British Standard Institution definition of density

True density: The mass of a particle divided by its volume, excluding open and closed pores.

Apparent density: The mass of a powder divided by its apparent volume

Bulk density: The apparent powder density under defined conditions

Tap density: The apparent powder density obtained under standard conditions of tapping

You may possibly want to check:

http://www.who.int/medicines/publications/pharmacopoeia/Bulk-tapped-densityQAS11_450FINAL_MODIFIEDMarch2012.pdf

http://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/revisions/m99375-bulk_density_and_tapped_density_of_powders.pdf

https://www.ecn.nl/docs/society/horizontal/CEN-Determination%20of%20bulk%20density,%20Version%20240805.pdf

British Standard Institution definition of density

True density: The mass of a particle divided by its volume, excluding open and closed pores.

Apparent density: The mass of a powder divided by its apparent volume

Bulk density: The apparent powder density under defined conditions

Tap density: The apparent powder density obtained under standard conditions of tapping

Shefali Bhardwaj

True density is constant value for a matter.  True density is the density of the solid material. As a geologist, calcite mineral has true density of 2.72 gr/cm3. 

Apparent density is similar to the true density except the volume of closed pores is also included so it is less than true density. for example a crabonate rock which is composited of pure calcite, show apparent density  less than  2.72 gr/cm3

Bulk Density: Bulk density is a characteristic of a volume of divided material such as powders, grains, and granules. It includes the volume of the solid material, open and closed pores, and the interparticle void. so its less than Apparent density for same sample.

Envelope Density: Like bulk density, envelope density is determined from the volume of the solid material, open pores, and closed pores. Envelope density is determined for a single, consolidate quantity of material, therefore there are no interparticle voids between packed particles.

The following discussion addresses both bulk density and apparent density: https://www.researchgate.net/post/what_is_the_difference_between_Bulk_density_and_Apparent_density

I have discussed the determination of bulk density by the Archimedes method for porous samples elsewhere at this forum: https://www.researchgate.net/post/How_do_i_calculate_for_percentage_porosity_in_a_ceramic_material/1

Thank you!

Kind Regards!

BULK DENSITY

The bulk density of a powder is the ratio of the mass of an untapped powder sample and its volume including the contribution of the inter particulate void volume. Hence, the bulk density depends on both the density of powder particles and the spatial arrangement of particles in the powder bed. The bulk density is expressed in grams per millilitre (g/ml) although the international unit is kilogram per cubic metre (1 g/ml = 1000 kg/m3 ) because the measurements are made using cylinders.

It may also be expressed in grams per cubic centimetre (g/cm3 ).

The bulk density of a powder is determined by measuring the volume of a known mass of powder sample, that may have been passed through a sieve, into a graduated cylinder (Method A), or by measuring the mass of a known volume of powder that has been passed through a volumeter into a cup (Method B) or a measuring vessel (Method C).

TAPPED DENSITY

volume determined by the use of graduated cylinder, the cylinder can be tapped giving a measure of the so called Tapped Density.

The apparent powder density obtained under standard conditions of tapping.

The tapped density is an increased bulk density attained after mechanically tapping a container containing the powder sample. The tapped density is obtained by mechanically tapping a graduated measuring cylinder or vessel containing the powder sample. After observing the initial powder volume or mass, the measuring cylinder or vessel is mechanically tapped, and volume or mass readings are taken until little further volume or mass change is observed. The mechanical tapping is achieved by raising the cylinder or vessel and allowing it to drop, under its own mass, a specified distance by either of three methods as described below. Devices that rotate the cylinder or vessel during tapping may be preferred to minimize any possible separation of the mass during tapping down.

True density: The mass of a particle divided by its volume, excluding open and closed pores. as true/skeletal volume for true density measurement- includes volume of solid phase only and any closed pores within that are not open to the outside surface. For regular shapes this is easy to measure using an accurate balance and a ruler, for irregular or fractured shapes we employ the Archimedean principle of fluid/gas displacement to measure the volume. The gas pycnometry operating principle is Gas Law: PV = nRT Where P is the gas pressure, V is the volume containing the gas, n is the number of moles of the gas, R is the universal gas constant and T is the temperature of the gas. Introducing a sample into an analysis chamber of a known volume we determine the volume of a gas displaced by the sample and true volume of the analysed material. Mo

Apparent density: The mass of a powder divided by its apparent volume

Very useful explanation thanks Sirs,

The bulk density of a material is the ratio of the mass to the volume (including the interparticulate void volume) of an untapped powder sample. This is obtained by placing samples naturally in a container of known volume and taking the mass of the samples that fully filled the container (Note: without any tapping but only by natural packing and piling of the samples on each other). The bulk density is the ratio of the mass to the volume of container. The volume in this case includes the inter granular spaces i.e., the porosity factor.

The tapped density is obtained by mechanically tapping a graduated cylinder containing the sample until little further volume change is observed. in this case, the container is tapped to accommodate more samples and the process above is repeated.

True Density is the measure of the mass per unit TRUE volume of the grains which does not include pore spaces in between the samples.

The bulk density will be lower than the "true" density of the material, since the bulk density averages in void spaces (filled with, presumably, a low-density material like air) between the individual particles making up the material.

The bulk density of a material is the ratio of the mass to the volume (including the interparticulate void volume) of an untapped powder sample.

The tapped density is obtained by mechanically tapping a graduated cylinder containing the sample until little further volume change is observed.