I bought a brine hygrometer the other day. At a garage sale. It was
marked 0 - 100% at 60degF. So I found a tall glass vase and put a half
inch of salt into it and filled it with water.
The hygrometer read close to 100% so I was satisfied with my $2 purchase.
A day later, there was a thin crystalline film on the stem. A week
later, a thick encrustation.
I was surprised. Reminded me of the beginning metaphor for thermionic
current. Perhaps it would make a slow rectifier? Is there a ready
explanation for the salt transport?