Ethers of Eosin

By treating the potassium salt of eosin with methyl iodide or chloride, or with ethyl bromide, monomethyl- and monoethyl-ethers of eosin may be obtained, and these even surpass the eosins in brilliancy of shade, their tone being in general somewhat bluer. 

They are monobasic acids, as one unaltered hydroxyl group is present. The salts are insoluble in water and absolute alcohol, but dissolve with tolerable ease in alcohol of 50 per cent. The solutions show a magnificent fluorescence. 

The ethyl ether, in form of its sodium or potassium salt, is extensively used in silk-dyeing as spirit eosin or primerose h kalcool/ For use, the commercial product is dissolved in spirit and gradually added to the dye-bath, which is acidified with acetic acid. 

Colourless ethers of eosin also exist, and may he prepared by heating the silver salt of eosin with alcoholic iodides [63], 

The commercial products known as erythrosin are iodine derivatives of fluorescein corresponding to eosins. The alkali-salts, which are the commercial products, are soluble in water, and possess a much bluer tone than the corresponding eosins, and their solutions do not exhibit the fluorescence characteristic of the latter bodies. 

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