AbstractMeasurements of laminar dispersion in a capillary have been used to determine the molecular diffusion coefficients of hydrogen and helium dissolved in water over the temperature range of 10° to 55°C. Literature correlations did not predict realistic values of the diffusivities for the hydrogen—water and helium—water binaries. A statistical analysis of the experimental diffusion coefficients indicated that they could be related to the absolute temperature by a semiempirical correlation, which may be considered an extension of the well‐known Wilke‐Chang correlation. This relation was based on the absolute reaction rate model of liquids.