(From Barytes 1378 heavy,) called, from its weight, also terra ponderosa, ponderous earth.

This is not found very abundantly, or in large continued masses, but chiefly in the vicinity of mines. or veins of metal. Its species are aerated and vitriolated ponderous earth, either in the form of a transparent spar, or an opaque earth, of a white grey, or fawn colour; frequently of no regular figure,'but often in the peculiar form of a number of small convex lenses, set edgewise in the ground. We are indebted to the celebrated chemists, Gahn, Scheele, and Bergman, for our more particular knowledge of this earth; but the vitriolated barytes was mentioned so early as 1700, by Legh, in his Natural History of Lancashire, Cheshire, etc.

As this has seldom been found pure, in order to obtain it in a suitable degree of purity, we are favoured with the following process by M. I. A. Chaptal. The sulphate of barytes, or the vitriolated ponderous earth, which is its most usual combination, is pulverised and calcined in a crucible, with an eighth part of powder of charcoal: the crucible must be kept ignited during an hour; after which the calcined matter is to be thrown into water. It communicates a yellow colour to the fluid, and at the same time a strong smell of hepatic gas is perceived; the water is then to be filtered, and muriatic acid poured in; a considerable precipitate falls down, which must be separated from the fluid by filtration. The water which passes through the filter holds the muriatic barytes in solution. The carbonate of potash, or mild vegetable alkali, in solution, being then added, the ponderous earth falls down; and the carbonic acid may be driven off by calcination. The product saturated with the muriatic acid, and little more of the acid being afterwards added, supplies the terra, ponderosa muriata, or salita, which is considered as an evacuant, deobsiruent, and tonic. It is given in solution, and half a drachm is dissolved in an ounce of water. On exhibition, it has been found in small doses to in15 A 8 233 B A S crease the flow of urine, promote perspiration, open the bowels, and improve the appetite and general health. It has been considered as highly useful in scrofulous cases, chronic cutaneous complaints, and ulcerated legs. In some cancers, infarcted mesenteric glands, scirrhous testicle, buboes, asthma, and ascarides, it is said to be of advantage. Its dose is from six to ten or twenty-drops; but if ever it occasion vertigo, nausea, purging, or pains in the bowels, the dosemust be reduced, or the medicine omitted. Small doses, gradually increased, may be given twice a day, so long as they create no inconveniences. This medicine is however suspicious; and the vitriolated barytes is known to be poisonous. As the muriatic acid is but weakly retained, many substances may separate it. Even fixed air will decompose it; and in its exhibition hard water, alkaline, earthy, and metallic salts, particularly tartar emetic, should be avoided. Its irritating quality is so great, that it has produced considerable inconvenience in the more irritable constitutions and in spasmodic complaints. In scrofula, in some cutaneous diseases, and in indurated scirrhous tumours, we have found it successful; and when we have failed, have had reason to attribute the failure to the imperfect state of the medicine. Its purity may be ascertained by a little Glauber salt, or any vitriolated neutral. The smallest atom will occasion an evidently conspicuous deposition. Barytes acts on vegetable and animal substances, dissolving muscular fibres, and forming insoluble soaps with oil. For a further account see Med. Commentaries, vol. iv. and vi. dec. 2; Medical Communic. London, vol. ii. Chap-tal's, Gren's, and Thompson's Chemistry,