A Low-Cost Temperature Controlled Oil Bath Inexpensive hrnting bath3 have been described in the lnerature wh~rhutilirvd rheortat or Variac contn&d heating element immersed in an i d . ' \Ye have used such baths in t h pa% ~ but were dissatisfied with the inherent temperature fluctuations. As an alternative to the commercially available thermostatically controlled baths, we have been using the simple oil baths with a thermoswitch temperature control in series with the power supply and resistive element load. Fenwal, Inc. series 17000 thermoswitches give excellent results. They offer a temperature ranee of -73-2M°C for brass encased switches and -73-316°C for stainless steel models. A screw typc wmperature adjuitmenr mn be set rc, n ip~cificwmpemrurt. using n Hr i n glass rhermornrtcr as ;I refcrrnre. 'l'he typical varlnnre h r our inrulattd, well stirred baths ir fD .PCrhnnwhuut a 2,5 20n0(! working mncc With a line adjustment 01 [he puwer supply, augmented with rht l~uilt m "antlcipatim chararteriitic"of the tlxmwsuitch, uvershoot is grcalv mmimirrd and flurtuntam\ of lesr t h o O.RD(' an b ~ ~ c h i e w d . l'he thermoswitch p~rturedi i the tmss modd 17010-0. I t has normally cloaed contacts and srllr fur about S:N 'l'he convenient imction strw afixed to the wall of t h ? rrsstalli*ar~ondish is made by bolting a terminal strip t& Hoffman Jamp. Asbestoa cloth insulation which normally engulfs the dish has been removed for clarity. ~
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1 Darlage,
L. J., and King, S. J., J. CHEM. EDUC., 53,774 (1976).
University of Wisconsin-Milwaukee Milwaukee. 53201
R. L. Sehneider
Volume 55. Number 10. October 1978 1 671
