Chemical burn

**JGM_14** · Aug2-07, 10:24 AM

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** · Aug2-07, 10:29 AM

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** · Aug2-07, 10:42 AM

that makes sense

**chemisttree** · Aug2-07, 10:54 AM

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** · Aug2-07, 12:06 PM

thanks for the info

**Gokul43201** · Aug2-07, 02:46 PM

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** · Aug2-07, 03:34 PM

Originally Posted by 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?

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** · Aug2-07, 05:51 PM

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** · Aug2-07, 08:02 PM

Originally Posted by chemisttree

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** · Aug2-07, 09:10 PM

Originally Posted by chemisttree

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.

Originally Posted by mgb_phys

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.

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

**mgb_phys** · Aug2-07, 09:18 PM

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

**JGM_14** · Aug3-07, 09:23 AM

He spilled it on his lap!? Sounds painful.

**chemisttree** · Aug3-07, 11:45 AM

Originally Posted by mgb_phys

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** · Aug3-07, 11:48 AM

Originally Posted by Gokul43201

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** · Aug3-07, 02:51 PM

Originally Posted by Gokul43201

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** · Aug3-07, 05:03 PM

Originally Posted by Moonbear

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 gonna happen...right?