Sciencemadness Discussion Board

Disulphur dichloride reaction with rubber

plante1999 - 28-7-2012 at 14:03

I was synthetising S2Cl2 from chlorine and molten sulphur in a rubber stoppered apparatus, the S2Cl2 was imediatly distilled of and condensed using an air condenser (glass tube). I saw that there was evident reaction with the rubber and the S2Cl2 vapor, after the reaction I was left with a tar black crystalline mass in the reaction vessel and a very small amount of S2Cl2 ( 10% yield based on sulphur). The rubber stopper was dessintwgrated with many holes in it.

How could I turn the rubbers stopper resistant to S2Cl2?

S2Cl2 with Tiny amount of rubber contamination:

EDIT: I have now touched the mass with glove on and the mass seam to be rubber... I guess boiling hot S2Cl2 is able to dissolve rubber. More test is needed to know if it is the same rubber as the original one.


[Edited on 28-7-2012 by plante1999]

[Edited on 28-7-2012 by plante1999]

kristofvagyok - 28-7-2012 at 14:25

I would suggest to use PTFE tubing, it is resistant to (almost) everything(:

For this "accident" I also had a similar reddish-black solution when I poured some peroxysulfuric acid on a buchner funnel (as cleaning) and the water vacuum just pulled it out from the bottle, whoops :D

Almost every case additives are added to polymers to make them more soft, more hard, smell good ect. these additives are often not as resistant to chemicals then the original polymer would be.

NurdRage long ago posted a video about getting some phthalic acid from nitrile gloves... Octyl phthalate is added to the polymers as a plasticiser (to make it more soft) with a lot other things... And because the octyl phthalate is not as resistant to strong bases.... It could be easily extracted.

So the polymer tubing what you use should also contain some things that may react with S2Cl2 (what is not a really friendly stuff). Use PTFE;)

Endimion17 - 28-7-2012 at 14:29

Quote: Originally posted by plante1999  
How could I turn the rubbers stopper resistant to S2Cl2?

Nohow. It simply dissolves rubber. Vulcanization, remember? Sulfur bridges, etc.

plante1999 - 28-7-2012 at 17:34

I have PVDF rods, any idea to dissolve the PVDF and coat the rubber?

If I cannot use rubber is there any substitute nonreactive stopper?


peach - 29-7-2012 at 01:02

With the sulphur chlorides gradually fuming off hydrogen chloride as they pick up moisture from the atmosphere (and air inside their container), they will tend to gradually get around the majority of seals and ruin numerous polymers / elastomers over time. Even the special 'Ultrachemically resistant' grades of Tygon (2075 and 2375) can start going opaque around it.

I happen to be searching around about polymers / elastomers at the moment and found this site which, whilst not being from a big chemical company, may still be of interest to you.

A silicone stopper would likely be a little better. One option, lacking a silicone stopper, is to smear silicone grease (or a fluoro based grease) all over the exposed surfaces of the elastomer, the same way builders and painters will smear barrier cream on their hands, arms and face to keep the epoxy and cement based products off their skin. This is kind of what's done with the natural rubber / silicone septa seals for some of the air free chemistry now, the inner surface (the one that actually touches the chemicals inside the glass) is backed by a very thin layer of PTFE; so the needle will still puncture it but it is highly resistant to chemical attack.

Ideally, you should be using ground glass for something like sulphur chlorides. You may notice your sample is gradually giving off some 'steam' (hydrogen chloride fumes) when disturbed. If it has access to much moisture as it distils (particularly if the system is completely open and you live somewhere humid), I would not be surprised if your yield was dropping off purely for the sake of it partially hydrolysing; e.g. if you are using a retort style arrangement and allowing it to drip out into a collection tube.

The rubber going funny, and the black muck, is a very common theme I have seen other air sensitive chlorides engaging in.

I originally made some sulphur chloride / dichloride just for fun and wasn't too bothered about it staying perfect, so I bottled it up in a regular plastic capped bottle. Very soon after, it looked as it does in the photos below (the process has actually slowed down as it's used up the moisture in the bottle and bag). But here it is a year on. The inside of the bag is wet. There are droplets of free liquid in there, which is the hydrogen chloride dissolved in the moisture from the air that was in there; so it's hydrochloric acid. As is common with these things, it's taken the label off. Or is trying to.

What I found interesting was the yellow deposit on the top (outside) of the cap. The cap it's self is sealed on there with PTFE tape, so I find it difficult to believe it's gotten round that. Perhaps the sulphur chloride(s) themselves have actually permeated the top of the plastic cap. I would hazard a guess that the top is LDPE. The 'sweating' appearance of caps is a sure sign that something akin to the photos below is on the way. I have seen at least two different chlorides from two different chemical suppliers doing exactly the same thing, despite being in their (differently capped) original bottles.

[Edited on 29-7-2012 by peach]

blogfast25 - 29-7-2012 at 05:53

Rubbers that contain no (or very little) residual double bonds will not be affected much by S2Cl2. Candidates are EPDM, EPR (peroxide cured), Hypalon, FPM (Viton and competitors) , polyacrylate rubber, Santoprene and others. Unfortunately these are only very rarely (if AT ALL) used for lab stoppers or hose.

Typical 'under the bonnet' automotive rubber parts will resist S2Cl2 quite well because they're mostly made of the elastomers cited above.

[Edited on 29-7-2012 by blogfast25]

[Edited on 29-7-2012 by blogfast25]