An Inexpensive, Inert Thermocouple Probe In performing experiments in the chemistry laboratory, one often needs a thermocouple probe for recording temperature measurements. An inexpensive, wide temperature range probe can be made easily from '/8-in. stsinless steel tubing commonly used for gas chromatography columns. The desired length of tnbing is threaded with 28 gauge insulated thermocouple wire. Copper versus Constantan may he used for low temperature and Chrome1 versus Alumel for higher temperatures. After forming the junction, the end of the tube may he sealed with silver solder or with soft solder leaving the t,ip of the thermocouple protrude. The wires from the open end may go to the reference junction directly or may be connected through a commercially available thermocouple quick-disconnect connector. Due to the latter, the probe is unitized, this making it virtually impossible to break off the wires. The connector also makes a convenient holder and allows easy switchingfrom one probe to another. We have used such s, probe with good results for determining phase diagrams of organic solids. The probe is inert to these materials. Due to the probe's small size, hest conduction into or away from the substance being measured by means of the probe is not a factor. A further advantage for phase diagram work is that the probe may he used to stir the solution where previously a separate device was needed.
JOHN H. MEISER
476 / Journal of Chemiml Education
