Fizzing the floors

A reader writes:

My mom's always been a strong proponent of vinegar as a miracle cleaner for almost anything, floors, windows, clothes, you name it. She recently discovered bicarbonate of soda, too, and has been using that for all sorts of stuff too, like in the dishwasher instead of the special powder.

When I visited the other day, she was washing the floors with a bucket that had hot water, bicarbonate of soda AND vinegar in it. Apparently the fizz when you add the vinegar gives you more "scrubbing bubbles". Except I vaguely remember from elementary school that an acid and a base cancel each other out, the example given having been exactly this, vinegar and washing soda.

So was my mom just washing the floor with salty water?



Vinegar and bicarbonate of soda are indeed the standard boringly-safe-science demonstration of an acid and a base neutralising, and the reaction does produce a salt, but not table salt.

Bicarb is NaHCO3, acetic acid is CH3CO2H. Acetic is the acid in vinegar - cheap "white vinegar", which is rather more economical for cleaning things than 50-year-old balsamic, contains nothing but nice clean industrial acetic acid and water.

The reaction is:

NaHCO3 + CH3CO2H -> CH3COONa + H2O + CO2

Those products are sodium acetate, water and carbon dioxide. The CO2 is invisible but heavier than air, and can be poured out of the reaction container to extinguish a candle, said candle being the most dangerous thing that exists in boringly-safe-science demonstrations.

Sodium acetate is sometimes used as a flavouring, because it tastes like salt and vinegar all by itself. ("Salt and vinegar" snacks in the USA are apparently likely to be flavoured with sodium acetate; here in Australia I think that's illegal for some reason. I don't think it's toxicity; sodium acetate is pretty innocuous.)

If you mix sodium bicarbonate and hydrochloric acid, HCl, then the reaction is the same except instead of sodium acetate, you get sodium chloride, which is everyday table salt.

(For this reason, bicarb is a very effective antacid. A teaspoon full of bicarb can turn nasty acid-reflux indigestion into a series of hugely satisfying CO2 belches in seconds. You'll have a pretty darn high-sodium diet, though, if like me you end up eating several spoonfulls of the not-that-bad-tasting-when-you-get-used-to-it substance per day. In that case, hie thee to a doctor and get yourself a prescription for one or another acid-production-reducing drug.)

You'd want to be careful making salt from bicarb and hydrochloric acid, though, because if you don't get your stoichiometry right and not add balanced amounts of the reagents, then there'll be left-over bicarb or hydrochloric acid at the end. This is also what will happen if someone decides to make a cleaning product out of bicarb and vinegar; they probably won't titrate the mixture, and so will have a surplus of one substance or the other. Surplus bicarb, as a base, will clean greasy things by, essentially, turning the grease into soap. Surplus vinegar, as an acid, will clean things by dissolving various kinds of dirt, like mineral deposits ("scale"), or rust.

For these reasons, and also the fact that plain water plus elbow grease can clean a lot of things pretty effectively (the basis for the popularity of "laundry balls", which don't actually do anything), people may come to the conclusion that a vinegar-and-bicarb concoction is a super cleaner, when in fact they'd be better off using a smaller amount of only one of the ingredients.

(At least, in this case, mixing the compounds will do no harm. Mixing bleach and ammonia, on the other hand, may greatly reduce the amount of time you spend doing household chores, on account of how you may now be dead.)

Oh, and sodium bicarbonate is not "washing soda"; that's sodium carbonate, Na2CO3, which is commonly used to "soften" hard water, which contains dissolved minerals that prevent soap from working properly. Sodium bicarbonate is "baking soda", named for its use as a leavening agent; if you mix bicarb into batter that's slightly acidic, the fizzy-neutralisation reaction occurs and creates lots of little CO2 bubbles in the batter. "Baking powder" contains dry bicarb and acid powder (usually tartaric acid). Add water, and the components react and fizz.

(See also, the delightfully popular recipe for "Swedish Lemon Angels".)

Getting back to sodium acetate, a supersaturated solution of it is used in "phase change" heat packs...

...which "freeze", liberating heat, when disturbed with the little clicker device inside, or when otherwise slapped around. You put the pouch in boiling water to re-liquefy its contents; the things can be used over and over indefinitely, as long as they don't spring a leak.

You can do something similar to this with numerous other fluids, but sodium acetate's properties suit it very well to the purpose. Even if you don't actually need a hand-warmer, I strongly recommend you buy one as a toy, since you can get them on eBay for about $5 delivered.

Psycho Science is a regular feature here. Ask me your science questions, and I'll answer them. Probably.

And then commenters will, I hope, correct at least the most obvious flaws in my answer.

8 Responses to “Fizzing the floors”

  1. Anne Says:

    Interestingly, of the various not-very-toxic quasi-natural products one might have around the home, apparently lemon oil makes a really rather good grease-cutting cleaner. And here I always thought that "lemon-scented" was just cosmetic.

    It also makes a mediocre rocket fuel, by the way:

    One of the oddest combinations to be investigated was tried by RMI, who burned d-limonene with [white fuming nitric acid]. d-limonene is a terpene which can be extracted from the skins of citrus fruits, and all during the runs the test area was blanketed with a delightful odor of lemon oil. The contrast with the odors of most other rocket propellants makes the event worth recording.
    — John D. Clark, "Ignition!"

  2. TwoHedWlf Says:

    You can also just buy sodium acetate powder for about $20/kg. Then you can have bowls of sodium acetate solution all over the kitchen just waiting for someone to poke them and turn it into hot ice. That earned me a series of eye rolls from the wife.

  3. Fallingwater Says:

    Bubble: "I wonder what this white stuff is? Maybe if I touch it..."
    *bubble reaches closer, touches the expanding white crystals*
    "What the... oh no, it's getting all over me! Help! Get it off! Aaaarrrgh!" *dies*

    • TwoHedWlf Says:

      It looks like just a container of water until you touch it. If you move the container it's obviously much thicker than water though.

  4. Major Malfunction Says:

    If you can get your hands on some pure ethanol you can make yourself my interpretation of a Pangalactic Gargle Blaster. You pour a measure of your ethanol, and add a teaspoon of bicarb, and a teaspoon of citric acid. Now you fill the glass with water, stir vigorously, and scull!

    It really is like "having your brain smashed out by a slice of lemon wrapped round a large gold brick!"

  5. Jhong Says:

    I wonder if there is any way to electrically activate sodium acetate (a piezo element maybe?). It'd make for a really interesting art installation -- a big container of acetate that is repeatedly cooled, activated, then reheated.

    • Anne Says:

      I'd skip the electrical triggering and put the thing out there where people could poke at it. So it sits there, looking innocuous, until some kid pokes it, at which point crystals start forming, it gets hot, and the parent rushes them out hoping nobody notices they've ruined an exhibit. Then the electrical circuitry measuring the temperature kicks in and heats it enough to dissolve the sodium acetate, then lets it cool and lurk again.

  6. trab Says:

    Sodium Acetates (E262) are definitely allowed in food in Australia and New Zealand, Source:

    Ammonium, Calcium & Potassium Acetates are also allowed.

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