(Professional Student)
12-14-01 01:30
No 247300
Can anyone explain to me how a metal hydroxide, like NaOH, reacts to remove water?
I have never heard of a metal hydroxide being used to dry liquids. My list of 38 drying agents does not include any hydroxides.
Sodium and potassium metal dry liquids by forming the metal hydroxides and hydrogen gas, this I know.
Digging through my vast private library, I uncovered an organic lab text from 1950 that calls for the use of NaOH pellets to dry N-Methylpyrrole.
Is this simply an ion solubility question?
[EDIT] maybe ion solubility wasn't the right term. In an
excess of NaOH, there would be a continuous reaction between
OH- and water. But water will always be present. Does this
reaction tie up the water, thus removing it from the organic
liquid?
thanks
Back to the Primitive
(Hive Bee)
12-14-01 02:01
No 247313
What you need to do is leave some sodium hydroxide crystals out in a humid atmosphere and observe what happens, the term is hygroscopic
Drying agents are classified as either physical or chemical. Chemical agents are classified as hydrate forming salts, oxides, acids, bases (caustics) and metals. Caustics are the best agents for drying amines, if this fact isn't apparent in your library, you need to consider an expansion plan
(Professional Student)
12-14-01 02:11
No 247316
hahaha,... give me a break dude.
Back to the Primitive
(Professional Student)
12-14-01 03:52
No 247341
gee. well at room temp i guess if you have 1 mole NaOH and 1 mole water, you could get a hydrate of sorts. 1 mole NaOH and 2 moles water, you get dissolved NaOH. how sweet
Back to the Primitive
(Hive Bee)
12-14-01 10:34
No 247440
give me a break dude.
Well, what I don't understand is why a so called "professional student" can't take some initiative and make their way to the library to do their own research, it's good to get a little exercise Adsorption is a surface phenomena, the interface is the solid NaOH and the water present in solution. As the process advances, a layer of NaOH saturated water can be observed. If you would have done the simple experiment as I asked, you would have observed the crystals adsorbing the water from the air, and as you may have heard, "a picture is worth a thousand words". CRC doesn't list a hydrate, so the process you've theorized is probably not the case. I imagine hydrogen bonding is at work (big surprise}, the equilibrium is driven toward a saturated solution.
(Stoni's sexual toy)
12-14-01 10:54
No 247444
> gee. well at room temp i guess if you have 1 mole NaOH
> and 1 mole water, you could get a hydrate of sorts. 1
> mole NaOH and 2 moles water, you get dissolved NaOH.
> how sweet
What if you have 5 moles of NaOH and 1 mole of H2O? Where will the water go preferentially? Into the organic or into the inorganic substance? Will an aqueous solution of NaOH form? Or will the NaOH remain a solid even though it has 20% water absorbed? Can the NaOH be removed by decantation/filtration? What do you think?
(Professional Student)
12-14-01 16:10
No 247493
no shit lugh. i dont need to do the 'experiment' because
i've seen it a hundred times. i understand what adsorption
is, and hydrogen bonding. i would say f
ckoff,but i'll just say goodbye.
Back to the Primitive
(Hive Bee)
12-14-01 16:26
No 247494
no shit lugh. i dont need to do the 'experiment' because i've seen it a hundred times. i understand what adsorption is, and hydrogen bonding. i would say
f
Whatever floats your boat
If you knew the answer, why start this thread? If you believe there are only 38 drying agents known to organic chemists, you need to expand your horizons Hydroxides have been used as drying agents for almost two centuries, this fact isn't exactly the breakthrough of the century
(Professional Student)
12-14-01 16:38
No 247496
What if you have 5 moles of NaOH and 1 mole of H2O? Where will the water go preferentially water will be drawn out of the organic. i doubt you would be able to decant it or filter it. there would be dissolved and undissolved NaOH. well you could decant off most of the organic if it was something like ether or toluene.
Back to the Primitive
(Professional Student)
12-14-01 16:58
No 247500
whatever - i use what's used in the labs. in the four
years i've been working in the lab, no person has ever used
a hydroxide to dry a liquid. the only mention of using
NaOH as a drying agent i have seen is in a 50 year old
lab text. have to keep an open mind though, and remember
how things used to be done. i understand how it works,
doesn't seem like a particularly attractive method, but
if it works - it works.
Back to the Primitive
(Stoni's sexual toy)
12-14-01 18:13
No 247517
> water will be drawn out of the organic.
Yes.
> i doubt you would be able to decant it or filter it. there
> would be dissolved and undissolved NaOH.
No. There won't be any liquid NaOH.
Example: commercial KOH is 85%, a few (maybe 2 or 3) % K2CO3, rest water. Yet it is a solid.
> whatever - i use what's used in the labs. in the four
> years i've been working in the lab, no person has ever
> used a hydroxide to dry a liquid.
I've seen KOH being used to dry solvents repeatedly, even though it already contains up to 15% of water. Someone I know used KOH/CaCl2 effectively to dry huge amounts of acetone/THF mixture used in flash chromatography, having a 6L distillation unit running up to 12 hours a day for solvent recycling. It definitely works.
(Old P2P Cook)
12-14-01 18:41
No 247523
. i would say fckoff, but i'll just say goodbye.
Promises, promises ...
(Hive Bee)
12-14-01 20:53
No 247561
Ref:
Sodium Hydroxide forms hydrates with 7,5,4,3.5,3.11,2(mp 12.7c)and 1(mp 64c)H2O, and potassium hydroxide with 4(mp -32.7c),2(mp 35.5c),1.5 and 1(mp 143c)H20 (Pickering, JCS., 1893, 63, 890)
There's the facts !!!!!
(Hive Bee)
12-15-01 00:06
No 247650
>Digging through my vast private library,
Hey b159510:
I bet if you tossed all the Dr. Suess books, that library of yours would suddenly look ALOT smaller...
\\|//
τΏτ -- Semper ubi sub ubi!
\O/
'''
(Professional Student)
12-15-01 00:53
No 247677
timsong- thanks for the Ref.
Buster- Everyone knows Dr. Suess (god rest his soul)
was a genius. You'll have to sweeten your offer
if you want to get those flippers on my collection.
Back to the Primitive
(Stoni's sexual toy)
12-15-01 22:07
No 247910
Who is Dr. Suess?
(Old P2P Cook)
12-15-01 22:13
No 247914
You really don't know!? Is he not known outside the US?
(Stoni's sexual toy)
12-15-01 22:26
No 247918
No, I don't know him.
But I found out what they were talking about after I considered buster's spelling problems (it's either pulchritude or brains, can't have both
except in very rare cases like mine)
(Hive Bee)
12-15-01 22:28
No 247921
Who is Dr. Suess?
A very famous author of children's books. Should be some info at amazon.com
(Hive Bee)
12-16-01 01:17
No 247989
"Green Eggs and Ham" is a classic, a "must-read". Every civilized person should have this book in their library. I'm sure the pulchritudinous b159510 would agree with me on this one.
\\|//
τΏτ -- Semper ubi sub ubi!
\O/
'''
(Master Searcher)
12-16-01 01:38
No 248000
[image] [image]
![[image]](../picproxie_docs/000247300-file_zrsq.gif){kind=link}
![[image]](../picproxie_docs/000247300-file_ezsg.gif){kind=link}
http://www3.overture.com/d/sr/?xargs=00u
[image]
![[image]](../picproxie_docs/000247300-file_v4ze.gif){kind=link}
Edit after locking thread: One thing I should say is that I found KOH to be a lot more hygroscopic than NaOH. Some KOH I had absorbed so much water that it formed a solution and overflowed out of the container which had a cap that wasn't perfectly air tight.
http://www.geocities.com/dritte123/PSPF.
(Chief Bee)
12-16-01 01:49
No 248005
Oh, this is so off topic now I'm gonna scream.
(Hive Bee)
12-16-01 01:49
No 248006
Oh man that's tripped me back, I remember having that 'cats big hat' book when I was a kid