(From depuro, to purify). Depuration, clarificatio, despumatio,vel rectificatio. It is the freeing of any fluid from all heterogeneous feculence, and rendering it more transparent. This operation is of three kinds: 1st. Decantation, which can only take place where there is a difference in the specific gravity hat constitutes the mixture; so that the lighter part can be poured off. When oils are to be separated from water, or indeed from other fluids, a tritorium, or separatory glass, is used. 2dly. Despumation. The principle of this mode of depuration is the existence of air in the fluid, which, when rarified by heat, rises to the top, carrying with it the feculae, which may be separated by a spoon. 3dly. Clarification', performed by adding the whites of eggs, or such fluids as will coagulate by means of heat, and entangle all the heterogene-ous matter, which may be easily separated. 4thly. Filtration or Percolation, performed by passing, without pressure, the fluid to be purified through strainers of linen, flannel, or paper, which, retaining the feculence, permit only the clearer fluid to pass. In filtration, a soft porous paper is folded in the shape of a funnel, then placed into one; and, after suffering some water to filtrate through it, to dissolve the alum, usually employed in the manufacture of the paper, the liquor is to be gradually poured on, to pass through it.
When flannel is used it is commonly formed into a cone, called Hippocrates' sleeve, and its base is hung on three props, with the apex of the cone downwards; it is then filled with the liquor, which gradually drops from the apex: it is generally used when the fluid to be depurated is hot.
Distillation and sublimation are practised in the depuration of spirits and salts, and the operation is then called rectification.