Parr Instrument 6200 - Manual (Page 65)

66
6200
Calorimeter Operating Instruction Manual
In the ASTM treatment, the
correction for acid formation
assumes that all the acid titrated
is nitric acid. Obviously, if sulfur
is present in the sample, which
in turn produces sulfuric acid, part of the
correction for the sulfuric acid formed is
already included in the ASTM nitric acid
correction (e1). This is adjusted by a
separate computation based upon the sulfur
content of the sample. An additional
correction of 1.37 Kcal must be applied for
each gram of sulfur converted to sulfuric
from sulfur dioxide. This is based upon the
heat of formation of sulfuric acid, from sulfur
dioxide, under bomb conditions, which is -
72.2 Kcal per mole or -36.1 calories per
milliequivalent. But remember, a correction
of 14.1 calories per milliequivalent of sulfuric
acid is already included in the ASTM nitric
acid correction (e1). Therefore the
additional correction which must be applied
for sulfur will be the difference between 36.1
and 14.1 or 22.0 calories per milliequivalent
(44.0 Kcal per mole). For convenience, this
is expressed, in the ASTM e2 formula, as
13.7 calories (44.0/32.06) for each
percentage point of sulfur per gram of
sample.
Both the ISO 1928 and BSI
1016: Part 5 methods for testing
the calorific value of coal and
coke, deal with acid and sulfur corrections in
a manner which is somewhat different than
ASTM procedures. Provision has been
made in the 6200 Controller for dealing with
these different procedures.
The analysis of bomb washings in
these methods call for a titration, first using
0.1N barium hydroxide (V2) followed by
filtering, and a second titration using 0.1N
HCL(V1) after 20 ml of a 0.1N sodium
carbonate has been added to the filtrate.
Table B-1 gives the settings which allows
the results of the two titrations, V1 and V2,
to be entered into the controller directly for
the calculation of the total acid correction.
V1 should be entered at the prompt for acid
and V2 is entered at the prompt for sulfur.
The settings in Table B-1 assume that
the same procedure is carried out for both
standardization and determination.
The offset value is the product of -1, the
Heat of Formation of Nitric Acid, the acid
multiplier, and the 20 ml of 0.1 N sodium
carbonate used in the analysis.
The formula used to get the total
correction in calories is as follows:
V1(Acid Multiplier)(Heat of Formation of
Nitric Acid)V2(Sulfur Multiplier)(Heat of
Formation of Sulfuric Acid)+offset value.
The values for fixed acid and sulfur,
which are used in preliminary reports, will
reflect a sulfur correction of 0, and a nitric
acid correction of 10 calories.
ASTM
Treatment for
Acid and
Sulfur
ISO
Calculations
B-6
APPENDIX B