Mercury at room temperature is a silvery-white, odourless liquid with a high surface tension (forms convex globules on most surfaces) and a surprisingly high volatility.
Mercury vapour is non-flammable but very poisonous if inhaled; it can also enter the body by absorption through the skin but at quite a low rate.
Mercury has a profound effect on the central nervous system ranging from fatigue, irritability, tremors, impaired cognitive skills and sleep disturbances to vision and hearing impairment, renal impairment and psychotic reactions (e.g. hallucinations, delirium, suicidal tendency); the seriousness of the effect depending on the concentration and duration of the exposure.
Although mercury was commonly used in dental amalgams, thermometers and batteries, due to its toxicity, its use in these areas has largely been phased out. It still plays a major part in the processing of gold and silver ores and is still used widely in mercury vapour lamps.