Hydroxy naphthol blue

CAS: 63451-35-4

Ref. 3D-FH161019

Product Information

• Name: Hydroxy naphthol blue
• Brand: Biosynth
• Description: Hydroxy naphtol blue is a synthetic azo dye, a chemical compound containing the functional group RN=N-R. The hydroxy naphtol blue trisodium and disodium salts are used as indicators to determine the content of alkaline earth and lanthanides spectrophotometrically, showing at maximum a wavelength of ~650 nm (λmax = 647.6 nm). An example of a common use of hydroxy naphtol blue sodium salt is to determine the hardness of water by measuring the concentration of calcium and magnesium. At alkaline or basic pH, the hydroxy naphtol blue forms a pink/red complex with the metal ions and, after titration with EDTA, hydroxy naphtol blue is liberated, turning the solution blue, indicating the endpoint.

Chemical properties

• Molecular weight: 620.48 g/mol
• Formula: C₂₀H₁₁N₂O₁₁S₃·3Na
• Color/Form: Black Blue Powder