Mercury thermometers usually measure for five minutes. Before using the mercury thermometer, you need to shake the mercury mercury column to below 35 ℃, and then place the mercury end of the thermometer at the top of the armpit, that is, deep in the armpit, and clamp the thermometer with the upper arm to avoid dislocation and fall. After five minutes of measurement, take out the thermometer, read the temperature data, and then wipe it clean with toilet paper for the next time or for others to use. To take a reading, hold the end of the thermometer in one hand, that is, away from the end of the mercury column, so that the eyes and the thermometer to maintain the same level, and then slowly rotate the thermometer, from the front to see a very thick column of mercury, you can read out the corresponding temperature value. When reading, never touch the water temperature end of the thermometer with your hand, as this will affect the mercury column and cause inaccurate measurement.