Parr Instrument 6725 - Manual (Page 24)

6725
Semi-micro Calorimeter Instruction Manual
4-4
Manual Test Sequencing
Some users may wish to construct their own thermogram and apply the classic graphical
corrections developed by Dickenson and others. In this case the actual temperatures
can be logged to the thermometer memory of the thermometer and then analyzed at the
end of the test. These logged temperatures can be recalled to display on the
thermometer, printed on an attached printer or transferred to a computer using either the
Ethernet Connection or a Compact Flash Card. The Ethernet Connection can also be
used to transfer temperatures to a computer for plotting and analysis in real time.
First, select the appropriate jacket temperature source as described previously. Then
prepare the sample and charge the oxygen bomb as described in Operating Instructions
No. 492M. Each bomb and bucket combination will have to be standardized separately
and the proper energy equivalent for each set must be used when calculating the heat of
combustion.
The calorimeter bucket consists of the Dewar flask with its attached spacer ring. The
bucket may be filled either gravimetrically or volumetrically, as long as it can be done
with a precision of 0.03% or better. The bucket should be filled with water to the nearest
multiple of 50 milliliters (grams) which just covers the small hole (gas inlet/outlet) on the
bomb head inlet valve. Due to differences in construction and manufacturing tolerance
on both the Dewar flask and the bomb hanger, the amount of water will be 400 or 450
mL (grams). Distilled water is preferred, but demineralized or tap water containing less
than 250 ppm of dissolved solids will suffice. The temperature of the water should be
within ± 1 °C of room temperature and be consistent from test to test. After filling the
Dewar, set it in the stainless steel air can and gently push the spacer ring down as far as
it will go.
Attach one of the ignition wires to the socket in the center terminal on the bomb head
and push it down as far as it will go. Attach the second wire to the socket provided on
the bomb hanger. Set the bomb in the loop of the A67C2 bomb support and carefully
lower it into the Dewar to hang from the top rim of the flask. Position the bomb as shown
in Figure 2 so that the stirrer can operate freely without striking the bomb.