anions such as citrate and lactate this permeate is carried by a duct 1 to the entrance of a column 2 filled with a strong anionic resin af then from the exit of this column 2 by a duct 3 to the entrance of a column 4 filled with a strong cationic resin cf the strong cationic resin is in the na or k form i e its counter ion is the na or k ion the strong anionic resin is in the cl u2212 form i e its counter ion is the cl u2212 ion it will be noted that as an alternative both these resins could be used in a mixture in which case a single column would be sufficient during the passage of the permeate through the anionic resin it exchanges its multivalent inorganic anions phosphate and organic acid anions lactate citrate with the cl u2212 ions of the resin during its passage through the cationic resin it exchanges its multivalent cations ca 2 mg 2 with the na or k ions of the resin the permeate is therefore relieved from a substantial part of its multivalent inorganic cations and anions and of its organic acid anions which cations and anions have been.