Used as a dye in histology for staining calcium in tissues, particularly in the von Kossa method, where it forms a red complex with calcium deposits for clear visualization under microscopy. Also applied in the textile industry for dyeing natural fibers such as cotton and cellulose, providing red to burgundy or purple shades depending on dyeing conditions; it can be combined with other precursors to achieve a wider range of hues and offers moderate resistance to light and water. Acts as a pH indicator in analytical chemistry due to its color change in varying pH environments and is used in laboratory studies of dye diffusion in materials.