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the coloured phenolphthalein solution has a tendency to gradually fading away with passage of time varying up to several months, its intensity may considerably decrease. On the other hand if the alkaline solution of phenolphthalein was only pink to light pink initially it may almost become colourless after a passage of several weeks to months. Moreover concentration of sodium carbonate should be kept to the minimum (say 0.05N) as higher concentration of alkali would hasten the degradation of phenolphthalein and consequent loss of colour.