Density

There are several types of densities, each specifically defined.
Examples are absolute density, bulk density and envelope density.  

Particle & Surface Sciences Analytical Service Laboratory offers analyses that measure density consistent with each of the following density types.

Absolute Density
Bulk Density
TAP. Density
Envelope Density  

 Absolute Density, sometimes called true or skeletal density, is determined by the 
Accupyc 1330 which uses a gas displacement technique to determine the volume of sample under test. The density is calculated using the sample weight which was determined using a balance. The instrument measures the volume of the sample, excluding interstitial voids in bulk powders and any open porosity in the individual particles, to which the gas has access. Internal (closed) porosity is still included in the volume. Almost any solid samples as well as some fluid samples can be measured by this technique. This density can also be measured using a mercury porosimeter.

Bulk density  is defined as the total volume of material including any interstitial volume and any open or closed pore volume. Particle & Surface Sciences Analytical Services Laboratory uses a Mercury porosimeter Autopore II 9220 for this analysis. The technique employs a mercury displacement to determine volumes. This technique typically pertains to powders but can also be used for any bulk material.

Tap density, as with bulk density, includes the interstitial volume and pore volume in its calculations.

Envelope density is the mass of an object divided by its volume where the volume includes that of its pores and small cavities. This density is measured using the AutoPore II 9220.

The specific pore volume and percent porosity of a sample can be determined by subtracting the skeletal volume from the envelope volume prior to doing the remaining computations.

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