Sodium Carbonate crystals in cold water

[Erina]

I use Bicarbonate of Soda (NaHCO₃) in my washing machine for my clothes as an alternative to commercially available washing powders. Whilst living in London and thus in a "hard water" region I read that converting NaHCO₃ into Sodium Carbonate (Na₂CO₃) would dissolve better in "hard water", but I have since come to find that all it does is collect and crystalise on contact with <30ºC temperature (i.e. cold) water.

The Crystals can be coaxed back into mixing with water if the water is heated up (I usually wash my clothes on a 40ºC cycle anyway), but wanted to know why they crystalise?

nb. I convert my NaHCO₃ -> Na₂CO₃ in the oven at 230ºC for 1hr.

 

 

[studiot]

7 minutes ago, Erina said:

nb. I convert my NaHCO₃ -> Na₂CO₃ in the oven at 230ºC for 1hr.

Surely it would be cheaper to buy ordinary wahing powder/liquid/balls than to run you oven for an hour?

[Erina]

I use the single compound to avoid all the other stuff in normal washing powder. However, I did work out the cost and it's about the same:

On average I go through 1.25Kg of Bicarbonate of Soda in a single month:

• 2tbsp /wash

2tbsp = 0.030g *33 = ~1kg

1/33 of the cost of 1/5 of £14 = (£14.00 / 5 = £2.80) / 33 = 0.084p !
 

I was just wondering what chemical process was going underway when the Sodium Carbonate hit the water?

[studiot]

3 hours ago, Erina said:

I was just wondering what chemical process was going underway when the Sodium Carbonate hit the water?

 

This page might interest you.

Note hte abrupt solubility change in the temperature region you mention.

[StringJunky]

6 hours ago, Erina said:

I use the single compound to avoid all the other stuff in normal washing powder. However, I did work out the cost and it's about the same:

On average I go through 1.25Kg of Bicarbonate of Soda in a single month:

• 2tbsp /wash

2tbsp = 0.030g *33 = ~1kg

1/33 of the cost of 1/5 of £14 = (£14.00 / 5 = £2.80) / 33 = 0.084p !
 

I was just wondering what chemical process was going underway when the Sodium Carbonate hit the water?

Have you thought about pure soap flakes which is just fatty acid-based? I did read older washing powder formulas used what you are using now and flakes together.

[Erina]

studiot: I see clearly from the diagram that Sodium Carbonate only becomes soluble as the surrounding heat rises, losing its hydrate in the process, this I can confirm. Looking further online it seems that the crystallisation process occurs as the dry powder is an anhydrous compound and in this case can absorb water, which then becomes the water of hydration and thus crystallises.

So Sodium Carbonate crystallises because it's an anhydrous compound and it can't help it?

ref: https://owlcation.com/stem/What-is-a-Hydrate-Chemistry

StringJunky: Thanks for the suggestion.

I actually did try that as I wanted to try to perfume my washed clothes. Using natural essential oil extract I found that the scent would evaporate along with the water during the drying process, the scent would need to be a man made synthetic to have any clinging power.

I don't need to fatty activity in my cleaning process, if I need to remove dirt then I soak in a white vinegar and water bath to kill any bacteria, then wash away in Sodium Carbonate rinse to balance the pH. The agitation during the washing process removes built up "dirt", while the fatty deposits form the soap would only encourage stubborn bacterial growth (which is what Sodium Bicarbonate is good at removing), so best avoided.

[studiot]

8 hours ago, Erina said:

I actually did try that as I wanted to try to perfume my washed clothes. Using natural essential oil extract I found that the scent would evaporate along with the water during the drying process, the scent would need to be a man made synthetic to have any clinging power.

Have you tried soap nuts?

These are a totally natural products from the soap nut tree and are used instead of detergent in some countries.

I can testify that they are inexpensive and do work well in a washing machine.

https://www.google.co.uk/search?source=hp&ei=uQoPXvCAKpTQgweelJGYBw&q=Soap+Nuts&oq=Soap+Nuts&gs_l=psy-ab.3..0l10.1224.3892..5280...0.0..1.1226.5746.3-1j2j2j1j2......0....1..gws-wiz.......0i131j0i10.GH4AF607l_o&ved=0ahUKEwiwwZ-rkOfmAhUU6OAKHR5KBHMQ4dUDCAc&uact=5

[Strange]

16 hours ago, Erina said:

nb. I convert my NaHCO₃ -> Na₂CO₃ in the oven at 230ºC for 1hr

Sodium carbonate is commonly known as “washing soda” and is easy to buy over the counter

15 hours ago, Erina said:

I use the single compound to avoid all the other stuff in normal washing powder. However, I did work out the cost and it's about the same:

You could also look at making your own soap (for the tougher, oil-based marks) - this can be done with vegetable oil and sodium hydroxide (caustic soda). The latter is quite dangerous, so be careful if you try it

11 minutes ago, Strange said:

Sodium carbonate is commonly known as “washing soda” and is easy to buy over the counter

Also worth noting that sodium bicarbonate is manufactured from sodium carbonate. So you are using (wasting?) a lot of energy to “undo” that step. 

[studiot]

20 minutes ago, Strange said:

Also worth noting that sodium bicarbonate is manufactured from sodium carbonate. So you are using (wasting?) a lot of energy to “undo” that step. 

In the Solvay process it is the other way round

 

https://www.google.co.uk/search?source=hp&ei=FBIPXsSDO42SlwTIpaP4CA&q=solvay+process&oq=solvay&gs_l=psy-ab.1.5.0l10.36.1856..4066...0.0..0.122.512.4j2......0....1..gws-wiz.......0i131j0i3j0i10.6J4n6xsJMwk

Edited January 3, 2020 by studiot

[Strange]

3 minutes ago, studiot said:

In the Solvay process it is the other way round

I don’t know which is most widely used, but Wikipedia did confirm my vague memory 

[studiot]

1 hour ago, Strange said:

I don’t know which is most widely used, but Wikipedia did confirm my vague memory 

I don't quite see how ?

The Wiki article I linked to says quite clearly that the bicarbonate is manufactured first as a precursor of the carbonate.

 

Since sodium carbonate is quite soluble, but calcium carbonate is not, you are not likely to find much sodium carbonate free in Nature.
So it has to be prepared from a soium salt (commonly the chloride).
The original process (LeBlanc) was by way of sulphuric acid, the modern(?) process (Fresnel-Solway) is via ammonia.

There is also an alectrolytic process, based on the Nelson Cell which makes it directly from carbon dioxide and sodium hydroxide.
But then you have to get the hydroxide from somewhere.

 

17 hours ago, Erina said:

but wanted to know why they crystalise?

Here is some more (numeric) information which confirms why you are having to heat your decahydrate crystals.

Heats of solution are as follows

Anhydrous salt

Na₂CO₃ + Aq = Na₂CO₃ (aq) ΔH = -5640 calories

Monohydrate

Na₂CO₃.H₂O + Aq = Na₂CO₃ (aq) ΔH = -2250 calories

Decahydrate

Na₂CO₃.10H₂O + Aq = Na₂CO₃ (aq) ΔH = +16160 calories

The negative sign of the first two indicate that heat is evolved on solution of the salt, making the reaction thermodynamically favourable.
 

But the decahydrate absorbs heat (positive sign) to dissolve, which is why you have to heat it.

[Strange]

3 minutes ago, studiot said:

I don't quite see how ?

I just meant “my vague memory [that bicarbonate can be produced from carbonate]”

Quote

Sodium bicarbonate is produced industrially from sodium carbonate:^[70]

https://en.m.wikipedia.org/wiki/Sodium_bicarbonate

As i said, I had no idea what the main production method is. 

[studiot]

2 hours ago, Strange said:

I just meant “my vague memory [that bicarbonate can be produced from carbonate]”

https://en.m.wikipedia.org/wiki/Sodium_bicarbonate

As i said, I had no idea what the main production method is. 

I had no knowledge of the newer american method.

One can learn something every day.

Thanks for that.

[Erina]

Studiot : I am not sure what the soap nuts would be useful for in the cleaning process, the only reason I tried "soap" before was because I wanted to see if it would bind the perfume to the clothing once dry. It did not work as my records show, and that was with a lavender infusion, which is quite strong to human noses.

I have looked into making soap, your suggestion is the "hot" method, and I needed to have a facemark fitted for that, but there ins't a place near by I can achieve that, nor one that carried 3M products (they like to foist other brands on to customers as it makes them more money), I would therefore have had to buy all sizes to see which fit me best and it was just all to expensive. There is a "cold" method available, but I'm just not making soaps right now, and my experiment showed that the scent didn't linger as I hoped anyway.

Fortunately I don't have stains on my clothes, anything too troublesome and I would make a paste from the bicarb, rub it on and leave it to work, repeating the process with an vinegar (acid) wash. If the stain needed more attention, then I would buy a commercial product - this never happens to me though, because I don't care about stains, stains are cool on mans clothing!

From what I read, "soap" is used as topological lubricant to aid in the process of cleaning oneself, it doesn't actually leave anything "clean" (i.e. dirt removed), save for a vehicle to more the dirt somewhere else, but water does that anyway. The benefit of the two cycle system that I employ is that the acid wash (white vinegar : 5% acetic acid) will kill the bacteria build up, and the alkaline wash will bind to it and the water wash it all away, resulting in a neutral finish. That dirt removed is what I am looking for, and the perfume can be of my choosing as an afterthought, if I can find a way to make natural non-synthetics bind with clothing..

 

Strange: I buy in 5kg (~11Ib) bulk bags, portion it out and (used to) cook around 1kg a time, there is no high street commercial outlet that will give me a better deal than Amazon. So it's cheaper this way. But I'll stop cooking the batch now because of the crystallisation (I can't believe I never checked, perhaps it's the water outside of London?) and will just use it strait.

 

• My main reason for coming here was to find out why the crystals form, and I think it's because the anhydrous powder compound drinks the water and thus solidifies, is that right?

[Strange]

26 minutes ago, Erina said:

From what I read, "soap" is used as topological lubricant to aid in the process of cleaning oneself, it doesn't actually leave anything "clean" (i.e. dirt removed), save for a vehicle to more the dirt somewhere else, but water does that anyway.

Soaps (and detergents, generally) have a hydrophilic (water attracting) and lipophilic (fat attracting) part. This enables them to bind to oily or fatty compounds  and emulsify ("dissolve") them in water, hence removing them from skin, clothes, dishes, whatever.

[Erina]

I see.

Well, was my hands aside, I think that the Bicarbonate of Soda can do that in spades, so I'll stick with the bicarb. But good to know.

[Strange]

2 hours ago, Erina said:

I see.

Well, was my hands aside, I think that the Bicarbonate of Soda can do that in spades, so I'll stick with the bicarb. But good to know.

Don't use it to wash anything aluminium, though, as it can corrode it.

[studiot]

5 hours ago, Erina said:

Studiot : I am not sure what the soap nuts would be useful for in the cleaning process, the only reason I tried "soap" before was because I wanted to see if it would bind the perfume to the clothing once dry. It did not work as my records show, and that was with a lavender infusion, which is quite strong to human noses.

Soap is an artificial compound called sodium stearate.

Soap nuts are the fruits of the soap nut tree which contain a substance that looks a bit like liquid hand soap but is 100% natural and called saponin.

Saponin is a natural detergent (detergents are a general term for cleaning compounds that work with water).

5 hours ago, Erina said:

• My main reason for coming here was to find out why the crystals form, and I think it's because the anhydrous powder compound drinks the water and thus solidifies, is that right?

I thought we had answered that rather fully.

Sodium carbonate has several different crystalline forms, which are rather temperature and moisture dependent.
The temperature of

On 1/2/2020 at 5:41 PM, Erina said:

but I have since come to find that all it does is collect and crystalise on contact with <30ºC temperature (i.e. cold) water.

This is exactly what my diagram shows.

Below 30^oC, the decahydrate is the stable form and its solubility drops rapidly with temperature, hence your crystals.
Because solution of the decahydrate required intake of heat, dissolving lowers the solution temperature further promoting crystallisation.
Warming these a bit drives off some of the water of crystallisation and the crystals revert to another form, the heptahydrate as the whitish powder coating on the outer parts since that is where the water leaves the crystals.

You will not get the anhydride unless you heat very hard and your starting point (the bicarbonate) will probably reduce to a mixture of carbonate and bicarbonate when you first put it in the oven. This is called sodium sesquicarbonate.

Edited January 3, 2020 by studiot

[MigL]

Who would have thought you can do experiments with laundry...