... 4, dielectric constant 18.10, insoluble in water, soluble in acid, ammonia, ammonium chloride, dissolved in sodium hydroxide to produce blue color ... glass, ceramic, enamel, paint industry, agent for take away, fungicides, solar heat absorber surface, reducing tobacco tar, artificial rainfall materials,etc ... Acid insoluble ≤%0.010.20.2Cl¯ ≤%0.010.20.2 High quality black copper oxide plating grade