o-Cresolphthalein pH Indicator, 1 oz. For Sale

This 30ml (one ounce) vial of o-Cresolphthalein contains 0.04% w/v Ethanol. Acid-base indicator, 8.2 (colourless) – 9.8 (violet). It comes in a convenient squeeze bottle for dosing by the drop.

What is an acid-base indicator?
An acid-base indicator is either a weak acid or a weak base. Indicators have a highly helpful property: they change colour depending on the pH of the solution they are in. This colour shift occurs gradually throughout a variety of pH values rather than at a single pH. The colour change interval is the name given to this range. Each pH indicator has a usable pH range. For example, o-Cresolphthalein changes colour from colourless at 8.2 to violet at 9.8. And Bromothymol Blue has a good pH range of 6.0 (yellow) to 7.6 (blue).

How are liquid indicators used?
Liquid pH indicators are used to test other solutions. A few drops of the appropriate indicator applied to an unknown solution can reveal its pH value. pH indicators are used by chemists in a typical laboratory method known as titration. An unknown ingredient is measured here by carefully adding a solution of known concentration until a neutral point is attained. The neutral point is demonstrated by the colour shift of a pH indicator introduced into the unknown solution.