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Bromothymol blue (also known as bromothymol sulfone phthalein and BTB) is a pH indicator. It is mostly used in applications that require measuring substances that would have a relatively neutral pH (near 7). A common use is for measuring the presence of carbonic acid in a liquid.
Universal indicator components Indicator Low pH colour Transition pH range High pH colour Thymol blue (first transition) Red 1.2 – 2.8 Yellow Methyl orange: Red 3.2 – 4.4 Yellow Methyl red: Red 4.8 – 6.0 Yellow Bromothymol blue: Yellow 6.0 – 7.6 Blue Thymol blue (second transition) Yellow 8.0 – 9.6 Blue Phenolphthalein: Colourless
In and of themselves, pH indicators are usually weak acids or weak bases. The general reaction scheme of acidic pH indicators in aqueous solutions can be formulated as: HInd (aq) + H 2 O (l) ⇌ H 3 O + (aq) + Ind − (aq) where, "HInd" is the acidic form and "Ind −" is the conjugate base of the indicator. Vice versa for basic pH indicators ...
Bromophenol is also used as a colour marker to monitor the process of agarose gel electrophoresis and polyacrylamide gel electrophoresis.Since bromophenol blue carries a slight negative charge at moderate pH, it will migrate in the same direction as DNA or protein in a gel; the rate at which it migrates varies according to gel density and buffer composition, but in a typical 1% agarose gel in ...
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Phthalein dyes are a class of dyes mainly used as pH indicators, due to their ability to change colors depending on pH. [1] They are formed by the reaction of phthalic anhydride with various phenols. They are a subclass of triarylmethane dyes. Common phthalein dyes include: Bromothymol blue; Bromocresol green; Bromocresol purple; Cresol Red; o ...
The standards used include potassium dichromate (isosbestic points at 339 and 445 nm), bromothymol blue (325 and 498 nm) and congo red (541 nm). The wavelength of the isosbestic point determined does not depend on the concentration of the substance used, and so it becomes a very reliable reference.
The increase in pH then causes color change in the bromothymol blue indicator, turning it blue. Under neutral conditions the medium remains a green color. The color change to blue is useful because growth on Simmons' citrate agar is often limited and would be hard to observe if it were not for the color change.