Fulminate
Collier's New Encyclopedia (1921)
Important: Safety Warning
This page contains instructions involving gunpowder or other explosive or pyrotechnic compositions. Preparing explosives as described has caused severe injuries and deaths, and is illegal in most places.
In addition, this page contains a formula or preparation using substances now known to be dangerously toxic, such as arsenic, mercury, lead, or cyanide compounds. Exposure to these substances can cause severe poisoning, permanent injury, or death.
This information has been left in for historical purposes but should not be acted upon.
in chemistry, a salt of fulminic acid. Fulminate of mercury is prepared by dissolving 1 part of mercury in 12 parts of nitric acid; the solution is mixed with an equal volume of alcohol when cold. The mixture is then gently heated on a water bath. Red vapors are given off of nitrogen oxides and CO2, and a large quantity of nitrous ether, aldehyde, and other products. When the liquid becomes turbid it is allowed to cool, and the salt separates out; it is purified by recrystallization from boiling water. It forms white needles, which, when heated to 186°, explode, also by friction or percussion when dry. It is used for charging percussion caps; one kilogram of mercury will make fulminate sufficient for 40,000 caps. Fulminates have been regarded as methyl cyanide in which one atom of hydrogen has been replaced by NO2, and two atoms of hydrogen by mercury or silver. The action of chlorine on mercuric fulminate under water forms chloropicrin, CCl2 (NO2), mercuric chloride HgCl2, and cyanogen chloride CnCl. Hot nitric acid decomposes mercuric fulminate, yielding carbonic acid, acetic acid, and mercuric nitrate. Hydrochloric acid converts it into mercuric chloride and mercurous oxalate. When boiled with an aqueous solution of potassium chloride it is converted into potassium fulminurate. Fulminate of silver is obtained by heating nitrate of silver with strong nitric acid and alcohol till the liquid boils up. It is very dangerous to prepare. It crystallizes in small, white, opaque needles; it is very poisonous, and explodes lodes by friction or percussion, or when heated. It is soluble in aqueous ammonia, and deposits the fulminate unaltered. When silver fulminate is digested with water and metallic copper or zinc, the silver is replaced and copper fulminate or zinc fulminate is obtained. When fulminate of copper is mixed with ammonia, and a stream of H₂C gas is passed through the solution, the copper is completely precipitated, and the filtered solution contains hydrosulphocyanic acid and urea. Fulminate of gold was discovered by a monk in the 15th century. This substance, which explodes more rapidly and with greater local force than gun 4 powder, is made by precipitating a solution of chloride of gold by an excess of ammonia.
What Has Changed in the Last Century
Collier's in 1921 still described fulminates through a guess at their structure — "methyl cyanide in which one atom of hydrogen has been replaced by NO2" — because the real arrangement was not settled; the fulminate ion is now known to be CNO⁻, a linear isomer of cyanate, and the crystal structure of mercury fulminate itself was only determined by X‑ray work in 2007. Industrially the compound has been retired: from the 1920s and 1930s onward percussion caps and primers moved to lead azide, lead styphnate and tetryl, and later to non‑toxic mixes such as diazodinitrophenol, so almost no modern ammunition uses the "40,000 caps" chemistry described here. The recipes on this page are also now understood as genuinely lethal rather than merely delicate — mercury and silver fulminate preparation has killed and maimed chemists, and the mercury compounds are regulated toxics. One curiosity has gone the other way: free fulminic acid, HCNO, was characterised as a real, isolable species in the twentieth century and has since been detected in interstellar gas clouds.
Written for this edition, 2026.