<P> In large doses, silver and compounds containing it can be absorbed into the circulatory system and become deposited in various body tissues, leading to argyria, which results in a blue - grayish pigmentation of the skin, eyes, and mucous membranes . Argyria is rare, and so far as is known, does not otherwise harm a person's health, though it is disfiguring and usually permanent . Mild forms of argyria are sometimes mistaken for cyanosis . </P> <P> Metallic silver, like copper, is an antibacterial agent, which was known to the ancients and first scientifically investigated and named the oligodynamic effect by Carl Nägeli . Silver ions damage the metabolism of bacteria even at such low concentrations as 0.01--0.1 milligrams per litre; metallic silver has a similar effect due to the formation of silver oxide . This effect is lost in the presence of sulfur due to the extreme insolubility of silver sulfide . </P> <P> Some silver compounds are very explosive, such as the nitrogen compounds silver azide, silver amide, and silver fulminate, as well as silver acetylide, silver oxalate, and silver (II) oxide . They can explode on heating, force, drying, illumination, or sometimes spontaneously . To avoid the formation of such compounds, ammonia and acetylene should be kept away from silver equipment . Salts of silver with strongly oxidising acids such as silver chlorate and silver nitrate can explode on contact with materials that can be readily oxidised, such as organic compounds, sulfur and soot . </P>

A pure element such as silver (ag) contains only one type of