Archive/File: people/l/leuchter.fred/HCN
Last-Modified: 1999/11/06

This is from the [Merck Index] Ninth Edition 1976,
page 632, entry 4688 "Hydrogen Cyanide."

 -Hydrocyanic acid;- "Blausaeure" (German). CHN; mol wt 27.03 ... HCN.
Prepd on a large scale by the catalytic oxidation of ammonia-methane
mixtures [refs omitted].  May also be prepd by the catalytic decompn of
formamide.  Conveniently prepd in the laboratory by acidifying NaCN or
K4[Fe(CN)6].  <[Editor's note: this last formula is quite similar to, but
different from Prussian Blue, also a major topic in the Leuchter Report.
Prussian Blue is Ferric Ferrocyanide, or Ferric hexacyanoferrate (II).
The formula is Fe4[Fe(CN)6]3.  The =ferric= salt of ferrocyanide is
insoluble in water.  Other salts, such as the =potassium= salt of
ferrocyanide, are quite soluble in water]> [more refs omitted]

Colorless gas or liquid; characteristic odor; very weakly acid (does
not redden litmus); burns in air with a blue flame; =intensely
poisonous= even when mixed with air.  d(gas) 0.941 (air = 1) <[Editor's note: 
notice, the gas is LIGHTER than air]>; d(liq) 0.687.  mp -13.4.
bp 25.6 <[ latest defense of Leuchter made a big deal out of how the
gas would condense out on the cold walls.  This would clearly happen to
some extent in a cold room.  If the room were filled with people, the
gas would stay warm]>  Miscible with water, alc;  slightly sol in
ether.  LC50 <[lethal concentration that kills 50% of test animals,
NOTICE that this is dependent BOTH on time and on concentration!]> in
rats, mice, dogs: 544 ppm (5 min), 169 ppm (30 min), 300 ppm (3 min),
[ref omitted].

Human toxicity:  High concn produces tachypnea (causing increased
intake of cyanide)  <[tachy = rapid, pnea = breathing]> then dyspnea
<[dys = difficult, pnea = breathing]> paralysis, unconsciousness,
convulsions, and respiratory arrest. Headache, vertigo, nausea, and
vomiting may occur with lesser concentrations. Chronic exposure over
long periods may cause fatigue, weakness.  Exposure to 150 ppm for 1/2
to 1 hr may endanger life.  Death may result from a few min exposure to
300 ppm.  Average fatal dose <[ingested]> 50 to 60 mg.  =Antidote=
Sodium nitrite and sodium thiosulfate.

Use:  The compressed gas is used for exterminating rodents and insects
and for killing insects on trees, etc.  =Must be handled by specially
trained experts.=

  <[end of article]>

     Cyanide is a small molecule.  Basically it is toxic because it
resembles the oxygen molecule, O2 or OO looks like HCN to the binding
sites in the mitochondria and also probably to the heme groups in
hemoglobin and myoglobin.  If Cyanide "sits down" on the cytochrome a/a3
complex at the end of the mitochondrial respiratory chain, then the
oxygen you breathe no longer does you any good.  You can't use it as an
acceptor for high energy electrons, and you can't make ATP by the usual
method of oxidative phosphorylation.  Your body makes you breathe faster
at first, in an attempt to overcome it, and then cells start dying from
lack of oxygen and lack of ATP energy.

     In general, the statements about chemistry in the newest defense of
the Leuchter report seem valid.  The =premises= are of course open to
question or wrong.  Yes, high concentrations of cyanide will cause
formation of prussian blue on cold wet bricks that contain high levels
of iron ions.  But were the bricks really cold and wet?  Was the air
cold enough for the HCN to condense?

    Anyway, I hope this information proves useful.  I teach Biochemistry
at Rutgers University, and that's where my information about cyanide
toxicity comes from.  The Merck Index is a standard reference book that
probably every library has.

Frank Deis (DEIS@PISCES.RUTGERS.EDU)

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