| Pages:
1
..
9
10
11
12
13
..
30 |
querjek
Hazard to Self
Posts: 76
Registered: 26-8-2008
Member Is Offline
Mood: No Mood
|
|
I have a solution of 90% acetic acid.
The bps of acetic acid and water only vary by 18deg.C.
I don't necessarily need all of the water out, but it would be nice, and googling "acetic acid distillation" has only sorta helped.
What would be my best be to concentrate the acetic acid?
Thanks!
it's all about chemistry.
|
|
|
ammonium isocyanate
Hazard to Others
Posts: 124
Registered: 13-7-2009
Location: USA - Midwest
Member Is Offline
Mood: sick 
|
|
There are a number of ways you could do it. One would be to react the solution with a base and then acidify the salt with sulfuric or phosphoric
acid. This is the method I use, but only because I start with vinegar that is only 4% acetic acid by weight. For you, I would recommend the use of a
dessicant such as MgSO4 or CaCl2.
|
|
|
manimal
Hazard to Others
Posts: 180
Registered: 15-1-2008
Member Is Offline
Mood: ain't even mad
|
|
Quote: Originally posted by ammonium isocyanate  | | There are a number of ways you could do it. One would be to react the solution with a base and then acidify the salt with sulfuric or phosphoric
acid. This is the method I use, but only because I start with vinegar that is only 4% acetic acid by weight. For you, I would recommend the use of a
dessicant such as MgSO4 or CaCl2. |
How do you do this? Do you add the unhydrous sodium acetate to H2SO4, and then distill?
|
|
|
ammonium isocyanate
Hazard to Others
Posts: 124
Registered: 13-7-2009
Location: USA - Midwest
Member Is Offline
Mood: sick
|
|
| Quote: Originally posted by manimal | | Quote: Originally posted by ammonium isocyanate | | There are a number of ways you could do it. One would be to react the solution with a base and then acidify the salt with sulfuric or phosphoric
acid. This is the method I use, but only because I start with vinegar that is only 4% acetic acid by weight. For you, I would recommend the use of a
dessicant such as MgSO4 or CaCl2. |
How do you do this? Do you add the unhydrous sodium acetate to H2SO4, and then distill? |
You got it. In fact, if you use sulfuric acid you don't need totally anhydrous acetate as the sulfuric acid acts as a dessicant. 
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
| Quote: Originally posted by querjek | I have a solution of 90% acetic acid.
The bps of acetic acid and water only vary by 18deg.C.
I don't necessarily need all of the water out, but it would be nice, and googling "acetic acid distillation" has only sorta helped.
What would be my best be to concentrate the acetic acid?
Thanks! |
This is an old problem, and there are threads on it that you should consult.
MgSO4 and CaCl2 won't remove the last of the water from 90% acetic acid. It's very difficult to fractionally distill off the water. Since you're
already almost to glacial acid converting to NaOAc and distilling with H2SO4 is fairly wasteful. And the NaOAc does need to be anhydrous, I wish
people wouldn't give advice when they're clueless. It doesn't make them look smart to say something when it's obvious that they are just blowing
smoke out their arse. Distilling the NaOAc trihydrate with H2SO4 will give approximately the 90% acid you already have.
One way is to add enough EtOAc to form an azeotrope with the water in your 90% acid and distill with a good fractionating column. First the azeotrope
will distill at about 70 C, then the EtOAc will come over at about 77 C, and finally glacial AcOH will distill at about 118 C.
But consult the existing threads. Their has been a lot of discussion about this.
In one of those threads, SC Wack posted a promising looking patent in which wet AcOH is frozen in vacuum and the H2O evaporated off leaving crystals
of AcOH. It looked workable, but it didn't work for me. I think it should under the right conditions.
[Edited on 26-7-2009 by entropy51]
|
|
|
ammonium isocyanate
Hazard to Others
Posts: 124
Registered: 13-7-2009
Location: USA - Midwest
Member Is Offline
Mood: sick
|
|
You could use P4O10 as a dessicant, but that is hard to come by (at least for me).
I have a question of my own. I had a solution of CuSO4 and tried to dispose of it with NaHCO3 and Na2CO3. A volumous greenish precipitate formed.
However, a deep blue solution remained, presumably containing cupric cations. I can't think of any reason ammonia or any other chemical would be
present that would complex with Cu++ ions. Does HCO3- form any complex with copper? I can't really dispose of this solution until I know it contains
no copper ions. Any ideas for precipitating them?
|
|
|
turd
National Hazard
Posts: 800
Registered: 5-3-2006
Member Is Offline
Mood: No Mood
|
|
Is it possible to obtain 95% on a Reimer-Tiemann? I was always under the impression that yields of the Reimer-Tiemann are mediocre, yet SciFinder
claims that some Chinese claim that they obtained 95% on a modified Reimer-Tiemann (with tertiary amine) on p-methoxyphenol:
Liaoning Shifan Daxue Xuebao, Ziran Kexueban (2007), 30(3), 328-329. (Journal written in Chinese)
Here: http://pubs.acs.org/doi/suppl/10.1021/ol800507m another group of Chinese claims 91% for Et3N, CH3CN, paraformaldehyde.
The base must be a tertiary amine, since other amines would condense with the aldehyde/formaldehyde and give water, right?
And triethanolamine (OTC for me) cannot be used, since the OH groups are too acidic, isn't it?
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
Is Chinese borosilicate glass the same as Pyrex?
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by ammonium isocyanate | ..I had a solution of CuSO4 and tried to dispose of it with NaHCO3 and Na2CO3. A volumous greenish precipitate formed. However, a deep blue solution
remained, presumably containing cupric cations. I can't think of any reason ammonia or any other chemical would be present that would complex with
Cu++ ions. Does HCO3- form any complex with copper? I can't really dispose of this solution until I know it contains no copper ions. Any ideas for
precipitating them?
|
The basic copper carbonates, you're not going to see true CuCO3, form soluble complexes with excess carbonate. Try boiling in a wide mouthed
container for a quarter hour or so, this may convert all the copper to cupric oxide.
Alternatively let the solution evaporate to dryness.
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
Indeed, it's better to neutralize a copper solution with sodium hydroxide than carbonate for exactly this reason.
You do run the risk of ammonia impurity and cuprate formation, but those should be controllable with purity and pH.
Boiling, so CuO forms immediately, is always a good idea. Besides precipitating a stable form, it also settles faster and denser.
Tim
|
|
|
ammonium isocyanate
Hazard to Others
Posts: 124
Registered: 13-7-2009
Location: USA - Midwest
Member Is Offline
Mood: sick
|
|
Hmmm... I guess I'll have to try boiling, as evaporating isn't an option given that I have ~600mL of the solution.
An interesting side-note, I added more carbonate to one batch than the other, and then tried nutralizing that one with vinegar. It is now a more
turquoise/light blue color, whereas the other a deeper blue. Addition of alkali halides to the light blue solution (just in case Cu++ ions had been
reduced to Cu+ ions) results in the evolution of copious quantaties of gas, predsumably CO2 as no odor was observed, it did not support flame, and did
not really affect a pH test strip very much, nor was any smoke-like affect shown, as would be expected from hydrogen halides. No precipitate forms.
No reaction is observed with the other solution.
Addition of almunium or magnesium poweder to the dark blue solution results in a single-displacement reaction, yielding what appears to be copper
metal and leaving a purple solution behind. No reaction is observed with the light blue solution.
|
|
|
turd
National Hazard
Posts: 800
Registered: 5-3-2006
Member Is Offline
Mood: No Mood
|
|
Why do you post if your intent is not to help?
Scifinder states the reagents as 4-methoxyphenol, CHCl3, EtOH, NaOH and Et3N. My bet is on translation error or nonsense publication. I've seen too
many of both lately.
|
|
|
ammonium isocyanate
Hazard to Others
Posts: 124
Registered: 13-7-2009
Location: USA - Midwest
Member Is Offline
Mood: sick
|
|
What is the best way to dispose of chromate/dichromate compounds? I don't have any soluble lead (II) compounds, so I can't go the lead chromate
route.
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
Flood the reaction mixture with sulfites and acid (generate SO2 in-situ), reducing all hexavalent chromium to relatively harmless Cr(III). You may
want to heat a bit just to make sure it goes to completion.
[Edited on 7-29-09 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
Mood: No Mood
|
|
PbCrO4 (which occurs as the rare mineral crocoite) is, like PbSO4, only very slightly soluble, which would, if a soluble Pb salt were available, allow
it to be used to precipitate Cr(VI) from solution. It, and ZnCrO4 which is more soluble and less toxic, is of use as an intense red paint pigment,
especially in anti-corrosive roof paints and metal primers.
[Edited on 30-7-09 by JohnWW]
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
| Quote: Originally posted by turd |
Why do you post if your intent is not to help?
Scifinder states the reagents as 4-methoxyphenol, CHCl3, EtOH, NaOH and Et3N. My bet is on translation error or nonsense publication. I've seen too
many of both lately. |
The answer to both questions is no, obviously. Your inference of my intent was wrong, meadow muffin.
|
|
|
UnintentionalChaos
International Hazard
Posts: 1454
Registered: 9-12-2006
Location: Mars
Member Is Offline
Mood: Nucleophilic
|
|
| Quote: Originally posted by JohnWW | | PbCrO4 (which occurs as the rare mineral crocoite) is, like PbSO4, only very slightly soluble, and could be used to precipitate Cr(VI) from solution.
It, and ZnCrO4 which is more soluble, is of use as an intense red paint pigment, especially in anti-corrosive roof paints and primers.
|
1) he explicitly stated that he can't use lead as a precipitant.
2) must you include a wikipedia-like rundown of useless trivia with every post?
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
I make the solution acidic, then use an alcohol or even sugar and heat to reduce most of the Cr(VI) to Cr(III). Finish off with a little bisulfite or
sulfite+extra acid, then precipitate the Cr(III) for recovery.
|
|
|
ammonium isocyanate
Hazard to Others
Posts: 124
Registered: 13-7-2009
Location: USA - Midwest
Member Is Offline
Mood: sick
|
|
Thanks for the advice, but I ended up figuring out how to dispose of it. I dissolved the ammonium dichromate in water, acidified with NaHSO4, reduced
with aluminium powder, and added KOH to make sulfate anions and precipitate the chromium (III) ions.
|
|
|
User
Hazard to Others
Posts: 339
Registered: 7-11-2008
Location: Earth
Member Is Offline
Mood: Passionate
|
|
A small question,
How should I store pure lithium metal?
I can imagine it is stored under oil as potassium/sodium would be stored.
Or would an airtight container suffice.
What a fine day for chemistry this is.
|
|
|
Phosphor-ing
Hazard to Others
Posts: 246
Registered: 31-5-2006
Location: Deep South, USA
Member Is Offline
Mood: Inquisitive
|
|
Airtight container would have to be purged of all moisture/oxygen. So under mineral oil would probably be best .
"The nine most terrifying words in the English language are: 'I'm from the government and I'm here to help.'" -Ronald Reagan
|
|
|
Sedit
International Hazard
Posts: 1939
Registered: 23-11-2008
Member Is Offline
Mood: Manic Expressive
|
|
You can't really store it under oil because it floats to the surface. In order to store it use a piece of plastic wrap stuffed in the container to
hold the Lithium Down. I have stored it for sometime this way.
~Sedit
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
|
|
|
497
National Hazard
Posts: 778
Registered: 6-10-2007
Member Is Offline
Mood: HSbF6
|
|
Is it necessary to use teflon tape to seal teflon-to-teflon normal pipe thread connections? I recently acquired a used KNF double teflon diaphragm
vacuum pump, and upon taking it apart, I found the previous owners had used teflon tape to seal the threads that hold the valve holders (don't know
what they're really called) into the main pump head.
After taking it all apart and cleaning it up I put it back together. It only pulls about 25"Hg in parallel arrangement, while the specs say it should
do at least 28". So I'm trying to figure out what the problem is..
[Edited on 30-7-2009 by 497]
|
|
|
kclo4
National Hazard
Posts: 916
Registered: 11-12-2004
Location:
Member Is Offline
Mood: No Mood
|
|
Can ice (H2O) be sublimated at -10*C to ~0*C using the vacuumed formed from an aspirator/water jet vacuum?
That is.. in any reasonable time. I'd like to sublimate a small bit (10ml at most!) in a test tube in an attempt to make some SEAgel
The reason I ask is because if it is, it seems like it would allow me to make a small amount (volume wise) of SEAgel in a test tube, which seems way
cooler then that aerogel stuff.
http://www.youtube.com/watch?v=HoCAxS4vqwQ
It is made basically by sublimated frozen water that has been gelled by agar.
[Edited on 31-7-2009 by kclo4]
|
|
|
ammonium isocyanate
Hazard to Others
Posts: 124
Registered: 13-7-2009
Location: USA - Midwest
Member Is Offline
Mood: sick
|
|
In order to subliminate ice, you need a pressure a little under 1kPa (~1/100 of an atmosphere), which sounds a little low for an aspirator vacuum. At
this pressure, ice will subliminate at a few degrees below 0*C.
|
|
|
| Pages:
1
..
9
10
11
12
13
..
30 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
