an x - ray sedimentation particle size analyzer in which data is taken only at particular positions along the sedimentation cell , and each such position is individually calibrated . presentation of the data in the form of a particle size distribution curve can be accomplished very accurately using interpolation techniques . the sedimentation cell design is free of the effects of undesirable density gradients , capable of detecting and removing bubbles , capable of attaining a highly uniform dispersion of sample prior to sedimentation , and including a safety interlock device for blocking x - ray projection when the cell is being accessed .