16 January: Lead

Today is Lead Day in the French Revolutionary Calendar. Some things you may not know about this heavy metal.

1. The chemical symbol for lead is Pb, an abbreviation of its Latin name plumbum. The English words "plumbing", "plumber", "plumb", and "plumb-bob" derive from the same Latin root.
2. The atomic number of lead is 82. This is the highest atomic number of all the stable elements. Anything above lead is therefore radioactive, although bismuth (atomic number 83) has such a long half life (billions of years) that it is stable for all intents and purposes.
3. The melting point of lead is 600.61 K (327.46 °C, 621.43 °F) and the boiling point is 2022 K (1749 °C, 3180 °F).
4. Up until the 17th century, people didn't distinguish lead from Tin. Lead was called plumbum nigrum (literally, "black lead"), while tin was called plumbum candidum (literally, "bright lead").
5. The Romans used lead extensively. They used it to make Water pipes, often stamped with the emperor's insignia, to make pins to hold large blocks of limestone in buildings together, and even used lead acetate, (also known as sugar of lead) to sweeten their Wine. The latter is often put forward as an explanation for why so many Roman emperors went mad and the empire eventually declined.
6. Lead is toxic and ingesting it causes Brain and Blood disorders. We know that now, and so use is controlled, but as well as the Romans putting it in their wine, historically lead was often used in highly dangerous ways. It was used in cosmetics, in particular for geishas and women who wanted their faces to look pale and white. It was used to make cider presses in Devon and this gave rise to a disease called "Devon colic", now known to be a form of lead poisoning. It was even an ingredient in the paint used for children's toys.
7. Its uses include small arms ammunition (hence, "I'll fill you fulla lead"). Because it is dense and doesn't corrode, lead is used for the ballast keel of sailboats and for scuba divers' weight belts. More than half of the US lead production goes into the production of car batteries. It is effective at stopping gamma rays, and x-rays, so is used in shielding from radiation and hiding things from superheroes!
8. One thing it isn't used for, contrary to popular belief, is making Pencils. Lead pencils have no lead in them. The stuff inside pencils is graphite. When pencils were first produced, the particular type of graphite used was called plumbago (literally act for lead, or lead mockup).
9. In alchemy, lead was thought to be the oldest metal and was associated with the planet Saturn. Alchemists used Saturn's symbol (the scythe, ♄) to refer to lead.
10. At current use rates, the supply of lead is estimated to run out in 42 years. Or less, given population growth (18 years is one recent estimate). Or more, because the rate of recycling has gone up.