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Cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper. This red-coloured solid is a component of some antifouling paints.
C 2731 (OTTO) Cuprous oxide, red, 96% Cas no 1317-39-1 - used as a pigment, a fungicide, and an antifouling agent for marine paints.