Parr Instrument 6100 - Manual (Page 52)

B
Calculations
P a r r I n s t r u m e n t C o m p a n y 50
ISO Calculations
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 6100 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
(V
2
) followed by filtering, and a second titration
using 0.1N HCL(V
1
) 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, V
1
and V
2
, to be entered into the
controller directly for the calculation of the total acid
correction. V
1
should be entered at the prompt for
acid and V
2
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 For-
mation 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:
V
1
(Acid Multiplier)(Heat of Formation of Nitric
Acid)
V
2
(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.
Spiking Samples
There are times when a sample will not completely
burn. This can be due to a number of things includ-
ing low heat of combustion and high water content.
In cases such as these a material is added to the
sample in order to help it completely combust. This
is known as a combustion aid or spike.
The 6100 Calorimeter can automatically compensate
for the addition of spiking materials to these sam-
ples. The calculations are modified in these cases as
follows:
Hc =
WT-e
1
- e
2
- e
3
- (Hcs)(M
s
)
m
Where:
Hcs = The spiking material (cal/g)
M
s
= Mass of spiking material
This factor is added to the calculations when Spike
Controls, Use Spiking is set to ON.
There are generally two substances that Parr recom-
mends using as a spike, benzoic acid and mineral
(white) oil.
Benzoic acid is good as a spike for the same reasons
that it is good as a standard. It is homogeneous and
has an established heat of combustion.
Mineral oil is good for several reasons. It is inex-
pensive, it has a high heat of combustion, and it is
a liquid. As a liquid it can permeate the sample and
help it to burn.
To use spiking go to the Main Menu and then to
Operating Controls. Press Spiking Correction to get
to the Spike Controls sub-menu. Once on the Spike
Controls sub-menu change Use Spiking to ON. The
heat of combustion of the spike must be entered
in cal/g. The default value of 6318.4 is the value for
benzoic acid.
If mineral oil is to be used for your spike then the
heat of combustion of the mineral oil must be
determined. Run 10 tests of the mineral oil in deter-
mination mode with the reporting units set to cal/g.
The sample size should be approximately .6 grams.
Average the 10 results to get the heat of combustion
of the mineral oil.
Note: When using a spike it is very impor-
tant to be aware of the total energy being re-
leased by the sample and the spike. Do NOT
exceed 8000 calories total energy released.