Gold wire seals

Fig. 3.33 Catalyst cells (a) high temperature (> 600 K), flow-through, Swagelok sealed stainless steel cell and (b) high temperature gold wire sealed zirconium cell. O-ring sealed aluminium cells (c) low volume, (d) high volume and (e) flow-through, (f) Aluminium cell for off-line prepared samples (g) low temperature (<350 K) indium wire sealed aluminium cell, (h) High temperature, flow-through, Conflat sealed stainless steel cell for use on MARI, all the others are for TOSCA. The scale in the foreground is 0.3 m.

This procedure can also be applied to 5 and 10 pm platinum and gold wires (where the use of soft glass capillaries is sometimes preferred). For smaller tips (1-2 pm diameter), a Wollaston wire (a metal wire covered by a silver layer) is first placed in weak nitric acid solution to dissolve the silver layer prior to sealing the tip (Section 6.3.2). A laser puller can also be used with small diameter quartz capillaries to make submicron size electrodes (Section 6.3.3). Such sealing techniques require much practice and patience. 

A simple HMDE was developed by Gerischer [17]. Using his approach, one or two mercury drops falling from the classical DME are collected on a miniature spoon and transferred to a small metal contact sealed in glass or plastic (Fig. 14.2). Platinum or gold-plated platinum wires are used. The length of the exposed contact wire is usually 0.1-0.5 mm and its diameter is about 0.5 mm. 

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