APPARATUS FOR DETERMINING THE CRITICAL POINT Description and Specifications for Lab Tenders
APPARATUS FOR DETERMINING THE CRITICAL POINT.
APPARATUS FOR DETERMINING THE CRITICAL POINT This very accurate apparatus is used to study the compression
and the liquefaction of gas, to determine the critic point, and
to detect isothermal lines on diagram p-V ( Clapeyron diagram).
The gas under test is the sulfur hexafl uoride (SF6) that reaches
its critical temperature at 318,6 K (45,5°) and its critical
pressure of 3,76 MPa (37,6 bar), and it enables to create a
simple structure.
This apparatus includes a transparent measure cell, that it is
particularly hermetic and resistant to pressure. An adjustable
wheel enables to vary the internal volume of the cell: the
variation of the volume is indicated on fi xed and rotating scales,
with an accuracy rating of 1/1000 of the maximum volume.
Pressure is output by a hydraulic system containing castor
oil of good quality for medical purpose. The measuring cell
and the hydraulic system are separated by a membrane that
moves as the volumes increases. Consequently the pressure
gradient between the measuring cell and the chamber of oil,
is negligible.
A pressure gauge measures oil pressure instead of gas
pressure, without any dead volume inside the measuring cell.
Thus, during the transition from gaseous to liquid phase, and
vice versa, it is possible to observe how the fi rst drop of liquid
forms, and how the last gas bubble disappears.
The measuring cell is closed in a transparent water chamber. A
circulation thermostat enables to keep a constant temperature,
that can be easily set, read and checked with a thermometer.
Thus it is easy to plot volume, pressure and temperature on
p-V or pV-p diagrams, obtaining good results from a qualitative
point of view.
Pressure and volumetric corrections depending on
temperature, lead to accurate results from a quantitative point
of view (respect to reference standard values).
TRAINING PROGRAM
Liquid and gaseous state
• Dynamic state during compression and decompression phase
• Critical opalescence
• Determination of transition point at different temperatures
Quantitative measurements
• Explanation of critical point and of critical temperature
• Detection of isothermal lines in p-V diagram
(Clapeyron diagram)
• Detection of isothermal lines in pV-p diagram
(Amegat diagram)
• Pressure waves of saturated steam
• Deviations of real gas from ideal gas state
TECHNICAL CHARACTERISTICS
Critical temperature: 318.5 K (45.5°C)
Critical pressure: 3.76 Mpa (37.6 bars)
Critical volume: 197.4 cm3/mole
Critical density: 0.74 g/mole
Temperature range: 10 – 60°C
Maximum pressure: 6.0 Mpa (60 bars)
Maximum volume: 15.7 cm3
Diameter of pressure gauge: 160 mm
Orifi ce for temperature sensor: diameter of 6 mm
Connections through thermal instrument/means: 7 mm diameter
Connections of valve’s reducer: 1/8’’ diameter
Standard gas connection: 3.5 mm diameter
Dimensions: 380 x 200 x 400 mm
Weight: approximately 7 kg
Components
This equipment includes:
• Apparatus for critical point determination: it is fi lled with
hydraulic oil (castor oil) but without gas test (SF6), it has
a gas connection mounted on gas bomb MINICAN® and a
protection for gas tube connection
• 1 oil fi lling device
• Angled Allen wrench of 1,3 mm for locking screw of
turntable scale
• 1 fl exible hose of plastic material, 3 mm inner diameter
• 1 1/8”pipe connection tube (11)
• 1 oiler
• 1 silicon tube 6 mm
• 1 gas MINICAN® container
• 1 pressure regulator
• 1 immersion thermostat
• 1 pressure gauge
• 2 thermometers