I have read a formula for porosity that says ratio of volume of pore to total bulk volume of material. From the BET analysis I can get the pore volume of the material. How do I calculate the total bulk volume of the material? Is there any formula?
Pyconometry can give you the total volume and porosity.
You can also use mercury porosimetry, Capillary flow porometry etc to find the pore size and poresize distribution.
Hi Thiruvengadam,
To measure the bulk volume, you have to measure the volume variation when you put your sample in an non-wetting liquid, such as mercury.
Hope it helps
thank you for your valuable answers..... Lijo Francis and Julien Bustillo
You can calculate the porosity of a material using the Archimedes method
If you have XRD data, you can also calculate the bulk volume from the extracted unit cell parameters
Just to clarify, BET strictly refers to surface area measurement not pore volume. A complete gas sorption isotherm , say to P/Po = 0.99 can be used to evaluate total pore volume if it reaches a plateau value (if not, the curve is still increasing at 0.99 this suggests there are larger pores not yet filled so pore volume will be underestimated).
If you additionally know the "true" density of the solid (from literature, XRD, gas pycnometric measurement, etc) then determining porosity is trivial. The reciprocal of density is "specific volume", that is the volume of solid structure per unit mass, say cc/g. Add pore volume, also cc/g, and you have the bulk volume (solid + pores) per unit mass. Porosity is simply the pore volume fraction of the bulk volume (it's usual to express porosity as a percentage, but not absolutely required).
thank you for the valuable suggestion sir.... Martin A Thomas
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