Chemistry Reference
In-Depth Information
Fig. 5 Photograph of a standard scanning transitiometer (from BGR TECH, Warsaw). The
calorimetric detector, which can be moved up and down over the measuring and reference
calorimetric vessels (in twin differential arrangement), is shown in its upper position. In this
position, the calorimetric vessels, which are firmly fixed on the stand table, are then accessible for
loading
over the two calorimetric vessels (i.e., the measuring and reference vessels). These
two vessels are firmly fixed on a stand, to which the displacement system is itself
attached in such a way that the vessels always find the same positions inside the
calorimetric detectors when the calorimetric body is moved down to its working
position (see Fig.
5
). When performing measurements near 0
C or below, dry air is
pumped through the apparatus in order to prevent the condensation of water vapor
from air.
The variable volume is realized with a stepping motor-driven piston pump. The
resolution of the volume detection is ca. 5.24
10
6
cm
3
per step (as found by
measurement of the piston displacement for given numbers of steps) and the total
variable volume is 9 cm
3
. The calorimetric block can then be lifted to load the
sample into the cell, or for cleaning.
The pressure sensors are connected close to the piston pump. Pressure can
be detected with a precision of
4 kPa. The connection between the cryostat
and the heating/cooling shield of the calorimetric block is made via two flexible
