474

FILTRATION.

to the rate of percolation, so thatthe pressure upon the porous surface may be alwaysequally great. Upon the small scale, the lamp-fountain or bird’s-glass form, so generallyused.for lamps, will be found to answer.

Fig. 386 represents a glass bottle, a, partly filled with the fluid to be filtered, supportedin the ring of a chemicai stand, and having its mouth inverted into the same liquor inthe filter funnel. It is obvious that whenever this liquor by filtration falls below thelip of the bottle, air will enter into it. let down a fresh supply to feed the filter, andkeep the funnel regularly charged. If larger quantities are to be operated upon, the

following apparatus may

386 - be employed. Fig. 387?

a B, is a metallic vesselwhich may be made air-tight ; c is the under pipe?provided witli a stopcock?r, for letting down theliquor into the filter a b •The upper pipe t , throughwhich the fluid is pouredby means of the funnel r<?has also a stopcock whichopens or shuts, at thesame time, the small sid etube u t , through which?during the entrance of thefluid, the air is let off fr oDlthe receiver. A gl aS ^tube, g, shows the Ie veof the liquor in the bod?of the apparatus. In u ^ in; Iit, the cock Rmust ben lSclosed, and the cocKmust be opened to fill *’receiver. Then the filis set a going, by re '^. P j hcing the cock r, so as to keep the fluid in the filter upon a level with the opening 0tube c. Both these pieces of apparatus are essentially the same. p.

In many manufactures, self-acting filters are fed by the plumber’s common

390 388

w

' .

which the sinking and i

ce of a ball-cock389

! which the sirup is contained

of the ball, w/thin certain

limits, serves to open orshut off the supply ofliquor, as it may be re-quired or not. Dumonthas adopted this expedientIbr his system of filteringsirup through a stratumgra.nuia.rly ground animalcharcoal or bone-black.Fig , 388 is a front viewof this apparatus with ^filters, c; and Jig. 389 is across section. The frame-work b supports the cis-* stopcock