Lecture Viii.

Of Dephlogisticated Marine Acid Air.

This species of air is produced by heating spirit of salt with manganese; or more readily, by pouring acid of vitriol on a mixture of salt and manganese, in the proportion of about 16 of the former to 6 of the latter. In this case the acid of vitriol decomposes the salt, and the marine acid, disengaged in the form of air, takes dephlogisticated air from the manganese; so that this species of air seems to consist of marine acid vapour, and dephlogisticated air.

This species of air has a peculiarly pungent smell, and is absorbed by water as readily as fixed air.

The water takes about twice its bulk of it; and thereby acquires a yellowish tinge. Both this air, and the water impregnated with it, discharges vegetable colours from linen or cotton, and is thereby useful in bleaching.

This air when cold coagulates into a yellowish substance. It dissolves mercury, and with it forms corrosive sublimate.

Of Phlogisticated Marine Acid Air.

Besides the preceding kinds of air which are slowly absorbed by water, there are others which are absorbed by it very rapidly, so that they cannot be confined but by mercury.

Of this kind is phlogisticated marine acid air, procured by the acid of vitriol and common salt; the former seizing upon the alkaline basis of the latter, and thereby expelling the marine acid in the form of air.

It is called phlogisticated to distinguish it from dephlogisticated marine acid air, which seems to be the same thing, with the addition of dephlogisticated air.

Phlogisticated marine acid air is heavier than common air. It extinguishes a candle with a blue flame. It dissolves many substances containing phlogiston, as iron, dry flesh, &c. and thereby forms a little inflammable air. Water absorbs 360 times its bulk of this air, and is then the strongest spirit of salt. It absorbs one-sixth more than its bulk of alkaline air, and with it forms the common sal ammoniac. Its affinity to water enables it to dissolve ice, and to deprive borax, nitre, and other saline substances, of the water that enters into their composition.