Arsenic (III) oxide is a fine chemical product from the brand RESEARCH-LAB FINE CHEM INDUSTRIES. It is also known as Arsenous acid. Molecular Formula: As2O3 CAS Number: 1327-53-3 Molecular Weight: 197.84 Quantity: 500 gm/Bottle Purity: 99.9% The product is used to treat patients with leukemia that have been unresponsive to other agents. The anhydride form of arsenous acid, arsenic trioxide, is used as a herbicide, pesticide, and rodenticide.