Ensaio rápido para avaliar o potencial do extrato da flor de Caesalpinia pulcherrima na padronização de solução de HCl

Abstract

Artificial indicators are toxic to the ambient. An alternative to minimize waste generation is the use of natural indicators, meeting the Green Chemistry. The aim of this work was to evaluate the potential of Caesalpinia pulcherrima flower extract in the standardization of hydrochloric acid (HCl) solution, in comparison with the artificial Methyl Red indicator, using a titrimetric technique. This acidic solution standardization procedure using natural indicator is pioneer and should be studied. Flower petals were macerated with PA 1:1 (w/v) ethyl alcohol, and the extract was filtered through a fiberglass filter and stored in a test tube wrapped in aluminum foil. Titration procedures were performed in triplicate, with artificial and natural indicator. The natural indicator was able to detect the end point of the titration of the HCl with Borax, showing the same pH (around 5.0) indicated by the artificial indicator. The colors observed at the beginning and end of the titration were, respectively, yellow and salmon pink with the use of methyl red and, yellow and light lilac with the extract of C. pulcherrima. Concentration results for HCl in the standard solution were similar to the natural indicator. Thus, using the C. pulcherrima flower extract evaluated in the standardization of strong acid solution (HCl) with the weak base (borax) is advantageous.