that it could be used advantageously in the manufacture of gunpowder, but it has not succeeded.

Chlorate of potash is made by causing a stream of chlorine to go through a solution of caustic potash.

The combinations of chlorine with other simple bodies, form chlorides, if they are not acids, as chloride of sulphur, &c.

Chlorine and hydrogen. This compound body, which, according to the present nomenclature, is called hydrochloric acid gas, was known by the name of muriatic acid gas. It is readily obtained by distilling a mixture of common sea salt and sulphuric acid. The sulphuric acid combines with the soda, one of the constituents of salt; and the other constituent, the muriatic acid gas, is set free. Muriatic acid gas cannot support life nor combustion. It has a sharp pungent odour, and occasions white fumes when it is mixed with moist atmospheric air. It reddens vegetable blues. It combines with the alkaline bases: with ammoniacal gas it forms muriate of ammonia.

[blocks in formation]

It is decomposed by the electric spark into hydrogen and chlorine.

It is readily absorbed by water, which then becomes very acid, and forms the liquid muriatic acid.

The muriatic acid, called also the marine acid and the spirit of salt, is in very common use. It is obtained, as above-mentioned, by distilling sea salt and sulphuric acid. It exists in a state of combination with alkalies and earths in the mineral kingdom in great quantity, chiefly with soda, lime, and magnesia. With soda it forms muriate of soda, common or sea salt, with which every part of the ocean is impregnated, and also some lakes. Muriate of soda also exists in the form of a rock in the earth, whence it is extracted : it is called rock salt. The most considerable mines of rock salt are in Poland; extensive mines are also worked in Hungary, Spain, and Cheshire in England. Muriate of soda is obtained also from the sea water, by driving off the water by evaporation; and this is done either by exposing salt water in shallow places, called salt pans, to be evaporated by the heat of the sun, or by boiling salt water in vessels, or by these methods combined. Muriate of soda, so procured, is always contaminated with muriate of magnesia and muriate of lime, from which the salt is purified by different processes.

IODINE.

This substance, considered as a simple body, has been but lately discovered. It exists in certain marine plants, and is procured from kelp, which is

made by burning them. It is obtained first in the form of fumes, of a violet color, which condense in small opaque crystals of a blackish grey color and metallic lustre, resembling plumbago. It appears to be an element that exists in small

quantity. It is capable of producing acids by combination with other substances. With oxygen, it forms iodic acid ; and, with hydrogen, it forms hydriodic acid. It combines with phosphorus at the common temperature, giving out heat and light, and produces with it phosphuret of iodine. With sulphur, it makes sulphuret of iodine.

Iodine, also, unites with all the metals, forming with them iodurets.

SULPHUR,

Sulphur, known also by the name of brimstone, is a mineral substance, frequently found pure in nature.

It is of a pale yellow colour, without taste and, also without smell, except when heated. It is chiefly a volcanic product, and a great deal of what is used in this country is brought from Italy and Sicily. It is found also in nature combined with most of the metals as orés : united to iron, it forms iron pyrites.

Sulphur is extracted from pyrites by exposing it to heat in tubes, by which the sulphur is driven out and received in vessels with water: when melted and poured into moulds, it constitutes the roll sulphur in common use. A good deal of this is made in England. The sulphur thus obtained, however, is not quite pure. To purify it, it is sublimed by

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