Hematoxylin acc. to Weigert is used mostly in combination with various special (trichrome) stains. Because of its resistance to acid solutions, it retains the dye and stains nuclear membranes. Unlike the standard hematoxylins used in histology, such as hematoxylins acc. to Harris, Mayer, Mayer-Lillie, and Gill, Hematoxylin acc. to Weigert contains ferric ions that create resistance to acid solutions and sudden pH value changes. Hematoxylin acc. to Weigert is most commonly used in the following trichrome methods: AFOG, Gomori Trichrome, Masson-Goldner Trichrome, Masson Trichrome, Van Gieson Trichrome, Elastica-van Giesion and Weigert-van Gieson. Most of those methods are used for staining muscle and connective fibers. Due to the fact that Hematoxylin Weigert is not long-term stable, it is prepared by mixing two solutions directly before use. Hematoxylin, Weigert A is the first solution, and Ferri reagent is the second solution; functional Hematoxylin Weigert working solution is created by mixing the two.