fulminate

[fuhl-muh-neyt]

fulminate, any salt of fulminic acid, HONC, a highly unstable compound known only in solution. The term is most commonly applied to the explosive mercury (II) fulminate, also called fulminate of mercury, Hg(ONC)₂. The pure compound forms white cubic crystals. It is made by the action of nitric acid on mercury metal in the presence of alcohol and is often collected as a gray or brown sandy powder. It is very sensitive to heat, shock, or friction and is used in primers, detonators, and blasting caps.

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Fulminate

Fulminates are chemical compounds which include the fulminate ion. The fulminate ion is a pseudohalic ion, acting like a halogen with its charge and reactivity. Due to the instability of the ion, they are friction-sensitive explosives. The best known is mercury fulminate which has been used as a primary explosive in detonators. Fulminates can be formed from metals, like silver and mercury, dissolved in nitric acid and reacted with alcohol. The chemical formula for the fulminate ion is O⁻N⁺C⁻. It is largely the presence of the weak single nitrogen-oxygen bond which leads to its instability. Nitrogen very easily forms a stable triple bond to another nitrogen atom, forming gaseous nitrogen.

Historical notes

Fulminates were discovered by Edward Charles Howard in 1800.. Their use in firearms in a fulminating powder was first demonstrated by a Scottish minister, A. J. Forsyth, who was granted a patent in 1807. Joshua Shaw then made the transition to their use in metallic encapsulations, to form a percussion cap, but did not patent his invention until 1822.

In the 1820s, the organic chemist Justus Liebig discovered silver fulminate (Ag-CNO) and Friedrich Wöhler discovered silver cyanate (Ag-OCN). The fact that these substances have the same chemical composition led to an acrid dispute, which was not resolved until Jöns Jakob Berzelius came up with the concept of isomers.