Svante Arrhenius
Arrhenius' explanation was that in forming a solution, the salt splits up into charged particles (which Michael Faraday had given the name ions many years earlier). Faraday's belief had been that ions were produced in the process of electrolysis; Arrhenius' idea was that, even in the absence of an electric current, solutions of salts contained ions. He proposed that chemical reactions in solution were reactions between ions.