Chemistry Reference
In-Depth Information
Fig. 2.1
Schematic of LP-1
installation:
1
, heater;
2
,
conducting rods;
3
, sample;
4
, sliding cylinder;
5
, guide
rod;
6
, load;
7
, chopper;
8
,
photodiode;
9
, light source;
10
, mirror
Pt
Pt/Rh
electrical pathway
vacuum
water
axle. As it rotates together with the axle, chopper
7
modulates a light beam incident
on photodiode
8
, which is connected to a recorder.
In installations utilized in earlier studies [1, 2, 3, 4, 5], linear potentiometers
were used as recorders. However the potentiometer sensors were easily damaged
because they reacted with the gaseous decomposition products. Under these condi-
tions, the accurate recording of slight displacements is impossible. The application
of the installation described above allows linear pyrolysis data to be recorded with
the required accuracy and reliability for systems that are interesting from various
points of view and which are characterized by a very wide range of decomposition
rates (
U
10
−
19
ms
−
1
).
When in operation, the installation is covered by an acrylic or thick glass
dome. The inner space of the installation can be evacuated or filled with inert gas
through a connecting pipe (the pressure in the installation is measured by a vac-
uum manometer). Since the conducting rods are heated up to quite high temper-
atures by passing an electric current through them (up to 10
3
A) and transferring
heat from heater
1
, the hollow output ends of the rods are cooled by circulating
water.
Installation LP-2, which was used to measure rates of linear pyrolysis under el-
evated pressure, differs from LP-1 due to the presence of a constant-pressure bomb
containing the heater and the kinematic unit. A schematic of installation LP-2 is
shown in Fig. 2.2. Sample
7
moves downward and is pressed onto a hot plate by
ring loads
8
fixed onto cylinder
9
.
Since the temperature in the top part of the bomb rises up to 80-100
◦
C
during prolonged experiments, solid-state photodiode
1
is placed in a protective
water-cooled double-walled copper container. In order to improve observations of
10
−
3
≈
−
