FULMINATING GOLD AND SILVER. 185 



in a short time the powder becomes brown and acquires a pasty 

 consistence ; a blue lambent flame then appears on the surface, 

 and in an instant after the whole explodes with a stunning noise 

 and a slight momentary flash. If the mass be removed from the 

 fire as soon as it is fused, and kept in a dry well. closed vial, it may 

 at any time be exploded by a spark, in which case it burns like 

 gunpowder, but more rapidly and with greater detonation ; but 

 this effect cannot be produci-d on the unmelted powder, how accu- 

 rately soever the ingredients of it are mixed together. When 

 fulminating powder is in fusion, but not heated to the degree ne- 

 cessary to produce the blue flame, a particle of ignited charcoal 

 thrown upon it will occasion immediately a remarkably loud ex. 

 plosion. 



It appears that the ingredients of this powder do not acquire 

 their fulminating property till combined by fusion ; in other words, 

 till the pot. ash of sulphur form sulphuret of pot-ash : whence ful- 

 minating powder may also be made by mixing sulphuret of pot- 

 ash with nitre, instead of by adding the sulphur and alkali sepa- 

 rate. 



In all these the cause of the detonation, or fulminatidn, is not 

 accurately understood. In simple fulminating powder, there is a 

 very large portion of elastic gass evolved ; in fulminating gold 

 or silver, a much smaller ; yet the explosion in the latter case is 

 infinitely greater than that in the former. 



Fulminating Gold. 



Dissolve pure gold in nitro-muriatic acid to saturation, and di- 

 lute the solution with three times its bulk of distilled water, and 

 add to it gradually some pure ammonia ; a yellow precipitate will 

 be obtained, which must be repeatedly washed with distilled water, 

 and dried on a chalk stone, or in a filter. When perfectly dry, it is 

 called fulminating gold, and detonates by heat, as may be shewn 

 by heating a few grains of it on the point of a knife over the candle. 



* 



Fulminating Silver. 



Dissolve fine silver in pale nitric acid, and precipitate the solu- 

 tion by lime. water ; decant the fluid, mix the precipitate with 

 liquid ammonia, and stir it till it assumes a black colour j then de. 

 cant the fluid, and leave it in the open air to dry. This product is 

 fulminating silver, which when once obtained cannot be touched 



