SíNTESE, DETERMINA??O DE pKa E APLICA??O DE UM CORANTE TIAZOLILAZO COMO INDICADOR áCIDO-BASE SYNTHESIS, DETERMINATION OF pKa, AND APPLICATION OF A THIAZOLYLAZO DYE AS ACID-BASE INDICATOR

摘要

The pKa values of Br-TDB have been determined at 25 °C, in 0.10 mol L-1 NaCl byspectrophotometric method. The SQUAD computer software was used to process experimentaldata in pH ranging from 2.28 to 10.82 and 250 to 800 nm. The pKa values obtained were pKa1= 3.97 ± 0.01 and pKa2 = 7.64 ± 0.01. The Br-TDB reagent was applied as indicator in acidbase titrations and compared to phenolphthalein, methyl orange and thymolphthalein.Statistical t and F tests produced similar results without significant differences amongindicators, suggesting this dye can be used as acid-base indicator.