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An electrolyte is a substance that conducts electricity through the movement of , but not through the movement of . This includes most soluble salts, , and bases, dissolved in a polar solvent like water. Upon dissolving, the substance separates into and , which disperse uniformly throughout the solvent. Solid-state electrolytes also exist. In medicine and sometimes in chemistry, the term electrolyte refers to the substance that is dissolved.Lippincott Williams & Wilkins (2025). 9781582559230, Lippincott Williams & Wilkins. . ISBN 9781582559230
Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are drawn to the electrode that has an abundance of , 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 as hydrogen chloride (HCl), 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) or synthetic polymers (e.g., polystyrene sulfonate), termed "", which contain charged . A substance that dissociates into ions in solution or in the melt acquires the capacity to conduct electricity. Sodium, potassium, chloride, calcium, magnesium, and phosphate in a liquid phase are examples of electrolytes.
In medicine, electrolyte replacement is needed when a person has prolonged vomiting or diarrhea, and as a response to sweating due to strenuous athletic activity. Commercial electrolyte solutions are available, particularly for sick children (such as oral rehydration solution, Suero Oral, or Pedialyte) and athletes (). Electrolyte monitoring is important in the treatment of anorexia nervosa and bulimia.
In science, electrolytes are one of the main components of electrochemical cells.
In clinical medicine, mentions of electrolytes usually refer to the ions, and (especially) to their (in blood, serum, urine, or other fluids). Thus, mentions of electrolyte levels usually refer to the various ion concentrations, not to the fluid volumes.
Shortly after Arrhenius's hypothesis of ions, Franz Hofmeister and Siegmund Lewith 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 the Hofmeister 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 and might actually have explanations originating from the work of Charles-Augustin de Coulomb over 200 years ago.
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 Carbonic Acid ions.
can also be electrolytes as, for example, when sodium chloride is molten, the liquid conducts electricity. In particular, , which are molten salts with melting points below 100 °C, are a type of highly conductive non-aqueous electrolytes and thus have found more and more applications in fuel cells and batteries.
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.
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.Brown, Chemistry: The Central Science, 14th edition, pg. 680.
In 2021, researchers have found that electrolyte can "substantially facilitate electrochemical corrosion studies in less conductive media".
All known multicellular lifeforms require a subtle and complex electrolyte balance between the intracellular and extracellular environments. In particular, the maintenance of precise osmotic ion gradient of electrolytes is important. Such gradients affect and regulate the 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 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 (Ca2+), sodium (Na+), and potassium (K+). 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 , in general with the flushing out excess levels. In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic hormones, aldosterone and parathyroid hormones. Serious electrolyte disturbances, such as dehydration and overhydration, may lead to cardiac and neurological complications and, unless they are rapidly resolved, will result in a medical emergency.
Conductivity cells are another kind of tools used to measure the electrolyte solution's strength to conduct electricity.
A home-made electrolyte drink can be made by using water, sugar and salt mixing ratio. It is important to include glucose (sugar) to utilise the co-transport mechanism of sodium and glucose. Commercial preparations are also available for both human and veterinary use.
Electrolytes are commonly found in , sports drinks, milk, nuts, and many fruits and vegetables (whole or in juice form) (e.g., potatoes, ).
and hydrogen gas will bubble up; the anode reaction is
and chlorine gas will be liberated into solution where it reacts with the sodium and hydroxyl ions to produce sodium hypochlorite - household bleach. 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 to Solvation 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.
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