ANXUAL OF SCIENTIFIC DISCOVERY. 



passage of an electric spark through it, or in the latter case the rays 

 of the sun, produce instantaneous combination throughout the whole 

 volume of gas. A violent explosion takes place, and the vessel is 

 shattered into innumerable minute fragments, in consequence of the 

 enormous force suddenly exerted by the intensely heated product of 

 combination of the gases. 



These are one or two instances in which combination produces 

 explosion. We can produce a much greater variety of examples in 

 which explosion is the result of the instantaneous or very rapid 

 decomposition of a chemical compound. We are acquainted with sev- 

 eral classes of compounds remarkably unstable in their character, 

 these are to be found particularly among the bodies which we term 

 organic ; there are, however, a few inorganic compounds which are 

 also remarkable for their instability ; such are the combinations of 

 hydrogen and nitrogen with chlorine, bromine, and iodine. This, for 

 instance, is the iodide of nitrogen, which is formed whenever iodine 

 and ammonia are brought together. If it is sufficiently dry, a very 

 slight touch will cause the explosion. The combinations of mercury 

 and of silver with* carbon, nitrogen, and oxygen, which we know as 

 the fulminates, are remarkably explosive in their character. When 

 these fulminates, are perfectly dry, a very slight blow or a very small 

 amount of friction is sufficient to bring about their decomposition. 

 Thus, here is a small quantity of fulminate of mercury; you will 

 observe that a very slight application of heat to this is sufficient to 

 cause it to undergo decomposition. It inflames with a dull sort of 

 sound, which would, of course, be rendered more violent if the parti- 

 cles were confined. Here is some fulminate of silver, which is much 

 more explosive in its character. We will take a much smaller por- 

 tion of this than of the other fulminate, and place it upon the cop- 

 per, and submit it to the action of the heat. [This was done.] You 

 see it explodes much more readily and violently, and we perforate 

 the copper instantly; while in the case of the mercury compound 

 the copper was hardly indented. As I have said, the explosive char- 

 acters are exhibited by various organic compounds bodies not of 

 natural occurrence, but produced from non-explosive organic sub- 

 stances by the action of an acid remarkable for the amount of oxy- 

 gen which it contains, and for the tendency which it has to impart 

 that oxygen to other substances nitric acid. This nitric acid, as 

 many of you know, may be made to produce changes in organic sub- 

 stances, resulting in the oxidation of a proportion of hydrogen-atoms 

 in the organic structure, and their removal in the form of water ; a 

 corresponding proportion of the partially de-oxidized acid (nitrous 

 acid) passing into the space created by the abstraction of the hydro- 

 gen from the group; and thus we can produce, for example, from 

 cotton, from cellulose, or lignine, highly explosive substances. 



There is also an explosive substance produced by a similar action 

 of nitric acid upon the sweet principle of manna, beet-root, parsnips, 

 or onions, known as mannite ; it is nitromannite. Again, we are 

 enabled by the mere contact of nitric acid, in its most concentrated 

 form, at a low temperature, with glycerine, to produce a substance 

 of a highly explosive character known as nitroglycerine or glonolne. 

 It is only necessary to moisten a small portion of filtering-paper with 



