While finding the concentration of $\ce{NaOH}$ via titration with $\pu{0.05M}$ Oxalic acid solution (in our lab) we put NaOH in the burette whereas added phenolphthalein to oxalic acid in titration flask. But in this video the demonstrator does just opposite ( i.e., $\ce{NaOH}$ in flak with phenolphthalein). I am confused in deciding which one might be correct. My view is that either would do the job but I need some clarification.

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    $\begingroup$ Both are perfectly correct methods as long as the volume measurements are accurate. $\endgroup$
    – AChem
    Nov 1, 2019 at 16:12
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    $\begingroup$ @M.Farooq - I disagree. It is easier to detect the change from colorless to colored. So, if possible, the titrant should be a base when phenolphthalein is the indicator. $\endgroup$
    – MaxW
    Nov 1, 2019 at 19:41
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    $\begingroup$ No matter what you do students will always come to you holding the flask asking if this is the right end-point :-) For a skilled analytical chemist, both techniques should be fine and of course colorless to color is easier to detect. One is less painful than the other. $\endgroup$
    – AChem
    Nov 1, 2019 at 20:42

1 Answer 1


The base should be in the burette, and the acid in the flask. With this technique, the point of equivalence is obtained with a rather high degree of accuracy.

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    $\begingroup$ This is not a universal practice in analytical chemistry. For example, if we wish to determine NaOH contaminated with some sodium carbonate, one has to use HCl in the buret, and two use two indicators, NaOH solution is in the flask. $\endgroup$
    – AChem
    Nov 1, 2019 at 20:43

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