Placeholder Image

字幕列表 影片播放

  • Nickel is element number 28 between Cobalt (27) and Copper (29)

  • Nickel has been known for a long time as an element or as a mixture with other metals

  • But it was only isolated as an element in

  • 1751 by Axel Friedrich Cronstedt in Sweden.

  • To begin with it didn't have really much use and the big breakthrough for Nickel came in the 19th century

  • when it was discovered that if you added Nickel to Steel

  • you could make very strong armor.

  • Particularly armor plates for ships so that

  • your ship was stronger than the enemies and their shells couldn't penetrate

  • About the same time, a large deposit of Nickel or Nickel ore

  • was discovered in Sudbury in Ontario in Canada so that in some ways...

  • Nickel has become a Canadian element.

  • There are also now large deposits in Russia

  • But the Canadians have become so proud of Nickel

  • Axel Friedrich Cronstedt, his portrait is on the premier medal of the Canadian Institute of Chemistry

  • It is thought that the nickel deposit in Canada probably came with a meteorite from outer space,

  • because meteorites quite often have a very high Nickel content

  • and presumably in the very distant past a massive meteorite struck what is now Canada

  • and buried itself in the Sudbury region.

  • You don't need a very large diameter meteorite to contain an awful lot of metal.

  • The big breakthrough in the refining of Nickel came in 1890

  • when the British chemist, Ludwig Mond, who was a major industrialist, had a problem in his chemical works

  • that some of the Nickel valves on his chemical plant were found to corrode - dissolve

  • And he discovered or his assistant Finker discovered

  • that this was caused by a reaction between Carbon Monoxide and Nickel.

  • In 1890 they published a key paper about the compound.

  • The compound is called Nickel Tetracarbonyl { Ni(Co)4 }

  • It consists of essential nickel atom surrounded by four Carbon Monoxide groups arranged in a tetrahedron.

  • What made this compound really unusual is that when you think about transition metals - Iron, Copper, Nickel,

  • you think of coloured salts which are solids all the time

  • Nickel Carbonyl was a liquid, it was colorless and it boils at 43° C (107.6° F)

  • So it was almost a gas at room temperature.

  • The important thing about Nickel carbonyl

  • is that you can distill it easily and if you heat it up it decomposes back into nickel and carbon monoxide

  • So it turned out to be a really good way of purifying Nickel ore

  • And Mond set up a company specifically to get nickel from the ores in Sudbury.

  • So he was reacting the ore with carbon monoxide which extracted out the nickel and in fact some of the iron -

  • both of these so-called carbonyl compounds

  • You can then separate them by distillation

  • Heat them up to decompose them and you get absolutely pure nickel and some iron as well.

  • It was then discovered that nickel was a very good catalyst for reacting organic compounds with hydrogen

  • And particularly it was discovered that you could hydrogenate vegetable oils, sort of cooking oils that you use.

  • And these oils have Carbon-Carbon double bonds.

  • If you react this with hydrogen, the melting point of the oils increases

  • so the material becomes more like butter

  • And this is how you make margarine, by reacting vegetable oil with hydrogen and the Nickel is the Catalyst.

  • The hydrogen is absorbed onto the surface of Nickel the organic compound is also absorbed onto the surface

  • and when the molecules are held there, the hydrogen can transfer from the nickel onto the carbon of the double bond.

  • [Music]

  • I was very keen to do a big experiment demonstration in this video,

  • and I wanted to do it with a material called Raney Nickel.

  • Murray Raney was an American chemist working on the hydrogenation of fats trying to make a better catalyst

  • and the problem with the catalyst is, because it is solid and the molecules are absorbing on the surface

  • the bigger the surface area within reason, the better the catalyst.

  • So he needed some way of dividing up the nickel

  • so it was in very small particles, so it had a very large surface area

  • And he hit on the idea of mixing molten aluminium and molten nickel - these melted metals

  • And they mix when they are liquid, but when they solidify they separate

  • So you end up with a lump of aluminium with tiny bits of Nickel embedded in the solid

  • rather like currants or cherries in the cake

  • [Neil opens the can]

  • You can then put these mixed nickel aluminum pellets into sodium hydroxide

  • [Music + experiment sounds]

  • The sodium hydroxide dissolves the aluminium,

  • rather like we've done before with Coke cans

  • and they leave the nickel quite untouched

  • But they come out like removing the cherries from the cake

  • and they have a very low surface area.

  • So now my experiment.

  • I had read that Raney nickel is Pyrophoric, it reacts with oxygen in the air and bursts into flames

  • So I went to talk to my colleagues in organic chemistry who use Raney nickel

  • and you buy it as a slurry so it's wet to avoid it bursting into flames.

  • So I got a bottle which looked a bit old, but I was assured was probably okay

  • And I persuaded Neil to pour it onto a filter paper

  • And so what I expected was that it would dry out

  • and then you would be left with this dried tiny particles of Nickel which would

  • absorb oxygen, start burning, heat up more and more and burst into spectacular flames

  • Unfortunately, it didn't. In fact when Neil eventually set fire to the filter paper...

  • and the nickel didn't seem to burn

  • Clearly we had a dud batch

  • I think that the air had got in and slowly dissolved in the water and reacted over a period of months

  • and oxidized the nickel so probably what we had was some form of nickel oxide

  • But they are all fairly black in color so you can't really tell what you've got

  • So I rushed off and found another professor who had a much fresher sample

  • and he came down with his sample

  • and he told us we had to dry it on the hot plate

  • and he got quite worried, thought we'd used rather a lot of nickel.

  • We heated it up, we had all the cameras

  • the GoPro, the thermal camera, Brady standing there

  • so excited, and eventually...

  • it glowed slightly...

  • And what this demonstrates, is that sometimes

  • what chemists tell you about reactions are not always what happens in the lab.

  • However you've got to imagine

  • that if you're making margarine on a huge scale...

  • Tens of thousands of tons, and have got a huge amount of Raney nickel

  • then probably you can get quite a serious fire.

  • But we don't have that much Raney nickel, and we don't want a serious fire.

  • So, well, first of all let's look at some nickel

  • Neil has produced some Nickel pellets

  • So these are just labelled as general-purpose nickel

  • They're lumps of nickel. Quite a few chemists like to use Nickel spatulas

  • because they are more resistant to strong acids than stainless steel ones.

  • You can have over here...

  • This is quite nice. This is a...

  • Gauze that is made of very fine Nickel wires.

  • I think this one is designed for Electrochemistry so you can get a very high surface area.

  • Nickel has also been used quite often for electroplating in the days when cars had shiny bumpers

  • I can't remember what Americans called bumpers...

  • Fenders!

  • And these consisted of steel, which were plated with nickel and on top of the nickel, was chromium.

  • So the Chromium gave a nice shiny look but the Nickel bonded them together

  • Nickel has very colorful salts.

  • and our undergraduates, in their first year do a very nice experiment

  • where they take Nickel Chloride { NiCl4 } that is green

  • And they react this with ammonia, so that each nickel atom is surrounded by six ammonia atoms.

  • The Nickel ammonia complex { [Ni(Nh3)6]2+ } is a nice purple color

  • They then have to do a separate experiment to measure how much nickel is in the sample

  • to see if they made it properly.

  • They do this by dissolving up their nice purple compound

  • adding an organic compound called dimethyl glyoxime

  • which binds to the nickel and forms an insoluble red precipitate

  • which they filter off and weigh, so they can see how much nickel there is in their compound.

  • So in a single experiment...

  • they have gone from green to purple to red.

  • We're not showing you the experiment because then our students might cheat!!

  • So you'll have to come as a student to do it yourself

  • Then Neil thought about it.

  • He realized that as the water was evaporating and the individual particles of nickel got dry

  • each of them oxidized so you never had the whole mass going off at once

  • So what he decided

  • was to put the wet Raney nickel in a vacuum desiccator

  • This is a vessel which you can pump out all the air

  • And you're pumping on it of course the water also evaporates but the nickel is dried in a vacuum

  • so there's no oxygen for it to react with

  • So when he opened the tap, the air, containing the oxygen rushed in...

  • And all the nickel reacted at the same time and produced quite a satisfying whoosh

  • [Brady:] We've made videos about every element on the periodic table.

  • If you'd like to watch them in order, I'll put a link on the screen and in the video description

  • There's a playlist of them all one to 118. Might take you a little while...

  • We're constantly updating these videos with new ones like the nickel video you just watched.

  • And in fact we've filmed so much about Nickel there's some leftovers.

  • If you'd like to watch them, I'm also linking to the extra footage.

  • You can go and check out even more details the professor had to share.

Nickel is element number 28 between Cobalt (27) and Copper (29)

字幕與單字

影片操作 你可以在這邊進行「影片」的調整,以及「字幕」的顯示

C1 高級

鎳 - 視頻週期表 (Nickel - Periodic Table of Videos)

  • 37 3
    林宜悉 發佈於 2021 年 01 月 14 日
影片單字