Comparative Analysis of the Properties of Acid-Base Indicator of Rose (Rosa setigera), Allamanda (Allamanda cathartica), and Hibiscus (Hibiscus rosa-sinensis) Flowers

Abstract

The need to develop effective alternative for synthetic indicators is the demand of present-day chemistry. The acid-base indicator properties of Rose (Rosa setigera), Allamanda (Allamanda cathartica), and Hibiscus (Hibiscus rosa-sinensis) flowers were examined. Colour pigments were extracted from the flowers via cold and solvent extraction using soxhlet extractor. The pH value of the extracts with wavelengths of absorption was determined using ultraviolet spectrophotometer. From the results obtained, all the extracts exhibited sharp contrast between their colours in acid and base. Their pH was found to be 5.5 for cold extract of Rose and 5.6 for solvent extraction, 5.24 for cold extract of a Hibiscus and 6.52 for solvent extraction, 5.35 for cold extract of Allamanda, and 5.45 for solvent extraction. The maximum wavelengths of absorption obtained for all the extract fall within the visible region of electromagnetic spectrum. These values are almost similar to that obtained from synthetic indicators. It is on these bases that we concluded that natural indicators could be an excellent replacement for synthetic indicators since they are cheap, readily available, simple to extract, not toxic, user and environmentally friendly.

Experimenting on Natural Acid-Base Indicators: A Home-based Chemistry Activity during the COVID-19 Pandemic as evaluated by Teachers

“…Like the commercial indicators, the color changes determine the acidity or basicity of substances. Rose (Rosa setigera), gumamela (Hibiscus rosa-sinensis) and yellow bell (Allamanda cathartica) are some examples of natural indicators (Okoduwa et al, 2015). The color changes exhibited by rose, gumamela, and yellow bell extracts exemplify the possibility that plants found in the garden, backyard, or along the road could be utilized as sources of natural pH indicators.…”

A Comparative Analysis of Clitoria ternatea Linn. (Butterfly Pea) Flower Extract as Natural Liquid pH Indicator and Natural pH Paper

“…[2][3][4][5][6] The common solvent choice for the extraction is ethanol, methanol, water or its combination. Phenolphthalein is the most chosen standard indicator compared to methyl orange.…”

Analisis Aktivitas Antosianin dari Buah Senggani (Melastoma candidum L.), Kulit Kopi (Coffea arabica L.), dan Ubi Jalar Ungu (Ipomea batatas L.) Sebagai Indikator Asam Basa

“…Gambar 1. Struktur Antosianin (Sumber: Lestari et al, 2014) Beberapa penelitian terbaru telah berhasil mengekstraksi pewarna alami dari bunga segar seperti mawar (Rosa setigera), kembang sepatu (Hibiscus rosa-sinensis), Ixora coccinea dan dahlia serta mengujinya sebagai indikator pH (Okoduwa et al, 2015). Pada percobaan ini, digunakan buah senggani, kulit kopi dan ubi jalar ungu untuk diuji potensinya sebagai indikator alami pada titrasi asam-basa.…”