Guidelines for care & Use of Dry Solvent Stills [Example]

Standard Operating procedure for use of the Bomb Calorimeter in the Physical
Chemistry Teaching Laboratory, written by Jason Weibel, graduate student.
The bomb calorimeter is used in the determination of the enthalpy of combustion of a given
sample. Although the samples and equipment used in the experiment are relatively safe and fool-proof, care
must be taken and, as always, some common sense used. Consult the physical chemistry lab TA‟s manual
for information about the specific experiment run during the course of the semester.
Experimental Setup
1) Connect the equipment required for the experiment as shown in the physical chemistry lab TA‟s
manual. Consult the sample containers for any specific precautions or concerns in the use of the
chemicals.
2) The bomb calorimeter requires an atmosphere of oxygen gas surrounding the sample. Obtain a
cylinder of the gas and connect to the system. Be sure to secure the gas cylinder to the lab bench
or other immobile, stationary object before attempting to perform any operations with the cylinder,
including connecting it to the system. Consult the standard safety procedures for use of gas
cylinders and specifically the information concerning the use of oxygen cylinders. Also determine
the type of regulator required and the care and handling of such before putting a regulator on the
system.
Experimental Procedure
1) Make a pellet of the sample using the pellet press. Examine the sample container for specific
information about the chemicals.
2) Place the pellet in the calorimeter and secure the top of the bomb. Take care to make sure that the
bomb is properly threaded into its connection on the calorimeter.
3) Flush the system with O2 gas. Make sure that the exhaust nozzle of the system is in a position to
minimize the chance that anyone will be harmed by objects in or around the bomb calorimeter that
may become dislodged while flushing the system. Close the exhaust nozzle and fill the sample to
approximately 25 atmospheres, watching the pressure gauge on the calorimeter to make sure that
the pressure does not become too high. After the system is brought to the correct pressure, close
the connection to the oxygen cylinder and then open the exhaust nozzle. After the pressure in the
bomb calorimeter returns to atmospheric, close the exhaust nozzle and repeat two more times.
4) Combustion of the sample. After the final flushing of the sample close the exhaust nozzle and again fill
the bomb calorimeter with oxygen to a pressure slightly greater than 25 atmospheres. MAKE
SURE THAT THE CONNECTION TO THE OXYGEN GAS CYLINDER IS CLOSED AND
PREPARE TO FIRE THE BOMB. If the pressure in the calorimeter is falling slightly, wait until
the pressure is 25 atmospheres and then press the fire button on the calorimeter, if the pressure is
steady simply press the fire button.
5) After the temperature in the bomb has reached a steady value prepare to remove the top of the system.
Open the exhaust nozzle of the system following the precautions listed in step 3. After the system
has returned to atmospheric pressure unthread the top of the bomb and remove. Check for
anything that appears unusual and then remove the sample holder. The parts of the system may
have become hot, so use caution in handing the components of the system. Clean the components
of the system and repeat experiment as many times as is called for.
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