Mercury(II) nitrate

Mercury(II) nitrate, also known as mercuric nitrate, is a chemical compound. Its chemical formula is Hg(NO3)2. It contains mercury and nitrate ions. The mercury is in its +2 oxidation state. 
Properties.
Mercury(II) nitrate is a white crystalline solid. It is a strong oxidizing agent. 
Preparation.
It is made by reacting mercury with concentrated nitric acid; dilute nitric acid would make mercury(I) nitrate.
Uses.
It was used to make felt from fur. People would get poisoned when using it to make hats, making the term "mad hatter".