APPARATUS FOR CONTINUOUS FILTRATION. 
217 
The arrangement for continuous filtration is exceedingly simple. The ob¬ 
ject is to keep a filter constantly filled to a certain height. The rigid stand, 
a a a a, consisting of two horizontal boards connected by two uprights, 
may be replaced by any convenient laboratory fittings, its object being to 
carry a funnel-holder, b, which swings freely on a pivot, d. One arm holds 
the funnel, the other is balanced by a suitable weight, c. A vulcanized india- 
rubber tube, e e, and a wire stirrup,./, are the only other essential portions 
of the arrangement. The stirrup encircles the flexible pipe, and, passing 
through the upper board, is connected with the arm which holds the funnel. 
A wire rack, g, is added as a convenient means of regulating the pressure of 
the stirrup. 
It is obvious that if the counterpoise on the centre board is adjusted so 
that the weight of the filter when filled to the height desired will turn the 
scale, the pressure of the stirrup on the india-rubber tube will immediately 
cut off the supply. In practice it is found that the supply very soon adjusts 
itself exactly to the rate of filtration, and then the funnel remains stationary. 
The fluid may be supplied in many ways; a common washing-bottle an¬ 
swers very well, or a tap-jar may be employed, or any other similarly conve¬ 
nient appliance. The drawing shows a somewhat more complicated arrange¬ 
ment, in which the supply is brought from an open beaker by means of a si¬ 
phon, in which case the suction-pipe must be kept closed by a pinchcock. 
Washing Precipitates (Fig. 2). 
Object, to provide an intermittent supply of fluid in such a way that the 
filter shall empty itself completely before it is filled again. The same rigid 
stand, and the same oscillating funnel-board are used, but there is super- 
added another board like b, suspended in the same manner a little above it, 
as seen at h. This intermediate member holds a funnel, i, fitted with a Tan¬ 
talus siphon, immediately above the funnel used for filtering, and has a whe 
and stirrup, k, working from the opposite end. Both stirrups being raised to 
VOL. x. Q 
