Toller,

Assuming that it is held together with dowels and all of the joints are
a bit loose, I have had success with using a rubber mallet to take the
chair apart. I couple of taps with the mallet will tell you whether it
is going to come apart. If the existing glue is brittle it will break
up and the chair will come apart. I have had luck with this technique,
but I suspect that the chairs were not glued together well in the first
place.

Good luck,

Al