Alkali metal cyanides (mostly potassium cyanide, KCN,
or sodium cyanide, NaCN) have a history dating back to
the 18th century. They are widely used in chemical
synthesis, gold mining, electroplating, and a variety
of other industrial processes. NaCN and KCN are very
similar chemically, although sometimes one form or the
other is preferred. They are very toxic to higher forms
of life and hence may be difficult to purchase without
the backing of a business or educational institute.
Hydrogen cyanide has a characteristic odor that is most
often described as that of "bitter almonds." I
personally think that the scent, although distinctive,
does not resemble any almonds I have ever encountered.
Perhaps I haven't yet found the bitter ones. Although
the scent of hydrogen cyanide is a handy qualitative
test for small amounts, larger quantities or repeated
exposure will temporarily dull the nose's capability to
distinguish it. Additionally, a fair proportion of the
population cannot smell hydrogen cyanide to begin with,
so scent alone cannot be counted on to detect cyanides.
Alkaline cyanides, especially when damp, have a scent
of hydrogen cyanide to them. This is likely due to the
slow reaction of carbon dioxide from the air with the
cyanide. Since hydrocyanic acid is a very weak acid,
the slightly stronger carbonic acid (carbon dioxide
dissolved in water) can produce alkali carbonates from
alkali cyanides, simultaneously releasing hydrogen cyanide.
SHORTCOMINGS OF EXISTING FRINGE LITERATURE
A variety of fringe literature, both printed and
online, has suggested various processes for amateur
production of cyanides. Two commonly suggested methods
are the decomposition of low-toxicity, unregulated
ferrocyanide or ferricyanide compounds by heat
(producing alkali cyanides directly) or by strong acids
(producing hydrogen cyanide, which must then be led
into a solution of metal hydroxide to produce the
cyanide salt). These methods are workable, but they
still require chemicals that cannot be readily found in
consumer products and must be purchased from specialty
dealers or tediously synthesized (often, it is
suggested, by recreating nineteenth century industrial
production techniques in miniature). Another method
that is sometimes suggested is extracting hydrogen
cyanide from cyanogenic glycosides found in plants
(such as apple seeds or peach pits or leaves). This
method would require an unreasonable amount of
dedication to produce relatively small quantities of cyanides.
Methods that are much less commonly speculated about
but still possible include the distillation of ammonium
formate, combustion of alkali carbonate laced carbon in
the presence of ammonia or nitrogen, controlled
reduction of alkali nitrates by carbon, and Hoffman
isonitrile synthesis using ammonia, chloroform, and an
alkali hydroxide. All of these methods have drawbacks
in terms of requiring the purchase or synthesis of
certain chemicals, assembling apparatus, purifying the
final product, or obtaining decent yields of cyanides
in the first place. Therefore, included in part III of
this document is a tested procedure designed for
small-scale synthesis of alkali cyanides by an amateur
with modest resources, which should crown this document
King of the Fringe Cyanide Literature.
A SHORT HISTORY OF CYANIDES
"The familiar coloring matter, prussian blue, was
discovered about 1710, but the chemical substance
cyanogen, the radical common to prussian blue and to a
large series of complex substances now known to
chemistry, was not isolated until more than a hundred
years later. The name cyanogen (generator of blue) was
given by Gay Lussac, in 1814, to the new substance
which he found to be the characteristic ingredient of
this blue and of compounds related to it. The familiar
name of "Prussiates," still applied in trade to the
double cyanides of iron and potassium as well as the
common name 'Prussic Acid,' by which hydrocyanic acid
is known, bear evidence of the importance which the
blue color originating in Prussia had early acquired as
a commercial product.
Some time before the year 1710 a German manufacturer
named Diesbach, working with the so-called Dippel's
animal oil (commonly obtained by destructive
distillation of bones, blood, or other animal waste)
happened, in handling a solution of this oil made from
blood, to add it to a solution of potash (crude
potassium carbonate) and obtained thereby a blue color.
The process was soon applied upon a commercial scale.
It was first described in a book called Miscellanea
Berolinensia, published in 1710. But the discoverer of
the color was not known by name until mentioned by
Scheele in 1731."
To make a long story shorter, it was discovered some
years later that potassium ferrocyanide could be formed
by treating Prussian blue with potassium hydroxide. It
was later found that potassium ferrocyanide could be
formed directly by heating potassium carbonate, iron
scraps, and organic wastes (such as dried blood or
scraps of leather, wool, or horn) together in a furnace
for several hours, dissolving the fused mass in water,
and separating the potassium ferrocyanide by repeated
crystallization. The chemistry involved is not
straightforward and there were many details involved in
the successful commercial application of the process.
See  for a detailed description of the nineteenth
century industrial production of potassium ferrocyanide
("yellow prussiate of potash.")
Much of the nineteenth century's alkali cyanides were
produced by the thermal decomposition of ferrocyanides.
"CYANIDE OF POTASSIUM -- This useful salt is most
advantageously prepared from ferrocyanide of potassium
or yellow prussiate of potassa, which is to be
carefully dessicated, and reduced to a fine powder,
eight parts of which are mixed with three parts of
carbonate of potassa and one of charcoal, both in
impalpable powder. This mixture is to be exposed to a
strong red heat in a closed iron crucible. After
cooling, the mass is to be finely powdered, placed in a
funnel moistened with a little alcohol, and then washed
with cold water. The colorless strong solution of
cyanide of potassium which passes through, is then
rapidly evaporated to dryness in a porcelain basin and
fused at a red heat. This salt, as obtained by ignition
of the above ingredients, without the charcoal, usually
contains a little cyanate, which, however, does not
interfere with its use for forming and dissolving
cyanides of gold and silver for the processes of
voltaic gilding and plating."
Purer materials required more complicated methods. One
such method was passing hydrogen cyanide or hydrocyanic
acid into a solution of potassium hydroxide dissolved
in alcohol. The potassium cyanide was less soluble than
the hydroxide and precipitated.
"The preparation of cyanide of potassium in a state of
perfect purity, is always attended with difficulty,
owing to the action of the carbonic acid of the air
upon its solution, and the tendency of the menstrum
itself to undergo spontaneous decomposition, even when
secluded from the air. It is obtained in a state of
great purity by adding absolute hydrocyanic acid, or a
strong solution of this acid, to an alcoholic solution
of potassa; a portion of the cyanide falls down as a
white crystalline precipitate, which should be washed
with alcohol and dried."
The strong solution of hydrocyanic acid may be prepared
from potassium ferrocyanide.
"The last mode of procedure which it will be requisite
to describe here is that of Trautwein. Fifteen parts of
finely-powdered ferrocyanide of potassium are distilled
at a gentle heat with nine parts of sulphuric acid,
previously diluted with an equal weight of water; the
distillate is collected in a well-cooled receiver,
containing five parts of pure chloride of calcium,
broken into small pieces. When the hydrocyanic acid has
accumulated in sufficient quantity to cover the
chloride of calcium, it is poured off into a
well-stoppered glass bottle."
The "well-cooled receiver" cannot be emphasized too
much. Pure hydrogen cyanide boils at about 25 degrees
Celsius (77 degrees Fahrenheit) and concentrated water
solutions are also volatile. Attempting to prepare
hydrogen cyanide gas or solution without proper
glassware and a fume hood is asking for disaster. If it
is desired to store the hydrocyanic acid thus procured,
it is advisable to keep the bottle cool and away from
sunlight, and to add a few drops of sulfuric or
hydrochloric acid for stabilization. Unstabilized
hydrocyanic acid tends to polymerize with time, forming
a complex mixture of organic compounds.
In recent years, most hydrogen cyanide has been
obtained by the reaction of methane with ammonia or as
a byproduct of acrylonitrile production. These
processes are not at all suited to small-scale
production with simple apparatus.
Once you have obtained alkali cyanides, it is very easy
to produce hydrocyanic acid from them. Almost all acids
are stronger than HCN and will liberate it from its
salts. Acetic acid, citric acid, and certainly the
mineral acids will all set it free. But I would
consider it extremely foolhardy to produce hydrocyanic
acid without proper glassware and a fumehood.
"Poisoning may arise from any substance which releases
the cyanide ion (CN-). Cyanide is a potent and rapidly
acting chemical asphyxiant; it deprives tissues of
necessary oxygen by inhibiting reversibly such
oxidative enzymes as cytochrome oxidase (Stotz et al.,
1938). Because oxygen cannot be utilized, venous blood
retains the bright red color of oxyhemoglobin. Cyanide
does not react to an appreciable extent with the
hemoglobin molecule. As with other chemical
asphyxiants, the critical organs are those which are
most sensitive to oxygen lack, notably the brain. A
transient stage of central nervous stimulation is
followed by central nervous depression and finally
hypoxic convulsions and death due to respiratory arrest
(Ward and Wheatley, 1947). Cardiac irregularities are
commonly observed, but the heart beat invariably
outlasts breathing movements (Wexler et al., 1947).
Few poisons are more rapidly lethal than cyanide. The
inhalation of hydrogen cyanide commonly produces
reactions within a few seconds and death within
minutes. With the ingestion of cyanide salts death may
be delayed as much as an hour. The prognosis is fairly
good if the patient is still alive 1 hour after
swallowing a dose of cyanide, but fatal relapses have
been described after periods as long as 4 hours. If the
stomach is empty and the free gastric acidity is high,
poisoning is especially fast. After large doses some
victims have had time only for a warning cry before
sudden loss of consciousness. Hydrogen cyanide in
aqueous solution (hydrocyanic acid) is readily absorbed
from the skin (Potten, 1950; Tovo, 1955) and from all
mucous membranes (such as the rectum and vagina), but
the alkali salts are usually toxic only when ingested.
The average lethal dose of HCN taken by mouth is
believed to lie between 60 and 90 mg; this corresponds
to about 1 teaspoonful of a 2 per cent solution of
hydrocyanic acid and to about 200 mg of potassium
cyanide (Gettler and St. George, 1934; Gettler and
Baine, 1938). Prompt treatment, however, has saved a
person who swallowed 6000 mg of KCN (Miller and Troops,
1951) and 3 to 5 g have been survived without specific
therapy (Liebowitz and Schwartz, 1948). The lethality
of most derivatives is regarded as proportional to the
content of readily available cyanide. The mortality
rate is high, but in nonfatal cases recovery is
generally complete. Rarely neuropsychiatric sequelae
are observed, as in carbon monoxide poisoning.
[much information about detoxification mechanisms and
clinical treatment omitted]
1. Massive doses may produce, without warning, sudden
loss of consciousness and prompt death from respiratory
arrest. With smaller but still lethal doses, the
illness may be prolonged for 1 or more hours.
2. Upon ingestion a bitter, acrid, burning taste is
sometimes noted, followed by a feeling of constriction
or numbness in the throat. Salivation and nausea are
not unusual, but vomiting rarely occurs except after
concentrated solutions of sodium and potassium cyanide,
which are corrosive because of their high alkalinity.
Other symptoms follow in rapid progression.
3. Anxiety, confusion, vertigo, giddiness, and often a
sensation of stiffness in the lower jaw.
4. Hyperpnea and dyspnea. Respirations become very
rapid and then slow and irregular. Inspiration is
characteristically short while expiration is greatly prolonged.
5. The odor of bitter almonds may be noted on the
breath or vomitus. This characteristic odor is
sometimes a diagnostic help.
6. In the early phases of poisoning, an increase in
vasoconstrictor tone causes a rise in blood pressure
and reflux slowing of the heart rate. Thereafter the
pulse becomes rapid, weak, and sometimes irregular. The
victim notes palpitations and a sensation of
constriction in the chest.
7. Unconsciousness, followed promptly by violent
convulsions, epileptiform or tonic, sometimes local but
usually generalized. Opisthotonos and trismus may
develop. Involuntary micturition and defecation occur.
8. Paralysis follows the convulsive stage. The skin is
covered with sweat. The eyeballs protrude, and the
pupils are dilated and unreactive. The mouth is covered
with foam, which is sometimes blood-stained. The skin
color may be brick-red. Cyanosis is not prominent in
spite of weak and irregular gasping.
9. Death from respiratory arrest. As long as the heart
beat continues, prompt and vigorous treatment offers
some hope of survival.
Treatment (must be prompt):
1. If the patient is apneic, start artificial
respiration immediately. Keep the airway clear.
2. Administer by inhalation amyl nitrite (amyl nitrite
perles) for 15 to 30 seconds of every minute, while a
sodium nitrite solution is being prepared.
3. Discontinue amyl nitrite and immediately inject
intravenously 10 mL of a 3 per cent solution of sodium
nitrite over a period of 2 to 4 minutes. If necessary,
inject a nonsterile solution. Do not remove the needle.
4. Through the same needle infuse intravenously 50 mL
of a 25 per cent aqueous solution of sodium
thiosulfate. The injection should take about 10
minutes. Other concentrations (5 to 50 per cent) are
permissible if the total dose is held at approximately
5. Oxygen therapy may be of value in combination with
amyl nitrite and sodium thiosulfate therapy, perhaps by
speeding detoxification reactions.
6. If symptoms recur, the injections of nitrite and
thiosulfate may be repeated at half the above doses.
7. Because of the speed of absorption and the rapidity
with which symptoms appear, gastric lavage is seldom a
practical procedure and should be postponed at least
until after procedures 1-4. Probably the best lavage
fluid is a dilute solution of potassium permanganate (1:5000).
8. Oxygen therapy and a whole blood transfusion may
become necessary if nitrite-induced methemoglobinemia
become too severe."
A very dedicated but foolish individual might attempt
to produce hydrocyanic acid or hydrogen cyanide by
replication of the nineteenth century's methods:
heating potassium or sodium carbonate with scrap iron
and organic refuse in a small furnace for several
hours, extracting and purifying the ferrocyanide by
repeated crystalization, and treating the ferrocyanide
in one of the ways detailed in part I to yield an
alkali cyanide or hydrocyanic acid. This method
requires a furnace and a lot of time and labor.
There is a modified method that is slightly more
reasonable for amateur production of ferrocyanides. If
potassium or sodium hydroxide is substituted for the
respective carbonate, a propane torch or small charcoal
fire can be substituted for the furnace, since the
hydroxides have much lower melting points. Adding
copious amounts of dried blood to the molten hydroxide
will provide sufficient iron and nitrogen to yield a
bountiful crop of ferrocyanide. The ferrocyanide can
then either be purified by dissolution, filtration, and
recrystalization, or the entire reaction mass (once
cool) can be broken up and added to dilute sulfuric
acid and heated to distill hydrocyanic acid (again, see
part I). There are still problems, though. Molten
alkali hydroxides are hazardous to work with.
Hydrocyanic acid is very hazardous to work with. The
blood meal/hydroxide mixture tends to froth and swell,
so that it must be constantly stirred to break up
bubbles and fresh blood can be added only slowly. The
stench of charring blood will not endear you to
friends, family, or neighbors.
A much nicer method for the production of the cyanides
is the production of alkali cyanate followed by its
reduction to cyanide. This method requires relatively
high temperatures but does not need a furnace. All
required materials and apparatus can be inexpensively
and easily acquired. The writeup that follows produces
sodium cyanide, but one would almost surely have equal
success starting with potassium compounds to produce
potassium cyanide. Parts are estimated by volume in the
following writeup. This is generally a terrible method
for specifying chemical procedures, since powdered
solids can vary considerably in density depending on
particle size. However, for this particular procedure
we are always going to be using a large excess of
certain reactants to force the equilibrium in the
direction we desire. Since we are using large excesses
of materials to begin with, the imprecision introduced
by volume measures should not be a problem, and far
more people own measuring spoons than own laboratory
balances. I arbitrarily pick "tablespoons" as my
standard unit, though any other volume measure,
consistently applied, should work equally well.
In chemical terms, cyanic acid (HOCN) or isocyanic acid
(HNCO) will be reacted with sodium carbonate (Na2CO3)
to form sodium cyanate (NaOCN), carbon dioxide (CO2),
and water (H2O). The water and carbon dioxide escape as
gases because the mixture is heated.
heat 2 HOCN + Na2CO3 ----> 2 NaOCN + CO2 + H2O
The sodium cyanate will then be reduced with carbon at
high temperatures to form sodium cyanide and carbon
monoxide. The carbon monoxide gas of course also escapes.
heat NaOCN + C ----> NaCN + CO
Find two medium-sized steel cans (such as used for
holding soup, canned vegetables, etc.) They should be
sized such that one can be nested inside the other,
________ || || || || || || || || || || ||______||
or thus: ________ || || || || | | | | | | |______|
The smaller interior can will be used as a disposable
crucible for the cyanide production. The larger
exterior can will be inverted and set over the top of
the smaller can to protect the smaller can's contents
from the air during the reduction of the cyanate to cyanide.
Prepare the steel cans for use by heating them hot
enough to burn off the label, glue, and any coating on
the inside of the can. Wash out the inside of the can
once it has cooled, then heat it enough to dry it.
Prepare 3 tablespoons of finely powdered urea or
cyanuric acid. These materials are both often obtained
as small pellets or fragments. They must be reduced to
powder to ensure good contact with the sodium carbonate
so that a high yield of sodium cyanate will be
obtained. Repeated use of an electric coffee grinder
will quickly convert pellets or pieces to powder. A
ceramic mortar and pestle is somewhat more tedious but
can still produce good results. Slowest of all, one can
use the back of a metal spoon and a hard surface (like
a ceramic saucer) to crush the urea or cyanuric acid
into a fine powder.
Prepare 2 tablespoons of finely crushed charcoal
powder. Charcoal briquettes, such as are used for
cooking food, are a terrible source of charcoal powder.
They contain clay and binders that will lead to a less
pure product, plus they are hard to properly pulverize.
Activated charcoal is a source of relatively pure
carbon and can be used instead of briquettes. Powder it
as you did the urea or cyanuric acid (this may require
Prepare a fire for your crucible. This fire must be
capable of heating it to a cherry red glow. If your
fire is not hot enough, the cyanate will not be
converted to cyanide at a reasonable pace. The simplest
source of sufficiently intense heat is a charcoal fire
built using barbecue briquettes. You can pile the
briquettes in an appropriate barbecue, a large coffee
can with airholes punched in the side, or in a small
pit dug in dry ground. After you have prepared the
fire, you can increase its intensity by blowing air on
it (with a fan, hairdryer, etc.) or leave it as-is. You
may want to start the fire before you perform the other
steps since it can take a while for all the charcoal to
ignite and produce good coals.
Fine, dry sodium carbonate can easily be obtained by
heating sodium bicarbonate (which itself is usually
found as a fine powder) to convert it to the carbonate.
heat 2 NaHCO3 ----> Na2CO3 + CO2 + H2O
Place two tablespoons of sodium hydrogen carbonate into
the smaller can. Heat it upon a gas flame, electric
burner, or your charcoal fire. The powder may begin to
churn and even appear to "bubble" as it expels carbon
dioxide and water vapor, if you are able to apply
strong heat. Stir the powder with a long-handled metal
spoon or stiff piece of steel wire to ensure even and
rapid heating of the whole mass. When it ceases to give
off gases, withdraw it from heat (with metal tongs or
while wearing leather gloves) and let it cool a bit.
If you must, you can use sodium carbonate to begin with
instead of sodium hydrogen carbonate. Sodium carbonate
is commonly sold as the hydrate and this water should
be driven out before it is used to make cyanate. Unless
you are sure that the sodium carbonate is already
anhydrous, heat and stir it like you would the sodium
hydrogen carbonate. If the sodium carbonate is not
already a fine powder, powder it as you have the other
materials while it is still warm. The anhydrous
carbonate will absorb moisture from the air, so do not
take too long to complete the operation.
Combine your powdered urea or cyanuric acid with the
still-warm sodium carbonate and thoroughly stir the two
powders together with a spoon or wire. The urea or
cyanuric acid and sodium carbonate should be powdered
as finely as possible and well-mixed to ensure that the
cyanic/isocyanic acids react before boiling off to the
atmosphere and being wasted. Since a large excess of
urea/cyanuric acid is employed in this procedure, most
of the sodium carbonate should be converted to cyanate
even if the powdering/mixing isn't perfect, but you
should still try to prepare the materials as well as
Once the materials are mixed, place the can on the
charcoal fire. Heap coals up around the sides. The can
will begin expelling vapors and haze of unreacted
cyanic/isocyanic acid, water, carbon dioxide, ammonium
cyanate, ammonia, etc. It isn't terribly hazardous but
neither is it a tonic for the lungs; try to keep upwind
from it. If the fire is hot enough, after a few minutes
the contents of the can should be reduced in volume and
Add the powdered charcoal to this melt and stir it in
with your spoon/wire. The charcoal may ignite on the
surface and take a while to be wetted by the molten
cyanate; don't worry. When the charcoal seems to be
well-mixed with the melt, invert your larger can over
the crucible to form a lid (as illustrated before). Now
you will have to wait some time. Depending on the
intensity of your fire, somewhere from 30 minutes to 2
hours should suffice to convert the cyanate to cyanide.
The lower portion of the can should visibly be glowing
after a few minutes. If it isn't, the fire is probably
not hot enough. You can check the progress once in a
while by removing the covering can with tongs or
leather gloves. A burst of flame when the lid is
removed indicates that the reaction is still in
progress; carbon monoxide produced by the reduction of
the cyanate ignites when it is exposed to a fresh
source of oxygen. If there is no burst of flame when
the cover is removed after a period of cooking, the
reduction is complete or almost complete (or your fire
is not hot enough!) and the can may be removed from the
fire immediately or after just a few more minutes.
Do not remove the covering too often. Its job is to
keep carbon dioxide from the fire away from the cyanide
being formed inside the can. Excessive exposure to
carbon dioxide may convert a considerable portion of
the cyanide to carbonate, rendering your hard work useless.
After the reaction appears to be complete, remove the
can from the fire and wait for it to cool enough to be
touched with bare hands. Then remove the covering. You
want to extract the hard mass of leftover charcoal
powder and cyanide from the bottom of the can. You may
be able to smash it free with a hammer or rock. It is
easier to cut and tear the can open with a pair of
pliers and heavy scissors or tin snips. Perform all of
this over a sheet of newspaper to catch the fragments
that fall as you work. The can's metal may be very hard
and brittle from oxidation and exposure to hot cyanide.
When you have finally extracted the black lumpy mass
out of the bottom of the can, smash or crush it enough
that you can fit it all in an empty glass or plastic
jar with a lid. Be sure to wash your hands after you've
finished handling the cyanide-containing mass. You may
also want to decontaminate the pieces of your crucible
before you dispose of them in the regular trash (see
Add enough warm water to completely cover the
cyanide/charcoal mixture now sitting in the jar. If
everything went well and you are one of those people
who is able to smell cyanide, you should be able to
catch a peculiar odor from the jar at this point. If
you smell an odor like rotten eggs, a sulfur impurity
was introduced into your mix at some point and has
produced some sodium sulfide. Put the lid on the jar to
protect the cyanide solution from carbon dioxide in the
air. Periodically swirl or shake the water in the jar
over the next few hours. The longer you wait and the
finer the charcoal was, the better the cyanide will
leach into the water. If the charcoal was not powdered
very finely, much of the cyanide will remain trapped
inside of it. 2-3 hours of standing combined with
periodic swirling/shaking should do, although you may
Take a plastic kitchen or automotive funnel and fold a
paper towel or coffee filter into a cone inside of it.
Sprinkle a little water on the filter so that it sticks
to the inside of the funnel. This will be used to
filter the unreacted charcoal powder out of your sodium
cyanide solution. The finer charcoal particles will not
be trapped by paper towels or coffee filters. If you
want to remove all traces of charcoal, place a layer of
diatomaceous earth about as thick as your thumb in the
filter; this will catch even the finest bits. Place the
funnel/filter in the mouth of a second glass or plastic
jar, then slowly pour the water/cyanide/charcoal
mixture into it. You want all the liquid to pass
through the filter, not to overflow the funnel or to
slip down the sides past the filtration materials. It
may take several minutes for the liquid to pass through
depending on how badly the charcoal clogs the filter.
When all of the liquid has been filtered, pour the
clear sodium cyanide solution into a shallow glass
baking dish. Set it on a hotplate or electric stove
burner and evaporate it at low heat. Too much heat may
hydrolyze the solution, forming sodium formate and
ammonia. Too little heat will give the solution too
much time to be exposed to the air, which contains
carbon dioxide and will slowly convert it back to
sodium carbonate while liberating hydrogen cyanide. If
the hot solution smells mildly of ammonia, don't worry.
If it smells strongly of ammonia, the conversion of
cyanate to cyanide probably wasn't complete. It needed
more time or more heat in the fire.
When the sodium cyanide is nearing dryness it will form
a sort of damp slush that can be scraped up with the
edge of a credit card or similar implement. Do so,
otherwise it may be hard to remove from the pan when
completely dry. Periodically stir and crush the slush
as it dries until it appears to be mostly or completely
free of water. You now have solid sodium cyanide of an
unknown degree of purity. Store it in a sealed glass or
plastic bottle, sealed away from the air.
There are probably hundreds of qualitative and
quantitative tests for cyanides. One of the oldest,
simplest, and best qualitative tests is the Prussian
blue test. This test combines the unknown with a
mixture of iron (II) and iron (III) salts in acidic
media. The formation of a blue solution or precipitate
indicates the presence of cyanide. Consult an older
book of analytical chemistry if you are interested in
quantitative determination of cyanide by
First prepare a solution of iron (II) sulfate. This can
be conveniently accomplished by adding an excess of
fine steel wool to dilute sulfuric acid or copper
sulfate solution. The reaction with copper sulfate
completes faster and it is usually easier to obtain
copper sulfate than sulfuric acid.
Dissolve a tablespoon of copper sulfate crystals in a
cup of hot water inside a glass or plastic jar.
Shake/swirl the jar until the crystals dissolve. Add
fine steel wool to the solution. It may take a while
for the reaction to start, since steel wool is often
lightly coated with oil to retard rusting. Prodding and
swirling the wool with a glass, plastic, or wooden rod
may help to start the reaction. The wool will turn
copper-red as iron (II) sulfate is formed in the
solution and metallic copper deposits in place of the
iron in the steel wool. When fresh steel wool added to
the jar no longer obtains a copper coating, the
reaction is complete. You can use dilute sulfuric acid
in place of copper sulfate solution. The reaction is
complete when steel wool added to the liquid no longer
forms bubbles of hydrogen. Heating the liquid will
cause the reaction to complete faster, but be careful
to keep the hydrogen-producing reaction away from
Filter the pale dirty-green liquid through a paper
towel or coffee filter and store the clarified fluid in
an airtight jar. Iron (II) sulfate is easily oxidized
to iron (III) sulfate by atmospheric oxygen, which is
why it can be used in the Prussian blue test and why it
needs to be protected from air when not in use. As the
liquid oxidizes it will form an orange scum and the
liquid will darken. Eventually it may become too dirty
to use and will need to be replaced by a fresh batch.
To perform the test, place a small amount of your iron
(II) sulfate solution in a small jar. Add a few drops
of sulfuric or hydrochloric acid (you may try a small
amount of vinegar if you cannot get sulfuric or
hydrochloric acid). Add a few drops or small pieces of
the liquid or solid that you wish to test for cyanide.
Do not use a large sample; dangerous amounts of
hydrogen cyanide could be released. There may not be an
immediate reaction even if cyanide is present. Swirl
and shake the jar to expose the liquid to the air. If
cyanide is present, the liquid should take on a
beautiful blue tinge after a while and may even
precipitate deep-blue material. This is the Prussian
blue, the dye that started the ball rolling with
artificial cyanides in 1704. As some of the iron (II)
sulfate is oxidized by air to the iron (III) state, the
acidified mixture of iron (II) and (III) ions interacts
with cyanide to form this characteristic coloration. If
the test for cyanide is positive, you may wish to
dispose of the test liquid as described in section V.
It is not a good idea to just flush cyanides down the
sink or toilet, or to throw them in the trash. They
should first be converted to non-poisonous compounds.
Sodium hypochlorite solution (household chlorine
bleach) does an admirable job. The hypochlorite
oxidizes cyanide to harmless cyanate, which can then be
disposed of like other household waste.
Hydrocyanic acid solutions should be converted to
cyanide salts before they are oxidized, so that the
heat of oxidation does not cause free hydrogen cyanide
to volatilize. Add the hydrocyanic acid to an excess of
sodium or potassium hydroxide solution before oxidizing
it. The solid or dissolved cyanide should be poured
into an excess of household bleach. The reaction may be
fairly vigorous and generate considerable heat. The
liquid that remains is no more dangerous than ordinary
bleach. You may decontaminate jars, funnels, and
leftover filtered materials the same way. If the
charcoal used for the cyanate reduction had large
coarse pieces in it, they may retain cyanide on the
interior even after being treated with bleach.
Most of the materials that I have referenced can be
obtained in ordinary retail establishments, at least in
the United States.
ACETIC ACID: Ordinary distilled white vinegar is a
dilute solution of acetic acid. More concentrated
acetic acid is used to make up "stop bath" in
photography; photo suppliers should carry or be able to
ACTIVATED CHARCOAL: Often used to filter water in fish
tanks. It can be purchased from pet stores.
CITRIC ACID: This acid is found in citrus fruits and
juices (like lemon juice). It can also be purchased in
pure form from some health food stores, grocery stores,
COPPER SULFATE: Often sold as "root killer," sometimes
as a fungicide. Found in hardware or agricultural
stores. Also found in some pharmacies.
CYANURIC ACID: Used to protect swimming pool chlorine
from photodegradation. Look for "pool chlorine
stabilizer" in hardware and pool/spa supply stores.
DIATOMACEOUS EARTH: Sometimes used in gardening, also
used to filter swimming pool water. Look at hardware
stores, pool/spa suppliers, and gardening centers.
DRIED BLOOD: "Blood meal" is dried blood collected from
slaughterhouse animals. It is often sold in gardening
centers as an organic fertilizer.
HYDROCHLORIC ACID: Also called "muriatic acid" or
sometimes "spirits of salt." It is often found in pool,
hardware, and paint stores. It is used to clean
brickwork and adjust swimming pool acidity among other things.
POTASSIUM CARBONATE: Can be purchased from
ceramics/pottery suppliers. Also can be obtained by
heating potassium hydrogen tartrate until it is
completely charred, then crushing the mass of charcoal,
extracting with water, and filtering to produce
potassium carbonate solution and dried to obtain the solid.
POTASSIUM FERRICYANIDE: This material is sometimes used
in photography and for making blueprints. A few online
photo supply outfits sell it. I *believe* that it
behaves very similarly to potassium ferrocyanide, but I
have not personally investigated its properties.
POTASSIUM FERROCYANIDE: This has little use outside of
the laboratory. However, it is fairly harmless and can
be purchased without difficulty from chemical suppliers
who deal with individuals.
POTASSIUM HYDROGEN TARTRATE: Sold in grocery stores as
"cream of tartar."
POTASSIUM HYDROXIDE: Used in soapmaking; sometimes
found in craft stores or can be ordered online from
outlets specializing in soap/candle manufacturers. Also
sometimes found in hardware stores.
SODIUM CARBONATE: Sold as "washing soda" in some
grocery stores (look near the cleaning products). Also
can be purchased from ceramics/pottery suppliers.
SODIUM HYDROGEN CARBONATE: Also called baking soda,
sold in grocery stores.
SODIUM HYDROXIDE: Sold as "lye," used for opening
drains and making soap. Often found in hardware stores
and in grocery stores among the cleaning products.
STEEL WOOL: Fine fibers of steel used for polishing and
cleaning. Found in hardware and paint stores.
SULFURIC ACID: Sometimes found in dilute form for
adjusting swimming pool acidity. Also found in more
concentrated (but still dilute) form as replacement
electrolyte for lead/acid storage batteries. Found in
concentrated form in professional drain opener liquids
from hardware/plumbing stores.
UREA: Found at agricultural suppliers as fertilizer. It
is easy to find a 50 pound sack at a dedicated
farm-oriented outfit but harder to find in small
quantities or in ordinary urban/suburban gardening
centers. Some instant chemical cold packs (such as you
might use on a sprained ankle) contain urea. Consult
the package and/or manufacturer website to find out if
a particular brand uses urea or ammonium nitrate. When
you find one that uses urea, you can cut the cover open
to retrieve the urea pellets without bursting the water pouch.
 SHOWING THE PROGRESS AND DEVELOPMENT OF PROCESSES
FOR THE MANUFACTURE OF CYANOGEN AND ITS DERIVATIVES. J.
Am. Chem. Soc.; 1889; 11(1); 3-27.
 Muspratt, James Sheridan. Chemistry: Theoretical,
Practical, and Analytical as Applied and Relating to
the Arts and Manufactures - Volume 2. London, 1860.
 Gleason MN, Gosselin RE, Hodge HC, Smith RP .
Clinical Toxicology of Commercial Products. 3rd ed.
Baltimore, MD: Williams & Wilkins Company.