Baking Soda Chemistry: how much....
October 9, 2019 3:18 PM   Subscribe

I want to use baking soda and vinegar to produce carbon dioxide bubbles. The grocery store vinegar is described as having 5% acidity (not how it would be described in chem class!). How much baking soda should I use for, say, 1 quart of vinegar?

This is a home plumbing hack to create some fizz in a drain in hope of clearing a clog. I could always use an excess of baking soda, but I'd like to be efficient. The soda gets dissolved in water, and the vinegar and soda solutions are poured down the drain one after the other. I'm thinking the vinegar should go first but I'm open to advice.
posted by SemiSalt to Home & Garden (14 answers total)
 
I usually dump about a half cup of baking soda (dry) down the drain and then pour vinegar slowly till the solution stops fizzing, and repeat until the drain is clear. If it doesn't clear in a 3-4 repeats, I get out the snake.
posted by General Malaise at 3:48 PM on October 9


You have two choices:

The perfect stoichiometric ratio that will leave no baking soda left over (around 70 grams for a liter of vinegar).

A lot more than that, to make it happen quickly, because slow gentle bubbling probably won't accomplish much (in my experience, neither will fast vigorous bubbling, but some people swear by it).
posted by Dr.Enormous at 4:13 PM on October 9 [4 favorites]


I think the baking soda alone may be doing the work as an alkali on soap, skin and hair clogs. I pour some in a wet drain and leave it for half an hour. You can rinse with vinegar if you like but hot water might work as well.
posted by Botanizer at 4:31 PM on October 9 [1 favorite]


Ok, let's see if Google plus whatever remnants of high school chemistry are still rattling around in my head are sufficient to solve this.

1) First, we look up what the reaction of acetic acid and sodium bicarbonate looks like (e.g.: here) and find that it looks like something like this:

NaHCO3 + HC2H3O2 (aq) → NaC2H3O2 (aq) + H2O (l) + CO2 (g)

The only part I care about, however, is the left hand side. Specifically, it looks like the reaction involves one molecule of acetic acid and one molecule of sodium bicarbonate.

2) We can look up the molar masses of acetic acid and sodium bicarbonate on Wikipedia, obtaining 60.052 g/mol and 84.0066 g/mol, respectively. So, what we want then is a roughly 60:84 ratio by mass between the acetic acid and baking soda.

3) Also on the Wiki page for acetic acid, we find that its density is around 1.05 g/ml . This is pretty close to the density of water (1.0 g/ml), so we probably don't have to worry if the "5% acidity" really means 5% by volume or by mass. So, we infer that one quart of this vinegar contains about just under 50 grams of acetic acid (1.05 g/ml * 5% * 946.53 ml/quart).

4) So, to figure out how much baking soda we need, we just apply the 60:84 ratio to 50 grams (i.e.: setting 60/84= 50/x and solving for x) and conclude that we need 70 grams of sodium bicarbonate.

Perhaps someone with better chemistry background can double-check this calculation?

(Also, personally, I've found that boiling hot water can sometimes also be an effective drain opener, depending on the nature of the clog.)
posted by mhum at 4:55 PM on October 9 [2 favorites]


Oh wait. I just saw that Dr.Enormous already got there earlier.
posted by mhum at 5:19 PM on October 9


I do this all the time. Just dump in the baking soda first and then pour in the vinegar. Both are exceptionally cheap.
posted by Admiral Haddock at 5:21 PM on October 9 [2 favorites]


I agree you should add the vinegar first, with this rationale: vinegar is slightly more dense than water, so even if there's water above the clog, the vinegar will go through it to sit atop the clog and displace water even from within the clog itself to some extent.

Then when you add the baking soda solution (without waiting so long that the vinegar mixes too much with water above the clog), since the baking soda solution is even denser than the vinegar, it will flow through to the clog and react with the vinegar in the clog itself, and that effervescence will tend to break up the upper part of the clog.

I once broke up a stubborn clog by cutting the valve out of an old bike innertube so that there was a circular piece of rubber around it, then asking a friend to hold it down in the drain opening with a can that had both ends cut out of it, adding an inch of water in the sink, and then attaching the pump to the valve and pumping til the clog cleared. Which took less than a minute.
posted by jamjam at 5:35 PM on October 9 [1 favorite]


I’m a HS chemistry teacher. Baking soda and vinegar neutralize each other, essentially making water and a salt called sodium acetate. The bubbling reaction might loosen a little crud, but it looks a lot more exciting than it is. I know a search gets you a zillion advice columns on this “miracle”, but this article makes the most sense to me - and it concludes that it’s an ineffective technique. I’ve had the most luck clearing clogs with one of those hose gadgets that creates a blast of water pressure.
posted by chr1sb0y at 3:09 AM on October 10 [2 favorites]


Thanks to DrEnormous and mhum for answers to my direct question, and to everyone else for your advice. I should explain that I never expected this to work, but I felt constrained to try. It's a shower drain, and I was unable to remove the grate and unwilling to use any kind of strong chemical in a way that could spill on the shower floor. It's not a complete clog, just clogged enough for shower water to collect at your feet.

I tried 35g (between 3T and 4T) of baking soda dissolved in 3 cups of water and heated to near boiling, followed by 2 cups of vinegar + 1 cup water, also heated to near boiling. That was all followed by copious hot water. And I used a plunger. I perceive no change.

Thanks to chr1sb0y for the link. Mostly, I think the material in the article makes sense, but I'm really skeptical of the advice to use boiling water. On one hand, carrying large amounts of scalding water the length of the house and up the stairs doesn't seem very safe, and on the other hand the whole use profile of a shower drain is to remove hot water with soap/detergent in it. If hot water worked, normal use would work. I'd be interested in a link to your hose gadget.

This morning I was able to remove the grate. Another lesson that having the exact correct screwdriver is sometimes the key to success.

We've lived in this house since 1976, and it's always been a terrible drain, never going more than a couple years without a clog. I'm wondering if having a plumber replace the galvanized pipe with more slippery plastic pipe would be worthwhile.
posted by SemiSalt at 7:26 AM on October 10 [1 favorite]


This may be obvious, but for slow shower drains, using a zip it is almost always more effective than plunging. Pull up some matted accumulated hair gunk (it's mixed with dead skin and soap scum!) and then flush with water/vinegar/baking soda.
posted by desuetude at 8:29 AM on October 10 [2 favorites]


If it's a shower drain, it's likely blocked by a delightful gloppy mix of soap crud, hairs and biofilm (aka microbes that live on soap crud and hair/skin cells). Unless you can get the bicarb deep into the crud layer to get it to spall off, all you're doing is tickling it slightly.

Mechanical removal plus boiling water and bleach (yes, the good chlorine kind that kills things: that is the point of this exercise) is how you move this.

There's also a chance that you've got something physically blocking the pipe. Our slow bathroom sink was found to have three quarters, a cent, five safety pins, two razor blades, some q-tips and a pulverized lightbulb in the trap.
posted by scruss at 8:33 AM on October 10


Are you adverse to using an enzymatic/ chemical drain cleaner? I really like Drano's Max Gel - pour it in, let it sit for half an hour, flush with hot water from the faucet for five minutes.

Repeat if necessary. The residual heat from the hot water flush will help increase the speed of the chemical (and probably enzymatic) reaction.
posted by porpoise at 11:08 AM on October 10


Does your house have drum traps? Replacing those with real P-traps did a wonder in our house.
posted by epanalepsis at 12:32 PM on October 10


Porpoise, I'm trying one of the two part foaming drain cleaners now, because I've had some luck with them in the past with these not-quite-completely-stoppered situations in the past, but a bought a bottle of Max Gel as backup.
posted by SemiSalt at 1:09 PM on October 10


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