The gas constant (also known as the universal or ideal gas constant, usually denoted by symbol R) is a physical constant used in equations of state to relate various groups of state functions to one another. It is another name for the Boltzmann constant, but when used in the ideal gas law it is usually expressed in the more convenient units of energy per kelvin per mole rather than simply energy per kelvin per particle.
where P is the pressure of an ideal gas
T is its temperature
is its molar volume
This can also be written as:
R appears in the Nernst equation as well as in the Lorentz-Lorenz formula.
The two digits between the parentheses denote the uncertainty (standard deviation) in the last two digits of the value.