innervision
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Unknown Crystals during sulfur purification
I was on a quest to purify some commonly available wettable dusting sulfur, so I decided to go the recrystallizations route...
Unfortunately, S is not the only thing to crystallize.
Method:
I poured dusting sulfur into a flask with Xylene until no more dissolved and a layer formed on the bottom. I placed the flask into a boiling water
bath, and swirled ocassionally until I hit about 82 degrees C, which was as hot as I was getting it with my heating method. I then kept it at about
82C to make sure nothing was suspended in the solution.
I then would decant it rapidly into a warm beaker to cool.
The xylene was decanted off into a trash glass container, and the remaining sulfur crystals (which looked MUCH purer at that point) were washed with
anhydrous isopropanol twice, then with water four times.
The water would turn very white/cloudy at first, but lighten until further washing of the S crystals turned up no cloudiness.
I evaporated some of the isopropanol in a beaker and some of the cloudy water in another beaker at 54C. The water beaker would be left with a white
crust on the bottom, but the IPA was interesting. When about a third of the original volume and cooled, the IPA beaker had long, thin crystals growing
in it, and a gray solid at the bottom of the beaker. Of course, upon complete evaporation, there would be some S too.
I assume the gray material to be clay, and the white to possibly be CaCO3, because that's is what I have gathered from researching this horrible
sulfur concoction they call dusting sulfur. The long, thin crystals however, I can not figure out. A silica coumpound floats in the back of my mind
because I read somewhere that vaguely mentioned it.
Any clue as to what this could possibly be? ...or a general chems it could belong to?
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chemoleo
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Intriguing, but how can we help if we don't know the composition of 'dusting sulphur'? What is it used for, what product is it?
Zillions of compound dissolve in xylene, and in water/isopropanol at the same time (which excludes CaCO3/silica compounds, which arent remotely
soluble in xylene/IPA).
So how, do you think, could anyone make an educated guess?
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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12AX7
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Idunno. If someone already researched it, or has any inkling whatsoever what those acicular crystals are. The assumption is that, impure as it is,
dusting sulfur has a similar composition across the country or world.
Unfortunately, I am also completely without clue. Do you have enough (or can you make enough) for an analysis? At least find out if it's organic or
not.
Tim
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innervision
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That's the thing. Dusting sulfur does not say its inert ingredients. I think I read somewhere that it isn't legal to say what else is in there. It
makes sense, but i'm not sure if that is actually true or not.
What I have is Green Light Wettable Dusting Sulfur: Sulfur 90%, inert 10%.
The bag has no clues as to what the other ingredients might be from reading warnings. It does say do not use it in combination with an oil emulsifier.
It is a 3.75lb. bag, so I could play around with it more. The largest flask I have with a stopper is 125mL, and I don't want too many stray xylene
fumes (even though I am using a respirator) so it is a hassle to do large batches, although I might.
I know this "what is it" question was extremely vague, but I was hoping someone might recognize the crystal structure from something they have done
with dusting sulfur.
Also, is there a way to disable an emulsifier without reacting with the sulfur? It would be so much easier if I didn't have to recrystallize first. At
least that way I could remove the water soluble junk first, then maybe use a solvent that swallows little sulfur, but goes after the rest. Then
recrystallize the sulfur and be done.
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chemoleo
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Try the following:
Shake your dusting sulphur in water, see if something dissolves, or rather whether the insoluble sulphur dissolves wihtout residue in xylene.
If not, shake your dusting sulphur in weak HCl/some acid, and repeat.
Or, dissolve in weak base (NaOH), same thing again.
If nothing works, it's probably either insoluble inorganic, or insoluble organic. See if you can remove the latter with a solvent that does *not*
dissolve sulphur, such as ethanol, acetone.
I am sure you'd get rid of at least some of the impurities....
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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innervision
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I have tried shaking it in water. Since wettable dusting sulfur contains an emulsifier of some sort, it gives a suspension that takes a very long time
to settle. I think I had a small flask of some sitting for two days before it was somewhat clear on top. It was still cloudy to an extent, and the
settled dusting sulfur on the bottom was still the same 'ol light yellow like there was a good portion of a white substance in it.
When I did the water wash after the xylene extraction, there was a MUCH cloudier solution than just the water and dusting sulfur shaken.
The main reason why I haven't tried the acid or base is that I don't want a polysulfide contamination or especially H2S formation.
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12AX7
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Could try heating it with water in an autoclave? Melt and consolidate the sulfur..
Tim
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innervision
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Seeing how I lack an autoclave, that's probably not going to happen. Also, melting solids is not something I like to do. It's such a pain to work
with.
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