Phosphoromolybdic Acid Orange G (A) Solution (GOLDNER II) is a combination of phosphoromolybdic acid and Orange G dye available in different concentrations. The solution comes in five variants containing different amounts of Orange G (2 g to 20 g) and phosphomolybdic acid (2 g to 50 g).

In histology, this solution is used as a component of the Goldner trichrome stain to differentiate various tissue components. In this process, phosphomolybdic acid stains collagen fibers and basement membranes blue, while Orange G stains erythrocytes and cell nuclei red. The different concentrations allow the intensity and staining contrasts to be adjusted according to the desired visualization and specific tissue type.