GUNPOWDER. 219 



Throw a handful of saltpetre into a gocd cinder fire ; a most 

 brilliant deflagration will result, the action being precisely the 

 same as with the charcoal and fused saltpetre above described. 



Paper soaked in a solution of saltpetre and dried will undergo 

 a peculiar kind of rapid smouldering combustion when lit by 

 touching with a red-hot cinder or otherwise ; touch paper is thus 

 prepared to form the portion of squibs, rockets, and suchlike fire- 

 works intended to be lit. Tobacco and cigars largely owe their 

 power of keeping alight whilst not being actually smoked in the 

 mouth to the presence of small quantities of saltpetre naturally 

 contained in the tobacco leaf, or added during manufacture for the 

 purpose. Pastilles are somewhat similar in their action, being 

 generally composed of powdered charcoal and saltpetre with 

 various aromatic gums, &c., added so as to develop a pleasant 

 scent whilst smouldering ; a kind of tape known as " Eibbon of 

 Bruges " and by other names is sometimes prepared in a similar 

 fashion, for the purpose of producing an incense-like odour when 

 a piece of it is lighted and allowed to smoulder. 



Expt. 259. To prepare Gunpowder. Gunpowder is manu- 

 factured by grinding saltpetre to powder and mixing with it 

 finely ground charcoal and sulphur, the proportions used varying 

 with the quality of powder to be prepared, but usually being 

 somewhere about 



Saltpetre, 75 parts in 100 



Charcoal, 12 J ,, 



Sulphur, 12 



100 



The charcoal employed is prepared from special kinds of wood, 

 dogwood and alder being preferred ; the pulverised substances are 

 moistened with water to diminish the risk of firing, and then 

 well ground together to form an intimate intermixture ; the mass 

 is then strongly compressed, and the " press cake " obtained broken 

 up by a suitable machine, the fragments being sifted, dried by 

 steam heat, and glazed or polished by placing them in revolving 

 barrels, so that the grains rub against one another; for large 

 grains or "pebble powder" where each grain is as large as a hazel 

 nut or walnut, a somewhat different method of granulation is 

 requisite. These mechanical operations of intermixing, compress- 

 ing, and graining are indispensable in order to obtain a mixture 

 suitable for fire-arms ; on the small scale, a pestle and mortar may 

 be employed to intermix the ingredients, previously well damped 

 so as to form a very stiff" paste when ground together ; this paste 

 may be spread out in a thin layer on a plate to dry in the air, and 



