I am grateful to Dr. Grok, because it was his questions that prompted me to think about this topic again!

I was responding to a comment from an extremely friendly reader yesterday and mentioned that triatomic ozone dissolves in water much better than diatomic oxygen. 4.9 liters per 100 liters of water for oxygen and 49 liters per 100 liters of water for ozone.

Why?

At first, I foolishly assumed that the similarity of triatomic molecules of water and ozone created such a huge difference in solubility.

But I immediately objected to myself: Hydrogen chloride, diatomic, has a huge solubility in water, it seems 450 liters in 100 liters of water at zero degrees Celsius.

Then came a “reasonable” and also stupid idea:

It is not water that dissolves hydrogen chloride, but hydrogen chloride that dissolves water, forming hydroxyl – hydrochloric acid.

\But finally!

The main thing is the following more reasonable thought: It’s all about the ratio of the PARTIAL pressures of the two media. The one whose pressure is greater is the one who dissolves better in the other.

For example, gases dissolve much worse in hot water than in cold water.

Why?

After all, the temperature of gas is the same as that of water!

But the PARTIAL PRESSURE OF WATER VAPOR at low temperatures also DROPS SIGNIFICANTLY, and for gases it is higher! Therefore, they dissolve better in cold rather than hot water. Similarly, with hydrogen chloride, it means that the idea of reverse dissolution of water in it is ABSURD!

And salt and sugar, for example, dissolve better in hot water, because the partial pressure of steam increases with temperature and water molecules more easily penetrate into the lattice of sodium chloride or sucrose, destroying it.

At temperatures below four degrees Celsius, the pressure of water vapor is low, and therefore liquid crystal of ice structures begin to form in the water, whose density is lower than that of water, which is why a well–known “anomaly” is observed within these four degrees – the density of water drops and at zero, not liquid, but “normal” solid ice crystals are formed..

Consequently, the water begins to freeze, that is, to turn into ice, not at zero degrees Celsius, but at plus four!

So, in summary, the solubility of substances in each other depends on the ratio of the partial pressures of “steam” of these substances.

Faciant meliora potentes.

If I’m wrong, let my seniors correct me.

15 XII 2025