Product Overview

Methyl Purple pH Indicator Solution Indicator Grade (CAS No. 1340-02-9) is a prepared indicator reagent based on Methyl Purple, a complex sulphonated azo-type dye system exhibiting a distinct acid–base colour transition in the mildly acidic region. The indicator changes from green toward purple as the medium becomes more acidic, with the characteristic transition occurring over approximately pH 4.8–5.4. This defined visual response makes the reagent useful for locating endpoints in aqueous acid–base procedures where an indicator transition in this pH region is appropriate.

The Indicator Grade is intended for laboratory procedures in which Methyl Purple is used as a visual pH indicator rather than as a general-purpose dye. A principal established application is alkalinity determination by acid titration, where the colour change provides the endpoint for total or “M” alkalinity measurements in aqueous samples. Methyl Purple indicator solution is also used in established titrimetric procedures where the selected endpoint lies within its transition interval, providing a practical visual alternative to potentiometric endpoint detection.

Typical Applications

• Total alkalinity determination in water by acid titration using a Methyl Purple endpoint.
• “M” alkalinity determination in aqueous water-quality testing.
• Endpoint indication in acid–base titrations requiring a transition in the approximately pH 4.8–5.4 region.
• Laboratory analysis of drinking water, treated water and other aqueous samples for alkalinity-related measurements.
• Preparation of analytical titration systems using Methyl Purple as the visual endpoint indicator.
• Educational and laboratory demonstrations of acid–base titration endpoints within the Methyl Purple transition range.

Common Synonyms

• Methyl Purple Indicator Solution
• Methyl Purple Solution
• Methyl Purple pH Indicator
• Methyl Purple Indicator
• Fleisher's Indicator Solution
• Fleisher's Indicator

Storage Conditions

Store the prepared indicator solution tightly closed and protected from excessive heat, direct light and contamination so that its characteristic colour response is maintained during storage and use. Minimise unnecessary exposure of the solution to air and promptly reclose the container after dispensing to preserve composition, homogeneity and endpoint performance.