Mercury fulminate is highly sensitive to heat and friction, which is what causes it to detonate on impact with objects. Throughout the 19th and mid-20th centuries it was used as the explosive component of black-powder firearm caps as well as rifle and pistol cartridges and shotgun shell primers. The primer is the component of a cartridge that is responsible for initiating the combustion of the primary explosive charge (the gunpowder) in the cartridge. When the primer is struck by a firearm's hammer, the friction caused by the impact causes the mercury fulminate to undergo a exothermic reaction (detonation), and the combustion then in turn ignites the gunpowder. Mercury fulminate was replaced as the main component of primers in the late 20th century because it tended to degrade over time: it would break down into its constituent elements, and the mercury in it would react with the brass in the cartridge weakening its structural integrity. It was replaced with less toxic and more stable chemicals like lead azide, lead styphnate, and tetrazene.
Jennifer Van Dyck has played five different characters over the course of the series:
- Episode 1.21 Sonata for Solo Organ (1991) - Joanna Woodleigh.
- Episode 4.16 Big Bang (1994) - Shelly Conners.
- Episode 7.6 Double Blind (1996) - Jill Perry.
- Episode 9.21 Ambitious (1999) - Morgana Palmer.
- Episode 12.14 Missing (2002) - Morgana Palmer.
- Episode 16.19 Positive (2006) - Dr. Elaine Clemens.
This episode features a crime that is partly inspired by The Anarchist Cookbook.
Dan Ziskie has played six different roles over the course of the series:
- Episode 5.19 Cruel and Unusual (1995) - George Jeffries.
- Episode 7.6 Double Blind (1996) - Fred Sawyer.
- Episode 9.11 Ramparts (1999) - Captain Gene Sayres.
- Episode 11.23 Judge Dread (2001) - State Police Investigator.
- Episode 14.12 Payback (2004) - Joshua Kramer.
- Episode 16.12 Family Friend (2006) - Captain Tom Baden.
John Bedford Lloyd has played three different roles over the course of the series:
- Episode 2.14 Blood Is Thicker... (1992) - Jonathan Ryder.
- Episode 7.6 Double Blind (1996) - Dr. Christian Varick.
- Episode 16.8 New York Minute (2005) - Prentiss's Lawyer.