PowerLabs Fulminate Explosives
Synthesis

INTRODUCTION:

Mercury fulminate is an unstable primary
explosive compound. Mercury fulminate was discovered in 1799 by the British
chemist Howard. It was introduced by the British gentleman Wright in 1821 as an
effective filler for percussion caps. Alfred Nobel got its patent in 1867 for
blasting caps, and was the single most used compound for that application until
very recently. It is not used today for that purpose because of more stable
explosives from modern chemistry taking its place, but its high power, ease of
manufacture, and relative stability (as compared with some other improvised
primer choices) makes it an attractive choice for improvised blasting caps even
nowadays. Below, FOR INFORMATIONAL PURPOSES ONLY, the manufacture of a small
batch is outlined. The entire synthesis takes about 2 hours. Do not try to scale
up the procedure, as thermal runaway or excessive crystal stress may result in a
detonation.
Once again I discourage anyone to attempt these
procedures, and if you choose to do so you are doing it at your own
risk.

MATERIALS:

Reactants:

Materials:

1,1g Mercury metal
(Hg(l)) (d. 13.543g/cc)

50mL glass beaker and
100mL flat bottom glass  balloon.

10mL 68% Concentrated
Nitric Acid (HNO3(aq)) (d. 1.41g/cc)

Pipette

15mL 99.8% absolute
ethanol ((C2H6O)(l))

Stirring
Rod

Distilled Water, Ethanol
(l)

The reaction goes as
follows: 1st step involves the nitration of mercury metal with excess nitric
acid:
Hg + 3 OHNO2 => HgNO3 + OHNO2 +
NO2
Secondly, the mercury nitrate and excess acid are
added to ethanol, forming the fulminate:
HgNO3 + HNO3 + C2H6O
=>
Hg(ONC)2

Here all the materials and
reactants used for the synthesis of mercury fulminate can be seen: From the back
row to the front, from left to right:

100gram bottle of Mercury
metal, 100mL bottle of 65% Conc. HNO3, 1L of Distilled Water, 1L
absolute ethanol.
Glassware is one 50mL glass beaker, one 100mL flat
bottom glass balloon, both Pyrex. On the glass beaker is the stirring rod. The
Pipette is between the two large plastic bottles. To the extreme right a 400mL
beaker with filter paper is seen: This will be used to carry out the
filtrations.

PROCEDURES:

For
this procedure 10mL of 65% analytical grade nitric acid were measured out and
pipetted into a 50mL beaker, onto which 1.1g of mercury were pipetted and added.
A vigorous reaction ensued, during which large amounts of Nitrogen Dioxide
(NO2) gas were released and some heat is produced. The reddish/Brown
gas is highly toxic as well as being a very powerful oxidizer, and all contact
should be avoided. This step should be conducted under a fume hood. If the
reaction between the acid and the mercury does not start immediately, the
solution should be heated gently (to no more than 70C).

Once the reaction was complete a greenish liquid
(mercury nitrate solution) formed in the bottom of the beaker. This was left to
stand for a few minutes until it has returned to room temperature and most of
the nitrogen dioxide gas had escaped.

15mL of absolute ethanol were than pipetted onto the 100mL flat bottom glass
balloon, and it was warmed gently. The now cold mercury nitrate / nitric acid
solution was added to the warm ethanol, and within a few minutes a vigorous
reaction ensued, and the external heating was stopped (the reaction produces a
great deal of heat and is self sustaining).

This second reaction lasts approximately 10 minutes, during which time
the solution bubbled vigorously and produced dense white fumes (both poisonous
and flammable. Again this step should be performed in a fume hood). As the
reaction neared completion, the amount of gas and bubbles produced decreased and
crystals were seen precipitating at the bottom.

Once the reaction was complete a small layer of crystals had formed at the
bottom. These were the explosive fulminate, which now had to have all traces of
acid removed from it in order to become stable.

The crystals were removed from the solution by filtering, and while at the
filter they were washed with an extra 15mL ethanol, 50ml distilled water and
than finally 15mL ethanol. This ensured that all traces of acid were removed,
and also reduced the drying time (since ethanol is more volatile than the
distilled water).

Once dried, the crystals formed a grayish/yellow mass that was both poisonous
and sensitive to static electricity, friction and impact. The uttermost care
should be taken to ensure that these are not bumped, scraped or handled
roughly.
Despite the use of analytical grade reactants throughout the
procedure, the crystals still contained some small amount of impurities,
evidenced by their tint.
This is acceptable for commercial
applications, but where one needs the highest energy density possible, combined
with the minimum sensitivity, it would be wise to purify the
crystals.

PURIFYING THE
PRODUCT:

Purification can be done by the
following procedure:

The materials needed are high concentration ammonium hydroxide solution
(NH4OH) (24% conc. was used here)  and glacial acetic
acid (C2H4O2) (dilute also works). The two
chemicals can be seen next to a 50mL beaker containing the crude mercury
fulminate from the previous procedure.

First the mercury fulminate is dissolved in 10 times its volume of
ammonium hydroxide (in this case 10mL were used). It forms into a gray solution,
with a small amount of precipitate at the bottom. Care should be taken during
this procedure to avoid the ammonia gas emanating from the solution.

Once the mercury fulminate had been fully dissolved in ammonium hydroxide
solution, the solution was filtered and the filtrate, containing a small amount
of metallic mercury and dark impurities (which proved to be almost as explosive
as the primary explosive itself) was discarded, whilst the filtered solution was
kept.

To the filtered mercury fulminate/ammonium
hydroxide solution glacial acetic acid was added drop wise until the pure
mercury fulminate crystals started to precipitate out of the solution
(approximately 6ml were needed for this). Than more acid was added and the PH
was checked until the solution tested neutral. To this solution, an extra 20mL
of distilled water were added, and the solution was finally filtered, and washed
with an extra 10mL ethanol for quicker drying times.

Here we see the final, purified product. It consists in a regular mass of
perfect orthorhombic crystals, and is perfectly white due to lack of impurities.
Yield here is estimated at about 2.5 grams (one cc), enough for a #8 blasting
cap. The purified product offers several advantages over the impure version: for
one, its smaller, uniform crystals pack to a much higher density, providing both
more energy and detonation velocity, as well as minimizing crystalline lattice
stress, which is a major source of explosive instability. The higher purity
should also minimize potential incompatibility and long term stability problems.
This explosive is most often used mixed with 10% potassium chlorate by weight,
which gives it a better oxygen balance and thus power.

RESULTS:

Properties:

Decomposes (explodes) at 150 °C.
Molecular mass: 284,62g/mol.
Vdet = 4000m/s at
nominal density
(2,5g/cc).
=
5000m/s at max density (4,0g/cc).
Very sensitive to shock, friction,
and static discharge.

Silver
Fulminate Video

The explosive is very sensitive to shock, friction and heat,
exploding violently when ground hard between two solid surfaces or when struck
by a solid blow between two hard surfaces. Upon burning, very small amounts
produce a bright white flash of light and a subsonic air displacement. Burning
more than a few hundred milligrams results in DDT (Deflagration into Detonation
Transition) and causes a hypersonic shockwave. Everything around the explosive
is stained by atomized metallic mercury, and a toxic cloud of the vapor is seen
around the detonation site, which should be avoided at all costs.
Its
long term stability is fair, the explosive is practically non-hygroscopic and
can be safely stored for up to a year so long as it is not allowed to remain in
a warm environment or contact materials such as aluminum, magnesium, zinc,
copper, brass, or bronze, with which it causes corrosion by formation of
amalgams (a more serious problem with unpurified fulminate which contains traces
of lead). Long term storage in warm environments renders the explosive useless.
For safety of storage the explosive crystals should always be kept under
distilled water.

Synthesis adapted by POWERLABS.

Questions? Comments? Suggestions? E-mail me!

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Last updated 30/01/04

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