What is ISO 18747‑2- Multi-velocity approach about?
ISO 18747‑2 is an international standard on determining particle density by sedimentation methods.
ISO 18747‑2 specifies an in situ method for the determination of the density of solid particles or liquid droplets (herein referred to as “particle”) dispersed in the liquid continuous phase. The method is based on the direct experimental determination of particle velocity in these liquids or media in gravitational or centrifugal fields based on Stokes law.
The particle density is calculated experimentally determined particle velocities in different liquids or media, considering their dynamic viscosities and densities, respectively. The approach does not require the knowledge of particle size distribution but assumes that sedimentation relevant characteristics (e.g., volume, shape, agglomeration state) do not change.
Note: ISO 18747‑2 does not consider polydispersity about particle density, i.e., all particles are assumed to be of the same material composition.
Who is ISO 18747‑2- Multi-velocity approach for?
ISO 18747‑2 on determining particle density by sedimentation methods is relevant to:
- Physio-chemical engineers
- Testing authorities
Why should you use ISO 18747‑2- Multi-velocity approach?
Dispersions are widely used in industry and everyday life. There is a need to understand the density of dispersed particles or droplets, e.g. for physicochemical calculations such as kinematic viscosity of dispersions, determination of particle size distribution by sedimentation or acoustic techniques, particle characterization by field-flow approaches, optimization of dispersion long-term stability by density matching as well as, more generally, characterization of particles (e.g., composition, internal phase content of double emulsions or homogeneity of hollow capsules) in manifold academic and industrial areas.
The density of a body is defined as its mass divided by its volume. The geometrical volume (defined by length, width, and thickness) and the volume relevant for the determination of density may differ due to surface irregularities, fractures, fissures, and pores or the measuring techniques employed.
ISO 18747‑2 describes the density determination of micro-particles, especially nanoparticles dispersed in a liquid, is difficult not only due to the determination of mass and volume for small particles but also due to the fuzzy boundary between the liquid and the particle. In the context of 18747‑2, the Stokes diameter and diameter of the enveloping sphere/hull are particularly relevant.
Overall, 18747‑2 is useful as it assists the user with the sedimentation techniques that allow, in situ density determination, of particles dispersed in liquid continuous phases. 18747‑2 provides you with comprehensive information useful throughout the process of determination of the density.
