Chemistry Reference
In-Depth Information
Fig. 11.2
Circuit principle of
AVD-5:
1
, gas burette;
2
,
manometer and photocell;
3
,
baseplate;
4
, compensation
vessel;
5
, compensation
vessel tray;
6
, guiding rod;
7
,
thread connecting the
compensation vessel tray with
the electronic recorder slide;
8
, recorder slide;
9
, terminal
switch;
10-12
, hydroseals
used as a sensor in the engine follow-up controls. The use of hydroseals in the line
connecting the burette volume and the ambient atmosphere and terminal switches in
the reversible motor-compensation vessel-potentiometric sensor of the compensa-
tion vessel system ensures completely automated AVD operation. As gas collects in
the system the compensation vessel moves down, and this is recorded on the elec-
tronic potentiometer chart. When the burette is completely filled with the gas (the
lowest position of the compensation vessel), the first terminal switch triggers the
lifting of the compensation vessel by the reversible motor, while the gas is released
to the ambient air through a hydroseal. At the uppermost position of the compensa-
tion vessel the second terminal switch triggers the return of the follow-up controls
to the normal working mode.
Thus one obtains a saw-toothed curve corresponding to the recorded process of
gas evolution. In the experiments, devices with separated follow-up control and
recording units (AVD-2 and AVD-3) as well as a quick-response device (AVD-5)
were used. In AVD-5, the follow-up controls of the electronic recorder are re-
sponsible for the simultaneous motion of the compensation vessel and the recorder
printing head. AVD-5 can be used for recording processes that are characterized
by gas-evolution rates of up to 40 ncm
3
s
−
1
, and up to 2 ncm
3
s
−
1
when AVD-2
and AVD-3 are used. Schematic diagrams and a photo of the devices are given in
Figs. 11.1-11.3.
11.2.2 Microdroplet Device
The operation of this device is based on liquid displacement from a closed vessel
kept at a constant pressure due to the evolution of gas during the decomposition of
the liquid under study (Fig. 11.4). The increase in the volume of the displaced liq-
uid (which is identical to the volume of the evolved gas) is recorded as a function of
