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"Black snake" is a term that can refer to two similar types of
firework Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices in ...
, the Pharaoh's snake and the sugar snake. The "Pharaoh's snake" or "Pharaoh's serpent" is the original version of the black snake experiment. It produces a more impressive snake, but its execution depends upon mercury (II) thiocyanate, which is no longer in common use due to its toxicity. For a "sugar snake",
sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
and
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double s ...
are the commonly used chemicals. Once lit, both fireworks emit smoke and spew out ash resembling a snake via an
intumescent An intumescent is a substance that swells as a result of heat exposure, leading to an increase in volume and decrease in density. Intumescent materials are typically used in passive fire protection and require listing, approval, and compliance in ...
reaction. They remain on the ground and emit no sparks, flares, projectiles, or sound.


Pharaoh's snake

The Pharaoh's snake is a more dramatic experiment, yet it requires more safety precautions than the sugar snake due to the presence of toxic mercury vapor and other mercury compounds.


History

This reaction was discovered by Wöhler in 1821, soon after the first synthesis of mercury thiocyanate. It was described as "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." For some time, a firework product called "Pharaoschlangen" was available to the public in Germany but was eventually banned when the toxic properties of the product were discovered through the deaths of several children who had mistakenly consumed the resulting solid.


Description

The Pharaoh's snake experiment is conducted in the same manner as the sugar snake experiment, however, the former uses
mercury(II) thiocyanate Mercury(II) thiocyanate (Hg(SCN)2) is an inorganic chemical compound, the coordination complex of Hg2+ and the thiocyanate anion. It is a white powder. It will produce a large, winding "snake" when ignited, an effect known as the Pharaoh's serp ...
(Hg(SCN)2) instead of powdered sugar with baking soda. This must be done in a fume hood because all mercury compounds are hazardous.


Chemical reactions

After igniting the reagents, mercury(II) thiocyanate breaks down to form mercury(II) sulfide (HgS),
carbon disulfide Carbon disulfide (also spelled as carbon disulphide) is a neurotoxic, colorless, volatile liquid with the formula and structure . The compound is used frequently as a building block in organic chemistry as well as an industrial and chemical non ...
(CS2), and carbon nitride (C3N4).
Graphitic carbon nitride Graphitic carbon nitride (g-C3N4) is a family of carbon nitride compounds with a general formula near to C3N4 (albeit typically with non-zero amounts of hydrogen) and two major substructures based on heptazine and poly(triazine imide) units which, ...
, a pale yellow solid, is the main component of the ash. :2 Hg(SCN)2(s) → 2 HgS(s) + CS2(l) + C3N4(s) Carbon disulfide ignites into carbon dioxide (CO2) and sulfur(IV) oxide (SO2). :CS2(l) + 3 O2(g) → CO2(g) + 2 SO2(g) While carbon nitride (C3N4) will break down into nitrogen gas and dicyan :2 C3N4(s) → 3 (CN)2(g) + N2(g) When mercury(II) sulfide (HgS) reacts with
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well ...
(O2), it will form gray mercury vapor and
sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
. If the reaction is performed inside a container, a gray film of mercury coating on its inner surface can be observed. :HgS(s) + O2(g) → Hg(l) + SO2(g)


Sugar snake

Unlike the carbon snake, which involves the reaction of
sulfuric acid Sulfuric acid ( American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...
instead of
sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
, the sugar snake grows relatively faster and to a significantly larger volume.


Description

Solid fuel is used in this experiment. The solid fuel can be sand that is sufficiently covered in
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a hyd ...
or
hexamethylenetetramine Hexamethylenetetramine, also known as methenamine, hexamine, or urotropin, is a heterocyclic organic compound with the formula (CH2)6N4. This white crystalline compound is highly soluble in water and polar organic solvents. It has a cage-like ...
. A white mixture of sucrose and
sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
will eventually turn black and the snake will grow about long after it is lit.


Chemical reactions

Three
chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the positions of electrons in the forming and breakin ...
s occur when the snake is lit.
Sodium bicarbonate Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
breaks down into sodium carbonate,
water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous phase ...
, and carbon dioxide: : 2 NaHCO3(s) → Na2CO3(s) + H2O(g) + CO2(g) Burning sucrose or
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a hyd ...
(reaction with
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well ...
in the air) produces carbon dioxide gas and
water vapor (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous phase ...
: : C12H22O11(s) + 12 O2(g) → 12 CO2(g) + 11 H2O(g) : C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) Some of the sucrose does not burn, but merely decomposes at the high temperature, giving off elemental carbon and water vapor: : C12H22O11(s) → 12 C(s) + 11 H2O(g) The carbon in the reaction makes the snake black. The overall process is
exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity ( ...
enough that the water produced in the reactions is
vaporize Vaporization (or vaporisation) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon ...
d. This steam, in addition to the carbon dioxide product, makes the snake lightweight and airy and allows it to grow to a large size from a comparably small amount of starting material.


Use

It is a popular firecracker item in
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
, which children play with during the festival of
Diwali Diwali (), Dewali, Divali, or Deepavali ( IAST: ''dīpāvalī''), also known as the Festival of Lights, related to Jain Diwali, Bandi Chhor Divas, Tihar, Swanti, Sohrai, and Bandna, is a religious celebration in Indian religions. It is o ...
. Though deemed toxic by the Chest Research foundation and Pune University, black snake fireworks are still in use. The objective of the study was to determine which firework produced the most air pollution in India. The conducted study showed that the snake fireworks emitted the highest particulate matter, capable of penetrating the lungs via inhalation of smoke particles and consequently, causing significant damage. Other firecrackers that emit huge amounts of smoke particles include fuljhadi, pulpul, chakris and annar.


See also

* Chemical volcano *
Diet Coke and Mentos eruption A Diet Coke and Mentos eruption (also known as a soda geyser) is a reaction between the carbonated beverage Diet Coke and Mentos mints that causes the beverage to be expelled from its container. The candies catalyze the release of gas from the ...
* Elephant's toothpaste *
Intumescent An intumescent is a substance that swells as a result of heat exposure, leading to an increase in volume and decrease in density. Intumescent materials are typically used in passive fire protection and require listing, approval, and compliance in ...
*
Starlite Starlite is an intumescent material said to be able to withstand and insulate from extreme heat. It was invented by British hairdresser and amateur chemist Maurice Ward (1933–2011) during the 1970s and 1980s, and received significant public ...


References

{{Reflist Articles containing video clips Types of fireworks Chemistry classroom experiments