NITRE. 469 



of the powder.* As each additional volume of gas exerts a force 

 equal to that of the atmosphere, 1000 X 15 = 15000 pounds on a 

 square inch, which will project a bullet with a force of 2000 feet in 

 a second, j- The general rule for powder for heavy shot is one third 

 of the weight of the shot, for lighter artillery one fourth. Count 

 Rumford found that 18 grains of gunpowder raised a weight of 18000 

 Ibs. The goodness of gunpowder is judged of by the force with 

 which it impels projectiles ; it is measured in an instrument called an 

 eprouvette. A rude analysis of gunpowder is easily effected by dis>- 

 solving the nitre by water and then subliming the sulphur out of the 

 charcoal. J 



(f.) Pulvis fulminans or fulminating powder. $*It is made of 3 

 parts of nitre, 2 pearl ashes and 1 sulphur, well dried and thor- 

 oughly mixed, by gentle trituration in a warm mortar. It is placed 

 in a spoon and heated by a candle or the embers till it gradually 

 blackens and melts, when it explodes, with a sharp and loud report. 

 If the heat is raised too high or too rapidly, the powder is decompo- 

 sed and does not explode. 



(g.) Theory. Similar to that of gunpowder, but the explosion 

 happens only when all the mass is melted, and the gases are disen- 

 gaged instantaneously, whereas the grains of gunpowder || burn suc- 



* Vide Robbing' Essay on Gunnery, and Nich. Jour. IV, 258. t Murray. 



t For an accurate method by Gay Lussac, see Ann. de Ch. et de Phys. XVI, 434. 



This powder is used by sportsmen for priming, to insure the discharge of their 

 fowling pieces. For this purpose it is slowly melted over the fire, care being taken 

 to stir it frequently. When the fusion is complete, it is taken off and stirred until 

 cool, which leaves it in the state of a fine powder. It must be kept in close vessels, 

 since it rapidly attracts moisture from the atmosphere. 



|| Composition formerly used for firing artillery is 60 nitre, 40 sulphur and 20 

 gunpowder; rammed into a small pasteboard cylinder. 



Chinese blue lights for signals, 28 nitre, 7 sulphur, 2 arsenic, & apart rice flour, 

 and water enough to knead them into a stiff paste ; the water and flour retard the 

 combustion ; this paste is rammed into little earthen pots and kept in pitched cloths. 



Fire balls to be thrown into an enemy's camp, 40 nitre, 15 charcoal, 3 pitch and 

 a little sulphur. 



It is not consistent with the object of this work to enter into the details of pyro- 

 techny, which may be found in many works, Gray's Op. Chemist ; Cutbush, in Am. 

 Jour. Vol. VIII. p. 118, &c. The following may be taken as examples of prepa- 

 rations for rockets. 



Powder for rockets. 



Rockets of one or two ounces 8 parts gunpowder, 1 fine soft charcoal. 



Somewhat larger 10 ounces gunpowder, 3 saltpetre, 3 charcoal. 



Of five or six ounces weight 37 ounces gunpowder, 8 saltpetre, 2 sulphur, 6 

 charcoal, 2 iron filings. 



Ten to twelve ounces weight 17 ounces gunpowder, 4 saltpetre, 3 sulphur, 

 1 charcoal. 



One pound weight 16 ounces gunpowder, 1 sulphur, 3 charcoal. 



Four to seven pounds weight 31 saltpetre, 4 sulphur, 10 charcoal. 



Still larger 8 pounds saltpetre, 1| sulphur, 2| charcoal. 



The contents of a Congreve rocket, analysed by Gay Lussac, were in the propor- 

 tion of 720 nitre, 16 charcoal and 234 sulphur. A rocket made upon this result had 

 the same properties with the English. 



