Demo #2: Recrystallisation of Bismuth

This is demonstration #2. The recrystallisation of bismuth

Category:

Education

Tags:

• bismuth
• recrystallisation
• diamagnetism
• demonstration
• CNA
• college
• of
• the
• north
• atlantic
• grand
• falls-windsor

[hermanntrude]

bismuth is unusual because the solid floats on the liquid. perhaps that's why. As for your crystal and how it was formed i cannot guess. I suspect if you tried to polish it you'd lose the coloured sheen on the surface.

[burchified]

The faster it cools, the better they look. Try dipping the cooling pan in cold water.

[hermanntrude]

@burchified true? with most crystals, crystallization is better when slower

[hermanntrude]

you are correct it's to do with the formation of oxide layers but why would the oxide layers form multiple colours? it's something to do with surface plasmons i think. intereference is part of the explanation too

[hermanntrude]

same thing, yes I think so.

[daenumen]

@hermanntrude wait for the bismuth to dissolve?

surface tension? could make it float? ('pour liquid off of the top of the solid')

bismuth IS toxic.

[boswell255]

That's a very nice crystal! One thing I have noticed is all of the videos of making bismuth crystals, they all seem inverted. I have a bismuth crystal which looks entirely different,as though it was cast inside one of these "inverted" poured out crystals, and I was wondering how it was formed. Also, can they be polished, like gold or nickel chrome?

[mrhomescientist]

People are right, the colors are from a thin oxide layer that forms on the surface of the crystals. The differences in color are due to different thicknesses in this layer, causing light to refract and interfere in different ways. It also depends on the angle you view it, which is called iridescence. It's the same phenomenon that causes the different colors in soap bubbles, and the wikipedia article on that has an excellent explanation. I've done this experiment too, and I'll post a video soon.

[hermanntrude]

The half-life of bismuth is longer than the age of the universe. This means for all intents and purposes it behaves as if it isnt radioactive.

[midorad]

I think the explanation is due to the formation of thin oxide layers.