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Lowing boiling point of water

by Blenton
Tags: boiling, lowing, point, water
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Blenton
#1
Dec2-09, 02:41 AM
P: 193
Is there any catalyst or substance that can do this?
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Borek
#2
Dec2-09, 03:22 AM
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A lot depends on what you mean by "water". Obviously you are ready to accepts some mixture - vodka is such a mixture, and it boils at much lower temperature.

That is assuming by "lowing" you meant "lowering".

So short question, so many meanings
Andre
#3
Dec2-09, 03:40 AM
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Hmmm I seem to remember that in my time the boiling point was defined as the boiling temperature of the pure liquid at one atmosphere (or sea level). But it seems to be defined as the normal boiling point now

Any fluid boils at reduced temperatures at reduced ambient pressure. That limited us from flying above 62.000 feet, then blood starts to boil.

Borek
#4
Dec2-09, 04:23 AM
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Lowing boiling point of water

I suppose the question is meant to be understood as "lower boiling point after something has been added all other things being equal". But it is as vague as a question can be.

Quote Quote by Andre View Post
Hmmm I seem to remember that in my time the boiling point was defined as the boiling temperature of the pure liquid at one atmosphere (or sea level).
I think you have just forgot that part about "normal" or "standard" - after all, boiling point was always pressure dependent
lightarrow
#5
Dec2-09, 07:13 AM
P: 1,521
As Borek wrote, is impossible to lower the BP of water without significant amounts of another chemical (so, "catalythic" amounts are excluded).
Here there are some values of BP of mixes water + other liquid:
http://en.wikipedia.org/wiki/Azeotrope_(data)

From these data you see how is difficult to lower the BP of water: if you want to use little amounts of chemicals, you could, e.g. use 9% benzyl alcohol, but the BP lowers of 0.1C only.; or you could use cyclohexanol and you lower the BP of 2.2C, but you have to use at at 20%...
Borek
#6
Dec2-09, 07:30 AM
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Note that many substances will not lower, but raise the boiling point; that depends on the vapor pressure of the substance.
pzona
#7
Dec2-09, 09:36 AM
P: 233
If you mean regular tap water, I would imagine that removing some of the ions (Ca2+, Mg2+, etc.) would lower the boiling temperature slightly because of colligative properties. You can do this with a Brita filter, but the boiling point depression depends on the initial concentrations of the ions in this case. I'm pretty sure this isn't what OP meant though.
Blenton
#8
Dec5-09, 12:21 AM
P: 193
Hmm yes it was what I thought. It would probably against conservation of energy unless for some instance energy going into boiling water was wasted by a large degree.

I suppose the question is meant to be understood as "lower boiling point after something has been added all other things being equal". But it is as vague as a question can be.
Sorry I didn't notice the title, my meaning of Lowering the boiling point of water.

As Borek wrote, is impossible to lower the BP of water without significant amounts of another chemical (so, "catalythic" amounts are excluded).
Here there are some values of BP of mixes water + other liquid:
http://en.wikipedia.org/wiki/Azeotrope_(data)

From these data you see how is difficult to lower the BP of water: if you want to use little amounts of chemicals, you could, e.g. use 9% benzyl alcohol, but the BP lowers of 0.1C only.; or you could use cyclohexanol and you lower the BP of 2.2C, but you have to use at at 20%...
Interesting, but it does seem that for such a large quantity only a small gain is achieved.


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