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I have new bottles of 1 N hydrochloric acid from Fisher. The acid comes standardized from the company:

Standardized at 25 °C to pH 8.2 against sodium hydroxide that has been standardized against NIST™ potassium acid phthalate.

Will it remain standardized after opening the bottle, or do we have to standardize it regularly?

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    $\begingroup$ Most likely, yes, it will require standardization at some point. If you are working at the analytical lab, there must be a schedule for testing reactants to make sure they are of analytical grade and the concentrations are correct. $\endgroup$ – andselisk Apr 30 at 2:36
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    $\begingroup$ Not just hydrochloric acid, concentration of any acid changes over time. $\endgroup$ – Nilay Ghosh Apr 30 at 3:38
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First of all, check the expiry date. In general HCl solutions are secondary standards. 1 N is just a approximation. You need to standardize it every time with a primary standard such as sodium carbonate. On the other hand, constant boiling HCl is indeed a primary standard. It is not very well known, perhaps because modern analytical chemists have become lazier.

Constant-boiling hydrochloric acid John L. Sheldon J. Chem. Educ., 1935, 12 (8), p 377 https://pubs.acs.org/doi/abs/10.1021/ed012p377

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  • $\begingroup$ Boiling HCl standard is quite inconvenient to manage. The 1N one need not to be checked every time, it is enough to do periodically, with monitoring the trend. $\endgroup$ – Poutnik Apr 30 at 5:42

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