Best Manufacturer For Rhodamine B Dye in Mumbai. Rhodamine B (540%) is used as a dye, especially for paper. It is also used as a reagent for antimony, bismuth, cobalt, niobium, gold, manganese, mercury, molybdenum, tantalum, thallium, tungsten; as biological stain. It is often used as a tracer dye within water to determine the rate and direction of flow and transport. Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with instruments called fluorometers It’s provisionally listed for use in drugs and cosmetics.