Removing Tile Cement

Is there an 'easy' way of removing old cement from the back of tiles to be re-used?
I had to remove tiles in the bathroom when i installed a new vanity (bigger than old unit) and i now have to put them back on.
I can ( I hope ) carefully grind the old cement off but i have a very limited supply of tiles, probably only one or two spare, and i can't afford to break any. I've tried getting new tiles in the same pattern but they went out of production about 20 yrs ago. :C
Is there anything that disolves or significantly softens tile adhesive?
The only other option i can see is to retile the whole bathroom including the shower recess and i do not want to do that.

Tony

How about soaking them in a Hydrochloric acid bath. If you have a spare broken bit it is worth trying it out to make sure the acid doesn't stain the tile.
I've never done this, so its a guess. In theory it should be Ok the acid should only attack the lime in the cement not you ceramic?? (I'm assuming) tile.
Give it a test first and use about 12 water to 1 acid. Read the instructions and be carefull about splashes and fumes.

BT,
They are ceramic, glazed tiles.
I have a few broken pieces. I'll give it a go.
Thanks.

Tony