The laboratory thermometer

Can a clinical thermometer measure boiling water or ice? No. Their temperatures are outside its range: it is made only for body temperatures. For temperatures like these we use a laboratory thermometer.

A laboratory thermometer is a long, narrow, sealed glass tube. At one end is a bulb holding a liquid. Above the bulb you can see a narrow column of the liquid inside the tube, and a Celsius scale is marked along the tube. As the temperature changes, the column rises or falls. The scale mark that the top of the column reaches is the reading.

The liquid is generally alcohol, coloured red so you can see it (plain alcohol is colourless, like water), or mercury.

The range of a thermometer runs from the lowest to the highest temperature it can measure. For the laboratory thermometer in your book, the range is −10 °C to 110 °C, which is typical.

Handle it with care: it is glass and breaks if it hits something hard. And do not hold it by the bulb.