CAS 121-57-3 appears in our catalog under these names: Sulfamethoxazole Impurity 4（Sulfamethoxazole EP Impurity D）, Sulfanilic acid, ACS, 98.0-102.0% , Sulfanilic acid, 98+% . Offered by: Hubei YoungXin, Thermo Scientific (Alfa Aesar). Available pack sizes: 10mg, 25mg, 50mg, 100mg, 200mg, 50g, 250g, 1000g.