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CAS 23647-14-5 — 2-(4-Sulfophenylazo)1,8-dihydroxy-3,6-naphthalenedisulfonic acid trisodium salt (SPADNS)

2-(4-Sulfophenylazo)1,8-dihydroxy-3,6-naphthalenedisulfonic acid trisodium salt (SPADNS) is a synthetic azo dye widely used as a pH indicator and complexometric titrant in analytical chemistry, particularly for calcium and magnesium determinations. It appears as a dark red-orange powder, soluble in water, with a sharp color transition from red to blue in alkaline conditions. CAS 23647-14-5, molecular formula C16H9N2Na3O11S3, molecular weight 570.41 g/mol. Stored at ambient temperatures, non-hazardous under normal handling. Molekula supplies SPADNS from research to bulk quantities with full documentation and ISO 9001:2015 traceability.