| Pages:
1
2 |
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
I use hardware store denatured alcohol for the cleaning soln.
Edit: This may or may not be cheaper than drugstore 99% isopropanol. I will check.
[Edited on 26-2-2018 by Magpie]
[Edited on 27-2-2018 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Using aluminum amalgam as a desiccant should be a lot easier. Cut some aluminum electrical wire into small rods, sufficient weight calculated to react
with all the water present in the everclear plus maybe 2 or 3 percent extra. Degrease and etch the aluminum pellets with a 10% NaOH solution then
rinse and blot dry. Drop the aluminum pellets into the everclear and add a couple of grams of mercuric chloride. The aluminum pellets will become
covered with an adherent coating of metallic mercury which attacks and dissolves the surface of the aluminum and the resulting surface amalgam is
highly reactive to oxygen, moisture, and alcohols, all being insoluble solid byproducts in this case with the alcohol being ethanol. The everclear
should be completely dehydrated simply on standing for awhile, but stirring should speed the dehydration. Pressure relief should be provided for any
free hydrogen byproduct. The weight of a solid glass stopper is sufficient as a check valve.
The dried alcohol could be distilled or simply filtered if a bit of AlCl3 is a tolerable impurity. If the amalgamation is done as advance preparation
in a separate small amount of everclear, after the aluminum pellets are well amalgamated and shiny, the everclear having slight ALCl3 byproduct and
any unreacted HgCl2 can be decanted and the "clean" amalgamated aluminum pellets used for the dehydration of the everclear.
The elemental mercury can be recovered by dissolving the residue in HCl and decanting the solution from the globules of mercury.
Absolute Ethanol should be the result of dehydration by aluminum amalgam .....meaning less than 1 ppm H2O. It might even serve well to store the
absolute ethanol over aluminum amalgam to absorb any atmospheric moisture intrusion in storage. This would be a short term reaction for the aluminum
amalgam because the aluminum would gradually react with the ethanol to form the insoluble aluminum alcoholate, Aluminum Triethanolate or Aluminum
Triethoxide, but that would react with any incoming moisture to reform ethanol and insoluble aluminum hydroxide byproduct.
The 2010 JOC article on efficiency of various desiccants I did not read so I don't know if aluminum amalgam was tested. The idea I described is purely
off the top of my head. I know aluminum amalgam is highly reactive and will even deoxygenate air as well as dehydrate the air.
[Edited on 4/5/2018 by Rosco Bodine]
|
|
|
Boffis
International Hazard
Posts: 1879
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
Can blue self-indicating silica gel be used to at least absorb some of the water from ethanol. Say to drop the water from 5% to say 1% first?
|
|
|
LearnedAmateur
National Hazard
Posts: 513
Registered: 30-3-2017
Location: Somewhere in the UK
Member Is Offline
Mood: Free Radical
|
|
Should be able to, I’m skeptical about 99% purity from a single drying run but you should be able to knock it down to a couple of percent. Just
watch for that indicator change and if you use enough ethanol, you could probably dry the silica gel and distill off the water to figure out how much
is removed.
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
|
|
|
Boffis
International Hazard
Posts: 1879
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
@LearnedAmateur, actually I was thinking that if I could drop the water content below even 2% water then I could azeotropically dry it by simply
distilling of the more volatile azeotrope and leave essential dry alcohol in the still. The distillate should approximate to the azeotrope (95%)
leaving a residue in the flask of purer alcohol which can then be dried with say 3A zeolite and finally distilled again.
|
|
|
RogueRose
International Hazard
Posts: 1596
Registered: 16-6-2014
Member Is Offline
|
|
Quote: Originally posted by Boffis  | | Can blue self-indicating silica gel be used to at least absorb some of the water from ethanol. Say to drop the water from 5% to say 1% first?
|
I found it didn't even work with 90% or 180proof. Allowed to sit (while heated to 130) for 24 hours. Same % but lost about 15% due to adhesion.
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
Why is there resistance, yet no follow-up experimentation, to prove or disprove deltaH's tripotassium phosphate hypothesis ?
All i did was throw KOH into H3PO4 to make some, and then added it to dilute ethanol and measure the result.
The result (in my experiments) was 100% ethanol, no water.
That could be +/- a few percent, yet to date, nobody has Bothered trying it, preferring to multum loqui without doing a damned thing.
What kind of Scientists are here these days ?
[Edited on 5-4-2018 by aga]
|
|
|
RogueRose
International Hazard
Posts: 1596
Registered: 16-6-2014
Member Is Offline
|
|
| Quote: Originally posted by aga | Why is there resistance, yet no follow-up experimentation, to prove or disprove deltaH's tripotassium phosphate hypothesis ?
All i did was throw NaOH into H3PO4 to make some, and then added it to dilute ethanol and measure the result.
The result (in my experiments) was 100% ethanol, no water.
That could be +/- a few percent, yet to date, nobody has Bothered trying it, preferring to multum loqui without doing a damned thing.
What kind of Scientists are here these days ? |
Are you saying that you did this with Tri Sodium Phosphate, and DeltaH was suggesting TPP? Could you point to the DeltaH post or reference? I
couldn't find a thing about anything you are talking about.
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
use Google. Search like this :
site: sciencemadness.org ethanol tripotassium phosphate delta H
First result:
http://www.sciencemadness.org/talk/viewthread.php?tid=61746&...
Edit:
Trisodium phosphate remains untested. Nobody has reported on that.
I edited the post to put KOH where i said NaOH.
If You were to try the Na3PO4 experiment, then we'd all know something new.
[Edited on 5-4-2018 by aga]
|
|
|
RogueRose
International Hazard
Posts: 1596
Registered: 16-6-2014
Member Is Offline
|
|
I see. I just figured that you were talking in reference to this thread since you posted in this thread, kind of makes sense, otherwise people
usually reference the thread they are talking about or at least mention it is a different thread.
|
|
|
RogueRose
International Hazard
Posts: 1596
Registered: 16-6-2014
Member Is Offline
|
|
Well I think TSP is an excellent suggestion to try and dry ethanol as if the Wiki is correct, it is insoluble in ethanol and the hydrate is a
dodecahydrate, which I believe is 12 water molecules, so that suggests a strong drying capacity per mole.
There is no weight per mole listed in wiki but I calculated it as follows:
Na = 23 * 3
P = 31
O = 16 *4
Anhydrous = 164g/mole
12 molecules of water = 216g so dodecahydrate = 380g/mole
So theoretically this should dry 132% of weight in water that is added to the ethanol, so every 100g added to ethanol, 132g of water should be able to
be absorbed.
I can try this but my TSP has some contaminates of Na2CO3 which shouldn't be much of an issue, it is only slightly soluble and is about 5% of the TSP.
I'm curious if mine is the hydrate or anhydrous, I'm guessing hydrate as the anhydrous would be about 2.3x the price for same amount.
|
|
|
RogueRose
International Hazard
Posts: 1596
Registered: 16-6-2014
Member Is Offline
|
|
I have 200g TSP drying now and it's being a bugger. I have it in a glass dish and it has formed a hard dry layer on top and there looks to be a
liquid/gel layer on the bottom that will just not go away even with the oven on "Toast" (both bake/broil at same time - on high). It looses water at
212 so the oven at 525 should be more than adequate at 3 hours+. That anhydrous MP is crazy high near 3000F so that layer isn't melted anhyd TSP.
There is some Na2CO3 in it but the MP is near 1500F, so it isn't that either. IDK how long this should take or a better way to do this w/o removing
and chopping it up to re-heat.
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
Yes, it does like it's water, which is what makes it so effective i guess.
A 1931 industrial process for Na3PO4 ends with .12H2O hydrate crystals, and starts with neutralising the phosphoric
acid to disodium phosphate first, mainly to remove impurities from the acid it seems, then to trisodium phosphate at the end.
Sounds like a good way to go if your acid is low grade and green like mine.
This sounds do-able, despite mentioning a 4,000 gallon tank and a 70 foot tower 
Attachment: snell1931.pdf (755kB)
This file has been downloaded 994 times
|
|
|
Boffis
International Hazard
Posts: 1879
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
@ Magpie; Is it necessary to heat the suspension of calcium oxide in the alcohol? Could I simply leave the suspension, perhaps with occasional
shaking, for a week or so and then let it settle, decant or filter of the alcohol and distill? This way I don't need the "powerful overhead stirrer"
which I don't have. Does the ethanol-calcium oxide mixture get hot when you first mix them? Isopropanol azeotrope and calcium oxide certainly do.
I tried this method with recovered isopropanol and the calcium oxide set into a concrete-like block and then I just pour off the isopropanol and
redistill it with a high reflux ratio and low distillation rate. I do this in old plastic jerry cans and just throw them away when I am done. I actual
fact I will probably not do this again for isopropanol because it is now so easy to get at 99%+ and so cheap it isn't worth it, particularly as the
azeotrope is about 30% water.
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
| Quote: Originally posted by Boffis | @ Magpie; Is it necessary to heat the suspension of calcium oxide in the alcohol? Could I simply leave the suspension, perhaps with occasional
shaking, for a week or so and then let it settle, decant or filter of the alcohol and distill? This way I don't need the "powerful overhead stirrer"
which I don't have. Does the ethanol-calcium oxide mixture get hot when you first mix them? Isopropanol azeotrope and calcium oxide certainly do.
|
I don't think this would work.
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
Boffis
International Hazard
Posts: 1879
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
@Magpie; Why not? Any actual technical reason or just a gut hunch? As I say the reaction between azeotropic isopropanol and calcim oxide is
exothermic, not as exothermic as with water but still the mixture gets hot.
What difference does the heating do apart from speed up the reaction? If its an equilibrium reaction surely low temperatures favour calcium hydroxide
though I can't see there being much difference between room temperature and 78 C making much difference.
Anyway I have set up an experiment with 500ml of rectified spirit and 81g of calcium oxide and I see how it goes.
|
|
|
Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
Member Is Offline
Mood: Chemistry: the subtle science.
|
|
The reaction between CaO and water is 2-phase. Therefore, strong mixing is important. Even with strong mixing I call for 6 hrs of mixing. Check
Vogel.
Edit: On checking Vogel I see that he does not prescribe the use of a stirrer, but refluxing only. I'm concerned that one might have severe bumping
without a mixer, however.
[Edited on 3-6-2018 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
|
|
|
walruslover69
Hazard to Others
Posts: 235
Registered: 21-12-2017
Member Is Offline
Mood: No Mood
|
|
Over the summer I have access to a piece of spectroscopy equipment that analyzes the density and specific gravity of solutions to the 0.000001 g/cm
and is used to determine compositions of binary solutions. If you guys commented or messaged me with a list of discussants you would like to test for
their drying abilities, I would love to be able to make a table with the drying properties of desiccants that everyone on the forum could reference.
should I make this project a separate thread or leave it in here?
|
|
|
| Pages:
1
2 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
