Parr Instrument 6300 - Manual (Page 73)

C
ALCULATIONS
6300
B
w w w . p a r r i n s t . c o m 73
the thermochemical corrections. The 6300 Calorimeter
has been programmed to permit the user to use standard
solutions and units which are most convenient, since
the microprocessor can easily apply any conversion
factors required.
F
USE
C
ORRECTION
The fuse correction applied by the calorimeter is
calculated as:
e
3
= (fuse value) (fuse multiplier from
calculation factors page)
= (entered value)(fuse multiplier from
thermochemicals page)
“Fuse Value” is the number entered by the user and the
value which appears in the test report.
Note:
Calculation Factors,- Fuse Multiplier is normally set to
1.0 so the entered value is in calories.
Users may find it convenient to enter a fixed value for
the fuse correction and avoid the need to determine this
correction for each test.
Fixed fuse corrections can be entered when
Thermochemical Corrections, is set to ON. By default a
fixed fuse correction of 50 calories is applied to all tests.
Total errors of more than 5 calories will seldom occur
when using a fixed fuse correction and the ignition
thread supplied by Parr.
A
CID AND
S
ULFUR
C
ORRECTIONS
Total acid
•
is the amount of base required to titrate
the bomb washings (milliliters).
Nitric acid
•
is that portion of the total acid in the
bomb washings that result when the nitrogen in the
air that is trapped in the bomb is burned at high
pressure. Since this nitric acid does not result from
the sample, and the combustion conditions are
reasonably constant from test to test, the amount of
nitric acid formed is also constant.
Acid multiplier
•
is multiplied by the user
entered acid value to arrive at the number of
milliequivalents of acid. This value is normally the
concentration (normality) of the base in equivalents
per liter (N).
Percent sulfur
•
is the concentration of sulfur in the
sample (weight %).
Molecular weight of sulfur
•
is 32.06.
Equivalent weight of sulfur in H
•
2
SO
4
is 16.03 (one
half of the molecular weight).
Heat of formation of nitric acid
•
is 14.1 calories/
milliequivalent.
Heat of formation of sulfuric acid
•
(from SO
2
) is
36.1 calories/milliequivalent.
Sample mass
•
is the mass of sample burned in the
bomb (grams).
Sulfur multiplier
•
is multiplied by the product of the
user entered sulfur value and the sample mass to
arrive at the number of milliequivalents of sulfuric
acid in the bomb washings.
Sulfur Correction:
e2 = (percent sulfur)(sample mass)(sulfur multiplier)
(heat of formation of H2SO4).
Acid Correction:
In the 6300 there are a number of settings for the acid
correction.
e1 is the nitric acid portion of the correction.
Fixed HNO3: The Acid Correction is a fixed value set
by the operator.
The calculation is:
e1 = (nitric acid value)(acid multiplier)(heat of
formation of nitric acid)
For an 1138 bomb the default nitric acid value is 8 and
acid multiplier is .0709. The heat of formation of nitric
acid is 14.1 calories/milliequivalent so the calculation
is:
e1 = (8)(.0709)(14.1) or e1 = 7.9975 calories (rounds to 8)
When the Acid Correction is set to Fixed HNO3 the
value is considered a final value and the operator is not
prompted for an acid value when reporting the results.
Entered HNO3: The Acid Correction is entered by the
operator when reporting the results.
The calculation is the same as Fixed HNO3 above. The
value listed on the Acid Correction button is used for
preliminary calculations. When finalizing the report
the operator will be prompted for the acid value.