Quicksilver

While we were in Slovenia, we visited the town of Idrija, where there was once a mercury mine. When I get home, I will add some pics, but I am a bit busy travelling, right now.

The element mercury has been known since the time of the ancient Romans, who obtained it from mines in Spain and Italy, and called it 'living silver', or argentum vivum. We merely translated this to get our name 'quicksilver'. The word 'quick', in this sense does not mean 'fast' or 'rapid', but 'alive', a meaning we preserve when we speak of a fetus quickening in the womb, the quick on a fingernail, or if we speak of 'the quick and the dead'.

People often assume this last phrase to mean that those who do not move fast (in a lively manner or quickly) are dead, but that just reflects the way we now interpret the term. The Greeks called it 'water silver', hydrargyros, which explains why chemists use the symbol Hg when they speak of mercury. The chemists have no element with the symbol M, which is just as well, as it leaves them free to use that letter to indicate any generic metal.

Mercury was one of the seven metals (gold, silver, iron, mercury, tin, copper and lead) known in antiquity, and directly or indirectly by associations with the various gods, these metals gave their names to the days of the week. Our Wednesday, in French, is still Mercury's day, or Mercredi. Sunday belonged to the sun, which is gold, Monday to the silvery moon, Tuesday to Mars or the Saxon Tiw, both linked to iron.

Thursday belonged to the Saxon Thor or to Jove, whose metal was tin, while Friday belonged to Venus or the Saxon Frig and copper, and leaden Saturday was the Saturn's day. The astrologer's symbol for Venus and copper was a looking-glass and gives today's biologists their 'female' symbol, while the symbol for iron and Mars, the sword and shield of Mars, is now used by biologists to indicate 'male'.

Metallic mercury was fascinating stuff, with its ability to roll around like a liquid on a flat surface, and the way it would form an amalgam with many metals, forming an alloy which is in effect a metal-metal solution. It took us rather longer to discover that mercury is one of the 'heavy metals', like lead and cadmium, and that like those, it is poisonous, damaging the nerves. People like hatters who used mercury in their work often showed signs of this damage by twitching, giving us the expression 'as mad as a hatter'.

Later, the metal was recognised as a special sort of poison which could be used to destroy certain microbes, particularly those causing venereal disease, leading to the expression 'one night with Venus led to a lifetime with Mercury'. These days, antibiotics produce a far tighter control, and GPI, the general paralysis of the insane (otherwise called tertiary syphilis) that carried off Frederick Delius in the end is never seen today, because the spirochaetes are killed by everyday antibiotics given for boring and unrelated illnesses, long before they can get that far.

Long before the Romans, the Chinese and the Hindus knew and marvelled at the liquid metal, and it has been found in Egyptian tombs dating back to 1500 BC. It occurs rarely as the metal, and more commonly as the red ore cinnabar, mercury sulfide, which breaks down when heated to make sulfur dioxide and mercury metal vapour, which can be condensed.

Mercury is shipped in iron

bottles because iron does

not form an amalgam with

mercury.

These days, we don't play with quicksilver any more, and calomel, Hg₂Cl₂, is only rarely used in medicines now. The metal is still found in a few barometers and in thermometers, mercury switches, mercury vapour lamps and a few other things, but in most of the world, uses of mercury are becoming fewer and fewer.

The one use which cannot be entirely avoided is in the ubiquitous 1.5-volt dry cell or battery. Mercury is added to the mix in these devices to prevent 'gassing', where bubbles of hydrogen gas build up inside the cell until the pressure breaks the seal, causing corrosive electrolyte to dribble out and damage some piece or other of expensive equipment. The amount of mercury used in a dry cell is now much less, but there is mercury there still, inside the dry cells that power your electrical equipment.

One reason why we use less mercury today is that we know about the damage done by a form of mercury that caused Minamata disease, a form called methyl mercury, but while that is controlled better today, metallic mercury use is out of control in the third world, where alkali plants use a process that leaks mercury into the environment.

Mercury distillation apparatus, Thames, New Zealand.

Mercury is also being misused by enthusiastic gold hunters in Brazil and in parts of Indonesia, where crushed ore is immersed in mercury to dissolve the gold into the mercury as an amalgam. Then later, the amalgam is heated, and the mercury evaporates off, leaving the gold behind.

Much of the mercury is condensed out and used again, but each heating loses more mercury into the environment, where it must be building up right now. This pollution will last a long while: in California, the fish in some of the rivers of the Sierra Nevada still have raised levels of mercury, a century and a half after the gold rush, and so do fish in the San Francisco Bay.

In 1924, the German Siemens and Halske company thought they had found the Philosopher's stone when they found that gold was 'growing' in a new type of mercury vapour lamp, and they even took out patents on the process before they worked out that their mercury contained small amounts of an impurity from an earlier use — traces of gold, in fact.

Mercury made several scientists famous, including Fahrenheit, whose real achievement was not to make a thermometer, but to find a way of cleaning the mercury so it would work in a thermometer, and Torricelli, who made the first mercury barometer. Lavoisier cracked the secret of chemical reactions by heating calx, mercuric oxide, and others followed him. The best vacuum pumps used mercury as well, and it seems fair to wonder how many scientists over the past two centuries, were killed by quicksilver.

One thing is certain: plenty of miners were killed that way...