Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: 58% EtOH + NaOH = .....
Sulaiman
International Hazard
*****




Posts: 3059
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 2-8-2018 at 04:58
58% EtOH + NaOH = .....


I have a small beaker which has what looks like a transparent crystaline deposit over the lower 1/3.
I have tried many cleaning solutions and mechanical scrubbing... little change.
So I decided to try a base bath (first time).
I have read here on this forum of hydroxide plus either ethanol or water.
I decided to use some of my 58% ethanol stock with drain cleaner grade NaOH.

Within a minute of mixing NaOH into the dilute ethanol,
the liquid split into two phases,
the lower smaller portion was colourless, the upper layer was a transparent clear light yellow colour.

The grade of NaOH drain cleaner that I have is quite good,
when dissolved in H2O it forms a totally colourless transparent solution,
the EtOH is distilled from glucose + yeast and is colourless transparent.

The volumes of colourless : yellow portions looks close to 42:58

Both portions make pH 1-14 paper indicate max. alkalinity.

The two phases are now in separate beakers.



What is the yellow due to ?
View user's profile View All Posts By User
CobaltChloride
Hazard to Others
***




Posts: 239
Registered: 3-3-2018
Location: Romania
Member Is Offline


[*] posted on 2-8-2018 at 05:07


Generally, alcoholic solutions of strong base turn yellow because trace amounts of aldehyde form due to the oxidation of alcohol by oxygen in the air. In the presence of base, the aldehydes undergo a number of reactions, among them being polymerization. The traces of polymerized acetaldehyde make solutions of NaOH in EtOH look slightly yellow
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 3059
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 2-8-2018 at 06:06


Thanks.

Now considering making some dry aldehyde-free ethanol ....
View user's profile View All Posts By User
walruslover69
Hazard to Others
***




Posts: 183
Registered: 21-12-2017
Member Is Offline

Mood: No Mood

[*] posted on 2-8-2018 at 08:32


If you store it under molecular sieves they will polymerize aldehydes and dry. The polymerization is probably much much slower though.
View user's profile View All Posts By User
DJF90
International Hazard
*****




Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline

Mood: No Mood

[*] posted on 2-8-2018 at 09:06


I'm more surprised by the phase separation... I was under the impression that this would form a homogeneous solution. Could it be that your alcohol contains fusel oils (higher alcolhols) which encourages the ethanol to separate from the aqueous caustic?
View user's profile View All Posts By User
walruslover69
Hazard to Others
***




Posts: 183
Registered: 21-12-2017
Member Is Offline

Mood: No Mood

[*] posted on 2-8-2018 at 09:12


NaoH does a pretty efficient job at separating polar and semi polar solvents like water and alcohols. I have used it before to separate water/IPA
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 3059
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 2-8-2018 at 11:32


Quote: Originally posted by DJF90  
I'm more surprised by the phase separation... I was under the impression that this would form a homogeneous solution. Could it be that your alcohol contains fusel oils (higher alcolhols) which encourages the ethanol to separate from the aqueous caustic?


I was astonished by how quickly and cleanly the phases seperated,
and rapidly re-separate after vigorous stirring,
(looks like oil on water)
two completely clear, separate phases, easily separated using a pipette.
(except the last mixed drop)

I mis-typed earlier ... I should have wrote sucrose & some glucose, plus yeast & nutrients.
The 58% EtOH has been distilled and diluted a couple of times during the testing of my still,
It should contain most of the fractions of b.p. less or equal to EtOH/water ... it still smells like more than just EtOH.
View user's profile View All Posts By User
happyfooddance
International Hazard
*****




Posts: 521
Registered: 9-11-2017
Location: Los Angeles, Ca.
Member Is Offline

Mood: No Mood

[*] posted on 2-8-2018 at 11:40


Quote: Originally posted by DJF90  
I'm more surprised by the phase separation... I was under the impression that this would form a homogeneous solution.


Me too.

Quote: Originally posted by walruslover69  
NaoH does a pretty efficient job at separating polar and semi polar solvents like water and alcohols. I have used it before to separate water/IPA


But this is ethanol, not IPA, I use ethanol with NaOH quite a bit and I have never once seen phase separation. K2CO3 will initiate phase separation, however.
Quote: Originally posted by Sulaiman  
Thanks.

Now considering making some dry aldehyde-free ethanol ....


Two ways to remove acetaldehyde: place your ethanol in an open flask, and bubble air through it for a day or so, and/or: pull a vacuum (with stirring and pump running) for about half an hour to 45 minutes.

I believe you mentioned in another thread that you take your wash up to 12%, correct? Keeping it under 10% (I do 9%), as well as keeping fermentation temp under 30°C does a lot to keep acetaldehyde (and fusel) production at a minimum.

12% is where acetaldehyde starts to become an inconvenience (for me).

My 2 cents.

Edit: You might want to test your drain cleaner for potassium. Flame test, maybe?

[Edited on 8-2-2018 by happyfooddance]
View user's profile View All Posts By User
Sulaiman
International Hazard
*****




Posts: 3059
Registered: 8-2-2015
Location: UK ... on extended Holiday in Malaysia
Member Is Offline


[*] posted on 2-8-2018 at 12:12


Good info ... thanks.

In this case the ethanol is purely to test my fractionating still,
so many normally 'unwanted' fractions are actually welcome.
But I will try another couple of fermentations at different wash concentrations when (if ever) I am happy with my still.
The 58% EtOH consists of combined batches and re-distilled and combined fractions.
The target wash concentrations were 21%, 20.5% and the largest batch was 17%.
Not very scientific I'm afraid.

I had a taste-test guinea pig who informed me that earlier fractions tasted f@@king awful, the current 58% just tastes foul.

Not much chance seeing a little K with a lot of Na present in the flame :D
I will try with my 99% NaOH and look for any difference,
I'll also probably try using KOH, but that is more expensive.

[Edited on 2-8-2018 by Sulaiman]
View user's profile View All Posts By User
DavidJR
International Hazard
*****




Posts: 908
Registered: 1-1-2018
Location: Scotland
Member Is Offline

Mood: Tired

[*] posted on 2-8-2018 at 13:24


What makes a remarkable difference in the level of fusels is simply if you allow the wash to completely settle and become water clear before distilling. I add a small amount of potassium aluminium sulphate (maybe 1 gram per litre, not critical) which acts as a flocculant and helps the yeast and whatnot settle out quickly. You'll need to allow it to settle, gently draw off the liquid into a clean container, and repeat until it's water clear.

It seems that a lot of the impurities are contained in/bound to (?) the yeast particles in suspension and will be released upon distillation.


Also, once i've stripped the wash (I use my 4 litre water distiller and run until the vapour temp is about 97C) I add a little bit of activated carbon, shake it up, sit for a while and then vacuum filter (using a diatomaceous earth-based filter aid, e.g. celite, celatom,...) which helps.





View user's profile View All Posts By User

  Go To Top