Overview
ISO 18747-1:2018 - Determination of particle density by sedimentation methods (Part 1: Isopycnic interpolation approach) specifies an isopycnic interpolation method to determine the density of solid particles or liquid droplets dispersed in a liquid. The method exploits the Archimedean principle: a particle stops migrating (settling or creaming) when its density equals the surrounding liquid density. ISO 18747-1:2018 determines particle (buoyant) density by observing migration direction in liquids of different densities under gravitational or centrifugal fields.
Keywords: ISO 18747-1:2018, particle density, isopycnic interpolation, sedimentation methods, buoyant density, centrifugation, particle characterization.
Key topics and technical requirements
- Principle: Uses buoyancy balance (Archimedean principle) - particle migration ceases where particle density equals liquid density (buoyant density).
- Scope: Applies to solid particles and liquid droplets dispersed in a continuous phase; assumes particles share the same material composition.
- Definitions: Distinguishes true particle density, skeletal density, and buoyant (apparent) density depending on pores, coatings, or immobilised surface layers.
- Measurement approaches: Detection of migration direction under gravitational or centrifugal fields; includes techniques to discriminate sedimentation vs creaming/flotation.
- Sample preparation: Guidance on test liquid solutions and dispersing procedures (references ISO 14887:2000 for dispersing).
- Data analysis methods: Graphical interpolation, two‑point interpolation, linear or non‑linear fitting to determine isopycnic points.
- Quality and reporting: Addresses reference materials and estimation/propagation of measurement uncertainty.
- Informative annexes: Practical notes on backscattering discrimination, direct migration velocity measurement, velocity linearization, buoyant density centrifugation, and uncertainty propagation.
Practical applications and users
ISO 18747-1:2018 is useful for laboratories and industries that need accurate particle density information for:
- Formulation scientists and colloid chemists (density matching to optimize dispersion stability)
- Materials scientists and nanotechnology researchers (core/shell and coated particle characterization)
- Quality control and R&D in paints, coatings, pharmaceuticals, food, and mineral processing
- Analysts performing separation-based particle size distribution methods where density is a key input
- Laboratories performing sedimentation or centrifugation-based particle characterization
Applications include kinematic viscosity calculations for dispersions, separation and flotation studies, characterization of capsules or coated nanoparticles, and determining effective/apparent density in complex media.
Related standards
- ISO 14887:2000 - Sample preparation: dispersing procedures for powders in liquids (normative reference)
- ISO 3105 (referenced in introduction) and other parts of the ISO 18747 series for complementary sedimentation and density methods.
This standard provides a robust, traceable framework for determining particle buoyant density using isopycnic interpolation - essential for reproducible particle characterization across research and industrial labs.
Open preview (PDF)Determination of particle density by sedimentation methods — Part 1: Isopycnic interpolation approach
