Parr Instrument 6200 - Manual (Page 24)

5
Operating Instructions
P a r r I n s t r u m e n t C o m p a n y 22
To speed and simplify the bucket filling process,
and to conserve water and energy, Parr offers
a closed circuit Water Handling System (No.
6510). This provides a water supply, cooled
to the starting temperature and held in an
automatic pipet ready for delivery in the exact
amount needed to fill the bucket. Instructions
for this automatic system are given in Operating
Instruction No. 454M.
4. Set the bucket in the calorimeter. Attach the
lifting handle (421A) to the two holes in the
side of the screw cap and partially lower the
bomb into the water. Handle the bomb carefully
during this operation so that the sample will not
be disturbed. Push the two ignition lead wires
into the terminal sockets on the bomb head.
Orient the wires away from the stirrer shaft
so they do not become tangled in the stirring
mechanism. Lower the bomb completely into
water with its feet spanning the circular boss
in the bottom of the bucket. Remove the lifting
handle and shake any drops of water back into
the bucket and check for gas bubbles.
Note: If bubbles continue to rise from the
bomb after the air in the screw cap has
escaped the test must be stopped and the
bomb not fired until the leak has been cor-
rected.
5. Close the calorimeter cover. This lowers the
stirrer and thermistor probe into the bucket.
Make sure that the bucket thermistor does
not touch the bucket or 1108P when the lid is
lowered.
6. Select determination or standardization as
appropriate on the Calorimeter Operation menu
by toggling the OPERATING MODE key. After
pressing the START key, the calorimeter will
now prompt the operator for Bomb ID number,
sample ID number, sample weight and spike
weight in accordance with the instructions set
into the operating controls page.
7. The calorimeter will now take over and conduct
the test. During the time it is establishing the
initial equilibrium, it will display PREPERIOD on
the status bar. Just before it fires the bomb, it
will sound a series of short beeps to warn the
user to move away from the calorimeter. Once
the bomb has been fired, the status bar will
display POSTPERIOD. The calorimeter will check
to make certain that a temperature rise occurs
and will then look for the final equilibrium
conditions to be met. If it fails to meet either the
initial or final equilibrium conditions, or if it fails
to detect a temperature rise within the allotted
time, the calorimeter will terminate the test and
advise the user of the error.
8. At the conclusion of the test, the calorimeter will
signal the user.
9. Open the cover and remove the bomb and
bucket. Remove the bomb from the bucket
and open the knurled valve knob on the bomb
head to release the residual gas pressure before
attempting to remove the cap. This release
should proceed slowly over a period of not less
than one minute to avoid entrainment losses.
After all pressure has been released, unscrew
the cap, lift the head out of the cylinder and
examine the interior of the bomb for soot or
other evidence of incomplete combustion. If
such evidence is found, the test will have to be
discarded. Otherwise, wash all interior surfaces
of the bomb, including the head, with a jet of
distilled water and collect the washings in a
beaker.
10. Titrate the bomb washings with a standard
sodium carbonate solution using methyl orange,
red or purple indicator. A 0.0709N sodium
carbonate solution is recommended for this
titration to simplify the calculation. This is
prepared by dissolving 3.76 grams of Na
2
CO
3
in
the water and diluting to one liter. NaOH or KOH
solutions of the same normality may be used.
11. Analyze the bomb washings to determine the
sulfur content of the sample if it exceeds 0.1%.
Methods for determining sulfur are discussed in
Operating Instructions No. 207M.
12. At the end of the testing period, turn OFF the
calorimeter at the power switch.