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The structures of deuterated, protonated, and relithiated forms of MnO2 spinel, obtained by ion exchange of Li ions with D or H in a well-crystallized spinel Li1.27Mn1.73O4 compound, have been determined by powder neutron diffraction. Refinements were carried out using the Rietveld method of powder profile analysis in the space group Fd3m. Li ions are removed from both tetrahedral 8a and octahedral 16d sites when Li1.27Mn1.73O4 is contacted with DCl or HCl solution. The neutron diffraction data show that deuterium and hydrogen ions are predominantly incorporated into the crystal as −OD and −OH by bonding to lattice oxygen atoms without any other major change to the MnO2 spinel structure. The −OD and −OH groups are directed into the interstitial space of the 8a tetrahedra, but with an orientation which suggests that the deuteron or proton site is favored for occupation only when the nearest neighbor octahedral 16d site contains no Mn ion. When the protonated compound is contacted with LiOH solution, reinserted Li ions relocate on tetrahedral 8a sites in preference to vacant octahedral 16d sites in the MnO2 framework.

The thermal conductivity of ethane in the critical region has been measured isochorically at densities up to 1.76 times the critical density and at temperatures down to 0.13 K above the critical temperature. The measurements were performed with a thermal conductivity apparatus based on the parallelplate method. The experimental accuracy was 0.5 to 5 %, depending on the distance to the critical point. The experimental results agree well with a recently developed crossover theory for the thermal diffusivity of fluids in the critical region.

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An equation based on the hydrodynamical equations of change is solved, analytically and numerically, for the calculation of the viscosity from the mass-flow rate of a steady, isothermal, compressible and laminar flow in a capillaiy. It is shown that by far the most dominant correction is that due to the compressibility of the fluid, computable from the equation of state. The combined correction for the acceleration of the fluid and the change of the velocity profile appears to be 1.5 times larger than the correction accepted to date.