Detergent

A detergent (as a noun) is a material intended to assist cleaning. The term is sometimes used to differentiate between soap and other surfactants used for cleaning. As an adjective pertaining to a substance, it (or "detersive") means "cleaning" or "having cleaning properties"; "detergency" indicates presence or degree of cleaning property.

Components
Detergents, especially those made for use with water, often include different components such as:

Surfactants to 'cut' (Emulsify) grease and to wet surfaces
Abrasive to scour
Substances to modify pH or to affect performance or stability of other ingredients, acids for descaling or caustics to break down organic compounds
Water softeners to counteract the effect of "hardness" ions on other ingredients
oxidants (oxidizers) for bleaching, disinfection, and breaking down organic compounds
Non-surfactant materials that keep dirt in suspension
Enzymes to digest proteins, fats, or carbohydrates in stains or to modify fabric feel
Ingredients that modify the foaming properties of the cleaning surfactants, to either stabilize or counteract foam
Ingredients to increase or decrease the viscosity of the solution, or to keep other ingredients in solution, in a detergent supplied as a water solution or gel
Ingredients that affect aesthetic properties of the item to be cleaned, or of the detergent itself before or during use, such as optical brighteners, fabric softeners, colors, perfumes, etc.
Ingredients such as corrosion inhibitors to counteract damage to equipment with which the detergent is used
Ingredients to reduce harm or produce benefits to skin, when the detergent is used by bare hand on inanimate objects or used to clean skin
Preservatives to prevent spoilage of other ingredients
Sometimes materials more complicated than mere mixtures of compounds are said to be detergent. For instance, certain foods such as celery are said to be detergent or detersive to teeth.


Types
There are several factors that dictate what compositions of detergent should be used, including the material to be cleaned, the apparatus to be used, and tolerance for and type of dirt. For instance, all of the following are used to clean glass. The sheer range of different detergents that can be used demonstrates the importance of context in the selection of an appropriate glass-cleaning agent:

a chromic acid solution—to get glass very clean for certain precision-demanding purposes such as analytical chemistry
a high-foaming mixture of surfactants with low skin irritation—for hand-washing of dishware in a sink or dishpan
any of various non-foaming compositions—for dishware in a dishwashing machine
other surfactant-based compositions—for washing windows with a squeegee, followed by rinsing
an ammonia-containing solution—for cleaning windows with no additional dilution and no rinsing
ethanol or methanol in windshield washer fluid—used for a vehicle in motion, with no additional dilution
glass contact lens cleaning solutions, which must clean and disinfect without leaving any eye-harming material that would not be easily rinsed

Terminology
Sometimes the word detergent is used to distinguish a cleaning agent from soap. During the early development of non-soap surfactants as commercial cleaning products, the term syndet, short for synthetic detergent was promoted to indicate the distinction. The term never became popular and is incorrect, because most soap is itself synthesized (from glycerides). The term soapless soap also saw a brief vogue. There is no accurate term for detergents not made of soap other than soapless detergent or non-soap detergent.

The term detergent by itself is sometimes used to refer specifically to clothing detergent, as opposed to hand soap or other types of cleaning agents.

Plain water, if used for cleaning, is a detergent. Probably the most widely-used detergents other than water are soaps or mixtures composed chiefly of soaps. However, not all soaps have significant detergency and, although the words "detergent" and "soap" are sometimes used interchangeably, not every detergent is a soap.

The term detergent is sometimes used to refer to any surfactant, even when it is not used for cleaning. This terminology should be avoided as long as the term surfactant itself is available.


History
The earliest detergent substance was undoubtedly water; after that, oils, abrasives such as wet sand, and wet clay. For the history of soap, see the entry thereon. Other detergent surfactants came from saponins and ox bile.

The detergent effects of certain synthetic surfactants were noted in 1913 by A. Reychler, a Belgian chemist. The first commercially available detergent taking advantage of those observations was Nekal,[1] sold in Germany in 1917, to alleviate World War I soap shortages. Detergents were mainly used in industry until World War II. By then new developments and the later conversion of USA aviation fuel plants to produce tetrapropylene, used in household detergents, caused a fast growth of household use, in the late 1940s.[2] In the late 1960s biological detergents, containing enzymes, better suited to dissolve protein stains, such as egg stains, were introduced in the USA by Procter & Gamble.[3]


See also
Laundry detergent
Cleavable detergent
Dispersant

External links
About.com: How Do Detergents Clean
US Patent 6472364: Detergent compositions or components