Search: disinfectants

Disinfectants containing active chlorine, e.g. hypochlorites, oxidize iodide to iodine, which is titrated with sodium thiosulfate (Na₂S₂O₃) and converted to active chlorine.

Sodium thiosulphate reacts to form sodium tetrathionate (Na₂S₄O₆)

For the determination of low concentrations (up to 2.5 mg/l) of chlorine dioxide (CIO₂) and chlorite the photometric or colorimetric DPD methods are well established. Higher concentrations of ClO₂ that are present in the concentrates have to be determined by titration with sodium thiosulphate or after strong dilution.

Chlorine dioxide oxidizes iodide to iodine, which is then reduced by sodium thiosulphate. The sodium thiosulphate consumed is recalculated as ClO₂.

The quantitative determination is carried out in a sulphuric acid solution by titration with potassium permanganate:

5 H₂0₂ +  2  KMnO₄ + 3  H₂S0₄  →  2 MnSO₄ + H₂S0₄ + 8 H₂0 + 5 0₂

If the sample contains other peroxide-containing disinfectants in addition to hydrogen peroxide (H₂O₂), the method T-754-01-032 Peracetic-acid-based-disinfectants must be used.

Hydrogen peroxide oxidizes iodide to iodine, which is reduced by sodium thiosulfate (Na₂S₂O₃) and recalculated as hydrogen peroxide.

If the sample contains other peroxide-containing disinfectants in addition to hydrogen peroxide (H₂O₂), the method T-757-01-032 Peracetic-acid-based-disinfectants must be used.

In addition to peracetic acid (C₂H₄O₅), hydrogen peroxide (H₂O₂) is always present in disinfectants, so that both components must be determined together. The quantitative determination of hydrogen peroxide is carried out as described under T-753.01.032 Disinfectants-containing-hydrogen-peroxide-potassium-permanganate-method or T-753.02.032Disinfectants containing hydrogen peroxide - sodium thiosulphate method. The peracetic acid is determined iodometrically:

Aldehyde-containing agents are oxidized by iodine to the corresponding acid:

The iodine not used for oxidation is re-titrated with sodium thiosulphate.