Sciencemadness Discussion Board

Sodium Sulfate from Aluminum Sulfate

AlphaDecay - 13-7-2014 at 16:32

Has anyone tried this synthesis? It uses only easy acquiring chemicals:
3Na2CO3 + Al2(SO4)3 -> 3Na2SO4 + Al2(CO3)3
Aluminum carbonate would precipitate, leaving sodium sulfate in solution, but I also found out that Aluminum Carbonate decomposes to carbon dioxide and aluminum hydroxide in water. Is it right? Any tips?
(Please do not tell me to buy the sodium sulfate, I want to synthesize it)
[Sorry for english mistakes]

DraconicAcid - 13-7-2014 at 19:25

You won't get aluminum carbonate, you'll get aluminum hydroxide and carbon dioxide. But the sodium sulphate should still form.

AlphaDecay - 14-7-2014 at 07:44

Yes, I actually need only the sodium sulfate, Al(OH)3 will be a by-broduct...

Justin Blaise - 16-7-2014 at 08:11

Filtering Al(OH)3 might prove difficult, as it tends to be gelatinous. If you have sodium carbonate, why not react it with some sulfuric acid?

Amos - 16-7-2014 at 09:31

At pharmacies and grocery stores you can buy Epsom Salts (magnesium sulfate heptahydrate, it's ludicrously cheap) in pretty large quantities. By reacting solutions of magnesium sulfate and sodium carbonate, with a definite excess of sodium carbonate, you can precipitate magnesium carbonate and be left with a solution of sodium sulfate that contains just a bit of sodium carbonate. Neutralize the excess carbonate with some dilute sulfuric acid(battery electrolyte works fine), and you can evaporate the solution to grow pure crystals of sodium sulfate.

AlphaDecay - 25-7-2014 at 11:07

Quote: Originally posted by Justin Blaise  
Filtering Al(OH)3 might prove difficult, as it tends to be gelatinous. If you have sodium carbonate, why not react it with some sulfuric acid?

Well, here where I live concentrated H2SO4 is pretty hard to acquire and it is expensive too, so I searched for readily available chemicals to make Na2SO4.
Actually isn't this the chemical reaction [Na2CO3 + Al2(SO4)3] that happens in pools to decant solid particles?

AlphaDecay - 25-7-2014 at 11:09

Quote: Originally posted by No Tears Only Dreams Now  
At pharmacies and grocery stores you can buy Epsom Salts (magnesium sulfate heptahydrate, it's ludicrously cheap) in pretty large quantities. By reacting solutions of magnesium sulfate and sodium carbonate, with a definite excess of sodium carbonate, you can precipitate magnesium carbonate and be left with a solution of sodium sulfate that contains just a bit of sodium carbonate. Neutralize the excess carbonate with some dilute sulfuric acid(battery electrolyte works fine), and you can evaporate the solution to grow pure crystals of sodium sulfate.

I may try that someday, thanks for suggestion.

Artemus Gordon - 25-7-2014 at 12:27

Quote: Originally posted by AlphaDecay  
Has anyone tried this synthesis? It uses only easy acquiring chemicals:
3Na2CO3 + Al2(SO4)3 -> 3Na2SO4 + Al2(CO3)3
Aluminum carbonate would precipitate, leaving sodium sulfate in solution, but I also found out that Aluminum Carbonate decomposes to carbon dioxide and aluminum hydroxide in water. Is it right? Any tips?

(Please do not tell me to buy the sodium sulfate, I want to synthesize it)
<b>Artemus Gordon here: I'm glad nobody did tell AlphaDecay to go buy some, but the fact that AlphaDecay has to say this reflects badly on this forum. Don't do this, people!</b>

[Sorry for english mistakes]

aga - 25-7-2014 at 13:40

Highly confused by that remark Artemus. What do you mean ?

All i can add is that Aluminium Hydroxide is a real PITA to deal with, so best avoided.

AlphaDecay - 26-7-2014 at 17:12

I didn't understand that also, and what is the thing with Al(OH)3?
Perhaps I am missing something, and I would like to know what is it...

[Edited on 27-7-2014 by AlphaDecay]

TheChemiKid - 26-7-2014 at 17:19

Aluminum hydroxide traps huge amounts of water in it forming a gelatinous mass that takes forever to filter. Even then, huge amounts of water (and your product) are trapped in the Al(OH)3.

AlphaDecay - 26-7-2014 at 17:24

Oh, I see. Okay then, I will be trying something else...

TheChemiKid - 26-7-2014 at 17:27

Good idea. I recommend the epsom salts (MgSO4) method or mixing ammonium sulfate (if you can get it as a fertilizer) and sodium hydroxide, carbonate, or bicarbonate (whatever is easiest to get).

AlphaDecay - 26-7-2014 at 17:48

Nice! Ammonium sulfate is easy to get. Reacting it with Sodium Carbonate would produce Ammonium carbonate, or ammonia and carbon dioxide? Or even (NH4)2CO3 would decompose to ammonium bicarbonate and ammonia? Any suggestion is well accepted.

TheChemiKid - 26-7-2014 at 17:55

It would decompose to ammonia, water, and carbon dioxide.
If sodium bicarbonate is used, it will produce the same chemicals, but there would be more water and carbon dioxide, and the same amount of ammonia.
If sodium hydroxide is used, it will only produce ammonia and water.

AlphaDecay - 26-7-2014 at 17:58

I see. But now I've gotten 2kg Al2(SO4)3, any interesting uses for it?

TheChemiKid - 26-7-2014 at 18:02

You could:
Make double salts, specifically alum.
Make other aluminum sulfate.
Decompose it first to form water, then sulfur trioxide.

AlphaDecay - 13-8-2014 at 11:33

I mixed the two chemicals(Na2CO3 and [NH4]2SO4) and I didn't see any gas driving off the solution, also no smell of ammonia gas... I think I'm gonna try the reaction with Calcium Sulfate, the by-product, CaCO3 is less soluble than CaSO4.

Johnny Cappone - 7-4-2021 at 04:30

What if, instead of carbonate, we used sodium chloride?

I am in need of Na2SO4, and although dilute sulfuric acid and caustic soda are available reagents for me, aluminum sulfate (reasonably pure, I suppose) is also available as a flocculant to treat pool water. A package with 2kg of Al2(SO4)3 would cost me only 3.60 USD.
Given the characteristic solubility curve of sodium sulfate, I believe that it could be crystallized without major difficulties simply by cooling the solution. AlCl3 would continue to be dissolved and could also be recovered later (any interesting use for hydrated aluminum chloride?) My concern lies in the possibility that some sodium alum (NaAl(SO4)2ยท12H2O) is formed.
Therefore, I would like to hear a second opinion on this approach.

njl - 7-4-2021 at 04:49

It would really be best to have one product be insoluble. The leftover aluminum trichloride hydrate isn't very useful except for preparing other aluminum salts.

unionised - 7-4-2021 at 09:24

If you powder and dry the sodium carbonate in air for a while until it stops losing weight then you will have pretty pure Na2CO3. H2O with a molar mass of 124 and probably better than 95% pure
And the Epsom salts (molar mass 246.47 g) on sale will also be better than 95% pure. (Much better if it's pharmaceutical grade).

So, if you weigh out the correct ratio of the materials you will end up with a suspension of magnesium carbonate and a solution of sodium sulphate which should also be better than 95% or so pure.
You can then filter that liquid and evaporate the water to give crystalline sodium sulphate.

That's possibly good enough for your purpose but, if it isn't then it's a simple enough matter to recrystalise it.

On the other hand, filtering solutions containing Al(OH)3 is very frustrating.

rockyit98 - 7-4-2021 at 23:58

NaHSO4 can be found in pool chemical shops along with Na2CO3, the rest is no brainer.