Acid-Base Indicator Properties of Dye from Local Plant The Rosella Calyces (Hibiscus Sabdariffa)

摘要

The dye from the Calyces Hibiscus Sabdariffa (Zobo) was extracted and used as acid-base indicator for the standardization of acid and determination of the molar massesof some selected acids. The Calyces Hibiscus sabdariffa was peeled, washed and heated in an oven at 60°C. It was ground into powder and soaked in hot and cold ethanolfor the extraction. Part of the extract was filtered and concentrated by subjecting the extract to slow heating which yielded 1.5 kg of the Hibiscus sabdariffa indicator. Hotand cold extracts of the Hibiscus sabdariffa were used for the standardization of acid with 0.03 M concentration of the bases. On the preliminary test carried out on basicmedium, the calyces Hibiscus sabdariffa indicator turned red in acidic condition and green in basic medium, both hot and cold indicators yielded sharp and intense coloursat the end points during titration processes. However, there were no colour changes for weak acid versus weak bases (H2C2O4/Na2CO3 and H2C2O4/B4Na2O7). The meanvolumes of the acids used were determined and used for the determination of the molar concentration and mass concentration of all the acids used in the research work.