Improvements in the Manufacture of Explosive Compounds.
Year: 1897

page_text: Date of Application, 29th June, 1897-Accepted, 31st July, 1897
COMPLETE SPECIFICATION.
1. Improvements in the Manufacture of Explosive Compounds.
I, HUDSON MAXIM, of Thurlow Lodge, 377 Norwood Road, in the County of
Surrey, Chemist and Mechanical Engineer, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
The object of this invention is mainly to provide, at a minimum of expense in
manufacture, a smokeless explosive compound or powder for guns of all calibres,
which shall consist chielly or wholly of pyroxylin, and which sliall, at the same
time, produce very high ballistic results.
Heretofore, great difficulty has been experienced in the use of smokeless
explosives composed wholly of pyroxylin for guns of large calibres, on account of
'the density of a colloid of guncotton and the small extent to which the flame of
combustion will consume the explosive material under admissible pressure and
during the very short time that elapses before the projectile leaves the gun. This
has made it difficult to use such explosive material in pieces of the requisite
dimensions or thickness to enable sufficiently large charges to be employed. Con-
sequently it has been necessary to employ a thinner body of the explosive material
in order that it may be completely burned through and wholly consumed, and thus
too large a combustion area, relative to the weight of the charge, is presented to
the initial flame of combustion, with resulting excessive pressures.
Another disadvantage experienced in making smokeless explosives wholly of
pyroxylin has been due to the quantity of solvents necessary, and to the difficulty
with which the solvents can lie evaporated from the explosive material unless the
latter be made in very thin sheets or pieces, and in addition to this disadvantage,
a further difficulty arises in the warping, twisting and breaking of the sheets or
pieces of explosive material, such warping, twisting and breaking being due to
the more rapid evaporation of the solvent from the surfaces of the explosive body
and the consequent shrinkage of such surfaces before the solvent has evaporated
from its deeper portions.
In carrying out my invention I first make a paper or paper board of pyroxylin
of the highest degree of nitration, that is to say, tri-nitro-cellulose. This is then
sized or impregnated with a size preferably consisting mainly of a more soluble
variety of pyroxylin than the tri-nitro-cellulose, the said soluble pyroxylin being
dissolved in a suitable solvent that is not a solvent of the tri-nitro-cellulose. Such
a solvent, for example, as wood alcohol, or a mixture of ether and alcohol, is very
suitable for this purpose. The kind of pyroxylin used for making the size pre-
ferably of the character employed for making pyroxylin varnish. After being
sized, and when it is desired to produce a body of explosive material of a thickness
greater than that of the paper, any desired number of such sheets may be placed
one upon another and the whole be subjected to pressure, whereby the said sheets
are caused to adhere firmly and solidly together. The sheets or masses of the
material are then multi-perforated and cut into any suitable shape for use in
guns, after which the volatile solvent or solvents employed are evaporated. The
final product consists of an impervious mass of fibrous pyroxylin, agglutinated by a

page_text: colloid of the pyroxylin of the size, which fills all the pores and interstices and
covers all the pyroxylin fibres. I prefer to employ in the size a considerable excess
of neutralizer, such, for example, as urea. This produces an explosive compound
of exceptional stability.
The hardness and density of the explosive body may be varied as desired by
varying the consistence of the size and the quantity of it applied, and by varying
the amount of pressure applied to the mass.
According to another modification of my invention, I use a size consisting of
soluble pyroxylin and nitro-glycerin, preferably in about equal proportions by
weight, dissolved in wood alcohol or other suitable solvent. I do not confine
myself to a pyroxyline size; I sometimes employ other materials, such, for example,
as are usually employed in the manufacture of some fine papers, and with or
without nitro-glycerin, and I find it advantageous in some instances to incor-
porate with the size a quantity of an oxygen-bearing-salt, such, for example, as
nitrate of barium.
As there need only be employed a quantity of nitrate of barium equal to about
fifteen to twenty per cent. of the weight of the other solids used in the size, and as
only about fifteen per cent. to twenty per cent. of the weight of the final product
will consist of the solids of the size, there will therefore appear in the final product
only about 2 per cent. of nitrate of barium, which is too small a percentage to
be objectionable as a smoke-producer.
In order to confine more exclusively combustion to and within the perforations,
and thereby secure the maximum of increase of burning area as the powder
becomes consumed, I prefer to apply to the external surfaces of the body of the
powder-material, a coating or layer of a material of a less explosive or less com-
bustible character than that of the main body of the powder, which serves to
retard the ignition of the explosive body where applied, so that ignition there takes
place later than within the perforations. This coating may be applied either
before or after making the perforations, but preferably before.
ав
There are different substances, of varying efficiency, which will serve
deterrents or retarding agents to initial combustion, and which may be employed
for the purpose. For example, I may employ a coating of commercial non-
explosive celluloid, or of a non-combustible mineral compound, or a coating of
paper made from un-nitrated cellulose, and impregnated with a size made of non-
explosive material, with which has been preferably combined a considerable
percentage of urea. I may, of course, employ for the coating a compound con-
sisting mainly of the same material as the main body of the powder, but always a
large percentage ought to be added to the coating.
I have found that, when urea, in percentages ranging from four per cent. upwards
is employed in a smokeless powder, ignition is very much retarded, as urea in
combustion absorbs heat instead of giving out heat like many other organic bodies.
Urea has the further advantage in a smokeless powder, that it reduces the tempera-
ture of the products of combustion in the gun, as well as being the best neutralizer
that can be employed to secure the stability of the powder.
A further advantage of an impervious coating applied to a smokeless powder
compound of the character described, especially one containing a percentage of
urea, is that the interior portions of the body are better protected from any
external conditions which might effect the stability of the compound.
I do not confine myself to any particular character of coating or to the coating
of powder grains of any particular shape, as the invention may be applied to
powder made in cylindrical rod form, the same as British Cordite, as well as to
powders made in rectangular form, or otherwise. Nor do I confine myself to any
particular coating material, as such may be made of any suitable ignition-retarding
agent.
When employing powder in the form of long rectangular strips approximating
the length of the powder-chamber in the gun, and it is desired to prevent such
strips from too closely touching one another, the air-spacing of the powder-charge

page_text: may be more evenly dispersed through the charge by making the strips slightly
waved or corrugated.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed; I declare that what I
claim is :-
1. The process of making an explosive compound of the character described,
which consists in making a paper of tri-nitro-cellulose, sizing the paper, and
subjecting the same to pressure.
2. The process of making an explosive compound, consisting in making a paper
of tri-nitro-cellulose, and impregnating the paper with a solution of a more soluble
variety of pyroxylin in a solvent which is not a solvent of the tri-nitro-cellulose.
3. The process of making an explosive compound, consisting in making a paper
of tri-nitro-cellulose, and impregnating the paper with a solution of a more soluble
variety of pyroxylin and nitro-glycerin, in a solvent which is not a solvent of tne
tri-nitro-cellulose.
4. The herein described process of manufacturing an explosive compound, which
consists in superimposing layers of pyroxylin paper one upon another, solidly
uniting them, then applying a coating of a more slowly burning or less explosive
material than the main body of the compound, and then multi-perforating the
explosive body.
5. The herein described process of manufacturing an explosive compound, which
consists in making pyroxylin into paper, and then impregnating the same with a
size containing nitrate of barium or other oxygen-bearing salts.
6. The herein described process of manufacturing an explosive compound, which
consists in making pyroxylin into paper, uniting together superimposed sheets of
the paper, and then coating the same with a substance containing a larger per-
centage of urea or other neutraliser than the main body of the explosive material.
7. A body of explosive compound consisting of a number of superimposed layers
of pyroxylin paper.
8. A body of explosive compound consisting of a number of superimposed layers
of pyroxylin paper, and one or more layers of un-nitrated paper, applied to the
exterior.
D. YOUNG & Co.;
11 & 12 Southampton Buildings, London, W.C., Agents for the Applicant.