Following is the structure of 2,3,3-Trimethyl-3H-indole-5-sulfonic acid (CAS NO.132557-73-4):
                     
Empirical Formula: C₁₁H₁₃NO₃S
Molecular Weight: 239.2908 g/mol
Molar Refractivity: 61.77 cm³
Molar Volume: 177.7 cm³
Density: 1.34 g/cm³
Index of Refraction: 1.611
Melting point: 290-295 °C
Surface Tension of 2,3,3-Trimethyl-3H-indole-5-sulfonic acid (CAS NO.132557-73-4): 48.2 dyne/cm
Product Categories of 2,3,3-Trimethyl-3H-indole-5-sulfonic acid (CAS NO.132557-73-4): Indole; Dyes intermediates
SMILES: O=S(=O)(O)c2cc1c(\N=C(/C1(C)C)C)cc2
InChI: InChI=1/C11H13NO3S/c1-7-11(2,3)9-6-8(16(13,14)15)4-5-10(9)12-7/h4-6H,1-3H3,(H,13,14,15)
InChIKey: HUFDYAIAEFHOKI-UHFFFAOYAU

 2,3,3-Trimethyl-3H-indole-5-sulfonic acid , its cas register number is 132557-73-4. It also can be called 2,3,3-Trimethyl-3H-indole-5-sulfonic acid ; and 3H-indole-5-sulfonic acid, 2,3,3-trimethyl- .