Silver fulminate (AgCNO) is the highly explosive silver salt of fulminic acid. Silver fulminate is a primary explosive, but has limited use as such due to its extreme sensitivity to impact, heat, pressure, and electricity. The compound becomes progressively sensitive as it is aggregated, even in small amounts; the touch of a falling feather, the impact of a single water droplet, or a small static discharge are all capable of explosively detonating an unconfined pile of silver fulminate no larger than a dime and no heavier than a few milligrams. Aggregating larger quantities is impossible, due to the compound's tendency to self-detonate under its own weight. Silver fulminate was first prepared in 1800 by Edward Charles Howard in his research project to prepare a large variety of fulminates. Along with mercury fulminate, it is the only fulminate stable enough for commercial use. Detonators using silver fulminate were used to initiate picric acid in 1885, but since have only been used by the Italian Navy. The current commercial use has been in producing non-damaging novelty noisemakers as children's toys. Structure Silver fulminate occurs in two polymorphic forms, an orthorhombic one and a trigonal one with a rhombohedral lattice. The trigonal polymorph consists of cyclic hexamers, (AgCNO)6. Properties Fulminates are very toxic, about the same as cyanides. When pure, silver fulminate is chemically very stable, not decomposing after years of storage. Like many silver salts, it darkens with light exposure. It is only slightly soluble in cold water and can be recrystallized using hot water. It can also be recrystallized from a 20% solution of ammonium acetate. It is not hygroscopic and can explode when moist or under water; it was reported to remain explosive after 37 years under water. It explodes upon contact with concentrated sulfuric acid or chlorine or bromine, but not when contacting iodine. It is insoluble in nitric acid, but dissolves in ammonia, alkali chlorides, alkali cyanides, aniline, pyridine, and potassium iodide by forming complexes. Concentrated hydrochloric acid decomposes it non-explosively with a hissing noise; thiosulfate also decomposes it non-explosively, and can be used for disposal. Preparation This compound can be prepared by pouring a solution of silver nitrate in nitric acid into ethanol, under careful control of the reaction conditions, to avoid an explosion. The reaction is usually done at 8090 °C; at 30 °C, the precipitate may not form. Only very tiny amounts of silver fulminate