Journal of Chemistry / 2019 / Article / Tab 3

Research Article

Natural Plant Extracts as Acid-Base Indicator and Determination of Their pKa Value

Table 3

Titration results of flower extracts and commercially available indicators.

IndicatorTitrand/titrantColour changeRequired volume of titrant

PhenolphthaleinNaOH/HClPink to colourless8.87 ± 0.0577
NH4OH/HClPink to colourless14.57 ± 0.0577
CH3COOH/NaOHColourless to pink12.07 ± 0.0577

sMethyl orangeNaOH/HClYellow to red9.17 ± 0.0577
NH4OH/HClYellow to red15.67 ± 0.1155
CH3COOH/NaOHRed to yellow5.27 ± 0.0577

Methyl redNaOH/HClYellow to red8.97 ± 0.0577
NH4OH/HClYellow to red16.13 ± 0.0577
CH3COOH/NaOHRed to yellow12.13 ± 0.0577

Bougainvillea glabraNaOH/HClBrownish yellow to red8.97 ± 0.0577
NH4OH/HClBrownish yellow to red15.17 ± 0.0577
CH3COOH/NaOHRed to brownish yellow12.23 ± 0.0577

Impatiens balsaminaNaOH/HClBrownish yellow to red9.07 ± 0.0577
NH4OH/HClBrownish yellow to red15.3 ± 0.1
CH3COOH/NaOHRed to brownish yellow12.13 ± 0.0577

Bauhinia purpureaNaOH/HClYellow to red8.93 ± 0.0577
NH4OH/HClYellow to red15.27 ± 0.0577
CH3COOH/NaOHRed to yellow12.3 ± 0.1