Air Pycnometer — Langer Method

The vacuum air pycnometer is designed to determine the volume and density of solid materials such as soil samples. It applies wherever specific-gravity calculations matter: soil research (porosity determination), pharmaceutical powder/granulate investigation, road construction (tar measurement), brick manufacturing (clay analysis), and the food industry (seed and coffee-bean volumetry). The instrument is particularly useful for measuring the volume of irregularly shaped objects, and can also measure non-porous materials.

Working Principle

A low pressure (underpressure) is created in the vacuum bell holding the object to be measured. Depending on the gas volume in the bell, more or less air is drawn in. The amount of air present is independent of the volume occupied by the object being measured. Once the low pressure has stabilized, the object's volume can be read from the calibrated scale — enabling simple calibrations, and it can also be used without soil sample rings when needed.

Applications

• Determining the porosity of soil samples (100 cc soil sample rings recommended when taking undisturbed samples)
• Powder and granulate research in the pharmaceutical industry
• Measuring the pore volume of asphalt (road construction) or clay and bricks (brick manufacturing)
• Volume determination of seeds, coffee beans, pulses etc. in the food industry
• Laboratory soil density measurements

Limitation: temperature variation affects the measurement (can be avoided with climate control in the laboratory).