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Weirdest Chemical Reaction: Mercury (II) Thiocyanate

Updated on August 16, 2013

Pharaoh's Serpent

Pharaoh's Snakes Chemical Reaction
Pharaoh's Snakes Chemical Reaction

Mercury (II) thiocyanate Chemical Reaction

When Mercury (II) thiocyanate is exposed to a high temperature source an exothermic reaction is started. It produces a large mass of coiling serpent-like solid. An inconspicuous flame which might be blue in color might be seen but can also be in yellow or orange. The resulting solid might have a dark grey color or light tan or colors in between the two with the inside generally much darker than the outside.

This reaction was discovered by a person by the name of Wohler in 1821. Back in his time the Pharaoh's serpent was made into a firework called 'Pharaoschlangen' and it was available to the public in Germany. It was created mainly for amusement, but it was eventually banned when the toxic properties of the product (Mercury) were discovered through the death of several children mistakenly eating the resulting solid. The fumes as well of Mercury was toxic to the body.

pharaoh's serpent
pharaoh's serpent

Mercury (II) thiocyanate being Ignited (Footage 1)

Mercury (II) thiocyanate being Ignited (Footage 2)

Health hazards

Grey fumes of Mercury are produced during the reaction which is poisonous to the human heath, it is advised to ignite the chemical within a fume chamber or outdoors.

Laboratory manufacturing of Pharaoh's Serpent

Mercury (II) thiocyanate can be made by reacting mercury solutions and thicyanate solutions. Example Concentrated Potassium thiocyanate and Mercury nitrate.

Mercury compounds are extremely toxic to your body, (blocks enzymatic reactions and afects neuron communications in the brain) so protective equipment should be used whenever attempting to react mercury thiocyanate. Unfortunately the realization of its toxic property was discovered few years ago, and before that it used to be cheaply available in chemical shops, which lead to couple of deaths. However, it is still commercially available today, though expensive.

New and Safer Version of Pharaoh's Serpent (Black Snake)

Mercury (ii) Thiocyanate was found to be a little bit toxic for the kids, so they came up with a new kind of Serpent that looks a little like Pharaoh’s Serpent, but are not quite that dramatic and fun as the original one. These are called Black Snakes. It is the safe versions made with sugar and baking soda. The sugar burns just like it would in a marshmallow to create a lightweight carbon ash, the reaction is slow and the length of the serpent is not that big. What actually happens is that the heated baking soda makes carbon dioxide gas that inflates the ash.

Black Snake Demonstration

Making of the Black Snake at home

Black Snakes can be made at home using simple materials found in your kitchen. The black snake in the video above is however not the same as what we are about to make. The above one is as a result of mixing concentrate Sulfuric Acid with sugar.

For our simple Black Snake, What you'll need is:

  1. Tray
  2. Sand
  3. Igniting fluid
  4. Powder Sugar
  5. Backing Soda
  6. Lighter


  1. Place the pile of sand onto a tray. make it form a heap and punch a hole right in the middle with your finger. Not too deep that you can see the tray.
  2. Take the flammable liquid (Igniting Liquid) and sprinkle enough into the hole, not too much that it soaks the whole sand.
  3. Mix equal amounts of Backing Soda and powder Sugar in a bowl.
  4. Put some of the mixture in the hole, don't put much that it forms a heap at the top of the sand.
  5. Using the lighter, ignite the visible liquid on the sand, then watch!

Video: Making Pharaoh's Serpent at Home

It not as fun and dramatic as Mercury (II) thiocyanate, but its worth trying.

© 2013 ElijahWex


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