# Nyvlt coefficients

This author avoids using the mediation of the equivalent sphere. Usually, crystals have three main dimensions A, B and C, so that:

The intermediate dimension B is the only dimension that can be correlated with granulometric analysis by sifting. Consequently, we define the coefficients directly:

Q and E are the volume and the surface of a crystal taken at random. All of the crystals are supposed to be geometrically similar, which ensures the independence of *a* and P relative to the crystal size.

If the form of the crystals changes through growth, then the growing rate will be:

Note that if R is the rate of orthogonal growth for a face perpendicular to dimension B, the crystal growth rate is:

# The importance of form: porosity

The porosity ? of a crystal bed is a direct function of the form. Non-pressed loose fibers 0.9 < ? < 0.99

Loose plates 0.80 < s < 0.9

Irregular but equidimensional particles 0.4< ? < 0.7

Spheres *г* # 0.4

Tight parallel fibers *г* # 0.2

A minimum volume is required for explosives. It is advantageous that these particles be spherical.

Silver halide used for photography takes the form of plates due to the very high non-sphericity coefficient for this configuration. These halides offer a maximum surface volume and, for a given quantity of silver, optimal light sensitivity.