Chemistry Blog

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May 24

#ToxicCarnival: Nitroglycerin

by azmanam | Categories: chemical biology, in vivo chemistry | (20451 Views)

Tonight, we make soap.

Matt over at Sciencegeist is organizing this blog carnival in an effort to reclaim the word chemical from the hands of ignorant people who blindly assume anything with ‘chemicals’ in it must be evil. This is not a moment too soon.  I’m not exactly sure how the pendulum of public opinion swung from products being advertised as ‘Better living through chemistry’ to products being advertised as ‘chemical free’ (whatever that means). Soaps and other skin care/beauty products are certainly in the cross-hairs of the ‘chemical free’ crowd, but that’s not what I’m talking about today.

As the tallow renders, you skim off the layer of glycerin. If you were to add nitric acid, you got nitroglycerin.  If you were to add sodium nitrate and a dash of sawdust, you’d have dynamite. 

Ascanio Sobrero

Nope, instead I’m going to talk about nitroglycerin.  Nitroglycerin was first synthesized by Ascanio Sobrero in 1847. He warned as many people as he could never to make it again, as it is extremely unstable and dangerous. See, detonation of nitroglycerin produces gases which would occupy more than 1,200 times the original volume at STP (note, upon detonation, the gases released are extremely hot, thus occupying even more volume).  The resulting pressure wave as the gases expand is strong enough to destroy buildings and kill people. Sobrero’s face was permanently scarred as result of a nitroglycerin explosion while he was studying it. Alfred Nobel was also working in this lab at the same time and decided to take this new explosive and commercialize it. He knew that in order to make a commercial product, it needed to be stabilized enough to be stored and shipped.

There have been a number of recorded accidents involving nitroglycerin.  Sobrero was disfigured as a result of a nitroglycerin explosion. While Alfred and his brother Emil were working on a safe formulation of nitroglycerin, an explosion took the life of Emil and several others. This prompted Stockholm officials to forbid the production of nitroglycerin and Nobel’s lab had to move onto a barge on Lake Mälaren.

In 1866, a shipment of unlabeled (!) liquid nitroglycerin was delivered to San Francisco to be transported to construction companies for use in blasting away rock. One of the crates remained behind in San Francisco, whereupon it began leaking. The unlabeled crate was taken to the Wells Fargo office in downtown SF (then at the corner of California and Montgomery Streets). A few workers pried open the crate to have a look. The resulting explosion leveled several buildings and killed 15 people. Almost simultaneously, some of the nitroglycerin being used in construction detonated early and killed 6 people. From then on, all liquid nitroglycerin was to be made on site if it was to be used in construction.

Also in 1866, Nobel formed the United States Blasting Oil Company to prepare nitroglycerin in a factory on the Hackensack River in New Jersey. Three years later, the factory was destroyed by explosions, and production ceased.

Finally, in 1867 Nobel figured out how to stabilize nitroglycerin. Adding kieselgur (diatomaceous earth) turned the nitroglycerin into a paste which could be molded into cylinders and wrapped in greased paper.  The resulting package was stable enough to store and ship. Nobel quickly applied for the patent to what we now know as dynamite.

Its most notorious use is in demolition, and it also has been used extensively in military propellants. Alfred Nobel was quite concerned about the wartime use of nitroglycerin. Yet he continued to develop the explosive somehow hoping to achieve peace, in a balance-of-terror, mutually-assured-destruction sort of way.  He is quoted in 1891 as saying “Perhaps my factories will put an end to war sooner than your congresses: on the day that two army corps can mutually annihilate each other in a second, all civilised nations will surely recoil with horror and disband their troops.” Mmm… gonna say history has proven him wrong.

Yeah, with enough soap, one could blow up just about anything, if one were so inclined.

So how could this terribly destructive chemical ever be used for good? Well, it starts by listening to your employees. Many workers in nitroglycerin production factories began noting unusual work-related physiological changes. Some (including Alfred Nobel) would complain of splitting headaches. This caused nitroglycerin to be considered, of all things, as a homeopathic remedy for curing headaches. Because of the homeopathy stigma, many established physicians turned their nose at the use of nitroglycerin as a medical treatment. Of course, many respected doctors of the time were still prescribing bloodletting as a rational medical treatment.

In 1879, Dr. William Murrell authored a paper advocating the use of nitroglycerin to treat angina pectoris, or chest pain. He tested nitroglycerin on himself by touching a cork stopper to his tongue. He received a pounding headache, tachycardia, and increase in the force of his heartbeat. He convinced 35 other people to try this as well, and they all noted the same effects (“No! It doesn’t hurt at all! Look, 34 other people have done it! Do you mind closing the blinds and turning down the lights!”). Leaning on the research of Dr. T. Lauder Brunton,  he thought nitroglycerin might be an effective treatment for angina pectoris. His hypothesis was right, and we now know why.

Angina pectoris is caused by lack of sufficient oxygen to the heart muscles. They then have to function somewhat anaerobically, much like our other muscles do during intense exercise.  Much like after exercise, when this happens to heart muscles, we experience it as chest pain. One of the many causes of headaches is dilated blood vessels. We now know nitroglycerin is a vasodilator. It dilates blood vessels, causing headaches at higher doses, and allowing more oxygen to flow to heart muscle in lower doses, relieving the patient of their chest pain.

In perhaps one of the more ironic stories of medical history, Alfred Nobel was prescribed nitroglycerin for chest pain late in life. Remembering the severe headaches, he declined treatment. Funny how things go full circle sometimes.

The full story of how nitroglycerin causes vasodilation wouldn’t be unraveled until the 1980s (here’s a long, but really fascinating read into how this discovery developed, from the 1700s through 1998). In a long and contentious process, scientists discovered that nitroglycerin is converted into nitric oxide (itself a toxic chemical at high doses), and that nitric oxide is the messenger molecule which causes blood vessels to dilate. Turns out it does so by increasing the concentration of cyclic guanosine monophosphate (cGMP). To bring our story full circle (again), in 1998 Robert Furchgott, Louis Ignarro, and Ferid Murad were awarded the Nobel Prize in Physiology or Medicine for their discoveries in this arena.

So nitroglycerin can either cause pain and hasten death, or relieve pain and postpone death. As always: the dose makes the poison (or, the protein makes the poison). So read the rest of the entries in the #ToxicCarnival and lets help get rid of this silly chemophobia epidemic that’s plaguing our world.

Extras:

  • The quote from the documentary Fight Club above for making dynamite is not quite scientifically accurate… on purpose. Movie makers did not want scientifically accurate formulas for making explosives in a major motion picture. Nitroglycerin is made by nitrating glycerin with a mixture of nitric and sulfuric acid. Glycerin is the backbone which bonds with fatty acids to make triglycerides, the main constituent of vegetable oils and animal fats. You can nitrate many molecules by mixing them with a mixture of nitric and sulfuric acid. Doing so generally makes them explosive. Nitrating cellulose makes nitrocellulose (guncotton). Nitrating toluene makes trinitrotoluene (TNT). And nitrating glycerin makes nitroglycerin.
  • Making nitroglycerin is quite an exothermic process. Heat, as you can imagine, is quite detrimental to explosives. Explosions are quite devastating at manufacturing facilities. Wikipedia describes safe practices for manufacturing nitroglycerin

    The nitrator is cooled with cold water or some other coolant mixture and maintained throughout the glycerin addition at about 22 °C (72 °F), much below which the esterification occurs too slowly to be useful. The nitrator vessel, often constructed of iron or lead and generally stirred with compressed air, has an emergency trap door at its base, which hangs over a large pool of very cold water and into which the whole reaction mixture (called the charge) can be dumped to prevent an explosion, a process referred to as drowning. If the temperature of the charge exceeds about 30 °C (86 °F) (actual value varying by country) or brown fumes are seen in the nitrator’s vent, then it is immediately drowned.

  • Repeated exposure to nitroglycerin, either by regularly taking nitroglycerin tablets, or by working around nitroglycerin will eventually lead to tolerance. For industrial workers, the weekend away from the job provides enough down time away from nitroglycerin that the tolerance effects wear off. Upon re-exposure the next week, workers often experience what is known as Monday Morning Headache.
  • As mentioned above, nitroglycerin is mixed with diatomaceous earth to form dynamite. Diatomaceous earth is a sedimentary rock composed of primarily of silica, with some alumina and iron oxide as well. In lab, we know this as Celite, the great filter aid. It also appears in certain cat litters and as an abrasive in some toothpastes.
  • Nitroglycerin is very much an explosive being used in a pharmaceutically safe manner. But it’s still an explosive. And if there is residue on something you’re trying to take through airport security, the explosives detector might single you out for, uh, further screening.
  • As with all medications, you and your doctor need to be cognizant of incompatible medications. The nitric oxide/cGMP physiology is quite interesting. Brain vasodilation causes headaches. near obstructed blood vessels, it increases blood flow, lowers blood pressure, and actually helps prevent clotting. Certain macrophages release nitric oxide which helps kill invading bacteria… and increase in cGMP in… other parts of one gender’s body… leads to… an effect which makes this blog no longer family friendly. There’s a certain color of a certain pill on the market (naming it would invite all kinds of spam) which inhibits cGMP metabolism in this… part of the body. Takers of nitroglycerin need to be sure to mention taking this… other pill… to their doctor to avoid contraindication.

6 comments

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  1. Jade

    This is a very interesting interesting article, thanks.

  2. ExploSci

    you forgot that it is tasty. very tasty.

  3. Gifh

    Hi! You made it really very clear and enjoyable to read! May I ask you if it is possible to translate (and may be adapting) your article in Italian for our crowd? I really appreciate to do so!

    1. azmanam

      Yes, you may translate the article into Italian. Please give proper credit and provide a link back to the site :)

      1. Gifh

        Thanks, and sure: I used to credit back according to a CC BY-NC-SA licence. :)

  4. Fleaker

    ExploSci knows indeed that it tastes good :-)

    Spicy sweet burning flavor!

    Great article with historical perspective! A good example of the double edged sword that chemistry can be!

  1. Toxic Carnival: Day Four | ScienceGeist

    [...] Chemistry Blog Azmanam takes us on a tour of the history of nitroglycerine. This is a much better way to get up close and personal with the molecule than driving a dump truck [...]

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