The acidification of dilute solutions of alkali metal chlorides as a result of glow discharge action in closed cells is observed. This effect is appeared in the range of pH from 2 to 12. The boiling of the treated solution and its keeping at the room temperature (about a month) are not influence on acidification effect. The rectification of obtained solution gives the neutral condensate and acid remainder. The material of electrodes and plasma gas nature are not influenced by this effect. It was estimated that 10–20 positive ions are needed for formation of one proton in solution. The circulation of plasma treated solution results in increasing as well as decreasing solution pH. The rate and direction of pH change are the function of flux and concentration of electrolyte. It is supposed that non-equilibrium process of solution components transfer influences pH value.