Because the human body every moment body temperature fluctuations, not fixed, but also with the surrounding environment temperature changes. And mercury thermometer 5 minutes close to the actual temperature of the body temperature, and 10 minutes, the body pulsation energy will be superimposed, it will increase the error of measurement, resulting in the measurement of 5 minutes and 10 minutes readings are not the same.
Mercury thermometer in the mercury hazard, many countries have taken measures to ban it, as early as 1992, Sweden has banned the sale of all medical devices containing mercury. Mercury pollution has attracted worldwide attention, and a legally binding international convention on mercury pollution control is likely to be introduced in June 2013 after several rounds of intergovernmental negotiations.
Expanded Information:
A mercury thermometer. p>A mercury thermometer contains about 1 gram of mercury. When it is broken, all of the leaked mercury evaporates, which can bring the air mercury concentration in a room 15 square meters large and 3 meters high to 22 .2 milligrams per cubic meter. China has set the maximum allowable concentration of mercury in indoor air at 0.01 mg/m3. It is generally believed that a person can quickly become mercury poisoned in an environment with a mercury concentration of 1.2-8.5 milligrams per cubic meter.
But the use of mercury thermometers has not been banned in China. Mercury thermometers are widely used in the medical field and in ordinary households, and are available in some pharmacies. Data from the China Medical Devices Industry Association show that in 2008, the country's production of mercury thermometers consumed 109.25 tons of mercury, equivalent to 21.85 billion standard mercury-containing energy-saving lamps.
Baidu Encyclopedia - Mercury Thermometer