Throughout the course of history many chemicals have been used or, at least experimented with, as wood preservatives. In the last (nearly) 200 years three types of wood preservatives have come to all but dominate the market:
• Tar oil preservatives
• Organic solvent preservatives
• Water-borne preservatives
More specifically this would be creosote, pentachlorophenol, and chromated copper arsenate (CCA), respectively. While there are other preservative formulations, especially true for water-borne preservatives, these three have dominated the wood preservative market. However, changes may be on the horizon, though, for wood preservation.