QUALITIES. _Form_, Crystals of considerable size, whose primary form is an oblique rhombic prism; they do not deliquesce when exposed to the air, but melt at a heat a little exceeding 212°. _Taste_, very acid and agreeable. SOLUBILITY. Water at 60° dissolves about one-fifth of its weight, and when boiling, a much greater proportion. The solution, which, if saturated, has the specific gravity 1·230, acquires, when diluted, like that of most vegetable acids, a mouldy pellicle by keeping. The saturating power of crystallized tartaric acid is almost exactly equal to that of crystallized citric acid, the atomic weight of the former being 76, and that of the latter 75. CHEMICAL COMPOSITION. When uncombined with water, as it exists in tartrate of potass, it is composed of 5 atoms of oxygen, 3 atoms of hydrogen, and 4 atoms of carbon. The crystals consist of 1 atom of acid and 1 of water. INCOMPATIBLE SUBSTANCES. Alkalies, Earths, and their carbonates; the salts of lime and lead. The solutions of the salts of potass are converted by it into bi-tartrate, or super-tartrate. MEDICINAL USES. It is introduced into the Pharmacopœia as a cheap and efficient substitute for the citric acid. It is also used in the preparation of _Sodaic powders_, _Seidlitz powders_, &c. ADULTERATIONS. When carelessly prepared it will contain sulphuric acid, to detect which, let a portion be dissolved in distilled water, and a solution of acetate of lead be added. A precipitate will appear which, if the acid be pure, will be entirely redissolved by a few drops of acetic acid, or pure nitric acid. If any portion remain undissolved, sulphuric acid is the cause. Muriate of Baryta also, when sulphuric acid is present, but not otherwise, gives a precipitate insoluble by an excess of muriatic acid.
ACONITI FOLIA. L.E.D. (_Aconitum Napellus._[355]) _Aconite._
QUALITIES. _Taste_, moderately bitter, and acrid, leaving in the mouth a painful sensation of heat and roughness, followed by numbness in the gums and lips which continues for two or three hours. _Odour_, faint and narcotic; their peculiar properties are considerably deteriorated by drying. CHEMICAL COMPOSITION. M. Brandes has ascertained that the narcotic principle of this plant is a peculiar alkali, to which he has given the name _Aconita_.[356] SOLUBILITY, water and alcohol only imperfectly extract their virtues. MEDICINAL USES. It is narcotic, and occasions, in over-doses, nausea, vomiting, vertigo, hyper-catharsis, cold sweats, convulsions, and death; effects which entirely depend upon its action on the brain. It was first administered in 1702, by Stöerk, of Vienna, in chronic rheumatism, gout, schirrus, and paralysis; more lately it has been employed in scrofula, cancer, and intermittents, and it is said with much effect. On account of the variable strength of the leaves they can hardly be given with safety and effect; the extract (_which see_,) presents the more eligible form of exhibition. The leaves are, however, sometimes given in the form of powder, generally combined with some mercurial alterative, or with antimonials, camphor, and other diaphoretics. DOSE gr. i-x. OFFICINAL PREP: _Extractum Aconiti._ L.E.