Chemistry: Explosive moments in the laboratory

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Mark Peplow surveys a gorgeous gala of reactions in Theodore Gray's new book.

Reactions: An Illustrated Exploration of Elements, Molecules, and Change in the Universe

Theodore Gray Black Dog & Leventhal: 2017. ISBN: 9780316391221

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Nick Mann

Aluminium foil reacts with bromine.

For Theodore Gray, chemical reactions are “a sort of nanoscale fight club”. In Reactions, the chemist, science writer and technologist offers a lavishly illustrated tour of this molecular battleground, full of wit and wonder.

Gray's career as a chemical evangelist began in 2002, when he misread a line in Oliver Sacks's Uncle Tungsten (Knopf, 2001) and imagined the periodic table of elements as a literal table. A skilled woodworker, Gray decided to build it and stock cavities beneath each symbol with samples of the elements.

Then, he recalls, “things really got out of hand” ( The table won the 2002 Ig Nobel Prize in Chemistry, and spawned a cottage industry: Gray now sells periodic-table posters, books and quilts, and makes museum displays. With photographer Nick Mann, he has amassed a gallery of element photos, showcased in his 2009 book The Elements. Its sequel, Molecules, followed in 2014; Reactions is the final part of the trilogy (all published by Black Dog & Leventhal).

Gray's enthusiasm shines in Reactions. Take the humble glow stick, which mixes two precursors to generate a peroxyacid ester that jolts a dye into emitting light. Of this, an object available at petrol stations for a pittance, he urges: “I insist that you be amazed.” The text is peppered with dry asides, and a grumpy disdain for anything unscientific. Homeopathy he brands authorized lying; claims for 'chemical-free' health foods irk him. Even steampunk — gadgetry with a Victorian aesthetic — draws his ire, because “none of the things these people make actually work”.

So far, so enticing. Yet the book struggles to sustain momentum because it lacks a narrative. In The Elements, the organizing principle was obvious: it was a beautiful catalogue of the building blocks of matter, ordered by atomic number and full of fascinating facts. But chemical reactions are messy and multitudinous. It can be hugely challenging to explain why they occur, and to choose which to include.

Reactions leans heavily on combustion and explosion — understandable, given its visual emphasis. As a result, some of it feels samey. Plenty of other glamorous reactions could have illustrated different concepts, from the redox chemistry behind the spectacular ammonium dichromate 'volcano', to the catalytic decomposition of hydrogen peroxide used to create 'elephant's toothpaste' — a foam fountain beloved of science demonstrators.

When Gray settles on a subject, he can provide genuine insight, as in sections on the anatomy of fireworks or the composition of paints. But too often, the coverage is frustratingly superficial. In the sole example from the vast field of synthetic organic chemistry, he outlines the total synthesis of the alkaloid physostigmine, yet divulges nothing about why it is useful — it's a treatment for glaucoma. And although the diagrams that show its step-by-step construction create an impression of complexity, Gray doesn't begin to explain why this particular route is a cunning way to knit together a molecule. It's enough to spark, but not sate, curiosity.

Delving into the principles behind reactions, Gray follows the Sun's energy from chlorophyll to plant carbohydrates, and onwards to oil, petrol and the chemistry of the internal-combustion engine. This discussion of energy is straightforward (“an itch that the universe needs to scratch”); the coverage of entropy is more difficult to follow. “Feel free to skip this section, by the way: it's really hard,” he writes. From a science communicator, that feels like a cop-out.

There are brief mentions of how other factors — concentration, temperature, surface area — affect rates of reactions, but no unifying explanation of chemical kinetics to go with the thermodynamics. Catalysis, surely one of the most important principles of modern chemistry, is notably absent.

Still, it feels churlish to gripe about this love letter. Mann's photography transforms chemical samples into art, and captures the thrill of Gray's demonstrations. Many photos recall the works of eighteenth-century artist Joseph Wright, using chiaroscuro to frame the glow of a reaction with a background of deep shadow. Others are playful: in one, chlorine gas combines with sodium metal to create a billow of sodium chloride, which rises to vaporously salt a net full of popcorn.

The pictorial treats go beyond photography. Molecular structures are bathed in a diffuse violet glow, the shimmer serving as a reminder that their shroud of electrons is a cloud, not a constellation of points. And the most attractive chapter, on the chemistry of light, draws a beautiful analogy between sound waves and musical notes, and electromagnetic wavelengths and colour.

There are gorgeous sequences of stills from high-definition video, such as one showing the hellish cauldron created when aluminium meets bromine. I had an urge to jab the page to make it play. Indeed, Gray's previous works have been ported, extremely successfully, into iPad apps, with multimedia that users can manipulate. I expect that Reactions will make the same transition. For now, it feels like an app trapped inside the body of a book.

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