Equivalent diameter based on the sphere

Different equivalent diameters are used depending on the measurement method and the question being asked. The equivalent sphere diameter (d_e) is a measure of the shape of particles. Since real particles are rarely perfect spheres, this value is used. It refers to the diameter of a hypothetical sphere that corresponds to the real particle in terms of a defined property (e.g. volume or surface area).

d_v = (6·V_P / π)^(1/3)

This definition is particularly relevant for volume-based measurement methods such as laser diffraction and for questions where the particle volume per mass or amount of substance is decisive.

Surface equivalent sphere diameter: Let the surface area of any particle be A_P. The surface equivalent sphere diameter d_a is defined such that the surface area of the particle corresponds to the surface area of a sphere.

d_a = (A_P / π)^(1/2)

This definition is important when surface-dependent phenomena are in the foreground, such as solution and reaction kinetics or adsorption on the particle surface.