203. Chlorine plays such an important part in connection with human industry, that a short sketch of its history and properties cannot but be interesting and useful.

Chlorine is an elementary body, as far as is yet known. It is true that this substance has been suspected by chemists to be a compound, but although its decomposition has been more than once announced, it has not, within the writer's knowledge, been verified.

Chlorine was discovered by Scheele in 1774, and, in accordance with the crude notions then entertained, was called "dephlogisticated marine air." Sir Humphrey Davy investigated its properties at a later date, and gave it the name which it now bears, derived from a Greek word signifying pale green, or yellowish green. The name of the mineral "chlorite" has the same derivation, but this substance contains no chlorine, and must not be confounded with the chlorous acid salts, which are also called chlorites.

Under ordinary circumstances, chlorine is a pungent and suffocating gas of a yellowish green color, and is 2.44 times as heavy as an equal volume of air. When compressed to one-fifth of its normal volume it becomes liquid, and is then 1.33 times as heavy as an equal volume of water.

Chlorine has powerful affinities, which cause it to combine, under suitable conditions, with almost every other known element. When naturally combined with silver, it forms the well known mineral horn silver. It is also found in nature, combined with lead, copper, and other metals, especially with sodium in the compound known as common salt. When it is considered that the entire ocean, covering three-fourths of the surface of the globe, with a depth, in places, of several miles, is heavily charged with salt, and that over six-tenths of the weight of salt consists of chorine, it will be perceived that a more definite statement could hardly convey a more definite idea of the enormous quantity of chlorine existing in the world. If all the chlorine in the ocean could be set free at once, it would destroy every vestige of life on the globe.

In combination with hydrogen, chlorine forms hydrochloric acid gas, and in this form is evolved in enormous quantities in the manufacture of soda-ash from salt, by the agency of sulphuric acid. The gas, dissolved in water, forms ordinary hydrochloric or muriatic acid. This acid, in contact with manganese binox-ide, evolves chlorine, and it is in this way that chlorine is produced, in countries where the acid is a waste product of the soda works, for the manufacture of the so-called chloride of lime, or bleaching powder. In this country the use of chlorine is limited, and we generally make the hydrochloric acid, and develop chlorine from it at the same time, by means of a mixture of salt, manganese binoxide, and dilute sulphuric acid, as explained in the directions for the chlorination of gold ores. The best remedy for the effects of an accidental inhalation of chlorine is, to breathe the vapor of water or alcohol, or to drink a glass of spirits.