I would like to test for the reaction between carbonic acid and copper (to simulate the effect of acid rain on copper). However, I find that many supplies failed to provide carbonic acid (either in powder or liquid form). Some says that carbonic acid is unstable and thus cannot supply it. Therefore, I want to make it myself. Are there any simple ways to make carbonic acid from other chemicals (e.g. sodium carbonate?).

Also, I have found some carbonic acid powder in some commercial product such as this one.

But it is for bathing instead of chemical use. Can they produce carbonic acid?

Any answers and comments are welcome. Thank you very much for helping.

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    $\begingroup$ Carbonic acid does not exist $\endgroup$ – Nilay Ghosh Dec 7 '19 at 15:55

Carbonic acid does not exist either in powder either in liquid form near normal conditions.. ( It can be created and detected at special kryogenic or gaseous phase conditions not applicable for its usage as "on shelf acid".)

In a pure form, it exists only as its salts: bicarbonates ( of alkali metals ) and carbonates.

As an acid, it exists at ambient conditions only in minor concentration in water solutions of carbon dioxide ( soda water, mineral water ) and/or bicarbonates ( drink water, mineral water, baking soda solution ), with the equilibrium strongly shifted in favour of the oxide.

$$\ce{CO2(aq) + H2O <<=> H2CO3(aq)}$$

Note that the acidity of acid rain is not based on carbonic acid, that gives to natural rain just mild acidity about $\mathrm{pH=5.7}$.

Acid rain contains traces of strong mineral acids as sulphuric and nitric acid, that are formed from oxides of sulphur and nitrogen, present in air.

I suggest for the testing to use very diluted ( 0.1-1 mM ) solution of one of the above acids, or their mixture.

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    $\begingroup$ Carbonic acid has been reported in the solid phase, though not in a form you can easily make and put in a bottle - sciencedirect.com/science/article/abs/pii/… . See also en.wikipedia.org/wiki/Carbonic_acid $\endgroup$ – Ian Bush Dec 8 '19 at 12:49
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    $\begingroup$ Yes, I know, but I tried to keep it simple for the OP. And yes, I have read and provuded the Wikipedia link as well. Anyway, thanks for comment. $\endgroup$ – Poutnik Dec 8 '19 at 12:51
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    $\begingroup$ @IanBush at any drastic system, you can make chemicals that are not known to exist at room temperature. You can even make compounds of krypton at such systems. So, though Carbonic acid is not known to exist at room temperature theoretically, by changing the conditions drastically like super low temperature, super high pressure, you can confirm its existence. $\endgroup$ – Nilay Ghosh Dec 8 '19 at 13:14
  • $\begingroup$ I think Perrier has a pH about 4.5. Other carbonated mineral waters are probably similar. These would be a good approximation to acid rain. I suggest using a closed vessel to contain the copper, the liquid, and some empty space to contain CO2 and O2 to oxidize the copper. $\endgroup$ – James Gaidis Dec 8 '19 at 14:52
  • $\begingroup$ It is better to follow the real acid rain conditions than simulate it by unnecessarily very different system. E.g the carbonised water has much higher buffering capacity than very diluted mineral acids, brings bubbly conditions and extra support for forming cupper carbonates. $\endgroup$ – Poutnik Dec 8 '19 at 15:06

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