PERCLOSE, or DEMI-GAIITER, in heraldry, the lower half of a garter with the buckle. PERCOLATION, a process much used in pharmacy, and in some other arts, for extracting certain soluble properties of various bodies by filtering a liquid through them. In the new British pharmacopeia 39 tinctures and 9 extracts are ordered to be prepared by percolation. As the fluid soaks in and passes through the material acted upon, it displaces and carries with it the soluble parts, hence percolation is sometimes called the method of displacement. The forms of apparatus for tion are very numerous, but the principle is the same in all—viz., a vessel with a porous bottom, and in the form of a truncated cone inverted, receives the rial first, and over it is poured the water or other fluid which is to extract its virtues. One made by an nent French pharmacien, 31. Bejot, is very effective and complete. A is a long funnel-shaped glass. with a glass stop-cock (b) in the bottom, which narrows to an inch diameter; this fits into the neck of a large globular sel B, both being adjusted by grinding. C is a syringe 'of brass fixed in the glass B as shown, and made tight by a .caoutchouc washer, al, are three diaphragms of porous felt, pierced by the tube d, which allows air bubbles to escape from the bottom without disturbing the fluid. The material to he acted upon, as wood, bark, root•, leaves, etc., is first dered, and is then laid on the top of the uppermost diaphragm, al, so as to half fill the space between it and the glass-cover e; water, or any other required fluid, is then poured in until it is filled, the stop-cock b is opened, and the operator draws the air from the, outer vessel by means of the air-pump C, the fluid is thus rapidly drawn through the material, and displaces its soluble parts. a' and arrest
the Pile solid particles which are carried through the first diaphragm with the liquid, and form sediments which are also acted upon by the liquid which is checked at each divisiowfor a time. The fluid, when it reaches the globular glass, however dark colored, is beautifully bright and clear, and the preparations so made are remarkable for Omit good quality and uniformity of strength. In the year 1864 Dr. Redwood, of the phar maceutical. institution of Great Britain, invented a new percolator of great efficacy. It consists of a tinned copper cylinder, with a smaller cylinder of flannel in,side, in which the materials are put. The whole is filled with the fluid menstruum, and as that which is in more immediate contact with the solid materials becomes charged with the soluble matter displaced, it gives rise, as its density is imzeased, to an camps motic action through the flannel walls of the inner cylinder until the whole is equalized, when it is drawn off by the tap, and fresh fluid added until it collies away colorless. The outer cylinder has a tight cover to prevent loss by evaporation.