Photography — Processing wastes — Analysis of cyanides — Part 1: Determination of hexacyanoferrate(II) and hexacyanoferrate(III) by spectrometry

The principle of the test method specified is treating a sample of effluent, or diluted effluent, with a mixture of iron(II) and iron(III) ions. If Fe(CN)₆ is present, a blue suspension will form. In the range of 1,0 mg/l to 10,0 mg/l, this suspension is stable and its absorbance is linear with its concentration. The absorbance is measured with a spectrometer, and the concentration determined from a previously established calibration.