Dithiofluorescein (sometimes generically called thiofluorescein) is a

complexometric indicator A complexometric indicator is an ionochromic dye that undergoes a definite color change in presence of specific metal ions. It forms a weak complex with the ions present in the solution, which has a significantly different color from the form exis ...

used in

analytical chemistry Analytical skill, Analytical chemistry studies and uses instruments and methods to Separation process, separate, identify, and Quantification (science), quantify matter. In practice, separation, identification or quantification may constitute t ...

. It changes from blue to colorless when it binds to mercury(2+) ions. It thus can indicate the endpoint in the

titration Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of Quantitative research, quantitative Analytical chemistry, chemical analysis to determine the concentration of an identified analyte (a substance to be ...

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

s using ''o''-hydroxymercuribenzoic acid or its

sodium salt Sodium salts are salt (chemistry), salts composed of a sodium cation and any anion. The anion may be the conjugate base of some Inorganic compound, inorganic or organic acids, or any monatomic or polyatomic anion. They can be formed by the Neutra ...

. The

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

can be immobilized t in a

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

on a

fiber optic An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...

, which might allow development of a detector for

sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...

ions in a flow cell. Unlike

fluorescein Fluorescein is an organic compound and dye based on the xanthene tricyclic structural motif, formally belonging to Triarylmethane dye, triarylmethine dyes family. It is available as a dark orange/red powder slightly soluble in water and alcohol. ...

and other related

fluoran Fluoran is a triarylmethane dye. It is the structural core of a variety of other dyes. These dyes have a variety of applications such as chemical stains (for example eosins) and in thermal paper Thermal paper (often supplied in roll form, an ...

dyes that have oxygen

substituent In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. The suffix ''-yl'' is used when naming organic compounds that contain a single bond r ...

s on the benzene rings, dithiofluorescein, which has sulfur substituents, is not

fluorescent Fluorescence is one of two kinds of photoluminescence, the emission of light by a substance that has absorbed light or other electromagnetic radiation. When exposed to ultraviolet radiation, many substances will glow (fluoresce) with color ...

References

{{reflist Analytical reagents Complexometric indicators Triarylmethane dyes Spiro compounds Lactones Thiols