Hello,
I was conducting an investigation to determine the amount of acetylsalicylic acid in Aspirin. After titrating the titrant (NaOH) against the analyte (solution of ethanol + 2x relatively dissolved aspirin tablets and 5x drops of phenolphthalein indicator), a colour change from a cloudy-opaque to a weak pink was observed. This colour change seemed permanent at the time, considering the flask containing the solution was swirled afterwards and the same pink intensity stayed. However, after approximately 8 minutes, the solution was observed to fade back to its original, cloudy state.
Why did this occur? Was it due to the endpoint not clearly being reached? Were the reactions between the chemicals still occurring? I'd greatly appreciate any reasons as to why this had occurred.
Thanks.