Salt (chemistry) 27558 225633025 2008-07-14T17:30:13Z Timeroot 7362413 spelling fix {{dablink|This article is about the term '''salt''' as referred to in [[chemistry]]. For the everyday meaning, see [[salt]] or its main ingredient, [[sodium chloride]]. For other meanings of the word salt, see [[salt (disambiguation)]].}} [[Image: Halite(Salt)USGOV.jpg|thumb|A magnified crystal of a salt ([[halite]]/[[sodium chloride]])]] A '''Salt''', in [[chemistry]], is defined as the product formed from the neutralisation reaction of [[acids]] and [[base (chemistry)|bases]]. Salts are [[ionic compounds]] composed of [[cation]]s (positively [[electric charge|charged]] ions) and [[anion]]s (negative ions) so that the product is electrically [[electric charge|neutral]] (without a net charge). These component ions can be [[inorganic compound|inorganic]] such as chloride (Cl<sup>&minus;</sup>), as well as [[organic chemistry|organic]] such as [[acetate]] (CH<sub>3</sub>COO<sup>&minus;</sup>) and [[monoatomic ion]]s such as fluoride (F<sup>&minus;</sup>), as well as [[polyatomic ion]]s such as sulfate (SO<sub>4</sub><sup>2&minus;</sup>). There are several varieties of salts. Salts that produce [[hydroxide]] ions when dissolved in water are ''[[basic salts]]'' and salts that produce [[hydronium]] ions in water are ''[[acid salt]]s''. ''Neutral salts'' are those that are neither acid nor basic salts. [[Zwitterion]]s contain an anionic center and a cationic center in the same [[molecule]] but are not considered to be salts. Examples include [[amino acid]]s, many [[metabolite]]s, [[peptide]]s and [[proteins]]. When salts are dissolved in water, they are called [[electrolyte]]s, and are able to conduct [[electricity]], a property that is shared with molten salts. Mixtures of many different ions in solution—like in the [[cytoplasm]] of [[cell (biology)|cell]]s, in [[blood]], [[urine]], [[plant saps]] and [[mineral water]]s— usually do not form defined salts after evaporation of the water. Therefore, their salt content is given for the respective ions. ==Properties== [[Image:Spice 4 bg 010104.jpg|thumb|Table salt and [[peppercorns]]. ]] ===Colour=== Salts can appear to be clear and [[Transparency (optics)|transparent]] ([[sodium chloride]]), [[Opacity (optics)|opaque]], and even metallic and lustrous ([[pyrite|iron disulfide]]). In many cases the apparent [[Opacity (optics)|opacity]] or [[Transparency (optics)|transparency]] are only related to the difference in size of the individual [[monocrystal]]s. Since light reflects from the [[Crystallite|grain boundaries]] (boundaries between crystallites), larger [[crystal]]s tend to be transparent, while [[polycrystalline]] aggregates look like white powders. Of course, some salts are inherently [[Opacity (optics)|opaque]]. Salts exist in all different [[color]]s, e.g. [[yellow]] (sodium [[chromate]]), [[orange (color)|orange]] ([[potassium dichromate]]), [[red]] ([[Cinnabar|mercury sulfide]]), [[mauve]] ([[cobalt(II) chloride|cobalt chloride]] hexahydrate), [[blue]] ([[copper(II) sulfate|copper sulfate]] pentahydrate, [[Prussian blue|ferric hexacyanoferrate]]), [[green]] ([[nickel(II) oxide|nickel oxide]]), colorless ([[magnesium sulfate]]), [[white]], and [[black]] ([[Manganese(IV) oxide|manganese dioxide]]). Most [[minerals]] and inorganic [[pigment]]s as well as many synthetic organic [[dye]]s are salts. ===Taste=== Different salts can elicit all five [[basic taste]]s, e.g. salty ([[sodium chloride]]), sweet ([[lead diacetate]]; but which will cause [[lead poisoning]] if ingested), sour ([[potassium bitartrate]]), [[Bitter (taste)|bitter]] ([[magnesium sulfate]]), and [[umami]] or savory ([[monosodium glutamate]]). ===Odor=== Salts of strong acids and strong bases ("[[strong salts]]") are non-[[Volatility (chemistry)|volatile]] and odorless, while salts of either weak acids or weak bases ("[[weak salts]]") may smell after the [[conjugate acid]] (e.g. acetates like acetic acid ([[vinegar]]) and cyanides like hydrogen cyanide ([[almond]]s) or the conjugate base (e.g. ammonium salts like [[ammonia]]) of the component ions. That slow, partial decomposition is usually accelerated by presence of water, since [[hydrolysis]] is the other half of the [[reversible reaction]] equation of formation of [[weak salts]]. ==Nomenclature== [[Image:Salt_glas_hg.jpg|thumb|Various salt minerals]] [[Image:Sea_salt-e_hg.png|thumb|Chemical composition of [[sea salt]]]] The name of a salt starts with the name of the cation (e.g. ''sodium'' or ''ammonium'') followed by the name of the anion (e.g. ''chloride'' or ''acetate''). Salts are often referred to only by the name of the cation (e.g. ''sodium salt'' or ''ammonium salt'') or by the name of the anion (e.g. ''chloride'' or ''acetate''). Common salt-forming cations include: * [[ammonium]] NH<sub>4</sub><sup>+</sup> * [[calcium]] Ca<sup>2+</sup> * [[iron]] Fe<sup>2+</sup> and Fe <sup>3+</sup> * [[magnesium]] Mg<sup>2+</sup> * [[potassium]] K<sup>+</sup> * [[pyridinium]] C<sub>5</sub>H<sub>5</sub>NH<sup>+</sup> * [[Quaternary ammonium cation|quaternary ammonium]] NR<sub>4</sub><sup>+</sup> * [[sodium]] Na<sup>+</sup> Common salt-forming anions (and the name of the parent acids in parentheses) include: * [[acetate]] CH<sub>3</sub>COO<sup>&minus;</sup> ([[acetic acid]]) * [[carbonate]] CO<sub>3</sub><sup>2&minus;</sup> ([[carbonic acid]]) * [[chloride]] Cl<sup>&minus;</sup> ([[hydrochloric acid]]) * [[citrate]] HOC(COO<sup>&minus;</sup>)(CH<sub>2</sub>COO<sup>&minus;</sup>)<sub>2</sub> ([[citric acid]]) * [[cyanide]] C≡N<sup>&minus;</sup> ([[hydrogen cyanide]]) * [[hydroxide]] OH<sup>&minus;</sup> ([[water (molecule)|water]]) * [[nitrate]] NO<sub>3</sub><sup>&minus;</sup> ([[nitric acid]]) * [[nitrite]] NO<sub>2</sub><sup>&minus;</sup> ([[nitrous acid]]) * [[oxide]] O<sup>2&minus;</sup> ([[water (molecule)|water]]) * [[phosphate]] PO<sub>4</sub><sup>3&minus;</sup> ([[phosphoric acid]]) * [[sulfate]] SO<sub>4</sub><sup>2&minus;</sup> ([[sulfuric acid]]) ==Formation== Salts are formed by a [[chemical reaction]] between: * A [[base (chemistry)|base]] and an [[acid]], e.g. [[ammonia|NH<sub>3</sub>]] + [[hydrochloric acid|HCl]] → [[ammonium chloride|NH<sub>4</sub>Cl]]. * A [[metal]] and an [[acid]], e.g. [[magnesium|Mg]] + [[sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]] → [[magnesium sulfate|MgSO<sub>4</sub>]] + [[hydrogen|H<sub>2</sub>]]. * A [[base (chemistry)|base]] and an [[Oxide|acid anhydride]], e.g. 2 [[Sodium Hydroxide|NaOH]] + [[Dichlorine monoxide|Cl<sub>2</sub>O]] → 2 [[Sodium hypochlorite|NaClO]] + [[Water|H<sub>2</sub>O]] * An [[acid]] and a [[Oxide|basic anhydride]], e.g. 2 [[nitric acid|HNO<sub>3</sub>]] + [[Sodium oxide|Na<sub>2</sub>O]] → 2 [[Sodium Nitrate|NaNO<sub>3</sub>]] + [[Water|H<sub>2</sub>O]] * Salts can also form if solutions of different salts are mixed, their ions recombine, and the new salt is insoluble and precipitates (see: [[solubility equilibrium]]), for example: Pb(NO<sub>3</sub>)<sub>2</sub>(aq) + Na<sub>2</sub>SO<sub>4</sub>(aq) → PbSO<sub>4</sub>(s) + NaNO<sub>3</sub>(aq) ==References== <!--<div class="references-small"> <!--See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how to generate footnotes using the <ref(erences/)> tags- -> <references/> </div>--> * [[Mark Kurlansky]] (2002). ''Salt: A World History''. Walker Publishing Company. ISBN 0-14-200161-9. ==See also== {{wiktionary}} {{wiktionarypar|Desalt}} {{commons|Salt}} * [[Acid salt]] ''also known as'' Hydrogen salt * [[Alkali salts]] ''also known as'' Basic salt * [[Edible salt]] * [[Electrolyte]] * [[Halide]] * [[Ionic bond]]s * [[Kosher salt]] * [[Natron]] * [[Old Salt Route]] * [[Road salt]] * [[Salting the earth]] ''(the deliberate massive use of salt to render a soil unsuitable for cultivation and thus discourage habitation)'' * [[Sodium]] * [[Table salt]] * [[Zwitterion]] * [[Salinity]] * [[hypertension]] [[Category:Chemical compounds]] [[Category:Salts| ]] [[Category:Alchemical substances]] [[ar:ملح (كيمياء)]] [[az:Duzlar]] [[bg:Сол]] [[ca:Sal (química)]] [[cs:Soli]] [[da:Salt]] [[de:Salze]] [[et:Soolad]] [[el:Άλας]] [[es:Sal (química)]] [[eo:Salo]] [[fr:Sel (chimie)]] [[ko:염]] [[id:Garam (kimia)]] [[is:Sölt]] [[it:Sale]] [[he:מלח (כימיה)]] [[ka:მარილები]] [[la:Sal]] [[lt:Druska]] [[ln:Móngwa]] [[jbo:silna]] [[mk:Соли]] [[ms:Garam]] [[nl:Zouten]] [[ja:塩]] [[no:Salt]] [[nn:Salt]] [[nds:Solt]] [[pl:Sole]] [[pt:Sal]] [[qu:Kachi]] [[ru:Соли]] [[simple:Salt]] [[sq:Kripërat]] [[sl:Sol (kemija)]] [[su:Uyah (kimia)]] [[fi:Suola]] [[sv:Salt]] [[tl:Asin]] [[tr:Tuz (kimya)]] [[vi:Muối (hóa học)]] [[uk:Сіль (хімія)]] [[yi:זאלץ]] [[zh:盐]]