Sciencemadness Discussion Board - Best way to extract sodium hypochlorite?

Quote: Originally posted by Crazy_Chemist

I need to extract it.

Why?

Well, need and need, I just like to produce new chemical to have in my homelab

But...

Quote: Originally posted by sauveurdumonde

I recall reading that hypochlorite powders tend to have sensitive explosive tendencies. It may not be very easy to store anhydrous.

I dont think Im going to store it at ahome...

So, I think I'm going to the pool-store instead.

When I need chlorine gas, I usually use HCl and KMnO4.

woelen - 11-3-2022 at 02:14

NaClO is quite unstable. It never is sold as a solid. The solid does exist though, but it only is a lab curiousity, which fairly quickly decomposes.
Commercial solutions are limited to appr. 15%, usually less (12...13%). If the concentration is raised, then you see two competing decomposition reactions. In one reaction there is disproportionation into NaCl and NaClO3, and in the other there simply is decomposition with production of O2. The latter reaction can be enhanced severely by transition metal impurities. E.g. if you add a few drops of a cobalt salt solution to a concentrated solution of NaClO, then the solution starts bubbling/foaming (production of O2).

chornedsnorkack - 11-3-2022 at 02:23

Quote: Originally posted by woelen

NaClO is quite unstable. It never is sold as a solid. The solid does exist though, but it only is a lab curiousity, which fairly quickly decomposes.
Commercial solutions are limited to appr. 15%, usually less (12...13%). If the concentration is raised, then you see two competing decomposition reactions. In one reaction there is disproportionation into NaCl and NaClO3, and in the other there simply is decomposition with production of O2. The latter reaction can be enhanced severely by transition metal impurities.

Disproportionation is promoted by heating. How do strong NaClO solutions behave on cooling - gentle cooling (deep freeze) and harsh cooling (like liquid nitrogen)?
What would happen if frozen NaClO solution is allowed to stand at low temperature with but out of direct contact with a strong desiccant like CaO?

Sulaiman - 11-3-2022 at 05:26

I like problem solving challenges,
lateral, diagonal and upside-down thinking.

But potentially explosive substances in glassware is a poor choice.
(in my opinion)

Tsjerk - 11-3-2022 at 06:28

Sodium hypochlorite pentahydrate is stable at refrigerator temperatures according to wiki.

Texium - 11-3-2022 at 11:47

Quote: Originally posted by Crazy_Chemist

When I need chlorine gas, I usually use HCl and KMnO4.

That's not a very efficient way of generating chlorine. You'd be much better off finding either trichloroisocyanuric acid (TCCA), sodium dichloroisocyanurate (NaDCC) or calcium hypochlorite at a hardware or pool store, and using that in combination with HCl to generate chlorine. At least one of those should be readily available for you and cheap. Save your permanganate for better things.

woelen - 11-3-2022 at 12:46

I fully agree with Texium. KMnO4 is way to valuable for making Cl2.

Best is TCCA or Na-DCCA. I do not like Ca(ClO)2, because the resulting Cl2 is not very pure. It also produces ClO2 (you can see that the solution gets a more intense color than one should expect from Cl2 alone). The ClO2 most likely is due to chlorate impurity of the Ca(ClO)2, which almost always is present, especially if the material is somewhat older. A similar thing I also observed with somewhat older bleach as a source of Cl2.

The major disadvantage of using TCCA or Na-DCCA is that poorly soluble cyanuric acid is formed in the reaction, which easily leads to excessive foaming. The Cl2-gas, however, is very pure (disregarding water vapor).

[Edited on 11-3-22 by woelen]

S.C. Wack - 11-3-2022 at 15:45

Quote: Originally posted by chornedsnorkack

How do strong NaClO solutions behave on cooling - gentle cooling (deep freeze) and harsh cooling (like liquid nitrogen)?
What would happen if frozen NaClO solution is allowed to stand at low temperature with but out of direct contact with a strong desiccant like CaO?

The hydrates are made by cooling etc. Frozen bleach would have a hard time evaporating.

That's not a very efficient way of generating chlorine.

I did the math and don't see it...more efficient based on HCl maybe, but HCl is really cheap. Permanganate generates more Cl per gram of oxidant and the cost per gram of Cl is pretty much the same, not that TCCA has ever been sold locally outside of pool specialists. Permanganate (sold in about half the hardware stores here since forever) has no storage issues, very much unlike the others.

Quote: Originally posted by woelen

I do not like Ca(ClO)2, because the resulting Cl2 is not very pure.

The product(s) of the reaction depends on the amount and strength of acid (and sometimes temperature).

[Edited on 12-3-2022 by S.C. Wack]

karlos³ - 11-3-2022 at 18:09

Quote: Originally posted by Antiswat

calcium hypochlorite cannot be bought in europe- GENERALLY.

Uh what?
You mean OTC or what?

chornedsnorkack - 12-3-2022 at 04:30

Quote: Originally posted by chornedsnorkack

The hydrates are made by cooling etc. Frozen bleach would have a hard time evaporating.

The vapour pressure of water is:
at +20 Celsius - 2339 Pa
at 0 Celsius - 611 Pa
ice at -20 Celsius - 103 Pa

So when a frozen hydrate is stored in a closed vessel but out of contact with a powerful desiccant, like CaO, P4O10 or concentrated H2SO4 (all of whic would react with NaClO if in contact, but are even less volatile than water), then dehydration of hydrates would be one competitive reaction.

unionised - 12-3-2022 at 04:47

The hydrates are made by cooling etc. Frozen bleach would have a hard time evaporating.

That would be a serious disappointment to those who make freeze dryers.

S.C. Wack - 12-3-2022 at 08:32

Quote: Originally posted by chornedsnorkack

The vapour pressure of water is:
at +20 Celsius - 2339 Pa
at 0 Celsius - 611 Pa
ice at -20 Celsius - 103 Pa

In other words, it would have a hard time evaporating.

That would be a serious disappointment to those who make freeze dryers.

If what we said had anything to do with operating freeze dryers.

[Edited on 12-3-2022 by S.C. Wack]

Texium - 12-3-2022 at 10:47

That's not a very efficient way of generating chlorine.

I did more math, and I still see it.

Reaction of potassium permanganate with HCl:
2 KMnO₄ + 16 HCl —> 2 KCl + 2 MnCl₂ + 5 Cl₂

2.5 moles of Cl₂ per mole of KMnO₄. Permanganate is not regularly sold in any hardware store I've been to. The product "Pot Perm Plus" is generally only obtainable by special order. If I wanted to get it from my local Home Depot, I would have to order it to the store to pick up. Other stores don't offer it at all. It was the same case where I lived in Texas. Maybe other locales have it OTC. So that's 794 grams for $30.30, or about $6 per mole, giving us a theoretical yield of $2.41 per mole of chlorine gas. With the caveat that permanganate isn't actually OTC.

Screen Shot 2022-03-12 at 11.14.08 AM.png - 710kB

Now let's take a look at TCCA:
C₃N₃O₃Cl₃ + 3 HCl —> C₃N₃(OH)₃ + 3 Cl₂

3 moles of Cl₂ per mole of TCCA. I could buy this at my local Lowe's in the store today if I wanted to:

Screen Shot 2022-03-12 at 11.15.03 AM.png - 630kB

While it's much more expensive upfront, that's for 11.34 kg of 94% TCCA, or 10.66 kg of pure TCCA. This comes out to about $3.25 per mole, giving us a theoretical yield of $1.08 per mole of chlorine gas.

While researching this, I was rather surprised to find that pool chemicals seem to be less available now than in years past when I bought them for my lab. I couldn't find NaDCC on any sites, for instance, while I know that I had bought some from Lowe's or Home Depot in-person in 2015 in an affordable 5 lb container of granules. Otherwise I would have included that in the price comparison too. It's always worth keeping in mind that availability of OTC chemicals is constantly shifting, and some things that we take for granted may be phased out for unclear reasons.

S.C. Wack - 12-3-2022 at 13:24

So that's 794 grams for $30.30, or about $6 per mole, giving us a theoretical yield of $2.41 per mole of chlorine gas.

My calculations were based on my (half perhaps, I'd have to actually go check) cost, not your needlessly expensive figure (the $20 at amazon is still not the lowest that comes up with a search...their 5# @ $40.34 was used for the 93.6% TCCA)

On topic, I suspect that distillation with a high enough vacuum could concentrate dilute bleaches to a point where a hydrate could be crystallized out by cooling.

Texium - 12-3-2022 at 16:25

So that's 794 grams for $30.30, or about $6 per mole, giving us a theoretical yield of $2.41 per mole of chlorine gas.

My “needlessly expensive figure” was based on what is available at hardware stores, which I used because you seemed to find it important to point out that permanganate is easier to find OTC than TCCA (maybe it is in Cornworld, but here it’s certainly not). The price I quoted is for Home Depots across the US. Maybe you have some special hardware store in Cornworld that sells it for half the price of the competition. Lucky you, if that’s the case.

The best price I can find online for permanganate is this: https://www.fleetfarm.com/detail/filter-mate-potassium-perma... which with the $8 shipping they offer does come out to about half the price of the Home Depot stuff. Still, that only puts it roughly even with TCCA.

Overall, I still think TCCA is a better choice unless you have local access to much cheaper permanganate. TCCA has the advantage of not leaving you with manganese waste to dispose of too.

Tsjerk - 13-3-2022 at 01:53

On topic, I suspect that distillation with a high enough vacuum could concentrate dilute bleaches to a point where a hydrate could be crystallized out by cooling.

My thoughts as well. You might even use a freeze drying apparatus for this.

S.C. Wack - 14-3-2022 at 14:02

So that's 794 grams for $30.30, or about $6 per mole, giving us a theoretical yield of $2.41 per mole of chlorine gas. With the caveat that permanganate isn't actually OTC.

My calculations were based on my (half perhaps, I'd have to actually go check) cost, not your needlessly expensive figure

I was off. The OTC product is actually $28.48. For 4.75#. But only until the sale is over, then it'll be $32.

The best price I can find online for permanganate is this: https://www.fleetfarm.com/detail/filter-mate-potassium-perma... which with the $8 shipping they offer does come out to about half the price of the Home Depot stuff. Still, that only puts it roughly even with TCCA.

You mean like what I said?

Permanganate generates more Cl per gram of oxidant and the cost per gram of Cl is pretty much the same

That product you found might be the same thing but with a different label, and (getting to the actual point) also be exactly what I have in stock from many years back, magically stable. Now you can put your skepticism to the test?

So how about finding a similar price for TCCA and recalculating, now that you've proven that permanganate is in fact cheaper. Personally if I was going to special order something I'd go with the lowest price, esp. if it was to my door. And I'd buy a lot of it if it was useful and stable for decades. What to do with Mn+2...yeah it's like radioactive waste and can't be isolated from solution, it's totally useless uh huhm, unlike cyanuric acid which is so useful for...stabilizing Cl in pools.

I've used permanganate many times to make calculated amounts of Cl, even hypochlorite. Nothing wrong with it.

[Edited on 14-3-2022 by S.C. Wack]

unionised - 14-3-2022 at 14:41

That would be a serious disappointment to those who make freeze dryers.

If what we said had anything to do with operating freeze dryers.

It has.

Removal of water, as the vapour from a frozen material is (1) what the plan here was and (2) how a freeze dryer works.

Whether you remove it with a vacuum pump or a desiccant isn't a huge difference.
Obviously the pump works better but, if your idea that cold stuff won't evaporate were true, then freeze dryers wouldn't work.
They do.
It isn't.

Texium - 14-3-2022 at 17:21

So how about finding a similar price for TCCA and recalculating, now that you've proven that permanganate is in fact cheaper. Personally if I was going to special order something I'd go with the lowest price, esp. if it was to my door. And I'd buy a lot of it if it was useful and stable for decades.

I didn’t “prove that permanganate is cheaper:” my final conclusion was that at best it’s about the same cost as TCCA for chlorine production, so I don’t even know what you’re talking about. My main point from the beginning was that your statement of what is commonly available OTC is completely backwards. Permanganate is rarely available OTC nowadays. TCCA is available at pool stores and most hardware stores. Doing the math has led me to conclude that if you can get reasonably priced permanganate, it’s just as cost effective as TCCA. Congratulations, you’ve changed my mind with this exercise. That being said, I’ve also observed that some pool chemicals go on deep clearance when they’re out of season, so being able to snag some TCCA or possibly NaDCC at a ridiculously low price isn’t unheard of. Bottom line is, either of these chemicals are good for chlorine production. Which one is best depends on what is locally available for you.

Fantasma4500 - 15-3-2022 at 08:21

okay so, what about persulfate? it forms chlorine on contact with table salt or in solutions of chloride

1kg sodium persulfate 13 euros
Na2S2O8 + 2 NaCl = Cl2 + 2 Na2SO4
1000g + 491g = 297g(4.2M) + 1193g

https://www.ebay.de/itm/144018689254?hash=item21882ecce6:g:K...

2 KMnO4 + 16 HCl = 2 KCl + 2 MnCl2 + 8 H2O + 5 Cl2
1000g KMnO4 yields 1121g Cl2- with 1845g HCl .. 6.15L HCl 30%? now we wanna also factor the HCl into this equation. seems about 3e/L 30% here

what about TCCA
C3Cl3N3O3 + 3 HCl = 3 Cl2 + C3H3N3O3
1000g + 470g = 915g + 555g

so 1kg TCCA, 1.5L HCl 30%? one quart the HCl required, while it produces only 200g less Cl2. 81.6% of the chlorine that KMnO4- albeit with 4x as much HCl. it could appear TCCA is infact more compact

so lets say, for 1kg of Cl2 gas you need:
1100g TCCA 14e/kg = 15.4e
890g KMnO4 29e/kg = 26e
3300g NAPS - 13e/kg = 43e

0.89x 6L HCl at 3e/L would give 16e cost for HCl 30% - 5.34L for KMnO4
and 1100g TCCA + 1.65L 30% HCl =5e
NAPS uses table salt, 1kg is 0.5e, 0.25e.

so the corrected price for the 3, for 1kg Cl2 gas comes out to
TCCA: 20.4e
KMnO4: 42e
NAPS: 43.25e

KMnO4 i would agree is not readily available and is even a watched chemical, NAPS is more under the radar. however KMnO4 does yield KCl and MnCl2 but manganese can also be toxic. the real bonus with KMnO4 is how colorful it is. i went off with european ebay price for TCCA. infact i cant find anything but 150g KMnO4 from thailand priced at 45e. KMnO4 MAY however, eventually, be possible for the amateur chemist to make at home, once i progress into cracking that one. i believe cyanide may be made from cyanuric acid somehow, but i couldnt find my way around last time i looked into it, so TCCA does also yield a somewhat useful product.

SWIM - 15-3-2022 at 11:22

That would be a serious disappointment to those who make freeze dryers.

If what we said had anything to do with operating freeze dryers.

Freeze dryers don't evaporate things.
They sublimate things.

S.C. Wack - 15-3-2022 at 15:55

Whether you remove it with a vacuum pump or a desiccant isn't a huge difference.

I'm guessing that you don't use desiccators much? I do; using lime, sulfuric acid, calcium chloride. In fact I'll be posting in another thread about an experiment with lime that's already been going on for a week. I posted what I did because I'm aware of their limitations.

If one adds a kg of desiccant, with 100 ml of water on a dinner plate on a short pedestal on the shelf, then yes a substantial amount of water will be transferred at room temperature...after 3 days...but it would be unsurprising if vacuum obviously outperformed that even in such unrealistic use. I can't imagine that doing it in a freezer would go well at all.

[Edited on 15-3-2022 by S.C. Wack]

Sulaiman - 16-3-2022 at 00:10

on the topic of cost effective chlorine generation ;

it does not matter

availability, disposability and safety are the important parameters - to me

at amateur level there is no need for industrial volumes or cost effectiveness.

Tsjerk - 16-3-2022 at 00:20

Enthalpy of sublimation is a bit higher than enthalpy of evaporation (50 kJ/mol against 40 kJ/mol). But the surface area at which sublimation can occur quickly becomes much larger during sublimation as pores and cavities are formed. Surely sublimation occurs slower because of the lower temperature, but the temperature needs to be low here anyway.

I can imagine freeze drying to be fast, I even noticed first hand it can be fast. A vail with a couple of milliliters goes in an hour at -18 at mediocre vacuum. Larger samples take longer, but when left over night tens of milliliters are gone. But who cares? You have to cool the samples anyway, so whether it is in a freezer with or without vacuum doesn't really matter.

unionised - 16-3-2022 at 11:00

Quote: Originally posted by SWIM

Freeze dryers don't evaporate things.
They sublimate things.

SRSLY?
You don't realise that sublimation is evaporation?

unionised - 16-3-2022 at 11:02

I'm guessing that you don't use desiccators much?

I guess you don't use vacuum desiccators much.
Perhaps you should.

SWIM - 16-3-2022 at 11:12

Quote: Originally posted by SWIM

Freeze dryers don't evaporate things.
They sublimate things.

SRSLY?
You don't realise that sublimation is evaporation?

Not according to most sources who don't happen to be you.

Potassium Permanganate

MadHatter - 16-3-2022 at 15:34

Texium, that's an excellent price for KMnO₄. I used to buy from Sears, retail
store, for well over $30 for 5 LBS. On the plus side, it was truly OTC. As for
NaOCl, just my opinion, there's no need to have it in a "solid" form. It works
fine just the way it is.

S.C. Wack - 16-3-2022 at 15:50

I guess you don't use vacuum desiccators much.
Perhaps you should.

Who said anything about using vacuum desiccators?

The truth/fact (what I deal in) is, my desiccator is the vacuum kind, but I have little desire to run one of my pumps constantly (or buy something that will measure vacuum and activate the pump at a set pressure) or set up a drying train to keep water out of the pump oil (the recirculating aspirator pump water gets warm before long). When small amounts of things to be dried are used, it creates its own vacuum.

If one wants to try an experiment in the *actual spirit* of the original suggestion, they could weigh some ice cubes and put them in a cup in a bag containing silica gel in the freezer and weigh the cup from time to time. I'd be interested to hear the results.

Needless to say, it would be unsurprising if the verdict was that it would be wiser not to freeze the hypochlorite.

Fantasma4500 - 17-3-2022 at 14:54