HEATED VACUUM MICRODESICCATORS EUGENE W. BLANK Pennsylvania State College, State College, Pennsylvania
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ICRO-PROCEDURES frequently call for the use of a desiccator. An extension of this need involves the use of a vacuum desiccator to dry difficultly crystallizable compounds. Figure 1 shows the construction of a vacuum desiccator that is simple in construction and withal efficient. The dimensions may be varied to fit the material with which the apparatus is to be constructed. A brass, or preferably aluminum, block is drilled to contain the desiccator tube and thermometer. The bent portion of the tube is filled with a suitable drying agent, usually CaCl*, and placed in the block. The aluminum block
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The material is placed in small crucibles which are supported on a wire tripod. The latter is made up of three wires soldered to small metal rings. A few glass beads are placed in the flask to prevent bumping. The drying agent is preferably P20sfor the reasons that its melting point is very high and it is strongly absorbent, thus overcoming the objection to its being influenced by the heat of the bath. The desiccator may be charged with PzOs without having i t
VACUUM MICRO-DESICCATOR
HEATEDBY MEANSOX A MICRO-BURNER APPROXDMTELY X
FIGURE 2.-DETAILS OX THE VACUUMMICRO-DESICCATOR HEATED BY MEANS OF
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may be split horizontally into two sections to admit of LIQUID-VAPOR BATE *PPRO-ATE'.YP/6 X readily removing and inserting the desiccator tube. A thin sheet of asbestos DaDer Drotects the drvinz agent from undue heating. ~ h block e is heated by means of stick to the side walls a micro-bnmer or i t may he placed on a steam-bath. Care should be taken in breaking the vacuum to by first inserting a glass prevent scattering of material by an inrush of air. tube slightly smaller than This scattering of material can be further guarded the internal diameter of against by packing the exhaust tube with cotton or the desiccator tube. glass wool. The boats, containing the material to be ~ ~ p r o ~ r iorganic a t e liquids for use in the apparatus dried, rest on a thin strip of copper metal placed in the can be selected by consulting a table of boiling points. desiccator. Since the foregoing paper was submitted, the author's Figure 2 represents an apparatus that is adapted to attention has been called to a device somewhat similar the gentle drying of materials over a long period of in principle to the second apparatus described, offered time. The use of a liquid bath requires no temperature by the Fisher Scientific Company and described in control by constant personal attention. The Laboratory, 4 , No. 1, p. 13. 189 A
