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What are the general ways to treat an accident involving highly concentrated or similarly dangerous acids?

I have a lab instructor who recently debated with our group about treating an acid spill on the skin. According to him, one should immediately rinse off the acid with running water for about 15-20 minutes. He says that one should never apply bases to the site because an Acid-Base is highly exothermic and would only increase the damage.

However, I clearly remember learning once that one should apply baking soda (sodium bicarbonate) to a bee sting or ant bite in order to neutralize the acid and relieve the burning. I also know that the dilution of an acid in water is done by adding the acid slowly to the water containing vessel because of the heat released in the process. And especially when preparing a dilute solution of sulfuric acid, one wears safety goggles and gently stirs the solution to prevent splashing.

So which is it? And does it depend on the severity of the burn or type acid?

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    $\begingroup$ And ant bee stings are not "highly concentrated or similarly dangerous acids" so there's no reason to suppose that folk remedies for stings have any application to chemical spills. (Well, OK, stings are "similarly dangerous" if you're allergic to them but that's not what you're asking about.) $\endgroup$
    – David Richerby
    Aug 14, 2015 at 12:10
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    $\begingroup$ What's the source of your "very inexperienced" prejudice? $\endgroup$
    – Etheryte
    Aug 14, 2015 at 15:34
  • $\begingroup$ @Nit He sounded very unsure of himself and is new around here. So the description is just based on judgement. $\endgroup$
    – tkhanna42
    Aug 15, 2015 at 5:22
  • $\begingroup$ @tennispro1213 A lot of the most competent scientists I know tend to "sound unsure of [themselves]." Clearly, he knew what he was talking about here. Maybe you should have a little faith that he got to where he is with a lot of experiences along the way. $\endgroup$
    – SendersReagent
    Apr 15, 2016 at 0:56

5 Answers 5

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My Lab First Aid book$^{*1}$ tells the following:

The local therapy mainly consists of the instant, intense rinsing (at least 10 minutes) with tap water (ideally 15 to 20 °C). Don't try to neutralize the chemical burn, because the heat generation could lead to further tissue damages.

This means, that your lab instructor is absolutely right.

The rinsing water should wash the cold water away faster than the heat from the acid base reaction could harm you. It's not for nothing that there are emergency showers and eye douches in every lab.

I have a friend who is a chemical lab assistant and once had to carry concentrated sulfuric acid in a big glass beaker. Suddenly the bottom of the beaker broke off and all the acid poured over her etc. She not even thought of anything else than getting out of her clothes and under the next emergency shower.

$^{*1}$ The book is: R. Rossi, Erste hilfe bei akuten Notfällen - Begleitheft zu Jander - Blasius, S. Hirzel Verlag, 2005, p. 11f.. The text is in german and I translated it.

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    $\begingroup$ Rinsing is the most proper way and should be totally automatic (experience acquired by suffering with normal heat burns). Later "neutralizing" with diluted bicarbonate solution should not harm, but first rinse. Do not think what chemical I have to dilute in which concentration, etc... every second matters! $\endgroup$
    – ssavec
    Aug 13, 2015 at 11:36
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    $\begingroup$ I once asked a fire fighter if they use any kind of chemicals for decon-p, and he basically said "Nah, we just put as much water on the person as we can. Dilution neutralizes everything." $\endgroup$
    – hiergiltdiestfu
    Aug 14, 2015 at 8:48
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Speaking from experience.

Minor spills (drops) on skin of concentrated nitric or sulfuric acid are nothing to speak of. Wash them off with plenty of water for a minute or two and you are fine. I'm pretty sure that this is the case for phosphoric acid as well. Hydrochloric acid is a bit more troublesome, mosly because it fumes intensively, but still nothing spectacular.

A common aftereffect of small nitric acid spills is local skin yellow coloring and a quickened loss of upper layer with fresh skin below. Again, nothing to panic about.

These acids cause proteins to denaturate, forming strong barriers for further diffusion into skin. As such, short contact with skin is safe as long as the acid is immediately washed off and the skin is undamaged. Diluted (0.1-0.5 M) hydrochloric acid is so tame, it is pretty safe to wash briefly glassware in it without gloves.

There are, however, acids, that are trouble. One is glacial acetic acid. It diffuses rather readily through lipid membranes and may cause deep, troublesome chemical burns requiring special treatment.

Also, note that while our skin is surprisingly resilient, our mucous membranes, and eyes in particular are not. Even one unlucky drop may require special help.

So, summing up. Wash off sulfuric acid, nitric acid and hydrochloric acid, but as long as the contact is brief and small, it is nothing to care about. Longer and/or wider contacts should get medical attention.

Wash longer acetic acid, formic acid.

Generally avoid (and I mean it) hydrofluoric acid and derivitives (toxin, rapidly diffusing through sking) and $\ce{HClO4}$ (may form explosives on storage)

BY ALL COSTS PROTECT YOUR EYES. THEY CANNOT BE REPAIRED.

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To add to @PH13's answer, according to the Texas A&M University's page Safety Guidelines, that rinsing is crucial, from the site:

Chemicals may cause severe burns. Immediately flush skin with cold water. Remove contaminated clothing (including socks and shoes) and rinse at least 10x as long as the chemical was in contact with the skin.

However, as all chemicals, including acids, have differences in how they react, it is crucial to be aware of the first-aid guidelines laid out in the Materials Safety Data Sheet (MSDS):

Read the MSDS sheets and product labels to learn the first aid procedures, health hazards and physical hazards for the chemicals used in each exercise.

This should be done as part of the lab preparation and hazard assessment, also to have on hand in case of emergencies such as a spill on skin or in the eyes.

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Skin is fairly resistant to acids. Rinse it off with water for a minute and you're good. Everything that has already penetrated the skin (nitrous gases, HCl, HF(!)) will not be removed by washing afterwards. Further cooling might keep the swelling and inflammation down, of course.

There is ONE exception: Wipe off conc. $\ce{H2SO4}$ with a dry piece of cloth (or with anything dry) before applying water. Otherwise you'll get a severe burn.

Bases take longer to wash off, they enter the skin more easily (by dissolving it).

Never try to neutralize anything, it takes much longer than jumping under the emergency shower, is totally useless and likely dangerous, too.

But how does an "inexperienced" lab instructor discuss this with you? This is a subject for a very serious, compulsory lecture by the responsible head of laboratory, before anyone as much as opens a lab door!

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  • $\begingroup$ He's still at the student level and since the actual instructor wasn't available yet, my group decided to talk to him...also, I thought of the example of sulfuric acid the whole time when he was explaining. I didn't realize it was an exception. Thanks a lot! $\endgroup$
    – tkhanna42
    Aug 13, 2015 at 14:01
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    $\begingroup$ Conc. sulfuric acid is not so much an acid as an extremely vigorous desiccator. That makes it very dangerous for your eyes. On dry skin, it sucks the last bit of water out of the topmost dead layer, and then basically nothing. Proteins take long to dissolve in acids. If you want to see how evil the stuff really is, put a drop on a piece of cotton or a paper napkin. And do that in the fume hood and remove anything flamable from the vincinity. $\endgroup$
    – Karl
    Aug 13, 2015 at 15:09
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There’s another key point why rinsing immediately and for a significant time is better than attempting to neutralise and it does fully support the heat argument.

When you attempt to neutralise acid spills, e.g. with hydrogencarbonate, the solid will stay on your skin and react only there. That means, the heat is generated right where you already spilt the acid and probably already have a mild burn. And there is nowhere the heat could go because none of the reactants will move.

If you neutralise with lots of water, yes, a lot of heat will be generated. But this heat will heat up the water which flows away. So even though you are generating a lot of heat, you are also creating an equally efficient heat-removal mechanism; and because you should rinse at least five minutes this will mean much less heat damage can be done to the skin in question.

Bee stings are very different in this regard. The amount of acid is very small and it has already somewhat penetrated the skin through the action of the sting (as opposed to just being on top as with an acid spill in the lab). The neutralisation will not generate as much heat because there is not that much acid, but rinsing with water is much less effective because the water is much less effective at actually getting to the acid itself.

Therefore, for two different accidents two vastly different treatment methods can both be correct (as long as you use the right one at the right time).

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