Parr Instrument 1356 - Manual (Page 9)

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Press the Clear key, enter the new value on the keyboard and press the Enter key. This
sequence is canceled by pressing the RESET key. Press the Escape key, when one is
done editing. If more than 1 sample is to be edited, the screen will display the next
sample’s information.
J. Standardizing the Calorimeter
The calorimeter will calculate the average EE value from standardization tests that have
been made.
K. Calculating the Heat of Combustion
While the Model 1356 Calorimeter will automatically make all of the calculations
necessary to produce a gross heat of combustion for the sample. It is important that the
user understand these calculations to ensure that the instrument is set up so that the
calculations match the procedures used and that the units are consistent throughout the
entire procedure and calculations.
L. General Calculations
Basically, the calculation of the gross heat of combustion is done using the following
equation:
Where:
Hc =Gross heat of combustion.
T =Observed temperature rise.
EE =Energy equivalent of the calorimeter being used.
e1 =Heat produced by burning the nitrogen entrapped in the bomb to form nitric acid.
e2 =Extra heat produced due to burning sulfur to sulfur trioxide and forming sulfuric
acid instead of sulfur dioxide.
e3 =Heat produced by the burning fuse wire.
m =Mass of the sample.
For convenience and by tradition, these calculations are made in calories, grams,
and degrees Celsius, and then converted to other units if required. The other units desired
are set on Menu page 2, line 2.
Temperature rise. The 1356 Calorimeter produces a corrected temperature rise reading
automatically. Corrections for heat leaks are applied automatically. Similarly, the method
for extrapolating the end point of the test is discussed in the dynamic method description.
Energy equivalent. The energy equivalent (represented by W in the above formula, or
abbreviated as EE) is determined by standardizing the calorimeter as described in the
Standardization Section of the calorimeter manual. It is an expression of the amount of
energy required to raise the temperature of the calorimeter one degree. It is commonly
expressed in calories per degree Celsius. Since it is directly related to the mass of the
calorimeter, it will change whenever any of the components of the calorimeter (i.e. the
bomb, bucket, or amount of water) is changed.
M. Thermochemical Corrections
Nitric acid correction. In the high pressure oxygen environment within the oxygen bomb,