[Cherostavik]

I was heating some ammonium nitrate and tbh forgot to set my usual 5 min alerts, and when I came back to check it I had a boiling, smoking, disgusting black liquid. Taken off heat it practically turned to cement and had to be chipped out of the beaker. I've hot filtered it through basic paper filters, recrystallized it, and ran acetone over the broken up crystals (I don't have a vacuum filter yet). Whatever the decomp product is, it's soluble in acetone and heavy enough in it to form a visible layer between store bought acetone, making a brown liquid. My question is, what actually IS this substance?

[Enthalpy]

Welcome, Cherostavik! Happy to learn that it didn't kill you.