Easy, sustainable method of alkali production

[downwardsfromzero]

This is a response to the "self sustainable organic chemistry" thread. A kind of inorganic variant, perhaps.

The method:

1. Collect urine-soaked clothing from nearby toddler/drunkard. You could also piss on some kind of fabric yourself, of course. Cotton or similar vegetable fibre is best, and children's urine won't smell as bad as that of adults.

2. Place in bucket, ideally one with a good lid.

3. Place a bowl of water - preferably distilled - on top of the clothing in the bucket. Make sure it is stable. The water must stay in the bowl. I suppose an open bottle would also work instead of the bowl, nestled down into the damp fabric.

4. Place tightly-fitting lid on bucket. Seal with tape if you think it's necessary depending on how tightly the lid fits.

5. Leave for 2-3 days, depending on temperature. Colder takes more time. Any longer and the clothes go mouldy.

6. The bowl/bottle will now contain a weak ammonia solution. Bingo! Free alkali!

7. Wash the clothes!!!!! Or compost them if it's gone badly mouldy (hence the recommendation to use vegetable fibres).


This process can be repeated with fresh urine-soaked cloth and the original water to make a stronger ammonia solution. There will, of course, come a point of diminishing returns in this respect.

 

[narmz]

so this is gross, but what's it useful for?

 

[InMotion]

Urine is an exceptionally poor source of ammonia. Ammonia is also not an 'alkali'.

There are sustainable ways to produce NaOH as well as KOH. A solution of NaOH can easily be made from electrolysis of salt. KOH can also be made iirc from wood-ash.

 

[SKA]

Electrolysing NaOH out of brine requires a special electrolytic cell with a membrane.
Building a simple electrolytic cell isn't too difficult, but the membrane required for
yielding NaOH (+ Chlorine, Hydrogen & Oxygen-gas) from electrolysing brine is probably
hard/expensive to obtain. >>> Chloralkali process - Wikipedia

Or you should happen to be in the possession of Nafion membranes...

 

[Yerba]

Better to do it like the old-timey soapmakers and steep hardwood ash in water for a crude NaOH solution.

 

[endlessness]

or, calcium hydroxide + sodium carbonate which should react to make lye. Calcium hydroxide can be made from calcinated shells, sodium carbonate is easily made by cooking sodium bicarbonate which anybody can find in pharmacies, grocery stores and supermarkets.

That first post sounds very off, I dont suggest people do that, there are better ways to get bases.

 

[InMotion]

You don't need a special membrane it can be done with a salt/gelatin bridge.

Edit - pretty sure you can score dozens of nafion from dead car batteries. Scrap yards buy dead car batteries for around $5, bet you could scoop one up there no issue.

What I do to get ammonia is gas it from NH4NO3 + NaOH in minimal water into a cold water solution. Titrate and dilute to a desired concentration. Most people here wouldn't want to handle ammonia gas however.

 

[SKA]

Interresting InMotion,

Can you explain how to set up such an electrolytic cell with a salt/gelatin bridge?

 

[InMotion]

Sure, a salt bridge is essentially a way to separate an anode and a cathode and allows electrochemical work to be done. Gelatin or agar with an electrolyte can be used to fill a glass U shaped tube to create a salt bridge. I have used simply wet filter paper saturated with an electrolyte(Not for NaOH production however).

(ignore the labels of the chemicals this is just a diagram).

And for basic information about a salt bridge - Salt bridge - Wikipedia


For some base information on the process check this out - Chloralkali process - Wikipedia
Although I admit these 'instructions' sound like they are written by someone on GHB, there is more information out there I promise I am just lazy.

Laboratory procedure

Electrolysis can be done with two beakers, one containing a brine and one containing pure water. A salt bridge can be made of a length of bent hose (a metal pipe should not be used) to connect the two beakers. Plug the ends with tissue or cloth. Put any electrode in the solution that you want to produce sodium hydroxide and hydrogen with. Put an electrode made from a carbon rod (or a pencil lead) into the solution that you want to produce the chlorine gas. If you want the hydrochloric and hypochlorous acid from the chlorine dissolution, put its electrode in the pure water solution. If you want the sodium hydroxide and hydrogen gas, put its electrode into the pure water solution. Connect the "any" electrode to the negative terminal of a 12 volt power supply.

In this particular instance I believe maintaining a divided cell(or membrane) and a relatively cool temperature is important otherwise products such as sodium chlorate will form over time(iirc). I remember seeing something about someone using PVC tubing to make a cell for alkali production. This method is okay for making liquid solutions but not so much solid NaOH because when the water is evaporated or boiled away it comes into contact with CO2 making Na2CO3(sodium carbonate).

Carbon electrodes can be harvested from some bigger lantern batteries and such, I don't recommend pencil lead(it doesn't last). Or they can be bought cheaply.

 

[SKA]

That is fascinating information but indeed it is messed up lingually.
Could you perhaps simplify and clearify this information in laymen's terms?

 

[InMotion]

Sure thing.

The overall equation(not half cell stuff to keep it simple):

2 NaCl + 2 H2O → 2 NaOH + Cl2(g) + H2(g)

So what is happening here is typical of most any electrolysis experiment. An oxidation and a reduction are occurring. At the Anode(negative electrode) the oxidation occurs. At the Cathode(positive electrode) the reduction occurs.

Cathode: 2H+ + 2e- -> H2(g)
Anode: 2Cl- -> Cl2(g) + 2e-
Solution: Na+ + OH- -> NaOH(aq)

Because though Cl2(chlorine gas which is slightly soluble in water) reacts with H2(hydrogen gas) and OH- (hydroxy ion) the two electrodes need to be separated by a membrane or barrier. Otherwise products such as sodium chlorate(NaClO3) form. These likely will still form but only in small concentrations. This should not present any real issues but if one is worried about it it can be reduced very easily .

Here is another decent website - Science Aid: Electrolysis

A typical example of a home-made cell generates about a 50% NaOH Solution.
Example here: Make Lye From Salt and Gelatin

Carbon is a good choice for a cheap and inert electrode. This guy used windshield wiper blades, hehe.

 

[InMotion]

Better yet use a sodium salt such as sodium carbonate so there is no chlorate/perchlorate formation

 

[The Day Tripper]

Better to do it like the old-timey soapmakers and steep hardwood ash in water for a crude NaOH solution.

I think that would give you potassium carbonate iirc. To get koh from hardwood ash you would need to cook it with calcium hydroxide just like with sodium carbonate/lime to get naoh.

 

[InMotion]

KOH is inside of wood ash but so is K2CO3, and other stuff. Alkali oxides as well I am sure which on contact with water form the hydroxides.

The thing is solutions of NaOH and KOH after exposure to air give Na2CO3 and K2CO3, which is why you cannot evaporate the solutions that are made to get solid NaOH/KOH. So the concentrations have to be right for their end use. Hence why I mention electrolysis, an STB could be done with the resultant solution.

There aren't too many vessels one can 'safely' boil solutions of NaOH/KOH. They react with a lot of metals especially with heat. Glass works, but it will etch the glass over-time(even borosilicate). They must be stored 'air-tight' for them to last. Also Ca(OH)2 has worse solubility at high temperatures in water iirc. Might be better done at room temp.

 

[downwardsfromzero]

Glad this topic got a ball rolling for a while. I was feeling silly/mischievous when I posted it (could you tell? ) Haven't been here lately to follow the progress.

Ammonia solution is quite alkaline, even if it is not strictly a caustic alkali like the alkali metal hydroxides.

The inspiration for my original post was that AFOAF indeed had a bucket of urine-soaked cloth, courtesy of their young child, which reeked of ammonia. That set me thinking and - hey, presto! - fun with home chemistry!

To those who find the idea disgusting, isn't a bucket full of powdered root bark, caustic alkali (a product of the chlor-alkali industry, usually) and petroleum distillate quite a disgusting notion, too?

Ammonia is, I am told, useful at some stages of spice purification. Why not use an abundant waste product to cheaply (freely) make your own?

I do like the way people got on to a discussion of home electrolysis. Molten salt could be used to make metallic sodium which is then be dissolved in distilled water to make sodium hydroxide solution (and hydrogen) but that would be even more ridiculous than the urine-ammonia technique, wouldn't it?

Talking of dissolving alkali metals, why not dismantle some fresh lithium batteries and dissolve the lithium in water to make lithium hydroxide solution? It might not be as cheap as caustic soda but it would be fun IF ONE FOLLOWS APPROPRIATE SAFETY PRECAUTIONS!!!

That has rather strayed from the initial idea of cheapness and sustainability, so to reiterate - electrolysis of brine, preferably using solar electricity, probably wins as the cheapest, most sustainable method of alkali production at home, followed by wood ash plus burnt snail shells.

 

[downwardsfromzero]

And another thing...

Ammonia solution is useful in producing your own sodium carbonate from common salt as follows:

The Solvay process

Concentrated brine, formed by dissolving the maximum possible 359 g L−1 of table salt in pure water, is saturated with ammonia. In practice, you might as well make as strong an ammonia solution as you can, then add the salt. This solution is then saturated with carbon dioxide (e.g. from a sparkling drinks maker device or from burning charcoal perhaps) and chilled. Sodium bicarbonate precipitates and may be filtered off. To obtain sodium carbonate, heat the bicarbonate at 105[deg]C, as described elsewhere.