Parr Instrument 6725 - Manual (Page 50)

6725
Semi-micro Calorimeter Instruction Manual
6-2
In practice, the amount of heat produced by the combustion of Nitrogen in the 22 mL and
1109A bomb is negligible and is usually handled by using the Fixed HNO3 Correction for
Nitrogen and setting it to 1.5.
Sulfur Correction
In the oxygen rich atmosphere within the bomb, sulfur in the sample is oxidized to
sulfur trioxide which combines with water vapor to form sulfuric acid. This liberates
additional heat over the normal combustion process which converts sulfur to sulfur
dioxide. The sulfur correction removes this excess heat from the calculation. In
practice, the importance of this correction is directly proportional to the sulfur
content of the sample.
Note:
For ordinary work where benzoic acid is used, for standardizing the
Calorimetric Thermometer, the Fixed Sulfur Correction, for
Standardizations should be ON applying a fixed value of 0.0 to all
standardization tests. Benzoic acid contains no sulfur.
Manual vs. Fixed Corrections
If fixed values for fuse, acid and sulfur are turned OFF on the Thermochemical
Corrections Menu, then the user must manually enter the values at the prompt. Final
reports for each test can be obtained whenever the operator is prepared to enter any
required corrections for fuse, acid and sulfur. When entering corrections, the user can
choose either or two methods. These are:
• Manual
Entry
• Fixed
Corrections
Manual Entry
During the reporting process, the controller will prompt the user to enter the following
values:
• Fuse
Correction Key in the Fuse/Heat Wire Correction and press the ENTER
key. The default setting for this value is to be entered in calories.
• Acid
Correction Key in the Acid Correction and press the ENTER key. The
default setting for this value is to be entered in milliliters of standard alkali required
to titrate total acid or calories.
• Sulfur Correction
Key in the Sulfur Correction and press the ENTER key. The
default setting for this value is to be entered as percent sulfur in the sample.
Note:
If the Spiking Correction is used, a spiking correction must be entered
before obtaining a Final Report. After the last entry has been made, the
Calorimetric Thermometer will automatically produce a Final Report. If
values for these corrections are not available, the operator can use the
SKIP key to bypass any of the corrections, however, a Final Report will
not be printed until an entry is made for fuse, acid and sulfur.
Fixed Corrections
In many cases, fixed values for fuse and acid can be used without introducing a
significant error since the corrections are both relatively small and constant. Fixed sulfur
corrections can also be used whenever a series of samples will be tested with