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The document discusses the phase diagram of nitric acid and how to distill dilute and concentrated nitric acid solutions. Dilute nitric acid below 68% concentration forms an azeotrope during distillation and cannot be further concentrated. Nitric acid above 68% concentration can be distilled to produce pure nitric acid and leave the azeotrope in the distillation flask.

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mohamedmero2001
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39 views4 pages

Safetyyy

The document discusses the phase diagram of nitric acid and how to distill dilute and concentrated nitric acid solutions. Dilute nitric acid below 68% concentration forms an azeotrope during distillation and cannot be further concentrated. Nitric acid above 68% concentration can be distilled to produce pure nitric acid and leave the azeotrope in the distillation flask.

Uploaded by

mohamedmero2001
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Faculty of engineering, Alexandria university

Gas and petrochemical department


Safety

Phase diagram of nitric acid

Done by: Engy Mahmoud Gahin


ID: 7056

Submitted to: Dr. Hassan Farag


Using the diagram

Distilling dilute nitric acid

Start with a dilute solution of nitric


acid with a composition of
C1 and trace through what
happens.

The vapour produced is richer in


water than the original acid. If you
condense the vapour and reboil it, the new vapour is even richer in
water. Fractional distillation of dilute nitric acid will enable you to
collect pure water from the top of the fractionating
column.

As the acid loses water, it becomes more concentrated. Its concentration


gradually increases until it gets to 68% by mass of nitric acid. At that point, the
vapour produced has exactly the same concentration as the liquid, because
the two curves meet.

You produce a constant boiling mixture (or azeotropic mixture or azeotrope). If


you distil dilute nitric acid, that's what you will eventually be left with in the
distillation flask. You can't produce pure nitric acid from the dilute acid by
distilling it.

Distilling nitric acid more concentrated than 68% by mass

This time you are starting with a concentration C2 to the right of the azeotropic
mixture.

The vapour formed is richer in nitric acid. If you condense and reboil this, you
will get a still richer vapour. If you continue to do this all the way up the
fractionating column, you can get pure nitric acid out of the top.

As far as the liquid in the distillation flask is concerned, it is gradually losing


nitric acid. Its concentration drifts down towards the azeotropic composition.
Once it reaches that, there can't be any further change, because it then boils
to give a vapour with the same composition as the liquid.
Distilling a nitric acid / water mixture containing more than 68% by mass of
nitric acid gives you pure nitric acid from the top of the fractionating column
and the azeotropic mixture left in the distillation flask.

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