The vegetable fixed alkali has a strong attraction to water, with which it will become saturated in the common state of our atmosphere, when it is said to deliquesce; and having the appearance of oil, the salt of tartar is thus said to become oil of tartar per deliquium. On the other hand, the mineral, or fossil alkali, is apt to lose its water in a dry atmosphere, and then it is said to effloresce. In this state it is often found on old walls.
Volatile alkali is procured by burning animal substances; in Egypt (from whence, as contained in sal ammoniac, we till of late imported it) from camel's dung; but now from bones, by distillation. To the liquor thus procured they add vitriolic acid, or substances which contain it. This acid unites with the alkali, and common salt being put to it, a double affinity takes place. The vitriolic acid uniting with the mineral alkali of the salt, makes Glauber salt, and the marine acid uniting with the volatile alkali, makes sal ammoniac. Slaked lime added to this, unites with the marine acid of the ammoniac, and sets loose the volatile alkali in the form of alkaline air, which combining with water, makes the liquid caustic volatile alkali. If chalk (containing calcareous earth united with fixed air) be mixed with the sal ammoniac, heat will make the calcareous earth unite with the marine acid, while the fixed air of the chalk will unite with the volatile alkali, and assume a solid form, being the sal volatile of the apothecaries.
LECTURE XVII.
Of Liquid Inflammable Substances.
Of liquid inflammable substances the principal is spirit of wine, sometimes called ardent spirit, and, when highly rectified, alcohol. It is obtained from vegetable substances by their going through the vinous fermentation. It is considerably lighter than water, colourless, and transparent, has a peculiar smell and taste, and the property of inebriating.
Ardent spirit seems to consist of a peculiar combination of phlogiston and water; for when the vapour of it is made to pass through a red-hot earthen tube, it is resolved into water and inflammable air. It is highly inflammable, and burns without smoke, or leaving any residuum; and in the act of burning its phlogiston so unites with dephlogisticated air as to make fixed air.
Ardent spirit mixes readily with water in all proportions, and also with essential oils, and balsams or resins, which are the same thing inspissated.
By its affinity with essential oils, ardent spirit extracts them froth aromatic plants; and these liquors have obtained the name of tinctures.