The National Institute of Standards and Technology (NIST, published an online database detailing the physical properties of ionic liquid solvents. The solvents, which are characterized by salts that melt below the boiling point of water, are gaining significant interest from chemical engineers and others designing “green” industrial processes.

Ionic liquids are unique because they don’t have a measurable vapor pressure at room temperature. With typical vapor pressures in the range of 10-10 pascal (10-14 PSI), ionic liquids have essentially no vapor emissions, which NIST says makes them excellent candidates for “green solvents” to replace hazardous, air-polluting organic solvents like acetone and benzene. Also, the NIST notes that with dozens of anions and cations to choose from, they can be tailored to specific needs and may be particularly useful as solvents for biocatalysis.

According to NIST, one problem chemical engineers have faced in employing ionic liquids is that there has been a lack of organized, reliable data on the basic physical properties of the solvents, which is critical information for designing industrial processes. NIST, in cooperation with the International Union of Pure & Applied Chemistry (IUPAC), has created ILThermo, the IUPAC Ionic Liquids Database. Launched at the end of July, ILThermo is a free, Web-based research tool that allows users worldwide to access an up-to-date data collection of thermodynamic, thermochemical, and transport properties of pure ionic liquids, as well as binary and ternary mixtures.

Assembled from published data, ILThermo aims to include information on structure, thermodynamic, and transport properties of pure ionic liquids and mixtures. The inaugural version of the database includes data for more than 200 ions and more than 300 ionic liquids. Uniformly calculated uncertainties (following guidelines adopted by the major scientific unions and NIST) for each data point in the collection are also provided, making it easier to compare the quality of different measurements.

The ILThermo database is located at