Parr Instrument 6300 - Manual (Page 36)

5
O
PERATING
I
NSTRUCTIONS
P a r r I n s t r u m e n t C o m p a n y 36
F
OODSTUFFS AND
C
ELLULOSIC
M
ATERIALS
Fibrous and fluffy materials generally require one of
three modes of controlling the burn rate. Fibrous mate-
rials do not pelletize readily and generally require either
moisture content or combustion aid such as mineral oil
to retard the burn rate and avoid development of high
pressures.
Partial drying may be necessary if the moisture content
is too high to obtain ignition, but if the sample is heat
sensitive and cannot be dried, a water soluble combus-
tion aid such as ethylene glycol can be added to pro-
mote ignition.
C
OARSE
S
AMPLES
In most cases it may be necessary to burn coarse sam-
ples without size reduction since grinding or drying
may introduce unwanted changes. There is no objection
to this if the coarse sample will ignite and burn com-
pletely. Whole wheat grains and coarse charcoal chunks
are typical of materials which will burn satisfactorily
without grinding and without additives or a special
procedure.
C
ORROSIVE
S
AMPLES
1138 Oxygen Combustion Bomb
The 1138 bomb is made from alloy 20; a special nio-
bium stabilized stainless steel selected for its resistance
to the mixed nitric and sulfuric acids produced during
the combustion process.
The 1138CL is made from the halogen resistant Hastel-
loy G30™. Hastelloy G30™ is an alloy rich in cobalt
and molybdenum and is able to resist the corrosive
effects of free chlorine and halogen acids produced
when burning samples with significant chlorine con-
tent. While no alloy will completely resist the corrosive
atmospheres produced when burning samples contain-
ing halogen compounds; users who intend to test these
materials are urged to select the 1138CL Bomb.
These bombs are 250 mL in volume and are rated to a
maximum working pressure of 2000 psi. The bombs
are hydrostatically tested to 3000 psi and the sample
range is ~1g or 5000 – 8000 calories.
1136 Oxygen Combustion Bomb
The 1136 bomb has been used extensively in our model
1281 calorimeter for the past ten years. It will safely
burn samples liberating up to a maximum 8000 calories
per charge using oxygen charging pressures up to 40
atm.
The 1136 bomb, like the 1138 bomb, is made of alloy 20
and is also available in Hastelloy G30
TM as part number
1136CL. These bombs are 340 mL in volume and are
rated to a maximum working pressure of 2000 psi. Like
the 1138, the bombs are hydrostatically tested to 3000
psi and the sample range is ~1g or 5000 – 8000 calories.
E
XPLOSIVES AND
H
IGH
E
NERGY
F
UELS
Materials which release large volumes of gas which det-
onate with explosive force or burn with unusually high
energy levels, should not be tested in this calorimeter.
Rather, they should be tested in a model 6100 or 6200
Calorimeter which can be equipped with an 1104 High
Pressure Oxygen Bomb designed specifically for these
types of samples.
V
OLATILE
S
AMPLE
H
OLDERS
Volatile samples can be handled in a Parr 43A6 Plati-
num Capsule with a spun rim, or in a Parr 43AS Al-
loy Capsule which has a sturdy wall with a flat top
rim. These holders can be sealed with a disc of plastic
adhesive tape prepared by stretching tape across the top
of the cup and trimming the excess with a sharp knife.
The seal obtained after pressing this disc firmly against
the rim of the cup with a flat blade will be adequate for
most volatile samples. The tape used for this purpose
should be free of chlorine and as low in sulfur as pos-
sible. Borden Mystic Tape, No. M-169-C or 3M Trans-
parent Tape, No. 610, are recommended for this pur-
pose. The 3M Transparent Tape can be ordered through
Parr, Part No. 517A.
The weight of the tape disc must be determined sepa-
rately and a correction applied for any elements in the
tape which might interfere with the determination. The
approximate Heat of Combustion of the tape is 6300
cal/g. An actual amount should be determined by run-
ning a blank test with tape alone using a sample weigh-
ing 1.0 gram. The compensation for heat of tape may
be done through the spike option; see Spike Controls,
Line 2 - Heat of Combustion of Spike.