Parr Instrument 1341 - Manual (Page 7)

1341 Plain Jacket Calorimeter
w w w . p a r r i n s t . c o m 7
11. After the last temperature reading, stop the
motor, remove the belt and lift the cover from
the calorimeter. Wipe the thermistor shaft and
stirrer with a clean cloth and set the cover on
the A37A support stand. Lift the bomb out of the
bucket; remove the ignition leads and wipe the
bomb with a clean towel.
12. Open the knurled knob on the bomb head to
release the 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 for soot
or other evidence of incomplete combustion. If
such evidence is found, the test will have to be
discarded.
13. Wash all interior surfaces of the bomb with a jet
of distilled water and collect the washings in a
beaker.
14. 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 enter this quantity on the data
sheet as the net amount of wire burned. Alter-
natively, the correction in calories is located on
the card of the 45C10 fuse wire.
15. Titrate the bomb washings with a standard so-
dium carbonate solution using methyl orange or
methyl red indicator. A 0.0709N sodium carbon-
ate solution is recommended for this titration to
simplify the calculation. This is prepared by dis-
solving 3.76 grams Na
2
CO
3
in water and diluting
to one liter NaOH or KOH solutions of the same
normality may be used.
16. Analyze the bomb washings to determine the
sulfur content of the sample if it exceeds 0.1 per
cent. Methods for determining sulfur are dis-
cussed in Instruction Manual No. 207M.
Graph displaying typical temperature rise curve
Caution!
Do not have any part of the body in the
pressure relief path.