Is it true that CO2 escapes faster when you store a (once opened) bottle lying down instead of standing?

Answer

Hi Mark,

I don’t think that’s right. We are talking about a not so simple system here.

It is about CO2 dissolved in water. We know from experience that achieving the correct balance between water and CO2 is very slow. CO2 is added to high-pressure spray water (+/- 10 atmospheres), causing it to dissolve in the water. The cooler the water, the better this works. In the factory, the water is therefore cooled before CO2 is added. Solution equilibrium is reached relatively quickly, and then an additional amount of pressurized CO2 is added to the bottle before it is capped.

Now everything depends on the temperature and on what we call “nucleation”.

When the bottle is opened, you know from experience that some of the CO2 escapes – the pressure above the water disappears, and the dissolved CO2 wants to escape. However, this does not always work smoothly – it works much better when the water is warmer, because the correct balance then strives for water with less CO2. But reaching the new equilibrium takes time – a lot of time. And before CO2 can escape from the water, it must first form a bubble, and the number of germs that exist in the bottle for this purpose is limited – so the number of bubbles, and the rate at which the CO2 escapes, is also limited.

As soon as you close the bottle again, CO2 will continue to escape from the water until the pressure above the water surface is equal to the equilibrium pressure of the CO2 dissolved in the water at the temperature at which the water is located. The next time you open the bottle, some of the CO2 will escape again, so the water will fizz even less the next time you open the bottle.

I haven’t done any rigorous research on it, but I don’t suspect that the area of ​​contact between the water and the atmosphere above will affect the final equilibrium. It might take a little longer to reach equilibrium if the freshly closed bottle is standing up instead of lying flat, but I don’t think it will make much of a difference.

How much CO2 your water will still contain will depend on the following factors:

*the temperature of the water each time the bottle has been opened. Warmer water means there is more CO2 above the water, and less in the water – so more escapes when the bottle is opened.

*how long you leave the bottle open. The longer it is open, the more CO2 will have escaped.

*how many times the bottle has been opened. Every time a new dose of CO2 escapes

*the potential for bubble nucleation. If you have just shaken the bottle, much more CO2 will escape than if it had been sitting quietly for a while. For fun, try throwing a teaspoon of sugar into a bottle of sparkling water and see what happens.
(or the famous diet soda + mentos experiment, which also has to do with nucleation of the bubbles)

* the liquid level in the bottle – the less liquid there is, the more CO2 can escape from the liquid before enough pressure has built up in the “empty” part of the bottle for equilibrium.

You may only be able to observe the effect of the bottle lying flat or not if you do not give the bottle enough time between two successive openings to regain its equilibrium pressure above the liquid – the other effects seem to me to be much more important.

I hope that clarifies it a bit!