Fluorescein, iodination

This solution may also be employed in the test for bromine. If iodine has been found, add small amounts of sodium nitrite solution, warm shghtly and shake with fresh 1 ml. portions of carbon tetrachloride until the last extract is colourless boil the acid solution until no more nitrous fumes are evolved and cool. If iodine is absent, use 1 ml. of the fusion solution which has been strongly acidified with glacial acetic acid. Add a small amount of lead dioxide, place a strip of fluorescein paper across the mouth of the tube, and warm the solution. If bromine is present, it will colour the test paper rose-pink (eosin). 

Another group of halogenated fluorescein dyes is prepared by condensing chloro derivatives of phthalic anhydride with resorcinol, followed by bromination or iodination. Thus Phloxine B /78472-87-2] (Acid Red 92, Cl45410) (42) is prepared by condensing tetrachlorophthaUc anhydride with resorcinol followed by tetrabromination. Phloxine B undergoes ethylation to yield the yellowish ted acid dye Cyanosine B [6441-80-1] (43). 

The treatment of unsaturated substances with halogen leads to addition to these molecules. This is true not only of bromine and chlorine vapor but also of the less reactive iodine. Substitution also occurs in the presence of light. Examples of such halogenations are listed in Table 12. Figure 32 illustrates the characterization of fluorescein in a bubble bath preparation. Bromination of the fluorescein in the start zone yields eosin. 

Irreversible reaction of [18] iodine with acetylsalicylic acid, aethaverine, amidopyrine, ascorbic acid, benzo-caine, quinine, dihydrocodeine, fluorescein, glycine, hydrocortisone acetate, isoni-azid, metamizole, papaverine, paracetamol, phenacetin, phenol-phthalein, piperazine, resorcinol, salicylic acid, salicylamide, sulfaguanidine, thymol, triethanolamine, tris buffer detection by reaction chromatography... 

Postchromatographic reactions can be classified as reversible or destructive depending on the type of interaction they undergo with the separated compounds, and as selective or universal, based on the specificity of the reaction. The most common reversible methods employ iodine vapor Kater, fluorescein. 

Caffeine Xanthine derivatives Purines Purines, pyrimidines Purines Chloraminc-T Iron (111) chloride followed by iodine Silver nitrate followed by sodium dichromate Fluorescein Silver nitrate followed by bromophenol blue... 

Reagent iodine vapour phosphomolybdic acid fluorescein/bromine sulphuric acid ninhydrin or isotin 2,4 -dinitropheny lhy drazine H2S water, diphenylcarbazide or... 

Fluorescein (147) is prepared by the same route as Pigment Red 90 (see p. 575). The compound is iodized with iodine and potassium iodate in an acidic medium. The iodic acid reoxidizes the resulting hydrogen iodide back to iodine ... 

Rose Bengal differs in reactivity from fluorescein and Eosin because of the iodines at C-2, C-4, C-5, and C-7 which differentiate the reactivity of the phenoxide from the carboxylate and make substitution at C-2 possible in lieu of substitution at C-6. Essentially three different kinds of Rose Bengal derivatives have been synthesized. The most common include derivatives with gegen ions other than sodium at both C-2 and C-6. Many esters of C-2 have been synthesized and compounds with a number of different gegen ions at C-6 have been reported. The rarest derivatives of Rose Bengal are the C-6 ethers, of which only three have been reported. 

Since the salts are again decomposed by the current, with splitting off of the halogen, which in turn reacts on the fluoresceins, the quantitative—very important for bromine and iodine —utilization of the halogen can take place. The well-known cosins are said to be obtained in excellent yields and in a high state of purity. 

Other Lower Iodinated Fluoresceins Not more than 9.0%. 

Other Fower Iodinated Fluoresceins Not more than 9.0%. Total Color Not less than 87.0%. 

FD C Red No. 3 is principally the monohydrate of 9-(o-carboxy-phenyl)-6-hydroxy-2,4,5,7-tetraiodo-3//-xanthen-3-one disodium salt, with smaller amounts of lower iodinated fluoresceins. 

Corresponding chlorofluoresceins are obtained by action of di-and tetra-chlorophthaUc anhydride on resorcin. These compounds are entirely different from those formed by direct chlorination of fluorescein. In these the chlorine (bromine, or iodine) always enters the resorcin-rest. The fluoresceins from the chlorinated phthalic acids serve as starting-points for a series of very brilliant phthalem dyestuffs, which were first introduced into the colour-industry by E. Noelting. 

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