Carbon dioxide is the most soluble  of the gases  because as it dissolves it doesn't just go through a physical solution it goes through a chemical conversion  such that carbon dioxide dissolving in water forms  carbonic acid  which, in water  will dissociate into a hydrogen iron and a hydrogen bicarbonate iron  which can further dissociate  this is why I've got a nice wide blackboard and you've only got a piece of A four paper  so you end up with a carbonate iron two hydrogen ions  This system is a dynamic equilibrium.