Bromocresol purple

Bromocresol purple

Names
IUPAC name 4,4'-(1,1-Dioxido-3H-2,1-benzoxathiole-3,3-diyl)- bis(2-bromo-6-methylphenol)
Other names 5',5''-Dibromo-o-cresolsulfonephthalein Bromcresol Purple
Identifiers
CAS Number	115-40-2
ChEBI	CHEBI:86154
ChemSpider	7974
Jmol interactive 3D	Image
PubChem	8273
InChI InChI=1S/C21H16Br2O5S/c1-11-7-13(9-16(22)19(11)24)21(14-8-12(2)20(25)17(23)10-14)15-5-3-4-6-18(15)29(26,27)28-21/h3-10,24-25H,1-2H3 Key: ABIUHPWEYMSGSR-UHFFFAOYSA-N InChI=1/C21H16Br2O5S/c1-11-7-13(9-16(22)19(11)24)21(14-8-12(2)20(25)17(23)10-14)15-5-3-4-6-18(15)29(26,27)28-21/h3-10,24-25H,1-2H3 Key: ABIUHPWEYMSGSR-UHFFFAOYAH InChI=1/C21H17BrO5S/c1-12-9-14(7-8-18(12)23)21(15-10-13(2)20(24)17(22)11-15)16-5-3-4-6-19(16)28(25,26)27-21/h3-11,23-24H,1-2H3
SMILES Brc1c(O)c(cc(c1)C3(OS(=O)(=O)c2ccccc23)c4cc(c(O)c(Br)c4)C)C
Properties
Chemical formula	C21H16Br2O5S
Molar mass	540.22 g·mol^−1
Appearance	Purple powder
Melting point	241 to 242 °C (466 to 468 °F; 514 to 515 K) (decomposition)
Solubility in water	< 0.1 %
Hazards
R-phrases	R36/37/38
S-phrases	S26, S36
NFPA 704	0 1 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Bromocresol purple (BCP) or 5',5"-dibromo-o-cresolsulfophthalein, is a pH indicator. In its sultone form, it has a pK_a value of 6.3,^[1] and is usually prepared as a 0.04% aqueous solution.

Bromocresol purple (pH indicator)
below pH 5.2		above pH 6.8
5.2	⇌	6.8

Uses

Besides its primary function as an indicator, bromocresol purple is used in medical laboratories to measure albumin, and as an addition to acid stop baths used in photographic processing as an indicator that the bath has reached neutral pH and needs to be replaced.

References

• Material Safety Data Sheet from Oxford University

1. "Bromocresol Purple: Subsection "Environmental Fate and Exposure Potential"". NCBI PubChem. Retrieved 1 March 2014.

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