All About Nitroglycerin
In this episode, Marc discusses everything you need to know about nitroglycerin.
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Nitroglycerine, is an important substance not only in medicine, but in industry and warfare as well. And as we’ll see, there is an ongoing entanglement of these two threads in its history. In order to understand nitroglycerine, we need to take a look at the two main ingredients which comprise it, these are the element nitrogen and the compound glycerine. Let’s start with nitrogen.
Nitrogen is the fifth most abundant element in the universe and makes up about 78% of the earth's atmosphere1. Take a deep breath in. (inhale) – the majority of what you just inhaled is nitrogen. It’s all around us, and it’s inside us. Fortunately for us, it’s harmless on its own.
Nitrogen was known to ancient alchemists in the form of ammonium chloride, which has the formula NH4 (that’s the ammonium part) Cl (that’s the chloride part). Ammonium chloride forms naturally near volcanoes and in burning coal seams, and it was first discovered by the Romans near the Temple of Ammon in ancient Libya. They called the soft, water-soluble crystal “sal ammon”, which means the salt of Ammon, in deference to the God whose temple it was discovered beside. This is the etymological root of the word ammonia and all of the ammonium compounds used in modern chemistry today. They’re named after a Roman god. Sal ammonium was previously used as an ancient baking powder, it was also useful in dying and tanning leather, and had a role in the refining of precious metals. It’s useful stuff. 2 Sal ammonium can also be synthetically manufactured by heating a mixture of dung, salt and urine – ingredients that were in no short supply during our earlier history. 3 If you were an ancient artisan you would have been very familiar with the production and use of this nitrogen based compound.
You probably would have also been familiar with another form of nitrogen - nitric acid. With the formula HNO3, nitric acid is the most common acid made from nitrogen. It is a colourless, corrosive liquid that is a very strong oxidizing agent. This means it has the ability to rip electrons from the atoms of other substances – which is how acids generally work to dissolve things. They tear away electrons from atoms, and the remaining structurally unsound molecules come apart. In one particularly powerful version of this reaction, oxygen molecules that have had an electron stripped from them can be transferred to other substances where they start to pull electrons from those new substances. This transfer of an electron-reduced-oxygen-atom is called a ‘redox’ reaction, and it commonly produces combustion and/or explosions. Nitric acid, as a powerful oxidizing agent, therefore supports combustion and explosions, which makes it useful in the production of explosives and as a rocket propellant.
Ancient alchemists also knew about nitric acid. The oldest known European recipe for nitric acid is found in the Liber de inventione veritatis which is thought to have been written sometime around 1300, but historians suspect that nitric acid was known for many years prior to this and was universally used for its ability to melt all metals except gold, which made it an exceptionally useful purifying agent when gold was the standard for all currency. 4
Nitrogen gas itself was discovered in the 1760s by both Henry Cavendish and Joseph Priestley. In a series of clever steps, they figured out how to remove both oxygen and carbon dioxide from air and noted, to their surprise, that there was still a lot of gas left after they’d done that. They experimented with this mysterious remaining gas and noted it extinguished a lit candle and that a mouse breathing just this gas would soon die. However, neither Cavendish nor Priestley realized that this gas was in fact an element. The first person to suggest that it was, was a young student named Daniel Rutherford in his doctorate thesis of September 1772 at Edinburgh, Scotland. For this reason, the discovery of the element nitrogen is credited to him. 3
Nitrogen is still extremely important to us today. In fact, if we did not have the chemical control of nitrogen that we currently enjoy our population would be unsustainable. This is due to a chemical reaction known as the Haber-Bosch process, which combines nitrogen and hydrogen together under pressure to produce NH4 - or ammonium. Ammonium – which remember is named after the Roman God Ammon – is a key ingredient in commercial fertilizer, and without commercial fertilizer it would be impossible for us to support over 7 billion humans on the planet. In fact, it’s estimated that at least half of all the protein in the bodies of humans today came into our diet through nitrogen fixed by the Haber-Bosh process. It is arguably, one of the most important discoveries of the 20th century. 5
So, nitrogen in its various forms has had a long and productive history in our industry. Without it, most of us wouldn’t be here today. What about nitroglycerine’s other key ingredient – glycerine?
Unlike nitrogen, which is a fundamental element, glycerine is a combination of elements. Glycerine is a water-soluble, clear, almost colourless, odourless, viscous, liquid that feels smooth to the touch and is sweet to the taste. In fact, the name glycerine comes from the Greek word root ‘glykys’, meaning sweet, which is the same word used as the root for the word ‘glucose’, which (along with fructose) is an important ingredient in normal table sugar.
Glycerine is an important natural substance and a component of all living cells in the form of triglycerides. Triglycerides are combinations of glycerine and fatty acids, and they are the principal ingredients in almost all animal fats and vegetable oils.6
Glycerine is the name used predominantly by Americans, most of the rest of the world calls this substance glycerol. Now I’ve playfully started a bit of a tradition in this podcast of gently mocking Americans for not using the standard names for substances that the rest of the world uses, but in this case – in this show – I’m going with them, and I’m going to use the name glycerine, because this is the name that is used in the word nitroglycerine. So as you listen, just be aware that glycerine and glycerol are actually exactly the same thing.
Glycerine was accidentally discovered in 1779 by a Swedish chemist named K. W. Scheele, while he was heating a mixture of olive oil and lead monoxide. Scheele inelegantly called the substance he discovered the "sweet principle of fat”. 
In 1811 a French chemist who specialised in studying fats and oils named M. E. Chevreul first coined the much more elegant term glycerine. Twelve years later, in 1823, Chevreul obtained a patent for a chemical process which created glycerine as a by product. 7
Thirteen years after this, in 1836, a Frenchman in Paris named Theophile-Jules Pelouze – determined glycerol’s chemical formula. Pelouze became quite famous for this discovery, although almost 50 years later it was discovered that the formula he came up with wasn’t actually the correct one. Nonetheless, he attracted keen undergraduates who wanted to study under him, and in 1840 one such keen student, named Ascanio Sobrero arrived at his door and began to work with the master.
Six years later, the two attempted to determine how to produce an important new substance that had been discovered earlier that year by a German-Swiss scientist named Christian Schönbein. Schönbein was a brilliant inventor, who ultimately was credited with inventing the fuel cell and discovering ozone.
He was also an avid chemist who, much to the frustration of beleaguered wife Emilie, insisted on conducting his chemical experiments at home, in the family kitchen. One day, in 1846, Schönbein heard a loud ‘woosh’ and turned to see that an apron, which was at that point hanging on a hook in his kitchen, had spontaneously erupted into an all-engulfing fire.
Shortly before this happened, while his wife Emilie was out, Schönbein had been heating a flask containing a mixture of concentrated nitric and sulfuric acids on the kitchen stove. Remember, nitric acid is a powerful oxidizing agent that supports combustion and explosions. The flask he was using broke and the acids ended up spread across the floor. In an act of mindlessness that would make any wife slap their forehead Schönbein grabbed Emilie’s apron and used it to wipe up the hot liquid. He then hung up the apron to dry. It was moments after that that the apron, Emilie’s apron, burst into flames.
Schönbein had discovered what he called nitrocellulose – a mixture of nitric acid and cellulose fibres. Eventually, it came to be known as guncotton and it was an incredibly important discovery.
During the 1800’s most militaries used gunpowder as a propellant. Gun powder is a mixture of charcoal, sulfur and potassium nitrate. As any good Starfleet captain knows, gun powder is a great propellant, but it produces a lot of smoke. The nitrocellulose that Schönbein discovered was not only more powerful than gunpowder, it was also smokeless.
History buffs will appreciate that around 1890 scientists took guncotton and mixed it with nitroglycerine and a small amount of petroleum jelly to produce an explosive called cordite, which was quickly adopted by the British Army and Royal Navy as their standard explosive and it was used extensively in World War One. 8 In the battle of Jutland, the largest naval battle of World War One, the British were crippled by their unsafe handling of cordite, while the Germans, who were much more meticulous in their care of the explosive suffered less far less damage. And on August 6, 1945 when the Americans dropped the ‘Little Boy’ atomic bomb on Hiroshima from the Enola Gay, it was a cordite fuse that detonated it.
But let’s go back again, to Paris, about 100 years before Hiroshima where Pelouze and his student Ascanio Sobrero read about Schönbein’s discovery of nitrocellulose and determined to reproduce it, which they made short work of. From there, Sobrero wondered if he could combine nitric acid with any other substrates, preferably ones less molecularly complex than cotton in order to produce an even better explosive. He had some success in combining nitric acid with mannitol, creating the powerful explosive nitromannite. Within a year he had combined nitric acid with glycerol to create what he called pyroglycerin. In February of 1847 he gave his now famous lecture in which he demonstrated pyroglycerin by exploding a fair bit of it in front of his class during a lecture.
Sobrero had great ambivalence about creating pyroglyercin - which we today call nitroglycerin. In the process of working with the substance, sometime in the 1840’s he unfortunately ended up blowing a part of his face off.
In addition to exploding nitroglycerin Sobrero also did something else that probably wouldn’t occur to most people to do. He tasted it. In so doing he became the first person in the world to experience, and report, the now all-too-familiar nitroglycerin headache. This becomes important later when we start to discuss the medical uses of nitroglycerin.
All in all, Sobrero’s experiences with the substance he created were so negative that he avoided studying it intently and eventually came to regret its creation. He later wrote:
“‘. . . when I think of all the victims killed during nitroglycerine explosions which in all probability will continue to occur in the future, I am almost ashamed to admit tobe its discoverer.”9
In 1851 another student came to Paris to study under the master Theophile-Jules Pelouze. He was a young Swede name was Alfred Nobel (NOH-bell). Nobel came from a family of industrialists and when he arrived in Paris and learned about Sobrero’s discovery of nitroglycerin he returned to his family to share the exciting news and to investigate possible industrial and military uses for the new explosive.
However, this wasn’t going to be easy. Nitroglycerin is extremely unstable and explosive. Just bumping it can set it off. This is because each nitroglycerin molecule contains three nitrate groups, and these nitrate groups are powerful oxidizing agents. As we previously said, oxidizing agents cause explosions. What is particularly volatile about nitroglycerin is that each group of three nitrates are bound directly to a hydrocarbon fragment, which acts as a fuel. So, nitroglycerine doesn’t need to utilize oxygen from the environment, which would slow its rate of reaction. It has all the ingredients it needs to create an explosion in its molecular constituents. This gives it an immense amount of power. One mole of nitroglycerin, which would weigh about 225 grams, or about 8 ounces, releases about 1.5 million joules of energy when it explodes. Remember, we defibrillate people using about 300 joules. A good handful of nitroglycerin will produce 1.5 million joules of energy, and will expand over 1000 times its initial volume as it explodes.10 That is powerful, dangerous stuff!
As Nobel tried to tame nitroglycerine he experienced setback after setback. Initially he worked with a liquid form of nitroglycerine and shipped the produce in zinc cans, but these exploded so often that the city of Stockholm banned the use of nitroglycerin within city limits. Many people died in the early stages of development, including Alfred Nobel’s brother Emil in 1864.
By 1867 Nobel had discovered that if he mixed the liquid nitroglycerin with a silica based powder called diatomaceous earth the resulting solid was very stable. Nobel called this solidified nitroglycerin ‘dynamite’ derived from the Greek word ‘dunamis’, which means powerful, and which is also the root for the English words dynamic and dynamo.
Noble also created a blasting cap for the dynamite which could induce the now-stable sticks to detonate on demand. The creation of dynamite was important not only in warfare, but also in industry. About 8000 tons7 of it were used to blast through Central America from the Atlantic to the Pacific ocean from 1903-1914, creating the Panama canal. It allowed the creation of railroads and other major infrastructure developments, as well as facilitating mining.
Nobel is famous for more than the creation of dynamite. Over his lifetime he filed 355 patents, including ones for synthetic rubber and one for artificial silk11. This made Nobel an incredibly rich man. In fact, at the time, he was one of the richest people in Europe.
Sadly, all that wealth didn’t bring him a lot of happiness. This was compounded by an unfortunate mistake the press made later in his life, in 1888 to be specific, when his older brother Ludwig died. Having a brother die is hard enough, especially when one of your other brothers died from mishandling dynamite, but when Ludwig died the French press mistakenly thought it was Alfred – the inventor of dynamite – who had died and they wrote an excoriating and eviscerating epitaph describing Nobel as the ‘Tradesman of Death’. Alfred had the rare experience of being able to watch people speak openly about him after they thought he was dead, and what they said was brutally critical.12
The reaction to the mistaken belief that he had died propelled Nobel into an existential crisis and he determined to do something to change his legacy while he still had the chance. Seven years later, still very much alive, Alfred Nobel put his plan into writing. Nobel had no children so he sat down and hand wrote a four-page will investing his vast fortune into a fund. The interest accrued from the fund was to be awarded to four people who the executors of the fund determined to have conferred the greatest benefit to mankind in the proceeding year and also to one more person … and this is the exact quote from Nobels will … “who shall have done the most or the best work for fraternity between nations, for the abolition or reduction of standing armies and for the holding and promotion of peace congress”. That last prize is today called the Nobel peace prize, and the other four Nobel prizes are awarded in the categories of literature, chemistry, physics, and either physiology or medicine.
Interestingly, in his later life, Alfred Nobel suffered from debilitating angina pectoris. In 1890 his physician prescribed nitroglycerin (which Nobel refused) and in 1896, weeks before his death, Nobel wrote “‘. . . isn’t it the irony of fate that I have been prescribed nitroglycerine to be taken internally! They call it Trinitrin, so as not to scare the chemist and the public.’ 13
But how did nitroglycerine, the explosive, come to be nitroglycerine the medical treatment? To understand that we have to go back to when Sobrero, the inventor of nitroglycerine decided – for whatever strange reason – to taste the highly explosive material and noted the immediate onset of a profound and uncomfortable headache.
...to be continued ...
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10. Senese, F. Why is nitroglycerin explosive ? General Chemistry Online (2015). Available at: http://antoine.frostburg.edu/chem/senese/101/redox/faq/nitroglycerin.shtml.
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12. Popova, M. How the Nobel Prize Was Born: A Surprising Story of Bad Journalism, Existential Guilt, and Dynamite. Brain Pickings (2013). Available at: https://www.brainpickings.org/2013/09/17/molly-oldfield-secret-museum-alfred-nobel-will/. (Accessed: 24th November 2018)
13. Ringertz, N. Alfred Nobel’s Health and His Interest in Medicine. Nobel Media (2014). Available at: https://www.nobelprize.org/alfred-nobel/alfred-nobels-health-and-his-interest-in-medicine/. (Accessed: 30th December 2018)
14. Winters, R. W. Accidental Medical Discoveries: How Tenacity and Pure Dumb Luck Changed the World. (Skyhorse Publishing, 2016).