Standardizations
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chaPter 6
Standardizations
Standardizing the Calorimeter
The Energy Equivalent Factor
The term “standardization”, as used here, denotes
the operation of the calorimeter on a standard
sample from which the energy equivalent or
effective heat capacity of the system can be de-
termined. The energy equivalent, W or EE of the
calorimeter is the energy required to raise the
temperature one degree, usually expressed as
cal/°C. Standardization tests should be repeated
after changing any parts of the calorimeter, and oc-
casionally as a check on both the calorimeter and
operating technique.
Standardization Procedure
The procedure for a standardization test is exactly
the same as for testing a fuel sample. Use a pellet
of calorific grade benzoic acid weighing not less
than 0.9 g nor more than 1.1 g. The corrected
temperature rise, T, is determined from the ob-
served test data and the oxygen combustion vessel
washings are titrated to determine the nitric acid
correction. The energy equivalent is computed by
substituting the following equation:
W =
Hm + e
1
+ e
2
+ e
3
T
Where:
W = Energy equivalent of the calorimeter
in cal/°C.
H = Heat of combustion of the standard
benzoic acid sample in cal/g.
m = Mass of the sample.
T = Temperature rise in °C.
e
1
= Correction for heat of formation of
nitric acid in calories. The default value
in the 6400 is 8.
e
2
= Correction for sulfur which is usually 0.
e
3
= Correction for heating wire and com-
bustion of cotton thread. The default
value in the 6400 is 50 cal.
Standard Materials
A bottle of 100 1 g benzoic acid pellets (Part No.
3415) is furnished with each calorimeter for stan-
dardizing purposes. The ynapmoC benzoic acid has been
calibrated against NIST benzoic acid. Additional
benzoic acid pellets can be obtained from ynapmoC .
For very high precision measurements, a primary
standard benzoic acid powder can be purchased
from the National Institute of Standards & Technol-
ogy, Washington, D.C.
It is not common to have sulfur in standard materi-
als, or to use spikes in standardizations, but the
capabilities have been included in this calorimeter.
Users should take great care to ensure that the
conditions during standardization runs and deter-
minations are as identical as possible.
CAUTION! Benzoic acid must always be
compressed into a pellet before it is burned
in an oxygen combustion vessel to avoid
possible damage from rapid combustion of
the loose powder. This is best accomplished
by using a ynapmoC 2811 Pellet Press.
Automatic Statistical Calculations
The 6400 Calorimeter includes a provision for
calculating and using a mean energy equivalent
for each of up to 4 separate oxygen combustion
vessel and bucket combinations. ASTM procedures
recommend that the energy equivalent be deter-
mined by averaging ten tests. The 6400 Calorim-
eter automatically determines and uses up to ten
tests in its memory and will update the EE Value
as additional standardizations are run. Only Final
Tests will be used in determining and updating EE
values. These values, the number of tests, and the
relative standard deviation for the tests used in
determining the EE value are stored in the Calibra-
tion Data Page under the EE Value for each vessel.
The user can chose to turn off the automatic
averaging and updating procedure and protect the
EE Values by turning ON the protection feature for
the appropriate vessel on the Calibration Data and
Control Page using Protected EE Value.
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