Laundry detergent

Laundry detergent, or washing powder, is a type of detergent (cleaning agent) that is added for cleaning laundry. While detergent is still sold in powdered form, liquid detergents have been taking major market shares in many countries since their introduction in the 1950s.
Laundry detergent pods have also been sold in the United States since 2012 when they were introduced by Procter & Gamble as Tide Pods. Earlier instances of laundry detergent pods include Salvo tablets sold in the 1960s and 1970s.
From ancient times, chemical additives were used to facilitate the mechanical washing of clothing with water. The Italians used a mix of sulfur and water with charcoal to clean cloth. Egyptians added ashes and silicates to soften water. Soaps were the first detergents. The detergent effects of certain synthetic surfactants were noted in Germany in 1917, in response to shortages of soap during World War I. In the 1930s, commercially viable routes to fatty alcohols were developed, and these new materials were converted to their sulfate esters, key ingredients in the commercially important German brand FEWA, produced by BASF, and Dreft, the U.S. brand produced by Procter and Gamble. Such detergents were mainly used in industry until after World War II. By then, new developments and the later conversion of aviation fuel plants to produce tetrapropylene, used in household detergents, caused a fast growth of domestic use in the late 1940s.
Alkalis like soda ash precipitate hard water ions and are commonly used as builders. Additionally, they enhance washing performance. Hydrophilic fibers like cotton have a negative surface charge in water, whereas synthetic fibers are comparatively neutral. The negative charge is further increased by the adsorption of anionic surfactants. With increasing pH, soil and fibers become more negatively charged, resulting in increased mutual repulsion. This is one of the reasons why alkalis enhance wash performance, apart from effects like the saponification of fats. However, repulsive forces between soil and fibers alone do not produce satisfactory washing results even at high pH. The optimum pH range for good detergency is 9-10.5.