33. _On a New Vegetable Acid_.—This acid is crystallizable, but the forms have not as yet been determined: it is less soluble in cold water than tartaric acid; its aqueous solution precipitates lime water in white floculi, just like tartaric acid, but the precipitate, if dissolved in muriatic acid, re-appears on adding ammonia, whilst that produced by tartaric acid does not produce this effect. The new acid has a greater affinity for lime than muriatic or nitric acids, for it precipitates the muriate and nitrate of this earth in the manner of oxalic acid, but it differs from the latter in not precipitating a solution of sulphate of lime. With potash it forms an acid salt, slightly soluble in cold water: it precipitates acetate of lead, and the precipitate holds much water in combination: the tartrate of lead, on the contrary, is anhydrous. Notwithstanding these circumstances, the equivalent number of this acid is within a few thousandths of that of tartaric acid: when distilled, it is decomposed, and produces an acid yellow liquid like tartaric acid, leaving a light charcoal burning without residuum. M. Gay Lussac is engaged in developing the chemical history of this substance.—_Bull. Univ._ A. vii. 327. 34. _Altheine, a new Vegetable Principle_.—M. Bacon gives the following directions for the preparation of this substance, which he has discovered in the _Althea officinalis_. An extract of the roots of the plant is to be made by means of cold water, and, when concentrated, [p218] acted upon by boiling alcohol: the latter will dissolve the acid malate of altheine, oil, &c.: the different alcoholic decoctions are to be put together and will throw down a crystalline deposite as they cool; the latter is to be separated and dissolved in water, and the solution, when filtered, is to be evaporated by a moderate heat, until like a syrup, and then set aside to crystallize. The crystals procured are to be washed with a small quantity of pure water, to separate the yellow matter from them, and then dried upon paper. These crystals appear, to the naked eye, like grains, needles, and feathers, but under the microscope present a hexaedral form. They are of a fine emerald green colour, transparent, brilliant, inodorous; unaltered in the air; they redden litmus paper, are soluble in water, and insoluble in alcohol. The aqueous solution of these crystals, acted upon by cold magnesia and filtered, then restores the colour of reddened litmus paper; renders syrup of violets green; and when evaporated furnishes the altheine free from malic acid. When thus pure, the substance crystallizes in regular hexaedral forms or in rhomboidal octoedrons; it affects litmus and violets as just described: it is transparent, of an emerald green colour, brilliant, inodorous, slightly sapid, unaltered by air, very soluble in water, not soluble in alcohol, soluble in acetic acid, with which it forms a crystalline salt.—_Ann. de Chimie_, xxxiv. 201.