CAS 3421-67-8 appears in our catalog under these names: 2,3,5,6-Tetrachloroterephthalaldehyde 95%, 2,3,5,6-Tetrachlorobenzene-1,4-dicarbaldehyde, 97%, 97%, 2,3,5,6-Tetrachloroterephthalaldehyde, 98%. Offered by: Ambeed, Chemat, Fluorochem. Available pack sizes: 100mg, 250mg, 1g.