"The process of percolation or displacement consists in subjecting a substance or substances, in powder, contained in a vessel called a percolator, to the solvent action of successive portions of menstruum' in such a manner that the liquid, as it traverses the powder in its descent to the recipient, shall be charged with the soluble portion of it, and pass from the percolator free from insoluble matter. When the process is successfully conducted, the first portion of the liquid or percolate passing through the percolator will be nearly saturated with the soluble constituents of the substance treated; and if the quantity of menstruum be sufficient for its exhaustion, the last portion will be destitute of color, odor, and taste, other than those possessed by the menstruum itself.