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Journal of Chemistry
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2019
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Article
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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.
Indicator
Titrand/titrant
Colour change
Required volume of titrant
Phenolphthalein
NaOH/HCl
Pink to colourless
8.87 ± 0.0577
NH
4
OH/HCl
Pink to colourless
14.57 ± 0.0577
CH
3
COOH/NaOH
Colourless to pink
12.07 ± 0.0577
sMethyl orange
NaOH/HCl
Yellow to red
9.17 ± 0.0577
NH
4
OH/HCl
Yellow to red
15.67 ± 0.1155
CH
3
COOH/NaOH
Red to yellow
5.27 ± 0.0577
Methyl red
NaOH/HCl
Yellow to red
8.97 ± 0.0577
NH
4
OH/HCl
Yellow to red
16.13 ± 0.0577
CH
3
COOH/NaOH
Red to yellow
12.13 ± 0.0577
Bougainvillea glabra
NaOH/HCl
Brownish yellow to red
8.97 ± 0.0577
NH
4
OH/HCl
Brownish yellow to red
15.17 ± 0.0577
CH
3
COOH/NaOH
Red to brownish yellow
12.23 ± 0.0577
Impatiens balsamina
NaOH/HCl
Brownish yellow to red
9.07 ± 0.0577
NH
4
OH/HCl
Brownish yellow to red
15.3 ± 0.1
CH
3
COOH/NaOH
Red to brownish yellow
12.13 ± 0.0577
Bauhinia purpurea
NaOH/HCl
Yellow to red
8.93 ± 0.0577
NH
4
OH/HCl
Yellow to red
15.27 ± 0.0577
CH
3
COOH/NaOH
Red to yellow
12.3 ± 0.1