Parr Instrument 1356 - Manual (Page 6)

6
Press the START key . The calorimeter will prompt for a Cal ID. The calorimeter
will then prompt for sample identification number by displaying Sample ID on
the display. Enter the correct sample ID by using any number, up to six digits, to
identify the sample. The calorimeter will check its memory and will not accept
duplicate sample ID numbers. Enter this value. The system will now prompt for a
sample weight, enter the sample wieght.
6. The calorimeter will now take over and conduct the test. During the time it is
establishing the initial equilibrium, it will display the PRE-PERIOD. Once the
bomb has been fired, the POSTPERIOD will be displayed. 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.
7. At the conclusion of the test, the calorimeter will signal the user and print the
results.
8. Open the cover, detach the lead wires from the bomb and remove the bucket with
the bomb. 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 place it on the support stand.
Examine the interior of the bomb and fuel capsule for soot or other evidence of
incomplete combustion. If such evidence is found, the test will have to be
discarded.
9. Wash all interior surfaces of the bomb with a jet of distilled water and collect the
washings in a beaker.
10. Use Fixed Corrections or remove all unburned pieces of fuse wire from the bomb
electrodes; straighten them and measure their combined length in centimeters.
Subtract this length from the initial length of 10 centimeters and multiply this
burned length by 2.3 calories per cm (for Parr 45C10 Fuse Wire) to obtain the
fuse correction. The scale on the fuse wire card can be used to obtain this value
directly. If fixed corrections are used no entry is required.
11. Use fixed corrections or 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.
Enter the titer value for the acid correction. If fixed acid corrections has been
programmed, no entry is required.
12 Analyze the bomb washings to determine the sulfur content of the sample if it
exceeds 0.1 percent. Methods for determining sulfur are discussed in Operating
Instructions No. 207M.
13. Turn off the calorimeter at the power switch.