Abstract: Inorganic metallic compounds, particularly salts, oxides and hydroxides, are removed from solutions by removing at least a part of the solution liquid and stirring and cooling this part while in the metastable state until a crystallization of the metallic compounds is rendered possible. Then energy is fed in bursts to the cooled down part in order to initiate the crystallization. The crystallized metallic compounds are separated, leaving a residual liquor which then is transferred back to the solution.

Abstract: A plating waste water treating apparatus including a tank defining an interior treating chamber. A sleevelike electrode which functions as an anode is positioned concentrically within and spaced slightly from the tank wall. An electrode which functions as a cathode is concentrically positioned within and spaced from the anode, with the cathode being defined by two concentric but radially spaced coil springs, with the outer spring functioning to receive thereon the metal deposits. A diffuser plate is provided at one end of the treating chamber to control waste water flow into the treating chamber.

Abstract: Carbonates, and particularly sodium carbonate, are removed from cyanide containing plating baths by taking from said cyanide containing bath at least part of its bath liquid; stirring and cooling in a cooling container the token liquid while in the metastabile state until crystallization of the carbonates occurs; separating the crystallized carbonates from the liquid; and leading the residual liquor back to the plating bath. Preferably, the quantity of bath liquid taken from the plating bath and the moment of this taking are chosen so as to bring the carbonate content of said plating bath, after leading the residual liquor back to it, to a carbonate content of 25 to 45 grams/liter, and the cooling is continued until the exothermic reaction, which is caused by the liberation of the heat of crystallization, starts, and thereafter the mixture is still held for 2 to 4 minutes at 0.5.degree. C. to 1.degree. C. below this starting temperature.