Mercury(II) nitrate

Mercury(II) nitrate is a toxic colorless or white soluble crystalline mercury(II) salt of nitric acid. It was also used to treat fur to make felt in a process called 'carroting'. The phrase 'mad as a hatter' is associated with psychological illness brought on by excessive exposure to mercury(II) nitrate. The practice continued in the United States until it was banned in December 1941 by the United States Public Health Service. Although this sounds beneficial to health, the ban actually freed mercury(II)nitrate to be used as a detonator in the then ongoing war.