Obsessive opera fans are used to sorting their full-throated, passionate art form into categories—lyric or grand, Italian or French, opera buffa or opera seria. Now, from a very unlikely corner, comes another possibility: sorting them at the molecular level.
Years ago, Portuguese chemistry professor and opera aficionado João Paulo André started to notice that the operas he loved featured a surprising number of plots with potions and poisons. Sometimes the characters might intone the name of a specific substance; sometimes they would just describe an elixir whose effects could only be explained by a particular chemical. All in all, about a fifth of operas, André estimates, reach the heights of comedy, tragedy, and romance not only with music, acting, and costumes, but also with the help of substances like oxalic acid, arsenic, or a cyanogenic glycoside called amygdalin.
Poison "has been one of the most important ingredients in theater and opera and movies," said André in an interview. "It's a horrible thing, but at the same time it's so fascinating. It's an incredible ingredient to create a good drama." André published the findings of his study of poison and
opera in the Journal of Chemical Education earlier this year, and suggests that opera can be something of a teaching tool for chemistry professors.
In his paper, André tallies operas up, dividing them into categories. He starts with the "apothecary operas"—the ones in which pharmacists and chemists are characters. These are best exemplified, André argues, by Gaetano Donizetti's 1836 comedic opera "Il Campanello," in which a wealthy pharmacist who has just married a beautiful and much younger woman is delayed from consummating his marriage. The pharmacy bell keeps tolling at just the wrong moment as the jealous Enrico visits the pharmacy in the middle of the night, bringing with him complicated drug needs, relayed in a "prescription duet." The recipe includes butirro d'antimonio (antimony(III) chloride), and etiope minerale (mercury(II) sulfide).
Next come the "operas of poisonous natural products," in which the drama often hinges on some unnamed homebrew potion, leaving the curious listener to deduce that the sad lover is using, say, an acetylcholinesterase inhibitor to still an aching heart. Modern scientists sometimes approach these as puzzles to be solved with historical research and a close look at the symptoms described in the libretto. For example, a 2003 paper in the British Medical Journal argued that the love potion that locked Tristan and Isolde in their doomed passion was solanaceae, which causes the heart to speed up, vision to blur, and pupils to enlarge, and which ultimately may result in death. One of the operas of poisonous natural products is a veritable chemistry lesson set to music—Puccini's "Suor Angelica." In the one-act opera, a nun whose son has died commits suicide by gathering four very toxic ingredients and brewing a potent tea, naming them one by one.
She made choices with a modern scientist's acumen. "Each one individually kills," André said. "So she takes a cocktail of four terrible plants."
Then there are the "operas of the great poisoners of antiquity," based on historical figures' penchant for poisoning people. And in a category all its own are the "arsenic operas," based on poisonings that use a colorless arsenic compound. Drama would suffer—pivotal assassinations and accidental poisonings would be impossible—if it weren't for basic chemistry: "its toxicity mainly due to the high affinity of As(III) for thiol-bearing biomolecules," as André explains in his paper.
The idea is not to glorify poisoning, or to pretend the true magic of opera lies in the periodic table. André sees his project as a way to draw the public into the two worlds where he feels most at ease. He developed his list into a public lecture for the International Year of Chemistry in 2011, and uses the occasional aria when he teaches. For instance, André uses "Suor Angelica" to teach his students about cyanide poisoning.
The world of science can often seem to have the human element starched out of it—starting with the reserve that surrounds scientists' presentation of factual results and figures and ending with the austere, white knee-length costumes worn by its inhabitants. There's an irony, then, that an art form that exaggerates so many dynamics of human life turns to science for real, explainable causes to push the plot forward.
But perhaps it is not so surprising: Forensic science plays the same role in any number of popular crime dramas today. Even when we are being entertained, suspending disbelief about so many things that are necessarily artificial on stage or on television, we seem to crave just a little dose of logic.
"We like things in due place; we like to have explanations for things," André said. "Poison is something that we fear, and probably that's why it's so fascinating."