Alcohol Thermometer Principle

Alcohol thermometers are replacing mercury thermometers in many applications. They employ alcohol as the filled in liquid in glass tubes. The temperature measurement range of alcohol thermometers varies from 115°C to 785°C, where former is the freezing temperature point of alcohol and latter is boiling temperature point of alcohol. A typical thermometer for getting environmental temperature readings is required to have a temperature range of -20°F to 120°F i.e. -30°C to 50°C.

Alcohol, being a volatile substance may result in parting of the column in the thermometer due to mechanical shock. The column can then be joined again by making the thermometer fall over a wooden surface enveloped with lots of paper sheets. “Hold the thermometer in a vertical position, bulb end down, 4 to 6 inches over the wood surface covered with paper, and then drop. After the thermometer bulb strikes the paper, catch the thermometer with your other hand to prevent breakage. Small amounts of alcohol may cling to the portion of the capillary tube above the alcohol column.”

High temperature portion of the thermometer can be warmed up beneath an incandescent lamp which will bring the alcohol down to the column. One can also mount the thermometer vertically for overnight which will let the drawing back of alcohol to the column. This thermometer should never be employed with a parted fluid column since it generally leads to incorrect temperature measurements.