Not real prominent on the net but a chemist got me using this looking for gold recovery patents so thought I would post it. Great for ideas on how you may want to do something, and many things are just plain interesting. Many of the older patents are fairly simple and possibly able to be replicated at home. I am currently looking at a 1940 ore grinder that I think I can build.
PDF's can be downloaded and printed.
http://www.google.com/patents?hl=en
Google Patents
http://www.google.com/patents?id=SV1uAAAAEBAJ&pg=PA77&dq=2239952#PPA77,M1
patents