A TECHNIQUE FOR VACUUM FILTRATION JAMES R. BROWN Veterans Administration Research Hospital, Chicago, Illinois
THEmethod described herepermits'one to filter with suction directly into a variety of receivers, thus avoiding the need to transfer from a suction flask or to rinse down a filtering adapter. The advantage of such a technique is that less glassware is dirtied and the filtrate need not be diluted unnecessarily. The figure shows the arrangement used. The essential point is the use of moderately rigid sponge rubber (not foam rubher) with smooth surfaces to make a tight connection between the bell jar and the receiver. A set of squares is prepared, each with a different size hole, cut with large cork borers. Before use, the upper surface may be wetted with water to improve the seal. The bell jar is supported a t the neck with a buret extension clamp (not shown). As receivers, we have used round bottom flasks of 500 or more ml. capacity and graduated cylinders 50 to 1000 ml. in capacity. Smaller containers are more conveniently used with the hell jar and the usual glass plate, or with a larger .. jar (New Cat' No' 35070).
VOLUME 34, NO. 4, APRIL, 1957
A. Bllehner funnel. B, Rubber cone filtering adapter (A. H. Thomas Co.. No. 5115-T). C,Filter bell jar (Corning Glass Works. Cat. No. 6880). D, Sponge rubber. a/' in. thiok, medium grade. 5 X 5 in. E., Extension ring, steel. 3 in. inside diameter (Fisher Saientific Co.. Cat. No. 14-055). Cat.
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