New formula for fast, abundant hydrogen production may help power fuel cells.

Scientists in Lyon, a French city famed for its cuisine, have discovered a quick-cook recipe for copious volumes of hydrogen (H2).

The breakthrough suggests a better way of producing the  that propels rockets and energizes battery-like fuel cells. In a few decades, it could even help the world meet key energy needs—without carbon emissions contributing to the greenhouse effect and climate change.

It also has profound implications for the abundance and distribution of life, helping to explain the astonishingly widespread microbial communities that dine on hydrogen deep beneath the continents and seafloor.

Describing how to greatly speed up nature’s process for producing hydrogen will be a highlight among many presentations by Deep Carbon Observatory (DCO) experts at the American Geophysical Union‘s annual Fall Meeting in San Francisco Dec. 9 to 13.

The DCO is a global, 10-year international science collaboration unraveling the mysteries of Earth’s inner workings—deep life, energy, chemistry, and fluid movements.

Muriel Andreani, Isabelle Daniel, and Marion Pollet-Villard of University Claude Bernard Lyon 1 discovered the quick recipe for producing hydrogen:

In a microscopic high-pressure cooker called a diamond anvil cell (within a tiny space about as wide as a pencil lead), combine ingredients: aluminum oxide, water, and the mineral olivine. Set at 200 to 300 degrees Celsius and 2 kilobars pressure—comparable to conditions found at twice the depth of the deepest ocean. Cook for 24 hours. And voilà.

Dr. Daniel, a DCO leader, explains that scientists have long known nature’s way of producing hydrogen. When water meets the ubiquitous mineral olivine under pressure, the rock reacts with oxygen (O) atoms from the H2O, transforming olivine into another mineral, serpentine—characterized by a scaly, green-brown surface appearance like snake skin. Olivine is a common yellow to yellow-green mineral made of magnesium, iron, silicon, and oxygen.

The process also leaves hydrogen (H2) molecules divorced from their marriage with oxygen atoms in water.

The novelty in the discovery, quietly published in a summer edition of the journal American Mineralogist, is how aluminum profoundly accelerates and impacts the process.

Finding the reaction completed in the diamond-enclosed micro space overnight, instead of over months as expected, left the scientists amazed. The experiments produced H2 some 7 to 50 times faster than the natural “serpentinization” of olivine.

Over decades, many teams looking to achieve this same quick hydrogen result focused mainly on the role of iron within the olivine, Dr. Andreani says. Introducing aluminum into the hot, high-pressure mix produced the eureka moment.

Dr. Daniel notes that aluminum is Earth’s 5th most abundant element and usually is present, therefore, in the natural serpentinization process. The experiment introduced a quantity of aluminum unrealistic in nature.

Jesse Ausubel, of The Rockefeller University and a founder of the DCO program, says current methods for commercial hydrogen production for fuel cells or to power rockets “usually involve the conversion of methane (CH4), a process that produces the greenhouse gas carbon dioxide (CO2) as a byproduct. Alternatively, we can split water molecules at temperatures of 850 degrees Celsius or more—and thus need lots of energy and extra careful engineering.”

“Aluminum’s ability to catalyze hydrogen production at a much lower temperature could make an enormous difference. The cost and risk of the process would drop a lot.”

“Scaling this up to meet global energy needs in a carbon-free way would probably require 50 years,” he adds. “But a growing market for hydrogen in fuel cells could help pull the process into the market.”

“We still need to solve problems for a hydrogen economy, such as storing the hydrogen efficiently as a gas in compact containers, or optimizing methods to turn it into a metal, as pioneered by Russell Hemley of the Carnegie Institution‘s Geophysical Laboratory, another co-founder of the DCO.”

Deep energy, Dr. Hemley notes, is typically thought of in terms of geothermal energy available from heat deep within Earth, as well as subterranean fluids that can be burned for energy, such as methane and petroleum. What may strike some as new is that there is also chemical energy in the form of hydrogen produced by serpentinization.

At the time of the AGU Fall Meetings, Dr. Andreani will be taking a lead role with Javier Escartin of the Centre National de la Recherche Scientifique in a 40-member international scientific exploration of fault lines along the Mid-Atlantic Ridge. It is a place where the African and American continents continue to separate at an annual rate of about 20 mm (1.5 inches) and rock is forced up from the mantle only 4 to 6 km (2.5 to 3.7 miles) below the thin ocean floor crust. The study will advance several DCO goals, including the mapping of world regions where deep life-supporting H2 is released through serpentinization.

Aboard the French vessel Pourquoi Pas?, using a deep sea robot from the French Research Institute for Exploitation of the Sea (IFREMER), and a deep-sea vehicle from Germany’s Leibniz Institute of Marine Sciences (GEOMAR), the team includes researchers from France, Germany, USA, Wales, Spain, Norway and Greece.

Notes Dr. Daniel, until now it has been a scientific mystery how the rock + water + pressure formula produces enough hydrogen to support the chemical-loving microbial and other forms of life abounding in the hostile environments of the deep.

With the results of the experiment in France, “for the first time we understand why and how we have H2 produced at such a fast rate. When you take into account aluminum, you are able to explain the amount of life flourishing on hydrogen,” says Dr. Daniel.

Indeed, DCO scientists hypothesize that hydrogen was what fed the earliest life on primordial planet Earth—first life’s first food.

And, she adds: “We believe the serpentinization process may be underway on many planetary bodies—notably Mars. The reaction may take one day or one million years but it will occur whenever and wherever there is some water present to react with olivine—one of the most abundant minerals in the solar system.”

Enigmatic evidence of a deep subterranean microbe network

Meanwhile, the genetic makeup of Earth’s deep microbial life is being revealed through DCO research underway by Matt Schrenk of Michigan State University, head of DCO’s “Rock-Hosted Communities” initiative, Tom McCollom of the University of Colorado, Boulder, Steve D’Hondt of the University of Rhode Island, and many other associates.

At AGU, they will report the results of deep sampling from opposite sides of the world, revealing enigmatic evidence of a deep subterranean microbe network.

Using DNA, researchers are finding hydrogen-metabolizing microbes in rock fractures deep beneath the North American and European continents that are highly similar to samples a Princeton University group obtained from deep rock fractures 4 to 5 km (2.5 to 3 miles) down a Johannesburg-area mine shaft. These DNA sequences are also highly similar to those of microbes in the rocky seabeds off the North American northwest and northeastern Japanese coasts.

“Two years ago we had a scant idea about what microbes are present in subsurface rocks or what they eat,” says Dr. Schrenk. “Since then a number of studies have vastly expanded that database. We’re getting this emerging picture not only of what sort of organisms are found in these systems but some consistency between sites globally—we’re seeing the same types of organisms everywhere we look.”

“It is easy to understand how birds or fish might be similar oceans apart, but it challenges the imagination to think of nearly identical microbes 16,000 km apart from each other in the cracks of hard rock at extreme depths, pressures, and temperatures” he says.

A hydrogen bubble is quickly released as olivine meets water and aluminum oxide under extreme pressure and heat. Credit: Muriel Andreani, University of Lyon-1

“In some deep places, such as deep-sea hydrothermal vents, the environment is highly dynamic and promotes prolific biological communities,” says Dr. McCollom. “In others, such as the deep fractures, the systems are isolated with a low diversity of microbes capable of surviving such harsh conditions.”

“The collection and coupling of microbiological and geochemical data made possible through the Deep Carbon Observatory is helping us understand and describe these phenomena.”

How water behaves deep within Earth’s mantle

Among other major presentations, DCO investigators will introduce a new model that offers new insights into water / rock interactions at extreme pressures 150 km (93 miles) or more below the surface, well into Earth’s upper mantle. To now, most models have been limited to 15 km, one-tenth the depth.

“The DCO gives a happy twist to the phrase ‘We are in deep water’,” says researcher Dimitri Sverjensky of Johns Hopkins University, Baltimore MD.

Dr. Sverjensky’s work, accepted for publication by the Elsevier journal Geochimica et Cosmochimica Acta, is expected to revolutionize understanding of deep Earth water chemistry and its impacts on subsurface processes as diverse as diamond formation, hydrogen accumulation, the transport of diverse carbon-, nitrogen- and sulfur-fed species in the mantle, serpentinization, mantle degassing, and the origin of Earth’s atmosphere.

In deep Earth, despite extreme high temperatures and pressures, water is a fluid that circulates and reacts chemically with the rocks through which it passes, changing the minerals in them and undergoing alteration itself—a key agent for transporting carbon and other chemical elements. Understanding what water is like and how it behaves in Earth’s deep interior is fundamental to understanding the deep carbon cycle, deep life, and deep energy.

This water-rock interaction produces valuable ore deposits, creates the chemicals on which deep life and deep energy depend, influences the generation of magma that erupts from volcanoes—even the occurrence of earthquakes. Humanity gets glimpses of this water in hot springs.

Says Dr. Sverjensky: “The new model may enable us to predict water-rock interaction well into Earth upper mantle and help visualize where on Earth H2 production might be underway.”

The DCO is now in the 5th year of a decade-long adventure to probe Earth’s deepest geo-secrets: How much carbon is stored inside Earth? What are the reservoirs of that carbon? How does carbon move among reservoirs? How much carbon released from Earth’s deep interior is primordial and how much is recycled from the surface? Are there deep abiotic sources of hydrocarbons? What is the nature and extent of deep microbial life? And did deep Earth chemistry play a role in life’s origins?

The $500 million global collaboration is led by Dr. Robert Hazen, Senior Staff Scientist at the Geophysical Laboratory, Carnegie Institution of Washington.

Says Dr. Hazen: “Bringing together experts in microbes, volcanoes, the micro-structure of rocks and minerals, fluid movements, and more is novel. Typically these experts don’t connect with each other. Integrating such diversity in a single scientific endeavor is producing insights unavailable until the DCO.”

Ninety percent or more of Earth’s carbon is thought to be locked away or in motion deep underground, he notes, a hidden dimension of the planet as poorly understood as it is profoundly important to life on the surface.


New Dangerous Strain Of HIV Discovered

Researchers have discovered a new, more aggressive strain of the human immunodeficiency virus (HIV) that develops into AIDS much more quickly than other strains, Medical News Today reported.

In a new study published in the Journal of Infectious Diseases, scientists detailed the new strain as a “recombinant” virus – a hybrid of two virus strains. Called A3/02 – a cross between the 02AG and A3 viruses – the strain can develop into AIDS in just five years after first infection – one of the shortest time periods for HIV-1 types.

“Recombinants seem to be more vigorous and more aggressive than the strains from which they developed,” said first author Angelica Palm, a doctoral candidate at Lund University in Sweden.

So far, the A3/02 strain has only been seen in Guinea-Bissau, West Africa, but other studies have shown that recombinants are spreading more quickly across the globe.

“HIV is an extremely dynamic and variable virus. New subtypes and recombinant forms of HIV-1 have been introduced to our part of the world, and it is highly likely that there are a large number of circulating recombinants of which we know little or nothing,” said senior author Patrik Medstran, professor of clinical virology at Lund University. “We therefore need to be aware of how the HIV-1 epidemic changes over time.”

[​IMG] ​


Detecting Cancer with Digital PCR.

Could dPCR be a diagnostics dark horse?

Detecting Cancer with Digital PCRDigital PCR can carry out a single reaction within a single sample, but the sample is separated into a large number of partitions, and the reaction is carried out in each partition individually. [© anyaivanova –]
  • Over the past few years, scientists from a variety of disciplines have applied digital PCR (dPCR) as a potentially useful tool for breast cancer screening, measuring latent HIV reservoirs in patients, and diagnosing hospital-acquired and sexually transmitted infections, among others. Digital PCR and variations on it offer a new approach to nucleic acid detection and quantification.

    Similarly to real-time quantitative PCR (qRT-PCR or qPCR), dPCR carries out a single reaction within a single sample. However, in dPCR the sample is separated into a large number of partitions, and the reaction is carried out in each partition individually. This separation, proponents of the technology say, allows a more reliable collection and sensitive quantitation of nucleic acids.

    And a recent advance in dPCR, droplet digital PCR (ddPCR™), can measure absolute quantities by counting nucleic acid molecules encapsulated in discrete, volumetrically defined, water-in-oil droplet partitions. The technology is said to offer advantages in the field of liquid biopsies, enabling circulating nucleic acids (cfDNA) and circulating tumor cells (CTCs) to be measured in blood. The technique can also detect rare tumorigenic mutations in a high background of “normal” DNA, routinely down to 0.01% and often further.

    But although simple in theory and principle, the technique’s implementation was not, as it was carried out in commercially available 384-well plates with five microliters per partition, requiring large volumes of reagents.

  • The dPCR Arena

    Advanced nanofabrication and microfluidics technologies have now been incorporated into systems that produce hundreds to millions of nanoliter- or even picoliter-scale partitions, but to date, few companies have jumped into the dPCR arena, offering instrumentation platforms that perform dPCR, or both qPCR and dPCR in various configurations.

    In 2006, Fluidigm became the first company to commercialize dPCR. Currently it offers two systems that mix samples with reagents, partition the reaction mixture, and perform thermocycling and read results within each partition. The systems use chips containing microfluidics and valves that partition samples into about 800 reactions, with either 12 or 48 samples per chip.

    Life Technologies, through its 2009 acquisition of BioTrove, now offers two machines that can be used for both digital PCR and qPCR, the OpenArray and QuantStudio 12K Flex. These mix samples with reagents, load mixtures into reaction chambers, run amplification cycles and monitor reactions as they occur. The machines rely on plates that are roughly the size of microscope slide boards with nano-sized holes; capillary forces and careful placement of hydrophilic and hydrophobic surfaces hold samples in place.

    Life Technologies has also introduced the QuantStudio 3D Digital PCR System. This system, which began shipping in June 2013, is built around a high-density, nanofluidic silicon chip that enables up to 20,000 data points. The system’s chip-based approach is meant to simplify workflow, decreasing the number of hands-on steps needed to begin experiments, and reducing the risks of sample contamination and loss of DNA.

    Companies like Bio-Rad and RainDance now market instruments with many more partitions than previously possible using plates with nano-sized holes. In droplet digital PCR, reaction chambers are separated not by the walls of a well but by carefully titrated emulsions of oil, water, and stabilizing chemicals. Samples are put into a machine where they are mixed with all the necessary reagents and dispersed into tiny droplets. The droplets for each sample are transferred into tubes that can be placed in a thermocycler for PCR. Afterward, the tubes are transferred to a droplet-reading machine, which functions like a flow cytometer to analyze each droplet for whether or not a reaction has occurred.

    RainDance, for example, has developed a patented way to put reagents inside of picoliter-sized droplets to encapsulate biology one droplet at a time. Currently, single nucleic acids are placed inside of the droplets. This creates a single-plex PCR reaction inside of each droplet and, the company says, droplets can be generated using one of RainDance’s commercial instrument systems at up to 10,000 per second.

    In an email to GEN, George Karlin-Neumann, Ph.D., director of scientific affairs at the Digital Biology Center, Bio-Rad clarified distinctions between qPCR and his company’s QX200 Droplet Digital PCR™, explaining that either system can quantitate DNA or RNA targets with either Taqman 5’ nuclease assays or fluorescent DNA-binding dyes (SYBR for qPCR, and EvaGreen for ddPCR) run in suitable Master Mixes.

    But, he explained, ddPCR divides a sample reaction into many thousands of small, uniformly sized droplets where each may or may not contain a target template of interest. After thermocycling to endpoint in a standard 96-well plate and thermocycler, the droplets in each well are read and counted in a droplet flow cytometer (or reader) to determine which droplets have the target (“positive” droplets) and which do not (“negative” droplets). The fraction of positive droplets reflects the number of target molecules in the reaction volume, thus yielding the concentration measurement sought.

  • dPCR and Cancer Detection

    And researchers have adopted dPCR for numerous applications including for analysis of several parameters in cancer patients. In study results published in Clinical Cancer Research last March, researchers from the Royal Marsden Hospital in London described their adaptation of ddPCR to determine the presence of oncogenic amplification through noninvasive analysis of circulating free plasma DNA and exemplify this approach by developing a plasma DNA digital PCR assay for HER2 copy number.

    Because HER2 copy number in digital PCR is assessed relative to a reference gene, the investigators used EFTUD2, a gene within the ERBB2 locus found not to co-amplify with HER2 and not subject to normal copy-number variations.

    Using the Bio-RAD QX100 ddPCR system, the researchers found that 64% of patients with HER2-amplified cancers were classified as digital PCR HER2-positive and 94% of patients with HER2-nonamplified cancers were classified as HER2-negative by the assay, giving a positive and negative predictive value of 70% and 92%, respectively.

    The authors concluded that “digital PCR of plasma DNA has high accuracy in the determination of HER2 status,” and that the approach of analyzing of plasma DNA with digital PCR has the potential to screen for the acquisition of HER2 amplification in metastatic breast cancer. “This approach could potentially be adapted to the analysis of any locus amplified in cancer,” they concluded.

    And last September, scientists working at Fred Hutchinson Cancer Research Center, demonstrated that ddPCR technology could be used to precisely and reproducibly quantify microRNA (miRNA) in plasma and serum over the course of different days, potentially allowing further development of miRNA and other nucleic acids as circulating biomarkers.

    Under active study as blood-based biomarkers for cancer and other diseases, miRNA measurements in blood samples have been plagued by unacceptably high interday variability, obviating their use as reliable blood-based biomarkers.

    “In the field of circulating microRNA diagnostics, droplet digital PCR enables us to finally perform biomarker studies in which the measurements are directly comparable across days within a laboratory and even among different laboratories,” said Muneesh Tewari, M.D., Ph.D., associate member in the Human Biology Division at the Fred Hutchinson Cancer Research Center and lead author of the study.

    And Dr. Karlin-Neumann says that ddPCR is “en route to being introduced into clinical practice in a number of areas.” Though, he notes, the “only CLIA lab I know of that currently offers a ddPCR-based test is the University of Washington’s Clinical Laboratory, which offers a ddPCR-based test for detection of chromosomally integrated HHV-6 virus in transplant patients.”

    Other labs, he says, that are in the process of developing clinical tests for detection of residual disease in leukemia patients with BCR-ABL translocations include that of Alec Morley, M.D., a pioneer of digital PCR. Dr. Karlin-Neumann also cites the work of Hanlee Ji, M.D., who is measuring copy-number variations by ddPCR in FFPE and cell-free plasma DNA to assess whether gastric and other cancer patients have amplifications in oncogenes that would make them amenable to one of a growing number of targeted therapies.

    Importantly, Dr. Karlin-Neumann pointed out that it’s still too early, regardless of the platform used, to be attempting to detect cancer in naïve patients not already known to have cancer since “we do not have the clinical experience to know what changes to look for and what thresholds are meaningful.”

    And he notes, until recently, there have not been technologies that allowed us to detect and quantitate below ~1% mutant abundance in either mixed tissue biopsies or in cfDNA in plasma or serum. ddPCR is demonstrating that it is capable of lowering this limit to as low a ~0.01% in a single ddPCR reaction well, and where more material is available, this can be lowered further by use of multiple wells. Similarly, fractional changes in oncogenic amplifications and deletions can be tested with ddPCR in both solid tumors and in cfDNA.

    And a team of scientists at the University of California, Berkeley says it has developed a bead-based, microfluidic digital PCR technology and demonstrated its ability to quantitatively measure cancer-related translocation mutations at extremely low levels and subsequently sequence single mutated clones.

    The scientists believe that their technology has advantages over commercial emulsion-based droplet digital PCR platforms, such as those offered by Bio-Rad and RainDance Technologies, because it enables downstream sequencing analysis following the digital PCR analysis step.

    But is this capability in demand? A RainDance spokesperson told PCR Insider that the company’s RainDrop digital PCR system currently does allow for emulsions to be broken following thermal cycling so the amplicons can be rescued and subsequently sequenced. However, RainDance said, it is “just starting to see requests for this kind of thing but it is not a commercial solution on offer at this point.”

    But technology will get continue to get piled higher and deeper, as modifications to PCR continue to accrue and scientists figure out how best to use them.


‘Determination’ can be induced by electrical brain stimulation.

Applying an electric current to a particular part of the brain makes people feel a sense of determination, say researchers

The men were having a routine procedure to locate regions in their brains that caused epileptic seizures when they felt their heart rates rise, a sense of foreboding, and an overwhelming desire to persevere against a looming hardship.

The remarkable findings could help researchers develop treatments fordepression and other disorders where people are debilitated by a lack of motivation.

One patient said the feeling was like driving a car into a raging storm. When his brain was stimulated, he sensed a shaking in his chest and a surge in his pulse. In six trials, he felt the same sensations time and again.

Comparing the feelings to a frantic drive towards a storm, the patient said: “You’re only halfway there and you have no other way to turn around and go back, you have to keep going forward.”

When asked by doctors to elaborate on whether the feeling was good or bad, he said: “It was more of a positive thing, like push harder, push harder, push harder to try and get through this.”

A second patient had similar feelings when his brain was stimulated in the same region, called the anterior midcingulate cortex (aMCC). He felt worried that something terrible was about to happen, but knew he had to fight and not give up, according to a case study in the journal Neuron.

Both men were having an exploratory procedure to find the focal point in their brains that caused them to suffer epileptic fits. In the procedure, doctors sink fine electrodes deep into different parts of the brain and stimulate them with tiny electrical currents until the patient senses the “aura” that precedes a seizure. Often, seizures can be treated by removing tissue from this part of the brain.

“In the very first patient this was something very unexpected, and we didn’t report it,” said Josef Parvizi at Stanford University in California. But then I was doing functional mapping on the second patient and he suddenly experienced a very similar thing.”

“Its extraordinary that two individuals with very different past experiences respond in a similar way to one or two seconds of very low intensity electricity delivered to the same area of their brain. These patients are normal individuals, they have their IQ, they have their jobs. We are not reporting these findings in sick brains,” Parvizi said.

The men were stimulated with between two and eight milliamps of electrical current, but in tests the doctors administered sham stimulation too. In the sham tests, they told the patients they were about to stimulate the brain, but had switched off the electical supply. In these cases, the men reported no changes to their feelings. The sensation was only induced in a small area of the brain, and vanished when doctors implanted electrodes just five millimetres away.

Parvizi said a crucial follow-up experiment will be to test whether stimulation of the brain region really makes people more determined, or simply creates the sensation of perseverance. If future studies replicate the findings, stimulation of the brain region – perhaps without the need for brain-penetrating electrodes – could be used to help people with severe depression.

The anterior midcingulate cortex seems to be important in helping us select responses and make decisions in light of the feedback we get. Brent Vogt, a neurobiologist at Boston University, said patients with chronic pain and obsessive-compulsive disorder have already been treated by destroying part of the aMCC. “Why not stimulate it? If this would enhance relieving depression, for example, let’s go,” he said.

Why do we value gold?

Mankind’s attitude to gold is bizarre. Chemically, it is uninteresting – it barely reacts with any other element. Yet, of all the 118 elements in the periodic table, gold is the one we humans have always tended to choose to use as currency. Why?

Why not osmium or chromium, or helium, say – or maybe seaborgium?

I’m not the first to ask the question, but I like to think I’m asking it in one of the most compelling locations possible – the extraordinary exhibition of pre-Columbian gold artefacts at the British Museum?

That’s where I meet Andrea Sella, a professor of chemistry at University College London, beside an exquisite breastplate of pure beaten gold.

He pulls out a copy of the periodic table.

Periodic table

“Some elements are pretty easy to dismiss,” he tells me, gesturing to the right-hand side of the table.

“Here you’ve got the noble gases and the halogens. A gas is never going to be much good as a currency. It isn’t really going to be practical to carry around little phials of gas is it?

Gold – key facts

Gold - symbol, atomic number and weight
  • Symbol: Au (from Latin aurum)
  • Atomic number: 79
  • Weight: 196.97
  • One of the “noble” metals that do not oxidise under ordinary conditions
  • Used in jewellery, electronics, aerospace and medicine
  • Most gold in the earth’s crust is thought to derive from meteors
  • Biggest producers: China, Australia, US, Russia
  • “And then there’s the fact that they are colourless. How on earth would you know what it is?”

The two liquid elements (at everyday temperature and pressure) – mercury and bromine – would be impractical too. Both are also poisonous – not a good quality in something you plan to use as money. Similarly, we can cross out arsenic and several others.

Sella now turns his attention to the left-hand side of the table.

“We can rule out most of the elements here as well,” he says confidently.

“The alkaline metals and earths are just too reactive. Many people will remember from school dropping sodium or potassium into a dish of water. It fizzes around and goes pop – an explosive currency just isn’t a good idea.”

A similar argument applies to another whole class of elements, the radioactive ones: you don’t want your cash to give you cancer.

Out go thorium, uranium and plutonium, along with a whole bestiary of synthetically-created elements – rutherfordium, seaborgium, ununpentium, einsteinium – which only ever exist momentarily as part of a lab experiment, before radioactively decomposing.

Then there’s the group called “rare earths”, most of which are actually less rare than gold.

Unfortunately, they are chemically hard to distinguish from each other, so you would never know what you had in your pocket.

This leaves us with the middle area of the periodic table, the “transition” and “post-transition” metals.

Elementary Business

Plant, balloons and aluminium can

This group of 49 elements includes some familiar names – iron, aluminium, copper, lead, silver.

But examine them in detail and you realise almost all have serious drawbacks.

We’ve got some very tough and durable elements on the left-hand side – titanium and zirconium, for example.

The problem is they are very hard to smelt. You need to get your furnace up into the region of 1,000C before you can begin to extract these metals from their ores. That kind of specialist equipment wasn’t available to ancient man.

Aluminium is also hard to extract, and it’s just too flimsy for coinage. Most of the others in the group aren’t stable – they corrode if exposed to water or oxidise in the air.

Take iron. In theory it looks quite a good prospect for currency. It is attractive and polishes up to a lovely sheen. The problem is rust: unless you keep it completely dry it is liable to corrode away.

“A self-debasing currency is clearly not a good idea,” says Sella.

We can rule out lead and copper on the same basis. Both are liable to corrosion. Societies have made both into money but the currencies did not last, literally.

So, what’s left?

Why is gold golden?

2,000-year-old golden funerary mask from Colombia

Gold’s golden colour has been a mystery until very recently, says Andrea Sella.

The secret lies in its atomic structure. “Quantum mechanics alone doesn’t explain it,” he says.

“When you get to gold you find the atom is so heavy and the electrons move so fast that you now have to include Einstein’s theory of relativity into the mathematics.

“It is only when you fold together quantum mechanics with relativity that suddenly you understand it.”

Unlike other metals, which in their pure form reflect light straight back, electrons in the gold “slosh around a little,” Sella says, with the result that gold “absorbs a bit of the blue spectrum light, giving the light that is reflected back its distinctive golden colour”.

Of the 118 elements we are now down to just eight contenders: platinum, palladium, rhodium, iridium, osmium and ruthenium, along with the old familiars, gold and silver.

These are known as the noble metals, “noble” because they stand apart, barely reacting with the other elements.

They are also all pretty rare, another important criterion for a currency.

Even if iron didn’t rust, it wouldn’t make a good basis for money because there’s just too much of it around. You would end up having to carry some very big coins about.

With all the noble metals except silver and gold, you have the opposite problem. They are so rare that you would have to cast some very tiny coins, which you might easily lose.

They are also very hard to extract. The melting point of platinum is 1,768C.

That leaves just two elements – silver and gold.

Both are scarce but not impossibly rare. Both also have a relatively low melting point, and are therefore easy to turn into coins, ingots or jewellery.

Silver tarnishes – it reacts with minute amounts of sulphur in the air. That’s why we place particular value on gold.

It turns out then, that the reason gold is precious is precisely that it is so chemically uninteresting.

Gold’s relative inertness means you can create an elaborate golden jaguar and be confident that 1,000 years later it can be found in a museum display case in central London, still in pristine condition.

So what does this process of elemental elimination tell us about what makes a good currency?

First off, it doesn’t have to have any intrinsic value. A currency only has value because we, as a society, decide that it does.

“Start Quote

That’s the other secret of gold’s success as a currency – gold is unbelievably beautiful”

Andrea Sella

As we’ve seen, it also needs to be stable, portable and non-toxic. And it needs to be fairly rare – you might be surprised just how little gold there is in the world.

If you were to collect together every earring, every gold sovereign, the tiny traces gold in every computer chip, every pre-Columbian statuette, every wedding ring and melt it down, it’s guesstimated that you’d be left with just one 20-metre cube, or thereabouts.

But scarcity and stability aren’t the whole story. Gold has one other quality that makes it the stand-out contender for currency in the periodic table. Gold is… golden.

All the other metals in the periodic table are silvery-coloured except for copper – and as we’ve already seen, copper corrodes, turning green when exposed to moist air. That makes gold very distinctive.

“That’s the other secret of gold’s success as a currency,” says Sella. “Gold is unbelievably beautiful.”

But how come no-one actually uses gold as a currency any more?

Chart showing gold price adjusted for inflation

The seminal moment came in 1973, when Richard Nixon decided to sever the US dollar’s tie to gold.

Since then, every major currency has been backed by no more than legal “fiat” – the law of the land says you must accept it as payment.

Nixon made his decision for the simple reason that the US was running out of the necessary gold to back all the dollars it had printed.

Find out more

In Elementary Business, BBC World Service’s Business Daily goes back to basics and examines key chemical elements – and asks what they mean for businesses and the global economy.

  • And here lies the problem with gold. Its supply bears no relation to the needs of the economy. The supply of gold depends on what can be mined.

In the 16th Century, the discovery of South America and its vast gold deposits led to an enormous fall in the value of gold – and therefore an enormous increase in the price of everything else.

Since then, the problem has typically been the opposite – the supply of gold has been too rigid. For example, many countries escaped the Great Depression in the 1930s by unhitching their currencies from the Gold Standard. Doing so freed them up to print more money and reflate their economies.

The demand for gold can vary wildly – and with a fixed supply, that can lead to equally wild swings in its price.

Most recently for example, the price has gone from $260 per troy ounce in 2001, to peak at $1,921.15 in September 2011, before falling back to $1,230 currently.

That is hardly the behaviour of a stable store of value.

So, to paraphrase Churchill, out of all the elements, gold makes the worst possible currency.

Apart from all the others.

Egypt’s new breed of hijab-clad superheroine

Egypt’s new breed of hijab-clad superheroine .