Rhodamine B is a brilliant xanthene fluorescent dye (CAS 81-88-9, C.I. 45170, molecular weight 479.01) used as a stain, tracer and laser dye. Supplied as red-brown to dark green crystals or powder, it gives a clear solution in methanol where a 10 ppm preparation shows absorption maxima between 542 and 554 nm and intense red fluorescence. Applications span fluorescence microscopy, histology, water-flow tracing and analytical determinations. Practical grade, store below 30 C, shelf life three years. Packaged as a 100 g powder.