Cresol purple

Other Names Phenol, 4,4 -(3H-2,l-benzoxathiol-3-ylidene) i5 [3-methyl-, 5,5-dioxide m-Cresol purple m-Cresol, 4,4 -(3H-2,l-benzoxathiol-3-ylidene)di-, 5,5-dioxide o-Toluenesulfonic acid, a-hydroxy-a,a-fcii(4-hydroxy-(9-tolyl)-, y-sultone 3H-2,l-Benzoxathiole, phenol derivative Cre-sol purple Metacresol Purple NSC 9607 m-Cresolsulfonephthalein CA Index Name Phenol, 4,4 -(l,l-dioxido-3H-2,l-benzoxathiol-3-ylidene) [3-methyl-CAS Registry Number 2303-01-7 Merck Index Number 2577 Chemical Structure 

Chemical/Dye Class Sulfonephthalein Molecular Formula C21H18O5S Molecular Weight 382.43 pH Range 1.2-2.8  

Physical Form Dark brown glittering crystals or oUve green powder Solubility Very shghtly soluble in water, ethanol soluble in methanol UV-Visible ( max) 579 mn, 371 nm Melting Point 250°C 

Boiling Point (Calcd.) 577.5 50.0°C Pressure 760 Torr Synthesis Synthetic methods -  

Cihelnik, S. Stibor, I. Lhotak, P. Solvent-free synthesis of sulfonephthaleins, sulfonefluoresceins and fluoresceins under microwave irradiation. Collect. Czech. Chem. Commun. 2002, 67, 1779-1789. 

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GL 28] [R 2] [P 30] Ammonia absorption in dilute acidic solution containing Cresol Purple indicator was rapid, as expected [7]. By appropriate choice of processing parameters, neutralization was achieved close to the gas/liquid contacting zone or distributed over the full contact length. This is evidence for having controls by both solution and gas-phase transport. 

An analytical solution for molecules with alkaline functionality is acid/base titration. In this technique, the polymer is dissolved, but not precipitated prior to analysis. In this way, the additive, even if polymer-bound, is still in solution and titratable. This principle has also been applied for the determination of 0.01 % stearic acid and sodium stearate in SBR solutions. The polymer was diluted with toluene/absolute ethanol mixed solvent and stearic acid was determined by titration with 0.1 M ethanolic NaOH solution to the m-cresol purple endpoint similarly, sodium stearate was titrated with 0.05 M ethanolic HC1 solution [83]. Also long-chain acid lubricants (e.g. stearic acid) in acrylic polyesters were quantitatively determined by titration of the extract. 

However, for m-cresol purple, thymol blue and o-nitroaniline, many estimated K, values yielded straight lines with eqn. 4.77, so that with these indicators the spectrophotometric method failed. This result led Bos to check some of the above results by means of the potentiometric method of Tanaka and Nakagawa64 applied to titrations in glacial acetic acid also he obtained the following data ... 

Figure 9. Normalized spectra of the base form of four indicators (1 - phenol red, 2 - bromo-cresol purple, 3 - thymol blue, and 4 -bromocresol green).

Using Appendix B, you would choose bromthymol blue (range 6.0 to 7.6, Lower color-yellow Upper color-blue) and m-Cresol purple (range 7.5 to 9.0, Lower color-yellow Upper color-violet) because bromthymol blue s high-end color (blue) ends where m-cresol purple s low-end color (yellow) begins. The pH would be between 7.5-8.5. 

Meta cresol purple m-Cresolsulphone-phthalein Red Yellow 1-2-2-8... 

A standard of pH 52 may be prepared by mixing 4.2 1 of 0.2 AT acetic acid with 158 cc. of o 2 AT sodium aceta while the 5.4 standard contains 29 cc. of the acid to 1 cc of sodium acetate solution Bromo-cresol purple may used as indicator The range 5.2 to 5.4 was determined wit out correcting for the protein or salt error. For details pH determinations the student is referred to Clark s book. 

Cresol purple m-Cresolsulfonephtha- lein Yellow Purple 7.4-9.0 8.3... 

Fortunately we are able to replace bromphenol blue and brom-cresol purple with other sulfonephthaleins which do not show dichromatism. W. C. Harden and N. L. Drake have prepared tetrabromophenoltetrabromosulfonephthalein (tetrabrom-phenol blue) which may be used in place of bromphenol blue. Both indicators have the same transformation range (pH 3.0-4.6) with a color change from pure yellow to pure blue. Chlor-phenol red, with a color change from yellow to red, is a good substitute for bromcresol purple. 

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