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I pour 1 gram of ascorbic acid (a white powder sold by the kilogram as food-grade thus hopefully dextrorotatory) at 25°C (it's hot in Paris) into a 1 liter bottle of carbonated water at 6°C (drinking-grade, or so tells the public fountain dispensing it, complete with analysis of the overall 420 milligram/liter of dissolved minerals).

I observe significant sparkling as the powder descends and dissolves. Nothing near Mentos/Coke-grade, but still it can't be missed.

Why? Is there some chemical reaction? Or is it only de-saturation of CO2 by some physical phenomena?

Update: I don't know the initial pH of the carbonated water. Before carbonation, it's reportedly about 8.7 on a yearly average, with regulatory limits [6.5, 9].

Links to Safety data and LD50 information on ascorbic acid. Seriously, avoid inhalation of the stuff or getting any in the eyes. I recommend against consumption of the result of that or other experiment by human or other animal.

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    $\begingroup$ The powder probably acts as nucleation site for bubbles of $\ce{CO2}$ to form in the supersaturated carbonated water. Changing the pH turns some hydrogen carbonate into carbonic acid/$\ce{CO2(aq)}$ as well, but this is probably the smaller effect because most of the carbonate is in that form already when you mix pure water with carbon dioxide. What is the initial pH? $\endgroup$
    – Karsten ♦
    Commented Jul 27 at 15:58
  • $\begingroup$ I don't know the initial pH of the carbonated water. Before carbonation, it's reportedly about 8.7 on a yearly average, with regulatory limits [6.5, 9]. $\endgroup$
    – fgrieu
    Commented Jul 27 at 16:30
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    $\begingroup$ This is an uncontrolled experiment. One gram is a lot of Vitamine C ~10X the MDR, also a lot of heat to add to the water. The CO2 water is probably slowly warming so most likely slightly supersaturated and subject to perturbation releasing CO2. Ascorbic is essentially a lactone and not appreciably acidic so should not increase the acidity of carbonated water. $\endgroup$
    – jimchmst
    Commented Jul 27 at 18:42
  • $\begingroup$ @jimchmst: on third though, you are right, and I added a paragraph to the Q. $\endgroup$
    – fgrieu
    Commented Jul 27 at 20:13
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    $\begingroup$ If you added near any powder you would see sparkling of oversaturated $\ce{CO2}$ solution. Acids may just boost it if there is significant amount of $\ce{HCO3-}$, converting it to $\ce{CO2}$. pH 8.7 is very high, it seems there must be $\ce{HCO3-}$. $\endgroup$
    – Poutnik
    Commented Jul 28 at 7:26

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Almost anything can nucleate bubble evolution when pressure is suddenly released.

  • Shake a soda (pop, "Coke" [Atlantan], "tonic" [Bostonian]) bottle before opening.
  • Immerse the pop bottle in an ultrasonic bath.
  • Repeatedly scratch the inside of a glass filled a carbonated beverage with a glass rod.
  • Pour almost any powder, crystal, gravel, or other finely divided substances into freshly-poured pop.

You're dealing with a substance in a metastable (or downright unstable) state, read to "pop" off.

A similar effect is seen in supercooling and superheating, and is the reason cooks and chemists use boiling stones to decrease violent bumping.

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