[spoom]

I put the X-ray in a solution of sodium hydroxide getting a dark liquid with solid waste. What should I do next?

[Arkcon]

I once had a reference that detailed this sort of procedure step-by-step, but I have lost it a long time ago: http://www.chemicalforums.com/index.php?topic=23385.msg88784#msg88784  Briefly, however, I'd expect that the liquid doesn't contain silver, but the solid contains at least some silver oxide.  You should be aware that they sell devices, basically mini-plating cells, to extract silver from photographic wastes -- http://www.finishing.com/3800-3999/3910.shtml  This is only cost effective for massive quantities of photographic waste.