Subject: What's the relationship between gases and dissolved gases?

I understand that Henry's Law defines the relationship between a gases pressure 
above a liquid and it's concentration within that liquid.  And, Henry's Law 
Constants seem to be, in essence, an empirically determined value which 
quantifies this relationship.  But, what is the "driving force" (logic) behind 
this balance?  Does understanding this logic make it possible to determine the 
gases concentration within the liquid, knowing it's pressure above, without 
knowing the Henry's Law Constant?

In Message ID # 923925416.Ot, Mr. Kingsley refers to a beer bottle at 
equalibrium, saying "the partial pressures of the carbon dioxide in the air and 
in the liquid are the same".  This is an interesting thought, yet it confused 
me.  First, how do you determine the partial pressure of the gas in the 
liquid?  And, wouldn't this infer that the dissolved gas concentration is 
dependent on pressure only?  Wouldn't that, in turn, make Henry's Law Constants 
the same for all gases?

Please help...I feel like I'm missing something obvious...

Re: What's the relationship between gases and dissolved gases?