15 Chromogen/Metal Indicator



Metal Indicator

  • Product code
    N013  NN
  • CAS No.
  • Chemical name
    2-Hydroxy-1-(2-hydroxy-4-sulfo-1-naphthylazo)-3-naphthoic acid
  • MW
Unit size Price Item Code
1 g N013-08

Product Description

NN is a colorimetric and chelatometric reagent for calcium (pH 12, λmax=470 nm) and UO22+ (λmax=570 nm, ε=1.36×105). Although NN is soluble in water, the solution is unstable and decomposes in a few minutes, especially in the presence of oxidative ions. Its proton dissociation constants are reported to be pKa2=9.26 and pKa3=13.67 (μ=0.1, 24ºC). An NN solution of 0.1% w/v in 50% aqueous methanol is stable for one week if stored in a cool and dark place. Ascorbic acid is used as a stabilizer of the NN stock solution. Al, Cu, Fe(III), and Ni interfere with the determination of calcium by NN and should be masked by KCN or triethanolamine.

Chemical Structure


Open References

1) K. Ueno, T. Imamura and K. L. Cheng, "Handbook of Organic Analitical Reagents 2nd Edition", CRC Press, 1992.
2) J. Patton and W. Reeder, "New Indicator for Titration of Calcium with (Ethylenedinitrilo) Tetraacetate", Anal. Chem., 1956, 28, 1026.
3) A. Itoh and K. Ueno, "Evaluation of 2-Hydroxy-1-(2-Hydroxy-4-Sulpho-1-Naphthylazo)-3-Naphthoic Acid and Hydroxynaphthol Blue as Metallochromic Indicators in the EDTA Titration of Calcium", Analyst, 1970, 95, 583.

Handling and storage condition

Appearance: Black purple powder
Solubility in NaOH solution: To pass test (clear, blue to deep blue)
Absorbance: 0.600 - 0.800 (around 555 nm)
Sulfated ash: ≦ 0.20 %
Sensitivity: To pass test
IR spectrum: Authentic
Handling and storage condition
Ambient temperature

Product Classification

Product Classification

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