Heat Capacity

The following information applies to the : CAL3K-AP , CAL3K-A , CAL3K-U, CAL3K-F.

The Heat capacity is a measurement which describes the amount of energy (heat) needed to raise the vessel temperature by 1 degree.

The exact heat capacity is calculated by the CAL3K every 6 seconds after the Start record (parameter) during a calibration and then saved to the vessel as a ‘Bomb Factor’. This factor is then used (and averaged with up to 10 others) during a sample determination to calculate the calorific value (CV).

The following is an approximation of the heat capacity:

0.5000g of Benzoic Acid (BA) releases 0.5g*26.454Kj/g = 13.227Kj

This results in a 13.09603C temperature Rise.

Therefore the heat capacity is 13.227Kj / 13.09604C = 1.010 Kj/C

Of course I made the temperature rise up! The actual heat capacity varies with time (every 6 seconds) and with each vessel. But it is safe to say that the heat capacity is very close to ~1.0.

During a determination (without frills) the following happens:

Let’s say we burn 0.6g of Benzoic Acid: From the above data we calculate the temperature Rise:

Rise = 13.09603 / 0.5 * 0.6 = 15.71524°C
The CAL3K calculates:
CV = Rise * Heat capacity / mass
= C * KJ/C / g
= 15.71524 * 1.010 / 0.6
= 26.4554Kj/g


The CAL3K system uses the SMART CAL3K bomb vessel. The bomb vessel is the first of its kind, and is the heart of the CAL3K system. Its sophisticated design allows the temperature to be measured to six decimal places in degrees Celsius. The vessel is an intelligent (SMART) vessel with a microprocessor built into its base.

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The Heat capacity of the vessel is approx. 0.001C/J or 1KJ/C. In practical terms is means that 0.5g Benzoic Acid results in approx. 13.2°C temperature rise.

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This is a conventional term, but related to the heat capacity. The Bomb factor is approx. 1 KJ/C. In practice this means that 0.5g Benzoic Acid results in ~13.2°C rise. Then the calorific value CV=13.2C / 0.5g x 1KJ/C = 25.4KJ/g.

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