Medicinales, vel Mixerales. Medicinal, or Mineral waters.

Waters which contain minerals in solution are distinguished by the name mineral waters; but as there is no water found in nature, even among the purest, unim-pregnated by some of these substances, the name of mineral waters ought to be confined to such as are sufficiently impregnated to produce a sensible effect on the animal economy, so as to cure or prevent the disorders to which it is liable; hence the term medicinal is more applicable. They participate more or less of the matters over which they run in their subterraneous passages, and from some prevailing ingredient they receive their names.

The substances which are contained in waters are either held by suspension or solution; by the first are meant clay, silex,.(quartzose, vitrifiable earth,) in a state of division; calcareous earth; and magnesia. By the second, air of different kinds; the carbonic acid; pure, or compound alkalis; lime, magnesia, the sulphates, muriates, the extractive matters of plants, hepatic gas, etc. Silex, however, is often contained in waters, apparently dissolved by means which we cannot understand or imitate. Though the most ancient, the most general, and the most simple division of mineral waters is into cold, hot, or thermal waters, accordingly as their temperature is the same with, or exceeds that of common water.

Modern chemists of allowed abilities have arranged all mineral waters into four classes; called gaseous, saline, sulphureous, and ferruginous waters.

The acidulous are the most common and best known of the gaseous waters, and are those in which the carbonic acid air abounds; known by their sharp penetrating taste, the facility with which they afford bubbles by simple agitation, or even by mere standing, the property of turning the tincture of turnsole red, and precipitating lime water and liver of sulphur. These are divisible into two orders, cold and hot; the first comprehending cold, acidulous, and alkaline waters, such as Seltzer, St. Myon, Bard, &c; in England, Tilbury and Clifton. The second, hot or thermal, acidulous, alkaline waters, as those of Mount d'or.

This ingredient in mineral waters was first discovered in the Pyrmont waters by Dr. Brownrigg. There are few waters without it; but unless at least six inches of this air are found in 100 of the water, it is scarcely medicinal. The Pyrmont water contains from about 150 to 187 inches in 100. In general, water at the temperature of 60° can take little more than its own bulk, unless when pure alkalis, with which it can combine, be present. It is incompatible only with alkaline air.

Azote was first discovered in the Buxton waters by Dr. Pearson, and it has been suspected in the Bath waters. Dr. Garnet found it in those of Harrow-gate; and Mr. Lambe (Manchester Mem. vol. v.) in those of Lemington Priors.

Common air was discovered by Mr. Boyle in waters of every kind, but this does not render them medicinal. Oxygen air was first discovered in water by Scheele, but has not since been found in any other instance. Indeed the medicinal waters, whose obvious qualities force them on our notice, can scarcely ever contain oxygen, since it cannot unite with water containing hepatic air or ferruginous salts. We know not that this is ever medicinal, for oxygenous air in the stomach is injurious. Hydrogenous air seems never to exist alone in water, though it may be suspected in the waters of marshes; but it is a solvent of sulphur, and, with it. forms a common ingredient in sulphureous waters. When combined to saturation it is styled by Berthollet, the sulphurated hydrogen; and, when united to a basis, hydrosulphuret. When the sulphur is in excess, it is hydrogenated sulphur of Berthollet; and, with a basis, hydrogenated sulphure; more conveniently, the supersulphurated hydrosulphuret. Mr. Kirwan calls these combinations, respectively, hepatic air, or super-sulphurated hydrogen, hepatules, and hepars. Of the hepatic air, water takes up about two-thirds or three-fourths of its bulk; by agitation, or heating the water, a greater quantity is absorbed. Heavy inflammable air, or carbonated hydrogen, exists seemingly in some volcanic waters, but has not been ascertained by direct experiment. Sulphureous, or vitriolic air, is also contained in the hot waters of Italy connected with volcanoes. It is apparently the excess of the vitriolic acid in the ferrugineous waters, and has been usually referred to that head.

The saline waters consist of a numerous group of the acid, alkaline, earthy, and neutral saline springs. As we have just seen the excess of vitriolic acid forming its peculiar air, so the excess of the acid itself is sometimes found in the vitriolated and aluminous waters. The muriatic acid has not yet been found except in a state of combination, unless Dr. Wethering's suspicion of its existing in the waters of Nevil Holt should be realized; (Translation of Bergman's Sciagraphia). The boracic acid has, as we shall show, been found in some Italian lakes: in a combined state we have always received it as a natural production from the lakes of Persia and Thibet, under the name of tinkal. The nitrous acid exists only in a combined state, and we recollect of this only one instance, viz. at Bihor in Hungary. See Annales de Chimie, vol. i. p. 224.

Of the alkalis, the natron is most abundant in mineral waters, and it is found in an aerated state. The quantity of this salt in almost every region of the earth is considerable; and it forms a striking and convincing proof, that the waters of the ocean once covered the face of the earth; for the natron is, in almost every situation, evidently the fixed residuum of decomposed sea salt. In the natron lakes of Egypt it is accompanied with the sea salt, and the same admixture occurs in many mineral waters. Sea water has not been usually reckoned among mineral waters; it is however highly deserving of this distinction: and we cannot avoid noticing in this place a curious fact lately published, which, if confirmed, will greatly illustrate our subject, viz. that the Galvanic spark passed through water produces an impregnation of sea salt. In the progress of our publication we shall again advert to the fact, should further experiments either confirm or oppose it. In the interval between writing and printing this paragraph, it has received additional confirmation.