Direct Spectrophotometric Determination of Iron in the HCl Soluble Fraction of Carbonate Rocks

Abstract A method is presented for the direct determination of iron in the HCl soluble fraction of carbonate rocks. Use is made of the absorbance‐difference technique as developed by Glasner and Avinur, whereby the chloroferrate absorbance of the solution is measured at two wavelengths and the difference of absorbance between them is made the basis of the determination. Determination of iron by the chloroferrate absorbance when measured at only one wavelength was found to be impeded by the variation of the absorbance with the following factors: the ratio of chloride salt to free HCl; the nature of the chloride salt (Ca or Mg); slight changes in the total chloride concentration; and temperature. All these difficulties were largely overcome by the application of the absorbance‐difference technique.