The most important task for the thermometer is to determine the temperature at the top of the column during distillation. It is important that it is accurate at 78 °C and is a finely calibrated sprit thermometer. Graduation in whole degrees is sufficient. Always buy a well known ■^78 C brand name or it can loose accuracy after a time and you get incorrect reading and spoil the control over the process and the quality of the spirit.
The distillation apparatus functions satisfactorily without such equipment. Using equipment for automatic temperature control frees one from personally monitoring the temperature. Many types of such controls are available. A transducer is mounted in the top of the column set at 78°C. It then controls the heating or the through-cooling (using solenoid valves) if the temperature becomes too high. Normally on the Lab-Master, no electronic temperature control is necessary. Of course it can sometimes be fun and need not cost a lot. The first solution is to put a thermostat in the top of the column. The thermostat then switches of the heating current if the temperature becomes too high. In practice this is not a good solution as the system is slow to respond as the thermostat requires a few degrees before responding. Distillation ceases as the heat source takes some time to heat up again on being once more switched on. Distillation will be 50% slower. The only use for such a system is as a "safety valve". If the temperature is set a few degrees too high or rises for any reason the thermostat will stop the distillation.
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