Bromtymolblå

Bromtymolblå, known in English as bromothymol blue (BTB), is a synthetic pH indicator dye used in chemistry and biology. It is a brominated derivative of thymol blue and is commonly employed to gauge acidity or basicity in aqueous solutions. In solution, bromtymolblå changes color from yellow in acidic conditions to blue in basic conditions, with a greenish tint near neutral pH.

The characteristic color transition of bromtymolblå covers roughly pH 6.0 to 7.6. This makes it especially useful for monitoring processes around neutral pH, such as the neutralization of weak acids, CO2 dissolution in water, and many educational titration experiments. It is widely used in standard indicator solutions for classroom demonstrations and in some practical water-quality tests and aquarium kits.

Bromtymolblå is typically available as a solid indicator or as an aqueous solution, often as its disodium salt or other salt forms suitable for water-based media. In laboratory practice, it is used in small concentrations and is compatible with aqueous environments. Proper storage involves keeping the container closed, protected from light and strong oxidizers, and at a stable, moderate temperature.

Safety considerations for bromtymolblå are those common to laboratory dyes. It is generally of low acute toxicity but should be handled with ordinary precautions to avoid unnecessary exposure and staining. Waste should be disposed of according to local regulations for chemical indicators.

See also: thymol blue, methyl orange, phenolphthalein.

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