Dear Sree,

Usually, you do not have to introduce density to calculate SSA, automatic equipments make the measurement of the empty space before dosing with nitrogen. If you need introducing density, it should be real density measured by helium pycnometry and I suppose that the sample tubes you use are already measured/calibrated.

Introducing density before nitrogen adsorption, your analysis is going to be shorter and you do not have the risk to have helium still adsorbed in very narrow pores when nitrogen adsorption starts. Unfortunately, your SSA determination is going to be less precise and finally you are obliged to do He pycnometry in a second equipment, so you are not really saving time... What I do is measuring empty volume after nitrogen or CO2 adsorption.

Hi Sree. What type of system are you using to determine your BET? Most systems do not involve density in the SSA calculation. Density is used for further determinations. If you want to use density, I would advise you to use true density.

Dear Amaro....thanks for your response.. We are having Thermo Scientific surface area analyzer (volumetric based method), we have to feed density to process the data even for surface area calculation

Dear Sree,

Usually, you do not have to introduce density to calculate SSA, automatic equipments make the measurement of the empty space before dosing with nitrogen. If you need introducing density, it should be real density measured by helium pycnometry and I suppose that the sample tubes you use are already measured/calibrated.

Introducing density before nitrogen adsorption, your analysis is going to be shorter and you do not have the risk to have helium still adsorbed in very narrow pores when nitrogen adsorption starts. Unfortunately, your SSA determination is going to be less precise and finally you are obliged to do He pycnometry in a second equipment, so you are not really saving time... What I do is measuring empty volume after nitrogen or CO2 adsorption.