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CE 110 Diffusion in Liquids and Gases
Education / GUNT Hamburg / Process Engineering / Mechanical Process Engineering /

Diffusion is the microscopic mass transport of particles such as atoms, molecules and ions due to differences in concentrations. It plays an important role in numerous processes. For example, diffusion can bring together the reactants in chemical reactions and, in some cases, it can be the rate-limiting step for the process.
  CE 110 is equipped with two experimental units for investigating diffusion in liquids and gases. To investigate diffusion in liquids, a concentrated salt solution is used. The solution is contained in a U-tube, one end of which has a disc with several vertical capillaries. The U-tube is immersed into a tank containing demineralised water so that the disc with the capillaries is positioned below the surface of the water. The concentration gradient between water and the solution causes the salt ions to move out of the U-tube through the capillaries into the demineralised water. The capillaries ensure that the ions move in one dimension. A stirrer in the tank prevents the salt concentration increasing near to the disc, thus preventing concentration differences in the tank. A conductivity meter measures the salt concentration in the tank.
  To investigate diffusion in gases, a highly volatile solvent is used. The solvent is contained in a vertical tube which is immersed into a heated water bath. The thermal energy from the water bath causes the solvent to evaporate. A fan generates an airflow, which moves horizontally at the upper end of the tube. The gaseous solvent diffuses due to the concentration gradient from the surface of the liquid solvent upwards to the pure airflow. The airflow transports the solvent molecules away, thus

ensuring a constant concentration at the upper end of the tube. The volume of liquid solvent in the tube decreases over time. A scale microscope enables the level to be determined. A heater with controller keeps the temperature in the water bath constant.

  The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.


Learning Objectives / Experiments

- fundamentals of diffusion: Fick's law
- derivation of the calculation formula for the diffusion

  coefficients for the given experimental conditions 
- determination of the diffusion coefficient for the

  mass transport in gas
- determination of the diffusion coefficient for the

  mass transport in liquid


[1] investigation of diffusion in liquids and gases
[2] transparent tank with magnetic stirrer, conductivity meter and U-tube with capillaries for investigating diffusion in aqueous solutions
[3] evaporation of a highly volatile solvent with a diffusion tube in a heated water bath for investigating diffusion in gases
[4] removal of gaseous solvent at the upper end of the diffusion tube with a fan
[5] heater with controller and sensor for adjusting the temperature in the water bath
[6] height-adjustable microscope for monitoring and determining the solvent volume in the diffusion tube
[7] separate display and control unit contains temperature controller and fan


Technical Data

Tank with stirrer: approx. 1.5L
Speed stirrer: 0...1.500min-1
253 capillaries made of glass
- diameter: 1mm, length: 5mm
Water bath: approx. 2L
Diffusion tube for solvent
- diameter: 3.4mm, length: 85mm
Power output heater: approx. 150W
Fan: 120...320L/h
Microscope scale division: 0,1mm
Measuring ranges
- temperature: 0...100°C
- conductivity: 0...200mS/cm


Dimensions and Weight
LxWxH: approx. 170x170x280mm (experimental unit for diffusion in liquids)
LxWxH: approx. 220x280x420mm (experimental unit for diffusion in gases)
LxWxH: approx. 260x265x120mm (display and control unit)
Weight: approx. 65kg
Required for Operation
230V, 50/60Hz, 1 phase
Scope of Delivery

1 experimental unit for diffusion in liquids
1 experimental unit for diffusion in gases
1 display and control unit

1 conductivity meter
1 magnetic stirrer with 2 magnetic stir bars

1 stopwatch
1 set of instructional material

Order Details

083.11000  CE 110  Diffusion in Liquids and