100 Dr. J, H. Gladstone [May 4, 



In so doing he glanced first, in a cursory manner, at the various 

 kinds of explosives with which chemists are acquainted. Any great 

 and sudden increase of volume may give rise to the phenomena 

 designated explosion ; but such great and sudden increase never 

 takes place by the mere dilatation of a solid or liquid body : it is 

 always necessary that gases should be formed. The simplest form 

 of explosion is when a liquid is suddenly converted into a gas either 

 by the removal of pressure, or by the bursting of the vessel in which 

 it was contained, as illustrated by the common " candle-cracker." 

 The enormous expansion of a gas by the removal of pressure is 

 taken advantage of for the projection of missiles in the air-gun, 

 and in Perkins's steam-gun. In these cases there is no chemical 

 change ; but usually an explosion is the result of a rapid chemical 

 action between the different constituents of a mixture, or chemical 

 compound, by which substances are produced that occupy a very 

 much larger space than the original combination did. Such an 

 explosion is always attended with heat, and generally with light and 

 noise. The substance exploded may be a mixture of two or more 

 gases : for instance, if the fire-damp of the mines be set fire to in 

 the air, it burns quietly with a luminous flame ; if, however, it be 

 previously mixed with air, on being ignited the flame passes instantly 

 throughout the whole mass ; and if mixed with twice its volume of 

 oxygen, this takes place with great violence, and a loud report. 

 One atom of the carburetted hydrogen combines with four atoms 

 of oxygen, to form carbonic acid and water. In this case, however, 

 the gases produced by the explosion would actually have occupied 

 less space than the original mixed gases, and a positive contraction 

 would have ensued, had it not been for the high temperature at 

 which they were formed. In order to obtain very great expansion 

 we must not start with a gaseous mixture. Solid or liquid oxygen 

 is a desideratum, but it can be procured in that condition only when 

 in a state of combination. There are several salts which contain a 

 large quantity of this element, and which give it up with great facility 

 — the nitrates and chlorates of potash or soda, for instance ; and these 

 salts contain also another element, which when free assumes a gaseous 

 condition, even at ordinary temperatures. 



Dr. Gladstone then proceeded to show the violent combustion 

 that ensued when wood was thrown into one of these salts in a fused 

 condition, and to demonstrate the still greater effects that resulted 

 when the salt and the combustible had been previously mixed. He 

 then rapidly described the manufacture of gunpowder from nitre, 

 charcoal, and sulphur, and the different proportions of the three 

 ingredients that are employed in different countries. In exploding, 

 gunpowder produces carbonic acid and nitrogen gases, and sulphuret 

 of potassium, which is also dissipated by the great heat evolved, and 

 if it reach the air is converted into sulphate of potash, giving rise 

 to the white smoke that follows the explosion. Beside these gases 

 some others are always produced in small and varying quantity^ 



