Silver compounds were used as disinfectants. The antimicrobial use of silver has been largely supplanted by the use of antibiotics. In very finely dispersed form, silver is bactericidal, i.e. slightly toxic, which is due to the adequate formation of soluble silver ions because of the large reactive surface. In living organisms, however, silver ions usually quickly bind to sulfur and are eliminated from the metabolic cycle in the form of dark, slightly soluble silver sulfide. The effect is surface-dependent. In medicine, this is used for wound dressings and invasive devices (e.g., endotracheal tubes).[20] In general, silver is therefore used for antibacterial purposes in medical products as a coating or in colloidal form, increasingly also as nanosilver. Silver ions are used as disinfectant and as a therapeutic agent in wound therapy. They can reversibly inhibit silver-susceptible strains after a relatively long exposure time. Beyond that, they can also have bacteriostatic or even bactericidal (deadening) effect. This is called the oligodynamic effect. In some cases, chlorine compounds are added to increase the low efficacy of silver.