15 Chromogen/Metal Indicator



Metal Indicator

  • Product code
    X003  XO
  • CAS No.
  • Chemical name
    3,3'-Bis[N,N-bis(carboxymethyl)aminomethyl]-o-cresolsulfonphthalein, disodium salt
  • MW
Unit size Price Item Code
1 g X003-10
5 g X003-12


XO is a colorimetric reagent and metal indicator of various metal ions. It is readily soluble in water. Its proton dissociation constants are reported to be -1.74, -1.09, 0.76, 1.15, 2.58, 3.23, 6.40, 10.5, and 12.6 (ion strength: 0.2). The color of the aqueous XO solution is yellow at pH < 6.3 and pink at pH > 6.5, and turns reddish-violet in the presence of metal ions. XO forms complexes with various metal ions in acidic conditions. Therefore, XO can be used to determine Ca, Cd, Mg, Pb, and Zn in the presence of Zephiramine in acidic conditions. XO is also a very versatile indicator for EDTA titration in acidic solutions.

Product Description

Technical info

Table 1 Colorimetric Determination of Metal Ions Using XO


Open References

1. D. C. Olson, et al., Semixylenol Orange: A Sensitive Reagent for Zirconium. Anal Chem. 1962;34:1299-1302.
2. M. Murakami, et al., Separation and Acid Equilibria of Xylenol Orange and Semi-xylenol Orange. Talanta. 1967;14:1293-1307.
3. Z. Nan, et al., Spectrophotometric Determination of Bismuth with Semi-xylenol Orange and Its Application in Metal Analysis. Talanta. 1989;36:733-737.

Handling and storage condition

Appearance: Reddish orange to reddish purple powder
Solubility in water: To pass test (clear, orange)
Solubility in Phosphate buffer: To pass test (clear, deep red)
Absorbance: ≧ 0.210 (around 440 nm)
Loss on drying (80°C): ≦ 10.0 %
Sulfated ash: ≦ 40.0 %
Sensitivity: To pass test
Freeo- Cresolphthalaine: To pass test
IR spectrum: Authentic
Handling and storage condition
Ambient temperature

Product Classification

Product Classification

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