Bomb Calorimetry Testing
Click image for a close-up view.
Parr Bomb calorimetry is used to measure heats of combustion. This includes conventional fuels, renewable energy sources, explosives, foodstuffs, waste materials, organics, pharmaceuticals, and pyrotechnics.
The Parr bomb is usually calibrated by combustion of a high purity sample of benzoic acid (NIST SRM 39j or equivalent). For high-precision calorimetry, the mass of the benzoic acid used for calibration will be corrected for buoyancy. After a valid calibration, standard enthalpies of formation for pure compounds may be derived from the standard heats of combustion. For high-precision evaluations, combustion data requires correction for a series of factors collectively known as the “Washburn reduction.” Details of these corrections are described in “EXPERIMENTAL THERMOCHEMISTRY Measurement of Heats of Reaction” edited by Frederick D. Rossini , INTERSCIENCE PUBLISHERS INC. NEW YORK, 1956.
The bomb calorimeter is calibrated with SRM 2232 (benzoic acid) certified by the National Institute of Standards and Technology (NIST). For compounds containing elements other than carbon, hydrogen, and oxygen, such as nitrogen, other NIST standards are used.
Parr Bomb in the Combustion Bucket
The bomb is fired in a bucket containing 2 kg distilled water. Heat of combustion is calculated from the change in the water temperature.
Native Anmerican grasses are a source of renewable energy. Bomb calorimetry is used to evaluate the energy content. The graphic shows the typical combustion curve obtained for an American prairie grass.