Determination of porosity
Contents
Determining porosity values for porometry data.
To determine an accurate porosity value for your sample the recommended technique is to measure the absolute density and volume of the sample before or after the porometry analysis, using a technique such as helium pycnometry. You could also use the quoted density value from the manufacturer. Once you have the absolute density from helium pycnometry all you need to do is calculate the porosity value by using the simple formula.
You can calculate the envelope volume simply by using the sample thickness multiplied by the surface area of your sample, which are found in the data file.
You can also obtain a porosity value by using one of the alternatives to pycnometry listed below:
| • | Use microscopy images to work out the void volume percentage relative to the total volume and this provides a reasonable estimate of porosity. |
| • | Porosity determined by mercury porosimetry |
| • | Porosity determined using an imbibition method described below |
Determination of porosity by imbibition method
To calculate the effective porosity (related to the interconnected pore space) you can use an imbibition method, as long as you know the density of the wetting fluid.
| 1. | Weigh the sample and record the weight |
| 2. | Saturate the sample in a wetting fluid |
| 3. | Weigh the sample after saturation |
| 4. | Work out the difference in weight between the initial and saturated sample which corresponds to the density of the wetting fluid multiplied by pore volume (porosity) |
| 5. | You can now work out the pore volume by dividing the difference in weight by the density to give you the pore volume, if you then divide the pore volume by the total volume you calculate the effective porosity. |