Bromocresol Green Paper

Quick Answer: Bromocresol Green Paper is indicator paper treated with bromocresol green, a dye that is yellow below about pH 3.8 and blue above about pH 5.4, with green shades in between; it is used to check solutions in the moderately acidic pH 4 to 5 region.

Working in the Moderately Acidic Region

Bromocresol green belongs to the sulfonephthalein family, like bromothymol blue, but its colour change sits about two and a half units lower on the scale. Where bromothymol blue answers ‘is this near neutral?’, bromocresol green answers ‘is this around pH 4 to 5?’, a region that includes many weak-acid solutions, acetate buffers and acidic rinse or fermentation liquids.

It is also an indicator for titrations whose end point falls in the acidic region, such as sodium carbonate or ammonia titrated with a strong acid. On paper it serves as a spot check that a solution has reached that zone. In a comparison practical, laying bromocresol green, Congo Red Paper and litmus side by side on the same series of dilute acids shows students how each indicator responds at a different point.

Like other single-indicator papers, it gives only three readings, yellow, green or blue. It is a band check, not a pH measurement.

Specifications

Applications

• Checking that acetate buffers and weak-acid solutions are in the pH 4 to 5 range.
• Spot-checking the approach to the end point when titrating carbonate or ammonia with strong acid.
• Indicator comparison practicals across the acidic part of the pH scale.
• Monitoring acidic rinse, fermentation or pickling liquids during training.

Care & Handling

• Keep the strips sealed and away from ammonia and acid vapours.
• Read the colour promptly, comparing it with an unused strip.
• Take a fresh strip for each sample and a clean rod for each transfer.

Why Choose LabEquip

College chemistry departments and analytical training labs buy bromocresol green paper as part of a set of indicator papers. LabEquip lists it with the rest of that range under General Lab Products, and orders can be placed through the contact page.

Frequently Asked Questions

What is the colour range of bromocresol green paper?

Yellow below about pH 3.8, green between about 3.8 and 5.4, and blue above about 5.4.

How does it differ from bromothymol blue paper?

Both belong to the same indicator family, but bromothymol blue changes around neutral, from about pH 6.0 to 7.6, while bromocresol green changes in the acidic region, from about pH 3.8 to 5.4.

Which titrations use bromocresol green?

Titrations whose end point lies in the acidic region, such as sodium carbonate or ammonia titrated with hydrochloric acid. It is also a component of some mixed indicators.

Can it show whether water is acidic?

Only if the water is quite acidic, below about pH 5.4. Most natural waters are above this and will show blue, so a near-neutral indicator or full-range paper is more informative.

Why is the colour sometimes blue-green rather than clearly green?

The strip is showing a mixture of the acid and base forms partway through the transition. A blue-green result points to the upper part of the range, around pH 5.

How long does the paper stay usable?

Kept sealed, dry and away from light and fumes, it stays usable for a long period. If unused strips have changed shade, or a known buffer gives the wrong colour, replace the stock.

Last Updated: September 2026