This part of ISO 13317 describes a method for the determination of the particle size distribution of a powder dispersed in a liquid using gravity sedimentation. The measurement of the concentration of solids settling in a liquid suspension is achieved by monitoring the incremental signal absorption from a beam of X-rays. The method of determining the particle size distribution described in this part of ISO 13317 is applicable to powders which can be dispersed in liquids or powders which are present in slurry form. The typical particle size range for analysis is from about to about . The method is used for materials containing particles of the same chemical composition which produce adequate X-ray opacity.