IKA C 6000 isoperibol Package 2/12 - Manual (Page 23)

23
Corrections
As determined by the
system, during a combustion
experiment, not only is
heat generated from the
combustion of the sample,
but heat also occurs in the
form of extraneous energy.
This may fl uctuate considerably
in proportion to the heat
energy of the fuel sample.
The combustion heat of the cotton threat that ig-
nites the sample and the electrical ignition energy
would result in distorted values of the measure-
ment. This effect is taken into consideration in the
calculation with a correction value.
Substances with low fl ammability or substances
that burn poorly undergo combustion in combina-
tion with combustion aids. The combustion aid is
fi rst weighed and then added to the crucible with
the sample. From the weight of the combustion
aid and its known specifi c gross calorifi c value, it
is then possible to determine the quantity of heat
that is introduced thereby. The result of the expe-
riment must be corrected by this amount of heat.
The C 14 disposable crucible is a combustible
crucible that can be used instead of a traditional
crucible. The disposable crucible undergoes total
combustion with no residue. If a disposable cruci-
ble is used, there is then no need for a cotton th-
read. The crucible is in direct contact and is ignited
by the fi xed ignition wire of the decomposition
vessel.
The sample is weighed directly into the disposable
crucible. In most cases, no additional combustion
aid is necessary because the disposable crucible
itself acts as the combustion aid.
Acid correction
Almost all substances to be analyzed contain sul-
fur and nitrogen. Under the conditions that pre-
vail during calorimetric measurements, sulfur and
nitrogen undergo combustion and form SO
2
, SO
3
and NO
X
. Sulfuric and nitric acid arise in combi-
nation with the water resulting from combustion
and humidity. Heat of solution is also generated.
To obtain the standard gross calorifi c value, the
effect of the heat of solution on the gross calorifi c
value is corrected.
To obtain a defi ned fi nal status and to record all
acids quantitatively, distilled water or another
suitable absorption solution is placed in the de-
composition vessel before the trial according to
the relevant standards. With this absorption fl uid
and the combustion water, the combustion gases
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 ob-
tained 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 con-
tact IKA
® ‚ or your nearest authorized dealer.
Working with the IKA ® C 6000 global standards/isoperibol calorimeter