Organic chemistry for students of medicine / [Sir James Walker].

  • Walker, James, Sir, 1863-1935.
Date:
1913
Catalogue details

Licence: In copyright

Credit: Organic chemistry for students of medicine / [Sir James Walker]. Source: Wellcome Collection.

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    is added to its solution it assumes a bright pink colour, whence its use as an indicator. The constitution generally attributed to its sodium salt is shown in the following equation :— O Off OH OH /\ /\ /\ \/ \/ \/ \ / \ • C o + NaOH = c 1 /N 1 \/ 1 \/ + H.,0 COONa Phenolphthalein Sodium salt of phenolphthalein In the passage from the phthalein to its salt an isomeric change in constitution is supposed to occur, the quinonoid structure, and consequently colour, appearing. Fluorescein is a phthalein formed from resorcinol, ;«-CeH5(OH)2, and phthalic anhydride. The formula of its sodium salt is as follows, when written with the quinonoid structure :— O OH COONa Sodium salt of fluorescein (Uranin) Uranin exhibits a brilliant greenish fluorescence in solution, but is of little importance as a dye. The eosins are in general fluoresceins in which several hydrogen atoms of the rings are replaced by bromine or iodine. Ordinary cosine-A is tetrabromo - fluorescein. The eosins are largely used as reddish dyes and stains. The phthaleins are all acid dyes.
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