Phenol-red

Other Names Phenol, 4,4 -(3H-2,l-benzoxathiol-3-yUdene) M-, 5,5-dioxide Phenol, 4,4 -(3H-2, l-benzoxathiol-3-yUdene)di-, 5,5-dioxide 3H-2,l-Benzoxathiole, phenol deriv. a-Hydroxy-a,a-bis(p- hydroxyphenyl)-o-toluenesnlfonic add y-sultone 3,3-Bw(p-hydroxyphenyl)-2,l,3H-benzoxathiole 1,1-dioxide 3H-2,l-Benzoxathiole, 3,3- jX4-hydroxyphenyl)-, 1,1-dioxide Fenolipuna NSC 10459 PSP PSP (indicator) Phenol red Phenolsulfonephthalein Phenolsul-fonphthalein Phenolsulphonphthalein SuUbnphthal Sulphental Sulphonthal TF-R 2 CA Index Name Phenol, 4,4 -(l,l-dioxido-3H-2,l-benzoxathiol-3-ylidene)i -CAS Registry Number 143-74-8 Merck Index Number 7247 Chemical Structure 

Chemical/Dye Class Sulfonephthalein Molecular Formula C19H14O5S Molecular Weight 354.38 pH Range 6.8-8.4 

Solubility Sparingly soluble in water soluble in ethanol almost insolnble in ether, chloroform UV-Visible (A ) 557 nm, 558 nm, 360 nm, 423 ran, 433 ran Melting Point 300°C 

Boiling Point (Calcd.) 562.8 50.0°C Pressure 760 Torr Synthesis Synthetic methodsi-  

Safety/Toxicity Carcinogenicity, environmental analysis, dye-induced cholestasis, mutagenicity, Nephrotoxocity ° 

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Ltease test. The enzyme uretwe hydrolyses urea to ammonium carbonate (p. 519). The reaction is sp ific and is frequently used for solu tions of urea to which the biuret test cannot be applied. Add about 5 drops of phenohred to o 2 g. of urea dissolved in 5 ml. of water. To this yellow solution, add 0 2 g. of jack bean meal suspended in 2 ml. of water containing. also 5 drops of phenol-red. The colour changes to red as the solution becomes alkaline. 

The principle of this test is as follows The liquid suspected of containing urea is treated with dilute acid or alkali until its pH is about 7. A solution of the enzyme is also made and its pH adjusted to 7. The two solutions are mixed and the resulting conversion of urea to ammonium carbonate causes the pH of the solution to rise to over 8 this change is noted by the use of a suitable indicator, phenol-red being the one usually employed. Proteins do not interfere with the test, but the reaction is inhibited by traces of heavy metals. 

Place about 0 2 g. of jack-bean meal in a test-tube, add 2 ml. of water and about 5 drops of phenol-red. Mix thoroughly and allow the faintly yellow solution to stand while the urea solution is being made up. 

By condensing o sulphobenzoic anhydride with phenol in the presence of anhydrous zinc chloride, phenolsulphonephthalein (phenol red) is formed. Tetrabromination of the latter afibrds tetrabromophenolsulphonephthalein (bromophenol blue) ... 

Phenolsulphonephthalein (phenol red). Mix 10 g. of o-sulpho-benzoic anhydride (Section VIII,9), 14 g. of pure phenol and 10 g. of freshly fused zinc chloride in a small conical flask. Place a glass rod in the flask and heat gently over a flame to melt the phenol. Then heat the flask containing the well-stirred mixture in an oil bath at 135-140° for 4 hours. Stir from time to time, but more frequently during the first hour if the mixture froths unduly, remove the flask from the bath, cool and then resume the heating. When the reaction is complete, add 50 ml. of water, allow the water to boil and stir to disintegrate the product. Filter the crude dye with suction and wash it well with hot water. Dissolve the residue in the minimum volume of warm (60°) 20 per cent, sodium hydroxide solution, filter, and just acidify the filtrate with warm dilute hydrochloric acid (1 1). Filter the warm solution, wash with water, and dry upon filter paper. The yield of phenol red (a brilliant red powder) is 11 g. 

Phthaleins. Dyes of this class are usually considered to be triaryhnethane derivatives. Phenolphthalein [77-09-8] (23, R = CO) and phenol red [143-74-8] (23, R = SO2) are used extensively as indicators in colorimetric and titrimetric determinations (see Hydrogen-ION activity). These compounds are prepared by the condensation of phenol with phthaUc anhydride or i9-sulfoben2oic anhydride, respectively, in the presence of a dehydrating agent. 

The pH is measured colorimetricaHy with phenol red indicator. High FAC causes lower pH rea dings due to bleaching of the indicator and resultant HCl formation. The pH of pool water is readily controlled with inexpensive chemicals. Hydrochloric acid solution or sodium bisulfate lower it, whereas sodium carbonate raises it. Since acid addition neutralizes a portion of the alkalinity, this must be replenished if the alkalinity drops below the minimum. By contrast, pH adjustment with carbon dioxide does not affect alkalinity. 

Phenol red is an indicator with a pffa of 7.4. It is yellow in acid solution and red in alkaline. 

Chemicals. Indicator solutions ( 0.1 per cent, aq.). Bromophenol blue Congo red phenol red. 

Carefully scrape the separated bromophenol blue spots on to a sheet of clean smooth-surfaced paper using a narrow spatula (this is easier if two grooves are made down to the glass on either side of the spots). Pour the blue powder into a small centrifuge tube, add 2 mL of ethanol, 5 drops of 0.880 ammonia solution, and stir briskly until the dye is completely extracted. Centrifuge and remove the supernatant blue solution from the residual white powder. Repeat this procedure with the separated Congo red and phenol red spots . 

Sulphonphthaleins. These indicators are usually supplied in the acid form. They are rendered water-soluble by adding sufficient sodium hydroxide to neutralise the sulphonic acid group. One gram of the indicator is triturated in a clean glass mortar with the appropriate quantity of 0.1 M sodium hydroxide solution, and then diluted with water to 1 L. The following volumes of 0.1 M sodium hydroxide are required for 1 g of the indicators bromophenol blue, 15.0 mL bromocresol green, 14.4 mL bromocresol purple, 18.6 mL chlorophenol red, 23.6 mL bromothymol blue, 16.0 mL phenol red, 28.4 mL thymol blue, 21.5 mL cresol red, 26.2 mL metacresol purple, 26.2 mL. 

With 0.01M solutions, the ideal pH range is still further limited to 5.5-8.5 such indicators as methyl red, bromothymol blue, or phenol red will be suitable. The titration error for methyl orange will be 1-2 per cent. 

Pipette 25 mL of an aluminium ion solution (approximately 0.01 M) into a conical flask and from a burette add a slight excess of 0.01 M EDTA solution adjust the pH to between 7 and 8 by the addition of ammonia solution (test drops on phenol red paper or use a pH meter). Boil the solution for a few minutes to ensure complete complexation of the aluminium cool to room temperature and adjust the pH to 7-8. Add 50 mg of solochrome black/potassium nitrate mixture [see Section 10.50(C)] and titrate rapidly with standard 0.01 M zinc sulphate solution until the colour changes from blue to wine red. 

P2X3 Sensory neurones, NTS, some sympathetic neurons 2-MeSATP>ATP>a,p-meATP>Ap4A (rapid desensitization) TNP-ATP, PPADS, A317491, NF110, lp5l, phenol red Intrinsic cation channel... 

Gravimetric and volumetric methods are practicable for the quantitative determination of the a-sulfo fatty acid esters. Using gravimetric methods the surfactant is precipitated with p-toluidine or barium chloride [105]. The volumetric determination method is two-phase titration. In this technique different titrants and indicators are used. For the analysis of a-sulfo fatty acid esters the quaternary ammonium surfactant hyamine 1622 (p,f-octylphenoxyethyldimethyl-ammonium chloride) is used as the titrant [106]. The indicator depends on the pH value of the titration solution. Titration with a phenol red indicator is carried out at a pH of 9, methylene blue is used in acid medium [106], and a mixed indicator of a cationic (dimidium bromide) and an anionic (disulfine blue VN150) dye can be used in an acid and basic medium [105]. 

The amount of the ester sulfonates, besides the mono- and disalt of the a-sulfo fatty acid, can be calculated by two titrations, one in the acid and one in the basic range. In the basic range both sulfonates and carbocylate functionalities are negatively charged and titrated with the cationic surfactant hyamine. In acid medium the RCOOH group is protonated and no longer available for the titration. Since hyamine-methylene blue (acid conditions) titrates only sulfonate and hyamine-phenol red (basic conditions) determines both sulfonates and carbo-cylates, substraction of the titration value with phenol red from the double value of the titration with methylene blue yields only the a-sulfo fatty acid ester. This is the only species of the three which has merely the sulfonate function [106]. 

C18-0102. A solution has a pH of 8.5. What would be the color of the solution if the following indicators were present in the solution (a) methyl orange (b) phenol red (c) bromocresol green and (d) thymol blue (See Table 18-2. )... 

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