... , Mohs hardness 3-4, dielectric constant 18.10, insoluble in water, soluble in acid, ammonia, ammonium chloride, dissolved in sodium hydroxide ... circuit board plating, Ferrite magnetic materials and other electronic industries, glass, ceramic, enamel, paint industry, agent for take away, fungicides, solar ... ---Acid insoluble ≤%0.010.20.2Cl¯ ≤%0.010.20.2 High quality black copper oxide plating grade