Bleach refers to a number of chemicals which remove color, whiten or disinfect, often via oxidation. The bleaching process has been known for thousands of years, but the chemicals currently used for bleaching resulted from the work of several 18th century scientists. Chlorine is the basis for the most commonly used bleaches, for example, the solution of sodium hypochlorite, which is so ubiquitous that many people just call it “bleach”, and calcium hypochlorite (bleaching powder).