Laundry detergent, or washing powder, is a substance which is a type of detergent that is added when one is washing laundry to help get the laundry cleaner. It is often colloquially called laundry Soap or simply detergent or Soap and it helps wash the fabric in a manner rather analogous to the way Soap helps wash hands, other parts of the body, or other things cleaner than washing with water alone. Laundry detergent has traditionally been a powdered or granular solid, but the use of liquid Laundry detergents has gradually increased over the years, and these days use of liquid detergent equals or even exceeds use of solid detergent. Some brands also manufacture laundry Soap in tablets and dissolvable packets, so as to eliminate the need to measure Soap for each load of laundry.
In the 1960s, detergent manufacturers waged an advertising battle over who had the longest lasting suds, and detergent compounds quickly appeared in the waterways. Suds began to appear in streams, rivers, lakes, and at the foot of Niagara Falls, piles of discolored detergent foam rose eight feet high.
Detergents also contain phosphate additives to soften the water and thereby improve the effectiveness of the detergent molecules. It was noted that between 1940 and 1970 the amount of phosphates in city wastewater increased from 20,000 to 150,000 tons per year.
With the increase in phosphates, algal blooms grew splendidly on the excess phosphorous and consumed the majority of all oxygen in the waters, killing fish and plants.
Uses of laundry detergent
Laundry detergent is used by almost every household in the developed world, so its production and sale has become an important industry. One can find many different brands of Laundry detergent in the shops, and each one may claim to have any number of special qualities. Each brand has its own instructions on how it should be used and what amount to use written on the container it comes in. Some brands of Laundry detergent purport to be more concentrated and can be added in smaller amounts. The detergent can be added onto the laundry or to the wash water at the start of the wash, or it can be added beforehand or soon after starting the wash into a special compartment in a washing machine made for that purpose, to be flushed into the wash by the wash water. Often bleach is a separate additive to the wash, but there are laundry detergents which have bleach already blended in with them.
All laundry detergents are soluble in water so as to make the water more effective at cleaning the laundry. The detergent does its work and is needed during the initial "Wash" cycle to separate the dirt or soil out from the fabric. The purpose of the rinses which follow is to rinse the detergent residue from the laundry as well as to remove the dirt suspended in the wash water by replacing the initial wash water with fresh water.
Separate stain pre-treatment products are sometimes available to be added directly to stained areas of fabrics. However, undiluted liquid Laundry detergent or a paste of solid detergent made by mixing in a little water may be used to pre-treat heavily soiled or stained areas of the fabric by scrubbing in the detergent prior to the wash. Special oxidizer washing products have become available in liquid or solid granular form. Such solid products often contain sodium percarbonate or sodium perborate and the liquid products often contain hydrogen peroxide. They are often marketed as containing "active oxygen". Some Laundry detergent is specially sold for delicate woolen articles.
Detergent molecules are long and the detergents can mold into different forms of matter so it can be asymmetrical: one end attracts long pieces of dirt while the other end attracts water, which is why detergent lifts dirt from wet clothes. Detergent molecules come in two forms, straight and branched - a difference that affects sudsing but not cleansing ability. The suds of the straight molecules of detergent break down quickly, while the suds of branched molecules break down slowly if at all.
A key ingredient in both solid and liquid laundry detergents is a surfactant. A surfactant is a substance which, when added to water, significantly reduces the surface tension of the water. This effect allows water to wash surfaces better. There are many different types of organic compounds which can function as surfactants. Surfactants are thick, viscous liquids; however, some are soft, waxy or greasy solids.
Surfactants typically have somewhat longer molecules which may or may not have an electric charge. Surfactants with uncharged molecules are non-ionic surfactants. Surfactants with positively charged molecules (or ions) are cationic surfactants. Surfactants with negatively charged molecules (or ions) are anionic surfactants. Surfactants with both positively and negatively charged part in the same molecule are zwitterionic surfactants. Most brands of Laundry detergent have anionic or nonionic surfactants or a mixture of the two, although cationic surfactants have been used in laundry detergents. The use of cationic and anionic surfactants together is incompatible in the same detergent. The usual content of surfactants in a typical detergent is about 8-18%.
In powdered or granular solid detergents, the surfactant is soaked into the solid ingredients. In liquid laundry detergents, liquid or even solid surfactant are blended into the liquid detergent. There is usually a limit on how much liquid surfactant can soak into powder or granular solids before making the solid detergent mushy. More liquid surfactant can usually be blended into a liquid detergent. The liquid detergents commonly contain at least some water to help liquefy the other additives and still have the detergent pour able. The liquid detergents may also have other solvent liquids, such as alcohol or a hydrotrope, to help blend all the additives together.
Laundry detergents may have ingredients to help control the pH of the wash water. For example, solid detergents usually contain sodium carbonate (soda ash) or sodium bicarbonate to maintain pH by neutralizing any acidic materials that may enter the wash water.
Compounds called "builders" are often used to enhance ("build") the surfactant effect. Their role is to lower the water hardness by scavenging the calcium and magnesium ions and adsorbing them or chelating them. Some form of sodium phosphate can be used here, such as trisodium orthophosphate, monosodium orthophosphate, or a form of tripolyphosphate (TPP). In some locations, phosphate is no longer used as an additive due to environmental concerns as phosphates in surface waters stimulate algal bloom. As alternatives, other chelating agents are used. Sodium carbonate precipitates insoluble calcium carbonate and magnesium carbonate. Organic chemicals similar to EDTA can be employed, eg. nitriloacetic acid (NTA). Borates can be used as well. Ion exchange materials are frequently used in modern formulations; the most common kind is based on synthetic zeolites, often with polycarboxylate based polyelectrolytes. The usual content of such materials in a typical detergent is about 20-45%.
Many detergents contain bleaches. In North America countries, sodium hypochlorite based bleach additives are more common. These work at lower temperatures and do not need activation. In Europe, peroxide-based bleaches are prevalent instead. The chemicals employed are usually sodium percarbonate and sodium perborate, or other compounds that release hydrogen peroxide. Peroxide bleaches either need higher temperature (60 °C or more) to become effective, or a suitable catalyst or activator (eg. manganese or iron complexes, or TAED) which lowers the required temperature down to 40 °C or even to room temperature. The usual content of bleaches in a typical detergent is about 15-30%. It is possible to overdo the bleaching; the Persil Power fiasco is a good example of deployment of too powerful bleaching activator.
The detergents promising making the laundry "whiter than white" usually contain optical brighteners, acting as phosphors converting some ultraviolet radiation to blue light and optically offsetting the yellowing of the material. The usual content of optical brighteners in a typical detergent is about 0.1%.
Fillers are a bulk component in many detergents. Their primary role is modifying the physical properties of the material. In solid detergents, sodium sulfate or borax can be used to make the powder free-flowing. In liquid detergents alcohols are added to increase the solubility of the compounds and to lower the mixture's freezing point. Corrosion inhibitors can be added to prolong the lifetime of the washing machines; sodium silicate can be used here. Anti-foaming agents are added to lower the production of foam and to make the presence of detergents in wastewater less obvious. The usual content of fillers in a typical detergent is about 5-45%.
Some laundry detergents have enzymes to help in removal of biological stains (eg. grass or blood), often enzymes produced by the bacteria Bacillus subtilis and Bacillus licheniformis. The content of enzymes can reach up to 0.75%.
Some laundry detergents have fabric softeners. Perfume or color ingredients are sometimes added for better smell or to give a detergent some color.
Other brands, however, are left without these additives, marketed to those who avoid these because of allergies or individual preference. There are also detergents made with vegetable-based surfactants which are popular in health food stores.
Containers and sizes
Solid Laundry detergent is commonly sold in cardboard boxes and plastic tubs. In many parts of the world, Laundry detergent is also sold in single-use packets. The size of the boxes can vary from small single-use boxes sold from vending machines in laundromats to large economy-size boxes. In some cases, plastic measuring scoops have been included inside the boxes. Liquid detergent is sold in plastic bottles, usually high density polyethylene or sometimes PET or other kinds. Again, various sizes are available. On large size bottles, a handle to carry the bottle is often pre-formed as part of the bottle. The bottle caps are often made large enough so they can be used as cups for measuring out the liquid detergent.
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Commoner, Barry (1971). The Closing Circle: Nature, Man, and Technology. New York, NY: Random House. ISBN 039442350X.