Orange G solution is used in the laboratory as a histological stain. Especially erythrocytes and keratin structures are effectively stained by this solution. The staining is based on the electrostatic attraction between the acidic, negatively charged azo dye Orange G and the positively charged proteins in the target structures.

A particular suitability results from the specific attraction of the Orange G dye to proteins, especially keratin, which is found in skin and hair cells. The dye binds to these structures, allowing effective visualization under the microscope.

The Orange G solution consists of the azo dye Orange G dissolved in aqua bidest and acetic acid. The dye interacts with the structures to be stained through ionic bonds, which are maximized at the pH regulated by acetic acid. Acetic acid is used here to optimize the pH and promote hydrogen bonding, which stabilizes the dye binding.