The Journal of Physical and Chemical Reference Data is published jointly by the National Institute of Standards and Technology and the American Institute of Physics. The objective of the Journal is to provide critically evaluated physical and chemical property data, fully documented as to the original sources and the criteria used for evaluation. Critical reviews of measurement techniques, whose aim is to assess the accuracy of available data in a given technical area, are also included. Papers which report new estimation or prediction techniques and test these techniques against existing databases are also accepted. The journal is not intended as a publication outlet for original experimental measurements such as those that are normally reported in the primary research literature, nor for review articles of a descriptive or primarily theoretical nature.