To measure the body temperature is still often used mercury thermometers. Their principle of operation lies in the unique properties of amazing metal mercury. The melting point of mercury is - not hundreds of degrees, like other metals, and -38,8°C. Therefore, under normal conditions, the mercury is in a liquid state. When heated, the mercury expands and the temperature drops compressed. Mercury thermometers are very precise temperature measurement accuracy up to 0,01°C due to the high thermal conductivity of mercury and almost linear scale expansion. Other liquids that are used in thermometers - for example, alcohol and glycerol, such precision is not given.
in Addition, the mercury does not wet glass and does not stick to the glass, which make thermometers. This allows you to make the tube of the thermometer, which moves on mercury (bar), very narrow, which increases the accuracy of the instrument.
All these properties make mercury a unique working body for medical thermometers. But this metal has one important drawback - mercury and many of its compounds are extremely toxic! In Europe in 2007, mercury thermometers and sphygmomanometers were banned, but the Russians are in no hurry to switch to electronic thermometers.
If your home is accidentally broken thermometer, the main danger is spilled mercury.
It should be noted that the metallic mercury for living organisms is not dangerous. Toxic mercury ions, which are formed during its oxidation. But on the air, metallic mercury at room temperature is not oxidized. However, this does not mean that mercury, which resulted from the thermometer, not dangerous! And here's why.
We have said that mercury very low melting point - -38,8°C. And at a temperature from +18°C it begins to evaporate! And here's a pair of mercury is very toxic! Because when inhaled, they enter the lungs, where the mercury is oxidized under the influence of enzymes and in this oxidized state begins to administer their black deeds in the body.
Mercury can evaporate not only in air but also under water.
Mercury has a neurotoxic effect, i.e. the ability to destroy the nerve cells.
Acute poisoning with mercury intoxication signs begin to show in a few hours. Patients will have weakness, loss of appetite, headache, pain when swallowing, metallic taste in the mouth, much Drools gums swell and begin to bleed, there are nausea and vomiting, severe abdominal pain, diarrhea (sometimes with blood). Often develops pneumonia. In the most severe cases, after a few days of death.
But such an outcome is only possible if large quantities of mercury received by the body. However, the treachery of mercury in the fact that it is able to accumulate in the body. Therefore, when prolonged contact with toxic compounds or mercury vapor at first it may not show, but it accumulates (such property accumulation is called the cumulative effect). The man begins to feel weakness, drowsiness, it gets frequent headaches, irritability, depression, worsening memory, reduced attention and mental capacity. Gradually develops shaking fingertips with agitation (doctors call this "mercury tremor"), start failure of the heart, blood pressure decreases.
We you spoke in detail about the effects of mercury, so you know: this metal you cannot joke! 2 grams of mercury, which is contained in a single thermometer, by evaporation in a closed unventilated room area of 20 m2 is able to create the concentration of mercury vapor, thousands of times greater than the acceptable norm! A broken thermometer is unlikely to result in acute and especially chronic poisoning, but now you know that even small doses of mercury to the body is not useful. And if someone told you that he once played with balls of mercury from a broken thermometer or even swallowed one, and nothing alive" - this does not mean that mercury can be treated lightly.