Uranine— Eosine

Tluoresceine, uranine, eosine, phloxme, erythrosme, rose bengale, methyl eosme, eosme scarlet, cyanosme, metachrome w violet... 

Quinoline yellow, quinaldme yellow, uranine, eosine orange, etc. Also turmeric, c ... 

The second family ofxanthene dyes is fluorescein and its derivatives. Fluorescein itself is only slightly fluorescent in alcohol solution. In contrast, the alkali salt obtained by addition of alkali exhibits the well-known yellow-green fluorescence characteristic of the fluorescein dianion (uranin). Fluorescein and its derivatives, e.g. eosin Yand erythrosin Y, are known to be very sensitive to pH and can thus be used as pH fluorescent probes (see Chapter 10). 

Arakawa et al.82) employed various 9-phenyl xanthene derivatives as the dye for DSC, and found that Eosin Y (EY Dye 18) shows relatively high conversion efficiency of 1.3% under 100 mW-cm"2 irradiance. They clarified the efficiency of 9-phenyl xanthene derivatives as follows EY > Dibromofluorescein > Fluorescein = Fluorescin > Rhodamin B > Dichlorofluorescein > Uranine >... 

A number of derivatives of fluorescein are useful dyes. Uranin is the disodium salt of fluorescein. ChrysoUn is a salt of benzyl-fluorescein, which is formed from phthalic anhydride and benzyl-resorcinol. It dyes silk and wool a fast yellow, and is used in cotton dyeing. Eosin is the disodium salt of tetrabromo-fluorescein, which is prepared by the action of bromine on fluorescein. Its dilute alkaline solution is rose-colored, and exhibits an intense yellow-green fluorescence. Other dyes related to fluorescein are tetrabromo-dichlorofluorescein and various ethers of fluorescein and its substitution-products. The dyes of this class produce on silk and wool shades from yellow to reddish yellow, cherry-red, and purple. 

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