Dr. R. Hare on the Explosiveness of Nitre, 531 



with a sledge. An explosion will ensue, with a very loud re- 

 port. Of course the operator's face should be protected by 

 a mask, his hands and legs by a leathern or woollen apron 

 and gloves. The operation may be performed by one person, 

 but more advantageously by two, as it is difficult for one to 

 hold the iron in the position most suitable for bringing the 

 surfaces together with the requisite degree of parallelism. 



13. In a letter in reply to one from Mr. Durant, of New 

 York, respecting the explosions which are the principal ob- 

 jects of these communications, I adverted to the superiority 

 of the affinity which exists between water and oxide of potas- 

 sium over that which exists between nitric acid and the same 

 base*, as a reason why the presence of the elements of water, 



* It may be well here to advert to the fact, that one of our young 

 countrymen, Tilghman, has, without any hint from me, not only perceived 

 the property of water on which I have insisted, but likewise has had the 

 sagacity to suggest its application to various useful processes. These have 

 all been founded on that superior affinity of water for certain bases, on 

 which, in my letter to Hayes, I had insisted as affording the rationale of the 

 explosion of nitre either with this liquid, or with any substance containing 

 its elements. 



From the preceding suggestions, and some experiments, of which an 

 account will be subjoined, it appears that the explosive violence of a mix- 

 ture of nitre with substances containing carbon in union with hydrogen, or 

 with hydrogen and oxygen, so as to be competent to convert the base into 

 a hydrate or carbonate, is dependent on the force with which they may be 

 held or brought together in a state of ignition, being sufficient to permit of 

 that increase of temperature which is necessary to explosive reaction. 



Probably at the temperature thus alluded to, the ingredients are all in a 

 condition analogous to that of a very dense explosive gaseous mixture. It 

 is well known that such mixtures detonate with a velocity apparently not 

 less than that of an electrical discharge. A single electrical spark, a particle 

 of platina sponge, even a sunbeam, may cause an explosion so instantaneous, 

 that it is the collapse only that can be observed. The dilatation which 

 precedes the collapse escapes scrutiny. However large the volume, igni- 

 tion in any one part seems to affect the whole at once. 



I infer, then, that when nitre and certain compounds of carbon with 

 hydrogen and oxygen reach a temperature at which the whole mixture, if 

 not restrained mechanically, would take the aeriform state by a sudden 

 revolution in the electro-chemical polarities, that detonating combination 

 ensues, to which, when ignited, various gaseous mixtures are liable. A few 

 cubic inches of olefiant gas, with twice the bulk of oxygen, included in 

 soap-bubbles and inflamed, will produce a report equal to that of a musket. 

 The accidental explosion of a half-gallon of a similar mixture created a 

 thundering noise like a field-piece, so as to alarm the whole neighbourhood 

 within a furlong of my laboratory. 



Aware of the influence of confinement in augmenting the force of reac- 

 tion between nitre and combustibles, the distinguished chemists above 

 mentioned (as having been called upon by the Corporation of New York 

 to investigate the phaenomena under consideration) treated the absence 

 of this condition as a reason for discrediting the idea that the reaction of 

 nitre with combustibles could account for them. But agreeably to the 



2 M 2 



