Bromocresol purple

Other Names Bromocresol purple Phenol, 4,4 -(3H-2,l-benzoxathiol-3-ylidene) [2-bromo-6-methyl-, S,S-dioxide o-Cresol, 4,4 -(3H-2,l-benzoxathiol-3-ylidene)fcw[6-bromo-, S,S-dioxide o-Toluenesulfonic acid, a,a- (5-bromo-4-hydroxy-m-tolyl)-a-hydroxy-, ysultone 3H-2,1-Benzoxathiole, phenol deriv. Bromcresol purple NSC 374134 CA Index Name Phenol, 4,4 -( 1,1 -dioxido-3H-2,1 -benzoxathiol-3-ylidene)i [2-bromo-6-methyl-CAS Registry Number 115-40-2 Merck Index Number 1387 Chemical Structure 

Chemical/Dye Class Sulfonephthalein Molecular Formula C2iHi6Br205S Molecular Weight 540.22 pH Range 5.2-6.8 

Physical Form Orange-yellow to brick red powder 

Solubility Sparingly soluble in water soluble in ethanol, ether, ethyl acetate 

Boiling Point (Calcd.) 590.2 50.0°C Pressure 760 Ton-Synthesis Synthetic methodsi 

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Similarly o-sulphobeiizoic anhydride and o-cresol yields o-cresolsulphone-phthalein (o-cresol red) dibromination of the last-named gives dibromo-o-sulphonephthaleln (bromocresol purple) ... 

Dibromo-o-cresolsulphonephthalein (bromocresol purple). Dissolve 6 g. of o-cresolsulphonephthalein in 50 ml. of glacial acetic acid, heat to boiling under reflux, add slowly a solution of 2 ml. of bromine in... 

Bromocresol Purple (5, 5"-dibromo-o-cresolsulfonephthalein) [115-40-2] M 540.2, m 241-242 (dec), pKi -2.15, pK2 6.3. Dissolved in aqueous 5% NaHC03 soln and ppted from hot soln by dropwise addition of aqueous HCl. Repeated until the extinction did not increase (Xn,ax 419nm). Can also be crystd from benzene. Indicator at pH 5.2 (yellow) and pH 6.8 (purple). 

Bromocresol purple (5.2...6.8) glutamic and ketoglutaric acids [217], halide and halate anions [91,218, 219] preservatives [220, 221] products of pyrolysis of epoxy resins [222] 5-aminodibenzocyclo-heptane derivatives [223] phenylalkanolamines, eph-edrine [224]... 

Dipping solution I Organic acids Dissolve 40 mg bromocresol purple in 100 ml 50% ethanol and adjust to pH = 10.0 (glass electrode) with caustic soda solution (c = 0.1 mol/1) [1]. 

Dipping solution II Halogen anions Dissolve 100 mg bromocresol purple in 100 ml ethanol and add a few drops of 10% ammonia solution until the color changes. 

The pH indicator bromocresol purple changes in color from yellow to purple in the pH range 5.2 —6.8. 

Bromocresol purple Dibromo-o-cresolsulphonphthalein 5.2-6.8 Yellow Purple 6.1... 

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. 

Thomas et al. [31] used a colorimetric method for the estimation of miconazole nitrate in creams. The method is based on the ion-pair extraction with bromocresol purple solution and measurement of the solution at 410 nm. 

A dual-transducer approach based on sol-gel optical sensors was recently reported to measure acid and salt concentrations in concentrated aqueous and HC1 solutions57. The acid sensors containing bromocresol purple, neutral red, and bromocresol green indicators were obtained by the immobilization of indicators in sol-gel derived films. The salt-HCl solution was flowed through the sensor cell58. 

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