Bromocresol purple

Bromocresol purple
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
Identifiers
CAS number	115-40-2 Y
PubChem	8273
ChemSpider	7974 Y
Jmol-3D images	Image 1
SMILES Brc1c(O)c(cc(c1)C3(OS(=O)(=O)c2ccccc23)c4cc(c(O)c(Br)c4)C)C
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 Y Key: ABIUHPWEYMSGSR-UHFFFAOYSA-N Y 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
Properties
Molecular formula	C21H16Br2O5S
Molar mass	540.22 g mol−1
Appearance	Purple powder
Melting point	241 - 242 °C (decomposition)
Solubility in water	< 0.1 %
Hazards
R-phrases	R36/37/38
S-phrases	S26, S36
NFPA 704	0 1 0
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Bromocresol Purple (BCP) or 5',5"-dibromo-o-cresolsulfophthalein, is a pH indicator. It has a pK_a value of 6.3,^{[citation needed]} and is usually prepared as a 0.04% aqueous solution.

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

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