Pressure Diffusion and the Ultra Centrifuge. If a sufficiently large pressure gradient can be established, then a measurable separation can be affected. One example of this is the ultracentrifuge, which has been used to separate enzymes and proteins. In the figure, a small cylindrical cell in a very high-speed centrifuge is shown. The length of the cell, L, is short with respect to the radius of rotation, R0, and the solution density may be considered a function of composition only. Determine the distribution of the two components at steady state in terms of their partial molar volumes and the pressure gradient. For simplicity, it is assumed the partial molar volumes and the activity coefficients are constant over the range of conditions existing in the cell.