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more rapid change in the mass of the substance, so that eventually 
decomposition of violent nature may be established, and the principal 
portion of the compound may suddenly undergo the same transforma¬ 
tion into gases or vapours, attended by the same development of heat, 
as though any one of the agencies (i.e., fire, friction, or percussion) 
ordinarily employed to determine the explosion of these bodies had 
been applied. Cases of so-called spontaneous explosion thus brought 
about are more familiar to scientific and manufacturing chemists than 
to the general public; but accidental explosions of very alarming and, 
in a few instances, of very calamitous character are on record which, 
though not actually of spontaneous nature, in the strict application of 
the term, have been brought about without any apparent application of 
external inciting agencies, and have hence, from a practical point of 
view, not been incorrectly classed as spontaneous explosions. 
A few substances, well known to chemists, are so very unstable in 
character, or are so very difficult to prepare in a condition approaching 
purity, that they either begin to undergo change as soon as they have 
been produced, or very shortly afterwards; such change proceeding 
sometimes gradually and quietly until the substance has been trans¬ 
formed into non-explosive bodies, or occurring, in other instances, with 
a rapidity speedily resulting in the violent decomposition or explosion 
of the substance. Injuries more or less severe have been inflicted upon 
the discoverers or investigators of substances of this kind, or upon 
those who prepare them and exhibit their properties for instructional 
purposes; and such accidents occasionally occur, even though all pos¬ 
sible or reasonable precautions appear to have been taken to guard 
against them. It has occasionally also happened that serious accidents 
have resulted from attempts to apply to practical purposes the explosive 
power of such substances (as, for example, the chloride of nitrogen and 
iodide of nitrogen), by persons imperfectly acquainted with their pro¬ 
perties or those of explosive substances generally. The great danger 
in which want of knowledge may involve experimenters in this direction 
is too obvious to need being dwelt upon.* 
* The great danger incurred in. experimenting with, or attempting the manufacture upon a 
large scale of, substances of unstable and explosive nature the properties of which are imperfectly 
understood, has been exemplified by repeated accidents with a liquid called methylic nitrate, the 
vapour of which is highly explosive. In 1872, a young English chemist of great promise lost his 
life by a very violent explosion which occurred in a laboratory in Germany, where he had been 
engaged in preparing large quantities of this substance with a view to its employment as a sub¬ 
stitute for nitroglycerine preparations. No conjecture could be formed of the immediate cause of 
the explosion. Some time after, a German manufacturing chemist of eminence lost the sight of 
one eye by the violent explosion of a very small quantity of the same substance while he was 
heating it in a glass tube; and in November last a very violent explosion occurred at the works of 
a manufactory of dyes at St. Denis, in a building where very considerable quantities of the methylic 
nitrate were being prepared and purified for colour-making purposes. Two men were killed, and 
a number seriously injured. In this case the accident was clearly traced to an act of recklessness 
of one of the workmen. The use of lights was prohibited in the building where the purification of 
the substance was carried on, in consequence of the inflammable vapour evolved and the danger of 
explosion from its ignition ; but on this occasion a man not only brought a lamp into the room, but 
actually lowered it into a large boiler from which the liquid was being decanted with a siphon—his 
object being to see how much remained. The vapour in the boiler was at once fired, and a violent 
explosion occurred almost immediately, followed by a second—there being upwards of 1000 lb. of 
the material in an adjoining store. 
