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. <...>

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

Необходимость международного стандарта на описание качества природного газа была основным доводом для создания в 1989г.
ИСО/ТК 193 с установлением области деятельности, включающей вопросы стандартизации качественных спецификаций газа Природный газ, обеспечивающий 20% первичной энергии в мире, увеличивает свой рынок, но в настоящее время не имеет общепринятого определения качества природного газа