Old phenolphthalein

[mazcheck]

Apparently some bottles of phenolphthalein solution did not work in a titration prac so I was wondering how do you test whether phenolphthalein is good or not?

[mtg]

I would do an indicator test with a little bit, I've never heard of the solid going off, but the solutions can get mixed up or over diluted. I test them in a bit of NaOH.

[rae]

You sure it was the phenolphthalein and not operator error. Maybe they added acid to acid.