Biomedical Engineering Reference
In-Depth Information
6.3.2 Physical Characteristics
The term cyanide refers to the anion CN
−
,orto
its acidic form, hydrocyanic acid (HCN). Though
a cyanogen C
2
N
2
is the oxidized form of cyanide
ions; however, the term cyanogen commonly
refers to a substance that forms cyanide upon
metabolism and produces the biological effects.
Cyanogens may be simple (cyanogen chloride)
or complex (sodium nitroprusside). Materials of
interest as chemical agents are hydrogen cyanide
(hydrocyanic acid, AC) and the simple cyanogen,
cyanogen chloride (CK).
Hydrogen cyanide is a colorless, highly volatile
liquid and represents a non-persistent hazard. The
vapor is less dense than air and has a faint odor of
bitter almonds, although 25-50% of the population
is missing the gene to be able to smell it. It is highly
soluble and stable in water. Cyanogen chloride on
the other hand is an irritating colorless gas that
is more volatile and dense than hydrogen cyanide
(Table 6.8).
Table 6.7
Chemical agents and lethality
Agent
Class
C
t
50
mgminm
−
3
Death
a
CS
Choking agent
(tear gas)
60,000
Cyanogen
Chloride
Blood agent
1000
Hydrogen
Cyanide
Blood agent
2500-5000
Sulfur
mustard
Vessicant
1500
Tabun
Nerve agent
400
VX
Nerve agent
50
a
Information consolidated from text and tables in unclassified military
and civilian sources
C
t
50
the product of concentration [C] of the nerve agent over time [t]
to produce effects (death) in 50% of those exposed to vapor or aerosol.
Relationship between dose time and concentration:
Delivered dose
=
Concentration mg/m
3
×
timemin
10 mg/m
3
×
10 minutes
=
100 mg/m
3
×
1minute
1982. In 1995 the Japanese doomsday cult Aum
Shinrikyo was believed to have placed cyanide
salts and acid in subway restrooms in Tokyo [13].
Cyanide is also the primary agent used in gas
chambers for death sentences in the penal system.
Cyanide poisoning is believed to be a large factor
in smoke inhalation injuries, especial where plas-
tics are burning [14].
Compared to other chemical agents, though
cyanide can cause death within six to eight minutes
it has had limited military usefulness because of
its high Ct
50
and volatility (Table 6.7). However,
despite its limitations of high volatility, low persis-
tence and a high Ct
50
, cyanide remains a potential
threat as an industrial hazard, accidental poison
and a chemical terror agent. The combustion
of any material containing carbon and nitrogen
has the potential to form cyanide; some plas-
tics (particularly acrylonitriles) predictably release
clinically significant amounts when burned. Indus-
trial concerns in the U.S. are the manufacture
of over 300,000 tons of hydrogen cyanide annu-
ally. Cyanides find widespread use in chem-
ical syntheses, electroplating, mineral extraction,
dyeing, printing, photography, and agriculture, and
in the manufacture of paper, textiles, and plastics.
6.3.3 Mechanism of Toxicity
Cyanide affects virtually all body tissues by
binding to metalloenzymes rendering them inac-
tive. In particular the cyanide ion forms a reversible
complex with the respiratory cytochrome oxidase
a3 enzyme system, an enzyme system essen-
tial for oxidative processes within cells. This
results in impairment of cellular oxygen utilization,
Table 6.8
Physical characteristics of cyanogen agents
Property
Hydrogen
cyanide
Cyanogen
chloride
Appearance
colorless
liquid and
gas
irritating
colorless gas
Chemical formula
HCN
CNCl
Molecular weight
27.02
61.48
−
133
C
−
69
C
Melting point
257
C
128
C
Boiling point
Vapor density
a
0.93
2.1
Volatility
b
1,080,000 25
C
6,132,000 20
C
a
Vapor density is compared to air.
b
Volatility is the amount (mg) of agent in 1m
3
.
