Specific surface area "SSA" is a property of solids which is the total surface area of a material per unit of mass, solid or bulk volume, or cross-sectional area.
It is a derived scientific value that can be used to
determine the type and properties of a material (e.g. soil). It is defined either by surface area divided by mass (with units of
m²/kg), or surface area divided by the volume (units of m²/m³ or m−1)
Measurement
The value obtained for specific surface area depends upon the method of
measurement. Several techniques have been developed to measure the specific
surface area of clays, including methylene blue (MB) stain test, ethylene
glycol monoethyl ether (EGME) method, Brenauer-Emmett-Teller (BET)adsorption method and Protein Retention (PR) method.
Calculation
The SSA can be simply calculated from a particle size distribution, making some assumption about the particle shape. This method, however,
fails to account for surface associated with the surface texture of the
particles.
Adsorption
The SSA can be measured by adsorption using the BET isotherm. This has the advantage of measuring the surface of fine structures and
deep texture on the particles. However, the results can differ markedly
depending on the substance adsorbed.
Gas permeability
This depends upon a relationship between the specific surface area and the
resistance to gas-flow of a porous bed of powder. The method is simple and
quick, and yields a result that often correlates well with the chemical
reactivity of a powder. However, it fails to measure much of the deep surface texture.
