16
To correctly determine the gross calorific value, it is of fundamen-
tal importance that the sample undergoes complete combustion.
After each experiment, the crucible and all solid residues must be
examined for any signs that combustion was not complete.
In case of using substances tending to squirt it is not possible to
ensure complete combustion.
Substances with low flammability (substances with a high
content of mineral matterand low-calorific substances) will often
Complete combustion
undergo complete combustion only with the aid of combustion
capsules or combustion bags (C 10/ C 12 see “Accessories“). It is
also possible to use liquid combustion aids such as paran oil.
The combustion aids as well (for example the cotton thread) must
undergo complete combustion. If unburned residues are left over,
the experiment must be repeated.
To ensure precise, reproducible results of the measurement, the
calorimeter system is calibrated after it is initially placed in service,
after service jobs, after parts are replaced and at specific time inter-
vals. During calibration, the heat capacity of the calorimeter system
is redetermined.
Regular calibration is absolutely essential to obtain accurate
measurements!
For this purpose, a specific quantity of a reference substance
undergoes combustion in the
IKA
®
C 1 under the conditions of
the experiment. Since the gross calorific value of the reference
substance is known, it is possible after combustion has occurred
Calibration
to calculate the heat capacity based on the increase in temperature
of the calorimeter system. The reference substance for calorimetry
on an international level is benzoic acid of the National Bureau of
Standards (NBS Standard Sample 39 J) with a guaranteed gross
calorific value.
For more detailed information on calibration please see the relevant
standards.
If the
IKA
®
C 1 is operated with several different decomposition
vessels, you will need to determine the heat capacity of the system
for each decomposition vessel. The parts of each decomposition
vessel must then not be swapped with parts from other vessels.
Ensure that calibration is carried out under the same conditions as
the subsequent tests. If substances are used in the decomposition
vessel in combustion tests (e.g. distilled water or solutions), you
must use exactly the same amount of this substance for calibration.
Notes on calibration
For determination of calorific values the increase in temperature
must be about as great as for the calibration (± 30%). 1g benzoic
acid =˜ 6K. The optimum sample quantity must de determined by
several trials where necessary.
• Under the conditions that prevail during calorimetric mea-
surements, sulfur and nitrogen un-dergo combustion and form
SO
2
, SO
3
and NO
X
. Sulfuric and nitric acid arise in combinati-
on with the water resulting form combustion. Heat of solution
is also generated. This heat of solution is taken into conside-
ration in calculating the gross calorific value. In order to quanti-
tatively record and determine all acids that have been formed,
about 5 ml of distilled water or another suitable substance can
be added to the decomposition vessel before the experiment.
The calibration of the system must have been performed in
accordance with the instructions!
Remove after measuring the complete inner vessel. Turn the inner
container upside down, loosen gently the internal container bot-
tom. Rinse thoroughly with distilled water, the inner area of the
inner container. The rinsing water and the solution formed from
the water that was added are combined and the acid content of
the combined solution is examined. If the sulfur content of the
combustion aid and the nitric acid correction are known, the water
does not need to be analyzed.
These correction values can not be entered in C 1. For this, use the
IKA
®
calorimeter software CalWin
®
.
To increase the service life of parts to wear and tear (O rings,
seals etc.) we recommend to work with water added to the
experiment as a matter of general principle.
Halogen rich substances can cause corrosion on the inner con-
tainer.
These substances must not be burned in C 1 with the
standard inner vessel.
In halogen-rich substances of special halogen-resistant
inner vessel C 1.12 must be used.
Handle
h
h
h
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