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Sulphur melting point

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LAN_403

Conundrum

Sat Mar 17 2012, 05:10PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Hi all.
From what I have been able to find on the Net, sulphur should melt at a well defined temperature of 115.21 Â°C according to Wikipedia.

My sample of flowers of sulphur seems to melt closer to 140C.. any ideas?
I am using an oven thermometer to check, but it appears that these are notoriously inaccurate.
Will try again with an LM35 as these are +/- 0.5 degrees Celsius.

This aside, can anyone suggest a way to get an even mixture of powdered zinc, powdered manganese and sulphur?
I was thinking a mortar and pestle, but getting powdered zinc is a royal pain.

Manganese isn't a big problem, MnO2 from defunct road lamp battery then use heat and carbon to get powdered Mn.

Thanks!

Bored Chemist

Sat Mar 17 2012, 07:02PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Grinding rocket fuel in a mortar and pestle isn't a good idea.

There are zinc based paints that you might be able get powdered zinc from- or you can just buy it.
What are you planning to do, make a phosphor?

klugesmith

Sat Mar 17 2012, 08:48PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Conundrum wrote ...
Manganese isn't a big problem, MnO2 from defunct road lamp battery then use heat and carbon to get powdered Mn.

How did that work out for you?
I understand that MnO2 can be reduced by aluminothermy, a.k.a. a thermite reaction.
Though the metallic product would probably form nuggets while molten.

Regarding the sulphur MP question: my recollection is that it must be heated very gently to form a clear yellow, mobile liquid. At the temperature rises, it becomes darker and more viscous as S8 molecules break and tangle. Some tanker-industry references say the molten stuff freezes at 238 F and is usually handled between 260 and 300 F; gets too viscous above 320 F. Conversion to degrees C is left as an exercise.

Conundrum

Sun Mar 18 2012, 09:23AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Yes, phosphor is the intended application.

More specifically, the green/blue sort (ZnS:Mn:Cu) which changes colour with applied voltage.
I am aware that you can just buy EL sheet etc but the paint I have is dried up and no longer works..

Seems that you can DIY the dielectric as well using barium carbonate (BaCO3) and titanium dioxide.

'Klugesmith I haven't actually tried this (yet!) but as this was a common method to make pure metals from mixed oxides way back in the olden days it should work just fine.
best done in a fume cupboard as metal fumes can be very dangerous!

-A

IamSmooth

Mon Mar 26 2012, 07:40PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Bored Chemist wrote ...

Grinding rocket fuel in a mortar and pestle isn't a good idea.

There are zinc based paints that you might be able get powdered zinc from- or you can just buy it.
What are you planning to do, make a phosphor?

It's been a while that I've done this type of chemistry. What is the reaction he is intending to do?

GluD

Mon Mar 26 2012, 11:23PM

Registered Member #1221 Joined: Wed Jan 09 2008, 06:17PM
Location: Odense, Denmark
Posts: 196

The reaction, as I remeber it, most people do when making zinc sulfide phospors is to mix zinc, sulfur and a very small amount either copper or manganese or something else depending on the desired colour. After mixing it is usually ignited to produce zinc sulfide which is "doped" with the copper or manganese. Expect smelly and toxic sulfurous fumes if you do this.

IamSmooth

Tue Mar 27 2012, 03:52AM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Where is the source of the phosphorus?

Conundrum

Tue Mar 27 2012, 07:02AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

phosphor = generic name for something that glows under UV, etc.
The early phosphors really were phosphorous or a compound, thats how it was discovered in the first place.
Alchemists boiled urine, leaving them with various compounds one of which visibly glowed in the dark for a short time.

Another useful note, if you happen to have the "wrong" king of sulphur which contains oxides and other garbage, melt it in an oxygen free atmosphere until liquid.
Upon cooling, grind it carefully with the Zn metal powder and small amount <1% of Mn prepared as previously mentioned and if desired a small amount of a salt such as potassium chloride to provide Cl ions for the reaction centres.
Copper also works.

I had glowing compounds with just zinc metal shavings and sulphur, but it works much better if you get powdered zinc by the zinc acetate+oxalate method or so I've been told..
precipitates out basically pure zinc metal which is easily separated out.

Zinc can be obtained from the casing of the battery you obtained the MnO2 from.
Has to be one of the old school zinc carbon ones like they use in some road lights.
Seen two smashed ones on the way home already.

Much fun can be had by putting the prepared Zn.S.Mn mixture under a glass sheet, evacuating all the air then zapping it with a near UV laser.
Not done this experiment yet but it is rumoured to produce a bright phosphor indeed.
If it works, make sure to post your results.

-A

Bored Chemist

Wed Mar 28 2012, 06:49PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

"but it works much better if you get powdered zinc by the zinc acetate+oxalate method or so I've been told.."
By whom? Because I really rather doubt it.

radiotech

Wed Mar 28 2012, 07:36PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

Sulphur is a bit tricky because of its allotropic forms and the triple-point changes.
In our sulphuric acid plant we got it out of the rail tankers by pumping in steam.

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