Operation
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Stainless steel capsules (43AS) are furnished with
each calorimeter. The stainless steel capsules will
acquire a dull gray finish after repeated use in an
oxygen combustion vessel due to the formation of a
hard, protective oxide film. This dull finish not only
protects the capsule, but it also promotes combus-
tion and makes it easier to burn the last traces of
the sample. New capsules are heated in a muffle
furnace at 500 ºC for 24 h to develop this protective
coating uniformly on all surfaces. This treatment
should be repeated after a capsule has been pol-
ished with an abrasive to remove any ash or other
surface deposits. Heating in a muffle furnace is also
a good way to destroy any traces of carbon or com-
bustible matter which might remain in the capsule
from a previous test. Capsules should be monitored
for wear. Do not use the capsule if the wall or base
thickness is less than 0.7 mm (0.025”).
Note: After heating, place the capsules in a
clean container and handle them only with for-
ceps when they are removed to be weighed on
an analytical balance.
When combusting samples that contain metal
particles such as aluminum or magnesium, the
non-metallic 43A3 Fused Silica/Quartz Capsule is
required.
CAUTION! Do not test samples con-
taining metal using the 43AS Stainless
Steel sample cups. Igniting samples
with metal components could ignite the
stainless steel sample cup and interior
components of the vessel and damage the
vessel. Samples containing metal can be
tested with the 43A3 Fused Silica/Quartz
crucibles.
When superior corrosion resistance is needed, the
43A5 Platinum Rhodium Capsule or 43A3 Fused
Silica/Quartz is required.
Test Process
Loading the sample
Prepare and weigh the sample to 0.0001 g. Gently
tap capsules that contain powdered samples to
compact the material. (Pellets are easier to handle
than loose samples and they burn slower in the
oxygen combustion vessel, thereby reducing the
chances for incomplete combustion).
Carefully place the capsule into the capsule holder.
A cotton thread (845DD2) is used as an auxiliary
fuse to ignite the sample. Remove any moisture
from the heating wire prior to attaching the cotton
thread.
10 cm (4”) of thread is recommended for this aux-
iliary thread which is looped over the heating wire,
doubled on itself, twisted to form a single strand
and fed into the sample cup to lay on the sample.
When contact is made through the heating wire,
the thread will ignite, drop into the sample cup
and ignite the sample. One spool of thread, part
number 845DD, is ~515 m. Part number 845DD2
contains approximately 1000 pieces of thread pre-
cut to 10 cm (4”).
Closing the Oxygen Combustion Vessel
Care must be taken not to disturb the sample when
moving the vessel head from the support stand to
the vessel cylinder in the calorimeter. Check the
sealing ring to be sure that it is in good condition
and moisten it with a bit of water so that it will
slide freely into the cylinder.
Notice that the vessel head grounding lug extends
beyond the outside diameter of the vessel head.
A slot for this lug is cut into the top of the calo-
rimeter bucket which holds the vessel cylinder.
Position this lug approximately 20 degrees to the
operators right and slide the head into the cylinder
and push it down as far as it will go. Now rotate
the vessel head 20 degrees to the left until the lug
contacts the left edge of the cut out and is pointed
to the front of the calorimeter.
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