Sciencemadness Discussion Board - Absolute EtOH with aid of CaC2

Absolute EtOH with aid of CaC2

kmno4 - 18-2-2007 at 08:31

In many posts appears question of dehydrating of 90-95% ethyl alcohol. I was also interested in this matter.
I have searched among old archives of known (english) chemical databases and the only successful results was 3 articles in JSTR and 1 artice in RSC. I also searched SM posts but I found only one, without experimental details.
Calcium carbide is the cheapest dehydrating agent which may be compared with same matallic Ca. A piece of carbide, left in the air, spills into the powder [(Ca(OH)2] in few hours. Powdered CaC2 turns withe in few minutes.
Propably it is the only easy available, cheap and very effective dehydrating substance (for mad amators) for drying ethanol.
Unfortunately, I have it in 5-10 cm pices and they are as hard as rock - metal tools are needful ...

. Nevermind.
But you have to keep it in your minds - the smaller pieces, the quicker rection - powder the best. I used to use 3cm pieces of CaC2 and a lot of it remained unchanged, even if refluxed longer than 24 h... Enough of writing.
3 old articles from JSTR in attachement.

** do somebody know of what purity is industrial CaC2 ?
I assume thet it is about 85% but I really do not know

It is important detail for calculations.

[Edited on 14-1-2008 by kmno4]

[Edited on 14-1-2008 by kmno4]

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Sauron - 18-2-2007 at 08:46

I remember many texts or lab manuals recommending preliminary drying of 95-96% ethanol with CaO (quicklime)

The Ca(OH)2 that forms is insoluble.

The resulting ethanol, dry enough for some purposes, is ready for sodium treatment and distillation.

At that point the problem is not getting it dry (it's dry) but keeping it dry, at least in a humid climate. Zeolites are good for that but nothing takes the place of a fresh Na treatment and distilling the very dry ethanol into reaction flask just ahead of use.

How soluble is acetylene in ethanol? If it is soluble then with CaC2 you are making an acetylene soln albeit a dilte one.

joeflsts - 18-2-2007 at 08:47

I'm not sure how much this helps but typical industrial grade CaC2 tends to have the following characteristics:

Procreant gas (20 degree, 101. 3kpa) (L / KG >=) :
1) Superfine: 300
2) First Class: 280
3) Up to grade: 260
Volume% phosphine (% <=) :
1) Superfine: 0. 06
2) First Class: 0. 08
3) Up to grade: 0. 08
Volume% of sulfurated hydrogen (% <=) :
1) Superfine: 0. 10
2) First Class: 0. 10
3) Up to grade: 0. 10
Quality percentage of granularity (5mm-80mm) (% >=) :
1) Superfine: 85
2) First Class: 85
3) Up to grade: 85
Quality percentage of filtrated goods (25mm below) (% <=) :
1) Superfine: 5
2) First Class: 5
3) Up to grade: 5
Packing: 50 + --1kg, 100 + --1kg or 200 + --1kg iron drum with Nz gas
Payment Item: L/ C or T/ T
Deliever days is: 7-10 days after confirm the L/ C.

copied from:
http://www.alibaba.com/catalog/11781349/Calcium_Carbide.html

kmno4 - 18-2-2007 at 09:00

Quote:

Originally posted by Sauron
I remember many texts or lab manuals recommending preliminary drying of 95-96% ethanol with CaO (quicklime)

The Ca(OH)2 that forms is insoluble.

The resulting ethanol, dry enough for some purposes, is ready for sodium treatment and distillation.

At that point the problem is not getting it dry (it's dry) but keeping it dry, at least in a humid climate. Zeolites are good for that but nothing takes the place of a fresh Na treatment and distilling the very dry ethanol into reaction flask just ahead of use.

How soluble is acetylene in ethanol? If it is soluble then with CaC2 you are making an acetylene soln albeit a dilte one.

As was many times posted - matallic Na is not enough.
I have dried 95% ethanol with AcOEt/Na - very quick hydrolise reaction, leves only AcONa and ethanol... but Na is much expensive than CaC2 .... and if ~90% EtOH is used, there is problem with distilling out EtOH from large amout of sodium acetate.

Sauron - 18-2-2007 at 09:30

I an usually drying commercial absolute ethanol as it is easy to buy here. 95% ethanol they sell here as Special Solvent #so and so.denatured with misc other crap so it is not very useful for anything serious. 90% is pretty wet.

When I was making liquor I used to distill ethanol (potable) out of brandy. Cheap brandy to be sure! But that is neither here nor there.

If I need 95% ethanol without the complications of denaturants in it I must add water to the absolute AR grade.

Sauron - 18-2-2007 at 21:16

So, commercial CaC2 also contains calcium phosphide. Therefore,using it to destroy water in ethanol will generate acetylene and a little phosphine and diphosphine.

Ugh. You'd have to offgas the ethanol at the pump vented out a hood. Correct?

kmno4 - 20-2-2007 at 10:19

Eeeeeeee,
You really should read these articles I gave.
I have impression that you do not know what is the purpose of > > 99,5% ethanol. In my country cheap anhydrous EtOH is available only for universities (for professors too, they like this substance), for manufacturing drugs etc. Cheap is only denaturated alcohol ~90% and ~95% spiritus smuggled from "cheaper" countries

. Given methode allows to prepare 99+% EtOH with yield better than 90% with the cheapest available substances. If Ca would be cheap, then using CaC2 would be just a pure stupidity, of course. C2H2+stink = needed hood -> nothing for free.

Sauron - 20-2-2007 at 18:03

No problem. It seems that everywhere, you win some, you lose some. Some things are easy to get, others hard, cross an invisible line on the map and everything shifts around.

Here the production of ethanol is a Crown monopoly licensed to the highest bidder, they ferment tapioca and glutinous rice. But the anhydrous reagent grade that I buy is imported. I thnk it is Merck. So I likely pay a premium for it.