Sciencemadness Discussion Board - Another Go at Making Disulphur Dichloride

Another Go at Making Disulphur Dichloride

aga - 28-4-2015 at 12:32

Given that this is Beginnings (no references) it must be noted that:-

* Chlorine gas can kill you.
* This entire experiment was conducted in a fume hood.
* Disulphur Dichloride is highly corrosive, gives off HCl+SO₂ gasses and must be stored sealed on ice.

Further to my Factice experiments it was found that Disulphur Dichloride works well, so more was required.

It can be made by reacting powdered elemental Sulphur with Chlorine gas.

The equation appears to be quite complex, yet overall it can be stated as :-

2 S + Cl₂ => S₂Cl₂

Chlorine Gas can be produced by the oxidation of Hydrochloric acid by Potassium Permanganate.

16 HCl + 2 KMnO₄ => 2 KCl + 2 MnCl₂ + 8 H₂O + 5 Cl₂

To convert 30g of powdered sulphur, with a 20w% solution of HCl, the stoichimetry was calculated to be :-

Reagents:-
S : 30g
20w% HCl : 273 ml
KMnO₄ : 30g

Products :-
Cl₂ : 10.4 litres
S₂Cl₂: 63.2g

Previously a Cl₂ scrubber was used to absorb any unreacted gas.
This seemed wasteful given the high affinity of the S to Cl₂ - so much so that simple agitation of the S caused suck-back in an earlier experiment.

To eliminate the need for a scrubber and hazardous excess Cl₂ production, an anti-bump head was chosen as the reaction vessel with a rubber glove sealed over one end with rubber bands to serve as a 'gasometer' or gas reserve (agaOmetertm

.

In effect the system is sealed and all Cl₂ produced MUST be consumed in the reaction with S to avoid pressure build-up and explosion.

A short length of rubber tube was added to the vac take-off spiggot so that Air could be flushed from the system.
As soon as a chlorine smell was detected (by an agaNosetm

this tube was folded and sealed with a clothes peg (agaValvetm

.

Practically speaking, simply regulating the rate at which HCl is added was a very effective way to regulate the rate of gas production and therefore pressure.

The rubber glove gives a clear visual indication of the pressure in the system, and would simply blow off in the event of over-pressure, although this would of course incur an escape of Chlorine gas.
That would be bad, yet less bad than the glass blowing apart (agaPanictm

The addition of a large and a small magnetic stirbar to the anti-bump head caused a situation in which the normal orderly stirring becomes chaotic and random (agaMixatm

, which is beneficial in this case as it splashes the powdered sulphur and the liquid all over the walls of the bulb, increasing the surface area and reaction rate.

22 minutes into the reaction and all of the powdered sulphur was a yellow liquid.

During the reaction the liquid was measured to be 52.6 C with an infra-red thermometer.

After 1 hour 36 minutes the rate of Chlorine production appeared to be negligible, and the experiment was stopped.

The liquid contents of the reaction vessel were filtered, and 31.41g of product was recovered (the remaining solids presumably being sulphur) representing a yield of 49.7%.

Given my own lack of experience and knowledge, i was quite pleased with almost 50% from an untested procedure.

The photographs explain it better.

This is what a small amount of leaked S₂Cl₂ did to the rubber glove acting as the gas reserve:

This test tube had a few drops of S₂Cl₂ added to water. Immediately elemental sulphur precipitated.

2 S₂Cl₂ + 2 H₂O => SO₂ + 4 HCl + 3/8 S8

vmelkon - 28-4-2015 at 13:36

Looks like a fun experiment. Personally, I would not use KMnO4. I would go with that cheap pool supply stuff : Trichloroisocyanuric acid (If I got the name right).

aga - 28-4-2015 at 13:50

I tried it with Beach & HCl.

The bleach has a foaming agent in it which makes it a pain, and it didn't make Cl₂ very fast either.

I'll see if i can get some of the pool stuff, as it did seem a waste of KMnO₄.

blogfast25 - 28-4-2015 at 14:00

Are you quite sure you've got S2Cl2? Not a mixture of SCl2 and S2Cl2? Any mass balance done?

Could be a nice opportunity to determine Cl content of something, since as you love Mohr's titrations so much?

Nice looking product though. Any plans to use for something else?

Magpie - 28-4-2015 at 14:01

Yes, pool TCCA and 20% HCl (see Len1, in Prepublication) is a convenient and cheap way to produce Cl2.

I see you did not dry your Cl2. Drying would likely increase yield. But this requires more glassware which increases the potential Cl2 leak points.

I'm surprised your glove (agaOmeter) held up to the Cl2 gas.

S2Br2 is much easier to make and might work for your factice? Of, course, first you must make Br2, a liquid.

Overall, nice work!

blogfast25 - 28-4-2015 at 14:06

Quote: Originally posted by aga

I'll see if i can get some of the pool stuff, as it did seem a waste of KMnO₄.

Or MnO2 + HCl. Cheaper than KMnO4.

Magpie - 28-4-2015 at 14:09

Quote: Originally posted by blogfast25

Are you quite sure you've got S2Cl2? Not a mixture of SCl2 and S2Cl2? Any mass balance done?

Yes, this was discussed by Sauron et al. IIRC Sauron concluded that this does not occur when making S2Br2, ie, it is the only product.

aga - 28-4-2015 at 14:11

Quote: Originally posted by blogfast25

Are you quite sure you've got S2Cl2? Not a mixture of SCl2 and S2Cl2? Any mass balance done?

Could be a nice opportunity to determine Cl content of something, since as you love Mohr's titrations so much?

Nice looking product though. Any plans to use for something else?

No idea at all of what i've got.

The first batch was massively over-chlorinated, and made veg oil go fizz.
Second batch made it solidify with no fizzing.
Judging simply by the colour this is somewhere in between.

Would a Mohr's not just show it has chlorine in it, or are you saying that the Amount of Cl₂ will show the ratio of products ?

Any suggestions as to the 'what else' ?

aga - 28-4-2015 at 14:15

Quote: Originally posted by Magpie

I'm surprised your glove (agaOmeter) held up to the Cl2 gas.

S2Br2 is much easier to make and might work for your factice? Of, course, first you must make Br2, a liquid.

These are top quality gloves from the supermarket ...

To be honest, i expected them to fall apart, yet seeing as the Product will be used for making Rubber, i reasoned that Rubber gloves might last long enough for the process to complete, and they did.

S2Br2 sounds like it is worth a try, although i don't seem to have any Bromine compounds in my inventory.

j_sum1 - 28-4-2015 at 14:20

I want to do this. However I have no need for S2Cl2 and no desire to store it. So I guess it is off the table. Intriguing process and uncomplicated set-up (aga's trademarked inventions aside) and a rather dramatic looking product.
I might attempt the previously discussed U-tube method though. (Number 23 on my current list of projects. I need some more time in the lab.)

blogfast25 - 28-4-2015 at 14:26

Quote: Originally posted by aga

Would a Mohr's not just show it has chlorine in it, or are you saying that the Amount of Cl₂ will show the ratio of products ?

Any suggestions as to the 'what else' ?

I'm just playing Devil's Advocate here. Most likely it's either pure S2Cl2 or a mixture of S2Cl2 and SCl2. But you're never certain until you analyse it properly.

Assuming the product contains no free Cl2 (a bit of refluxing would get rid of that anyway) and only S as a second element (bar trace contaminants, of course) then determining w% Cl would settle the question of its empirical formula from molar ratio.

[Edited on 28-4-2015 by blogfast25]

aga - 28-4-2015 at 14:27

If the product scares you, dump it into water to get your powdered sulphur back, with a weak mix of HCl and H₂SO₃.

It isn't something i like to think is hanging around my lab, so it will get used tomorrow morning.

aga - 28-4-2015 at 14:31

Quote: Originally posted by blogfast25

determining w% Cl would settle the question of its empirical formula from molar ratio.

Right-oh. Mohr's it is then.

Refluxing in Air would destroy the product due to atmospheric moisture, and i'm out of Argon, so any free Cl₂ will have to stay put.

blogfast25 - 28-4-2015 at 14:31

Quote: Originally posted by aga

It isn't something i like to think is hanging around my lab, so it will get used tomorrow morning.

What if it eats your lab overnight?

aga - 28-4-2015 at 14:33

Then we can determine the Cl₂ content by measuring What it ate, and How much

A bit like a Burger Mystery and Suspense party.

[Edited on 28-4-2015 by aga]

blogfast25 - 28-4-2015 at 14:58

Quote: Originally posted by aga

Refluxing in Air would destroy the product due to atmospheric moisture, and i'm out of Argon, so any free Cl₂ will have to stay put.

Does it fume in open air? [Edit: yes, it does!]

In any case, Mohr's only determines chloride, not chlorine. Unless any free chlorine present gets significantly converted to chloride somewhere in the analytical process, no measuring error is introduced.

I note also as per Wiki that S2Cl2 is supposed to be "golden yellow" and SCl2 more "orange-red".

[Edited on 29-4-2015 by blogfast25]

blogfast25 - 28-4-2015 at 16:16

Looks like Mohr's determination of chloride won't work here because SO2 will be oxidised by chromate, the indicator used in that method. Can't see an immediate fix for that interference... so let me ponder that for a while.

[Edited on 29-4-2015 by blogfast25]

Molecular Manipulations - 28-4-2015 at 19:59

Instead of Mohr's, how about reacting a known quantity with water, filter off the sulfur and add an excess of silver nitrate to precipitate chloride. After taking into account silver chloride's solubility product (very small) the total chlorine contant can be known. I doubt silver sulfite has a low enough solubility to precipitate.
EDIT it's about 4.6mg/L, not much, but considering sulfur dioxide's low solubility, it shouldn't precipitate.

[Edited on 29-4-2015 by Molecular Manipulations]

DJF90 - 29-4-2015 at 00:02

Quote: Originally posted by aga

After 1 hour 36 minutes the rate of Chlorine production appeared to be negligible, and the experiment was stopped.

The liquid contents of the reaction vessel were filtered, and 31.41g of product was recovered (the remaining solids presumably being sulphur) representing a yield of 49.7%.

Call me old fashioned, but it is conventional to isolate products as pure as possible. I appreciate that purity may not be critical for your intended application, but it is good practice to start as you mean to go on. Filtration may remove insoluble impurities (sulfur) but any excess chlorine (as Cl₂ or SCl₂) will remain. The trick to removing this is a quick reflux over some fresh sulfur followed by distillation of the S₂Cl₂.

Quote: Originally posted by aga

Refluxing in Air would destroy the product due to atmospheric moisture, and i'm out of Argon, so any free Cl₂ will have to stay put.

You do not need Argon as the compound in question is not air sensitive. It is however moisture sensitive (as you note) so take precautions to exclude moisture - drying glass in the oven at 110 *C and assembling hot with a CaCl₂ drying tube in place should suffice. As others have mentioned, your (lower than expected) yield is likely a consequence of the lack of dryig train between the Cl₂ generator and the reaction mixture.

[Edited on 29-4-2015 by DJF90]

aga - 29-4-2015 at 00:24

Quote: Originally posted by Molecular Manipulations

Instead of Mohr's, how about reacting a known quantity with water, filter off the sulfur and add an excess of silver nitrate to precipitate chloride. After taking into account silver chloride's solubility product (very small) the total chlorine contant can be known. I doubt silver sulfite has a low enough solubility to precipitate.
EDIT it's about 4.6mg/L, not much, but considering sulfur dioxide's low solubility, it shouldn't precipitate.

[Edited on 29-4-2015 by Molecular Manipulations]

How about taking a known qty of the product, react with a larger volume of water, centrifuge to get the S to the bottom, then drip a known conc of silver nitrate into the same container with a burette until it stops forming a white precipitate ?

My only worry about adding water & filtering is that i only have 31g of the product and would rather not use all of it overcoming losses due to filtering.

CuReUS - 29-4-2015 at 04:05

S₂Cl₂ can be used in place of PCl₃ or SOCl₂ to convert alcohols and carboxylic acids to alkyl chlorides and acyl chlorides respectively
http://chemistry.mdma.ch/hiveboard/chemistrydiscourse/000216...
btw why don't you try to make it in-situ ? that might prevent formation of SCl₂
see this

Quote:

Another similar synthesis, generating sulfur chloride in situ:

Mix quickly and thoroughly 205-215 g of pulverized fine NaOAc and 10g dry sulfur powder, the mixture is quickly transferred to a wide-mouth 1 liter RBF and wetted w/25 ml acetic anhydride. Into the flask through the rubber cork extend 1) a wide tube for chlorine in-flow........

https://erowid.org/archive/rhodium/chemistry/anhydrides.html

found two very good write-ups as well

read the 6th post by antoncho and 8th post by catastrope
http://chemistry.mdma.ch/hiveboard/novel/000207554.html

[Edited on 29-4-2015 by CuReUS]

Magpie - 29-4-2015 at 04:49

Quote: Originally posted by CuReUS

S₂Cl₂ can be used in place of PCl₃ or SOCl₂ to convert alcohols and carboxylic acids to alkyl chlorides and acyl chlorides respectively

That's a very useful thing to know as PCl3 and SOCl2 are more difficult to produce.

Quote: Originally posted by CuReUS

btw why don't you try to make it in-situ ? that might prevent formation of SCl₂

But I don't think aga is after an anhydride.

Wiki shows how the S2Cl2 can be purified by distillation, or, apparently by just letting it sit and auto-convert from SCl2.

To determine purity, why not use the standard technique: determine the boiling point.

aga - 29-4-2015 at 05:58

As far as i can work out, the two possible reactions with water both end up simplified to leave the interesting species as :-

2 SxCl₂ + 2 H₂O => 4 HCl + SO2

To me this means that regardless of the ratio of SCl₂ to S₂Cl₂ the products are

4 HCl + SO₂ giving HCl and H2SO₃

If that's right so far, then would not a simple titration of the acids with NaOH give the total acid molarity, of which the HCl component would be 4/5ths of that total, from which the Cl₂ can be calculated ?

I just tried adding known [M] of AgNO₃ and you can't see anything as the mix is too murky.

At 17.2ml black precipitate became visible.

With that as the endpoint the mm calculates out at 197.5 g/mol, which is 146% out of range.

aga - 29-4-2015 at 06:01

Quote: Originally posted by Molecular Manipulations

After taking into account silver chloride's solubility product (very small) the total chlorine contant can be known.

Oh !

You mean zap out all the silver chloride, capture it, dry it and weight it !

OK. I can still do that with my failed attempt as i've not thrown the stuff away yet.

blogfast25 - 29-4-2015 at 06:21

Quote: Originally posted by aga

[How about taking a known qty of the product, react with a larger volume of water, centrifuge to get the S to the bottom, then drip a known conc of silver nitrate into the same container with a burette until it stops forming a white precipitate ?

My only worry about adding water & filtering is that i only have 31g of the product and would rather not use all of it overcoming losses due to filtering.

You would never see the end-point, trust me. You need the chromate indicator to see when all chloride has been converted to AgCl. Then the chromate forms red Ag2CrO4.

I've found the simplest of fixes to the sulphite/chromate problem. Mohr's titration requires slightly alkaline conditions. Adding a pre-determined amount of hydrogen peroxide will oxidise the sulphite to sulphate but in alkaline condition hydrogen peroxide cannot oxidise chloride to chlorine (only in acidic conditions does this happen). Sulphate does not interfere because it's far more soluble than AgCl (personal experience confirms that).

For 250 ml of analyte solution only about 1.7 g of your product is needed. And that affords as many titrations as your heart contends!

Now it's your call. If you want to proceed, I'll do the calcs for you.

[Edited on 29-4-2015 by blogfast25]

gdflp - 29-4-2015 at 07:18

Quote: Originally posted by CuReUS

S₂Cl₂ can be used in place of PCl₃ or SOCl₂ to convert alcohols and carboxylic acids to alkyl chlorides and acyl chlorides respectively
btw why don't you try to make it in-situ ? that might prevent formation of SCl₂

I actually had this idea a couple of weeks ago and was going to try it as soon as I'm done with finals. I was going to try it with oxalic acid to make oxalyl chloride. I would have done it sooner, but I've been crazy with finishing up term papers and finals. I should have the results of an experiment by the end of May.

aga - 29-4-2015 at 08:16

Quote: Originally posted by blogfast25

Quote: Originally posted by aga

Now it's your call. If you want to proceed, I'll do the calcs for you.

Yeah !

Sod the factice. I'll make more S_xCl₂ for that using this new, quicker method.

Cheers ! What's the process bloggers ?

I already have 1.13g of the product diluted to exactly 250ml in water then filtered (as per MM's suggestion) of which about 100ml remains.

There is 25ml of that had an excess of AgNO₃ added, and the 1.16g of filter paper is currently drying with the bits in it.

blogfast25 - 29-4-2015 at 10:06

Quote: Originally posted by aga

Cheers ! What's the process bloggers ?

I already have 1.13g of the product diluted to exactly 250ml in water then filtered (as per MM's suggestion) of which about 100ml remains.

There is 25ml of that had an excess of AgNO₃ added, and the 1.16g of filter paper is currently drying with the bits in it.

I'll email you the protocol as a *.doc, see what you think. Then, if you go ahead, you can attach it here with your results, saving you some time in the write-up.

Re. precipitating and weighing, aka gravimetry, it's a lot trickier than you might imagine. Usually a 0.1 mg analytical balance is needed [depends on sample size, of course], as well as a suitable filtration medium, good washing practices, tips and tricks to avoid occlusion and reliable drying methods. VERY easy to get wrong. At a minimum, look up an existing protocol. Getting a dubious result can lead to a wild goose chase.

AgCl is also light sensitive and can't be calcined too high. But gravimetric determination of silver or chloride as AgCl is definitely in use, no question about it.

If I thought it was a better option than Mohr's titration, I'd have suggested it, believe me. Gravimetry is about as laborious as volumetry here, but the latter is slightly easier IMO.

Important point on the synthesis: try and establish a mass balance. Weighing your (tared) reactor before and after chlorination already gives a rough idea of what you've synthesised (assuming no foolish losses, spills etc).

[Edited on 29-4-2015 by blogfast25]

aga - 29-4-2015 at 11:14

Quote: Originally posted by blogfast25

Weighing your (tared) reactor before and after chlorination already gives a rough idea of what you've synthesised (assuming no foolish losses, spills etc).

DOH !

Why did i not think to do that ?

Buggrit.

blogfast25 - 29-4-2015 at 17:01

Re-reading len1’s notes on the preparation of S2Cl2/SCl2:

http://www.sciencemadness.org/talk/viewthread.php?tid=10377#...

… I quote:

Quote:

In addition both S and Cl2 are soluble in S2Cl2 to a great extent (corresponding to stoichometries of about S5Cl2 at the one extreme, and S2Cl5 at the other) - it is clear therefore that it is difficult to differentiate precisely the amount of mixture and chemical compound in the S/Cl system […]

len1 did distil his S2Cl2 and his stoichiometry assessment (presumed formula) was based on a mass balance.

So I think an accurate mass balance for your next synthesis is key here.

aga - 29-4-2015 at 23:36

Mass balance ?

Sorry to seem Dense.

Does that mean keeping track of all the weights from start to finish ?

blogfast25 - 30-4-2015 at 06:37

Quote: Originally posted by aga

Mass balance ?

Sorry to seem Dense.

Does that mean keeping track of all the weights from start to finish ?

Weigh your sulphur, then weigh your product at the end of your reaction. 'On paper' that allows you to determine obtained stoichiometry, if we assume all weight increase is due to reaction, not physical dissolution (absorption).

But going by len1, dissolved ('free') sulphur and/or dissolved ('free') chlorine can not be excluded a priori. It's a bit of a pain, this S/Cl system.

[Edited on 30-4-2015 by blogfast25]

aga - 2-5-2015 at 01:15

Quote: Originally posted by Molecular Manipulations

OK. Did that and arrived at a mm of 134.96 g/mol

I guess that means it's all S₂Cl₂

j_sum1 - 2-5-2015 at 05:08

Congratulations. Well done.

Tdep - 25-5-2015 at 04:39

I got some new glassware so I though I'd give this a try. Worked like a dream! Well, a very bad smelling dream. Started with 25g sulfur, ended with 52.1g of product which corresponds to a 99% yield according to complete conversion to S₂Cl₂. Ran for 3 hours, went smoothly, no sulfur left in reaction flask. My end goal is sulfur nitride so I don't need to worry about complete conversion, as both chlorides are referenced to work fine in the synth.

aga - 25-5-2015 at 05:42

Cool !

Nice one.

It does Honk a bit dunnit ?

Tdep - 25-5-2015 at 05:48

It does. Sulphur chemistry is always one to observe with eyes only. Gotta lower my limit of acceptable chlorine exposure too, throat is kinda scratchy. Nothing an excess of chocolate milk won't fix though.

How are you storing yours aga? I don't want to stopper it for risk of chlorine build up in the flask but don't want it destroyed in the few days until I can use it

aga - 25-5-2015 at 06:44

I had mine in a ground-glass stoppered RBF.

When i opened it after 24Hrs there had been considerable pressure build-up.

After that it went in a Simax 500ml bottle (plastic top).

Since the sulphur crystals precipitated out there has been no noticeable pressure build-up.

I filtered and put back in the stoppered RBF.

(also went and checked to see if it had exploded, and no, it hadn't).

Edit: this is about 70mls S₂Cl₂.

[Edited on 25-5-2015 by aga]

blogfast25 - 25-5-2015 at 06:49

Quote: Originally posted by aga

Since the sulphur crystals precipitated out there has been no noticeable pressure build-up.

Isobaric conversion:

S₂Cl₂ === > S + SCl₂

Determine Cl content on supernatant residue AT ONCE! :cool:

Even simpler: weigh S and supernatant residue. Do mass balance to determine conversion rate.

[Edited on 25-5-2015 by blogfast25]

aga - 25-5-2015 at 13:08

Quote: Originally posted by blogfast25

Determine Cl content on supernatant residue AT ONCE! :cool:

Residue ?

That's the Product !

blogfast25 - 25-5-2015 at 14:36

Quote: Originally posted by aga

That's the Product !

Errm... rest of the product!

aga - 25-5-2015 at 14:56

Can't quite grasp your lingo old chap.

Do you want me to bag a brace of bounders then squash the bosh with a flibbertooty ?

Crashing the crate into the briney is a given !

What! What! Hussars!