Investigation of Binary Diffusion Coefficients in Argon-Neon Mixtures Using a Loschmidt Cell Combined with Holographic Interferometry Binary diffusion coefficients D-ij were determined for mixtures of argon and neon over the entire composition range using a Loschmidt cell at 293.15333.15K and 110bar. Before the measurements, the different pure gases were added into the two half-cells of the Loschmidt cell. After connecting both half-cells, the change in partial molar density, or rather in the refractive index has been detected simultaneously as a function of position and time within each half-cell using holographic interferometry. The binary diffusion coefficients obtained for the upper half-cell show systematic deviations from literature data. In contrast, the data measured in the lower half-cell are in excellent agreement with literature. Within the measurement uncertainty, the product of the molar density of the mixture and D-ij is not affected by the pressure.