All About the Element Mercury

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Podcast Transcript

Since the dawn of human history, humans have been aware of a seemingly miraculous substance. It was a substance that had the same color as silver, but unlike silver, it wasn’t a solid. It was a liquid. 

Ancient people used this substance as a medicine and as an elixir for long life, something which they got absolutely wrong. 

Learn more about the element mercury, its history, and its unique properties on this episode of Everything Everywhere Daily.

What we know today as Mercury was one of the Metals of antiquity. These were metals that the ancients knew about because they could be found in their base elemental form. 

In addition to Mercury, there was Iron, Copper, Gold, Silver, Lead, and Tin. 

Needless to say, Mercury was very different from the other six. While it was known, there weren’t nearly as many practical uses for it as there were for other metals. 

We should start with the tale of the tape for Mercury. 

Mercury has an atomic number of 80 and thus has 80 protons in its nucleus. This put is right after platinum and gold on the periodic table. 

The big thing about Mercury, however, and the one thing that everyone knows, if they know anything about Mercury, is its low melting point, especially for a metal. 

Mercury has a melting point of 234.3210 K ?or ?38.8° Celcius or ??37.8° Fahrenheit. Its boiling point is 357 °C or ?674 °F. 

That means that so long as it isn’t bound to some other element in the form of a chemical compound and it is in its elemental form, Mercury will be a liquid at almost every temperature we will experience it at. 

Mercury is rather rare in the Earth’s crust but far from the rarest. It is more abundant than silver, gold, or platinum. 

However, because it doesn’t tend to bind with most other elements where it is found, it can be found in high concentrations. 

While ancient people knew of Mercury, it wasn’t as if they discovered pools of liquid Mercury. Almost all mercury from the ancient world came from a mineral known as Cinnabar, or Mercury Sulfide. It has a chemical formula of HgS. 

Cinnabar is a very bright red and was the basis for the pigment known as vermillion. Many ancient people used Cinnabar directly as a cosmetic, as an ink, and in dyes. Many ancient cultures, including China, Egypt, Rome, the Olmec, Maya, and others, were known to us it.

Extracting Mercury from Cinnabar was pretty easy, especially compared to how difficult it was to extract metals from other ores. 

There were recipes for cold Mercury extraction, which involved pulverizing Cinnabar and copper in the presence of an acid, usually vinegar. 

You can also extract Mercury from Cinnabar by heating it, which is how it was extracted at a larger scale by the Romans. If you heat Cinnabar, Mercury vapor will be released, which can then be condensed, similar to how alcohol is distilled. 

Evidence of Mercury has been found all over the world. The earliest evidence of liquid Mercury was found in Egyptian tombs dating back to 1500 BC. 

In one of the most incredible stories from ancient history, the first Chinese Emperor Chin supposedly had a tomb built with a map of his territories on the floor. All of the water was represented by flowing liquid Mercury. 

The tomb, if it exists, hasn’t yet been discovered, but if it does exist, it might be located somewhere near his Terra Cotta Warriors of Xi’an. 

Likewise, in 2014, a large deposit of liquid Mercury was found underneath the “Temple of the Feathered Serpent” in Teotihuacan, Mexico.

However, these uses of Mercury were mostly ornamental. The strange liquid properties of Mercury gave it mystical attributes, which is why it was used so often by alchemists. 

Emperor Chin sought to achieve immortality, and he was given treatments by his doctors, who believed that Mercury was the key to good health. 

Emperor Chin’s doctors couldn’t have been more wrong. Not only does Mercury not promote good health, it is actually quite toxic. 

The Romans probably did more Mercury mining than any other civilization in history at that point, and they observed that working with Mercury often resulted in illness and death. This is known as Mercurialism.

The word Mercury is of Latin origin, and it is named after the planet Mercury, which is named after the Roman god of the same name. The association of the element Mercury with the planet has to do with speed.  Mercury is the fastest planet, and Mercury was the god of messages and journeys. The element Mercury, often known as quicksilver, was associated with speed because of how it would move.

The chemical symbol for Mercury is Hg, which comes from the Romanized Greek word hydrargyrum, which just means water-silver.

One of the big advances in Mercury was the discovery in the 16th century that Mercury could be used to process silver. Dubbed the Patio Process, it was developed by Bartolomé de Medina in Pachuca, Mexico, in 1554.

The Patio Process used Mercury to create an amalgam with silver. An amalgam is a metallic alloy with Mercury. Mercury is particularly fond of creating amalgams with gold and silver, so it proved to be an excellent way to extract silver from ore. 

The Patio Process largely replaced smelting in the production of silver. 

Given the large amounts of silver the Spanish were mining in the New World, it required large amounts of Mercury for the Patio Process. 

The primary source of Mercury was the mine in Almaden, Spain, which was the largest deposit of Mercury in the form of Cinnabar on Earth. The mine in Almaden had been in service for over 2000 years, but it was starting in the 16th century that the mine saw its greatest output.

I actually had the pleasure of visiting the mine in Almaden in 2018. The mine hasn’t been in operation since 2002, and it was opened to the public in 2006.  Today, it and another Mercury mine in Slovenia are World Heritage Sites. 

The Mercury produced in Almaden was shipped to the New World to process the silver, which was then shipped back to Spain. 

The use of Mercury for the amalgamation of silver and gold was by far the largest use of Mercury for centuries. However, there were eventually more uses for the unique material found. 

In 1643, the Italian scientist Evangelista Torricelli invented a device to measure air pressure. It was a U-shaped tube that was closed on one end and open on the other, with a liquid in the middle that would move based on the pressure from the open end of the tube. 

Water was originally used as the liquid, but it required an enormous tube. With heavier Mercury, it only required a tube a fraction of the size.

In 1714, Daniel Gabriel Fahrenheit, a Polish physicist living in the Netherlands, invented a device that consisted of mercury in a closed tube that would change its level based on temperature. The mercury-in-glass thermometer was the most accurate temperature-measuring device created at the time. 

In the 19th century, mercuric nitrate was used to produce a superior felt that was used in hats. The constant exposure to Mercury vapors by hat makers often led to mercury poisoning. This is where the phrase “mad as a hatter” came from. 

The 20th century saw even more uses for Mercury. One of the most important uses was in electric devices. The fact that Mercury was both an electrical conductor and a liquid allowed it to be used in many applications. 

One of the biggest uses was in electrical switches. Depending on the position of the switch, Mercury could flow from one end of the switch to another where there were two electrodes, and the Mercury would complete the circuit. 

Mercury vapor fluorescent lights were developed, which were more efficient than incandescent lights. When an electrical current passes through Mercury vapor, it produces ultraviolet light. When the UV rays hit the phosphor coating in the tube, it causes it to fluoresce.

In the mid-20th century, Mercury was used in non-rechargeable batteries that were very popular during and immediately after WWII. 

The biggest use for Mercury during the 20th century was for the Chloralkali process.  The Chloralkali process was used to separate chlorine and sodium in a brine solution. 

Amalgams of Mercury, usually with silver, tin, and copper, have been used in dentistry to fill cavities. 

Mercury fulminate is an explosive that was often used as a primer in bullets. 

On top of all of this, Mercury was used in a host of chemical products, including paints, cleaning products, 

One of the most innovative uses of Mercury was as a mirror of a telescope.  Because of its silvery reflective surface, Mercury could be used as a telescope mirror. 

Isaac Newton discovered that if you rotated a liquid, the surface of the liquid would form a parabola as the edges of the liquid rose up along the rim. 

If you had a large container full of Mercury and spun it, you would be able to create a very powerful lens. 

This is exactly what some astronomers did. They have created very large aperture telescopes using Mercury at a fraction of the cost of traditional telescopes. 

There is, of course, a massive downside to this method. You can’t really point a liquid mirror in any direction you want. In fact, there is only one direction you can point it, straight up. 

The University of British Columbia’s massive 6-meter telescope, known as the Large Zenith Telescope, allows for a massive mirror at a fraction of the cost of traditional telescopes. 

Mercury was a somewhat common ingredient in many different industrial and commercial products throughout the 20th century. 

However, there was a problem. While Mercury poisoning had been known for centuries, medical professionals began to understand the dangers of Mercury poisoning. 

I’m old enough that I can remember mercury thermometers and, in a few cases, how they would break, and you could play with Mercury. It turned out this was an incredibly dumb thing to do. 

Mercury can quite easily vaporize, which means even if you work with liquid Mercury, you run the risk of Mercury poisoning. All of the Mercury in so many products raised the level of Mercury poisoning for everyone in the population. 

Moreover, as a heavy toxic metal that could uniquely vaporize compared to other metals, Mercury could accumulate life forms that ingested it. This was especially problematic in fish as Mercury would accumulate at higher trophic levels in the food chain. 

Lower levels of animals may only have small amounts of Mercury. However, as those fish were eaten, Mercury levels would accumulate.  Fish like tuna can have high levels of Mercury, as can dolphins and whales. 

In 2008, actor Jeremy Piven was diagnosed with Mercury poisoning after he was found with Mercury levels five to six times higher than normal. It turned out he had been eating sushi twice a day, every day, for twenty years. 

Mercury is a fascinating substance. Its heavy weight and the fact that it is a liquid at room temperature make it extremely useful for certain applications. 

However, it is also a highly toxic substance. It is so toxic that it has been removed from most common products. A fact that wouldn’t have surprised the people who worked with mercury almost 2000 years ago.