Fluorescent Dyes
Often fluorescent dyes are used for this purpose, especially in the following circumstances
- Insufficient lighting (e.g., sewers or cave waters)
- Precise quantitative data are required, measured by a fluorometer
- Very small amounts of the dye is allowed to be added (1 part per trillion may be detected).
Fluorescein is among the first fluorescent dyes, developed in 1871. Its disodium salt under the trademark "Uranine" was developed several years later and still remains among the best tracer dyes.
Other popular tracer dyes are rhodamine, pyranine and sulforhodamine.
Read more about this topic: Dye Tracing