Bromothymol Blue, also known as Bromothymol Blue. BTB for short. Bromothymol blue is an acid - base indicator and adsorption indicator. It is often used as a respiratory reagent for aquatic organisms in biological experiments. CAS login registration number 76-59-5 EINECS number 200-971-2 melting point 204 ℃ boiling point 640.2 ℃ at 760 mmHg water-soluble slightly soluble dense degree of 1.542 g/cm3 flash point 341 ℃ should use ph indicator.

Light rose crystalline powder, melting point 200~202℃, soluble in ethanol, ether, methanol and dilute hydroxide alkali solution.

Slightly soluble in benzene, toluene and xylene, slightly soluble in water, almost insoluble in petroleum ether. It is blue in alkaline solutions and yellow in acidic solutions.

Bromothymol blue is an acid - base indicator, ranging from pH6.0(yellow) to 7.6(blue).

Normal water is neutral, with a pH of about 7. It's almost light green.

When you dissolve carbon dioxide, you form carbonic acid, which is a weak acid, so the pH doesn't go down too much and it turns yellow.

The intermediate transition color is green or the detection of CO2 production: make clear lime water become cloudy, and make bromothymol blue aqueous solution from blue to green and then yellow.