Which chemical is used to artificially ripen Mayer's and Gill's hematoxylin?

The correct choice for artificially ripening Mayer's and Gill's hematoxylin is sodium iodate. This chemical plays a crucial role in the ripening process by oxidizing the hematoxylin dye, converting it into a more soluble and effective form for staining tissues.

In histopathology, hematoxylin is used for staining tissue sections, and the ripened form allows it to bind better to cellular structures, enhancing contrast and clarity during microscopy. Sodium iodate facilitates this transformation, ensuring that the resulting hematoxylin solution produces high-quality stain results.

In contrast, the other chemicals listed have different applications. Ferric chloride is often used in histology as a mordant to help fix the dye to the tissue but does not ripen hematoxylin. Mercuric chloride serves primarily as a preservative and fixative but is not involved in the ripening process of hematoxylin. Potassium chromate is sometimes used in other staining protocols but does not have a role in ripening hematoxylin either. Thus, sodium iodate stands out as the essential chemical specifically for this purpose.