Question about Cyanide Gas (for a good cause :-)

[email removed] (jim vassilakos) writes:
> wondering about cyanide gas (I hope the TML-chemists aren't
> jumpy tonight).

Nope.

> Here's what I've gleaned so far.
>
> You take NaCN (Sodium Cyanide), mix it with some HCl (Hydrochloric
> acid), and whammo, lots of HCN (Hydrogen Cyanide gas). I means lots.
> Enough to really ruin everybody's day assuming you're on a
> closed air supply (like a starship). Say one bucket of
> ingredients per 10,000 tons of displacement affected?

The reaction sounds right.  I'm not sure about the toxicity (sp?),
given that a starship has filters, that sounds a bit low.

> will it really be a gas (ain't much  good as a liquid)?

Basically, yes.

> Second, what does NaCN and HCN look like, smell like, etc? Well,

NaCN is a white powder.  Looks like any other white powder in the lab.

> I guess not many people know what HCN smells like... :-) but you

Actually I *have* smelled HCN.  Get a bottle of almond extract, put it
under your nose, and inhale hard.  (you'll have to imagine the
splitting headache I got....)

> get the idea. I need lots of adjectives for the story, and I don't
> mean the sort you'd find reading an encyclopedia. Anybody
> have an ounce of hands-on experience with this sort of
> thing? (Don't say anthing self-incriminating, now :-)

Almonds.  Sorta sweet odor.  Sorta pleasant.  Splitting headache.
(don't know how it gets when the concentrations get fatal.  It blocks
cellular respiration so people just sorta fall down dead, in about 10
seconds.  Face turns blue and they generally thrash around a lot.)

	-Love, Kisses, and a Neutron Bomb
		-Eric the Finn

[email removed] (jim vassilakos) writes:

> Subject: Question about Cyanide Gas (for a good cause :-)
> This time I'm
> wondering about cyanide gas (I hope the TML-chemists aren't
> jumpy tonight).

Not at all.  I'm sorryt that I'm late with the answer.  Several people
answered in last night's digest, and gave you the basics of what you need:
The smell, and the notion that the ship filters are probably going to be
capable of removing it as part of the regular air recirculation system.
I agree with this latter, byt the way, when you consider that a likely
contingency to be provided for is a fire onboard, which could give you all
sorts of nasty stuff considering the likely amount of plastic on board a
ship.

> You take NaCN (Sodium Cyanide), mix it with some HCl (Hydrochloric
> acid), and whammo, lots of HCN (Hydrogen Cyanide gas). I means lots.

So far so good.  I assume that you can do the chemical equations and molecular
weights bit enough to figure out that it will take you 49 grams of NaCN plus
36.4 grams of HCl to give you 27 grams of HCN plus byproducts.  Excess acid
would probably be either desirable or OK.

> Enough to really ruin everybody's day assuming you're on a
> closed air supply (like a starship). Say one bucket of
> ingredients per 10,000 tons of displacement affected?

10,000 displacement tons is 135,000 cubic meters.  With my handy copy of
the Army field manual on potential military chemical agents, I see that
they give two example numbers for lethal concentration: At 200 milligrams
per cubic meter of air, the LCt50 is about 2000 mg-min/m**3.  That is, you'd
have to breathe that atmosphere for 10 minutes before you had a 50% chance
of death.  The book says that the lethal dose (figured in minutes in a
given concentration) varies storngly with the concentration because the gas
is detoxified by the body fairly quickly.  At 150mg/m**3, the LCt50 is
4500 mg-min/m**3, i.e. a 30 minute exposure.  OK.  For a rough approximation
let's say that the 2000mg-min/m**3 is a firm figure, and that we want to
deliver the dose in 10 seconds, because at that concentration it will be
instantly detectable and crews must be trained to don vacc suits (or the
helmets) pretty fast in emergencies.  Not to mention the fact that the air
filters would start cleaning it up pretty quickly.  (In fact, they'd
probably keep it confined to the room that the mixing occurred in...but
we'll pretend not in order to get a number).  OK, 10 seconds is 1/6 minute.
So, you need a concentration of about 12000mg/m**3, or 12g/m**3.  135,000
cubic meters would make the total requirement 1620kg.  Each 27g of product
requires  75.4g of starting material, roughly 3:1.  So, you'd need about
4.8 metric tons in order to produce something approaching an instantly lethal
dose over the entire interior of the ship, not counting filter effects,
length of time needed for air circulation, etc...doesn't sound too likely
to me.

> Basically, I need know two things. First, is the above
> description correct? Will just mixing the two make HCN and
> will it really be a gas (ain't much  good as a liquid)?
> And is it really as potent as I'm pretending (one bucket to
> 10,000 tons seems a little steep, maybe it's just me)?

Much too steep.

> Many many many thanks in advance.
>
> [email removed]

No problem.

Rob Dean

In your letter dated Fri, 16 Oct 92 10:23:01 BST, you wrote:
>
> > Much too steep.
>
> Yeah. It looks that way. I got my original info from a chem-major
> and former player of mine, but I thought the area of effect sounded
> way off. You basically confirmed that.
>
> Thank you very much for the detailed reply. It's exactly what I needed
> to nuke the idea of using HCN in the story (now I have to find something
> even nastier :-)

Well, I'd refigure some numbers to be sure, but it doesn't look very practical.
Depends on how much of the ship you really need to contaminate, and how fast
you think the crew could respond.  For comparison, I looked up the lethal
dose (LCt50) of Sarin, a common nerve gas invented in World War II, and rather
than being 2000-4500 mg-min/m**3 for HCN, it's more like _70_mg-min/m**3.
Almost 30 times more lethal...so instead of a few tons you'd only need
about 9.45 kilograms to deliver a lethal dose in one minute.  Air mixing
and filters, of course, remain a problem.  Now, some biotoxins are _much_
more toxic than Sarin--something like poison arrow frog venom from South
America is 10,000 times more lethal than Sarin, but it is usually delivered
by injection.  I see a note that says that mixing it with scorpion venom
increases its toxicity by a factor of 20...

Given an SF universe, you could probably come up with something almost
arbitrarily lethal, although imposing severe handling precautions would
be in  order!

Rob Dean

(Additional note: HCN is lighter than air at room temperature, so given some
warning, you could engage in defensive measures like dropping to the floor and
cranking the grav-plates up to 2-Gs to encourage it to concentrate at the
ceiling, and it's also very soluble in water, meaning that a wet rag over the
breathing orifices would probably provide _some_ filtering effect.)