My favourite elements

Programme on BBC4 now about chemistry. You may or not find it exciting; I did. So I thought I would write about the elements that fascinate me. This is a personal view but it is not an uninformed one. I am a graduate chemist so here is no particular order are my favourite elements

Mercury – wonderful stuff, the only metal which is liquid at room temperature. Gallium comes close for it will melt in your hand but it’s not the same. Mercury is heavy and feels cold. When we were kids at school, we regarded it like gold. We had a wooden floor in the chemistry lab and little globules of mercury found their way into the cracks. So when the teacher wasn’t looking, we’d get them out and put them in a little bottle. It was almost a competition to see who got the most.

Of course we didn’t have all this Health & Safety stuff then, so we ignored the fact that mercury gives a poisonous vapour. Get enough of it and you go mad (Mad Hatter’s Disease) before you die.

Bromine – the only halogen that is liquid at room temperatures although even then it gives off fumes. Both the fumes and the liquid are a wonderful dark red brown colour. Saw it but rarely but it was always a great sight. Nasty stuff though.

Iodine – a solid halogen which forms into dark violet crystals at room temperature. Warm it up and it sublimes which is to say that it goes from solid to gas without passing through the intermediate liquid stage – as does solid CO2 or ‘dry ice.’ The vapour is stunningly beautiful, a deep violet/purple maybe with brown tinges. Loved playing with it in school.

If you put it into concentrated ammonia, it will form a blackish sludge of what is supposed to be nitrogen tri iodide but is actually a combination product NH3.NI3. When wet it is dormant but dry it out and it becomes one, if not the most, sensitive explosives in the world. So sensitive in fact that for all practical purposes, it is useless. When dry, you only have to touch it and it goes off with a loud bang and emits that violet iodine vapour.

So I used to make it and keep it in a test tube, wet. Again when the teacher was not looking I used to dribble the suspension in the cracks of the chemistry lab floor. Once it dried out it would crackle and splutter as you walked over it. Later I prepared some in the VIth form room. Too much with hindsight. It dried by morning and I tried to separate some before Morning Assembly. Bang and I was blinded and deaf and it took a couple of hours to recover. My next plan was to put some of the wet paste on the bottom of the legs of the headmaster’s chair in our school Assembly Hall. He always had the same routine; walk across the stage, stand in front of the chair, pull it forward and sit down. I planned to do this on the final day of term when he would address those of us leaving school for the last time. Never liked him. But one girl in class by the unfortunate name of Ruth Ellis (same as the last woman hanged in Britain) said she’s split on me. So I gave it up; you never know in this life whom you might call on for reference some day.

Later at University when I was in a hall of residence, I put some of the wet sludge in them little rubber bungs under the toilet seat. Did it late at night so it dried out by morning. Spectacular results but unfortunately, my fellow residents found out. A few nights later, they distracted me to take a telephone call in reception and while I was away, they threw all my bedding in the showers. Bastards with no sense of fun.

Potassium – a violently reactive metal in the presence of oxygen so you have to keep it in oil. It has the texture of cheese so you can cut it easily. Put a little bit in water and it whizzes about like a scalded cat with a beautiful lilac flame as it emits hydrogen. Once the teacher took a gauze container and put a bigger lump in it. He held it underwater and placed a gas jar above it to capture the emission of hydrogen. Misjudged that. The lump was too big and the water trough shattered so we kids had to jump back to avoid the floods.

Phosphorus : What a bloody element? And even if you know little about its chemistry you know about its use in matches and phosphorescence. Phosphorus will quite simply react with anything. When it gets to air, it has a go at the oxygen and thereby gives rise to its eerie glow. Think I was about 16 when my teacher allowed me to create PCl3 aka Phosphorus Trichloride, the only person allowed to do so – but then I was good. This is a dangerous experiment so it had to be carried out in an armoured glass fume cupboard. OK I followed the rules up to a point but then there was an enormous explosion and the fume cupboard was destroyed. Luckily the armoured glass buckled but did not rupture so we were spared injury. Extraction fan was destroyed too. I was quite proud of myself.

End of term report, my teacher wrote, ‘David is very good at this subject but he must learn that there is more to Chemistry than the creation of explosions.’ Personally, explosions fascinated me.

Cobalt – nothing special in its pure form, silvery, shiny but then so are many metals. It is the single metallic atom at the heart of vitamin B12 so it’s important to us. My attraction to Cobalt was the colour of its salts and their variability, some red or pink and some blue. Hydration had a lot to do with it.

But then there was an experiment that I did in the wash house down the yard which my teachers could not understand at the time and neither can I to this day. Dissolve some cobalt chloride in water in a test tube and slowly pour in hydrogen peroxide from the side as gently as possible. At the interface, you got a ring of some exquisitely purple substance maybe 3 or 4 mm thick and the oxygen bubbled from it as the hydrogen peroxide broke down. Once that finished, the purple disappeared. So what was it? No idea, nor anybody else. So probably an intermediary product which accelerated the breakdown of the peroxide.

And finally I have a denture for the loss of two teeth. It is made of cobalt and some other metal. It has served me well for over 35 years.

Hydrogen – you can’t see it, you can’t smell it yet it is the most abundant element in the universe. It is fascinating, quite fascinating. Lightest element of all and the simplest. The stuff of stars. Easy to make; just drop some light element into an acid. Loves oxygen and goes off with a pop. Its beauty lies in the fact that it is the most fundamental element of all.

Add a neutron or two and there we have atomic weapons, well hydrogen bombs.

Sulphur - now here is a pretty element, yellow mostly. Can be powdered or crystalline or even an amorphous dark brown platiscky rubbish. Was once called brimstone which I think is a pretty name. Now this is the stuff of volcanoes; its crystals can be found on the vents. Once went to get a sample on the Greek island of Nissyros with my Swiss Army knife. OK I got it but I burned my fingers with the hot sulphur dioxide venting from the orifice and the knife is stained to this day.

Versatile too. Mix it with charcoal, saltpetre (aka Sodium Nitrate) and you get gunpowder. Combine it with hydrogen and you get Hydrogen Sulphide, the so-called rotten eggs gas but then when did you last have a rotten egg by which to compare it?

Copper – this has to be the most beautiful metal of all, beating even gold in its untarnished state. What colour can you give it for there is nothing like it? It’s just copper and therefore a colour in itself. It is not surprising that such a wonderful metal has been used in coinage around the world; it is not just beautiful but it doesn’t corrode quickly although over the years when used on roofing, it acquires a green patina of oxides, sulphates and carbonates (maybe wrong there but cannot be arsed to look it up).

But that is the beauty of copper, so colourful in itself and a generator of colour in its compounds. And I adore the way it gives that intense green colour in a flame.

Magnesium – well a very light shiny metal but nothing exceptional. When alloyed with aluminium, it makes a strong metal used for car alloy wheels and other things. My first digital camera had a magnesium/aluminium body which always felt good and somehow remained cool even in the highest temperatures.

That’s all very nice but what gets to me about magnesium is the way it burns. Set alight a piece of magnesium ribbon and it burns like no other, well no other that I have ever seen. It is so brilliant that you can imagine the brightness of the stars; quite stunning. I don’t think in my life that I have ever seen something burn so bright.

Chromium – Another silvery metal. You all know it because you know about chrome plating.

For me, its attraction came not with the metal but its compounds for they are colourful. My first was potassium dichromate, an exquisite orange powder although I do believe you can get it in crystals. Then there was the oxide, well Cr203, think chromic oxide but you can’t be sure without looking it up for chromium has several valences.

Gold and Platinum – So now we come to perhaps the most famous metals of all time even for non-chemists. We can dispense with platinum easily. Another silvery metal of extraordinarily resilience but otherwise boring. Its sister elements like palladium and rhodium are just as good but attract less attention.

But then you move on to gold and you can understand why it has captivated the human race through the ages. It is simply quite beautiful. No metal like it. Heavy and yellow and does not tarnish. Gold is eternal and will last forever whatever shape into which it is formed. Prized throughout the world for centuries, it remains the metal of the gods. Seen the death mask of Tutankhamen but now I want to look upon his gold coffin.

Do I have a favourite? No. They are all wonderful in their own way. It’s just some appeal to me more than others.