I have a mystery I’m hoping someone can help with.
A student of mine got a burn while she was in the studio a couple
weeks ago. We were etching with nitric acid that day, but I’ve
gotten nitric on myself many times, and this was nothing like it.
As she was leaving class, she noticed a burning sensation on the
underside of her forearm, and saw that it was red in a dime-sized
spot. She came back, and for want of a better idea, we applied a
baking soda poultice.
She tells me it continued to “burn” for the next day or so, and
turned brown. She didn’t go to a doctor. The spot is still visible,
slightly brownish-reddish.
She says that the same day, she thought she had scratched her
glasses, but it turned out they were etched! This doesn’t
necessarily have any connection to the burn.
We don’t use hydrofluoric acid or anything unusual in the studio–
ferric chloride, nitric acid, the usual fluxes, pickle, paint
thinner, lacquer thinner, denatured alcohol.
I promised I would try to get to the bottom of this, so if anyone
has any or expertise that may help, I appreciate the
input.
Her glasses being etched is her own fault for not wearing safety
goggles! as to the burn could be anything coming in content with
body lotion or fragrance or soap and chemically reacting. Might
explain the staining.
Without actually seeing the lesion, I’m taking a guess. A tell-tale
sign of a conc. nitric acid burn is the yellowing of the skin as it
denatures the protein (forming picrics I recall, perhaps
incorrectly). By the time you added the base, it was way too late,
the damage had been done. It will be interesting to see her clothes
after they have been laundered (any holes?).
At university we could not enter the lab without a wearing a lab coat
and protective glasses. Students who wore contact lenses were also
not permitted into the lab. As you are no doubt aware, strong acids
and bases must be treated with respect. However, it seems to me that
we all need to occasionally to learn the hard way.
Nitric burns stain the skin yellow, Aqua Regia stains purple. Just
red as in a burn red? Not a stain, red? Sounds like a burn from high
strength hydrogen peroxide or a different acid. I’d be darn careful
about baking soda on an unknown burn. Check the work area for exactly
what was present. Sounds like it will heal fully on its own, but a
peek by a medical professional would be a good idea.
Any acid lab or regular acid user should have Diphoterine for
treating burns. The stuff far outperforms water or baking soda. I
think Gesswein has it, not sure.
Daniel Ballard
Precious Metals West
National Sales Manager
Sounds like a triggered eczema attack. There is a particular kind
that manifest in raised round spots usually dime or quarter sized
and can be brought on by an allergic reaction to something topical
and also by stress. She wouldn’t have to have a previous history with
eczema to have this reaction to a substance.
On the glasses, you’ve got me. Do you mean the lenses or the frames?
If you mean the lenses, did they have any special coatings on that
reacted with the nitric acid? If the frames, then anything goes. All
kinds of metals are used, including ones that are plated and sold as
solid whatever.
Acid and caustic burns are two very different things, acid being the
"better". Acid denatures the skin on contact creating a layer that
is more or less resistant to further penetration. While it may
entirely destroy the skin in that area, the acid is neutralized by
the process and the damage stays localized. The best traditional
primary treatment is dilution with lots of water although
neutralization (as with baking soda) is OK except in the eyes. In
contrast caustics do not immediately denature the skin, are not
neutralized by the skin, continue to penetrate and result in much
more tissue damage-not good!
Your friends’ burn will take days to weeks to heal. If there was
only a small amount of a strong acid she may have little visible
evidence, on the other hand if there was enough acid to destroy the
full epithelium it will be replaced by scar tissue.
Remembering back to chemistry class, the instructor taught us the
danger of nitric acid by putting a piece of chicken in it so we could
see its distruction. Nitric acid, concentrated enough will leave a
brownish mark on the skin. Not something to fool with. Isn’t it one
of the acids they used to have to keep in glass containers only?