IONS

the term originally used by Faraday to describe the components of a chemical compound set free when an electric current is pa ed through its solution. ‘The word is derived from the Gk., and means ‘traveller,’ and those parts of the decomposing compound which travel tojgthe anode are called anions, while those which go to the kathode are termed kations. It is a umed that when a salt is di olved in water, there occurs a certain amount of di ociation, (g.v.) ions, consisting of atoms or groups of atoms, being produced. These ions carry either a positive or a negative charge of electricity, and each molecule, on di ociation, forms two ions having equal and opposite charges. It should be carefully noted that ions are not held to be identical with chemical atoms. Thus, a solution of sodium chloride may contain positively charged sodium ions and negatively charges chlorine ions, but. seeing that metallic sodium reacts violently with water it is clear that there cannot exist, in the solution, any free sodium atoms. The ionic hypothesis is that the fons of sodium and chlorine are highly charged, electrically, and that the presence of these charges keep the ordinary chemical ‘activities in abeyance. Dr. R. A. Millikan, an American physicist, was awarded the Nobel prize in Nov. 1923 for isoiating the ion. See also I on i gaT I ON.