title: Study of electrical conductivity response upon formation of ice and gas hydrates from salt solutions by a second generation high pressure electrical conductivity probe.
abstract: We recently reported the development of a high pressure electrical conductivity probe (HP-ECP) for experimental studies of formation of gas hydrates from electrolytes. The onset of the formation of methane-propane mixed gas hydrate from salt solutions was marked by a temporary upward spike in the electrical conductivity. To further understand hydrate formation a second generation of window-less HP-ECP (MkII), which has a much smaller heat capacity than the earlier version and allows access to faster cooling rates, has been constructed. Using the HP-ECP (MkII) the electrical conductivity signal responses of NaCl solutions upon the formation of ice, tetrahydrofuran hydrates, and methane-propane mixed gas hydrate has been measured. The concentration range of the NaCl solutions was from 1 mM to 3M and the driving AC frequency range was from 25 Hz to 5 kHz. This data has been used to construct an "electrical conductivity response phase diagrams" that summarize the electrical conductivity response signal upon solid formation in these systems. The general trend is that gas hydrate formation is marked by an upward spike in the conductivity at high concentrations and by a drop at low concentrations. This work shows that HP-ECP can be applied in automated measurements of hydrate formation probability distributions of optically opaque samples using the conductivity response signals as a trigger.
authors.affiliation: CSIRO Materials Science and Engineering, Ian Wark Laboratory, Bayview Avenue, Clayton, VIC 3168, Australia.
authors.forename: Barbara
authors.initials: B
authors.lastname: Sowa
authors.affiliation: School of Civil, Environmental and Chemical Engineering, RMIT University, Melbourne 3001, Australia.
authors.forename: Xue Hua
authors.initials: XH
authors.lastname: Zhang
authors.affiliation: CSIRO Earth Science and Resource Engineering, Ian Wark Laboratory, Bayview Avenue, Clayton, VIC 3168, Australia.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Kozielski
authors.affiliation: Department of Chemical and Biomolecular Engineering, School of Engineering, University of Melbourne, VIC 3010, Australia.
authors.forename: Dave E
authors.initials: DE
authors.lastname: Dunstan
authors.affiliation: CSIRO Materials Science and Engineering, Ian Wark Laboratory, Bayview Avenue, Clayton, VIC 3168, Australia.
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Hartley
authors.affiliation: CSIRO Materials Science and Engineering, Ian Wark Laboratory, Bayview Avenue, Clayton, VIC 3168, Australia.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Maeda