Measuring the force between air molecules

[tm007]

If there was an atractive force between air molecules, how could this be measured? The force should be small. In the range of the force between watermolecules (hydrogen bond).

 

[Nugatory]

A previously unknown force between air molecules would show up as unexpected differences between the behavior of a volume of air and a volume of ideal gas.

(But do note that there’s no such thing as an “air molecule” - air is a mixture of nitrogen molecules, oxygen molecules, some stray argon atoms, and other odds and ends)

 

[snorkack]

A previously unknown force between air molecules would show up as unexpected differences between the behavior of a volume of air and a volume of ideal gas.

(But do note that there’s no such thing as an “air molecule” - air is a mixture of nitrogen molecules, oxygen molecules, some stray argon atoms, and other odds and ends)

That´ s one thing.
Also if air molecules are attracted to each other then on throttling air, air ought to cool as those attractive forces are overcome.
For an ideal gas should have neither attractive nor repulsive forces between molecules, and should neither cool nor heat on throttling.
But how do you tell the difference between a gas having no attractive or repulsive forces vs. a gas having both attractive and repulsive forces but those balanced between each other?
How do you measure attractive forces in presence of repulsive forces?