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98-472: Soap is a salt of a fatty acid (sometimes other carboxylic acids) used for cleaning and lubricating products as well as other applications. In a domestic setting, soaps, specifically "toilet soaps", are surfactants usually used for washing , bathing , and other types of housekeeping . In industrial settings, soaps are used as thickeners , components of some lubricants , emulsifiers , and catalysts . Soaps are often produced by mixing fats and oils with

196-497: A base . Humans have used soap for millennia; evidence exists for the production of soap-like materials in ancient Babylon around 2800 BC. In a domestic setting, "soap" usually refers to what is technically called a toilet soap, used for household and personal cleaning. Toilet soaps are salts of fatty acids with the general formula ( RCO 2 )M, where M is Na (sodium) or K (potassium). When used for cleaning, soap solubilizes particles and grime, which can then be separated from

294-483: A rheology modifier. Metal soaps can be prepared by neutralizing fatty acids with metal oxides: A cation from an organic base such as ammonium can be used instead of a metal; ammonium nonanoate is an ammonium-based soap that is used as an herbicide. Another class of non-toilet soaps are resin soaps , which are produced in the paper industry by the action of tree rosin with alkaline reagents used to separate cellulose from raw wood. A major component of such soaps

392-403: A base. This is also true of some compounds with ionic character, typically oxides or hydroxides of less-electropositive metals (so the compound also has significant covalent character), such as zinc oxide , aluminium hydroxide , aluminium oxide and lead(II) oxide . Electrostatic forces between particles are strongest when the charges are high, and the distance between the nuclei of the ions

490-488: A hard or soft form because of an understanding of lye sources. It is uncertain as to who was the first to invent true soap. Knowledge of how to produce true soap emerged at some point between early mentions of proto-soaps and the first century AD. Alkali was used to clean textiles such as wool for thousands of years but soap only forms when there is enough fat, and experiments show that washing wool does not create visible quantities of soap. Experiments by Sally Pointer show that

588-660: A major cottage industry, with sources in Nablus , Fes , Damascus , and Aleppo . Soapmakers in Naples were members of a guild in the late sixth century (then under the control of the Eastern Roman Empire ), and in the eighth century, soap-making was well known in Italy and Spain. The Carolingian capitulary De Villis , dating to around 800, representing the royal will of Charlemagne , mentions soap as being one of

686-477: A minimum quantity of one imperial ton at each boiling, which placed the process beyond the reach of the average person. The soap trade was boosted and deregulated when the tax was repealed in 1853. Industrially manufactured bar soaps became available in the late 18th century, as advertising campaigns in Europe and America promoted popular awareness of the relationship between cleanliness and health. In modern times,

784-415: A network with long-range crystalline order. Many other inorganic compounds were also found to have similar structural features. These compounds were soon described as being constituted of ions rather than neutral atoms , but proof of this hypothesis was not found until the mid-1920s, when X-ray reflection experiments (which detect the density of electrons), were performed. Principal contributors to

882-453: A paste and then heated to a temperature where the ions in neighboring reactants can diffuse together during the time the reactant mixture remains in the oven. Other synthetic routes use a solid precursor with the correct stoichiometric ratio of non-volatile ions, which is heated to drive off other species. In some reactions between highly reactive metals (usually from Group 1 or Group 2 ) and highly electronegative halogen gases, or water,

980-591: A pleasant smell was produced in the Middle East during the Islamic Golden Age , when soap-making became an established industry. Recipes for soap-making are described by Muhammad ibn Zakariya al-Razi (c. 865–925), who also gave a recipe for producing glycerine from olive oil . In the Middle East, soap was produced from the interaction of fatty oils and fats with alkali . In Syria , soap

1078-416: A potential energy well with minimum energy when the nuclei are separated by a specific equilibrium distance. If the electronic structure of the two interacting bodies is affected by the presence of one another, covalent interactions (non-ionic) also contribute to the overall energy of the compound formed. Salts are rarely purely ionic, i.e. held together only by electrostatic forces. The bonds between even

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1176-400: A reducing agent such as carbon) such that the metal ions gain electrons to become neutral atoms. According to the nomenclature recommended by IUPAC , salts are named according to their composition, not their structure. In the most simple case of a binary salt with no possible ambiguity about the charges and thus the stoichiometry , the common name is written using two words. The name of

1274-529: A role in determining the strength of the interactions and propensity to melt. Even when the local structure and bonding of an ionic solid is disrupted sufficiently to melt it, there are still strong long-range electrostatic forces of attraction holding the liquid together and preventing ions boiling to form a gas phase. This means that even room temperature ionic liquids have low vapour pressures, and require substantially higher temperatures to boil. Boiling points exhibit similar trends to melting points in terms of

1372-460: A salt usually have multiple near neighbours, so they are not considered to be part of molecules, but instead part of a continuous three-dimensional network. Salts usually form crystalline structures when solid. Salts composed of small ions typically have high melting and boiling points , and are hard and brittle . As solids they are almost always electrically insulating , but when melted or dissolved they become highly conductive , because

1470-498: A shorter wavelength when they are involved in more covalent interactions. This occurs during hydration of metal ions, so colorless anhydrous salts with an anion absorbing in the infrared can become colorful in solution. Salts exist in many different colors , which arise either from their constituent anions, cations or solvates . For example: Some minerals are salts, some of which are soluble in water. Similarly, inorganic pigments tend not to be salts, because insolubility

1568-418: A similar substance was used in the preparation of wool for weaving. In the reign of Nabonidus (556–539 BC), a recipe for a soap-like substance consisted of uhulu [ashes], cypress [oil] and sesame [seed oil] "for washing the stones for the servant girls". True soaps, which we might recognise as soaps today, were different to proto-soaps. They foamed, were made deliberately, and could be produced in

1666-457: A small soap works in Warrington in 1886 and founded what is still one of the largest soap businesses, formerly called Lever Brothers and now called Unilever . These soap businesses were among the first to employ large-scale advertising campaigns. Liquid soap was invented in the nineteenth century; in 1865, William Sheppard patented a liquid version of soap. In 1898, B.J. Johnson developed

1764-400: A soap derived from palm and olive oils; his company, the B.J. Johnson Soap Company , introduced " Palmolive " brand soap that same year. This new brand of soap became popular rapidly, and to such a degree that B.J. Johnson Soap Company changed its name to Palmolive . In the early 1900s, other companies began to develop their own liquid soaps. Such products as Pine-Sol and Tide appeared on

1862-496: A soap manufactory. The method of extraction proceeded on a discovery of Keir's. In 1790, Nicolas Leblanc discovered how to make alkali from common salt . Andrew Pears started making a high-quality, transparent soap, Pears soap , in 1807 in London. His son-in-law, Thomas J. Barratt , became the brand manager (the first of its kind) for Pears in 1865. In 1882, Barratt recruited English actress and socialite Lillie Langtry to become

1960-464: A soap-like substance was written on a Sumerian clay tablet around 2500 BC. This was produced by heating a mixture of oil and wood ash , the earliest recorded chemical reaction, and used for washing woolen clothing. The Ebers papyrus (Egypt, 1550 BC) indicates the ancient Egyptians used a soap-like product as a medicine and created this by combining animal fats or vegetable oils with a soda ash substance called trona . Egyptian documents mention

2058-483: A surfactant, when lathered with a little water, soap kills microorganisms by disorganizing their membrane lipid bilayer and denaturing their proteins . It also emulsifies oils, enabling them to be carried away by running water. When used in hard water , soap does not lather well but forms soap scum (related to metallic soaps , see below). So-called metallic soaps are key components of most lubricating greases and thickeners. A commercially important example

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2156-527: A variety of structures are commonly observed, and theoretically rationalized by Pauling's rules . In some cases, the anions take on a simple cubic packing and the resulting common structures observed are: Some ionic liquids , particularly with mixtures of anions or cations, can be cooled rapidly enough that there is not enough time for crystal nucleation to occur, so an ionic glass is formed (with no long-range order). Within any crystal, there will usually be some defects. To maintain electroneutrality of

2254-626: A wide variety of uses and applications. Many minerals are ionic. Humans have processed common salt (sodium chloride) for over 8000 years, using it first as a food seasoning and preservative, and now also in manufacturing, agriculture , water conditioning, for de-icing roads, and many other uses. Many salts are so widely used in society that they go by common names unrelated to their chemical identity. Examples of this include borax , calomel , milk of magnesia , muriatic acid , oil of vitriol , saltpeter , and slaked lime . Soluble salts can easily be dissolved to provide electrolyte solutions. This

2352-495: Is lithium stearate . Greases are usually emulsions of calcium soap or lithium soap and mineral oil . Many other metallic soaps are also useful, including those of aluminium , sodium , and mixtures thereof. Such soaps are also used as thickeners to increase the viscosity of oils. In ancient times, lubricating greases were made by the addition of lime to olive oil , which would produce calcium soaps. Metal soaps are also included in modern artists' oil paints formulations as

2450-483: Is K). When one of the ions already has a multiplicative prefix within its name, the alternate multiplicative prefixes ( bis- , tris- , tetrakis- , ...) are used. For example, Ba(BrF 4 ) 2 is named barium bis(tetrafluoridobromate) . Compounds containing one or more elements which can exist in a variety of charge/ oxidation states will have a stoichiometry that depends on which oxidation states are present, to ensure overall neutrality. This can be indicated in

2548-462: Is a curved blade with a handle, all of which is made of metal. The 2nd-century AD physician Galen describes soap-making using lye and prescribes washing to carry away impurities from the body and clothes. The use of soap for personal cleanliness became increasingly common in this period. According to Galen, the best soaps were Germanic, and soaps from Gaul were second best. Zosimos of Panopolis , circa 300 AD, describes soap and soapmaking. In

2646-407: Is a simple way to control the concentration and ionic strength . The concentration of solutes affects many colligative properties , including increasing the osmotic pressure , and causing freezing-point depression and boiling-point elevation . Because the solutes are charged ions they also increase the electrical conductivity of the solution. The increased ionic strength reduces the thickness of

2744-400: Is highest in polar solvents (such as water ) or ionic liquids , but tends to be low in nonpolar solvents (such as petrol / gasoline ). This contrast is principally because the resulting ion–dipole interactions are significantly stronger than ion-induced dipole interactions, so the heat of solution is higher. When the oppositely charged ions in the solid ionic lattice are surrounded by

2842-447: Is more skin-friendly than one without extra fat, although it can leave a "greasy" feel. Sometimes, an emollient is added, such as jojoba oil or shea butter . Sand or pumice may be added to produce a scouring soap. The scouring agents serve to remove dead cells from the skin surface being cleaned. This process is called exfoliation . To make antibacterial soap, compounds such as triclosan or triclocarban can be added. There

2940-535: Is named iron(2+) sulfate (with the 2+ charge on the Fe ions balancing the 2− charge on the sulfate ion), whereas Fe 2 (SO 4 ) 3 is named iron(3+) sulfate (because the two iron ions in each formula unit each have a charge of 3+, to balance the 2− on each of the three sulfate ions). Stock nomenclature , still in common use, writes the oxidation number in Roman numerals (... , −II, −I, 0, I, II, ...). So

3038-495: Is reputed for its particular mildness. The term "Castile" is also sometimes applied to soaps from a mixture of oils with a high percentage of olive oil. Proto-soaps, which mixed fat and alkali and were used for cleansing, are mentioned in Sumerian , Babylonian and Egyptian texts. The earliest recorded evidence of the production of soap-like materials dates back to around 2800 BC in ancient Babylon. A formula for making

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3136-548: Is required for fastness. Some organic dyes are salts, but they are virtually insoluble in water. Salts can elicit all five basic tastes , e.g., salty ( sodium chloride ), sweet ( lead diacetate , which will cause lead poisoning if ingested), sour ( potassium bitartrate ), bitter ( magnesium sulfate ), and umami or savory ( monosodium glutamate ). Salts of strong acids and strong bases (" strong salts ") are non- volatile and often odorless, whereas salts of either weak acids or weak bases (" weak salts ") may smell like

3234-414: Is small. In such cases, the compounds generally have very high melting and boiling points and a low vapour pressure . Trends in melting points can be even better explained when the structure and ionic size ratio is taken into account. Above their melting point, salts melt and become molten salts (although some salts such as aluminium chloride and iron(III) chloride show molecule-like structures in

3332-401: Is some concern that use of antibacterial soaps and other products might encourage antimicrobial resistance in microorganisms. The type of alkali metal used determines the kind of soap product. Sodium soaps, prepared from sodium hydroxide , are firm, whereas potassium soaps, derived from potassium hydroxide , are softer or often liquid. Historically, potassium hydroxide was extracted from

3430-509: Is sometimes left in the soap product as a softening agent, although it is sometimes separated. Handmade soap can differ from industrially made soap in that an excess of fat or coconut oil beyond that needed to consume the alkali is used (in a cold-pour process, this excess fat is called "superfatting"), and the glycerol left in acts as a moisturizing agent. However, the glycerine also makes the soap softer. The addition of glycerol and processing of this soap produces glycerin soap . Superfatted soap

3528-551: Is the formation of an F-center , a free electron occupying an anion vacancy. When the compound has three or more ionic components, even more defect types are possible. All of these point defects can be generated via thermal vibrations and have an equilibrium concentration. Because they are energetically costly but entropically beneficial, they occur in greater concentration at higher temperatures. Once generated, these pairs of defects can diffuse mostly independently of one another, by hopping between lattice sites. This defect mobility

3626-410: Is the sodium salt of abietic acid . Resin soaps are used as emulsifiers. The production of toilet soaps usually entails saponification of triglycerides , which are vegetable or animal oils and fats. An alkaline solution (often lye or sodium hydroxide ) induces saponification whereby the triglyceride fats first hydrolyze into salts of fatty acids. Glycerol (glycerin) is liberated. The glycerin

3724-421: Is the source of most transport phenomena within an ionic crystal, including diffusion and solid state ionic conductivity . When vacancies collide with interstitials (Frenkel), they can recombine and annihilate one another. Similarly, vacancies are removed when they reach the surface of the crystal (Schottky). Defects in the crystal structure generally expand the lattice parameters , reducing the overall density of

3822-411: Is the summation of the interaction of all sites with all other sites. For unpolarizable spherical ions, only the charges and distances are required to determine the electrostatic interaction energy. For any particular ideal crystal structure, all distances are geometrically related to the smallest internuclear distance. So for each possible crystal structure, the total electrostatic energy can be related to

3920-525: The Arabic word al-qāly , القلوي ) is a basic , ionic salt of an alkali metal or an alkaline earth metal . An alkali can also be defined as a base that dissolves in water . A solution of a soluble base has a pH greater than 7.0. The adjective alkaline , and less often, alkalescent , is commonly used in English as a synonym for basic, especially for bases soluble in water. This broad use of

4018-482: The Kapustinskii equation . Using an even simpler approximation of the ions as impenetrable hard spheres, the arrangement of anions in these systems are often related to close-packed arrangements of spheres, with the cations occupying tetrahedral or octahedral interstices . Depending on the stoichiometry of the salt, and the coordination (principally determined by the radius ratio ) of cations and anions,

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4116-416: The anhydrous material. Molten salts will solidify on cooling to below their freezing point . This is sometimes used for the solid-state synthesis of complex salts from solid reactants, which are first melted together. In other cases, the solid reactants do not need to be melted, but instead can react through a solid-state reaction route . In this method, the reactants are repeatedly finely ground into

4214-405: The conjugate acid (e.g., acetates like acetic acid ( vinegar ) and cyanides like hydrogen cyanide ( almonds )) or the conjugate base (e.g., ammonium salts like ammonia ) of the component ions. That slow, partial decomposition is usually accelerated by the presence of water, since hydrolysis is the other half of the reversible reaction equation of formation of weak salts. Salts have long had

4312-580: The electrical double layer around colloidal particles, and therefore the stability of emulsions and suspensions . The chemical identity of the ions added is also important in many uses. For example, fluoride containing compounds are dissolved to supply fluoride ions for water fluoridation . Solid salts have long been used as paint pigments, and are resistant to organic solvents, but are sensitive to acidity or basicity. Since 1801 pyrotechnicians have described and widely used metal-containing salts as sources of colour in fireworks. Under intense heat,

4410-435: The electronegative halogens gases to salts. Salts form upon evaporation of their solutions . Once the solution is supersaturated and the solid compound nucleates. This process occurs widely in nature and is the means of formation of the evaporite minerals. Insoluble salts can be precipitated by mixing two solutions, one with the cation and one with the anion in it. Because all solutions are electrically neutral,

4508-618: The Mediterranean olive-growing regions. Hard toilet soap was introduced to Europe by Arabs and gradually spread as a luxury item. It was often perfumed. By the 15th century, the manufacture of soap in Christendom often took place on an industrial scale, with sources in Antwerp , Castile , Marseille , Naples and Venice . In France, by the second half of the 16th century, the semi-industrialized professional manufacture of soap

4606-537: The Southern Levant , the ashes from barilla plants , such as species of Salsola , saltwort ( Seidlitzia rosmarinus ) and Anabasis , were used to make potash . Traditionally, olive oil was used instead of animal lard throughout the Levant, which was boiled in a copper cauldron for several days. As the boiling progresses, alkali ashes and smaller quantities of quicklime are added and constantly stirred. In

4704-494: The Tudor period that barrels of ashes were imported for the manufacture of soap. Finer soaps were later produced in Europe from the 17th century, using vegetable oils (such as olive oil ) as opposed to animal fats. Many of these soaps are still produced, both industrially and by small-scale artisans. Castile soap is a popular example of the vegetable-only soaps derived from the oldest "white soap" of Italy. In 1634 Charles I granted

4802-658: The anion and cation. This difference in electronegativities means that the charge separation, and resulting dipole moment, is maintained even when the ions are in contact (the excess electrons on the anions are not transferred or polarized to neutralize the cations). Although chemists classify idealized bond types as being ionic or covalent, the existence of additional types such as hydrogen bonds and metallic bonds , for example, has led some philosophers of science to suggest that alternative approaches to understanding bonding are required. This could be by applying quantum mechanics to calculate binding energies. The lattice energy

4900-511: The anions and net positive charge of the cations. There is also a small additional attractive force from van der Waals interactions which contributes only around 1–2% of the cohesive energy for small ions. When a pair of ions comes close enough for their outer electron shells (most simple ions have closed shells ) to overlap, a short-ranged repulsive force occurs, due to the Pauli exclusion principle . The balance between these forces leads to

4998-407: The article being cleaned. The insoluble oil/fat "dirt" become associated inside micelles , tiny spheres formed from soap molecules with polar hydrophilic (water-attracting) groups on the outside and encasing a lipophilic (fat-attracting) pocket, which shields the oil/fat molecules from the water, making them soluble. Anything that is soluble will be washed away with the water. In hand washing , as

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5096-632: The ashes of bracken or other plants. Lithium soaps also tend to be hard. These are used exclusively in greases . For making toilet soaps, triglycerides (oils and fats) are derived from coconut, olive, or palm oils, as well as tallow . Triglyceride is the chemical name for the triesters of fatty acids and glycerin . Tallow, i.e., rendered fat, is the most available triglyceride from animals. Each species offers quite different fatty acid content, resulting in soaps of distinct feel. The seed oils give softer but milder soaps. Soap made from pure olive oil , sometimes called Castile soap or Marseille soap ,

5194-462: The atoms can be ionized by electron transfer , a process thermodynamically understood using the Born–Haber cycle . Salts are formed by salt-forming reactions Ions in salts are primarily held together by the electrostatic forces between the charge distribution of these bodies, and in particular, the ionic bond resulting from the long-ranged Coulomb attraction between the net negative charge of

5292-406: The case of lard, it required constant stirring while kept lukewarm until it began to trace. Once it began to thicken, the brew was poured into a mold and left to cool and harden for two weeks. After hardening, it was cut into smaller cakes. Aromatic herbs were often added to the rendered soap to impart their fragrance, such as yarrow leaves, lavender , germander , etc. A detergent similar to soap

5390-590: The cation (the unmodified element name for monatomic cations) comes first, followed by the name of the anion. For example, MgCl 2 is named magnesium chloride , and Na 2 SO 4 is named sodium sulfate ( SO 4 , sulfate , is an example of a polyatomic ion ). To obtain the empirical formula from these names, the stoichiometry can be deduced from the charges on the ions, and the requirement of overall charge neutrality. If there are multiple different cations and/or anions, multiplicative prefixes ( di- , tri- , tetra- , ...) are often required to indicate

5488-558: The compound is the result of a reaction between a strong acid and a weak base , the result is an acid salt . If it is the result of a reaction between a strong base and a weak acid , the result is a base salt . If it is the result of a reaction between a strong acid and a strong base, the result is a neutral salt. Weak acids reacted with weak bases can produce ionic compounds with both the conjugate base ion and conjugate acid ion, such as ammonium acetate . Some ions are classed as amphoteric , being able to react with either an acid or

5586-462: The constituent ions, or the hydrated form of the same compound. The anions in compounds with bonds with the most ionic character tend to be colorless (with an absorption band in the ultraviolet part of the spectrum). In compounds with less ionic character, their color deepens through yellow, orange, red, and black (as the absorption band shifts to longer wavelengths into the visible spectrum). The absorption band of simple cations shifts toward

5684-533: The context of chemistry and chemical engineering . There are various, more specific definitions for the concept of an alkali. Alkalis are usually defined as a subset of the bases. One of two subsets is commonly chosen. The second subset of bases is also called an " Arrhenius base ". Alkali salts are soluble hydroxides of alkali metals and alkaline earth metals , of which common examples are: Soils with pH values that are higher than 7.3 are usually defined as being alkaline. These soils can occur naturally due to

5782-406: The counterions can be chosen to ensure that even when combined into a single solution they will remain soluble as spectator ions . If the solvent is water in either the evaporation or precipitation method of formation, in many cases the ionic crystal formed also includes water of crystallization , so the product is known as a hydrate , and can have very different chemical properties compared to

5880-861: The crystal. Defects also result in ions in distinctly different local environments, which causes them to experience a different crystal-field symmetry , especially in the case of different cations exchanging lattice sites. This results in a different splitting of d-electron orbitals , so that the optical absorption (and hence colour) can change with defect concentration. Ionic compounds containing hydrogen ions (H ) are classified as acids , and those containing electropositive cations and basic anions ions hydroxide (OH ) or oxide (O ) are classified as bases . Other ionic compounds are known as salts and can be formed by acid–base reactions . Salts that produce hydroxide ions when dissolved in water are called alkali salts , and salts that produce hydrogen ions when dissolved in water are called acid salts . If

5978-464: The crystals, defects that involve loss of a cation will be associated with loss of an anion, i.e. these defects come in pairs. Frenkel defects consist of a cation vacancy paired with a cation interstitial and can be generated anywhere in the bulk of the crystal, occurring most commonly in compounds with a low coordination number and cations that are much smaller than the anions. Schottky defects consist of one vacancy of each type, and are generated at

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6076-483: The development of a theoretical treatment of ionic crystal structures were Max Born , Fritz Haber , Alfred Landé , Erwin Madelung , Paul Peter Ewald , and Kazimierz Fajans . Born predicted crystal energies based on the assumption of ionic constituents, which showed good correspondence to thermochemical measurements, further supporting the assumption. Many metals such as the alkali metals react directly with

6174-521: The electrons in the metal ions or small molecules can be excited. These electrons later return to lower energy states, and release light with a colour spectrum characteristic of the species present. In chemical synthesis , salts are often used as precursors for high-temperature solid-state synthesis. Many metals are geologically most abundant as salts within ores . To obtain the elemental materials, these ores are processed by smelting or electrolysis , in which redox reactions occur (often with

6272-569: The electrostatic energy of unit charges at the nearest neighboring distance by a multiplicative constant called the Madelung constant that can be efficiently computed using an Ewald sum . When a reasonable form is assumed for the additional repulsive energy, the total lattice energy can be modelled using the Born–Landé equation , the Born–Mayer equation , or in the absence of structural information,

6370-502: The examples given above would be named iron(II) sulfate and iron(III) sulfate respectively. For simple ions the ionic charge and the oxidation number are identical, but for polyatomic ions they often differ. For example, the uranyl(2+) ion, UO 2 , has uranium in an oxidation state of +6, so would be called a dioxouranium(VI) ion in Stock nomenclature. An even older naming system for metal cations, also still widely used, appended

6468-445: The ions become completely mobile. For this reason, molten salts and solutions containing dissolved salts (e.g., sodium chloride in water) can be used as electrolytes . This conductivity gain upon dissolving or melting is sometimes used as a defining characteristic of salts. In some unusual salts: fast-ion conductors , and ionic glasses , one or more of the ionic components has a significant mobility, allowing conductivity even while

6566-469: The ions become mobile. Some salts have large cations, large anions, or both. In terms of their properties, such species often are more similar to organic compounds. In 1913 the structure of sodium chloride was determined by William Henry Bragg and William Lawrence Bragg . This revealed that there were six equidistant nearest-neighbours for each atom, demonstrating that the constituents were not arranged in molecules or finite aggregates, but instead as

6664-446: The liquid phase). Inorganic compounds with simple ions typically have small ions, and thus have high melting points, so are solids at room temperature. Some substances with larger ions, however, have a melting point below or near room temperature (often defined as up to 100 °C), and are termed ionic liquids . Ions in ionic liquids often have uneven charge distributions, or bulky substituents like hydrocarbon chains, which also play

6762-789: The market, making the process of cleaning things other than skin, such as clothing, floors, and bathrooms, much easier. Liquid soap also works better for more traditional or non-machine washing methods, such as using a washboard . Salt (chemistry) The component ions in a salt can be either inorganic , such as chloride (Cl ), or organic , such as acetate ( CH 3 COO ). Each ion can be either monatomic (termed simple ion ), such as sodium (Na ) and chloride (Cl ) in sodium chloride , or polyatomic , such as ammonium ( NH 4 ) and carbonate ( CO 3 ) ions in ammonium carbonate . Salts containing basic ions hydroxide (OH ) or oxide (O ) are classified as bases , for example sodium hydroxide . Individual ions within

6860-399: The material as a whole remains solid. This is often highly temperature dependent, and may be the result of either a phase change or a high defect concentration. These materials are used in all solid-state supercapacitors , batteries , and fuel cells , and in various kinds of chemical sensors . The colour of a salt is often different from the colour of an aqueous solution containing

6958-454: The milder soaps used by the Gauls around 58 BC. Aretaeus of Cappadocia , writing in the 2nd century AD, observes among "Celts, which are men called Gauls, those alkaline substances that are made into balls [...] called soap ". The Romans' preferred method of cleaning the body was to massage oil into the skin and then scrape away both the oil and any dirt with a strigil . The standard design

7056-427: The most electronegative / electropositive pairs such as those in caesium fluoride exhibit a small degree of covalency . Conversely, covalent bonds between unlike atoms often exhibit some charge separation and can be considered to have a partial ionic character. The circumstances under which a compound will have ionic or covalent character can typically be understood using Fajans' rules , which use only charges and

7154-440: The name by specifying either the oxidation state of the elements present, or the charge on the ions. Because of the risk of ambiguity in allocating oxidation states, IUPAC prefers direct indication of the ionic charge numbers. These are written as an arabic integer followed by the sign (... , 2−, 1−, 1+, 2+, ...) in parentheses directly after the name of the cation (without a space separating them). For example, FeSO 4

7252-503: The name to the element potassium , which was first derived from caustic potash, and also gave potassium its chemical symbol K (from the German name Kalium ), which ultimately derived from al k ali. Alkalis are all Arrhenius bases , ones which form hydroxide ions (OH ) when dissolved in water. Common properties of alkaline aqueous solutions include: The terms "base" and "alkali" are often used interchangeably, particularly outside

7350-586: The newly formed Society of Soapmakers a monopoly in soap production who produced certificates from 'foure Countesses, and five Viscountesses, and divers other Ladies and Gentlewomen of great credite and quality, besides common Laundresses and others', testifying that 'the New White Soap washeth whiter and sweeter than the Old Soap'. During the Restoration era (February 1665 – August 1714) a soap tax

7448-467: The opposite pole of a polar molecule, the solid ions are pulled out of the lattice and into the liquid. If the solvation energy exceeds the lattice energy , the negative net enthalpy change of solution provides a thermodynamic drive to remove ions from their positions in the crystal and dissolve in the liquid. In addition, the entropy change of solution is usually positive for most solid solutes like salts, which means that their solubility increases when

7546-502: The poster-girl for Pears soap, making her the first celebrity to endorse a commercial product. William Gossage produced low-priced, good-quality soap from the 1850s. Robert Spear Hudson began manufacturing a soap powder in 1837, initially by grinding the soap with a mortar and pestle . American manufacturer Benjamin T. Babbitt introduced marketing innovations that included the sale of bar soap and distribution of product samples . William Hesketh Lever and his brother, James , bought

7644-628: The products the stewards of royal estates are to tally. The lands of Medieval Spain were a leading soapmaker by 800, and soapmaking began in the Kingdom of England about 1200. Soapmaking is mentioned both as "women's work" and as the produce of "good workmen" alongside other necessities, such as the produce of carpenters, blacksmiths, and bakers. In Europe, soap in the 9th century was produced from animal fats and had an unpleasant smell. This changed when olive oil began to be used in soap formulas instead, after which much of Europe's soap production moved to

7742-407: The relative compositions, and cations then anions are listed in alphabetical order. For example, KMgCl 3 is named magnesium potassium trichloride to distinguish it from K 2 MgCl 4 , magnesium dipotassium tetrachloride (note that in both the empirical formula and the written name, the cations appear in alphabetical order, but the order varies between them because the symbol for potassium

7840-556: The repeated laundering of materials used in perfume -making lead to noticeable amounts of soap forming. This fits with other evidence from Mesopotamian culture. Pliny the Elder, whose writings chronicle life in the first century AD, describes soap as "an invention of the Gauls". The word sapo , Latin for soap, has connected to a mythical Mount Sapo, a hill near the River Tiber where animals were sacrificed. But in all likelihood,

7938-448: The size of ions and strength of other interactions. When vapourized, the ions are still not freed of one another. For example, in the vapour phase sodium chloride exists as diatomic "molecules". Most salts are very brittle . Once they reach the limit of their strength, they cannot deform malleably , because the strict alignment of positive and negative ions must be maintained. Instead the material undergoes fracture via cleavage . As

8036-418: The sizes of each ion. According to these rules, compounds with the most ionic character will have large positive ions with a low charge, bonded to a small negative ion with a high charge. More generally HSAB theory can be applied, whereby the compounds with the most ionic character are those consisting of hard acids and hard bases: small, highly charged ions with a high difference in electronegativities between

8134-420: The sodium chloride structure (coordination number 6), and less again than those with a coordination number of 4. When simple salts dissolve , they dissociate into individual ions, which are solvated and dispersed throughout the resulting solution. Salts do not exist in solution. In contrast, molecular compounds, which includes most organic compounds, remain intact in solution. The solubility of salts

8232-790: The solvent, so certain patterns become apparent. For example, salts of sodium , potassium and ammonium are usually soluble in water. Notable exceptions include ammonium hexachloroplatinate and potassium cobaltinitrite . Most nitrates and many sulfates are water-soluble. Exceptions include barium sulfate , calcium sulfate (sparingly soluble), and lead(II) sulfate , where the 2+/2− pairing leads to high lattice energies. For similar reasons, most metal carbonates are not soluble in water. Some soluble carbonate salts are: sodium carbonate , potassium carbonate and ammonium carbonate . Salts are characteristically insulators . Although they contain charged atoms or clusters, these materials do not typically conduct electricity to any significant extent when

8330-403: The substance is solid. In order to conduct, the charged particles must be mobile rather than stationary in a crystal lattice . This is achieved to some degree at high temperatures when the defect concentration increases the ionic mobility and solid state ionic conductivity is observed. When the salts are dissolved in a liquid or are melted into a liquid , they can conduct electricity because

8428-573: The suffixes -ous and -ic to the Latin root of the name, to give special names for the low and high oxidation states. For example, this scheme uses "ferrous" and "ferric", for iron(II) and iron(III) respectively, so the examples given above were classically named ferrous sulfate and ferric sulfate . Common salt-forming cations include: Common salt-forming anions (parent acids in parentheses where available) include: Alkali In chemistry , an alkali ( / ˈ æ l k ə l aɪ / ; from

8526-422: The surfaces of a crystal, occurring most commonly in compounds with a high coordination number and when the anions and cations are of similar size. If the cations have multiple possible oxidation states , then it is possible for cation vacancies to compensate for electron deficiencies on cation sites with higher oxidation numbers, resulting in a non-stoichiometric compound . Another non-stoichiometric possibility

8624-399: The temperature increases. There are some unusual salts such as cerium(III) sulfate , where this entropy change is negative, due to extra order induced in the water upon solution, and the solubility decreases with temperature. The lattice energy , the cohesive forces between these ions within a solid, determines the solubility. The solubility is dependent on how well each ion interacts with

8722-413: The temperature is elevated (usually close to the melting point) a ductile–brittle transition occurs, and plastic flow becomes possible by the motion of dislocations . The compressibility of a salt is strongly determined by its structure, and in particular the coordination number . For example, halides with the caesium chloride structure (coordination number 8) are less compressible than those with

8820-514: The term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base, and they are still among the most common bases. The word alkali is derived from Arabic al qalīy (or alkali ), meaning ' the calcined ashes ' (see calcination ), referring to the original source of alkaline substances. A water-extract of burned plant ashes, called potash and composed mostly of potassium carbonate ,

8918-413: The two solutions mixed must also contain counterions of the opposite charges. To ensure that these do not contaminate the precipitated salt, it is important to ensure they do not also precipitate. If the two solutions have hydrogen ions and hydroxide ions as the counterions, they will react with one another in what is called an acid–base reaction or a neutralization reaction to form water. Alternately

9016-526: The use of soap has become commonplace in industrialized nations due to a better understanding of the role of hygiene in reducing the population size of pathogenic microorganisms . Until the Industrial Revolution , soapmaking was conducted on a small scale and the product was rough. In 1780, James Keir established a chemical works at Tipton , for the manufacture of alkali from the sulfates of potash and soda, to which he afterwards added

9114-645: The word was borrowed from an early Germanic language and is cognate with Latin sebum , " tallow ". It first appears in Pliny the Elder 's account, Historia Naturalis , which discusses the manufacture of soap from tallow and ashes. There he mentions its use in the treatment of scrofulous sores , as well as among the Gauls as a dye to redden hair which the men in Germania were more likely to use than women. The Romans avoided washing with harsh soaps before encountering

9212-400: Was concentrated in a few centers of Provence — Toulon , Hyères , and Marseille —which supplied the rest of France. In Marseilles, by 1525, production was concentrated in at least two factories, and soap production at Marseille tended to eclipse the other Provençal centers. English manufacture tended to concentrate in London. The demand for high-quality hard soap was significant enough during

9310-469: Was introduced in England, which meant that until the mid-1800s, soap was a luxury, used regularly only by the well-to-do. The soap manufacturing process was closely supervised by revenue officials who made sure that soapmakers' equipment was kept under lock and key when not being supervised. Moreover, soap could not be produced by small makers because of a law that stipulated that soap boilers must manufacture

9408-473: Was manufactured in ancient China from the seeds of Gleditsia sinensis . Another traditional detergent is a mixture of pig pancreas and plant ash called zhuyizi ( simplified Chinese : 猪胰子 ; traditional Chinese : 豬胰子 ; pinyin : zhūyízǐ ). Soap made of animal fat did not appear in China until the modern era. Soap-like detergents were not as popular as ointments and creams. Hard toilet soap with

9506-423: Was mildly basic. After heating this substance with calcium hydroxide ( slaked lime ), a far more strongly basic substance known as caustic potash ( potassium hydroxide ) was produced. Caustic potash was traditionally used in conjunction with animal fats to produce soft soaps , one of the caustic processes that rendered soaps from fats in the process of saponification , one known since antiquity. Plant potash lent

9604-464: Was produced using olive oil together with alkali and lime . Soap was exported from Syria to other parts of the Muslim world and to Europe. A 12th-century document describes the process of soap production. It mentions the key ingredient, alkali , which later became crucial to modern chemistry, derived from al-qaly or "ashes". By the 13th century, the manufacture of soap in the Middle East had become

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