Abstract:
In routine experiments synthetic indicators are the choice of acid base titrations. But there are
some limitations like environmental pollution, availability and higher cost which lead to
utilisation for natural compounds as acid base indicators. Natural indicators are easy to
prepare, easily available and have no toxic effects. The present work highlights the use of the
ethanolic extract of the Passiflora edulis peels as a natural acid-base indicator in acid-base
titrations. The Passiflora edulis fruits were identified, washed, cleaned by distilled water,
peeled and the 50gm of the purple peels were soaked in 100 mL of 97% ethanol for about 24
hours. The resulting solution was filtered using Whatman no.4 filters. The resulted ethanolic
extract was tested for its acid base indicator properties and found to turn pink and green in
acidic and basic media respectively. The extract was then used as an acid-base indicator for
strong acid versus strong base and strong acid versus weak base titrations. For comparison
purposes, Phenolphthalein and methyl orange indicators were used in the same titrations as
for the Passiflora edulis extract. The experimental data obtained from both titrations using the
three indicators were analysed using ANOVA and results showed that there was no
difference between the titre values of the Passiflora edulis indicator and the other two
indicators. Therefore, the indicator was found to be a potential substitute for methyl orange
and phenolphthalein for titrations of strong acid versus weak base and strong acid versus
strong base. Hence, Passiflora edulis peels extract as a natural indicator is found to be a very
useful, readily available, non-hazardous, economical, simple to prepare and accurate for the
acid-base titrations.
