Re: Aqua Regia & safety

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From: Judy Seigel (jseigel@panix.com)
Date: 02/20/03-10:49:56 PM Z


On Thu, 20 Feb 2003, Philippe Monnoyer wrote:

> My feeling is that Gordon's assumption would free us to feel "obligated"
> to put disclaimers everywhere. This is heavy. In the meantime, refering
> once for all on a unique common source/reference page would be
> constructive. When somebody would post a recipe that he/she thinks
> deserve warning, he/she would point to that page. That page would give
> directions and indications, the best we could make it, without being an
> ultimate reference neither. A comparison: anybody could go in the
> library of the nearest university, in the chemistry bookshelf, and find
> tons of info without disclaimers nor warnings. The list is or should be
> like a bookshelf with organized warnings. That would maybe clear the
> list by removing never-ending sterile argueing. Frankly speaking aqua
> regia is not a big issue. Its danger is more immediate than dichromate,
> but I'd rather avoid that later one.

Philippe, I have worked extensively with dichromate & not with aqua regia,
but my feeling is it's simply impossible to rate the relative danger.
I've read a lot of the 19th century literature about workers in dichromate
who had hellacious agonizing skin lesions, without -- for nearly a
lifetime -- a clue what caused them. I am most EXTREMELY allergic myself
(I could get hives, when I was in full bloom turpentine allergy, from
sitting in a chair that someone with turpentine on her hands had put her
hands on 5 hours earlier, or using floor wax or shoe polish, which have
turpentine, which is, I understand one of the two most allergenic
substances to humans -- the other being chrome.)

Yet, I have managed by keeping hands out of it, and other care, to use
dichromate for 10 years and apparently OK ... Though I've found that even
putting bare hands in final "clear" washwater, as I occasionally did in
"emergency" at school, left me with discomfort in skin for a day. I also
know that an occasional splash on bare legs of just a tiny dot of the gum
soaking water that I didn't notice at the time, causes a burning itch
within an hour or so... It's quickly removed by rinse with clear water --
but it suggests to me all sorts of ramifications of danger.

As for the turpentine -- I shudder to think of the classroom situations
where each of 50 or even 20 students has an open palette with turpentine
evaporating into the room. We had that in art school... I hadn't
developed the allergy at the time, but it surely was a factor. And I'll
add that my own turpentine allergy at one time was so severe I verged on
anaphylactic shock.

In other words, trying to "rate" the danger is not only moot, but not
necessarily useful. It could cause someone to relax where they shouldn't,
and panic where it's also beside the point. It's like trying to say which
is more fattening, peanut butter or steak or Courvoisier. It depends
where, how, how much, and who.

As for that Hazards book, I found it absolutely useless. It has no sense
of proportion, rating all hazards as if you were using industrial strength
amounts for a 40 hour week. So you either discount it entirely, or give up
at the outset.

And to come back to the precipitating issue here, Liam's formula was for
50 ml (less than 2 ounces !) of aqua regia, which was then diluted. That's
about a shot glass full.

And now, Philippe, since you seem a level-headed sort -- what do you
think about working with ether, gun powder and rat poison, as has had NO
warnings on this list, not a single solitary one, although wetplate is
the latest rave, craze, passion.

And, would you compare the danger of splash or fumes from aqua regia with
Dutch mordant (the strongest etch for printmakers) or nitric acid, which
we used all day long in open trays in print making, probably from 2 to 4
litres in a tray, probably 4 or 5 trays in a room. Nobody said a WORD
about danger -- it was assumed that we were adults and knew it was strong
enough to bite metal.

Judy


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