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. LECTURE IX. _Of Vitriolic Acid Air._ Vitriolic acid air is procured by heating in hot acid of vitriol almost any substance containing phlogiston, especially the metals which are soluble in that acid, as copper, mercury, &c. This kind of air is heavier than common air, and extinguishes a candle, but without any particular colour of its flame. It will not dislodge the nitrous or marine acids from any substance containing them. By its affinity to water it deprives borax of it. One measure of this air saturates two of alkaline air, and with it forms the vitriolic ammoniac. Water imbibes between 30 and 40 times its bulk of this air, and retains it when frozen. Water thus impregnated dissolves some metals, and thereby yields inflammable air. If this water be confined in a glass tube, together with common air, and be exposed to a long continued heat, it forms real sulphur, the dephlogisticated part of the common air being imbibed, and forming real vitriolic acid, which uniting with the phlogiston in the air, forms the sulphur. Also this air mixed with atmospheric air will, without heat, imbibe some part of it, and thereby become the common acid of vitriol; so that water impregnated with vitriolic acid air, commonly called _sulphureous_, or _phlogisticated acid of vitriol_, wants dephlogisticated air to make it the common acid of of vitriol. This kind of air is imbibed by oils, which thereby change their colour; whale oil becoming red, olive oil of an orange colour, and spirit of turpentine of the colour of amber. If this air be confined in a glass tube by mercury, and the electric spark be taken in it, a black tinge will be given to the glass contiguous to the spark, and this black substance appears to be mercury super-phlogisticated; since by exposure to air it becomes running mercury: so that the vapour of mercury must be diffused through every part of this air, to the distance of at least several feet from the surface of the mercury. _Of Fluor Acid Air._ Fluor acid air is procured by dissolving the earthy substance called _fluor_ in vitriolic acid. This kind of air extinguishes a candle, and, like vitriolic acid air, one measure of it saturates two of alkaline air. It is peculiar to this kind of air to dissolve glass when it is hot.