Bromocresol purple

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Bromocresol purple
Names
IUPAC name
3,3-Bis(3-bromo-4-hydroxy-5-methylphenyl)-2,1λ6-benzoxathiole-1,1(3H)-dione
Other names
5′,5′′-Dibromo-o-cresolsulfonephthalein
BCP
Bromcresol purple
Properties
C21H16Br2O5S
Molar mass 540.22 g/mol
Appearance Brown or purple solid
Odor Odorless
Melting point 241–242 °C (466–468 °F; 514–515 K) (decomposes)
Boiling point Decomposes
0.1 g/100 ml
Solubility Soluble in alcohols
Solubility in ethanol 8 g/100 ml
Solubility in methanol 0.4 g/100 ml
Solubility in methyl cellosolve 30 g/100 ml
Vapor pressure ~0 mmHg
Hazards
Safety data sheet Sigma-Aldrich
Except where otherwise noted, 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 an organic chemical compound, a dye of the triphenylmethane family (triarylmethane dyes) and a pH indicator. It is colored yellow below pH 5.2, and violet above pH 6.8.

Properties

Chemical

At pH below pH 5.2, solutions of bromocresol purple turn yellow, while above pH 6.8, they turn violet. Changing the level of acidity causes a shift in the equilibrium between two different structures that have different colors. In near-neutral or alkaline solution, the chemical has a sulfonate structure that gives the solution a purple color. As the pH decreases, it converts to a sultone (cyclic sulfonic ester) that colors the solution yellow.

Physical

Bromcreson purple is a purple-ish solid, slightly soluble in water.

Availability

Can be bought from chemical suppliers.

Preparation

Delete this section if not applicable

Projects

  • pH indicator
  • Biological stain for cells
  • Determination of serum albumin concentration

Handling

Safety

Bromocresol purple doesn't appear to be toxic, but it may be irritant.

Storage

In closed bottles, away from air and light.

Disposal

No special disposal is required.

References

Relevant Sciencemadness threads