Phenolphthalein, 125ml (4 oz.) for sale. Buy from The Science Company.

This 125 ml (four ounce) bottle of phenolphthalein is a 1% solution in Ethanol. Commonly used as an acid-base indicator indicator, 8.3 (colorless) - 9.8 (red). Comes packed in convenient squeeze bottle for dispensing by the drop. Our Phenolphthalein is a stock item and will ship the next business day.

What is an acid-base indicator?
An acid-base indicator is a weak acid or a weak base. Indicators have a very useful property - they change color depending on the pH of the solution they are in. This color change is not at a fixed pH, but rather, it occurs gradually over a range of pH values. This range is termed the color change interval. Each pH indicator is defined by a useful pH range. For example Phenolphthalein changes from colorless at 8.3 to pink at 9.8. And Bromthymol Blue has a useful range from 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 right indicator added to an unknown solution can tell you its pH value. Chemists use pH indicators in a common laboratory procedure called titration. Here, an unknown substance is measured by carefully adding a solution of known concentration until a neutral point is reached. The neutral point is indicated by the color change of a pH indicator mixed in with the unknown solution.