NOVELTY - An apparatus (201) for forming metal hydroxide (204) comprises hydroxyl-producing cathode; acid-producing anode; direct current electricity source connected to cathode and anode, where source produces direct current electricity path between cathode and anode; metal silicate (202) mass contacted by acid produced by anode, and/or by hydroxyl produced by cathode; and water solution (203) having ion concentration to allow direct current electricity to pass in direct current electricity path between anode and cathode, where anode and cathode are partially submerged in water solution.    USE - As apparatus for forming metal hydroxide, where metal hydroxide is used for chemical, industrial, manufacturing, agricultural, aquacultural, environmental or other purposes, or is stored or discarded; for removing acid gas from a gas stream, mixture, or parcel; for penetrating, excavating or reducing in mass a metal silicate; and for producing hydrogen, oxygen, chlorine or other gases. The manufacturing purpose is the production of cement (claimed).    ADVANTAGE - The apparatus effectively dissolves metal silicates to produce metal hydroxide; remove carbon dioxide or other acid gases from the atmosphere or other gas mixture by reacting such gases with the metal hydroxide; penetrate or excavate metal silicates; extract metals or silicon-containing compounds from metal silicates; and produce hydrogen and oxygen or other gases. The apparatus makes more efficient dissolution of metal silicates and formation of metal ions, metal hydroxides, and silicon compounds by directly exposing metal silicates to the strongly acidic anolyte, and/or the strongly basic catholyte of certain electrochemical cells. The apparatus avoids high temperatures and/or pressures typically required to decompose metal silicates and to subsequently form metal salts of the acid gases. The metal ions, metal hydroxide, or metal salt produced can also be processed through various chemical, electrochemical, or thermal reduction processes, thus facilitating extraction of metals from the original silicate minerals.    DETAILED DESCRIPTION - An apparatus (201) for forming metal hydroxide (204), comprises a hydroxyl-producing cathode (i.e. an OH--producing cathode); an acid-producing anode (i.e. a H+ or H3O+-producing anode); a direct current electricity source connected to the hydroxyl-producing cathode and the acid-producing anode, where the direct current electricity source is capable of producing a direct current electricity path between the hydroxyl-producing cathode and the acid-producing anode; a metal silicate (202) mass that is contacted by acid produced by the acid-producing anode, and/or by the hydroxyl produced by the hydroxyl-producing cathode; and a water solution (203) having a sufficient ion concentration to allow the direct current electricity to pass in the direct current electricity path between the acid-producing anode and the hydroxyl-producing cathode, where the acid-producing anode and the hydroxyl-producing cathode are at least partially submerged in the water solution. The direct current electricity is applied across the acid-producing anode and the hydroxyl-producing cathode, where the direct current electricity is of sufficient current and voltage to generate hydroxyl ions at the hydroxyl-producing cathode and generate acid at acid-producing anode, where the acid or the hydroxyl is of sufficient concentration to dissolve at least some of the metal silicate into metal ions and silicate ions, where the silicate ions react with the acid produced by acid-producing anode and form at least one of the following: silica, silicic acid, other silicon compounds, and where the metal ions react with the acid formed at the acid-producing anode to produce a metal salt (208), allowing excess metal hydroxide produced from the water solution at the hydroxyl-producing cathode to accumulate in the water solution, or the metal ions react with the hydroxyl produced by the hydroxyl-producing cathode to form metal hydroxide. INDEPENDENT CLAIMS are included for the following:    (1) a method (M1) of forming metal hydroxide;    (2) a method (M2) of removing acid gas (207) from a gas stream, mixture or parcel;    (3) a method (M3) of penetrating, excavating or reducing in mass a metal silicate, involving providing a hydroxyl-producing cathode (i.e. an OH--producing cathode); providing an acid-producing producing anode (i.e. a H+ or H3O+-producing anode); providing a direct current electricity source that is connected to the hydroxyl-producing cathode and the acid-producing anode with the direct current electricity being capable of producing a direct current electricity path between the hydroxyl-producing cathode and the acid-producing anode and the direct current electricity being of sufficient current and voltage to produce acid at the acid-producing anode, and/or hydroxyl at the hydroxyl-producing cathode; providing a water solution into which the acid-producing anode and the hydroxyl-producing cathode are at least partially submerged, where the water solution has a sufficient ion concentration to allow the direct current electricity to pass in the direct current electricity path between the acid-producing anode and the hydroxyl-producing cathode; positioning the acid-producing anode and/or the hydroxyl-producing cathode in close proximity to a metal silicate mass, where the acid and/or the hydroxyl ions are of sufficient concentration to dissolve at least some of the metal silicate mass into metal ions and silicate ions, resulting in the penetration, excavation, or reduction in mass of the metal silicate; and    (4) a method (M4) of producing hydrogen (209), oxygen, chlorine or other gases.    DESCRIPTION OF DRAWING(S) - The figure shows diagrammatic view of system.    System for producing metal hydroxide (201)    Metal silicate (202)    Water solution (203)    Metal hydroxide (204, 206)    Gas-hydroxide contactor (205)    Acid gas (207)    Metal salt (208)    Hydrogen (209)    Oxidative gases (210)