Gas (Air) Permeametry option in the HumiPyc gas (helium) pycnometers
Using the provided software and selecting a pressure interval, the user can obtain time and calculate other parameters using Carman-Kozeny equation. This air
permeameter can be a viable option to determining fineness of many powders, like hydraulic cement, for which the ASTM C204-07 method is used. As it is
common practice in air permeametry, standard reference material (NIST No. 114q in the case of hydraulic cement) of known surface area can be used for relative
determinations of specific surface area.
Experimental data of pressure versus time for cement sample
Advantages:
- Can measure specific surface area and true density of the packed bed in the same run
- No need to use mercury, manometric liquids, or glassware
- Yields complete data of pressure versus time for further studies
- Fully automated, software support for calculations
- Use of other gases then air
- Easy to implement different sizes and shapes of packed beds cells
- Possible use of vacuum for diffusion methods
- Possible implementation of constant flow permeameter
- Low cost compared to standalone automated air permeameters
Click to enlarge
The basic premise of permeametry is that measurements of  resistance to a gas flow  through porous media can yield the
method-specific surface area.

Using a specially designed cell for holding a packed bed of powder and ancillary hardware, the HumiPyc Gas (helium)
pycnometers can be utilized as an automatic gas (air) permeameter. The main advantage of such approach is that  true density,
porosity, and the specific surface area can be obtained using the same instrument and automatically. Such quantities can be
obtained for different gases, and in case of the HumiPyc Model 1, at a range of temperatures.

In the simplest implementation, functionality similar to Blaine apparatus can be materialized. Pressurizing  to a programmable
pressure value of the pycnometer fixed volume and opening the auxiliary valve,  the pressure values are recorded versus time.
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