Sciencemadness Discussion Board

Neutralization of Vinegar with KOH

Romix - 18-8-2023 at 18:51

Dissolved half a can out of mayonnaise with insoluble in water plant ash in 2 500ml bottles of 10% vinegar.
PH still neutral, will filter it soon when it'll stop fizzing.
Ok the question is how much KOH I need to add to neutralize all the Acetates in solution??
Knowing that 1ml of Glacial Acetic acid weighs 1.5 grams.
How to work it out?

j_sum1 - 18-8-2023 at 18:56

Add KOH solution slowly.
Use pH paper
Stop when neutral.

Romix - 18-8-2023 at 19:07

Quote: Originally posted by j_sum1  
Add KOH solution slowly.
Use pH paper
Stop when neutral.

PH is neutral right now.

j_sum1 - 18-8-2023 at 19:39

Ash solution contains K2CO3.
Vinegar contains acetic acid.
Not sure what the mayonnaise is for.

You have a weak acid and weak base and the salts from the neutralisation reaction. Seems like you have created yourself a buffer solution. It will take quite a bit of strong acid or strong base to shift it.

If you want a neutral solution, I am not at all sure what your problem is.

Romix - 18-8-2023 at 19:47

Quote: Originally posted by j_sum1  
Ash solution contains K2CO3.
Vinegar contains acetic acid.
Not sure what the mayonnaise is for.

You have a weak acid and weak base and the salts from the neutralisation reaction. Seems like you have created yourself a buffer solution. It will take quite a bit of strong acid or strong base to shift it.

If you want a neutral solution, I am not at all sure what your problem is.

I meant that insoluble in water plant ash were stored in a can out of mayonnaise...

Romix - 18-8-2023 at 19:48

And I've used half a can of ash.

j_sum1 - 18-8-2023 at 20:21

Well, assuming your ash is pure potassium carbonate (which is a really dumb assumption but anyway)
You will have a mixture containing potassium ions, carbonate/bicarbonate ions (depending on the pH), acetate ions and dissolved CO2.

You can get rid of most of the CO2 by boiling it for a while.
Actual pH will depend on the exact proportions (which you don't know). You have a couple of different acid-base equilibrium reactions going on so it will be a dog of a thing to calculate anyway. Potassium acetate is a basic salt. But then you have other impurities.

If you want to put it on your garden, leave it for a long time to expel the CO2 and reach equilibrium. Then test pH and see if it is in the range you want for your garden.

If you want to do more than that then there are a number of good YT videos of qualitative tests that you can do on wood ash to determine ions present. But nothing much quantitative is within the reach of the amateur chemist.

DraconicAcid - 18-8-2023 at 20:33

It's neutral, and you want to make it more neutral? Come back when you know what you're talking about.

Romix - 18-8-2023 at 21:02

Chucked KOH in solution of Acetates until basic PH like 6 teaspoons.
A lot of white hydroxides precipitated. That is pain in the ass to filter.

Romix - 19-8-2023 at 01:42

Quote: Originally posted by DraconicAcid  
It's neutral, and you want to make it more neutral? Come back when you know what you're talking about.

My PH papers not turning red on diluted acetic acid!
Will make it basic with K2CO3, KOH doesn't work every thing dissolves in it's excess!!

Romix - 20-8-2023 at 07:51

Hydroxides that dissolved in excess KOH, dropped with K2CO3.

366390097_2586281208202747_4351141431529211708_n.jpg - 236kB
368574413_258763380292988_1719943926706341684_n.jpg - 193kB


[Edited on 20-8-2023 by Romix]

Romix - 20-8-2023 at 09:08

What cation it could be??
Obtained from insoluble in water plant ash dissolved in vinegar and precipitated with K2CO3.
It dissolves in excess KOH.
Hydroxides and Carbonates of which are both white.

Romix - 20-8-2023 at 09:09

Hydroxides that didn't dissolve in excess KOH were white too, but turning grey standing on air drying.

Rainwater - 20-8-2023 at 12:57

https://www.sigmaaldrich.com/US/en/technical-documents/techn...
Scroll down until you see the table.
From your starting material these cations are likly to disolive in vinegar and percipitate carbonates on the addition of K2CO3
Mg
Ca
Br
Fe

Iron can be ruled out because of the color of your percipitate
Barium will be in trace amounts

Edit:
A flame test will help determine the cation.
Magnesium will be white
Calcium an orange red

[Edited on 20-8-2023 by Rainwater]

B(a)P - 20-8-2023 at 13:06

Quote: Originally posted by Rainwater  

Mg
Ca
Br
Fe

Iron can be ruled out because of the color of your percipitate
Barium will be in trace amounts


Slight typo, should be Ba. Surely there would not be meaningful quantities of barium in wood ash?

Romix - 20-8-2023 at 13:48

Thinking about getting Spectrometer, to ID cations in plant ash, one day I've seen 2 of them selling on ebay under 20£ on auction. There's few there now, but buy now and very very expensive, will wait for a better deal!

Romix - 20-8-2023 at 13:50

Checking if Mg(OH)2 precipitated with KOH out of pure MgSO4·7H2O will dissolve in excess of KOH.
Also will give a go crystalizing K2SO4.

Romix - 20-8-2023 at 13:55

Quote: Originally posted by Rainwater  
https://www.sigmaaldrich.com/US/en/technical-documents/techn...
Scroll down until you see the table.
From your starting material these cations are likly to disolive in vinegar and percipitate carbonates on the addition of K2CO3
Mg
Ca
Br
Fe

Iron can be ruled out because of the color of your percipitate
Barium will be in trace amounts

Edit:
A flame test will help determine the cation.
Magnesium will be white
Calcium an orange red

[Edited on 20-8-2023 by Rainwater]

Thank you for advice. Flame testing them is a good idea, didn't knew about the difference. Will do that tomorrow, it's too dark now. Do I need to dissolve a sample for a flame test or can use hydroxides and carbonates as they are.

[Edited on 20-8-2023 by Romix]

Rainwater - 20-8-2023 at 14:06

Quote: Originally posted by B(a)P  

Slight typo, should be Ba. Surely there would not be meaningful quantities of barium in wood ash?

Correct, peer review proved itself again.

barium hydroxide as a very effective pesticide against kudzu and it is a common mineral where I live, the largest barium mine is my state is about 30 minutes from here.
It shows up in well water and soil test. Some countys require private wells to be tested biannualy, and a consentration over 1.5ppm will close your well.

Edit:
disoliveing some in HCl solution, then apply to a stick and dry, and repeat to build up a thick layer of salt. Add a few drops of methanol/ethanol. And apply a flame.


[Edited on 20-8-2023 by Rainwater]

B(a)P - 20-8-2023 at 14:27

Quote: Originally posted by Rainwater  
Quote: Originally posted by B(a)P  

Slight typo, should be Ba. Surely there would not be meaningful quantities of barium in wood ash?

Correct, peer review proved itself again.

barium hydroxide as a very effective pesticide against kudzu and it is a common mineral where I live, the largest barium mine is my state is about 30 minutes from here.
It shows up in well water and soil test. Some countys require private wells to be tested biannualy, and a consentration over 1.5ppm will close your well.


Interesting stuff! The mineralisation of local areas can be really fascinating. Very off topic, some time ago I was part of a team that designed and constructed a new training facility in a remote part of North Queensland. A water supply was required, but the granite in the area contained fine grained disseminated pitchblende and the concentrations of uranium in the water made it non-potable, so we ended up installing an RO plant and a little solar farm to support it.
Nice idea on the flame test, given it is a mix though will it give a meaningful result? I guess at least it will be a reasonable presence absence test for elements that tend to be dominant in flame tests.

Romix - 20-8-2023 at 14:46

Flame testing is very difficult, just tried testing K2SO4 in solution, it didn't change flame color, same for burning sample of Mg(OH)2.

Rainwater - 20-8-2023 at 14:49

Im stupid. Completely forgot about this.
You can selectively percipitate calcium using sulfuric acid (or equivalent)

Romix - 20-8-2023 at 14:56

Quote: Originally posted by Rainwater  
Im stupid. Completely forgot about this.
You can selectively percipitate calcium using sulfuric acid (or equivalent)

Barium too...

B(a)P - 20-8-2023 at 15:21

Quote: Originally posted by Romix  
Quote: Originally posted by Rainwater  
Im stupid. Completely forgot about this.
You can selectively percipitate calcium using sulfuric acid (or equivalent)

Barium too...


Yes, but unless you live up the road from Rainwater you will not have any barium.

Romix - 20-8-2023 at 15:57

No, not Calcium!
Cation that dissolved in excess KOH, and dropped with K2CO3 after acidification with vinegar.
Added K2SO4 to a sample dissolved in vinegar. No precipitate forming!

Romix - 22-8-2023 at 16:32

Quote: Originally posted by Rainwater  
Quote: Originally posted by B(a)P  

disoliveing some in HCl solution, then apply to a stick and dry, and repeat to build up a thick layer of salt. Add a few drops of methanol/ethanol. And apply a flame.
[Edited on 20-8-2023 by Rainwater]


Thank you for advice, I'll try that tomorrow, when it will get lighter.
Yes, I can see that most people on YouTube doing flame tests with chloride salts, I have a little bit of HCl left from my previous experiments about Gold Recovery, and both hydroxides (probably not just OH− any more, that is why they turned grey, a lot of gas been produced by dissolving insoluble in water plant ash in 10% vinegar and I think some of the gas been absorbed by the hydroxides in solution, like for example wet Ca(OH)₂ do standing on air. And Carbonates are well washed from other soluble salts in them.



[Edited on 23-8-2023 by Romix]

Romix - 22-8-2023 at 16:40

Already told you that my PH papers don't turn red on diluted Acetic Acid and fizzing from stirring ash in solution not a good indicator, because solution is full of CO2 gas like any mineral water in a shops with bubbles, and that's what is fizzing when you stir it or shake it, gas!

[Edited on 23-8-2023 by Romix]