A USEFUL AIR BATH
bath. With a cover of asbestos board on the air bath practically constant temperatures up to 300' can be obtained readily by regulating the gas flame. Because ARTHUR F. SCOTT of the low loss of heat by radiation the maintenance of The Rice Institute, Houston, Texas a temperature as high as 300" requires only about a 3cm. flame from an ordinary Bunsen burner. The dimensions of the air bath are such that a 210-cc. THE present note describes the design and use of an aluminum air bath which has proved to be of consider- casserole will sink into it almost to its handle. If it is able value for individual student use in a quantitative considered advisable, direct contact between the porceanalysis class. lain and the aluminum can be prevented by means of Essentiallv the air bath is sim~lvan aluminum three thin strips of asbestos paper or cord. This arbeaker, 8.5 an.in diameter and 11.5 cm. high, inside rangement affords a convenient means of carrying out dimensions. The wall and bottom are 0.5 em. thick. the dehydration of, say, silica, for which a porcelain Beakers of this design can be cast in any foundry and casserole and a temperature of 120' are usually recommachined a t a very reasonable cost, especially if quanti- mended. ties of 100 or more are ordered to absorb the cost of the The air bath will also hold snugly a 500-cc. Berzelius casting pattern. type pyrex beaker or, with the support of a few layers When precipitates or other substances contained in of asbestos paper, a 400-cc. low-form pyrex beaker. crucibles are to be heated, the crucibles are supported The uniform heating of a solution when the containing on the usual triangles, the legs of which are bent a t beaker is in the air bath permits of more rapid and uniform evaporation than is attainable when the beaker right angles and are cut to such a length that the CNcible bottom is about 2 cm. above the floor of the air is heated only on the bottom.
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