[CrazyAssasin]

For school science project we have to prepare an analysis of oxalic acid in pineapples, rhubarbs, sorrel and some other vegetables or fruit, I can't remember. For the beginning we only had to titrate simple oxalic acid to be familiar with specific titration. I prepared prominent concentration solution of oxalic acid and poured few drops of concentrated sulfuric acid and before titration I heated the solution to approximately 60C degrees. Then I titrated the solution with prominent concentration of KMnO4. At stoichiometric point solution supposed to get a permanent light pink colour. Howerer when I reached the stoichiometric point solution became brown, after a while brown precipitate settled and solution was yellowish brown. I was disappointed. I think those precipitates could be MnO2. Am I right? If not, what should I do to get a pink solution at stoichiometric point?

[Borek]

Most likely not enough sulfuric acid. "Few drops" doesn't sound correct to me.

Compare http://www.titrations.info/permanganate-titration-standardization

[CrazyAssasin]

You are right, thanks.