Note: Thus, hydrochloric acid ({HCl}) dissociates, in aqueous
solution, into the hydrogen ion, H^{+}, and the
chlorine ion, Cl^{-}; ferric nitrate, {Fe(NO3)3},
yields the ferric ion, Fe^{+++}, and nitrate ions,
NO3^{-}, NO3^{-}, NO3^{-}. When a solution containing
ions is made part of an electric circuit, the cations
move toward the cathode, the anions toward the anode.
This movement is called migration, and the velocity of
it differs for different kinds of ions. If the
electromotive force is sufficient, electrolysis ensues:
cations give up their charge at the cathode and
separate in metallic form or decompose water, forming
hydrogen and alkali; similarly, at the anode the
element of the anion separates, or the metal of the
anode is dissolved, or decomposition occurs.
2. One of the small electrified particles into which the
molecules of a gas are broken up under the action of the
electric current, of ultraviolet and certain other rays,
and of high temperatures. To the properties and behavior
of ions the phenomena of the electric discharge through
rarefied gases and many other important effects are
ascribed. At low pressures the negative ions appear to be
electrons; the positive ions, atoms minus an electron. At
ordinary pressures each ion seems to include also a number
of attached molecules. Ions may be formed in a gas in
various ways.