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-An '''electrolyte''' is a substance that ionizes when dissolved in suitable ionizing [[solvent]]s such as [[Properties of water|water]]. This includes most soluble salts, [[acid]]s, and [[Base (chemistry)|bases]]. Some gases, such as [[hydrogen chloride]], under conditions of high temperature or low pressure can also function as electrolytes. Electrolyte solutions can also result from the dissolution of some biological (e.g., [[DNA]], [[polypeptides]]) and [[synthetic polymer]]s (e.g., [[polystyrene sulfonate]]), termed [[polyelectrolyte]]s, which contain charged [[functional group]]s.
-Electrolyte solutions are normally formed when a salt is placed into a solvent such as water and the individual components dissociate due to the thermodynamic interactions between solvent and solute molecules, in a process called [[solvation]]. For example, when table salt ([[sodium chloride]]), NaCl, is placed in water, the [[salt]] (a solid) dissolves into its component ions, according to the dissociation reaction
-:NaCl<sub>(s)</sub> → Na<sup>+</sup><sub>(aq)</sub> + Cl<sup>−</sup><sub>(aq)</sub>
-It is also possible for substances to react with water, producing ions.  For example, [[carbon dioxide]] gas dissolves in water to produce a solution that contains [[hydronium]], [[carbonate]], and [[hydrogen carbonate]] ions.
-Note that molten salts can be electrolytes, as well. For instance, when sodium chloride is molten, the liquid conducts electricity.
-An electrolyte in a solution may be described as concentrated if it has a high concentration of ions, or dilute if it has a low concentration. If a high proportion of the solute dissociates to form free ions, the electrolyte is strong; if most of the solute does not dissociate, the electrolyte is weak. The properties of electrolytes may be exploited using [[electrolysis]] to extract constituent elements and compounds contained within the solution.
-==Physiological importance==
-In [[physiology]], the primary ions of electrolytes are [[sodium]] (Na<sup>+</sup>), [[potassium]] (K<sup>+</sup>), [[calcium]] (Ca<sup>2+</sup>), [[magnesium]] (Mg<sup>2+</sup>), [[chloride]] (Cl<sup>−</sup>), [[hydrogen phosphate]] (HPO<sub>4</sub><sup>2−</sup>), and [[hydrogen carbonate]] (HCO<sub>3</sub><sup>−</sup>). The electric charge symbols of plus (+) and minus (−)  indicate that the substance is ionic in nature and has an imbalanced distribution of electrons, the result of [[Dissociation (chemistry)|chemical dissociation]]. Sodium is the main electrolyte found in extracellular fluid and is involved in fluid balance and blood pressure control.
-All known higher lifeforms require a subtle and complex electrolyte balance between the [[intracellular]] and [[extracellular]] environment. In particular, the maintenance of precise [[osmotic]] [[ion gradient|gradient]]s of electrolytes is important. Such gradients affect and regulate the [[Rehydration|hydration]] of the body as well as [[blood pH]], and are critical for [[nerve]] and [[muscle]] function. Various mechanisms exist in living species that keep the concentrations of different electrolytes under tight control.
-Both muscle tissue and neurons are considered electric tissues of the body. Muscles and neurons are activated by electrolyte activity between the [[extracellular fluid]] or [[interstitial fluid]], and [[intracellular fluid]]. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in the [[plasma membrane]] called [[ion channels]]. For example, [[muscle contraction]] is dependent upon the presence of calcium (Ca<sup>2+</sup>), sodium (Na<sup>+</sup>), and potassium (K<sup>+</sup>). Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.
-Electrolyte balance is maintained by oral, or in emergencies, intravenous (IV) intake of electrolyte-containing substances, and is regulated by [[hormone]]s, in general with the [[kidney]]s flushing out excess levels. In humans, electrolyte [[homeostasis]] is regulated by hormones such as [[antidiuretic hormone]], [[aldosterone]] and [[parathyroid hormone]]. Serious [[electrolyte disturbance]]s, such as [[dehydration]] and [[Water intoxication|overhydration]], may lead to cardiac and neurological complications and, unless they are rapidly resolved, will result in a [[medical emergency]].
-===Measurement===
-Measurement of electrolytes is a commonly performed diagnostic procedure, performed via [[blood test]]ing  with [[ion-selective electrode]]s or [[urinalysis]] by [[medical technologist]]s. The interpretation of these values is somewhat meaningless without analysis of the [[medical history|clinical history]] and is often impossible without parallel measurement of [[renal function]]. Electrolytes measured most often are sodium and potassium. Chloride levels are rarely measured except for [[arterial blood gas]] interpretation, since they are inherently linked to sodium levels. One important test conducted on urine is the [[specific gravity]] test to determine the occurrence of [[electrolyte imbalance]].
-===Rehydration===
-In [[oral rehydration therapy]], electrolyte drinks containing sodium and potassium salts replenish the body's [[water]] and electrolyte levels after [[dehydration]] caused by [[exercise]], [[Alcohol abuse|excessive alcohol consumption]], [[diaphoresis]], [[diarrhea]], [[vomiting]], [[Substance intoxication|intoxication]] or [[starvation]]. Athletes exercising in extreme conditions (for three or more hours continuously, e.g. [[marathon]] or [[triathlon]]) that do not consume electrolytes risk dehydration (or [[hyponatremia]]).<ref>{{cite journal |author=J,Estevez E,Baquero E,Mora-Rodriguez R |title=Anaerobic performance when rehydrating with water or commercially available sports drinks during prolonged exercise in the heat |journal=Applied Physiology, Nutrition and Metabolism |volume=33 |pages=290–298 |year=2008 |doi=10.1139/H07-188 |pmid=18347684 |issue=2}}</ref>
-An electrolyte drink can be home-made by using the correct proportions of water, sugar, salt, salt substitute for potassium, and baking soda.<ref>{{cite web|url=http://www.webmd.com/hw/health_guide_atoz/str2254.asp?navbar=hw86827 |title=Rehydration drinks |publisher=Webmd.com |date=2008-04-28 |accessdate=2010-08-20}}</ref>
-Electrolytes are commonly found in [[fruit juices]], [[coconut water]], [[sports drink]]s, [[milk]], and many fruits and vegetables (whole or in juice form) (e.g., [[potatoes]], [[avocados]]).
-==Electrochemistry==
-{{Main|electrolysis}}
-When [[electrode]]s are placed in an electrolyte and a [[voltage]] is applied, the electrolyte will conduct electricity. Lone [[electron]]s normally cannot pass through the electrolyte; instead, a chemical reaction occurs at the [[cathode]], consuming electrons from the anode.   Another reaction occurs at the [[anode]], producing electrons that are eventually transferred to the cathode. As a result, a negative charge cloud develops in the electrolyte around the cathode, and a positive charge develops around the anode. The ions in the electrolyte neutralize these charges, enabling the electrons to keep flowing and the reactions to continue.
-For example, in a solution of ordinary table salt ([[sodium chloride]], NaCl) in water, the cathode reaction will be
-:2H<sub>2</sub>O + 2e<sup>−</sup> → 2OH<sup>−</sup> + H<sub>2</sub>
-and [[hydrogen]] gas will bubble up; the anode reaction is
-:2NaCl → 2 Na<sup>+</sup> + Cl<sub>2</sub> + 2e<sup>−</sup>
-and [[chlorine]] gas will be liberated. The positively charged sodium ions Na<sup>+</sup> will react toward the cathode, neutralizing the negative charge of OH<sup>−</sup> there, and the negatively charged hydroxide ions OH<sup>−</sup> will react toward the anode, neutralizing the positive charge of Na<sup>+</sup> there. Without the ions from the electrolyte, the charges around the electrode would slow down continued electron flow; [[diffusion]] of H<sup>+</sup> and OH<sup>−</sup> through water to the other electrode takes longer than movement of the much more prevalent salt ions.
-Also: Electrolytes dissociate in water because water molecules are dipoles and the dipoles orient in an energetically favorable manner to solvate the ions.
-In other systems, the electrode reactions can involve the metals of the electrodes as well as the ions of the electrolyte.
-Electrolytic conductors are used in electronic devices where the chemical reaction at a metal/electrolyte interface yields useful effects.
-* In [[battery (electricity)|batteries]], two materials with different electron affinities are used as electrodes; electrons flow from one electrode to the other outside of the battery, while inside the battery the circuit is closed by the electrolyte's ions. Here, the electrode reactions convert chemical energy to electrical energy.<ref name="Kamil Perzyna, Regina Borkowska, Jaroslaw Syzdek, Aldona Zalewska, Wladyslaw Wieczorek 2011 58–65">{{cite journal|author=Kamil Perzyna, Regina Borkowska, Jaroslaw Syzdek, Aldona Zalewska, Wladyslaw Wieczorek|title=The effect of additive of Lewis acid type on lithium–gel electrolyte characteristics|journal=Electrochimica Acta| volume=57|pages=58–65|year=2011|doi=10.1016/j.electacta.2011.06.014}}</ref>
-* In some [[fuel cell]]s, a solid electrolyte or [[proton conductor]] connects the plates electrically while keeping the hydrogen and oxygen fuel gases separated.
-* In [[electroplating]] tanks, the electrolyte simultaneously deposits metal onto the object to be plated, and electrically connects that object in the circuit.
-* In operation-hours gauges, two thin columns of [[mercury (element)|mercury]] are separated by a small electrolyte-filled gap, and, as charge is passed through the device, the metal dissolves on one side and plates out on the other, causing the visible gap to slowly move along.
-* In [[electrolytic capacitor]]s the chemical effect is used to produce an extremely thin '[[dielectric]]' or [[Electrical insulation|insulating]] coating, while the electrolyte layer behaves as one capacitor plate.
-* In some [[hygrometer]]s the humidity of air is sensed by measuring the conductivity of a nearly dry electrolyte.
-* Hot, softened glass is an electrolytic conductor, and some glass manufacturers keep the glass molten by passing a large current through it.
-==Solid electrolytes==
-Solid electrolytes can be mostly divided into three groups:
-* Gel electrolytes - they closely resemble liquid electrolytes. In essence, they are liquids in a flexible lattice framework. Various additives are often applied to increase the conductivity of such systems.<ref name="Kamil Perzyna, Regina Borkowska, Jaroslaw Syzdek, Aldona Zalewska, Wladyslaw Wieczorek 2011 58–65"/><ref name="dry">{{cite web|url=http://www.evworld.com/article.cfm?storyid=933 |title=The Roll-to-Roll Battery Revolution |publisher=Ev World |date= |accessdate=2010-08-20}}</ref>
-* Dry polymer electrolytes - they differ from liquid and gel electrolytes in the sense that salt is dissolved directly into the solid medium. Usually it is a relatively high dielectric constant polymer (PEO, PMMA, PAN, polyphosphazenes, siloxanes, etc.) and a salt with low lattice energy. In order to increase the mechanical strength and conductivity of such electrolytes, very often composites are used, and inert ceramic phase is introduced. There are two major classes of such electrolytes: polymer-in-ceramic, and ceramic-in-polymer.<ref>Syzdek, Jaroslaw, et al., Journal of Power Sources, 173, 2007, p712-720 {{doi|10.1016/j.jpowsour.2007.05.061}}</ref><ref>Syzdek, Jaroslaw, et al., Electrochimica Acta, 55, 2010, p1314-1322, {{doi|10.1016/j.electacta.2009.04.025}}</ref><ref>Syzdek, Jaroslaw, et al., Journal of Power Sources, 194, 2009, p66-72, {{doi|10.1016/j.jpowsour.2009.01.070}}</ref>
-* Solid ceramic electrolytes - ions migrate through the ceramic phase by means of vacancies and/or interstitials within the lattice. There are also glassy-ceramic electrolytes.
-==See also==
-* [[Strong electrolyte]]
-* [[ITIES]] (Interface between Two Immiscible Electrolyte Solutions)
-==References==
-{{Reflist}}
-==External links==
-*[http://scitation.aip.org/content/aip/journal/jcp/32/4/10.1063/1.1730863 electrolyte mixtures]
-{{Galvanic cells}}
-[[Category:Electrolytes| ]]
-[[Category:Blood tests]]
-[[Category:Urine tests]]
-[[Category:Physical chemistry]]
-[[Category:Acid-base physiology]]