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Intuitively I would expect the thermal and electric conductivity to be positively related, and since electric conductivity increases with salinity, so should thermal. But according to this table (p.10) it decreases. Why is this?

Related: is there such a thing as the Wiedemann-Franz law for liquids like water?

There's a paper that has theoretical derivations about it, but it's nowhere to be found:
Predvoditelev, A. S., "Some invariant Quantities in the Theories of Heat Conductance and the Viscosity of Liquids," Russian Journal of Physical Chemistry, Vol. 22, p. 339 (1948)

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    $\begingroup$ Someone correct me, if I am wrong, but doesn't the expectation that thermal conductivity and electrical conductivity are correlated come from the special case of metal physics, where electron transport is the main source of both (in a certain temperature range)? There are marvelous counterexamples, for instance diamond, sapphire and pure crystalline silicon, which have enormous thermal conductivity, but very poor or basically non-existent electrical conductivity. $\endgroup$
    – CuriousOne
    Commented Aug 12, 2014 at 18:57
  • $\begingroup$ @CuriousOne, yes this confuses me also, yet i too have seen cases where the 2 are not correlated as such $\endgroup$
    – Nikos M.
    Commented Aug 12, 2014 at 19:05
  • $\begingroup$ @CuriousOne yes, that is what I based my expectation on. I agree that it's a bit loose to tie metals and saline liquids together like that. $\endgroup$
    – Jan M.
    Commented Aug 12, 2014 at 19:12
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    $\begingroup$ I completely misread the question. Somehow I read it as asking about specific heat. I'm withdrawing my answer, and then later I'll withdraw this comment. $\endgroup$
    – David Hammen
    Commented Aug 13, 2014 at 0:24

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(add my comment as an answer)

A short answer would be that although electric and thermal conductivity have (movement of free) electrons as their primary carriers, they operate on different ranges/frequencies/wavelengths, and as such the structure and energy zones of the material (or material compound) can have quite different factors for each type of conductance.

From the Wikipedia article on thermal conductivity:

In metals, thermal conductivity approximately tracks electrical conductivity according to the Wiedemann–Franz law, as freely moving valence electrons transfer not only electric current but also heat energy. However, the general correlation between electrical and thermal conductance does not hold for other materials, due to the increased importance of phonon carriers for heat in non-metals. Highly electrically conductive silver is less thermally conductive than diamond, which is an electrical insulator, but due to its orderly array of atoms it is conductive of heat via phonons

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  • $\begingroup$ Which field should I look into to learn more about this? $\endgroup$
    – Jan M.
    Commented Aug 13, 2014 at 16:16
  • $\begingroup$ @PatronBernardm there various fields which intersect on this area, like solid-state physics, electromagnetism, thermodynamics $\endgroup$
    – Nikos M.
    Commented Aug 13, 2014 at 17:29

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