Metanil yellow is applied as the main ingredient in solutions for Herovici staining. In addition to metanil yellow (C.I.: 13065; CAS no.: 587-98-4), the composition of the solution includes 1000 ml distilled aqua. / deionized water (CAS no.: 7732-18-5) and 10 ml acetic acid 99% (CAS no.: 64-19-7). The solution serves as a single solution within staining kits for Herovici staining and finds its use mainly in histology, in vitro diagnostics and scientific laboratories.

Chemically, metanil yellow is an azo dye with the molecular formula C18H18N4O7S2. Aqua dest. / deionized water is treated water and acetic acid is an organic acid with the chemical formula CH3COOH.

The dyeing effect is based on the attraction between the azo groups in metanil yellow and the amino groups of collagen. In this process, acetic acid promotes bonding by neutralizing any bases and optimizing the environment for the chemical reaction.

The application of the product in histology makes it possible to distinguish collagens of different degrees of maturity. Here, young collagen, also known as type III collagen, can be stained red, while mature collagen, type I collagen, appears in a blue-black coloration.