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metal carbonyls / toxicity

updated tue 24 oct 00


Jon Singer on mon 23 oct 00

>>Date: Fri, 20 Oct 2000 14:28:11 -0400 (EDT)
>>From: Tom Buck
>>Ron Roy's post (below) jogged my memory of a visit long ago (October 1973)
>>to International Nickel's then new nickel refinery in Ontario....
>> Using some exotic chemistry the plant's process converts metal
>>oxides to "Carbonyls" which are GASES at low temperatures, the kind of low
>>temperatures that Ron mentions below....
>> The metallic Carbonyls are extremely toxic at very low doses (the
>>INCO refinery has extreme safety measures underway at all times; in some
>>sections, workers conduct themselves as if they were working in Outer

To give you some idea of just how toxic these things are, I was once at a
lab at the University of Colorado, in Boulder, where there was one room
in which they worked on the spectroscopy of a few of these compounds.
I think they had perhaps 2 grams of carbonyls in there; they had a large
warning sign on the door, and a very loud alarm. If any of it had gotten
loose, they would have evacuated the entire building.

OSHA, on one of their pages
gives the 8-hour safe-exposure level for inhaled Nickel Carbonyl as .001
parts per million in air. In contrast, even hydrogen cyanide is listed at 10
ppm, ten thousand times higher.

(Carbon monoxide, CO, is what combines with metals to make carbonyls.
CO itself is listed at 50 ppm. So go figure.)

I can't even imagine an industrial facility full of thousands of kilograms
of metal carbonyls. Just frightening. I don't think I would have been
too happy even to visit the plant that Tom mentions, and I certainly
wouldn't have wanted to work there!

I don't think it's too likely that we're making these in our kilns,
fortunately --
they decompose at about 250 celsius. (It's remotely possible, I guess, that
people who fire chrome greens in reduction might be synthesizing tiny
amounts of chromium carbonyl in their exhaust plumes.) Keep your kilns
well ventilated anyway, folks. Better safe than sorry, eh?

Cheers --