The Handbook of Chemistry and Physics has always provided a thorough range of critically evaluated data in a convenient, one-volume format. Over the last 10 years, revisions to the book have supported the advances in semiconductors and high-temperature superconductors; addressed environmental concerns by providing data on pollutants, contaminants, global warming, and ground water contamination. In the last several years, the handbook has added, revised, or updated 95% of its information. The 81st edition includes eight new tables and forty revised tables.