bob800
Hazard to Others
Posts: 240
Registered: 28-7-2010
Member Is Offline
Mood: No Mood
|
|
Evaporating a liquid in desiccator bag
I found a really simple procedure for making copper(II) acetate by woelen: Quote: Originally posted by woelen  |
- Add excess 30% acetic acid to the black material and let it stand in an open vessel for many many days until it has become perfectly dry. Everything
will smell of vinegar when you do this inside, so it is best to put the vessel outside in a warm and dry place where animals and children cannot
access it. When the acetic acid is added, the liquid becomes really dark green and black material seems not to dissolve at once, but while it is
standing, slowly all of it is converted to copper(II)acetate. It is important though to have excess acetic acid. |
However, it's really cold outside here, so evaporating outside won't do anything. Having watched a NurdRage video on making a desiccator bag(http://www.youtube.com/watch?v=XJFfS_YbbYI&feature=playe...), I thought I could make one and use NaOH to dry out the air and additionally
dissolve the pungent acetic acid fumes.
However, at the end NurdRage says, "This desiccator only works on solids, it does not work on liquids and cannot be used for concentrating acids,
peroxide or drying alcohols."
Why won't this work for liquids? Is there any other option for evaporating inside, without filling the whole house with vinegar fumes?
Any help would be very appreciated! Thanks!
|
|
|
Magic Muzzlet
Hazard to Others
Posts: 146
Registered: 22-7-2010
Member Is Offline
Mood: No Mood
|
|
You can use the bag to dry your copper acetate.
|
|
|
woelen
Super Administrator
Posts: 8014
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
The simplest option is to wait for summer 
A somewhat less simple option is to use a plastic tub which can be closed air-tight very well and put the liquid and a fairly large amount of NaOH in
it and just allow it to stand for some time in a warm place. You probably, however, will need quite some NaOH. You could evaporate some of the liquid
by heating, but then you run the risk of hydrolysing part of the acetate to the oxide and/or hydroxide and you run the risk of getting an impure
product which is not nicely crystalline.
Patience is your best friend in this particular case 
[Edited on 11-2-11 by woelen]
|
|
|
bob800
Hazard to Others
Posts: 240
Registered: 28-7-2010
Member Is Offline
Mood: No Mood
|
|
Perhaps I'll have to do that.
Thanks for the quick replies. I'll try the NaOH method, but if it ends up requiring tons of it, I'll put it away until summer.
|
|
|
DougTheMapper
Hazard to Others
Posts: 145
Registered: 20-7-2008
Location: Michigan, USA
Member Is Offline
Mood: Energetic
|
|
I've had good experiences with anhydrous magnesium sulfate.
Get epsom salts at the store and spread the crystals on a cookie sheet. Bake them in the oven as high as the temperature will go. The crystals will
first swell and then steam as the heptahydrate is dehydrated. It doesn't small as long as the crystals weren't dusty.
Let cool with as little exposure to air as possible. (Leave it in the oven) You will need a hammer or something of that magnitude to release the
stuck-on MgSO4 from the cookie sheet.
Place the product in an airtight container. It works wonders as a desiccant.
Victor Grignard is a methylated spirit.
|
|
|
entropy51
Gone, but not forgotten
Posts: 1612
Registered: 30-5-2009
Member Is Offline
Mood: Fissile
|
|
| Quote: Originally posted by DougTheMapper | I've had good experiences with anhydrous magnesium sulfate.
Get epsom salts at the store and spread the crystals on a cookie sheet. Bake them in the oven as high as the temperature will go. The crystals will
first swell and then steam as the heptahydrate is dehydrated. It doesn't small as long as the crystals weren't dusty.
Let cool with as little exposure to air as possible. (Leave it in the oven) You will need a hammer or something of that magnitude to release the
stuck-on MgSO4 from the cookie sheet.
Place the product in an airtight container. It works wonders as a desiccant. |
Sigh. If you put the MgSO4 in
a warm oven and slowly raise the temperature of the oven, the salt will dehydrate without melting in its water of crystallization. You will
end up with a dry powder. No hammer needed.
But MgSO4 is a good dissicant for drying organic liquids, not for filling a dessicator and trying to evaporate liquids.
|
|
|
ldanielrosa
Hazard to Others
Posts: 124
Registered: 25-4-2007
Member Is Offline
Mood: transparent
|
|
I don't know if this helps, but when I want to evaporate liquids I put 'em in a jar and let it fester for a while in a crock-pot with a sand bath.
|
|
|
annaandherdad
Hazard to Others
Posts: 387
Registered: 17-9-2011
Member Is Offline
Mood: No Mood
|
|
desiccating with NaOH
| Quote: Originally posted by bob800 |
Perhaps I'll have to do that.
Thanks for the quick replies. I'll try the NaOH method, but if it ends up requiring tons of it, I'll put it away until summer. |
I've been desiccating silver nitrate (in solution with some HNO3) using NaOH. The weather here is cool, but it's still working pretty well. I'm
using a Rubber Maid plastic container (which unfortunately are rather expensive, but maybe you can find one in a second-hand store). The top seals on
pretty well. As for the NaOH, I'm using drain cleaner (not Drano, which has aluminum in it) that I bought in the hardware store. It's pretty cheap.
Of course it doesn't have to be high quality, it just has to absorb the water and acid vapors.
I found that increasing the area of the evaporating liquid has a bigger impact on the rate of drying than does increasing the area of NaOH. So I've
ended up with maybe 4 petri dishes of liquid evaporating, plus one container of NaOH, in a single Rubber Maid container.
I learned the hard way not to use a metal container for the NaOH. The problem is not the NaOH, it's the acid vapors that attack the metal. I
switched to a plastic tub (originally used for margarine) and that works better.
I have taken to opening the container every 2 days and weighing the petri dishes to measure the rate of evaporation. The weather here is cool, but I
can get up to 10 grams of liquid evaporated per day with my setup. It still takes patience, but it works.
The NaOH gets runny after a while. I've just poured off the liquid and put the rest back in, supplementing the NaOH when there's not much left. I
read on another thread that someone mixed his NaOH with CaO to absorb the water, with good results. I haven't tried that yet.
I'd use CaCl2 if I didn't have the acid vapors to get rid of. I don't know which has the higher affinity for water, NaOH or CaCl2, but I'm
considering a final, extra drying step at the end with fresh (and completely dry) NaOH or CaCl2.
It's been interesting, and I'm thinking of just doing some crystallization for fun of different salts, after I'm done with the AgNO3. My daughter
likes to see colored crystals.
One more thing. Both the cheap drain cleaner I bought at the hardware store and the lab quality stuff I bought from a chemical supply place, come in
small pellets in a plastic container. When I first open the container, the pellets are so dry that they are all charged with static electricity and
clinging all over the sides of the container and the lid. When I try to scoop out a spoonful (with a plastic spoon), the static electricity makes the
little pellets jump all over the place, onto my hands and onto the table. Very annoying, especially for NaOH.
However, within a minute or two, the NaOH evidently absorbs enough water from the air to make an electrical conductor, and the static electric effects
disappear.
I'd prefer it if they just gave me larger lumps of NaOH so I wouldn't have this problem in the first place.
Any other SF Bay chemists?
|
|
|
Arthur Dent
National Hazard
Posts: 553
Registered: 22-10-2010
Member Is Offline
Mood: entropic
|
|
Well definitely the good ol trick of a large ziploc seal bag in which you put a dollar-store damp-trap filled with CaCl<sub>2</sub> is the
most efficient and inexpensive: Damp Trap @ $1.25 and Ziploc bag @ $.25, total cost a buck and a half. I've succesfully dessicated various chloride
solutions, and even got some solid FeCl<sub>3</sub> hydrate out of a concentrated solution.
For more serious dessicating, I use the contents of one of those Damp Traps in my Pyrex vacuum Dessicator with some vacuum (as much as my little
plastic aspirator can muster). Does the job very well, see this thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=17364#...
Manganese Chloride crystals from what was originally a fairly dilute solution.
Robert
--- Art is making something out of nothing and selling it. - Frank Zappa ---
|
|
|
Chemistry Alchemist
Hazard to Others
Posts: 403
Registered: 2-8-2011
Location: Australia
Member Is Offline
Mood: No Mood
|
|
would it be warmer inside then out side? normally i leave my liquids in the laundry (gets warm in there sometimes compared to out side or around the
house) so i place it ontop of one of those dryers which arnt in use... heat rises to teh sealing, my liquids are about 1 m away from the sealing so
after about a week or so i can grow very nice large crystals.... really good way to get nice pure crystals instead of boiling it or rushing drying
|
|
|
theflickkk
Harmless
Posts: 33
Registered: 29-3-2011
Member Is Offline
Mood: No Mood
|
|
Maybe you could try boiling down the solution, until a thin crust of copper acetate starts to form,
before letting it cool and evaporating it? I've tried it and it worked well in my opinion. This method gives
many tiny crystals instead of a couple of big ones though.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
