MAYUR C. SHAH, HEMANT P. PATEL AND PRATEEK G. SHILPKAR
Abstract
Now a days many synthetic neutralization indicators are available and their number are continuously increasing. Industrial synthesis of indicators causes environmental pollution directly as well as indirectly. The present study deals with small effort to give alternate of synthetic neutralization indicators through principles of green chemistry. Lavender to pink coloured Argyreia nervosa flowers are available during July-December and March-April. The water extract 10%w/v shows different colours at different pH : Pink (0 < pH < 2.87); Light pink (2.87 ≤ pH < 3.09); Coolourless (3.09 ≤ pH < 6.90); Green (6.9 ≤ pH) in pH metric titration of 0.1M HCl→0.1M NaOH. Indicator properties of this extract may be due to change in structure of anthocyanine derivatives, present in flower with pH change. Water extract of Argyreia nervosa flowers is more suitable as an acid-base indicator in HCl→NaOH. It is not suitable for CH3COOH→NaOH and NH4OH→HCl titrations.