[CHAPTER XLVII.]
DISINFECTION.
By disinfection is meant the destruction of the active cause of each infectious disease. A disinfectant is therefore synonymous with a germicide. Disinfectants must be distinguished from deodorants or deodorisers, such as charcoal, and from antiseptics, which are antagonistic to the growth of bacteria, without necessarily killing them, e.g. common salt. Disinfection may be effected by chemical or physical means.
CHEMICAL DISINFECTANTS.
A chemical disinfectant should fulfil the following conditions: 1. It must be an efficient germicide. 2. Its germicidal power should not be destroyed by the fæcal or other polluting matter, with which the bacteria of infection are associated. 3. For many purposes, it must not be destructive to or liable to stain the skin, or fabrics, or other articles to which it is applied. 4. It should preferably not be a virulent poison; and should be moderately cheap. The search for a completely non-poisonous disinfectant is a chimera.
There are three great classes of chemical disinfectants.
1. Oxidising agents, as the halogens (chlorine, etc.) and permanganates.
2. Deoxidising agents, as sulphurous acid (SO₂) and formic aldehyde (CH₂O).
3. Other disinfectants, which act by coagulating protoplasm or otherwise, as carbolic acid, corrosive sublimate.
The number of disinfectants is legion. Only the chief ones can be mentioned and their chief properties described. It is a good rule to eschew the use of all disinfectants of which the exact composition is not given; and all disinfectants which are described by “fancy” names, which are not descriptive of their composition.