Fulminating silver is a compound obtained by the action of ammonia on oxide of silver.  It is a very violent explosive.  Pure mercury fulminate may be kept an indefinite length of time.  Water does not affect it.  It explodes at 187 deg.  C., and on contact with an ignited body.  It is very sensitive to shock and friction, even that of wood upon wood.  It is used for discharging bullets in saloon rifles.  Its inflammation is so sudden that it scatters black powder on which it is placed without igniting it, but it is sufficient to place it in an envelope, however weak, for ignition to take place, and the more resisting the envelope the more violent is the shock, a circumstance that plays an important part in caps and detonators.  The presence of 30 per cent. of water prevents decomposition, 10 per cent. prevents explosion.  This is, however, only true for small quantities, and does not apply to silver fulminate, which explodes under water by friction.  Moist fulminates slowly decompose on contact with the oxidisable metals.  The (reduced) volume of gases obtained from 1 kilo. is according to Berthelot, 235.6 litres.  The equation of its decomposition is C_{2}HgN_{2}O_{2} = 2CO + N_{2} + Hg.

Fulminate of mercury is manufactured upon the large scale by two methods.  One of these, commonly known as the German method, is conducted as follows:—­One part of mercury is dissolved in 12 parts of nitric acid of a specific gravity of 1.375, and to this solution 16.5 parts of absolute alcohol are added by degrees, and heat is then slowly applied to the mixture until the dense fumes first formed have disappeared, and when the action has become more violent some more alcohol is added, equal in volume to that which has already been added.  This is added very gradually.  The product obtained, which is mercury fulminate, is 112 per cent. of the mercury employed.  Another method is to dissolve 10 parts of mercury in 100 parts of nitric acid of a gravity of 1.4, and when the solution has reached a temperature of 54 deg.  C, to pour it slowly through a glass funnel into 83 parts of alcohol.  When the effervescence ceases, it is filtered through paper filters, washed, and dried over hot water, at a temperature not exceeding 100 deg.  C. The fulminate is then carefully packed in paper boxes, or in corked bottles.  The product obtained by this process is 130 per cent. of the mercury taken.  This process is the safest, and at the same time the cheapest.  Fulminate should be kept, if possible, in a damp state.  Commercial fulminate is often adulterated with chlorate of potash.

Detonators, or caps, are metallic capsules, usually of copper, and resemble very long percussion caps.  The explosive is pure fulminate of mercury, or a mixture of that substance with nitrate or chlorate of potash, gun-powder, or sulphur.  The following is a common cap mixture:—­ 100 parts of fulminate of mercury and 50 parts of potassium nitrate, or 100 parts of fulminate and 60 parts of meal powder.  Silver fulminate is also sometimes used in caps.  There are eight sizes made, which vary in dimensions and in amount of explosive contained.  They are further distinguished as singles, doubles, trebles, &c., according to their number.  Colonel Cundill, R.A. ("Dict. of Explosives"), gives the following list:—­