Observation of liquid–liquid phase transitions in ethane at 300 K

Proctor, JE; Bailey, M; Morrison, I; Hakeem, MA; Crowe, IF

Abstract

We have conducted Raman spectroscopy
experiments on liquid ethane (C2H6) at 300 K, obtaining a
large amount of data at very high resolution. This has enabled
the observation of Raman peaks expected but not previously
observed in liquid ethane and a detailed experimental study of
the liquid that was not previously possible. We have observed a
transition between rigid and nonrigid liquid states in liquid
ethane at ca. 250 MPa corresponding to the recently proposed
Frenkel line, a dynamic transition between rigid liquid
(liquidlike) and nonrigid liquid (gaslike) states beginning in
the subcritical region and extending to arbitrarily high pressure
and temperature. The observation of this transition in liquid
(subcritical) ethane allows a clear differentiation to be made
between the Frenkel line (beginning in the subcritical region at
higher density than the boiling line) and the Widom lines (emanating from the critical point and not existing in the subcritical
region). Furthermore, we observe a narrow transition at ca. 1000 MPa to a second rigid liquid state. We propose that this
corresponds to a state in which orientational order must exist to achieve the expected density and can view the transition in
analogy to the transition in the solid state away from the orientationally disordered phase I to the orientationally ordered phases
II and III.

Citation

Proctor, J., Bailey, M., Morrison, I., Hakeem, M., & Crowe, I. (2018). Observation of liquid–liquid phase transitions in ethane at 300 K. Journal of Physical Chemistry B, 122(44), 10172-10178. https://doi.org/10.1021/acs.jpcb.8b07982

• Journal Article Type: Article
• Acceptance Date: Oct 16, 2018
• Online Publication Date: Oct 16, 2018
• Publication Date: Nov 8, 2018
• Deposit Date: Nov 8, 2018
• Publicly Available Date: Feb 22, 2019
• Journal: The Journal of Physical Chemistry B
• Print ISSN: 1520-6106
• Publisher: American Chemical Society
• Volume: 122
• Issue: 44
• Pages: 10172-10178
• DOI: https://doi.org/10.1021/acs.jpcb.8b07982
• Publisher URL: https://doi.org/10.1021/acs.jpcb.8b07982
• Related Public URLs: https://pubs.acs.org/journal/jpcbfk