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Hydrogen Cyanide: A Necessary Evil
Introduction
From the battlegrounds of World War II to the gold mines of the Midwest, hydrogen
cyanide is prevalent as an industrial material, pesticide, and a cultural icon representing covert
affairs. Its unique structure and nomenclature indeed imbue it with unique and dangerous
properties as a substance, both catching humanity’s eyes and imagination. Since the late 19th
century, this compound has been a very integral part of industry, culture, chemistry, and many
other processes that drive our minds, grow our food, and fuel our economy.
Composition and Properties
Hydrogen cyanide, known also by its
chemical formula, HCN, is composed of one
hydrogen atom, one nitrogen atom, and one carbon
atom. The hydrogen and carbon atoms are
connected with a single bond; however, the nitrogen
and carbon atoms connect using a triple bond,
causing the atom to be polar, or asymmetrical.
Fig. 1 – A Lewis diagram of Hydrogen
Cyanide, HCN.
Because of this, it boils at about twenty-five degrees
Celsius, causing the substance to become a gas at
room temperature (Ophardt). Generally, hydrogen cyanide is formed during a reaction
between ammonia and carbon monoxide, using the Andrussow process. HCN can also be
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obtained during a reaction between methane (natural gas) and ammonia using a catalyst of
either rhodium or platinum at temperatures of 1,100 degrees Celsius to 1,300 degrees Celsius.
As an acid, HCN is very weak, though very toxic, known in its water form as hydrocyanic
acid. As a liquid, hydrogen cyanide takes on a clear to pale blue color (“Hydrogen cyanide”).
To some, the substance has a faint odor of burnt almonds, though the scent is usually
undetectable due to a common genetic trait in humans (Cordas).
Effects of HCN on the human body
If ingested, large amounts of hydrogen cyanide can cause heart failure, intense seizures
and coma, often leading to severe brain damage and death (DynaMed). The cyanide prevents red
blood cells from intercepting oxygen, usurping the respiration process and causing shortness of
breath, extremely slow or fast heartbeat, and cherry-red skin in small doses. If exposed to the
substance over a long period of time, a
person may develop symptoms gradually,
which can make the poisoning harder to
detect. These gradual doses cause chronic
headaches, nausea, general weakness, and
shortness of breath. When cyanide enters
the eyes, it causes severe irritation and
itching, and can cause blindness after long
Fig. 2 – Cyanide starves red blood cells of oxygen,
causing free oxygen in the blood to tint the skin a
bright red.
periods of ocular exposure. Causes of
poisoning include intentional overdose, accidental ingestion of apricot pits, inhalation of smoke
from a bonfire or burning building materials, inhalation of car exhaust, or exposure to fumes
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from a chemical plant. In some cases, traces of cyanide have been found in imported food, such
as a shipment of Chilean grapes in 1989 that tested positive for traces of cyanide (WebMD).
Industrial applications
Cyanide has, over the course of several decades, been used as a mining additive during
the refining process of gold. After mined ore is smashed, it is mixed together with 300-500 mg/l
of aqueous cyanide. The cyanide, in a small chemical reaction, removes the gold from most nonsulfide ores. Often, this process is very
efficient, removing 70 – 90 percent of
refinable gold (ICMI). HCN is also
commonly used as an agricultural
pesticide in areas where manufactured
pesticides aren’t available. For this
reason, the cores of apples, peaches,
apricots, and lima beans can contain the
Fig. 3 – Large, airtight containers are used to store
pesticidal cyanide. They carry warning labels to
protect against accidental poisoning.
occasional dangerous dose of HCN
(Mann). During World War II, German
cyanide-based pesticides were marketed
under the name Zyklon-B. For its toxic properties, Zyklon-B was later chosen as a murder
weapon in the Auschwitz-Birkneau and Dachau gas chambers (Peters).
Use as a chemical weapon
Because of its toxic qualities, HCN has been used several times throughout history as a
chemical weapon. Since a lethal concentration of HCN is about 5 grams/min/m3, it is favored for
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use in buildings and other enclosed spaces (NTI). During the Nazi regime, death camps such as
Auschwitz-Birkneau and Dachau used HCN (under the name “Zyklon-B”) in delousing of hair
and extermination of Jews (Peters). A member of the “blood agent”
category, HCN is classified as a Schedule 3 compound by the CWC
(Chemical Weapons Convention), its exports limited after an
attempted utilization of it for nefarious purposes by Japanese
terrorists in 1995. By its former name, “prussic acid”, HCN was
used with limited success by the French military, and later utilized
Fig. 4 - Zyklon-B
canisters were a
common find in death
camps such as
Auschwitz-Birkneau and
Dachau.
by Japanese soldiers, who would hurl bottles of aqueous, stabilized
hydrogen cyanide at Allied soldiers during World War II (NTI).
Because of its high volatility and ability to kill in small doses,
HCN will always be considered a threat and controlled substance.
Conclusion
Hydrogen cyanide, though its uses are numerous as they are important, is a very toxic and
dangerous substance. It can cause serious damage to vital organs and cause death, even in
smaller doses. If handled carefully, however, HCN proves a powerful tool for many daily
industrial processes. From pesticides to refining agents, murder weapons to building materials,
hydrogen cyanide has certainly reserved itself an important, albeit notorious, place in human
history.
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Sources Cited
Cordas, Stevan. "Cyanide History." Dr. Stevan Cordas DO MPH. N.p., n.d. Web. 20 Nov. 2010.
<www.drcordas.com/education/weaponsmassd/cyanides.pdf>.
"Cyanide Poisoning ." WebMD. N.p., n.d. Web. 29 Nov. 2010. <http://www.webmd.com/a-to-zguides/drug-overdose>.
“DynaMed” DynaMed . N.p., n.d. Web. 29 Nov. 2010.
<http://dynaweb.ebscohost.com/Detail?id=AN+114710&sid=53545f54-d474-43ca-b6f0fa10296f3203@sessionmgr12>.
"Hydrogen Cyanide." Worldwide Chemical Information, Trading & Advertising. N.p., n.d. Web.
29 Nov. 2010.
<http://www.chemicalland21.com/industrialchem/organic/HYDROGEN%20CYANIDE.
htm>.
ICMI. "Use in Mining." International Cyanide Management Code (ICMI) For The Manufacture,
Transport and Use of Cyanide In The Production of Gold(ICMI). N.p., n.d. Web. 29 Nov.
2010. <http://www.cyanidecode.org/cyanide_use.php>.
Mann, Jay. "Cyanide - a natural pesticide." The Natural Toxins in Our Food. N.p., n.d. Web. 29
Nov. 2010. <http://www.saferfoods.co.nz/cyanide.shtml>.
"NTI: Hydrogen cyanide ." Nuclear Threat Initiative: Home Page. N.p., n.d. Web. 29 Nov. 2010.
<http://www.nti.org/e_research/profiles/NK/Chemical/1091.html>.
Ophardt, Charles. "Molecular Geometry Types: Linear." Elmhurst College: Elmhurst, Illinois.
N.p., n.d. Web. 29 Nov. 2010.
<http://www.elmhurst.edu/~chm/vchembook/202linear.html>.
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Peters, Gerard. “Blausaeure zur Schaedlingsbekaempfung” (Stuttgart: Ferdinand Enke,
1933), p.17.
Photo Sources
Figure 1
Ophardt, Charles. "HCN Diagram." Elmhurst College: Elmhurst, Illinois. N.p., n.d. Web. 29
Nov. 2010. <www.elmhurst.edu/~chm/vchembook/images/202hcn.gif>.
Figure 2
"Oxygen-starved Red Blood Cells." Brasil Health Care Blog. N.p., n.d. Web. 29 Nov. 2010.
<http://www.capitalbrasileiradacultura2007.com/page/2>.
Figure 3
"Zyklon-B Photograph." Flickr. N.p., n.d. Web. 29 Nov. 2010.
<farm3.static.flickr.com/2780/4311612224_5e86702bd3.jpg>.
Figure 4
”Zyklon-B Canister” University of Minnesota Center for Holocaust & Genocide Studies. N.p.,
n.d. Web. 29 Nov. 2010.
<http://www.chgs.umn.edu/museum/responses/kalb/images/holocaustseries8.jpg>.