Bleach refers to a number of chemicals that remove color, whiten, or disinfect, often via oxidation. Common chemical bleaches include household chlorine bleach (a solution of approximately 3–6% sodium hypochlorite, NaClO), lye, oxygen bleach (which contains either hydrogen peroxide or a peroxide-releasing compound), and bleaching powder (calcium hypochlorite). The bleaching process was known to most ancient civilizations and has been around for thousands of years. Modern bleaches resulted from the work of 18th century scientists including Swedish chemist Carl Wilhelm Scheele, French scientists Claude Berthollet and Antoine Germain Labarraque, and Scottish chemist Charles Tennant. Household chlorine bleach is created in two ways: by separating sodium hypochlorite from sea water or brine using electrolysis, or by adding chlorine gas to sodium hydroxide which produces sodium hypochlorite, water and sodium chloride.
Many bleaches have strong bactericidal properties, and are used for disinfecting and sterilizing.
Examples of peroxide-releasing compounds are sodium perborate, sodium percarbonate, sodium persulfate, tetrasodium pyrophosphate, or urea peroxide together with catalysts and activators, e.g., tetraacetylethylenediamine or sodium nonanoyloxybenzenesulfonate.