• Phenolphthalein pH Indicator, 125mL (4 oz.)
  • Phenolphthalein pH Indicator, 125mL (4 oz.)
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Concentration: 1% in Ethanol.
Formula: (C6H4OH)2C2O2C6H4
(an approximation)
CAS: 77-09-8
U.S. DOT: UN1987, Class 3, PG II
Get the SDS: Download
Return Policy: See Below.
No Fly Shipping! Only via UPS Ground
- USA & Canada.
Discount: Buy at least 12, save 15%
Cat No. - NC-9102
Price: $12.95


This 125 mL (four ounce) bottle of phenolphthalein is a 1% solution in ethanol. Commonly used as an acid-base indicator, 8.2 (colorless) - 10 (red). Comes packed in HDPE squeeze bottle with PP flip top cap for dispensing by the drop. Our phenolphthalein is regularly stocked and will usually ship the next business day.

Our 4oz size Phenolphthalein has flammable contents and only ships within the contiguous US states and Canada using Standard Ground. No air deliveries allowed.

In a rush? No restrictions on our 1oz size. See tab... Also Available...

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 8.2 to pink at 10.

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. In schools, phenolphthalein pH indicator is used in a student activity demonstrating first hand how an “infectious agent” is transmitted through a population.

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For chemical quality assurance our chemicals are "factory fresh" from qualified industrial chemical suppliers. To ensure top quality we CANNOT ACCEPT RETURNS on chemical purchases, even if the container is unopened.


Hazardous chemicals are limited to the 48 contiguous U.S. states. Ground-only (No-Fly) chemicals are limited to the 48 contiguous U.S. states and Canada.

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