Forgotten Chemical Reaction

Factual Questions
1

I’m trying to remember the following chemical reaction.

Does anyone know what it is?

Thanks

2

Mercury Thiocyanate: https://www.youtube.com/watch?v=dX7xeF-ywxc

3

Or did you want the formula:http://chemistry.about.com/b/2011/05/12/pharoahs-snake-firework-or-chemistry-demonstration.htm

4

Excellent, That’s it.

Thank you.