Anelectrolyte is a substance that conductselectricity through the movement ofions, but not through the movement ofelectrons.[1][2][3] This includes most solublesalts,acids, andbases, dissolved in apolar solvent like water. Upon dissolving, the substance separates intocations andanions, which disperse uniformly throughout the solvent.[4]Solid-state electrolytes also exist. In medicine and sometimes in chemistry, the term electrolyte refers to the substance that is dissolved.[5][6]
Electrically, such a solution is neutral. If anelectric potential is applied to such a solution, the cations of the solution are drawn to theelectrode that has an abundance ofelectrons, while the anions are drawn to the electrode that has a deficit of electrons. The movement of anions and cations in opposite directions within the solution amounts to a current. Some gases, such ashydrogen chloride (HCl), under conditions of high temperature or low pressure can also function as electrolytes.[clarification needed] Electrolyte solutions can also result from the dissolution of some biological (e.g.,DNA,polypeptides) orsynthetic polymers (e.g.,polystyrene sulfonate), termed "polyelectrolytes", which contain chargedfunctional groups. A substance that dissociates into ions in solution or in the melt acquires the capacity to conduct electricity.Sodium,potassium,chloride,calcium,magnesium, andphosphate in a liquid phase are examples of electrolytes.
In clinicalmedicine, mentions of electrolytes usually refermetonymically to the ions, and (especially) to theirconcentrations (in blood, serum, urine, or other fluids). Thus, mentions of electrolyte levels usually refer to the various ion concentrations, not to the fluid volumes.
The wordelectrolyte derives fromAncient Greek ήλεκτρο- (ēlectro-), prefix originally meaningamber but in modern contexts related to electricity, and λυτός (lytos), meaning "able to be taken apart".[7]
In his 1884 dissertation,Svante Arrhenius put forth his explanation of solid crystalline salts disassociating into paired charged particles when dissolved, for which he won the 1903Nobel Prize in Chemistry.[8][9][10][11] Arrhenius's explanation was that in forming a solution, the salt dissociates into charged particles, to whichMichael Faraday (1791–1867) had given the name "ions" many years earlier. Faraday's belief had been that ions were produced in the process ofelectrolysis. Arrhenius proposed that, even in the absence of an electric current, solutions of salts contained ions. He thus proposed that chemical reactions in solution were reactions between ions.[9][10][11]
Shortly after Arrhenius's hypothesis of ions,Franz Hofmeister and Siegmund Lewith[12][13][14] found that different ion types displayed different effects on such things as the solubility of proteins. A consistent ordering of these different ions on the magnitude of their effect arises consistently in many other systems as well. This has since become known as theHofmeister series.
While the origins of these effects are not abundantly clear and have been debated throughout the past century, it has been suggested that the charge density of these ions is important[15] and might actually have explanations originating from the work ofCharles-Augustin de Coulomb over 200 years ago.
Electrolyte solutions are normally formed when salt is placed into asolvent such as water and the individual components dissociate due to thethermodynamic 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:[citation needed]
Molten salts can also be electrolytes as, for example, when sodium chloride is molten, the liquid conducts electricity. In particular,ionic liquids, which are molten salts with melting points below 100 °C,[17] are a type of highly conductive non-aqueous electrolytes and thus have found more and more applications in fuel cells and batteries.[18]
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.[citation needed]
Alkaline earth metals form hydroxides that are strong electrolytes with limited solubility in water, due to the strong attraction between their constituent ions. This limits their application to situations where high solubility is required.[19]
In 2021, researchers have found that electrolyte can "substantially facilitate electrochemical corrosion studies in less conductive media".[20]
All known multicellular lifeforms require a subtle and complexelectrolyte balance between theintracellular andextracellular environments.[21] In particular, the maintenance of preciseosmoticgradients of electrolytes is important. Such gradients affect and regulate thehydration of the body as well asblood pH, and are critical fornerve andmuscle function. Various mechanisms exist in living species that keep the concentrations of different electrolytes under tight control.[24]
Both muscle tissue andneurons are considered electric tissues of the body. Muscles and neurons are activated by electrolyte activity between theextracellular fluid orinterstitial fluid, andintracellular fluid. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in theplasma membrane called "ion channels". For example,muscle contraction is dependent upon the presence of calcium (Ca2+), sodium (Na+), and potassium (K+). Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.[citation needed][25]
Measurement of electrolytes is a commonly performed diagnostic procedure, performed viablood testing withion-selective electrodes orurinalysis bymedical technologists. The interpretation of these values is somewhat meaningless without analysis of theclinical history and is often impossible without parallel measurements ofrenal function. The electrolytes measured most often are sodium and potassium. Chloride levels are rarely measured except forarterial blood gas interpretations since they are inherently linked to sodium levels. One important test conducted on urine is thespecific gravity test to determine the occurrence of anelectrolyte imbalance.[citation needed]
Conductivity cells are another kind of tools used to measure the electrolyte solution's strength to conduct electricity.[26]
A home-made electrolyte drink can be made by using water, sugar and saltin precise proportions.[28] It is important to includeglucose (sugar) to utilise the co-transport mechanism of sodium and glucose[clarification needed]. Commercial preparations are also available[29] for both human and veterinary use.
Electrolytes are commonly found infruit juices, sports drinks, milk, nuts, and many fruits and vegetables (whole or in juice form) (e.g., potatoes,avocados).
Whenelectrodes are placed in an electrolyte and avoltage is applied, the electrolyte will conduct electricity. Loneelectrons normally cannot pass through the electrolyte; instead, a chemical reaction occurs at thecathode, providing electrons to the electrolyte. Another reaction occurs at theanode, consuming electrons from the electrolyte. 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.[citation needed]
For example, in a solution of ordinary table salt (sodium chloride, NaCl) in water, the cathode reaction will be
2 H2O + 2e− → 2 OH− + H2
andhydrogen gas will bubble up; the anode reaction is
2 NaCl → 2 Na+ + Cl2 + 2e−
andchlorine gas will be liberated into solution where it reacts with the sodium and hydroxyl ions to producesodium hypochlorite - householdbleach. The positively charged sodium ions Na+ will react toward the cathode, neutralizing the negative charge of OH− there, and the negatively charged hydroxide ions OH− will react toward the anode, neutralizing the positive charge of Na+ there. Without the ions from the electrolyte, the charges around the electrode would slow down continued electron flow;diffusion of H+ and OH− through water to the other electrode takes longer than movement of the much more prevalent salt ions.Electrolytes dissociate in water because water molecules are dipoles and the dipoles orient in an energetically favorable manner tosolvate the ions.[citation needed]
In other systems, the electrode reactions can involve the metals of the electrodes as well as the ions of the electrolyte.[30]
Electrolytic conductors are used in electronic devices where the chemical reaction at a metal-electrolyte interface yields useful effects.
Inbatteries, 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.[31]
In somefuel cells, a solid electrolyte orproton conductor connects the plates electrically while keeping the hydrogen and oxygen fuel gases separated.[32]
Inelectroplating tanks, the electrolyte simultaneously deposits metal onto the object to be plated, and electrically connects that object in the circuit.[citation needed]
In operation-hours gauges, two thin columns ofmercury 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.[citation needed]
In somehygrometers the humidity of air is sensed by measuring the conductivity of a nearly dry electrolyte.[citation needed]
Hot, softened glass is an electrolytic conductor, and some glass manufacturers keep the glass molten by passing a large current through it.[citation needed]
Gel electrolytes – closely resemble liquid electrolytes. In essence, they are liquids in a flexiblelattice framework. Variousadditives are often applied to increase theconductivity of such systems.[31][33]
Dry polymer electrolytes differ from liquid and gel electrolytes in that salt is dissolved directly into the solid medium. Usually it is a relatively high-dielectric constantpolymer (PEO,PMMA,PAN,polyphosphazenes,siloxanes, etc.) and a salt with lowlattice energy. In order to increase themechanical strength and conductivity of such electrolytes, very oftencomposites are made, and inert ceramic phase is introduced. There are two major classes of such electrolytes: polymer-in-ceramic, and ceramic-in-polymer.[34][35][36]
^M Andreev, JJ de Pablo, A Chremos, J F Douglas (2018). "Influence of ion solvation on the properties of electrolyte solutions".The Journal of Physical Chemistry B.122 (14):4029–4034.doi:10.1021/acs.jpcb.8b00518.PMID29611710.
^Shi J, Sun X, Chunhe Y, Gao Q, Li Y (2002).离子液体研究进展(PDF).化学通报 (in Simplified Chinese) (4): 243.ISSN0441-3776. Archived fromthe original(PDF) on 2 March 2017. Retrieved1 March 2017.
^Ye S(, Tang Z( (1986).细胞膜钠泵及其临床意义.上海医学 [Shanghai Medicine] (in Simplified Chinese) (1): 1. Archived fromthe original on 3 March 2017. Retrieved3 March 2017.
^Tu Z( (2004).电解质紊乱对晚期肿瘤的治疗影响.中华中西医杂志 [Chinese Magazine of Chinese and Western Medicine] (in Simplified Chinese) (10). 张定昌.在正常人体内, 钠离子占细胞外液阳离子总量的92%, 钾离子占细胞内液阳离子总量的98%左右.钠、钾离子的相对平衡, 维持着整个细胞的功能和结构的完整.钠、钾是人体内最主要的电解质成分...
^Open Resources for Nursing, Ernstmeyer K, Christman E (2021),"Chapter 15 Fluids and Electrolytes",Nursing Fundamentals [Internet], Chippewa Valley Technical College, retrieved28 February 2024
^J, Estevez E, Baquero E, Mora-Rodriguez R (2008). "Anaerobic performance when rehydrating with water or commercially available sports drinks during prolonged exercise in the heat".Applied Physiology, Nutrition, and Metabolism.33 (2):290–298.doi:10.1139/H07-188.PMID18347684.
^abKamil Perzyna, Regina Borkowska, Jaroslaw Syzdek, Aldona Zalewska, Wladyslaw Wieczorek (2011). "The effect of additive of Lewis acid type on lithium–gel electrolyte characteristics".Electrochimica Acta.57:58–65.doi:10.1016/j.electacta.2011.06.014.
^abcdJiangshui Luo, Annemette H. Jensen, Neil R. Brooks, Jeroen Sniekers, Martin Knipper, David Aili, Qingfeng Li, Bram Vanroy, Michael Wübbenhorst, Feng Yan, Luc Van Meervelt, Zhigang Shao, Jianhua Fang, Zheng-Hong Luo, Dirk E. De Vos, Koen Binnemans, Jan Fransaer (2015). "1,2,4-Triazolium perfluorobutanesulfonate as an archetypal pure protic organic ionic plastic crystal electrolyte for all-solid-state fuel cells".Energy & Environmental Science.8 (4):1276–1291.Bibcode:2015EnEnS...8.1276L.doi:10.1039/C4EE02280G.S2CID84176511.
^Syzdek J, Armand M, Marcinek M, Zalewska A, Żukowska G, Wieczorek W (2010). "Detailed studies on the fillers modification and their influence on composite, poly(oxyethylene)-based polymeric electrolytes".Electrochimica Acta.55 (4):1314–1322.doi:10.1016/j.electacta.2009.04.025.ISSN0013-4686.
Leaist DG, Lyons PA (1981). "Multicomponent diffusion of electrolytes with incomplete dissociation. Diffusion in a buffer solution".The Journal of Physical Chemistry.85 (12):1756–1762.doi:10.1021/j150612a033.
Kaminsky M (1957). "Ion-solvent interaction and the viscosity of strong-electrolyte solutions".Discussions of the Faraday Society.24: 171.doi:10.1039/DF9572400171.
