I've done an experiment to standardise $\ce{NaOH}$ using oxalic acid.

What other primary standard acid can be used to standardise $\ce{NaOH}$?

Can $\ce{HCl, H2SO4, HNO3}$ be used?

I read up and found that:

$\ce{HCl}$ and $\ce{H2SO4}$ are easily diluted, however, the concentration of the "concentrated" solution is not accurately known.

$\ce{HNO3}$ contains a little nitrous acid, $\ce{HNO2}$, which has a destructive action on many acid-base indicators.

Therefore I only found potassium hydrogen phthalate. Is there other primary standard acid that can standardise $\ce{NaOH}$?

  • $\begingroup$ What actually does having a "destructive action on many acid-base indicators" actually mean? And are there concrete examples of it? Thanks! $\endgroup$
    – H_D
    Commented Jul 21, 2022 at 2:17

1 Answer 1


Oxalic acid dihydrate and KHP are the most comfortable acids for standardization, as their content per a unit of measurement (in this case it's obviously grams, as they are solid) hardly changes. When you have liquid acids, besides that what you've already mentioned, they can absorb water and other compounds from air. As they are liquid, people usually measure amount of those compounds by volume, and volume is a variable which depends on temperature, pressure.

  • 3
    $\begingroup$ I don't think any analytical chemist would use oxalic acid dihydrate over KHP. $\endgroup$
    – MaxW
    Commented Nov 6, 2017 at 18:48
  • $\begingroup$ @MaxW True, but oxalic acid has benefits for the amateur chemist in terms of price and availability and it is definitely used as a primary standard. It may not be the professional's choice, but there's nothing wrong with using it. It has all of a primary standard's properties, after all. $\endgroup$ Commented Mar 11, 2022 at 4:43

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