The Safest Way To Dilute Household Chemicals

Making a DIY disinfectant is as simple as mixing bleach (or alcohol) with a little water—but for safety reasons, the order in which you mix them matters more than you might think. As you’re mixing up your next batch of coronavirus-busting spray, let the first commandment of Chem 101 labs be your guiding principle: “Do what you oughta—add acid to water.”

Diluting certain acids produces a lot of heat, which makes this deceptively cute lil’ mnemonic incredibly important in a lab setting. Pouring water into concentrated acid generates too much heat way too quickly, which can cause the solution to bubble up or explode; adding the acid to the water instead slows the reaction process down enough that everything stays where it belongs.

The same strategy applies to household chemicals—even those that aren’t acidic at all—but for slightly different reasons. Whenever you pour one liquid into another, there’s usually at least some initial splash back—and if you’re pouring water into a chemical, the displaced liquid flying up at your unprotected eyeballs will mostly be that chemical. (This is even more likely to happen if you crank the tap full blast and stick a mostly-empty container of bleach underneath.) By reversing the order, you ensure the splash back is mostly water, which is significantly less hazardous to exposed skin and mucous membranes.

If all this sounds like hall monitor levels of safety overkill, consider that an unexpected trip to the ER has never been more dangerous than it is right now—and, for once, prevention could not be simpler. Bleach, ammonia, isopropyl alcohol, and vinegar may not be as dangerous to handle as strong acids, but treating them like they are anyway is a very good idea. Stay safe out there, and always remember to do what you oughta.