How to make the Pharoah’s Serpent (Mercury (II) Thiocyanate). Mercury (II) thiocyanate is made using potassium thiocyanate, mercury and concentrated nitric acid.
How to perform the Pharaoh’s Serpent
“Igniting mercury(II) thiocyanate causes it to decompose into an insoluble brown mass that is primarily carbon nitride, C3N4. Mercury(II) sulfide and carbon disulfide are also produced.
2Hg(SCN)2 → 2HgS + CS2 + C3N4
Flammable carbon disulfide combusts to carbon(IV) oxide and sulfur(IV) oxide:
CS2 + 3O2 → CO2 + 2SO2
The heated C3N4 partially breaks down to form nitrogen gas and dicyan:
2C3N4 → 3(CN)2 + N2
Mercury(II) sulfide reacts with oxygen to form mercury vapor and sulfur dioxide. If the reaction is performed inside a container, you will be able to observe a gray mercury film coating its interior surface.
HgS + O2 → Hg + SO2
“Helmenstine, Anne Marie, Ph.D
Safety & Disposal
Although Pharaoh’s snakes are considered a type of firework, they do not explode or emit sparks. They burn on the ground and release smoky vapors. All aspects of the reaction can be hazardous, including handling the mercury thiocyanate, breathing the smoke or touching the ash column, and contact with the remains of the reaction during clean-up. If you perform this reaction, use appropriate safety precautions for dealing with mercury.
The use of this instruction and the information provided therein takes place at the user’s own risk.