View previous topic | View next topic


Page 1 of 2
Goto page 1, 2  Next

1080955.  Sat Jun 21, 2014 1:12 am Reply with quote

Very! Great find, Posital! The process probably needs a bit of speeding up; body temperature-only would take too long. A hair dryer?

1080957.  Sat Jun 21, 2014 1:39 am Reply with quote

'yorz wrote:
Very! Great find, Posital! The process probably needs a bit of speeding up; body temperature-only would take too long. A hair dryer?


So many destructive uses for gallium....

1080969.  Sat Jun 21, 2014 4:13 am Reply with quote

Gallium melting in a hand.

1080992.  Sat Jun 21, 2014 9:20 am Reply with quote

Posital wrote:

Applying a bead of gallium to the surface of an aluminium can destroys the structural integrity of the aluminium when it's adsorbed after a few hours at room temp. See the video in the link.

Something doable for the show...

There's a certain xkcd article that is rather apt:

1080995.  Sat Jun 21, 2014 10:20 am Reply with quote

Wonderful stuff, brunel. Easy to understand for simpletons like me. :-)

1081004.  Sat Jun 21, 2014 12:38 pm Reply with quote

Astronomers use the term metal to describe everything that isn't hydrogen or helium. This leads to the property metallicity is the proportion of an object's mass that isn't made up of hydrogen or helium.

1081011.  Sat Jun 21, 2014 2:40 pm Reply with quote

I think about 75% of the periodic table is metals, I wonder what proportion of known matter it is...

1081013.  Sat Jun 21, 2014 3:14 pm Reply with quote

Over 60% of the matter in the universe is reckoned to be dark matter, of the remaining 40%, 12% is thought to be made of atoms with neutrinos and photons making up the rest (28%). Overall less than 0.25% of all matter is made up of elements other than Hydrogen or Helium.

1081029.  Sat Jun 21, 2014 5:17 pm Reply with quote

Then how accurate would it be to describe that 0.25% of all remaining matter to be metal?

From Wiki:
Z Element Mass fraction in parts per million
1 Hydrogen 739,000
2 Helium 240,000
8 Oxygen 10,400
6 Carbon 4,600
10 Neon 1,340
26 Iron 1,090
7 Nitrogen 960
14 Silicon 650
12 Magnesium 580
16 Sulphur 440

Hmmm - with Iron and Magnesium waaaay down the list, I guess "not very" is the answer.

I also wonder how we demark metals/non-metals and metalloids. Are we simply defining them by their behaviour at standard temperature and pressure?

If we observe anything at high temp/low pressure - they'd be an ionic plasma. Low temp/high pressure - non-metallic superconductor? High temp/high pressure - metallic???

Perhaps have a question around arsenic? It's a little ambiguous...

1081032.  Sat Jun 21, 2014 5:25 pm Reply with quote

There are a number of properties that define metallic nature, the preference to release electrons rather than gain them, lustre, high electrical conductivity, low electrical resistivity, high thermal conductivity, generally low ionization energies until the outer shell is depleted, generally low electron affinities, and the oldest probably ductility and malleability. Non metals are just about the exact opposite, and metalloids exhibit intermediate properties, or at least some of them.

1098225.  Fri Oct 17, 2014 6:43 am Reply with quote

I went to a lecture last night on glass and part of it concerned how they make various colours - by adding different elements to it. Obsidian, for instance, is usually black because of the high iron content. One particularly nice example we were shown was the Roman Lycurgus cup, which is a sort of pearly green normally, but glows a deep red when a light source is put inside:

According to the speaker (Bob Newport from the University of Kent) this effect was created by adding gold to the glass - but in a very specific way. You can't just add it the normal way (don't ask me what that is though!) since the gold will spread out atomically and you get "ruby glass". The way this glass was made is so specific that with modern-day technology it took Mr Newport and his colleagues 6 months to make something similar - and they only managed a tiny piece of it. They don't know whether the ancients stumbled across this effect or whether they knew exactly how to create it.

Although there are a few examples of this type of gold glass (iirc), the Lycurgus cup is the only complete exhibit in the world. It is located in the British Museum.

There was also lots of interesting information about using glass to grow new bones in people - but that doesn't really fit into the 'metal' remit!

1098227.  Fri Oct 17, 2014 6:49 am Reply with quote

Isn't the Lycurgus cup marvellous? I remember standing in front of it for ages at the BM, turning the light on and off, when I was a youngster. It's a fabulous work of art, quite apart from the technological conundrum it represents.

1098231.  Fri Oct 17, 2014 7:08 am Reply with quote

It produced a definite 'ooh' from the audience :)

1098232.  Fri Oct 17, 2014 7:10 am Reply with quote

Apparently the red effect is the same effect as looking at the sunset in a polluted city. He said it was 'Mie scattering' - I may well have spelled that wrong as I'd never heard of it before!

1168407.  Sat Jan 09, 2016 7:57 am Reply with quote

lead glass has a much higher refractive index 1.5 normal glass , 1.7/8 for lead glass so used for many high art pieces


Page 1 of 2
Goto page 1, 2  Next

All times are GMT - 5 Hours

Display posts from previous:   

Search Search Forums

Powered by phpBB © 2001, 2002 phpBB Group