Standard Test Method for Precipitated Silica-Surface Area by Multipoint BET Nitrogen Adsorption

Importancia y uso:

3.1 This test method is used to measure the surface area of precipitated, hydrated silicas that is available to the nitrogen molecule using the multipoint (B. E. T.) method. Single point nitrogen surface area is measured in accordance with the Test Methods D5604.

3.2 Solids adsorb nitrogen, and under specific conditions, the adsorbed molecules approach a monomolecular layer. The quantity in this hypothetical monomolecular layer is calculated using the BET equation. Combining this with the area occupied by the nitrogen molecule yields the total surface area of the solid.

3.3 This test method measures the estimated quantity of nitrogen in the monomolecular layer by adsorption at liquid nitrogen temperature and at several (at least five) partial pressures of nitrogen.

3.4 Before a surface area determination can be made it is necessary that the silica be stripped of any material which may already be adsorbed on the surface. The stripping of adsorbed foreign material eliminates two potential errors. The first error is associated with the weight of the foreign material. The second error is associated with the surface area that the foreign material occupies.

Subcomité:

D11.20

Referida por:

D5604-21, D5900-23, C1274-12R20

Volúmen:

09.01

Número ICS:

71.060.20 (Oxides)

Palabras clave:

nitrogen adsorption surface area; precipitated hydrated silica; silicas; surface area;