Measurement of the Universal Gas ConstantRUsing a Spherical Acoustic Resonator

We report a new value for the universal gas constant $R:8.314471\ifmmode\pm\else\textpm\fi{}0.000014$ J ${\mathrm{mol}}^{\ensuremath{-}1}$ ${\mathrm{K}}^{\ensuremath{-}1}$. The standard error of $R$ has been reduced by a factor of 5, to 1.7 ppm. $R$ was determined from the speed of sound in argon contained within a thick, spherical shell at the temperature of the triple point of water ${T}_{t}$. The volume of the shell was measured by our weighing the mercury required to fill it at ${T}_{t}$. The molar mass of the argon was determined relative to that of a standard with accurately known chemical and isotopic composition by use of speed-of-sound data.