OXALIC acid, in chemistry, is found native in some acid vegetable juices, and rather plentifully in the " oxalis acetocel la," or " wood-sorrel, and in other plants of the same genus ; it is naturally united with a quantity of potash, not sufficient for complete saturation, forming what has been long known under the name of " Essential salt of sorrel!' The oxalit acid is prepared artificially by boiling a sufficient quantity of nitric acid with a variety of vegetable and animal sub stances, such as sugar, mucilage, alco hol, animal jelly, &c. Take sugar as an example : one ounce in powder is put into a retort, with three ounces of strong nitric acid. During the solution, great quantities of the nitrous acid escapes : heat is to be applied till the nitrous gas is driven off: Three ounces more of nitric acid are to be added, and the boiling continued till the fumes cease, and the colour of the liquor vanishes. Pour out the liquor into a wide shallow vessel, and, when it cools, crystals will be formed, which may be collected and dried on unsized paper. The crystals thus obtained may again be dissolved in distilled water, and evaporated, to obtain new crystals. In this way oxalic acid may be obtained from the substances above enumerated, and many others, as alcohol, gum, honey, &c. Prepared in this way, oxalic acid is in a concrete state, crystallized in four-sided prisms, termi nated in two sided summits. They are
white and transparent, and have conside rable lustre. They have a sharp taste, and change vegetable blues into a red, c .our, and produce the same effect on all vegetables, excepting indigo. The acid properties of this substance are so strong, that one part of concrete oxalic acid gives to 3,600 parts of water the pro perty of reddening paper stained with turn sole. When exposed to heat it is vola tilized, partly in a liquid, and also in a crystaline form. It cannot be decompos ed but by a very great heat. It is dell quescent in moist air and cold water dissolves about one-hall its weight of the acid : boiling water dissolves a quantity equal to its own weight. This acid is de composed 'ay the sulphuric acid with heat, and charcoal is deposited : at the boiling temperature it is decomposed by the nitric acid, and converted into water and car bonic acid: its component parts are Oxygen 77 Carbon 13 Hydrogen 10 100 It combines with alkalies, earths, and metallic oxides, and the salts thus formed are denominated oxalates. The great at traction which this acid has for lime ren ders it of great utility in detecting that substance in every soluble combination.