Chemgineer
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Concentrating sulfuric acid by freezing
Is it feasible to concentrate say 80% sulfuric acid by freezing it and pouring off the liquid and discarding ice crystals?
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bnull
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It seems it depends on the initial concentration, if I'm not misinterpreting the phase diagram on page 6 of [1].
[1] Frank J. Zeleznik. Thermodynamic Properties of the Aqueous Sulfuric Acid System to 350 K. J. Phys. Chem. Ref. Data, Vol. 20, No. 6, 1991
(https://srd.nist.gov/JPCRD/jpcrd426.pdf).
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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chornedsnorkack
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Quote: Originally posted by Chemgineer  | | Is it feasible to concentrate say 80% sulfuric acid by freezing it and pouring off the liquid and discarding ice crystals? |
To begin with, that would be precisely diluting, and discarding acid.
This
https://www.vaisala.com/en/case/how-world-leading-sulfuric-a...
has a phase diagram in weight %.
As you see, at 80%, the solid phase is more concentrated so you´d be discarding acid and diluting the mother liquor.
Note that in the 60...77% range, the freezing of sulphuric acid and identity of solid phase is heavily up to chance. It is the equilibrium diagram
shown here (which at least is the maximum).
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