Soaps and Detergents

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For other uses, see Soaps and Detergents (disambiguation).
A collection of decorative soaps typically found in hotel rooms.
File:A bar of soap.jpg
Soap most commonly appears in bar form. This particular bar has seen some use and has lost its "bar" shape.

A detergent is a chemical compound or mixture of compounds used as a cleaning agent. A soap is a cleaning agent that is composed of one or more salts of fatty acids. In this sense, detergent is an umbrella term that includes soaps and other cleaning agents that differ in chemical composition. Even plain water, when used for cleaning, may be called a detergent.

There are, however, alternate ways in which the terms detergent and soap are used. For instance, the word detergent is often used when referring to synthetic cleaning agents that are not soaps (that is, not salts of fatty acids). Also, the word soap is applied to cleaning materials (such as "laundry soap") that do not contain salts of fatty acids.

The term is often used to differentiate between soap and other chemical surfactants used for cleaning purposes. Sometimes the word "detergent" is used in distinction to "soap."

Soap is a surfactant used in conjunction with water for washing and cleaning.

Etymology

According to one legend, "soap" takes its name from a "Mount Sapo" where ancient Romans sacrificed animals. Rain would send a mix of animal tallow and wood ash down the mountain and into the clay soil on the banks of the Tiber. Eventually, women noticed that it was easier to clean clothes with this "soap." The location of Mount Sapo is unknown, as is the source of the "ancient Roman legend" to which this tale is typically credited.[1]

In fact, the Latin word sapo simply means "soap." Borrowed from a Celtic or Germanic language, the term is cognate with Latin sebum, meaning "tallow," which appears in Pliny the Elder's account. Roman animal sacrifices usually burned only the bones and inedible entrails of the sacrificed animals; edible meat and fat from the sacrifices were taken by humans. Under such circumstances, animal sacrifices would not have included enough fat to make much soap. The legend about Mount Sapo is probably apocryphal.

History and process of soap making

File:Palmolive soap 1922 advertisement ladies home journal.jpeg
1922 magazine advertisement for Palmolive soap.

The earliest known evidence of soap use dates from 2800 B.C.E. and consists of Babylonian clay cylinders containing a soap-like substance. A formula for soap—consisting of water, alkali, and cassia oil—was written on a Babylonian clay tablet around 2200 B.C.E.

The Ebers papyrus (Egypt, 1550 B.C.E.) indicates that ancient Egyptians bathed regularly and combined animal and vegetable oils with alkaline salts to create a soap-like substance. Egyptian documents mention that a soap-like substance was used in the preparation of wool for weaving.

It is commonly reported that a soap factory with bars of scented soap was found in the ruins of Pompeii (79 C.E.). However, this report appears to be a misinterpretation of the survival of some soapy mineral substance, probably soapstone, at the Fullonica where it was used for dressing recently cleansed textiles. The ancient Romans were generally ignorant of soap's detergent properties. The word "soap" appears first in a European language in Pliny the Elder's Historia Naturalis, which discusses the manufacture of soap from tallow and ashes, but the only use he mentions for it is as a pomade for hair. He mentions rather disapprovingly that among the Gauls and Germans, men are likelier to use it than women.[2]

The Arabs made soap from vegetable oil (such as olive oil) or some aromatic oil (such as thyme oil), combined with sodium lye (Al-Soda Al-Kawia) (sodium hydroxide, NaOH). This formula continues to be used for making soap sold on the current market. From the beginning of the seventh century, soap was produced in Nablus (Palestine), Kufa (Iraq), and Basra (Iraq). Arabian soap was perfumed and colored; some soaps were liquid, others were hard. They also had special soap for shaving.

Al-Razi’s manuscript contains recipes for soap. A recently discovered manuscript from the thirteenth century details more recipes for soap making. One recipe recommends taking some sesame oil, a sprinkle of potash, alkali and some lime, mixing them together, and boiling. When cooked, they are poured into molds and left to set, leaving hard soap.

Historically, soap was made by mixing animal fats with lye. Because of the caustic nature of lye, this was a dangerous procedure, which could result in serious chemical burns or even blindness. Before the commercial production of lye became commonplace, it was produced at home for soap making from the ashes of a wood fire.

Castile soap, made from olive oil, was produced in Europe as early as the sixteenth century.

In modern times, the use of soap has become universal in industrialized nations, due to a better understanding of the role of hygiene in reducing the population of pathogenic microorganisms. Manufactured bar soaps first became available in the late nineteenth century, and advertising campaigns in Europe and the United States helped increase popular awareness of the relationship between cleanliness and health.


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Col. Enc: "Soap is a cleansing agent. It cleanses by lowering the surface tension of water, by emulsifying grease, and by absorbing dirt into the foam. ... Chemically, soaps are metallic salts of fatty acids. The manufacture of soap is based on a chemical reaction (saponification) in which an alkali acts upon a fat to form a metal salt (soap) and an alcohol (glycerol)."

"A detergent is substance that aids in the removal of dirt. Detergents act mainly on the oily films that trap dirt particles. The detergent molecules have a hydrocarbon portion, soluble in oil, and an ionic portion, soluble in water. The detergent acts as an emulsifier, i.e., by bridging the water and oil phases, it breaks the oil into tiny droplets suspended in water. The disruption of the oil film allows the dirt particles to become solubilized. Soap, the sodium salt of long-chain fatty acids, is a good detergent although it has some disadvantages, e.g., it forms insoluble compounds with certain salts found in hard water thus diminishing its effectiveness, and in acid solutions, frequently used in industry, it is decomposed (thus precipitating the free fatty acid of the soap). Synthetic detergents were first developed for commercial use in the 1950s. Detergents are classified as anionic, or negatively charged, e.g., soaps; cationic, or positively charged, e.g., tetraalkyl ammonium chloride, used as fabric softeners; nonionic, e.g., certain esters made from oil, used as degreasing agents in industry; and zwitterionic, containing both positive and negative ions on the same molecule. Detergents are incorporated in such products as dry-cleaning solutions, toothpastes, antiseptics, and solutions for removing poison sprays from vegetables and fruit."

EB:

Soap and detergent: "Soap and detergent are substances that, when dissolved in water, possess the ability to remove dirt from surfaces such as the human skin, textiles, and other solids."

Soap: "Any of a group of organic compounds that are salts of fatty acids, usually stearic acid (with 18 carbon atoms) or palmitic acid (with 16 carbon atoms). The source may be any vegetable oil or animal fat. Soaps are emulsifying agents commonly used for cleaning; they have long been made from lye and fat. Detergents are entirely synthetic and may or may not be soaps. Soaps of metals heavier than sodium are not very soluble; the curdy precipitate made by soap in hard water is the calcium or magnesium salt of the fatty acid in the soap. Heavy-metal soaps are used in lubricating greases, as gel thickeners, and in paints. Napalm is an aluminum soap."

Detergent: "Any of various surfactants (substances that reduce surface tension) used to dislodge dirt from soiled surfaces and retain it in suspension, allowing it to be rinsed away. The term usually refers to synthetic substances and excludes soaps. The characteristic features of a molecule of any detergent are a hydrophilic (water-attracting) end and a hydrophobic (oil-attracting) end. In ionic detergents, the hydrophilic property is conferred by the ionized part of the molecule. In nonionic detergents, hydrophilicity is based on the presence of multiple hydroxyl groups or other hydrophilic groups. Besides those used in water to clean dishes and laundry, detergents that function in other solvents are used in lubricating oils, gasolines, and dry-cleaning solvents to prevent or remove unwanted deposits. They are also used as emulsifying agents (see emulsion)."

Detergent: "any of various surface-active agents (surfactants) particularly effective in dislodging foreign matter from soiled surfaces and retaining it in suspension. The term usually denotes a synthetic substance that is not prepared by saponifying fats and oils (as is soap). Dishwashing and laundering of clothing are the principal applications of detergents."

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It usually comes in a solid moulded form, termed bars due to its historic and most typical shape. The use of thick liquid soap has also become widespread, especially from soap dispensers in public washrooms. Applied to a soiled surface, soapy water effectively holds particles in suspension so the whole of it can be rinsed off with clean water. In the developed world, synthetic detergents have superseded soap as a laundry aid.

Many soaps are mixtures of sodium (soda) or potassium (potash) salts of fatty acids which can be derived from oils or fats by reacting them with an alkali (such as sodium or potassium hydroxide) at 80°–100 °C in a process known as saponification. The fats are hydrolyzed by the base, yielding glycerol and crude soap. Historically, the alkali used was potassium made from the deliberate burning of vegetation such as bracken, or from wood ashes.

Soap is derived from either oils or fats. Sodium Tallowate, a common ingredient in many soaps, is in fact derived from rendered beef fat. Soap can also be made of vegetable oils, such as olive oil. Soap made entirely from such oils, or nearly so, is called castile soap.

Detergents

File:Tide display.jpg
Display of Tide on sale at a supermarket
File:Washingpowder.jpg
Laundry detergents are just only one of many possibilities of use of the detergents
File:Windex Original.jpg

Terminology for soaps and detergents

Sometimes the word "detergent" is used in distinction to "soap." For a while during the infancy of other surfactants as commercial detergent products, the term "syndet," short for "synthetic detergent" was promoted to indicate this, but never caught on very well, and is incorrect in any event because soap is itself synthesized via saponification of glycerides. The term "soapless soap" also saw a brief vogue. Unfortunately there is no accurate term for detergents not made of soap other than "soapless detergent" or "non-soap detergent."

Also, the term "detergent" is sometimes used for surfactants in general, even when they are not used for cleaning. As can be seen above, this too is terminology that should be avoided as long as the term "surfactant" itself is available.

Technically 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. Often the word "soap" is used to indicate any detergent, especially those that have characteristics similar to those of soap. It contains a glycerine molecule.

Composition of detergents

<<Much of the information on detergents was copied from: Detergents guide. Check this web site and compare.>>

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

  1. Surfactants to 'cut' grease and to wet surfaces.
  2. Abrasive to scour.
  3. Substances to modify pH or to affect performance or stability of other ingredients, acids for descaling, or caustics to destroy dirt.
  4. Water softeners are used to counteract the effect of "hardness" ions on other ingredients.
  5. Oxidizing agents (oxidizers) for bleaching and destruction of dirt.
  6. Non-surfactant materials that keep dirt in suspension.
  7. Enzymes to digest proteins, fats, or carbohydrates in dirt or to modify fabric feel.
  8. Ingredients that modify the foaming properties of the cleaning surfactants, to either stabilize or counteract foam.
  9. Additional ingredients, such as optical brighteners, softeners, colors, and perfumes.

Not only does the material to be cleaned dictate what compositions of detergent should be used, but also the apparatus to be used, and tolerance for dirt. For instance, the following are all examples of glass-cleaning agents; however, they demonstrate the importance of context in the selection of an appropriate glass-cleaning agent.

  • A chromic acid solution is used to get glass very clean for certain precision-demanding purposes, namely in analytical chemistry,
  • A high foaming mixture of surfactants with low skin irritation - for hand washing of drink glasses in a sink or dishpan,
  • Any of various non-foaming compositions - for glasses in a dishwashing machine,
  • An ammonia-containing solution - for cleaning windows with no rinsing,
  • Windshield washer fluid is used for a vehicle in motion.

Soap purification and finishing

The common process of purifying soap involves removal of sodium chloride, sodium hydroxide, and glycerol. These impurities are removed by boiling the crude soap curds in water and re-precipitating the soap with salt.

Most of the water is then removed from the soap. This was traditionally done on a chill roll which produced the soap flakes commonly used in the 1940s and 1950s. This process was superseded by spray dryers and then by vacuum dryers.

The dry soap (approximately 6-12% moisture) is then compacted into small pellets. These pellets are now ready for soap finishing. Soap finishing is the process of converting raw soap pellets into salable product, usually bars.

Soap pellets are combined with fragrances and other materials and blended to homogeneity in an amalgamator (mixer). The mass is then discharged from the mixer into a refiner which, by means of an auger, forces the soap through a fine wire screen. From the refiner the soap passes over a roller mill (French milling or hard milling) in a manner similar to calendering paper or plastic or to making chocolate liquor. The soap is then passed through one or more additional refiners to further plasticize the soap mass. Immediately before extrusion it passes through a vacuum chamber to remove any entrapped air. It is then extruded into a long log or blank, cut to convenient lengths, passed through a metal detector and then stamped into shape in refrigerated tools. The pressed bars are packaged in many ways.

Sand or pumice may be added to produce a scouring soap. This process is most common in creating soaps used for human hygiene. The scouring agents serve to remove dead skin cells from the surface being cleaned. This process is called exfoliation. Many newer materials are used for exfoliating soaps which are effective but do not have the sharp edges and pore size distribution of pumice.

Uses

Although the word soap continues to be used informally in everyday speech and product labels, in practice nearly all kinds of "soap" in use today are actually synthetic detergents, which are less expensive, more effective, and easier to manufacture. While effort has been made to reduce their negative effect upon the environment, the results have been mixed.

Soaps are useful for cleansing because soap molecules attach readily to both nonpolar molecules (such as grease or oil) and polar molecules (such as water). Although grease will normally adhere to skin or clothing, the soap molecules can attach to it as a "handle" and make it easier to rinse away. Allowing soap to sit on any surface (skin, clothes etc) over time can imbalance the moisture content on it and result in the dissolving of fabrics and dryness of skin.

(fatty end) :CH3-(CH2)n - COONa: (water soluble end)

The hydrocarbon ("fatty") portion dissolves dirt and oils, while the ionic end makes it soluble in water. Therefore, it allows water to remove normally-insoluble matter by emulsification.

Soap water can be used as a nature friendly way to get rid of an ant problem in your food. By pouring soap water on an ant trail it destroys the ant's sense of smell and the scent the ants were following to get to the food.

Handmade soap

File:Handmade soap.jpg
Handmade soap.

Some individuals continue to make soap in the home. The traditional name "soaper," for a soapmaker, is still used by those who make soap as a hobby. Those who make their own soaps are also known as soapcrafters.

The most popular soapmaking processes today is the cold process method, where fats such as olive oil react with lye. Soapmakers sometimes use the melt and pour process, where a premade soap base is melted and poured in individual molds, but this is not really to be considered soap-making. Some soapers also practice other processes, such as the historical hot process, and make special soaps such as clear soap (aka glycerin soap).

Handmade soap differs from industrial soap in that, usually, an excess of fat is used to consume the alkali (superfatting), and in that the glycerin is not removed. Superfatted soap, soap which contains excess fat, is more skin-friendly than industrial soap; though, if not properly formulated, it can leave users with a "greasy" feel to their skin. Often, emollients such as jojoba oil or shea butter are added 'at trace' (the point at which the saponification process is sufficiently advanced that the soap has begun to thicken), after most of the oils have saponified, so that they remain unreacted in the finished soap.

Disadvantages

Today, fat-based soaps have mostly been superseded by modern detergents. Washing agents do not contain soap for cleaning fabric, but for reducing foam.

The disadvantages of commercial soaps are:

  • Due to the fact that most commercial soaps eliminate the glycerine from soaps to use in other industires, this deprives the skin of the natural, moisturising glycerine and generally leaves the skin feeling dry.
  • Some antibacterial soaps have chemicals killing bacteria that coexist on the skin's surface and are essential to skin health. More alarmingly, the rise of antibacterial soaps contributes to antibiotic resistant bacteria. [citation needed]
  • Soap-based products often contain the additive sodium laureth sulfate, which research has found to be harsh on skin. This product is also present in many non-soap cleaners for personal hygiene (shampoos, bathfoams, toothpaste, etc.).
  • Soap can react mildly basically with fabrics resulting in damage over the long term. This is usually due to excess sodium hydroxide (NaOH, an alkali/base) left from manufacture, but can also be caused by the very slight presence of NaOH from the equilibrium reaction:
    R-COO-Na + H2O ↔ R-COO- + Na+ + H2O ↔ R-COOH + NaOH
    However, this equilibrium strongly favors the left-hand side so the fraction of NaOH formed is minuscule
  • Soap reacts with lime to form an insoluble deposit (soap scum) in "hard water":
    2Na+(R-COO)-(aq) + Ca2+(HCO3-)2(aq) → 2Na+(HCO3)-(aq) + Ca(R-COO)2(s) - where R stands for an alkyl group (precipitate)
  • A wide variety of emollient materials, such as shea or cocoa butters, are substantive to the skin.
  • Poorly finished soaps contain alkali (NaOH) and react mildly basically with skin and fabric; commercial products are finished to neutrality or to a weak acid content to prevent this and be more compatible with the skin's slightly acidic pH.
  • Commercial products use chelating molecules (sequestrants), often EDTA derivatives to bind with any free Ca or Mg ions and prevent soap scum. These also help reduce fragrance loss, discolouration and rancidity.
  • Castile soap has a very high alkalinity level, measured at about 9. pH of skin and hair has a slightly acidic pH level known to be about 5 to 6. Due to the high pH level, liquid castile soap is usually not recommended by soapmakers who market this high pH soap for washing hair because it is not pH-balanced and it may cause hair to become dry.

Laundry detergents

File:Tide display.jpg
A display of Tide laundry detergent at a supermarket.

Laundry detergent 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.

Use of laundry detergent

Because it is consumed when it is used, the sale of laundry detergent is a rather large business. There are many different kinds or brands of laundry detergent sold, many of them claiming some special qualities as selling points. Each brand has its own instructions on how to use it 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. The detergent is soluble in water and makes the water wash the laundry better along with agitation or tumbling. 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. Removal of certain types of stains is tough and can be achieved only with varying degrees of success. Also, 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 wool fabric.

Containers and sizes

Solid laundry detergent is commonly sold in cardboard boxes and plastic tubs. In many parts of Africa, 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.

Contents

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. Most surfactants are thick, viscous liquids, but some are soft, waxy or greasy solids. Detergent Molecules consist of:


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.

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 liquify the other additives and still have the detergent pourable. 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. Some other ingredients which solid detergents may have include sodium silicate or some form of sodium phosphate such as trisodium orthophosphate, monosodium orthophosphate, or a form of tripolyphosphate. In some locations, phosphate is no longer used as an additive due to environmental concerns.

Some laundry detergents have enzymes to help in stain removal. 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.

See also

  • Soap dispenser
  • Saponin
  • Saponification
  • Soaper
  • Glycerin soap
  • Soapmaking
  • Stainless steel soap

Notes

  1. ↑ [1]
  2. ↑ [2]

References
ISBN links support NWE through referral fees

  • Maine, Sandy (1995). The Soap Book: Simple Herbal Recipes. Interweave Press. ISBN 1-883010-14-4.
  • Tarekh Al-Masoudi\the first book. [The Masoudi History-printed in 1989 Beirut-Lebanon]
  • Much of the information on detergents was copied from: Detergents guide

External links

History

Soap making

Other

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