IKA C 2000 control - Manual (Page 23)

IKA  -WERKE C 2000 basic / control Ver. 04 08.07
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Almost all substances to be analyzed contain sulfur and nitrogen. Under the condi-
tions that prevail during calorimetric measurements, sulfur and nitrogen undergo
combustion and form SO
2
, SO
3
and NO
x
. Sulfuric and nitric acid arise in combination
with the water resulting from combustion and humidity. Heat of solution is also gen-
erated. To obtain the standard gross calorific value, the effect of the heat of solution
on the gross calorific value is corrected.
To obtain a defined final status and to record all acids quantitatively, about 5 ml of
distilled water or another suitable solution is placed in the decomposition vessel.
With this absorption fluid and the combustion water, the combustion gasses form
acids. After the combustion, the decomposition vessel is thoroughly washed with
distilled water so as to collect the condensate that has settled on the inner wall of
the vessel as well. The solution obtained in this manner can now be examined with
a suitable peripheral detection device for aqueous decomposition into the respective
acid content.
For more information on this subject, please contact IKA  or your nearest authorized
dealer.
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To correctly determine the gross calorific value, it is of fundamental 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.
Normally, solid substances can be burned directly in powder form. Rapidly burning
substances (for example benzoic acid) must not undergo combustion in loose form.
These substances tend to squirt, and it would therefore not be possible to ensure
complete combustion. In addition, it is possible the decomposition vessel could be
damaged. Such substances are pressed into tablets before combustion with a spe-
cial press (C 21 pelleting press, see accessories).
Substances with low flammability (substances with a high content of mineral matter
and low-calorific substances) will often undergo complete combustion only with the
aid of combustion capsules or combustion bags. It is also possible to use liquid
combustion aids such as paraffin oil, for example.
Most liquid substances can be weighed directly into the crucible. Highly volatile sub-
stances are placed in combustion capsules (gelatin capsules or acetobutyrate cap-
sules, see accessories) and undergo combustion together with the capsules.
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.
Substances rich in halogen may cause corrosion to appear on the decomposition
vessel. The C 5012 decomposition vessel should be used for these applications.
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