584 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[J anuary 23, 187 3. 
have "been inevitable. The immunity enjoyed by gun¬ 
cotton is due to its being wet, and therefore absolutely 
uninflammable, throughout all stages, even after it has 
been compressed into cakes or disks. At this point it 
contains 15 per cent, of water, the expulsion of which 
by desiccation is unattended by any liability to explo¬ 
sion, or even to ignition if very simple precautions are 
adopted. . For storing large quantities with absolute 
safety it is very convenient to preserve the compressed 
gun-cotton damp, as it is delivered from the presses. It 
has been thus stored for very long periods without the 
slightest detriment, and its non-inflammability in this 
condition is aptly illustrated by the fact that the perfo¬ 
rations required in some of the charges are produced by 
drilling the damp gun-cotton, the drill revolving at the 
rate of about 600 revolutions per minute. The gun¬ 
cotton employed in some extensive experiments recently 
made on the South Coast had been stored damp for 
nearly nine months, and was dried partly in the open air 
and partly in a hot-air chamber, when required for use. 
On that occasion 6 cwt. of damp gun-cotton, packed in 
twenty-four strong wooden boxes, were stacked in a 
wooden shed and surrounded by inflammable material. 
The building was then fired, and soon burned fiercely, 
which it continued to do for about half-an hour, when 
the fire gradually subsided, and the building and its 
contents were entirely consumed. The gun-cotton must 
have slowly burned away as the surfaces of the masses 
became sufficiently dry, but at no period of the experi¬ 
ment was there even any burst of flame, due to rapid 
ignition, perceptible. 
Another very important consideration connected with 
the extensive employment of an explosive compound or 
mixture as a substitute for gunpowder is the question of 
its stability. Mixtures of saltpetre or potassium chlo¬ 
rate, with oxidizable substances of stable character, may 
be generally relied upon to equal gunpowder in their 
unalterable nature, under all conditions of storage and 
use in different climates; deterioration in explosive 
power by the absorption of moisture is the only preju¬ 
dicial result which generally attends long-continued 
keeping of such mixtures. There are a few instances, 
however, in which absorption of moisture may in time 
establish slight chemical action between the compo¬ 
nents, and thus become, not only cause of more serious 
determination, but also a source of danger ; as chemical 
activity, once started in preparations of this kind, may 
gradually increase, being promoted by the heat de¬ 
veloped, until it attains a violence resulting in the 
spontaneous ignition or explosion of the mass. 
Instances are on record of the spontaneous explo¬ 
sion from this cause of damp mixtures, well known 
to be perfectly stable when dry. Substances of organic 
origin, of uncertain stability, require application with 
much greater caution to the production of explosive 
mixtures, as it is possible that changes may occur spon¬ 
taneously in them, or may be established by natural at¬ 
mospheric fluctuations of temperature, eventually giving 
rise to chemical action between them and the oxidizing 
agent with which they are mixed. Although the sta¬ 
bility of compounds , which are themselves endowed with 
explosive properties, may appear perfectly reliable when 
the substance is in a chemically pure condition, it is sus¬ 
ceptible of being seriously affected by comparatively 
minute causes; hence the most scrupulous care in the 
production and purification of such substances is impe¬ 
ratively necessary; and in this respect they compare 
disadvantageous^ with gunpowder, as a want of care 
in its production, though it may lead to accident during 
manufacture, or to an inferiority of the product, will not 
affect the stability of the material. 
Both nitro-glycerine and gun-cotton, when prepared 
in small quantities and carefully purified, have been 
long known by chemists to be subject to very gradual 
chemical change when exposed frequently to sunlight, 
and also to be liable to slow or rapid decomposition if 
exposed to temperatures very considerably higher than 
occur as extremes under natural conditions in any cli¬ 
mate. Both substances are also well known to have 
exhibited great stability under normal conditions of 
preservation, and even when continually exposed to 
light; but though many specimens exist, which have 
remained unaltered almost since the first discovery of 
these bodies a quarter of a century ago, the instances 
are numerous in which laboratory specimens have un¬ 
dergone spontaneous change, with more or less rapidity. 
The apparently variable nature of these substances, as 
regards stability, is due to the retention by them, in 
some instances, of small quantities of comparatively un¬ 
stable impurities, derived from foreign matters con¬ 
tained in the cellulose or glycerine; exposure to heat 
or to sunlig-ht developes changes in these, resulting in 
the production of acid substances ; hence, if they exist 
in gun-cotton or nitro-glycerine, they may consti¬ 
tute the starting-point of [decomposition when these 
arc exposed to high temperatures or to the influence of 
sunlight. If they exist in gun-cotton, they will be, to 
some extent, enclosed in the hollow fibres, and are then 
only removed effectually by breaking up the latter, and 
long-continued washing. In nitro-glycerine, they are 
held obstinately dissolved by the liquid, and their re¬ 
moval can also only be effectually accomplished by a 
long-protracted washing of the very finely-divided sub¬ 
stance.. Alkaline agents are in both cases useful in ac¬ 
celerating purification. 
For many years nitro-glycerine was universally re¬ 
garded as specially liable to spontaneous change; even 
samples of different quantities of several pounds each, 
which, within. the last four years, were produced at 
Woolwich in immediately successive operations, all ap¬ 
parently under the same conditions and with the special 
object in view of obtaining a thoroughly purified and 
stable material, have exhibited great differences in their 
keeping qualities. They have all been preserved in the 
dark, side by side; some are now in their originally pure 
condition, others have become more or less strongly 
acid, and two or three have undergone complete meta¬ 
morphosis into oxalic acid and other products. The 
manufacturing and purifying processes, as perfected by 
Mr. Nobel, appear to furnish more reliably uniform 
products than those usually obtained on a small scale, 
and such specimens of these products as the lecturer has 
had an opportunity to examine have exhibited great 
stability. Yet, if it were possible to trace explosions to 
their cause more frequently than is the case, an accidental 
want of stability might perhaps have been found, in some 
instances, at any rate, auxiliary in bringing about the 
violent nitro-glycerine explosions which have occurred. 
It has, however, been already established by very ex¬ 
tensive experience during the last three years that nitro¬ 
glycerine is . a far more reliable material than was 
formerly believed, and that if the most scrupulous at¬ 
tention is paid to its purification, and is combined with 
vigilance during storage and use of its preparations, and 
the adoption of certain precautions, which have already 
been proved important safeguards against chemical 
change in materials of this class, the risk of accident is 
so greatly reduced as to warrant the extensive manu¬ 
facture and employment of nitro-glycerine preparations 
under restrictions similar to such as may be deemed 
sufficient in the case of other explosive agents. 
The causes which led to the great uncertainty with 
regard, to stability exhibited by gun-cotton, as manufac¬ 
tured in the earlier days of its history, have been dis¬ 
cussed in former discourses. The very extensive experi¬ 
ments and observations which were set on foot nine 
years ago by the Government Committee, and have been 
continued to this day, on the keeping qualities of gun¬ 
cotton prepared by the Austrian process, have furnished 
most satisfactory results. Very considerable quantities 
of gun-cotton, in a great variety of forms, have been 
stored at Woolwich for several years, and their periodi- 
