From: Katharine Thayer (kthayer@pacifier.com)
Date: 02/21/03-03:30:03 PM Z
It seems that two separate issues may have got crossed in this
discussion. I'm told on good authority that Liam wasn't advocating
adding water to fresh acid but diluting spent acid with water, which is
a different issue. I'm glad to be corrected on the point and to find
that there is less disagreement on the issue than I thought and that no
one is likely to be encouraging folks to pour water into concentrated
acids. I still think the guidelines for aqua regia should be written by
persons other than the principals in the debate.
Katharine Thayer
Katharine Thayer wrote:
>
>
> The person who claims that he's added water to acid without any ill
> effect, leading at least one reader apparently to conclude that the acid
> to water rule has been discredited by his observation, is not a person I
> want writing chemical guidelines for new alt-photo workers. Saying that
> you've added water to acid and nothing bad happened, therefore adding
> water to acid is not a problem, is like saying that because you played
> Russian roulette once and didn't get the bullet, then Russian roulette
> is a fine game and everyone should play it. There is a very good reason
> why every beginning chemistry lab student has to memorize "acid to
> water, the way we oughter" and I for one, as a list participant with
> some chemistry background, would want that time-honored and tested rule
> of chemistry to be respected in any guidelines that we as a list provide
> for beginning alt-photo workers.
>
> Rather than asking the two extreme positions on this issue to try to
> find common ground, I think it may be better to have someone less
> involved with the debate but knowledgeable about chemistry, draft a
> simple guideline for aqua regia. Someone in this thread proposed a short
> sensible list starting with "Use a hood...." which I can't locate in
> the archives now but seems to me like a good place to start.
>
>
> My 2cents.
> Katharine Thayer
>
> Monnoyer Philippe wrote:
> >
> > Judy,
> >
> > It's a bit hard for me to make the link between my post and your short reply. I think you interprated it beyond what I meant.
> > Indeed, it would be ridiculous to consider chemicals do present the same risk with a rated scale.
> > As for fattening agent though, all other conditions being equal, peanut butter will obviously win the race.
> >
> > This was my absolute last mail on that topic.
> >
> > Philippe
> >
> > |
> > |
> > |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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