The captivating color transition of Solvent Yellow 2, also known by its historical moniker Butter Yellow (CAS 60-11-7), is rooted in its molecular structure and the principles of acid-base chemistry. As an azo dye, its chromophore system is sensitive to changes in proton concentration, leading to its utility as a pH indicator. NINGBO INNO PHARMCHEM CO.,LTD. offers this compound for applications where precise pH monitoring is essential.

The molecule of Solvent Yellow 2 features an azo group (-N=N-) connecting two aromatic rings, one of which is substituted with a dimethylamino group. In acidic conditions, the nitrogen atom of the amino group becomes protonated. This protonation alters the electron distribution within the molecule, specifically affecting the conjugation of the pi-electron system. This change in electron delocalization shifts the absorption spectrum, resulting in the observed color change from yellow (in neutral or alkaline conditions) to red (in acidic conditions). Understanding this structure-property relationship is key to appreciating why Methyl Yellow functions as an effective pH indicator.

When researchers decide to purchase Solvent Yellow 2, they are acquiring a molecule finely tuned for a specific pH range (2.9-4.0). This range is particularly useful for titrations involving weak acids and strong bases. The price of Solvent Yellow 2 can be influenced by the purity and the efficiency of its synthesis, which involves diazotization and coupling reactions. NINGBO INNO PHARMCHEM CO.,LTD. provides access to this compound, ensuring that its consistent quality supports accurate laboratory results.

While its past use as a food colorant is now restricted due to its carcinogenic nature, the scientific value of Solvent Yellow 2 as a pH indicator remains high. Its reliable performance in various analytical procedures, including the detection of free hydrochloric acid, solidifies its place in the laboratory toolkit. NINGBO INNO PHARMCHEM CO.,LTD. is committed to supplying this essential chemical, alongside vital safety information for its responsible use.