Photographie — Produits chimiques de qualité photographique — Méthodes d'essai — Partie 5: Détermination des teneurs en métaux lourds et en fer

The method is based on preparation of test samples and heavy metals standard solutions, preconditioning them, addition of sodium sulfide solution (for determination of heavy metals) or 1,10-phenanthroline reagent (for determination of iron), dilution with water, mixing well, transfer to two Nessler colour-comparison cylinders, and comparing the colour of both solutions.