I'm starting to sell off some of my alchemy & history of science books on ebay.co.uk (to raise funds to buy some more).
Nothing of great rarity, but some quite interesting basic material and pamphlets. The first batch includes Collectanea Chemica (1991 reprint), Waite's Turba Philosophorum (1973 reprint) and C.J.S. Thompson's Lure and romance of alchemy.
Rather than continuously clutter up this group, if you are interested, I suggest you check my eBay name 'alanpritchard' regularly or add me to your Favourite Sellers list.