Chlorophosphonazo-III

- Overview
  - Chlorophosphonazo-III is a colorimetric reagent for thorium, uranium, lanthanoids, actinoids, and alkaline earth metals. This reagent is readily soluble in water and is violet at pH 4 or lower, blue in NaOH solution, and brilliant green in acids such as H2SO4, HCl and diluted HNO3 (it decomposes in concentrated HNO3). Its proton dissociation constants are reported to be -1.1, -1.1, 0.6, 0.8, 1.5, 2.5, 5.47, 7.20, 12.15 and 15.13 (μ=0.1, 20°C). Chlorophosphonazo-III is used as a selective colorimetric reagent for calcium in a mixed Ca/Mg sample in the pH range of 2-3. It is also a useful indicator for the precipitation titration of SO42- using Ba2+ as a standard solution.
    
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- Properties
  - Alternative Name
    
    2,7-Bis(4-chloro-2-phosphonophenylazo)-1,8-dihydroxy-3,6-naphthalenedisulfonic acid
    
    CAS Number
    
    1914-99-4
    
    Molecular Formula
    
    C22H16Cl2N4O14P2S2
    
    Molecular Weight
    
    757.37
    
    Appearance
    
    Reddish brown or black purple crystalline powder
    
    Storage
    
    ambient temperature, protect from metal
    
    Shipping
    
    ambient temperature
    
    * For research use only
- Reference
  - 1) L. R. Snyder, et al., Characterization and Routine Determination of Nonbasic Nitrogen Types in Cracked Gas Oils by Linear Elution Adsorption Chromatography. Anal Chem. 1964;36:767-773.
    
    2) J. W. Ferguson, et al., Simultaneous Spectrophotometric Determination of Calcium and Magnesium with Chlorophosphonazo-III. Anal Chem. 1964;36:796-799.
    
    3) D. S. Howell, et al., Ultramicro Spectrophotometric Determination of Calcium in Biologic Fluids. Anal Chem. 1966;38:434-438.
    
    4) T. Yamamoto, Extraction-photometric Determination of Uranium(IV) with Chlorophosphonazo-III. Anal Chim Acta. 1973;65:329-334.
    
    5) M. Zenki, et al., Repetitive Determination of Calcium Ion and Regeneration of a Chromogenic Reagent Using Chlorophosphonazo III and an Ion Exchanger in a Circulatory Flow Injection System. Anal Sci. 2002;18:1137-1140.

MSDS

Chlorophosphonazo-III

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