LD5050
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Cool looking sulfur crystals
I was recrystallizing sulfur and I got some pretty cool looking crystal formations
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macckone
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Excellent!
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LearnedAmateur
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Interesting, I've found that crystals commonly form in a manner which you don't expect, depending on how pure the solute is, whether you use a seed
crystal or not, and if the solution is supersaturated. Basic caffeine forms a similar structure consistently upon crystallisation, if agitated when
supersaturated at room temperature. What solvent did you use - CS2, toluene, or something other? Was it disturbed or contaminated with insoluble
particles? I think that would explain the needle cluster, as it radiates out from a single point which would originate at the initial nucleation site.
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phlogiston
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You'd be surprised at how complex it is sometimes to produce a specific form of crystal.
Tiny amounts of impurities can inhibit the growth of some crystal faces and promote others, giving rise to different crystal shapes.
The seed can have a dramatic effect. There have been factories where one day all of a sudden some crystallisation tanks yielded a differently
crystallised product, and this 'condition' then spread to other tanks in time until they were completely unable to produce their original product.
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MrHomeScientist
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This sort of thing would go well in the Pretty Pictures thread!
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LD5050
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Quote: Originally posted by LearnedAmateur  | | Interesting, I've found that crystals commonly form in a manner which you don't expect, depending on how pure the solute is, whether you use a seed
crystal or not, and if the solution is supersaturated. Basic caffeine forms a similar structure consistently upon crystallisation, if agitated when
supersaturated at room temperature. What solvent did you use - CS2, toluene, or something other? Was it disturbed or contaminated with insoluble
particles? I think that would explain the needle cluster, as it radiates out from a single point which would originate at the initial nucleation site.
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I'm impressed at your knowledge on crystal formation and you are correct on how you mentioned impurities. There actually was a bit of impurities that
made it through the coffee filter which was a very fine and brown in color. This was recrystalized from xylenes that I got from the hardware store. I
actually gave up on this batch because of all the impurities and set it aside to find it later filled with these cool looking crystal formations. The
other more pure batches didn't grow crystals anywhere near this big.
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diddi
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where you using xylenes as solvent?
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j_sum1
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In my experience using xylene and toluene as solvents for sulfur, it s very easy to get monoclinic crystals. The orthorhombic form seems a lot more
difficult to make. Literature says that the orthorhombic form occurs when the crystallisation occurs below about 96°C. (And by literature, I mean
wikipedia and other shallow sources -- which is why I have not provided a citation.)
I have not obtained orthorhombic crystals of any decent size though. It seems to be something that requires a bit of care and control.
Eventually I would like to have an example of both for my element collection -- a nest of monoclinic needles -- probably embedded in some resin and a
nice large rhombic crystal -- big enough to handle without damaging easily.
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diddi
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there are many lovely sulphur forms which occur in nature j_sum. I have included then in my elements even tho they are not pure. hope to get to Mt
Ijen next year to collect some.
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