The smell that controls your life

Today’s breakfast came with an aroma of chlorine.

Not in the chic “croissant beside a rooftop infinity pool” way, but in that faint, clingy, leisure-centre chemical way.

The smell that sneaks into your hair, colonises your towel, and, apparently, clings to your children as they march out the door for school.

Kiss their foreheads and instead of parental tenderness you get reminders of Thursday night swim training and the soggy kit still lounging by the washing machine.

I’ve been there. Year 7 form room, chin propped on chlorine-scented hands despite post-pool shower, wondering if I’d fused with the pool overnight. I’d sneak a sniff of my hair (as subtly as an 11-year-old can) and wonder whether chlorine was just still on me, or had seeped into my DNA.

That’s chlorine for you. Less “Eau de Chanel” and more “Eau de Swim Club”.

But chlorine is far more than a poolside sensory assault: it sits in that fascinating grey zone between life-saving and life-threatening.

The paradox of chlorine is striking.

In high concentrations, it’s a suffocating poison and was the world’s first chemical weapon, unleashed in the trenches of World War I. Yet in controlled doses, it’s the reason you can sip water without also sipping cholera.

Chlorine is both a guardian and an executioner. The Jekyll and Hyde of the Periodic Table.

And the secret to its production? A GCSE experiment most of us have dismissed as forgettable fizzing in a beaker.

If you’ve ever sat through a chemistry class with graphite electrodes fizzing in a beaker of salty water, you’ll know electrolysis doesn’t exactly scream thrilling. At GCSE level, it’s just bubbles, half-equations, and the eternal confusion about which gas comes off at which electrode.

But zoom out, and that exact process powers one of the most important industrial chemical reactions in history:

The chlor-alkali process.

Pass electricity through brine, and you get three things — chlorine, hydrogen, and sodium hydroxide.

Unsexy names, yes. But between them? They prop up entire economies.

Your slightly underwhelming school experiment is, in fact, the backbone of modern civilisation.

If you fancy tumbling down a supercurricular rabbit hole:

In Deborah Blum’s The Poisoner’s Handbook, chlorine’s story is one of forensic chemistry racing against crime.

In environmental debates, it’s the villain behind CFCs tearing holes in the ozone layer.

And in medicine, it’s woven into countless pharmaceuticals. Take Chloramphenicol: without its chlorine atom, it’s a dud. Add that atom, and it latches onto bacterial ribosomes, transforming into a broad-spectrum antibiotic that has saved millions of lives.

Chlorine has also been part of the manufacturing process for a myriad of items in your house right now — not lurking as a bottle of bleach (though, yes, that too), but ghosting through the manufacturing of things you wouldn’t expect.

• PVC pipes quietly ferrying your clean water (ironic, really).
• Plastic casings protecting your laptop charger and gadgets.
• Paper bleached to a dazzling, almost smug whiteness.
• Disinfectants and sprays standing at attention under the kitchen sink.
• Paints and adhesives forming the invisible scaffolding of your home.
• Pharmaceuticals — painkillers, antiseptics, antibiotics.
• Circuit boards silently powering the devices keeping you entertained.

In short: if you’re reading this indoors, chlorine chemistry is literally surrounding you.

And that’s why all of this matters.

We often treat GCSE science like a hoop to jump through: memorise the equations, spit them out in June, forget them by July.

But every so often, a topic turns out to be far bigger than the curriculum hints.

Electrolysis isn’t just fizzing electrodes; it’s sanitation, plastics, medicine, electronics and civilisation itself.

And chlorine, that sharp poolside smell, becomes a reminder of science’s moral tightrope: the same process that gives us antibiotics also once gave us gas attacks.

Which should make you wonder: what else in the school syllabus is quietly running the world while we’re too busy yawning in double science?

Nici