Eugene K. Lubbs Rath Packing Company,
Research and Development Waterloo, Iowa
Device for Measuring Temperature in a Closed Rotating Flask
When heating substances in rotating heated flasks, it is nearly impossible to obtain a continuous temperature cnwe. A bulb thermometer can be placed within the flask, but it is difficult to read. A thermocouple could be used, but the flask rotation would twist the wires. Both problems can he overcome by using a slip ring and brush assembly in conjunction with a thermocouple. A copper:constantan thermocouple was inserted into a flask with the external ends bared and extending 3 4 in. past the neck of the flask. An insulating length of tygon tubing of sufficient inside diameter to insure a snug fit was slipped over the drive shaft of the motor. The bared wire ends were extended along the tygon tubing, with one wire extending ll/z in. beyond the other. Two bands of aluminum foil 3/a in. wide with a in. space between were wrapped around the tubing and wires so that each band contacted and depressed one wire. The bands were cemented in place. Leads were attached to a potentiometer and extended to the flask. The loose ends were stripped of insulation. As the flask mas rotated, touching the bared
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Journal of Chemical Educofion
potentiometer leads (copper to copper and constantan to constantan) to the rotating slip rings permitted internal temperatures to be followed continuously. The error introduced by the copper: foil: copper and constantan :foil: constantan junctions was reduced by placing the slip rings on the drive shaft where both were a t the same temperature. If more precise measurement is required, copper and constantan slip rings should be used.
