MARCH, 1953
139
A VACUUM DRYING APPARATUS FOR SMALL SAMPLES JOHN D. REINHEIMER The College of Wwster, Wooster, Ohio
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Fisher Pistol has been the standard apparatus for vacuum drying of small samples. This piece of apparatus is rather difficult to construct, and the solvents which are required are often lacking or contaminated when needed. A substitute for the traditional apparatus is an electrically heated Pyrex tube. This piece of apparatus may he constructed by a glass blower of moderate skill; it requires no solvents and may be permitted to run safely overnight. The illustration shows the equipment which has been used for a year. I t has been run for periods up to 24 hours, and at temperatures up to 100°C. Its construction requires materials which are readily available to any laboratory. CONSTRUCTION
Materials: Pyrex tube 34 mm. O.D.; a standardtaper 35/40 joint; 30 feet of nichrome wire, B & S No. 22; variable resistance of 200-250 ohms; a Pyrex second layer of damp asbestos is then wrapped over three-way stopcock; sheet asbestos; ring stands; and secured as was the first. The asbestos-wrapped tube is then dried in an oven a t 110' for about 24 clamps; wire gauze; and a board for a base. The asbestos sheet is first wrapped about the Pyrex hours. The wire gauze is bent into the shape shown in the tube and secured by three copper wires. The nichrome wire is then wramed about the tube, 10 turns per inch. picture to serve as a vial carrier. This olaces the vial and the ends &e fastened with bopper wire. ~ h bin the center of theheated tube.
