A. K. Vijh
and R. S. Alwitt Sprague Electric Company North Adams, Massachusetts
A Convenient Method for Sealing Metallic Wires into Glass Tubing
W e wish to draw attention to the fact that a convenient method of sealing metallic wires into glass tubing is afforded by a special, heat-shrinkable, two-layered Teflon tubing (e.g., "I'lotite" manufactured by Pope Scientific Inc., Menomnee Falls, Wis., see Fig. 1). Such a joint is mechanically sound, leakproof, and quite inert toward degreasing solvents and highly acidic or alkaline media. This procedure was recently used b y us in our studies on the mechanism of hydrogen evolution reaction on aluminum and found to be quite satisfactory. The method is particularly suitable for those cases in which it is not possible to seal satisfactorily the metallic wire directly into glass, e.g., for Al, Cd, Ph, etc. Metallic wires sealed into glass are, of course, frequently employed as electrodes for conducting either undergraduate experiments or research investigation~in the fields of electrochemical kinetics and thermodynamics. The advantage of this technique over others (e.g., masking with silicon rubber, waxes, glues, varnishes, etc.) usually employed in the preparation of, say, aluminum electrodes is that the sources of contamination are avoided. Since the present technique involves heating the glass-Teflon-metal boundary with an air gun or somc
suitable substitute, an electrode fabricated from a metal like aluminum will acquire an oxide layer. The oxide may, of course, be removed suhsequent,ly by a suitable chemipolishing or electropolishirig procedure. For metals with melting points close to or lower than 330°C (e.g., Cd, Pb), a slight modifcat,ion of the direct heating method may be employed. This v a r i d o n consists of covering with the heat-shrinkable Tcflon, not only the metal-glass boundary, but also the entire metallic electrode. The Teflon may then be heated only a t the metal glass boundary with the subsequent removal, with a sharp razor- blade, of the unheated length of the Teflon tubing (which act,s as a heat shield during sealing) enclosing the working electrode.
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TEFLON SEAL
Teflon seal connecting glass tubing and duminum wire obtained by heating "Flotite" to >330DC with an air gun.
Volume 46, Number 2, February
1969
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121
