Queen Victoria watched attentively as Dr. Pepper picked up a seemingly empty bottle and proclaimed: "And now, the oxygen and the hydrogen will have the honor of combining before your majesty!"
With that, he pulled out the stopper and pointed the neck at an open flame. The queen of England and her entourage were astounded by a loud bang and a flash. The hydrogen had indeed combined with the oxygen -- and not very peacefully, at that.
It was the 1850s, and Dr. John Henry Pepper (not of soft drink fame), director of the Royal Polytechnic Institution in London, was explaining to the monarch that the two elements combined to form water and release a great deal of energy in the process. Hydrogen could turn out to be a great fuel, Pepper went on, if only it could be obtained more easily. Alas, this was not possible.
The good doctor had made hydrogen by the method first described by Robert Boyle in 1671. Boyle, widely regarded as one of the fathers of modern chemistry, had described how addition of acids to metal filings "belched up copious and stinking fumes which would readily take fire and burn with more strength than one would easily suspect."
This reaction eventually captured the attention of young Henry Cavendish [see Page H6], one of the most bizarre, yet brilliant characters in the history of science. It was he who in 1766 finally isolated and identified this flammable gas as hydrogen -- a name derived from the Greek meaning "water maker."
Scientists later determined that hydrogen -- with its single proton and single electron -- was the simplest, lightest and by far most commonplace element in the cosmos, making up 98 out of every 100 atoms in the known universe.
Anyone who has seen a hydrogen explosion, even on a small scale, can readily visualize hydrogen's potential as a fuel [see illustration above]. Way back in 1903, Russian physicist Constantin Tsiolkovsky suggested that liquid hydrogen would be ideal for rockets.
Hydrogen does not have a particularly high energy content. In fact, a gallon of gasoline can provide three times as much energy as a gallon of hydrogen. But it weighs about 10 times as much!
Tsiolkovsky's ideas were prophetic. Two stages of the giant Saturn V rocket that took men to the moon burned liquid hydrogen in the presence of liquid oxygen. The space shuttle's huge external tank is filled with the same liquids.
We may eventually see hydrogen power homes and cars. Petroleum and natural gas -- the carbon-based, air-polluting resources on which industrial civilization is based -- are non-renewable. Hydrogen, however, is about as clean-burning as possible and is both abundant and potentially renewable.
As long ago as 1874, Jules Verne, in his classic novel Mysterious Island, had his shipwrecked engineer hero speculate that "water will one day be employed as fuel, that hydrogen and oxygen which constitute it, used singly or together, will furnish an inexhaustible source of heat and light."
That day is coming but is not imminent. Hydrogen can certainly be extracted from water, a virtually inexhaustible source. Passing an electric current through water (called "electrolysis") breaks the H2O down to hydrogen and oxygen, both of which can be readily collected.
There is, however, an obvious problem: financial and environmental cost. Most of North America's electricity is generated by burning expensive and polluting fossil fuels, displacing the problem of pollution. Hydrogen production becomes far more viable in areas blessed with hydroelectric facilities. But even there, what amounts to the conversion of electricity into hydrogen is not yet economically feasible.
Hydrogen-fueled airplanes were supposed to have flown in 1985. Calculations showed that a jumbo airliner that normally requires 80 tons of fuel to cross the Atlantic would require only 15 tons of liquid hydrogen. Hopes were flying high, but hydrogen-powered airliners are still stuck on the drawing board.
Moreover, hydrogen has a public relations problem. Just mention hydrogen, and people immediately conjure scenes of the Hindenburg and Challenger explosions. Actually, however, hydrogen is in many respects safer than gasoline. It is less dense than air and disperses quickly.
Most of the escaping gas from the Hindenburg floated away harmlessly; people were killed jumping out of the dirigible or by burning fuel oil carried to power the engines.
In prototype hydrogen-powered cars, the fuel is stored in large tanks behind the back seat. The tanks are insulated with 70 layers of aluminum and glass fiber in an evacuated space between two metal skins. Tests have shown that the prototype tanks will not explode even at temperatures as high as 900 degrees C for more than an hour and could withstand accidents better than conventional gasoline tanks.
The hydrogen availability problem may eventually be solved through clever chemistry. Electricity is not necessarily needed to split water into hydrogen and oxygen. Visible light can do so in the presence of an appropriate catalyst.
Researchers at the Tokyo Institute of Technology have shown, for example, that light from an ordinary lamp can split water when powdered cuprous oxide is used as a catalyst. Others have shown that titanium dioxide and molybdenum catalysts can do the job. The efficiency of these processes must increase greatly before they become practical.
Burning hydrogen is not the only way to derive energy from it. Liquid hydrogen is burned to lift the shuttle into space, but in orbit, the same element is used to produce electricity needed during a mission.
Have you ever wondered where the power inside the shuttle comes from? There are no onboard generators, at least in the traditional sense.
Power is generated by fuel cells -- devices that allow hydrogen and oxygen to combine without combustion, although in somewhat the same way. When hydrogen burns in the presence of oxygen, each highly reactive, electron-hungry oxygen atom (which needs two electrons to reach a favorable energy condition) snatches up two hydrogen atoms by their electrons, binding them into the compound H2O. That reaction also liberates a huge amount of heat energy.
In a fuel cell, oxygen manages to obtain the same electrons although it is not in contact with hydrogen. The two reagents are separated by a solution known as an electrolyte. Reaction occurs when electrons are released from the hydrogen and travel to the oxygen through an external circuit.
As a result, both donor and recipient atoms end up with a net electrical charge. That is, they become ions, that, with the aid of the electrolyte, combine to form water. The release and uptake of electrons actually occurs on the surface of a catalyst, usually platinum, that surrounds the hydrogen and oxygen electrodes.
As electrons travel through the circuit, they generate a current that can be used to run any electrical device. The basic idea is that the energy derived from the combination of hydrogen with oxygen is in the form of electricity rather than heat.
Furthermore, unlike batteries, fuel cells do not die. As long as hydrogen and oxygen are available, current is generated. This is basically the reverse of the electrolysis reaction used to break water into hydrogen and oxygen.
The added bonus of fuel cells, as far as the space program is concerned, is that the only product of the reaction is water. This is the water the astronauts drink. No need to waste energy carrying heavy bottles into orbit.
The Price of Progress
By now, you're probably wondering: If fuel cells produce energy without generating toxic byproducts, why don't we use them on Earth? Good question.
There are several problems. The catalysts are expensive: $30,000 worth of platinum was used in each fuel cell during the early days of the space program. Improvements in technology have reduced this expense significantly, but the main problem remains -- limited hydrogen availability.
Making hydrogen by reacting the simple hydrocarbon methane (CH4, a major ingredient of natural gas) with steam or by electrolyzing water cannot compete economically with petroleum production. But if pollution control becomes more and more important, hydrogen will likely become more viable as a fuel. After all, burning hydrogen releases no carbon dioxide, no sulfur compounds, no unburnt hydrocarbons and no sooty particulate matter.
The problem of gasoline lost by evaporation into the atmosphere, as much as 2 percent of the total every time you fill up, also is eliminated. Vancouver and Chicago already have in full service three buses powered by hydrogen fuel cells. Major car manufacturers are gearing up to put fuel-cell vehicles on the road by 2004.
Then, like Queen Victoria, you may have the honor of watching hydrogen and oxygen combine for your benefit.
Joe Schwarcz, director of the Office for Chemistry and Society at McGill University in Montreal, is the author of the forthcoming book, Radar, Hula Hoops and Playful Pigs (ECW Press).
Would you believe that in Japan they're brewing beer in which some of the carbon dioxide is replaced by hydrogen gas?
The manufacturer has offered an excuse about reducing the greenhouse effect by curbing carbon dioxide emissions. But the big appeal of Suiso beer seems to be that it allows guzzlers to sing with an unusually high-pitched voice.
The vocal chords vibrate with a different frequency in an atmosphere of exhaled hydrogen gas, and the resulting Donald Duck-like tones are a big hit in karaoke bars.
But what goes over even better is the spectacular fireworks display created by lighting one's hydrogenated breath. This has led to a rather dangerous form of entertainment in which participants vie to see who can breathe the most fire.
According to the Associated Press, one Toshira Otama mastered this by downing 15 beers and belching huge amounts of hydrogen. He was reportedly able to catapult balls of flame across the bar, impressing everyone except a bouncer.
That gentleman deemed Otama's dragon act a bit too dangerous after Otama singed the hair and eyebrows of a patron. The bouncer attempted to curb the activity, and in the scuffle that followed, Otama swallowed his cigarette and ignited the hydrogen gas. He suffered burns to his esophagus, sinuses and larynx.
Since his vocal chords were charred, Otama was unavailable for comment to the media, but one suspects that he will be seeking less precarious forms of entertainment in the future.
Hydrogen and the Hindenburg
Long before there was a hydrogen bomb, the littlest element was attracting plenty of bad press, particularly on May 6, 1937, when the giant dirigible Hindenburg burned and crashed while trying to land at Lakehurst, N.J.
The Hindenburg had made 10 routine round trips between Germany and the United States before the terrible explosion. What actually happened isn't clear. But the description by radio reporter Herbert Morrison is mind-numbing:
"It's crashing. It's crashing terrible. Oh, my, get out of the way, please. It's bursting into flames. And it's falling on the mooring mast. All the folks agree this is terrible, one of the worst catastrophes in the world. Oh, the flames, four or five hundred feet in the sky, it's a terrific crash, ladies and gentlemen. The smoke and the flames now, and the frame is crashing to the ground, not quite to the mooring mast. Oh, the humanity and all the passengers."
Horrible, to be sure, but apparently not a hydrogen explosion. The Hindenburg was a dirigible, not a blimp. That is, it wasn't just a bag of gas like the far smaller airships we see hovering over football games. Rather, it had a rigid framework, made of aluminum, over which a cotton skin was stretched. Inside were separate bags of hydrogen gas that held the ship aloft.
And what a ship it was! The Hindenburg was the largest flying machine ever built, 804 feet long. It would have dwarfed a jumbo 747 and was roughly the size of the Titanic. The crash killed 35 of the 97 people on board along with a crew member on the ground.
Interestingly, the radio description and existing newsreel footage portray a rapid fire, not an explosion. Witnesses spoke of flames like a spectacular fireworks display -- an effect not characteristic of hydrogen, which burns with a virtually colorless flame.
This has led some researchers to conclude that the cause of the accident was not ignition of the hydrogen but of the flammable cover. It was common practice in those days to strengthen the cotton with iron oxide, cellulose acetate and aluminum powder, a highly combustible mixture.
The leading theory is that an electrostatic charge built up on the stretched cotton during a storm. When mooring lines were dropped, a discharge through the metal frame ignited the fabric. Surviving samples of the Hindenburg's skin have been tested and found to be extremely flammable.
Indeed, even at the time of the crash, the Zeppelin Company, builder of the Hindenburg, may have dismissed hydrogen as the cause of the disaster. The builders instantly took measures to reduce the flammability of fabric being readied for construction of the Graf Zeppelin, the Hindenburg's sister ship.
A fireproofing agent, calcium sulfamate, was added to the skin, and aluminum was replaced by bronze, which is far less combustible. Measures also were taken to reduce voltage buildup between the skin and the internal structure by impregnating the ropes holding the fabric in place with graphite, a conductive material.
The Graf Zeppelin, filled with hydrogen, flew millions of miles safely.
Henry Cavendish: Genius and Oddball
By nearly any standards, Henry Cavendish was a strange man. He looked like a mad scientist. His clothes were shabby and rumpled. His voice was shrill, and he never looked anyone in the eye.
Cavendish spent four years at Cambridge University but never earned his degree. He was so pathologically shy that he simply could not face his professors for an exam. For the rest of his life, he would have trouble communicating with people. But in the laboratory, his skills were unparalleled.
Cavendish inherited a massive fortune and never had to worry about working. In fact, at the time of his death, he was the largest individual depositor in the Bank of England. So the young scientist who could have lived like a king instead led the life of a recluse, using the inheritance to fund his scientific work.
He apparently had no social life. Although he had problems facing men, he occasionally attended the scientific functions of the Royal Society.
Women were a different story. Even maids in his house were instructed to stay clear and communicate with him only through notes. When Cavendish accidentally met a maid on the staircase one day, he had a back stairway built for his use only. It was said that the best way to engage the odd scientist in a conversation was to ignore his presence and pretend to be speaking into thin air.
Unencumbered by a social life, Cavendish worked tirelessly in his home laboratory, and there he generated hydrogen by reacting iron or zinc with acids.
He noted that, when hydrogen burned in a closed container, water was produced. Water therefore, contrary to the ancient Greek dogma, was not an element. It could be made in the laboratory. This was the final nail in the coffin of Aristotle's theory that everything was composed of air, earth, fire and water.
Cavendish had numerous interests. He even investigated how an electrical current could be made to pass through different materials. Since no instrumental means to measure current was yet available, he would estimate the current by grasping the ends of the electrodes with his hands and noting how far up his arm a shock would travel.
The image of an elderly man dressed in an antiquated suit clutching two wires with his hair standing on end is surely one that audiences, and even Queen Victoria, would have enjoyed.
But Cavendish steadfastly refused to exhibit his scientific skills in public. It was left to the likes of Dr. John Pepper to introduce the public to the power of hydrogen.
CAPTION: Chemical energy is released or absorbed when something changes the bonds between atoms. Bonding is a stable condition, so breaking chemical bonds requires energy. That's why wood won't burn unless you put a match to it. Conversely, when bonds form, they release energy, which is why a fire gives off heat when its carbon combines with oxygen in the air. If a reaction results in the formation of bonds that give off more energy than it took to break up the components and get the reaction going in the first place, energy will be liberated. (This graphic was not available)
CAPTION: Diatomic hydrogen consists of two hydrogen atoms with a bond energy of 436,000 joules per mole, or 436 kJ/mol for short. (A mole is about 600 billion trillion molecules.) The bond energy of diatomic oxygen is 499 kJ/mol; hydrogen-oxygen is 460 kJ/mol. Burning hydrogen and oxygen to make water requires breaking up two hydrogen molecules and one oxygen molecule, for a total energy expenditure of 1,371 kJ/mol. But the reaction creates four hydrogen-oxygen bonds, for a total of 1,840 kJ/mol. So the net energy released is a whopping 469 kJ/mol. (This graphic was not available)