Research into ionic liquids (ILs) has been a very rapidly growing discipline in recent years. ILs have attracted very considerable attention because of their unique properties, which may be useful in new processes and technologies. They have already been studied for a variety of applications such as alternative solvents in organic synthesis and catalysis, reaction media for biocatalysis and biotransformation, in the separation sciences, electrolytes in batteries and solar cells, alternative lubricants, and as media for tissue preservation. ILs have excellent solvation properties, are thermally, chemically and electrochemically stable, and their vapour pressure is negligible. Nevertheless, the same properties that make them attractive replacements for other volatile industrial compounds may render them hazardous to ecosystems. This book discusses several topics that include the pharmaceutical aspect of ILs; the application of ILs to lignin extraction and depolymerisation; recent developments in ionic liquid toxicity assessments; the role temperature, irradiation and oxidation has on the stability of ILs; and analytical methods for determining the constituents of ILs.