It is a generation since a dictionary of explosives has been
published, and, in the meantime, many new explosives have been
introduced. It is hoped, therefore, that this small volume, giving
concise information about these special materials, may prove useful
to those who have to deal with them. In Cundill and Thomson’s
“Dictionary of Explosives,” issued in 1895, there are many entries of
the names of inventors and of mixtures which had been proposed but
have never been used commercially, nor are likely to be. As modern
explosives were then in their infancy, it was no doubt wise to insert
all the available information whether it appeared to be important
or not; but now it seems to me better to restrict the scope of the
dictionary so as to keep its size within moderate limits. Practically
only explosives with special or proprietary names are therefore dealt
with here. For information concerning chemical substances, such as
the nitro-toluenes and other nitro-compounds, reference should be
made to the textbooks on explosives and chemistry.
A few words may, however, be said here about the nitrocelluloses.
These are made by treating cellulose with a mixture of nitric
and sulphuric acids, and then purifying the product by washing
it thoroughly with hot water. The variety of cellulose most used
for this purpose is cotton, and the product obtained from it is
frequently called nitrocotton, three special varieties of which are
collodion cotton, pyrocollodion and guncotton (_q. v._). The only
other form of cellulose which is nitrated on a commercial scale is
“chemical cellulose” obtained by the treatment of wood or straw.
Nitrated wood cellulose has long been used for the manufacture of
smokeless powders for shot-guns, and during the War the Germans made
powders for rifled fire-arms from it.
No trouble has been spared to make the dictionary complete and
accurate, but there must inevitably be omissions and errors in it,
especially as regards the explosives of foreign countries. The author
will be grateful for any additional information that may be sent him.
Explosives may be classified in various ways, according to the
purpose of the classification, but the great majority of them fall
naturally into two main divisions: propellants and high explosives.
Propellants explode comparatively slowly, and are used to propel
projectiles from fire-arms. High explosives are much more rapid in
their action, and are used for bursting and shattering. Propellants
are of two sorts, according as they are intended for use in shot-guns
or rifled fire-arms. Those for shot-guns burn more rapidly than those
for the latter, but both practically always contain a considerable
proportion of nitrocellulose, gelatinised by means of such solvents
as acetone or ether-alcohol, according as it is of high or low
nitration. Some contain also nitroglycerine, and are then called
nitroglycerine powders, whereas those that do not contain this
substance are termed nitrocellulose powders. Many powders also
contain other ingredients, as may be seen from the compositions given
in this dictionary.
Of high explosives an important class is used for charging shells
and bombs. As a rule, but not necessarily, these are not the same
as the explosives used for mining operations and other general
blasting purposes. Another important class is that of the coal-mine
explosives, which are designed to give only a short and comparatively
cool flame so as to diminish the danger of igniting fire-damp
and coal-dust. Nearly half the explosives in this dictionary are
coal-mine explosives. The reason for this large number is that no
finality has yet been reached as to the best and safest explosives
to use in coal mines. When more experience has been gained it is
probable that the number of these explosives on the market will
be reduced. In England the Permitted List has recently been cut down
considerably.
In Great Britain these coal-mine explosives have to be submitted
to the Inspectors of Explosives, and are subjected to tests for
safety and strength. If they pass they are placed on the list of
“Permitted Explosives,” and the compositions are published in the
Explosives in Coal Mines Orders. In these Orders the upper and lower
limits of the percentage of each constituent are given, but in this
dictionary intermediate percentages are given so that the sum for any
explosive amounts to 100. In the Explosives in Coal Mines Orders the
percentage of such a substance as wood, meal or starch, is given in
the dried condition, but here it is given in the air-dry state on the
assumption that it then contains about 10 per cent. of moisture.
In France and Belgium also the compositions of the coal-mine
explosives are published, but in Germany, as a rule, only a list of
the constituents is given, and sometimes an upper or lower limit for
one or more of the principal constituents. Moreover, it is not stated
explicitly whether the explosives are intended for use in coal mines
or for general blasting purposes. In the United States of America,
explosives intended for use in coal mines are examined by the Bureau
of Mines, which, however, has no power to prevent the use of others
because regulations on this matter are made by the individual states.
If they pass they are placed on the list of “Permissible Explosives.”
The compositions are not published, but the class of composition is
stated.
Until the second half of the nineteenth century, gunpowder was
practically the only explosive used on a considerable scale, and it
was employed for all purposes. Consequently it does not fall into any
of the classes mentioned, or rather it could be placed in several of
them.
Another class of explosives that has not yet been mentioned is that
of the primary igniters, of which fulminate of mercury may be taken
as typical. The characteristic of these is that they can be exploded
or ignited by a spark or moderate friction, and consequently they
can be employed to fire other, less sensitive explosives. There
are, however, practically no explosives of this class which possess
special or proprietary names, and consequently they are not dealt
with in this dictionary.
_Naini Tal, India._
1920.