such as glycollic acid, remain in solution.  The mercury fulminate is then crystallised from hot water.  It forms white silky, delicate needles, which are with difficulty soluble in cold water.  In the dry state it is extremely explosive, detonating on heating, or by friction or percussion, as also on contact with concentrated sulphuric acid.  The reaction that takes place upon its decomposition is as follows:—­

C_{2}N_{2}O_{2}Hg = Hg + 2CO + N_{2}
(284)

According to this equation 1 grm. of the fulminate should yield 235.8 c.c. (= 66.96 litres for 284 grms.).  Berthelot and Vicille have obtained a yield of 234.2 c.c., equal to 66.7 litres for one equivalent 284 grms.

Dry fulminate explodes violently when struck, compressed, or touched with sulphuric acid, or as an incandescent body.  If heated slowly, it explodes at 152 deg.  C., or if heated rapidly, at 187 deg.  C. It is often used mixed with potassium chlorate in detonators.  The reaction which takes place in this case is 3C_{2}N_{2}O_{2}Hg + 2KClO_{3} = 3Hg + 6CO_{2} + 3N_{2} + 2KCl.

On adding copper or zinc to a hot saturated solution of the salt, fulminate of copper or zinc is formed.  The copper salt forms highly explosive green crystals.  There is also a double fulminate of copper of ammonia, and of copper and potassium.  Silver fulminite, C_{2}N_{2}O_{2}Ag_{2}, is prepared in a similar manner to the mercury salt.  It separates in fine white needles, which dissolve in 36 parts of boiling water, and are with difficulty soluble in cold water.  At above 100 deg.  C., or on the weakest blow, it explodes with fearful violence.  Even when covered with water it is more sensitive than the mercury salt.  It forms a very sensitive double salt with ammonia and several other metals.  With hydrogen it forms the acid fulminate of silver.  It is used in crackers and bon-bons, and other toy fireworks, in minute quantities.  Gay Lussac found it to be composed as follows:—­Carbon, 7.92 per cent.; nitrogen, 9.24 per cent.; silver, 72.19 per cent.; oxygen, 10.65 per cent.; and he assigned to it the formula, C_{2}N_{2}Ag_{2}O_{2}.  Laurent and Gerhardt give it the formula, C_{2}N(NO_{2})Ag_{2}, and thus suppose it to contain nitryl, NO_{2}.

On adding potassium chloride to a boiling solution of argentic fulminate, as long as a precipitate of argentic chloride forms, there is obtained on evaporation brilliant white plates, of a very explosive nature, of potassic argentic fulminate, C(NO_{2})KAg.CN, from whose aqueous solution nitric acid precipitates a white powder of hydric argentic fulminate, C(NO_{2})HAg.CN.  All attempts to prepare fulminic acid, or nitro-aceto-nitrile, C(NO_{2})H_{2}CN, from the fulminates have failed.  There is a fulminate of gold, which is a violently explosive buff precipitate, formed when ammonia is added to ter-chloride of gold, and fulminate of platinum, a black precipitate formed by the addition of ammonia to a solution of oxide platinum, in dilute sulphuric acid.