COMPOSITION OF GUNPOWDEK, ETC. 205 



aid of a gentle heat. To the solution, while still hot, add 

 2 ounces by measure of alcohol, continuing the heat till re- 

 action commences, when the nitric acid oxidises part of the 

 alcohol to aldehyde and oxalic acid, becoming itself reduced 

 to nitrous acid. The last-named acid in its turn acts upon 

 the alcohol, the result being the production of nitrous ether, 

 fulminic acid, and water. From the hot liquid the fulminate 

 of silver is slowly deposited in the form of small, white, 

 brilliant crystalline plates, which should be washed with a 

 little cold water, and spread upon separate pieces of filter- 

 paper, in portions not more than a grain or two each, after 

 which they are left to dry in a warm place. When dry the 

 papers are gently folded up and preserved separately in a 

 box or bottle, this being the only safe mode of keeping the 

 salt. It is one of the most dangerous of all chemical sub- 

 stances to handle, and explodes when heated, or when rubbed 

 or struck with a hard body, or when brought in contact 

 with concentrated sulphuric acid, with an enormous force, 

 owing to the sudden disengagement of a large volume of 

 gaseous matter, leaving the metal reduced. 



When fulminate of silver is digested with caustic potass, 

 one half of the oxide is precipitated, and a compound is 

 produced which resembles the neutral salt of silver, and 

 detonates with a blow. Tins is sometimes used for the 

 manufacture of anticorrosive percussion caps, but it has very 

 little advantage over the 



Fulminate of mercury, which is prepared by a process very 

 similar to that described for fulminate of silver. One part 

 of mercury is dissolved in twelve parts of nitric acid, specific 

 gravity 1/37, the solution being mixed with an equal quantity 

 of alcohol ; gentle heat is then applied, and if the reaction 

 becomes very violent, it may be kept down by the addition 

 of more spirit as required. A large volume of carbonic acid, 

 nitrogen, nitrous and aldehyde, and red vapour is disengaged, 

 and the hot liquid deposits the fulminate of mercury, which 

 may be purified by solution in boiling water and re-crystal- 

 lization. It explodes either by friction or percussion, and 

 when fired burns with a sudden and almost noiseless flash if 

 kindled in the open air. 



To form the mixture which is used in the ordinary caps. 



