While some fruits of scientific collaboration, such as CERN, have broken through to reach the general public, others that have had as much impact on our lives are not so well known. Thermodynamic tables are one of these, so let me focus for a bit on the US side of the topic.

As our understanding of pure substances and the principles of energy conservation developed during the 19th century, it became clear that each pure substance is characterized by a unique set of thermodynamic properties, including the heat of formation, that is the heat that is either released or absorbed when that substance is formed from its elements.

Over almost a hundred years, scientists published values for these heats of formation. It was a growing set of data with a lot of value, but that it was also very disorganized, subject to different reference points and standards. A coordination effort was needed and, rather surprisingly at the time, it was kicked off by the US.

In 1919, just after WWI, American delegates to the meeting of the International Union of Pure and Applied Chemistry proposed the curation and compilation of tables of physical properties of chemical substances and key technological materials. The IUPAC approved, and one US organization, the National Research Council, took the responsability of raising the funding and executing the project. This led to the International Critical Tables. International editors from leading scientific countries were included, with the notable exception of Germany.

The thermochemistry sections included heats of formation, heats of combustion, heats of transition/fusion/vaporization, specific heats, melting and boiling points, vapor pressures, and densities of various substances. It is the first attempt at critically reviewing almost 100 years of data and provide a single source of thermodynamic information.

The National Research Council itself was also a product of WWI. US President Woodrow Wilson established the NRC in 1916 as the operational arm of the US National Academies of Science, tasked with mobilizing and coordinating American science for national defense. Some of its roles during WWI include coordinating US research efforts for submarine detection and submarine warfare.

From there, two scientists from the National Bureau of Standards, Rossini and Bichowsky, took on the challenge of revising and extending the thermochemistry section of the ITCs. This led to the publication in 1936 of “The Thermochemistry of Chemical Substances”, which in particular tried to standardize all heat data to a common reference temperature and pressure. In 1942, Rossini founded the Thermodynamics Research Center inside of the NBS. There he took on Project 44 (you’ve got to love the name) from the American Petroleum Institute, which aimed at improving the thermochemical data of hydrocarbons. The TRC is still ongoing and the NIST Chemistry Webbook feeds in part from all these efforts.

Another initiative carried out in parallel was the development of the JANAF Thermochemical Tables in 1960. These were motivated by the US need for high temperature data for rocket propulsion R&D. This was a defense need (Joint Army-Navy-Air Force), so a new program, JANAF, was set up to generate and evaluate data for a wider set of elements than that of Project 44 and across a much larger temperature range. The NBS published the results, and JANAF eventually became a fully NIST-run effort (The NBS was renamed to NIST).

In the 1960s NASA took on the available thermochemical data and reformatted it into a polynomial form that simplified the the use of thermochemical data by computer simulations. These formats are still widely used. In the 1980s, Sandia National Laboratories developed CHEMKIN, a chemical kinetics software package. To calculate things like equilibrium constants, reaction reversibility, and heat release, CHEMKIN needs the thermodynamic properties of every species in a reaction mechanism as a function of temperature, so it adopted the NASA polynomial format.

What I find fascinating about this process is that it combines international collaboration, private fundraising (the ITCs were not federally funded), individual drive, government funding support to academia and industry, and then the creation of stable programs inside the US government. It is also a great example of how the US gov’s investment in science in the 20th century really made a difference. Still, fastforward to today, and I wish that it was easier to pull thermodynamic data from a common repository. They play a key role in the chemical reacting flow problems at the core of many synthesis techniques, and yet each lab is still reinventing the wheel, manually combing through papers and databases and compiling their own data.