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On Jul 9, 2006, at 2:37 PM, Michael Edmiston wrote:
. . . If "dirty" means inorganic chemicals with negligible vapor
pressure
(such as desalination of water) then a single distillation can get
fairly pure water, . . . This is typically considered "physical
chemistry"
and is fully described in college-level physical chemistry texts.
Salts, such as K2CO3 and NaCl, do not sublimate intensively. Otherwise
the vapor pressure of their molecules in air would not be very low. But
once dissolved in water these substances become mostly mixtures of
positive and negative ions (cations and anions). What is the "vapor
pressure" of ions? Something is preventing ions from being present in
bubbles of the escaping steam, when the electrolyte is boiled.
Otherwise distilled water would probably be salty. What keeps ions out
of the bubbles? Electrolytes are macroscopically neutral.
Ludwik Kowalski
Let the perfect not be the enemy of the good.
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