Salt water carries current with ions, not electrons, and so do your nerves
Dissolve table salt in water and it splits into charged sodium and chloride ions that drift toward opposite electrodes, carrying a current no copper wire could mimic. The same kind of traffic, pushed through protein gates in cell membranes, fires every nerve and contracts every muscle in the body.
An electrolyte is any substance that conducts by moving ions rather than electrons, typically a salt, acid or base dissolved in a polar solvent such as water. Water molecules are tiny dipoles that cluster around each ion, a process called solvation. Molten salts conduct too, and ionic liquids that melt below 100 °C are finding roles in batteries and fuel cells. The name joins the Greek prefix for amber, later tied to electricity, with a word for something that can be taken apart.
Michael Faraday coined the word ion but thought ions appeared only during electrolysis. Svante Arrhenius argued in his 1884 dissertation that dissolved salts already exist as charged particles even without any current, making reactions in solution reactions between ions. The idea earned him the 1903 Nobel Prize in Chemistry. Soon afterwards Franz Hofmeister and Siegmund Lewith found that different ions affect protein solubility in a consistent order, now called the Hofmeister series, whose cause is still debated.
Inside a battery, electrons travel through the outer circuit while ions close the loop internally. Electrolysing brine shows the partnership: hydrogen bubbles at one electrode and chlorine forms at the other, reacting to give sodium hypochlorite, household bleach. Without the salt ions sweeping in to neutralise charge build-up, the electron flow would stall.
In the body the main players are sodium, dominant outside cells, and potassium, dominant inside, along with calcium, magnesium, chloride, phosphate and bicarbonate. Their gradients govern hydration, blood pH and nerve and muscle signalling, and ion channels in cell membranes let them pass. Hormones such as aldosterone and antidiuretic hormone keep levels in check, with the kidneys clearing excess. Clinicians most often measure sodium and potassium, but the source stresses that readings mean little without clinical history and kidney function.
Source: Electrolyte
