BS ISO 9277. Determination of the specific surface area of solids by gas adsorption. BET method.
|Standard number:||21/30419294 DC|
|Status:||Draft for Comment|
This standard 21/30419294 DC BS ISO 9277. Determination of the specific surface area of solids by gas adsorption. BET method. is classified in these ICS categories:
- 19.120 Particle size analysis. Sieving
This International Standard specifies the determination of the overall1
For solids exhibiting a chemically heterogeneous surface, e.g. metal-carrying catalyst, the BET method gives the overall surface area, whereas the metallic portion of the surface area may be measured by chemisorption methods.
Gas adsorption allows for assessing surface area of nonporous materials and porous materials with accessible porosity (which depends on the chosen adsorptive). The BET method is applicable only to adsorption isotherms of type II (disperse, nonporous or macroporous solids) and type IV (mesoporous solids, there are however) (see Figure 1. Type II and Type IVa isotherms. However, in the case of Type IVb isotherms, caution is required since pore condensation may occur at quite low p/p0 (see 2015 IUPAC recommendations, ref. . The BET method cannot reliably be applied to solids which absorb the measuring gas. A strategy for BET area determination of microporous materials (type I isotherms) is described in Annex C.