Determining the Free Gas Volume

DOE-STD-3013-2004

Table B-2

Container Volumes

Free

Mass in

Material

Component

Interior

Volume in

grams

Volume in

liters

Convenience Can

1.839

1580

vcc = 0.198

Vc = 1.839

Inner Can

2.266

1600

vi = 0.200

2.068

Outer Can

Vo = 2.602

4026

2.204

B.3.2

Determining the Free Gas Volume

B.3.2.1

Density Method

A straightforward method to determine the free gas volume of the container is to first estimate

the volume occupied by the contained material as the mass of material divided by the material

density:

Vm = m/ρ,

[26]

The free gas volume is then obtained by subtracting the volume defined in Equation [26] from

the container unoccupied volume given in Equation [5a]. The difficulty with this approach is that

the density is most likely unknown. To facilitate discussion, definitions of different types of

density are provided:

Bulk density: This is the mass of material divided by the volume that it occupies. In the case

of a powder, it is assumed to be the density achieved after the powder has been poured into

the container.

Crystal density: This is the density of a crystal of the material in question.

Particle density: For purposes of this discussion, the particle density is the density of the

individual particles of powder. This will be greater than the bulk density because the

interstitial gas spaces (see Figure B.1) are not included in the volume. It will be less than

the crystal density because the particles will have some porosity that cannot be accessed by

the gas. The particle density can be measured with a gas pycnometer.

The correct density to use in Equation [26] is the particle density. However, it is extremely

unlikely that the particle density of material in every container will be measured. Accordingly,