Working liquids in liquid thermometers are used to sense temperature changes, So there are three requirements for it: First, the temperature range of liquids should be wide, that is to say, its freezing point should be low and its boiling point should be high. Second, the volume expansion coefficient should be large. Third, liquids should be pure, not stained with glass, not soaked with glass.
According to the different liquids filled, liquid thermometers are divided into mercury thermometers（-30~750℃）, Alcohol thermometer （-80~80℃）, Toluene thermometer （-80~100℃） and kerosene thermometer (0- 300 ℃).
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