Biological Properties of Mercury

Mercury and mercurial compounds, applied in the form of an ointment, have an irritating local action on the skin. Taken internally they have a strong toxic action, producing nausea, colic, and salivation. They bring about a sudden fall in blood- pressure, paralysis of respiration, and sometimes serious cardiac disturbances. The most rapid effect is produced by inhalation of mercury vapour. In cases of mercurial poisoning the metal accumulates to the highest concentration in the liver. Mercury vapours and compounds are also toxic to plants. Owing to their toxic effect on bacteria, mercury compounds, especially mercuric chloride, are used as antiseptics. They are also used medicinally.

The physiological effect is considered to be due to the mercury ion. The toxic action of corrosive sublimate has been ascribed to the ion HgCl₄''. The ionisable mercury compounds are more poisonous than the non-ionising organic mercury compounds, and the addition of sodium chloride, for example, which represses the ionisation, reduces the toxic action. It has also been found that the antiseptic power of mercury is greatest in solutions of hydrion concentration 10^-5-10^-6.6, whilst solutions of concentration 10^-7.8-10^-10.1 are unfavourable to the action. That is, the antiseptic solution should be feebly acid rather than feebly alkaline.