What are the liquids used in the thermometers and are they all of the same accuracy?
The liquids in glass thermometers vary depending on range, use and accuracy requirements. The two most common liquids are metallic mercury and various organic liquids. Mercury is a metallic element which is liquid at room temperature. It is the most reliable and repeatable of the thermometer liquids. It has a usable range from -40 to 500°C and has a linear coefficient of expansion. When mixed to form an amalgam with thallium the useable range is expanded down to approximately -58°C. When mercury is mixed with gallium, the resulting amalgam has an expanded range up to approximately 650°C. Common organic liquids are mineral spirits, kerosene, toluene, and more recently, certain citrus extract based solvents. All organic liquids need to be dyed. The common colors are red, blue and green. While most of the liquids used today are less toxic than mercury, organic liquids wet the sides of the bore causing repeatability problems. Also, they do not have linear coefficients of expansion. Therefo
