Química Nova (Jan 2009)

Aplicação de um corante tiazolilazo como indicador ácido-base e determinação das suas constantes de ionização ácida Application of a thiazolylazo dye as an acid-base indicator and determination of its acid ionization constants

  • Regina Terumi Yamaki,
  • Daniel Rodrigues Vieira,
  • Cleber Galvão Novaes,
  • Hygor Rodrigues de Oliveira,
  • Valfredo Azevedo Lemos,
  • Sandra Carvalho

DOI
https://doi.org/10.1590/S0100-40422009000700042
Journal volume & issue
Vol. 32, no. 7
pp. 1943 – 1946

Abstract

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The pKa values of the 6-[2´-(6´-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD) have been determined at 25 °C, in 0.10 mol L-1 NaCl medium by spectrophotometric method. The SQUAD computer program was used to process experimental data in pH range 1.78 - 11.54 and 290 - 720 nm. The pKa values obtained were 4.60 ± 0.04 and 9.48 ± 0.02. The Me-BDBD reagent was applied as indicator in titration of acid-base. The results were compared with phenolphthalein and bromocresol green indicators. Statistical t and F tests indicated that there were no statistically significant differences between the results for indicators with good agreement.

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