The ability to accurately measure and monitor pH is fundamental across a vast spectrum of scientific disciplines and industrial processes. pH indicators, like Cresol Red, provide a visual means to achieve this, translating subtle chemical changes into readily observable color shifts. As a premier manufacturer and supplier of specialty chemicals, including high-purity Cresol Red (CAS 1733-12-6), we are pleased to share insights into the science behind this essential laboratory reagent.

Cresol Red is a member of the sulfonphthalein family of pH indicators. Its chemical structure allows it to undergo reversible structural changes in response to variations in hydrogen ion concentration. This phenomenon is what causes the indicator to display different colors at different pH values. Specifically, Cresol Red typically shows a yellow color in more acidic conditions and transitions through orange to a distinct reddish-purple or violet hue as the solution becomes more alkaline. The primary pH range where this significant color change occurs is generally cited as being between pH 6.8 and 8.5. This range makes it particularly useful for monitoring neutral to slightly alkaline solutions.

The effectiveness of Cresol Red as an indicator is heavily reliant on its purity. Impurities can broaden the transition range, shift the pH at which color changes occur, or introduce unwanted coloration, leading to inaccurate pH readings. For applications ranging from laboratory titrations to sensitive cosmetic formulations and research into drug hydrophobicity, using Cresol Red with a high assay, such as our standard 99% purity, is critical. This ensures that the observed color changes are solely due to the pH of the solution being tested.

Understanding the pKa value associated with the indicator's transition is also key. While the exact pKa can vary slightly based on conditions, for Cresol Red, the relevant pKa for its main transition is around 8.0-8.5. This value indicates the pH at which the indicator is equally divided between its acidic (yellow) and alkaline (reddish-purple) forms, serving as the midpoint of its useful indicator range. This scientific understanding allows chemists and formulators to select the most appropriate indicator for their specific needs.

As a manufacturer based in China, we are committed to producing Cresol Red that meets these scientific expectations. We ensure rigorous quality control throughout our production process, from raw material sourcing to final product packaging (e.g., 25KG drums). This dedication to quality allows us to reliably supply Cresol Red to researchers, laboratories, and industries worldwide. If you are looking to buy Cresol Red and require a product known for its purity and precise indicator properties, we invite you to request a quote and learn more about our supply capabilities.