期刊名称：Journal of Applied Sciences and Environmental Management
印刷版ISSN：1119-8362
出版年度：2006
卷号：10
期号：1
页码：5-8
语种：English
出版社：Department of Pure & Industrial Chemistry, University of Port Harcourt
摘要：The acid-base indicator properties of aqueous and ethanol extracts from calyces of H. sabdariffa (Zobo) and a dye obtained from the ripe fruits of Basella alba (Indian spinach), two local plants, were investigated. A purple coloured dye obtained from the ripe fruits of Basella alba showed a λmax at 580nm, absorptivity of 0.2269 and was found to be photochemically unstable. A deep red coloured dye obtained from aqueous and ethanol extracts of H. sabdariffa had λmax of 520nm and 540nm and absorptivities of 0.1909 and 0.1187 respectively. The peaks are associated with nЛ* transitions. In strong acid/strong base titrations using the dyes as indicators, the end-points obtained agreed well with those obtained using conventional indicators. The dyes were found not suitable for weak acid/weak base titrations. The K a of the purple dye from Basella alba was of the order of 10 -5 while that of the red dye from H. sabdariffa was of the order of 10 -6 . Journal of Applied Sciences and Environmental Management Vol. 10(1) 2006: 5-8
