What happens in the reaction of ammonium dichromate and mercury(II) thiocyanate? I found this reaction of $\ce{NH4Cr2O7 + Hg(SCN)2 -&gt;[\Delta]\ ?}$ on youtube, and I'm curious as to how it works. I tried searching online, but didn't find much on it.

Thanks.
This is a combination of two reactions.  The first is the ammonium dichromate vocano and the second is called Pharaoh's snakes.

The volcano

The reaction occurring here is: $$\ce{(NH4)2Cr2O7(s) -&gt; Cr2O3(s) + N2(g) + 4 H2O(g)}$$  The reference above provides several pictures and a description of the chemistry.

Pharaoh's snakes

Again, the reference above describes what is happening, so only a summary of the chemical reactions is given here:
$$\ce{2 Hg(SCN)2-&gt;2 HgS + CS2 + C3N4}$$ $$\ce{CS2 + 3O2 -&gt; CO2 + 2SO2}$$ $$\ce{2C3N4-&gt;3(CN)2 + N2}$$ $$\ce{HgS + O2-&gt;Hg + SO2}$$

Pharaoh's snakes is a rather hazardous demonstration and should not be performed without the proper ventilation, protective gear and waste disposal equipment.