The Skin's Natural Protection Against Caustic Chemicals

[JGM_14]

I didn't know where to put this since it pertains to both chemistry and biology so i put it here. One time i accedently spilt 31.45% concentrated HCl on my skin and didn't notice it right away but then i saw this fuming drop on my skin and i immediately washed it off, it never tingled, burned, left a mark ect. I was very surprised. I have never gotten a chemical burn in my life, nothing.
I have been working with caustic chemcals for 2yrs now and i have had multiple experiences like that. Can anyone tell me if our skin produces natural buffers that neutralise small amounts of caustic chemicals? I do not do these things intentionally in case anybody was wondering.

 

[DaveC426913]

Well, the top layers of your skin are dead, so if you wash it off quickly enough it might not damage living tissue.

 

[JGM_14]

that makes sense

 

[chemisttree]

This is actually a very common experience. Your skin is covered in oils and dead cells. The acids do not usually rapidly attack the oily layer. When you rinse these acids off your skin with water, it is possible to do so without disturbing this protective layer and there is no sensation or apparent damage. Some silicone-based hand creams used in the Chemistry lab augment this oily layer and protect the hands to some degree (not nearly as good as gloves though). If you were to be exposed to strong acid and vigorously wipe the material off without water you will have a very different experience! That said, very strong acids, like 98% H2SO4, can thermally burn you if you are significantly contaminated and apply water. This is usually only applicable if your clothing has been severely contaminated (dripping with the stuff). In that case, the safe course of action is to strip off the contaminated clothing (modesty be d*mned) before using the safety shower. When the acid does eventually make it past your skin's protective layer, the sensation is immediately significant and painful. Many acids are volatile enough to sting the eyes or the nose and are therefore quite 'sensable'.
This is also true for some bases like ammonia but is not the case for strong caustics (strong bases) like NaOH. These chemicals slowly dissolve skin and often manifest only mild discomfort (even in an eye exposure) while doing it. Sometimes the sensation is not significant enough to alert you to the exposure and thus these chemicals can stay in place for extended times. Later, when you wash all of the saponified skin away, the injury is much more apparent and painful. This is why caustics are much more dangerous to work with than strong acids.

 

[JGM_14]

thanks for the info

 

[Gokul43201]

This is related, so let me add a recent experience and solicit advice. Couple days ago, I had a drop of pretty potent solvent (about 1:1 phenol + methylene chloride) fall on my arm. It started burning immediately. And it took me about 15 - 20 seconds before I could get my arm under a tap and wash it off. Now I've got something that like looks like a scab there. Should I have done something more/different?

 

[chemisttree]

This is related, so let me add a recent experience and solicit advice. Couple days ago, I had a drop of pretty potent solvent (about 1:1 phenol + methylene chloride) fall on my arm. It started burning immediately. And it took me about 15 - 20 seconds before I could get my arm under a tap and wash it off. Now I've got something that like looks like a scab there. Should I have done something more/different?

Phenol is a pretty strong acid. In a defatting solvent like methylene chloride, the burn is immediate and time makes it worse. The only thing you can do to minimize this in the future is to apply a silicone barrier handcream (VWR Cat. # 21923-402) and use gloves. Rapid response is a must. Your University stockroom might have this barrier cream in its safety or PPO stores. Remember that most barrier creams are silicone based and will play havoc with pristine surfaces if it is used by personnel handling them or if it is used extensively by personnel in the same labspace... even gloved. Not sure if that applies to your situation.

What to do differently in the future? Perhaps apply triethanolamine (neat by cotton tip applicator) to the affected area after a thorough water rinse. Bicarb solution will also help solubilize this fairly greasy acid.

 

[JGM_14]

absorb the acid into a cloth until you can wash it off, but don't hold the cloth on it on the acid soaked part, i have found that this works most of the time

 

[mgb_phys]

strong caustics (strong bases) like NaOH. These chemicals slowly dissolve skin and often manifest only mild discomfort ... Later, when you wash all of the saponified skin away, the injury is much more apparent and painful

Been there-done that! It's also very impressive at dissolving cotton clothes.

Can anyone tell me why HF is so much more dangerous / feared than any other acid? Is there a mechanism for actual toxicity or is just it's strong acidity?

 

[Gokul43201]

Phenol is a pretty strong acid. In a defatting solvent like methylene chloride, the burn is immediate and time makes it worse. The only thing you can do to minimize this in the future is to apply a silicone barrier handcream (VWR Cat. # 21923-402) and use gloves. Rapid response is a must. Your University stockroom might have this barrier cream in its safety or PPO stores. Remember that most barrier creams are silicone based and will play havoc with pristine surfaces if it is used by personnel handling them or if it is used extensively by personnel in the same labspace... even gloved. Not sure if that applies to your situation.

I was wearing gloves, but they don't cover my upper forearms. I was actually considering Saran wrap on my arms!

What to do differently in the future? Perhaps apply triethanolamine (neat by cotton tip applicator) to the affected area after a thorough water rinse. Bicarb solution will also help solubilize this fairly greasy acid.

Not likely to find triethanolamine in a physics lab...bicarb may be sitting around in a dusty bottle under the sink, perhaps.

Thanks for the suggestions.

Can anyone tell me why HF is so much more dangerous / feared than any other acid? Is there a mechanism for actual toxicity or is just it's strong acidity?

HF is actually not a terribly strong acid.

https://www.physicsforums.com/showthread.php?t=61648

 

[mgb_phys]

Thanks - very interesting. My wife is a chemist, now I know why she hated the stuff so much!

 

[JGM_14]

He spilled it on his lap!? Sounds painful.

 

[chemisttree]

Can anyone tell me why HF is so much more dangerous / feared than any other acid? Is there a mechanism for actual toxicity or is just it's strong acidity?

HF is not a strong acid which makes it fairly easy to absorb right through your skin into your tissues. The burns it leaves are deep and dangerous. I've heard that it doesn't stop moving until it hits bone (and forms CaF2). That's a deeeeep burn. Get enough on you and your life is in danger. HF or any fluoride salt sequesters Ca+2 ions in your tissues and can stop your heart!

 

[chemisttree]

I was wearing gloves, but they don't cover my upper forearms. I was actually considering Saran wrap on my arms!

Thats why you see chemists walking around in lab coats (and holey bluejeans).
Ouch!

 

[Moonbear]

I was wearing gloves, but they don't cover my upper forearms. I was actually considering Saran wrap on my arms!

You can buy sleeve guards. Lab coats are supposed to be tightly woven material, but some of the cheaper ones are not particularly resistant to soaking through with spills, so even that is not enough of a safeguard when working with things like phenol. Right in the first section of either Fisher's or VWR's catalog (whichever your university has the better contract with) is the section on personal protective equipment. Look for the sleeve guards there. You can pull them on over your lab coat (and you ought to be wearing a lab coat with that stuff).

Phenol is also an inhalation hazard (if you can smell it, it's too concentrated in the air). We've had entire buildings evacuated for a milliliter or two of phenol spilled on the floor (or it might have been a phenol-chloroform mixture, which is commonly used for extraction/purification in molecular biology labs). That's one of those procedures I insist be done with at least two people present in the lab at all times.

 

[Gokul43201]

You can buy sleeve guards. Lab coats are supposed to be tightly woven material, but some of the cheaper ones are not particularly resistant to soaking through with spills, so even that is not enough of a safeguard when working with things like phenol.

I could have gone up to our cleanroom, four floors up, and grabbed a bunny suit that would've covered 99% of my surface area - I was feeling lazy! What's going to happen...right?

 

[gravenewworld]

The burning sensation could have also just been mostly due to the DCM that spilled on you. It is well known that just DCM alone will cause you to feel like your skin is burning if you spill some on you. Most gloves also don't protect your from being exposed to DCM, so if you spill some DCM on your gloves you have to remove them instantly. You don't really want to spill that much DCM on you since it binds to your hemoglobin permanently and is metabolized into carbon monoxide, but if you spill small amounts on you once in a while you'll live.

Old timers back in the day used to wash their hands with stuff like benzene after they were done in the lab and still lived to tell about it. So yeah, you'll be OK.

 

[JGM_14]

the worst experience i ever had was when i was doing a hydrogen experment and the flask with the diluted HCl /Al metal exploded (fire,not from pressure) releasing 600ml of HCl and i accidently got it on my feet I wasn't wearing shoes, but if i was wearing shoes it probably soaked into my shoes and stayed there

 

[Moonbear]

the worst experience i ever had was when i was doing a hydrogen experment and the flask with the diluted HCl /Al metal exploded (fire,not from pressure) releasing 600ml of HCl and i accidently got it on my feet I wasn't wearing shoes, but if i was wearing shoes it probably soaked into my shoes and stayed there

Why were you not wearing shoes?! Closed-toe shoes are one of the primary rules of lab safety. You should have been thrown out of the lab without! I had to chase one of my students out of the lab and home to change the other day when she appeared with flip flops. I don't know what she was thinking (clearly, she wasn't thinking when she got dressed that day).

 

[JGM_14]

shoes make my feet hurt, and sweat. i don't like shoes.I am talking about the shoes that liquids can soak through the top, tennis shoes. i don't think it would matter if i wore those shoes or no shoes it would get to my skin either way

 

[Cesium]

You should have been thrown out of the lab without!

He makes the own rules in his own lab...whatever the consequences may be.

So do I! For example, as a general rule I try not to eat in my lab, but if I am doing something completely harmless like calibrating a thermometer in boiling water, then I might enjoy some chips.

 

[JGM_14]

i don't let anybody eat anything that is there unless i say otherwise(i do experiments on food sometimes).
shoes optional
i am not liable for anything that you do on your own
no talking when i am trying to concentrate (i have a mild form of ADHD)
i have lost some interest in junk food (i cannot figure out how, or why), so i don't eat in the lab, much

 

[mgb_phys]

Food in the lab! General rule is shoes, lab coat and safety goggles even when just walking through a lab.

Even in air sampling where all the 'chemicals' are absorbed onto tiny filters inside steel tubes and are analysed inside GC-MS machines there is no food allowed. Although the lab is considerably cleaner in terms of chemical residue than the office! Don't have to wear lab coats though , and only goggles when filing LN2.

 

[disregardthat]

Have you seen fight club? He poured caustic soda on his hand right after he kissed it. It seemed to be very painful. Is it true that water makes strong bases on your skin be more painful?

 

[JGM_14]

water dissolves the caustic soda which makes it react faster. it would be like putting soap in an open wound

 

[Remnant]

i have learned on first hand account that .. if HCl spills on you wash it off with a base (soap) but if not done in enough time.. your skill will turn yellow and you may get a few bumps because of it. but nothing to worry about (if handled almost imediately)

 

[jmnew51]

HF is not a strong acid which makes it fairly easy to absorb right through your skin into your tissues. The burns it leaves are deep and dangerous. I've heard that it doesn't stop moving until it hits bone (and forms CaF2). That's a deeeeep burn. Get enough on you and your life is in danger. HF or any fluoride salt sequesters Ca+2 ions in your tissues and can stop your heart!

I heard a story once about a container of HF that someone had disposed of in the curbside trash. Well when the trash collectors came to collect the trash, the bottle of HF accidentally broke open and spilled on the one guy. (Don't how much).

I think it took him 2 mos. to die.

I've breathed (in the past) the vapours of HF excessively from time to time working with stainless steel. And I'm quite amazed I am not f***ed in some way, knowing what I know now about it.

Jim

 

[mrjeffy321]

I have long heard that Hydrofluoric acid is (one of) the most painful acids to be burned with. How much truth is there to this?
Once its gets on you, it can be absorbed into your body and do a lot of damage to your bones and teeth. It’s a weak acid, but not a good idea to play with.

 

[mgb_phys]

I have long heard that Hydrofluoric acid is (one of) the most painful acids to be burned with. How much truth is there to this?

I don't think so - it's quite a weak acid and one of the dangers is that you don't feel much until it gets through to the other side.

Once its gets on you, it can be absorbed into your body and do a lot of damage to your bones and teeth.

Usually it kills you by binding all the calcium ions in your blood that is keeping your heart beating before it can do any damage to your teeth/bones.

 

[jmnew51]

I don't think so - it's quite a weak acid and one of the dangers is that you don't feel much until it gets through to the other side.

I would tend to think anthing that burns through to the other side has got to hurt.

Might not sting as much right away, but in the long run. Hmmmmm

I got that junk under my fingernails one time and it did not stop burning for a long, long time. And no amount of washing seemed to do any good.
Thank God it was not conc. HF.

Jim