This is Cresol Red (Water Soluble) Indicator for PH (CAS Number 483-36-1), with a chemical formula of C21H14N2Na2O7S2, molecular weight of 498.43 g/mol. It is commonly used in the lab to measure the acidity of solutions and is useful in titration, buffer solutions, and other pH related experiments. The PubMed link for Cresol Red is https://pubchem.ncbi.nlm.nih.gov/compound/cresol_red.