126 PHILOSOPHY OF 



in a state of intimate mixture. When perfectly 

 dry, and heat is applied, the nitre is decomposed 

 into its original constituents, with a tremendous 

 force of explosion, which is owing principally to 

 the elastic force of the nitrogen, on being released 

 from its combination with the oxygen and potass 

 of the nitre. During this rapid process, 2 atoms 

 of oxygen combine with 1 of sulphur, making sul- 

 phurous acid gas ; while the other 3 atoms of 

 oxygen that existed in the nitric acid, combine 

 with 3 atoms of charcoal, forming carbonic oxide 

 and carbonic acid. But as the elastic force of 

 these gases is comparatively low, the explosive 

 action must depend chiefly on the sudden ex- 

 pansion of nitrogen on assuming the gaseous 

 state. The whole is nothing but an instanta- 

 neous combustion of sulphur and charcoal, ac- 

 companied by the disengagement of heat and 

 light, as in ordinary combustion, and by the sud- 

 den liberation of nitrogen, which, in the separate 

 state, exerts an elastic force equal to a pressure 

 of 16800 Ibs. to the square inch. The force is 

 also greatly increased by the caloric given out 

 during the formation of carbonic oxide and car- 

 bonic acid, the quantity of which is by no means 

 inconsiderable. 



This is a most instructive exemplification of the 

 law by which caloric exerts two opposite forces, 

 the one or the other prevailing according to 

 circumstances. At ordinary temperatures, the 

 particles of nitre, sulphur, and charcoal, retain 



