The Boltzmann project

Area of Science:

• Thermodynamics
• Metrology
• Physical Chemistry

Background:

• The International Committee for Weights and Measures (CIPM) recommended redefining fundamental units.
• The redefinition of the kelvin involves fixing the Boltzmann constant (k).
• Accurate determination of the Boltzmann constant is crucial for metrology.

Purpose of the Study:

• To review recent determinations of the Boltzmann constant (k).
• To assess the suitability of these determinations for the new kelvin definition.
• To highlight the successful completion of research activities in temperature science.

Main Methods:

• Review of experimental and theoretical determinations of the Boltzmann constant (k) from the last decade.
• Analysis of the uncertainty associated with these determinations.
• Evaluation of the impact on thermodynamic temperature measurements.

Main Results:

• The Boltzmann constant (k) will be fixed at 1.380 649 × 10^-23 J K^-1.
• The redefinition allows for a relative standard uncertainty of 3.7 × 10^-7 for the triple point of water.
• This level of uncertainty (0.10 mK) is sufficient for all practical purposes.

Conclusions:

• The redefinition of the kelvin is a significant advancement in metrology.
• Research on Boltzmann constant determinations has successfully concluded.
• The new definition ensures stable and accurate thermodynamic temperature measurements.