A Micro Filter The qualitative organic analysis student must frequently filter small amounts of materials. The author has found the following inexpensive micro filter, which can be assembled by the student, to be more convenient for handling very small samples than a Hirsh funnel. Although micro filters using the flat end of a capillary tube as a support plate have been described by Fieser' and Wiberg,2 the micro filter described here is simpler to construct and easier to nse. The glass body of the filter is cut from 6 to 10 mm od glass capillary tubing. If no glass saw is available, -FILTER PAPER the flat end can he obtained by scoring -PLASTIC TUBING and breaking. Any high spots should be removed with a file. RUBBER STOPPER Both ends should he fire polished. The +FILTER FLASK short length of polyethylene tubing should be heated in boiline water and slipped over the capillary tuhing. If it is installed over two layers of cellophane tape, which is re-
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moved after the polyethylene cools, a sliding fit will result. The sleeve can then be pushed down over the glass capillary tubing after a filtration to permit easy removal of a precipitate. If the rubber stopper is installed "upside down" so that it seals flat against the top of the filter flask, the unit will be much easier to remove from the flask than if the stopper seats in the flask in the usual way. Filter paper discs can be cut with an ordinary paper punch. This work was supported by the University Research Institute of The University of Texas at El Paso.
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FIESEE,L. F., "Experiments in Organic Chemistry," ( h d ed.), D. C. Heath and Co., Boston, 1941, Part 11, p. 332; FIESER, L F., "Experiments in O r g a ~ 0Chemistry," (3rd ed.), D. C. Heath and Co., Boston, 1957, p. 259. a WIBERQ, K. B., "Lahoratary Technique in Organic Chemistry," McGraw-Hill Book Co., Inc., New York, 1960, p. 108.
Volume
45, Number 2, February 1968
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115
