NATURAL INDICATORS AS ALTERNATIVE TO SYNTHETIC ACID BASE INDICATORS

In acid-base titrations, indicators are used to show sharp color change at intervals of pH. Natural pigments in plants are highly colored substances and may show color change with variation of pH. An attempt has been made to investigate the indicator activity of flower pigments and to replace synthetic indicators as they have certain disadvantage like chemical pollution, availability problems and high cost. Alcoholic extract of Hibiscus rosasinensis, Calotropis gingantia, Brassica oleracea-capitata, Rosa chinensis, Brassica oleracea-italica, Ixora chinensis, Cantharanthus roseus gives sharp intense color change as compared to phenolphthalein and methyl orange. Herbal indicators are evaluated by using different titrations of acids versus bases. The flowers were cleaned by distilled water and cut into small pieces and macerated for two hours in 25 ml of 90% ethanol. The equimolar titrations were performed using 10ml of titrant with three drops of indicator. The mean and standard deviation for each type of acid base titrations were calculated from results the obtained. In all these titrations, promising results were obtained when it was tested against standard synthetic indicators. Titration show sharp color change at the equivalence point and the extract was found to be very useful and accurate for indicating the neutralization point. Natural indicators employed in the acid base titrations was found economic, safe and an efficient alternative for traditional indicators. Keywords: Herbal indicator, economic, accurate indicator, efficient alternative, sharp end point