Igniting mercury(II) thiocyanate causes it to decompose into an insoluble brown mass, primarily composed of carbon, along with mercury(II) sulfide,
carbon disulfide, and gaseous products including toxic cyanogen and nitrogen.
(2)Hg(SCN)2 → (2)HgS + CS2 + (3)C + (2)N2
The flammable carbon disulfide immediately burns int the presence of air to carbon dioxide and sulfur dioxide.
CS2 + (3)O2 → CO2 + (2)SO2
It should be noted that the carbonaceous mass also contains a significant molecular ratio of nitrogen within the molecular structure. Polymerised
plastic sulfur also seems to be an important constituent giving the worm-like form.
Mercury(II) sulfide reacts with oxygen to form mercury vapor and sulfur dioxide. If the reaction is performed inside a container, a gray mercury film
coating can be observed coating the interior surface.
HgS + O2 → Hg + SO2
[Edited on 25-8-2011 by AndersHoveland]Bot0nist - 25-8-2011 at 14:31
Cool. Thanks Anders. I remember reading that the old 'snakes' fire works contained cyanide compounds. Pharaoh's Serpent I believe.The WiZard is In - 25-8-2011 at 15:43
An Estimate of the Risk from a Firework Containing Mercury (II) Thiocyanate
YOSHIAKI IKARASHI, SHIGEO KOJIMA and MASA
AKI KANIWA
Eisei Kagaku 32 (5) 397-401 (1986)
National Institute of Hygienic Sciences, 1
1, Kamiyoga, Setagayaku, Tokyo 158, Japan
An indoor firework, so called "Cager Ningyo". has been imported from Mker in
the interior, and evidently consists of paracynnogen and mercuric sulfide, the
mercury having been burned and vaporized from the outer layer.
To estimate the risk from this firework, Hg gas, SO2 gas and CN gas evolved
from the accessary [sic] were determined by the modified "Standard Method of
Analysis for Hygienic Chemists Authorized by the Pharmaceutical Society of
Japan". As the results, maximum 157.0 ug of Hg gas could be detected in the
decomposition gas from 10 mg of the accessary. [sic] Therefore, if this firework
might be used to play in a room of 22.4 m3 (6 Jyou), Hg concentration in the
room air could reach at the level of 0.070 mg/m3, which might exceed the
allowable level in the work place (0.05 mg/m3). Maximum values of SO2 gas and
CN gas detected were 2.26 ug and 75 ug, respectively, and predictive levels in
the room might be much less than their allowable levels.
We considered it undesirable to use this type of firework by the following
reasons; i) from the above estimate, we might be exposed to the high level of Hg
vapor, ii) this firework itself or its residuum containing large amount of Hg might
be discarded carelessly into the environment, and iii) it is dangerous to put such
poisonous substances as Hg compounds near infants.
PYROTECHNIC SNAKES
TENNEY L. DAVIS
Massachusetts Institute of Technology, Cambridge, Massachusetts
Journal of Chemical Education Volume 17, 1940 Page 268-70
THE sale of the mercuric thiocyanate Pharaoh's Serpents, [1] with which many of us
amused ourselves as children, is now forbidden by law in several of the states, for the
vapors from these toys are poisonous, and, more serious, children have been known to
eat them with fatal consequences. Many of the youngsters nowadays will have to wait
until their high-school or freshman chemistry course before they can see a
demonstration of the extraordinary property of the mercury salt. They can, however,
purchase non-mercury Black Snakes, made entirely from organic materials, the
composition of which is as much of a mystery to the generality of chemists as it is to the
children who play with them.
Wöhler, [2] while still a medical student at Heidelberg in 1821, first reported the
remarkable property of mercurous thiocyanate—which he prepared by precipitating
mercurous nitrate with potassium thiocyanate—that it swells up when it is heated
"winding out from itself at the same time worm-like processes, to many times its former
bulk, of a very light material of the color of graphite, with the evolution of carbon
disulfide, nitrogen, and mercury. On further heating the same material remains along
with mercuric sulfide. The swollen mass obtained by gentle heating, when ignited with
copper oxide, gives a gas consisting of carbon dioxide and nitrogen in the proportion in
which they would be formed by the combustion of cyanogen"—and hence consists of
paracyanogen.
Mercuric thiocyanate gives better snakes than the mercurous compound. When a heap
or pellet of either of these substances is set on fire, it burns with an inconspicuous blue
flame, producing sulfur dioxide and mercury vapor. The resulting pale brown or pale
gray snake, if broken, is found to be much darker in the interior, and evidently consists
of paracyanogen and mercuric sulfide, the mercury having been burned and vaporized
from the outer layer.
Mercuric thiocyanate was first prepared by Berzelius [3] in 1821 by the action of
thiocyanic acid on mercuric oxide. Claus [4] reported that mercurous thiocyanate is
precipitated only in dilute solutions, that concentrated solutions of potassium
thiocyanate and mercurous nitrate give a black precipitate which consists of metallic
mercury mixed with mercuric thiocyanate. Otto Hermes' appears to have been the first
to report the preparation of pure mercuric thiocyanate by precipitation, although he
suggests in his paper of 1866 that it was already in use in commercial Pharaoschangen
which, he says were made up with two per cent. of potassium chlorate. He stated that
mercuric thiocyanate explodes powerfully when rubbed with an equal weight of
potassium chlorate, The pure substance decomposes at 16o, but when mixed with one
per cent. of potassium chlorate it decomposes at 90o. Philipp [6]in the following year
reported further observations on mercuric thiocyanate: that it turns yellow when heated
to 110', that it is decomposed by light to form a gray material insoluble in hydrochloric
acid an(I a dark colored material insoluble in potassium thiccyanate solution, that it is
slightly soluble in hot water and comes out again on cooling in the form of thin pearly
leaflets or small prisms which have all of the properties of the precipitated material, and
that it is soluble in cold hydrochloric acid and in potassium thiocyanate, potassium
chloride, ammonium chloride, and mercuric nitrate solutions.
Since mercuric thiocyanate is soluble in an excess of the reagents from which it is
prepared, it is best procured by adding a potassium or sodium thiocyanate solution
slowly and with stirring to a solution of mercuric nitrate to which a small amount of ferric
chloride solution has been added. The appearance of the red color of ferric thiocyanate,
if it is not dispelled by stirring, indicates that enough of the thiocyanate solution has
been added. The white precipitate is collected, washed, dried, and powdered. The
powder is moistened sparingly with a weak aqueous solution of gum arabic, "to which
may be added a pinch of saltpeter," [7] and is made into small cylindrical or conical
pellets which are known as Pharaoh's Serpents' Eggs. If too much of the gum arabic
water is used, the material assumes the consistency of heavy clay and is difficult to
handle. On a plant scale, little truncated cones of the material are made by pressing the
composition into holes, larger at one end than at the other ' bored through a sheet of
metal or a slab of hard wood, and then pressing the pellets out by means of a second
board or sheet of metal studded with pegs which match the smaller end of the holes in
the first piece. In the laboratory, pellets are made conveniently by means of two pieces
of glass tubing, fire-polished at the ends; the wider piece about ten cm. long is supplied
with a fitting made from a cork stopper, which plug is to be moistened in order to move
more freely when the instrument is in use, while the second tube about twelve cm. long
fits within the other and is used as a plunger for pushing the cork plug. The composition
is pushed into the tube against the cork plug; then, while the end of the tube is held
against a flat surface, it is compressed to a compact pellet which is finally jected by
pushing the plunger.
"Snakes in the Grass," "Volcano Snakes," and so forth, depend upon the use of
ammonium dichromate. if this material in the form of powder is made into a conical
heap, and a flame applied to the top of it, a visible but not violent "combustion"
proceeds through the mass which "boils up" to form a large volume of green material
(Cr2O3) resembling tea leaves. In practice, more flame is desired than ammonium di-
chromate alone will give. Weingart [8] recommends a mixture of two parts of ammonium
dichromate with one of potassium nitrate and one of dextrine. Tin foil cones are made
from circles of tin foil shaped on a former, and are introduced by means of the former
into conical cavities in a block of wood; they are then about half filled with the powdered
mixture, a Pharaoh's Serpent's Egg is pressed in, and the edges of the tin foil are
turned down upon it to form the base of the cone. A shallow wooden box filled with the
ammonium dichromate mixture in which five or six Serpent's Eggs are buried makes an
amusing toy, and may be fired by means of a piece of blackmatch. [9]
Black non-mercury snakes were apparently first made commercially in Germany, and
are at present fairly common in this country around the Fourth of July, in the form of
"Barrel Snakes" "Hat Snakes" (black pellets affixed to black discs of pasteboard to form
what look like miniature broad-brimmed black hats) "Colored Fire Snakes," and so forth.
The first indication of the possibility of such snakes appears to be a report by
Vorbringer [10] in 1867 that he had procured a brownish black product, which burned to
form black snakes, by the nitration of a certain black, resinous, acidic material from coal
tar, but he did not describe his raw material in such manner as to identify it and to make
it available to others. The method of making black snakes was kept secret, and does
not appear to have been described in accessible print until Weingart [11] published an
account of it in 1937. Ten parts of powdered "naphtha pitch" is mixed intimately with two
parts of linseed oil, seven parts of the strongest fuming nitric acid is added a little at a
time, and the mixture is allowed to cool for an hour. The product is washed thoroughly
with water, dried, powdered, mixed with three and one-half parts of powdered picric
acid, and made into pellets with gum-arabic water.
Several questions at once suggest themselves. What is "naphtha pitch?" Will some
more common material serve as well? What is the technic of nitrating twelve parts of
material, largely solid, with seven parts of nitric acid? Is the linseed oil necessary, and
what purpose does it serve?
Correspondence with various American manufacturers failed to discover anything
which is known as "naphtha pitch." A sample of "naphthol pitch," a by-product of the
manufacture of beta-naphthol, was kindly supplied by the Calco Chemical Division of
the American Cyanamid Company. This was a dark brown, shiny, brittle material,
having a conchoidal fracture and easily reduced to a cocoa-colored powder. In
response to an inquiry as to how he carried out the nitration, Mr. Weingart replied that
he "rubbed up the pitch with linseed oil in a Wedgewood mortar and added the acid, a
little at a time, so as to avoid excessive heating"—and kindly sent a sample of the
"naphtha pech" of German origin which he used in his own work. [12] This material was
a dark brown, almost black, granular powder. Both the "naphthol pitch" and the
"naphtha pech" reacted vigorously with nitric acid. When mixed with linseed oil and
nitrated by kneading (if we may give a name to the technic), each yielded a friable
product which burned to form a snake while a Bunsen flame was played upon it, but
which did not maintain its own combustion. Powdered with picric acid and made into
pellets as described, the product from each yielded excellent snakes, smooth skinned
and glossy with a luster like that of coke, elastic, and of spongy texture within. The
pellets burned with a luminous, sooty flame; a pellet one cm. long and eight mm. in
diameter gave a snake about 1.3 meters in length.
A satisfactory procedure was found to be as follows. Ten grams of powdered naphthol
pitch is mixed intimately with two grams of linseed oil, and the material is chilled in a
100-cc. pyrex beaker surrounded by cracked ice. Seven cc. (not seven grams) of
fuming nitric acid (density 1.50) is added in small portions, one drop at a time at first,
and the material is stirred over, kneaded, and kept thoroughly mixed at all times by
means of a porcelain spatula. The addition of each drop of acid, especially at the
beginning of the process, causes an abundance of red fumes, considerable heating,
and some spattering. It is recommended that goggles and rubber gloves be worn, and
that the operation be carried out in an efficient hood. The heat of the reaction causes
the material to assume a plastic condition, and the addition of the acid ought not to be
so slow that the material becomes hard. After all of the acid has been added, the dark
brown dough-like mass becomes friable on cooling. It is broken up under water with the
spatula, rinsed, and allowed to stand in water overnight, then washed thoroughly on the
filter and allowed to dry at laboratory temperature. The product is ground up with three
and one-half grams of picric acid, made into a moist meal with gum arabic water, and
pelleted. It yields about twenty pellets one cm. long and eight mm. in diameter. These
should be allowed to dry for four or five days at room temperature before they are used.
An experiment was carried out in accordance with these directions except that the
linseed oil was omitted. The powdered mixture of nitrated naphthol pitch and picric acid,
when made into pellets with gum-arabic water and dried, burned with a sooty flame, but
did not give snakes. Another portion of the mixture was made into a sticky meal with
linseed oil and compressed into pellets. The pellets, when lighted, started to give
snakes but did not maintain their combustion. After they had stood in the laboratory for
two months, during which time the linseed oil had oxidized and the pellets hardened,
they gave excellent snakes. The conclusion is indicated that oxidized linseed oil is
necessary for the formation of the snakes, and that this component of the mixture is
conveniently assured by mixing linseed oil with the naphthol pitch before nitration.
Since naphthol pitch is not easily procurable, some other material was sought-some
common laboratory chemical from which a chemist may easily prepare black snakes for
his own amusement or for the edification of students. Anthracene was tried with the
thought that the rather violent nitration is accompanied by oxidation, which perhaps
may result in the linking together of a number of aromatic nuclei, to form a material
predisposed toward the production of a carbonaceous residue-but the product melted in
the flame, gave no snakes, and did not maintain its combustion. Technical
beta-naphthol was found to be satisfactory. When the procedure described above was
tried with ten grains of technical betra-naphthol instead of ten grams of naphthol pitch,
seven cc. of fuming nitric acid (density 1.50), and so forth, the pellets gave good
snakes, thicker than those from the naphthol pitch but not so long, not so shiny,
blacker, and covered with wart-like protuberances or having a segmented appearance.
A similar experiment with beta-naphthol and seven cc. of ordinary c.p. nitric acid
(density 1.42) gave better snakes, somewhat longer and smoother than those from the
experiment in which fuming nitric acid was used, but still not as good as those from
naphthol pitch. The snakes from beta-naphthol, however, are perfectly good, and will
probably be satisfactory if none from naphthol pitch are available for comparison.
[1] Compare "An historical account of Pharaoh's serpents," by H. Irving in Sci. Progress,
30, 62-6 (1935). I am indebted to Professor Ernest H. Huntress for calling my attention
to this article.
[2] WÖHLER, Gilbert's Ann. d. Phys. u. phys. Chem., 9, 272 (1821). This is the same
as Volume 96 of Gilbert's Ann. d. Phys.
[3] BERZELIUS, Schweigger's J. f. Chem. u. Phys., 31, 42 (1821). This is the same as
Volume I of Jahrbuch d. Chem. u. Phys.
[4] CLAUS, J. prak. Chem., 15, 401 (1838).
[5] HERMES, J. prak. Chem., 97, 477 (1866). The statement Hermes, without
experimental support, that the voluminous, snake-like residue consists of melam, is
evidently in error,
[6] PHILIPP, Poggendorff's Ann. d. Phys. u. Chem., [5111,86 (1867)
[7] WEINGART, "Dictionary and manual of fireworks," Bruce Humphries, Inc., Boston,
1937, p. 152. This book contains many good formulas, and is recommended strongly to
the chemist who wishes to try his hand at the making of fireworks.
[8] WEINGART, loc. Cit., P. 154.
[9] The black "fuse" made by passing a few pieces of cotton string, twisted together,
through a slurry of finely pulverized back gunpowder and allowing to dry while stretched
on a frame.
[10] VORBRINGER, J. prakt. Chem., 102, 187-8 (1867). This is an editorial note, signed
"W" (Gustav Werther) based upon a letter from Vorbringer, describing experiments
carried out in the laboratory of the Mineral6l- und Paraffin-Fabrik des Herrn Dr. Hubner
in Rehmsdorf bei Zeitz.
[11] Weingart, loc. cit., pp. 152-3.
[12] Mr. Weingart also stated that he had obtained satisfactory results by using, instead
of "naphtha pech," the material procured by melting together sixty parts of Syrian
asphalt and forty of roofing pitch. Worked up in the regular way, this 11 yielded fairly
good snakes which were improved by rubbing the finished product up with a little
stearine before forming into pellets."
-----
The “Master Blaster Pastor” Ron Lancaster [not to be confused with the nine-
fingered Blaster Pastor!] commented on the AFN reprinted in The Best of The
AFN No. 3. April 1984.
He makes the following points: The quality of the pitch is critical, he suggest that
if you do not have access to beta-naphthol pitch, mix the pitch you do have with
linseed oil and nitrocellulose powder and then nitrate the whole lot together.
Ordinary nitric acid is not strong enough and fuming nitric acid is too strong,
therefore by trial and error you will have to add water.
I can say from personal experience – making snakes from (roofing) pitch/linseed
oil and fuming nitric acid is done by most once! It is not fun!! The mixture is a “C”-hair away from igniting spontaneously, and
have you ever tried to powder pitch?!
Or to make fuming nitric acid, the way the Merck Index suggests?! I would offer a
suggestion if you use their method: it takes a few minuets to get going, and when
it does …..! Use a WIDE mouthed vessel, or you will have a fuming nitric acid
volcano!
Yet another pyrotechnic snake is possible. The Reverend Lancaster reports in
AFN 31(March 1984) that organic chemist friend discovered that if para-
nitroacetanilide is heated with concentrated (1 ml) sulphuric acid in a large
evaporating dish, a large black snake suddenly shoots up in a long column of
ash. “It is quite interesting to do this in a laboratory situation but otherwise a little
impractical.” Leonard A. Ford, Chemical Magic, 1959 uses exactly the same
method.
--------
And there is yet a forth magic snake chemical! Details if/when
I get the time.
Industrial and Engineering Chemistry 44 [1] 120.
January 1952
donald j haarmann
---------------------
But science, spurred on by its energetic
notions, approaches irresistibly those
outer limits where the optimism implicit
in logic must collapse. For the periphery
of science has an infinite number of
points. Every noble and gifted man has,
before reaching the mid-point of his
career, come up against some point
of the periphery that defied his
understanding, quite apart from the
fact that we have no way of knowing
how the area of the circle is ever to
be fully charted. When the inquirer,
having pushed to the circumference,
realizes how logic in that place curls
about itself and bites its own tail, he
is struck with a new kind of perception:
a tragic perception, which requires, to
make it tolerable, the remedy of art."
