"The percolator most suitable should be nearly cylindrical or slightly conical, with a funnel-shaped termination at the smaller end. The neck of this funnel-end should be rather short, and should gradually and regularly become narrower towards the orifice, so that a perforated cork bearing a short glass tube may be tightly wedged into it from within until the end of the cork is flush with its outer edge. The glass tube, which must not protrude above the inner surface of the cork, should extend from 1 1/8 to 1 1/2 inches (3 to 4 cm.) beyond the outer surface of the cork, and should be provided with a closely-fitting rubber tube at least one-fourth longer than the percolator itself, and ending in another short glass tube, whereby the rubber tube may be so suspended that its orifice shall be above the surface of the menstruum in the percolator, a rubber band holding it in position. The dimensions of such a percolator, conveniently holding 500 gm. of powdered material, are preferably the following: Length of body 14 inches (36 cm.); length of neck 2 inches (5 cm.); internal diameter at beginning of funnel-shaped end, 2 1/2 inches (6 1/2 cm.); internal diameter of the neck 1/2 inch (12 mm.), gradually reduced at the end to 2/5 of an inch (1 cm.). (Larger percolators, holding several times that quantity, may be usefully employed in preparing extracts for the manufacture of carbonated beverages.) They are best constructed of glass, but, unless otherwise directed, may be constructed of a different material. The percolator is prepared for percolation by gently pressing a small tuft of cotton into the space of the neck above the cork, and a small layer of clean and dry sand is then poured upon the surface of the cotton to hold it in place.

Menstruum is any fluid which is used to dissolve a solid body; a solvent or dissolvent. The principal liquids employed in the carbonator's laboratory as menstruum for preparing extracts, etc., are alcohol and water - diluted alcohol.

"Although, with proper management, good results may be obtained in the preparation of extracts and fluid extracts by using a funnel-shaped (usually termed a conical) percolator for exhausting the powder, experience has demonstrated that the so-called cylindrical percolator is to be preferred, having the shape described above, which represents the section of a long cone, and this is terminated below either by a funnel or by a shorter cone.

Fig. 384.   Glass Percolator

Fig. 384. - Glass Percolator.

Fig. 385.   Percolator with Graduated Receiver

Fig. 385. - Percolator with Graduated Receiver.

"The relative proportion of diameter to height of powder is of importance, since it is evident that with an increase of the latter the same fraction of menstruum must come into contact with the larger number of particles of the powder. Its height should be four or five times greater than its mean diameter. The cover of the percolator should not fit airtight, or, if from the volatility of the menstruum, this should be desirable, a communication should be established by means of a glass tube between the receiving vessel and the top of the percolator for the equalization of pressure. Gum-cloth furnishes a convenient material for an ordinary cover" - N. D.