How do they decaffeinate coffee?

Someone told me that coffee beans are decaffeinated by using dry cleaning fluid
as a solvent to rinse out the caffeine. Is this true? If it is true, why dry cleaning fluid?

One of the processes uses Methylene Chloride, because Caffeine dissolves in it.

See: http://recipes.howstuffworks.com/question480.htm

I don’t think Methylene Chloride is used in commercial dry cleaning, but it’s a powerful solvent, and will dissolve many plastics.

Nowadays they increasingly use supercritical (liquid) carbon dioxide, I believe. Basically you need a solvent that will dissolve the caffeine out of the beans. To stop the flavour also being removed, they add the flavour to the solvent.

Because dichloromethane is an excellent solvent for caffeine, yet doesn’t extract many of the bean’s flavor components.
There are lots of other ways by which coffee is decaffeinated too.
This wikpedia article covers them nicely: Decaffeination

Colophon is right, but there is more magic to it than that. Supercritical CO2 dissolves different things under different conditions. For many things, solution only works above some pressure termed a threshold pressure. Caffeine, as well as various flavoring oils and essences that are part of coffee beans, are like this. The beauty of supercritical CO2 is that they can go just past the threshold pressure for caffeine, take the solution elsewhere with all these things in it, lower the pressure below caffeine’s threshold so it precipitates out, and then return the solution and exit the supercritical state to redeposit all the nice essences.

There is usually water present too (I forget why). That means they can call it the “sparkling water” process. But it’s not like they’re using Perrier.