"Mark Lipton" > wrote in message
...
> James Silverton wrote:
>
>
> > Hydrogen sulfide is actually more poisonous than hydrogen cyanide,
I
> > believe. However, H2S poisoning can be reversed by artificial
> > repiration if applied quickly enough unlike cyanide.
>
> My, what a bunch of chem-geeks we are! ;-) You're correct about the
> toxicity of H2S vs. HCN, but HCN is slightly more toxic (LC50 in
rats is
> 169 ppm for 30 minutes for HCN, whereas is 713 ppm for 1 hr for
H2S).
> The big difference is that the smell of hydrogen sulfide is
intolerable
> at levels well below lethal (whereas some people can't smell
hydrogen
> cyanide at its lethal concentration). Typically, the only way
someone
> can be poisoned by H2S is when its concentration is gradually
increased
> over a long period of time so that the person's sense of smell is
> desensitized by long exposure to H2S. Was your coworker simply
ignoring
> the smell, or was it a sudden exposure that overwhelmed him?

Yes, it was a sudden exposure and he was doing something that he
should not have tried. The incident actually had some effect on the
introduction of semi-micro methods and safer methods of generating
hydrogen sulfide.

Jim.