An apparatus for filtering through flannel or felt in an upward direction and under pressure of a column of the liquid suitable for filtering oils, syrups, extracts, essences, tinctures, infusions or decoctions, etc., is Warner's filter, illustrated here.

A is the reservoir containing the liquid; B, the recipient of the filtered fluid; c d, the connecting tube, and e the stop-cock. The action of the filter is explained by the engraving.

Another apparatus,, whose purpose is to exclude the air and equalize the pressure or avoid compression of air in the recipient, is shown in Fig. 382.

It consists of a glass funnel well fitted into the neck of a bottle or other recipient by means of a cork. The funne) is closed by a solid wooden cover that has on the side which closes the funnel a rubber sheet attached to ensure tight covering and exclusion of atmospheric air. The mouth of the recipient must be large enough to permit the use of a large cork, that is double perforated. In the second hole is fitted a bent glass tube; a similar one is fitted into the cover, and both are connected with. a small rubber hose which equalizes the pressure of filter and recipient.

Fig. 382.   Closed Funnel with Equalizing Device

Fig. 382. - Closed Funnel with Equalizing Device.

Fig. 883.   Plantamour's Water Bath Funnel

Fig. 883. - Plantamour's Water Bath Funnel.

Both filtering apparatus are practical devices, and very usefully employed where volatile fluids need to be filtered and clarified.

A water-bath funnel (Plantamour's) is represented by the above illustration, Fig. 383. It serves for filtering hot, saturated solutions, and will prevent the crystallization or separation of the dissolved matter while filtration is going on. Its construction is as follows: a b c is an ordinary glass funnel surrounded by a tin funnel d g k f n m h, the space between being about 3/8 of an inch; h e is a tin pipe of suitable length and 1/2 inch in diameter, soldered at h to the tin funnel; d o h r is a ring of tin, soldered to the points at d o h of the tin funnel. The diameter at r must be wide enough to permit the glass funnel to be inserted, save an eighth of an inch. At x is an opening to first supply the apparatus by the aid of small funnels with water, and secondly to allow the escape of steam. At p is a cock closing water-tight. When the apparatus is ready for operation, put a small spirit lamp under e, and the water between the two funnels will be kept boiling.