It is the only metal that exists in liquid state at room temperature and atmospheric pressure. Melting point -38.87℃, boiling point 356.6℃, density 13.59g/cm3. The cohesion is very strong, stable in the air, evaporates mercury vapor at room temperature, and the vapor is highly toxic. Naturally occurring mercury is a mixture of seven isotopes of mercury. Mercury is slightly soluble in water and its solubility increases in the presence of air. Mercury is common in nature, general animals and plants contain trace amounts of mercury, so there are trace amounts of mercury in our food, which can be metabolized through excretion and hair.