Bombs Away!

 During the beginning stages of the Covid-19 pandemic in 2020, many of us were using our time in quarantine to practice new hobbies such as baking bread, making whipped coffee, or hoarding toilet paper. For students and researchers at the United States Military Academy in West Point, New York, however, time in quarantine took a more explosive turn. In his article "This Chemist’s Pandemic Hobby? Firing Medieval Cannonballs" for the New York Times, author William Broad chronicles Dr. Dawn Reigner and her team as they tested different medieval recipes for gunpowder to discover what causes the most reactive explosions - and further understand how this chemical innovation changed the course of history forever.

The commonly known, tried and true recipe for gunpowder has consisted of saltpeter (potassium nitrate), carbon, and sulfur. These ingredients create an exothermic reaction that is used to propel bullets, cannonballs, and other similar weapons. Recipes date back centuries and all include these three main ingredients. Interestingly, there are medieval records of less common ingredients being added to the mixture such as brandy, vinegar, and quicklime were added in small quantities. Dr. Reigner and her team decided to test these additions to find the recipe for the most efficient gunpowder.

Figure 1: Simple equation for the combustion reaction of gunpowder

Broad notes in his article that gunpowder changed the nature of warfare, in that kingdoms needed armies as opposed to simply fortresses. Perfecting the recipe of gunpowder was also necessary, as large explosions would kill or maim those wielding the weapons themselves.

Dr. Reigner's group noted that in trying to create more effective explosions that were safe for the user, recipes were tweaked so as to lower the heat of combustion to safer levels while still having a large enough blast to damage structures and maim enemies. The researchers noted the changes over time and compared them to their own bomb calorimeter data.

Figure 2: Mass percentages of gunpowder components over time and bomb calorimeter data

Their research showed that the data surrounding the interesting additions to the recipes, like brandy, were inconclusive but did not show measurable difference. The biggest effect on the heat of combustion was the amount of saltpeter, also the most expensive ingredient, which was lessened in post-1400 recipes. Reigner's research shows that the trial and error method that medieval people used to perfect gunpowder is not dissimilar from the way research is conducted today, and that even in the 1300's people were striving to understand and perfect the way things are done.

References

Broad, W. This Chemist’s Pandemic Hobby? Firing Medieval Cannonballs. The New York Times, October 2021, Retrieved from https://www.nytimes.com/2021/10/07/science/gunpowder-medieval-cannons.html

ACS Omega 2021, 6, 35, 22848–22856

Publication Date:August 24, 2021

https://doi.org/10.1021/acsomega.1c03380