Sciencemadness Discussion Board

Melting sulfur - can SO2 be created?

Draeger - 29-5-2020 at 17:02

Basically, I was just wondering if melting sulfur would generate any toxic gasses, which I am guessing would just be SO2, hence the title. Maybe melting it under a layer of water (which would boil, but if it's enough it might be okay for my purposes?) would help catch any SO2 that might be evolved?
Can't do anything outside or anywhere ventilated, by the way.

beerwiz - 29-5-2020 at 17:40

Sulfur melts at 115.21°C. I melted it recently and I didn't notice any SO2. I kept the melt going for a full month and when I opened the flask I was surprised that it smelled like acetic acid (vinegar).

Draeger - 29-5-2020 at 18:50

Quote: Originally posted by beerwiz  
Sulfur melts at 115.21°C. I melted it recently and I didn't notice any SO2. I kept the melt going for a full month and when I opened the flask I was surprised that it smelled like acetic acid (vinegar).

Okay. Thanks.

DraconicAcid - 29-5-2020 at 19:09

As long as it doesn't catch fire, it's fine.

chornedsnorkack - 30-5-2020 at 09:33

This:
http://www.inchem.org/documents/icsc/icsc/eics1166.htm
quotes flashpoint as +160 Celsius an autoignition temperature as +230 Celsius.
How much quiet oxidation takes place below the runaway autoignition temperature?

Draeger - 30-5-2020 at 13:46

I started my experiment, and just a few seconds into heating it, far from melting the sulfur, I smelt a lot of what I assume to be sulfur dioxide, so I cancelled it. I have no idea what happened there.

beerwiz - 30-5-2020 at 20:16

Quote: Originally posted by chornedsnorkack  
This:
http://www.inchem.org/documents/icsc/icsc/eics1166.htm
quotes flashpoint as +160 Celsius an autoignition temperature as +230 Celsius.
How much quiet oxidation takes place below the runaway autoignition temperature?


I was running some sulfur experiments today, and I put sulfur in a covered crucible and heated it to 400'C for 2 hours. When I opened the crucible I was surprised that the sulfur was burning inside, kept wondering how it caught fire but the 160'C autoignition explains it.

[Edited on 31-5-2020 by beerwiz]

Ubya - 31-5-2020 at 01:17

Quote: Originally posted by Draeger  
I started my experiment, and just a few seconds into heating it, far from melting the sulfur, I smelt a lot of what I assume to be sulfur dioxide, so I cancelled it. I have no idea what happened there.


does the SO2 you are smelling, smells like rotten eggs?

what's your source of sulphur? it is probably contaminated with something that decomposes to SO2 (or H2S) with minimal heating

chornedsnorkack - 31-5-2020 at 02:26

Molten sulphur is a good solvent for hydrogen sulphide. Hydrogen sulphide appreciably changes properties of molten sulphur and is commonly found dissolved in molten sulphur.

Sulphur melting equilibrates slowly. On fast melting, sulphur melts at 120 Celsius and refreezes at 120 Celsius if promptly cooled back. On prolonged heating, the melting point drops and stabilizes at 115 Celsius.

Draeger - 31-5-2020 at 06:36

Quote: Originally posted by Ubya  
Quote: Originally posted by Draeger  
I started my experiment, and just a few seconds into heating it, far from melting the sulfur, I smelt a lot of what I assume to be sulfur dioxide, so I cancelled it. I have no idea what happened there.


does the SO2 you are smelling, smells like rotten eggs?

what's your source of sulphur? it is probably contaminated with something that decomposes to SO2 (or H2S) with minimal heating

Nope, it's not H2S. It smells like the ambient smell sulfur has.

My sulfur is sulfur granules from Onyxmet, 99,95% purity. I thought granules would be easier to use than a powder. I don't really have the best place to work with chemicals.

Herr Haber - 31-5-2020 at 08:10

I wouldnt worry if I were you.

You're probably only melting a few grams at a time and the amount of SO2 you'd generate when it catches fire shouldnt worry you if you are outside or just on the edge of the window.

But you mentioned water ! There are a few interesting things you can do with molten sulphur and water. Try pouring it slowly in a long enough column and make beads.
If you have a Dremel you can make some pearls and give someone the chemist's equivalent of a noodle necklace :)

Also note what happens when the temperature goes up (and before ignition).