help my kid drop acid (on plants)

November 15, 2008 10:04 AM

ScienceProjectFilter: What household chemicals can my son use to simulate acid rain for a science project?

We need nonorganic acids that would remain in the soil like "real" acid rain (I'm assuming lemons and vinegar won't work because they'll break down). His control will be watered with neutral water, then he'll have samples to be watered with 5.6 pH, 4.9 pH, and 3.9 pH (I might not have those numbers right but you get the idea). He'll be logging the soil pH for three weeks.

Suggestions for nonorganic alkaline substances would be good too, in case we need them to get the pH just right. But mostly we need to create acid rain. I'm happy to shop at Home Depot for what we need, but I don't want to break the bank or buy huge lots of chemicals I'll never use again.

Also, battery acid is not an option, since another kid wanted to do a battery acid-related experiment & the teacher rejected the idea.

posted by headnsouth to science & nature (10 comments total)

You should be able to find hydrochloric acid (muriatic acid) at a hardware store. Use baking soda to neutralize it. Also, keep the baking soda within arm's reach whenever you're working with the acid in case it spills.
posted by martinX's bellbottoms at 10:23 AM on November 15, 2008

You can buy HCl at most hardware stores under the name muriatic acid. Lye is NaOH, a strong base if you need to neutralize some acid to raise the pH, in order to get it just right.
posted by Bahro at 10:25 AM on November 15, 2008

Also, you don't mention how old your son is or how much lab experience he has but I should point that if you haven't already, it would be a really good idea to do some safety research before you start messing around with strong acids and bases.
posted by martinX's bellbottoms at 10:34 AM on November 15, 2008

If the teacher rejects acids from hardware stores as too dangerous, phosphoric acid is inorganic, and used to flavour cola - Wikipedia tells me it's known as E338. Even the most liability-paranoid teacher couldn't object to an experiment using cola.
posted by Mike1024 at 10:35 AM on November 15, 2008 [1 favorite has favorites]

Ah, sorry martinX's bellbottoms, he's 13 (or will be next Wednesday--happy birthday, peanut!) and it's an 8th-grade honors science class.
posted by headnsouth at 10:46 AM on November 15, 2008

Why do you think vinegar would break down? This experiment from the EPA uses vinegar and baking soda to simulate acid rain on plant cuttings. The experiment follows for two weeks, so it's at least that stable.

In fact, on a quick google, it looks like all the hits coming back for "simulate acid rain" call for vinegar or lemon juice.

I work with adults. I just had to send an adult to the nurse while doing a lab with hydrochloric acid. This is not the first time I've witnessed educated adults do stupid things with strong acids (and bases.) Your son is probably very smart, but I'd stick with the vinegar if at all possible.
posted by arabelladragon at 10:56 AM on November 15, 2008 [2 favorites has favorites]

I agree that acetic acid should be sufficient, and it's a hell of a lot safer than HCl.

By the way, real acid rain is made acidic by sulfuric acid, which is what is found in car batteries, but I don't recommend you use that one either.
posted by Class Goat at 11:19 AM on November 15, 2008

When I was an undergrad and doing Illegal Things with Chemicals, I was able to find sulfuric acid drain opener at the nearest hardware store. Adds a layer of realism to the experiment, but the concentrated product will rapidly dissolve skin / tissue if you spill it and is a major safety concern. You can dilute it down to something as strong as table vinegar and it will still be useful for such a project.

I guess I'd say that you can find sulfuric acid, but please don't.
posted by a robot made out of meat at 6:58 PM on November 15, 2008

I order to get any stable pH of a distilled water solution you will want to use phosphoric acid. DI water is pH 5 with a trivially small amount of sulfuric or nitric acid in it so even trying to get your 3 pH's will be impossible. I can go into the calculation, but it isn't necessary and would just go with Phosphate.
posted by koolkat at 1:56 AM on November 17, 2008

Thanks everyone for your advice. He used varying amounts of vinegar in spray bottles. The pH did change in the spray bottles over the three weeks of the project, so he tweaked it as needed. Earned an A, yay! More exciting than that, he just got accepted into our region's Governor's School, a competitive math/science high school where he'll learn everything he needs to know to answer future science- and math-related AskMes!
posted by headnsouth at 5:13 PM on March 20