CAS 4538-16-3 appears in our catalog under these names: 5-Oxo-4,5-dihydro-1h-1,2,4-triazole-3-carboxylic acid, 95%, 5-Oxo-2,5-dihydro-1h-1,2,4-triazole-3-carboxylic acid, 95%, 5-Oxo-4,5-dihydro-1H-[1,2,4]triazole-3-carboxylic acid 95%, 5-Oxo-4,5-dihydro-1H-[1,2,4]triazole-3-carboxylic acid, 95%, 95%, 5-Oxo-4,5-dihydro-1H-[1,2,4]triazole-3-carboxylic acid, 95%. Offered by: Combi-blocks, Ambeed, Chemat, Fluorochem. Available pack sizes: 250mg, 5g, 1g, 100mg, 50mg.