We all know chlorine (Cl) from swimming pools. The smell associated with such places is actually a chlorine compound called chloramine (NH₂Cl) which is a result of chlorine reacting with amino acids (in human hair, skin, sweat, etc.).

Although in pure gaseous form chlorine is both corrosive and toxic, it is essential to life. Chlorine compounds and ions are part of numerous biological processes. The most obvious one is the role of salt (sodium chloride, NaCl) and its ions in physiology. The hydrochloric acid (HCl) in our gastric juices that helps us digest proteins is another example.

At home we all know about bleach which is also a chlorine compound (sodium hypochlorite, NaOCl). We all know not to mix bleach with other household chemicals as both acids (like vinegar) and ammonia products will react with it to release chlorine gas. At least I hope we know this!

Chlorine is obviously used to disinfect municipal water supplies. This has been a great boon to civilization. We take for granted in this country our access to nearly unlimited supplies of safe drinking water. It’s not that way in a lot of places!

Chlorine is essential to the production of plastics, particularly polyvinyl chlorides. These are everywhere. Finding substitutes for plastics is no easy task. But we’ll have to figure out ways to make renewable and/or recyclable plastics. We can’t keep piling up old plastics in our landfills. Or garbage-patching our oceans, polluting our rivers, or contaminating our aquifers, either. Chlorine is necessary for chlorofluorocarbons, chemicals of great utility but with huge environmental impacts (like ozone depletion). The regulating of such CFCs was a proof that good things can happen on a global scale. If only we could do more of that.

You can get a pretty good idea about the wealth and standard of living of a country by looking at its consumption of chlorine. A good proxy is hydrogen chloride (HCl)*, a gas used industrially to produce hydrochloric acid. Hydrochloric acid is used in countless syntheses of other compounds and is critical to any industrial economy.

Chlorine gas (Cl₂) is made from the electrolysis of brines. Caustic soda (sodium hydroxide, NaOH) and hydrogen gas (H₂) are the (valuable) by-products. Statista tells me the worldwide production of chlorine in 2022 was 97 million tonnes.

HAPPY NEW YEAR!! May 2026 be healthy and prosperous for you and yours.

*Although the same formula is used for the gas (HCl) as for the acid (HCl), the acid is actually a liquid solution. The gas is bubbled through water to produce the liquid acid. Chemists typically specify the concentration of an HCl solution,for example, 1.0M HCl (“one molar”) is a common laboratory reagent.