An undergraduate laboratory experiment to determine the critical point of SF6 using light scattering at selected wavelengths. (1st October 2020)

• Record Type: Journal Article
• Authors: Murray, Andrew James; Harvey, Matthew
• Is Part Of: European journal of physics. Volume 41:Number 6(2020:Nov.)
• Publication Date: 2020-10-01
• Subjects: critical opalescence -- critical exponent -- light scattering -- undergraduate experiment; Physics -- Periodicals; Physics -- Study and teaching (Higher) -- Europe -- Periodicals; 530
• DOI: 10.1088/1361-6404/aba225
• Languages: English
• ISSNs: 0143-0807

Abstract

Abstract: Molecules and atoms that are normally gaseous at room temperature and pressure will liquefy or solidify as their temperature reduces or their pressure increases. In the apparatus detailed here a commercial cell contains pressurized SF6 so that it exists in both gaseous and liquid states, with the density of both being similar at room temperature. The critical point on the phase diagram can then be investigated, by elevating the temperature of the cell so the densities of liquid and gas equalize. Under these conditions light passing through the cell is highly scattered by density fluctuations in the fluid. By measuring the transmitted light as a function of both temperature and wavelength, the critical exponent can be derived and the effects of light scattering with wavelength investigated.