Fluorescein

9-(2-carboxyphenyl)-6-hydroxy-3 H -xanthen-3-one. _{C 20} H ₁₂ O ₅ (332.31). It is synthesized by heating and condensing 2 moles of resorcinol and 1 mole of phthalic anhydride in the presence of zinc chloride at 210 °C. Yellow-red powder. Melting point: 314-316 °C. Insoluble in water, slightly soluble in ethanol. It dissolves in an alkaline aqueous solution and turns yellow-red, emitting strong yellow-green fluorescence. The disodium salt is called uranin or uranin yellow (IC Acid Yellow 73). Absorption maximum at 510 nm, fluorescence maximum at 510 nm. Dyes, pigments, and intermediates thereof. In addition to being used in printing inks, its fluorescence is widely used as a probe for exploring underground waterways, tracking biochemical reactions, and medical (internal medicine, surgery, ophthalmology) examinations. The sodium salt has an LD ₅₀ of 6721 mg/kg (rat, oral). [CAS 2321-07-5][CAS 518-47-8: disodium salt]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

9-(2-carboxyphenyl)-6-hydroxy-3H-xanthen-3-one．C₂₀H₁₂O₅(332.31)．レソルシノール 2モル量と無水フタル酸1モル量とを塩化亜鉛の存在下，210 ℃ に加熱縮合して合成する．黄赤色の粉末．融点314～316 ℃．水に不溶，エタノールに微溶．アルカリ性水溶液に溶けて黄赤色を呈し，強い黄緑色の蛍光を発する．二ナトリウム塩はウラニン(uranin)またはウラニンイエロー(I.C.Acid Yellow 73)とよばれる．吸収極大510 nm，蛍光極大510 nm．染料，顔料，およびその中間体．印刷インキに用いられるほか，蛍光を利用し，地中水路の探索，生化学反応の追跡，医療(内科，外科，眼科)上の検査などにプローブとして広く利用される．ナトリウム塩はLD₅₀ 6721 mg/kg(ラット，経口)．[CAS 2321-07-5][CAS 518-47-8:二ナトリウム塩]

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