Liquid bleach


Liquid bleach, often called just bleach, is a common chemical household product that consists of a dilute solution of sodium hypochlorite and other secondary ingredients. It is a chlorine releasing bleaching agent widely used to whiten clothes and remove stains, as a disinfectant to kill germs, and for several other uses.
While the term has had this meaning for a long time, it may now be applied more generically to any liquid bleaching agent for laundry, irrespective of composition, such as peroxide-based bleaches.

History

was synthesized by French scientist Berthollet in 1789, by reacting chlorine gas with a solution of potassium hydroxide. He also discovered its cloth bleaching properties, and set out to commercialize it under the name of Eau de Javel after the borough of Paris where it was manufactured. It was the first product intended specifically for that application, and it shortened the process of bleaching newly made cloth from months to hours.
Scottish chemist and industrialist Charles Tennant proposed in 1798 a solution of calcium hypochlorite as an alternative for Javel water, and patented bleaching powder in 1799.
Around 1820, Antoine Labarraque substituted the much cheaper precursor sodium hydroxide for potash, thus producing Eau de Labarraque, basically the same "liquid bleach" still in use today. He also discovered its disinfectant properties, and was instrumental in spreading it worldwide for that purpose. His work greatly improved medical practice, public health, the sanitary conditions in hospitals, slaughterhouses, and all industries dealing with animal products—decades before Pasteur and others established the germ theory of disease. In particular, it led to the nearly universal practice of chlorination of tap water to prevent the spread of diseases like typhoid fever and cholera.

Composition

The active agent in liquid bleach is sodium hypochlorite, which gives the product a light greenish yellow tinge and its characteristic chlorine smell.
Formulations for household use usually contain 5% or less of sodium hypochlorite by weight. More concentrated solutions are available for industrial use.
Liquid bleach usually contains also some sodium hydroxide, intended to keep the solution alkaline. Sodium chloride is often present too, and plays no role in the product's action. Sodium chloride and hydroxide are normal residues from the main production processes.