Fluorescein CAS 2321-07-5, also known as fluorescent yellow, fluorescent green, or fluorescent red. There are two variants: stable red variant B and yellow variant A. The molecular formula is C20H12O5, with a molecular weight of 332.31. B is a crystalline powder with red and green fluorescence. Melting point 314-316 * C (decomposition). Soluble in hot alcohol, hot aniline, hot acetone, hot formic acid, slightly soluble in water, alcohol, ether, acetic acid, insoluble in petroleum ether. A is a yellow amorphous powder with a melting point of 314-316 ℃. Soluble in acetone, methanol, formic acid, slightly soluble in water, alcohol, ether, chloroform, benzene, acetic acid, xylene, nitrobenzene, insoluble in petroleum ether. Changes to a red variant when heated. Used as an indicator and biological staining agent for chemical analysis. It is obtained by reacting resorcinol with phthalic anhydride.

Chinese name: Fluorescein

Foreign name: Fluorescein

Nickname: Fluorescent Yellow; Fluorescent red; Fluorescent Orange; Acid Yellow 73

Chemical formula: C20H12O5

Molecular weight: 332.3063

CAS login number: 2321-07-5

EINECS login number: 219-031-8

Boiling point: 620.84 ℃

Water solubility: slightly soluble in water

Density: 1.602 g/cm ³

Appearance: Orange or light yellow red to red powder

Flash point: 232.65 ℃

Application: adsorption indicator liquid

Physical and chemical properties

Appearance: Orange or light yellow red to red crystalline powder.

Odor: No odor

Melting point/freezing point (℃): 125-127 ℃ (dec.)

Boiling point, initial boiling point, boiling range (℃): 620.8 ℃/760mmHg

Solubility: Soluble in acetone, pyridine, hot ethanol, methanol, formic acid, carbonate base, and hydroxide base solutions, with bright green fluorescence; Slightly soluble in water, alcohol, ether, benzene, chloroform, acetic acid, xylene, nitrobenzene, insoluble in petroleum ether.

Usage Description

1. Adsorption indicator for precipitation titration:

Prepare a 0.1% ethanol solution or a 1% aqueous solution with its sodium salt. Titrate Cl -, Br -, I -, SCN -, CN -, C2O42-, SO42-, CO32-, etc. with Ag+, and in neutral or weakly alkaline media, the titration endpoint color changes from yellow green to rose red.

2. Fluorescein is the matrix of luminescent substances. A substance that gives fluorescence to many living organisms. It forms a complex with ATP (fluorescein adenosine) and then binds to luciferase. Fluorescent luminescence activated during the oxidation process. The entire reaction is used for the detection of living organisms or for quantitative analysis of very low levels of bacterial contamination. For example, measuring with a fluorescence photometer.

3. Used as indicators for chemical analysis, biological colorants, and cosmetic colorants.

4. Antifreeze is an important pigment that can make the antifreeze present green fluorescence.

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