About 1540 the Spaniards constructed a larger and heavier firearm
(matchlock), carrying a ball of 10 to the pound, called a musket. This
weapon was introduced into England before the middle of the 16th
century, and soon came into general use throughout Europe. The snaphance
was invented about this period in Germany, and from its comparative
cheapness was much used in England, France and Holland. It held a flint
instead of the pyrites of the wheel or firelock, which ignited the
powder in the pan by striking on a piece of furrowed steel, when
released by the trigger, and emitting sparks.
As a sporting weapon the gun may be said to date from the invention of
the wheel-lock in the beginning of the 16th century, though firearms
were used for sporting purposes in Italy, Spain, Germany, and to some
extent in France, in the 15th century. Before that period the longbow in
England and the crossbow on the Continent were the usual weapons of the
chase. In Great Britain little use appears to have been made of firearms
for game shooting until the latter half of the 17th century, and the
arms then used for the purpose were entirely of foreign make.
The French gunmakers of St-Etienne claim for their town that it is the
oldest centre of the firearms industry. They do not appear to have made
more than the barrels of the finest sporting arms, and these even were
sometimes made in Paris. The production of firearms by the artists of
Paris reached its zenith about the middle of the 17th century. The
Italian, German, Spanish and Russian gunsmiths also showed great skill
in the elegance and design of their firearms, the Spaniards in
particular being makers of fine barrels. The pistol (q.v.) is understood
to have been made for the first time about 1540 at Pistoia in Italy.
About 1635 the modern firelock or flint-lock was invented, which only
differed from the snaphance by the cover of the pan forming part of the
furrowed steel struck by the flint. Originally the priming was put into
the pan from a flask containing a fine-grained powder called serpentine
powder. Later the top of the cartridge was bitten off and the pan filled
therefrom before loading. The mechanism of the flint-lock musket
rendered all this unnecessary, as, in loading, a portion of the charge
passed through the vent into the pan, where it was held by the cover or
hammer. The matchlock, as a military weapon, gradually gave way to the
firelock, which came into general use in the last half of the 17th
century, and was the weapon of Marlborough's and Wellington's armies.
This was the famous "Brown Bess" of the British army. The highest
development of the flint-lock is found in the fowling-pieces of the end
of the 18th and beginning of the 19th centuries, particularly those made
by Joseph Manton, the celebrated English gunsmith and inventor. The
Napoleonic wars afforded English gunmakers an opportunity, which they
fully utilized, of gaining the supremacy over their foreign competitors
in the gunmaking trade. English gunmakers reduced the weight, improved
the shooting powers, and perfected the lock mechanism of the sporting
gun, and increased the range and efficiency of the rifle. This
transference of the gunmaking craft from the Continent to England was
also assisted by the tyranny of the foreign gunmaking gilds. In 1637 the
London gunmakers obtained their charter of incorporation. The important
gunmaking industry of Birmingham dates from 1603, and soon rivalled that
of London. Double shot-guns do not appear to have been generally used
until the 19th century. The first successful double guns were built with
the barrels over and under, and not side by side, and were invented
about 1616 by one Guilliano Bossi of Rome. In 1784 double shot guns were
described as a novelty. Joseph Manton patented the elevated rib which
rested on the barrels. The general success of the double gun was
eventually due to the light weight which the better material and
workmanship of the best gunmakers made possible, and to the quickness
and certainty of ignition of the modern cartridge.
[Illustration: FIG. 6.--Moorish Flint-lock.]
[Illustration: FIG. 7.--Indian Matchlock.]
The objections to the flint-lock were that it did not entirely preserve
the priming from wet, and that the flint sparks sometimes failed to
ignite the charge. In 1807 the Rev. Alexander John Forsyth obtained a
patent for priming with a fulminating powder made of chlorate of potash,
sulphur and charcoal, which exploded by concussion. This important
improvement in firearms was not recognized and adopted by the military
authorities until more than thirty years later. In the meantime it was
gradually developed, and the copper percussion cap invented, by various
gunmakers and private individuals. Thomas Shaw of Philadelphia first
used fulminate in a steel cap in 1814, which he changed to a copper cap
in 1816. It was not until the introduction of the copper cap that the
percussion gun could be considered in every way superior to the flint.
In 1834, in the reign of William IV., Forsyth's invention was tested at
Woolwich by firing 6000 rounds from six flint-lock muskets, and a
similar number from six percussion muskets, in all weathers. This trial
established the percussion principle. The shooting was found to be more
accurate, the recoil less, the charge of powder having been reduced from
6 to 4-1/2 drs., the rapidity of firing greater and the number of
miss-fires much reduced, being as 1 to 26 nearly in favour of the
percussion system. In consequence of this successful trial the military
flint-lock in 1839 was altered to suit the percussion principle. This
was easily accomplished by replacing the hammer and pan by a nipple with
a hole through its centre to the vent or touch-hole, and by replacing
the cock which held the flint by a smaller cock or hammer with a hollow
to fit on the nipple when released by the trigger. On the nipple was
placed the copper cap containing the detonating composition, now made of
three parts of chlorate of potash, two of fulminate of mercury and one
of powdered glass.
[Illustration: FIG. 8.]
[Illustration: FIG. 9.]
[Illustration: FIG. 10.]
[Illustration: FIG. 11.]
[Illustration: FIG. 12.]
[Illustration: FIG. 13.]
[Illustration: FIG. 14.]
[Illustration: FIG. 15.]
[Illustration: FIG. 16.]
[Illustration: FIG. 17.]
[Illustration: FIG. 18.]
In 1840 the Austrian army was supplied with the percussion musket, and
in 1842 a new model percussion musket with a block or back-sight for 150
yds. was issued to the British army, 11 lb. 6 oz. in weight, 4 ft. 6-3/4
in. in length without bayonet, 6 ft. with bayonet and with a barrel 3
ft. 3 in. in length, firing a bullet of 14-1/2 to the lb. with 4-1/2
drs. of powder. This musket was larger in bore than that of France,
Belgium, Russia and Austria, and thus had the advantage of being able to
fire their balls, while the English balls could not be fired from their
barrels. But the greater weight and momentum of the English ball was
counteracted by the excess of windage. This percussion musket of 1842,
the latest development of the renowned Brown Bess, continued in use in
the British army until partially superseded in 1851 by the Minie rifle,
and altogether by the Enfield rifle in 1855. For further information as
to the history and development of military, target and sporting rifles
see RIFLE.
Illustrations are given herewith of a German carbine of the 16th
century, with double wheel-lock (fig. 8); a snaphance (fig. 9);
several forms of the Brown Bess or flint-lock military musket
(English, William III., fig. 10; George II., fig. 11; George III.,
fig. 12; French, Napoleon, fig. 13); and of the percussion musket
adopted in the British service in 1839 (fig. 14). Examples of
non-European firearms are shown in figs. 6 and 7, representing a
Moorish flint-lock and an Indian matchlock respectively. Figs. 15-18
represent various carbines, musketoons and blunderbusses, fig. 15
showing a small blunderbuss or musketoon of the early 18th century,
fig. 16 a large blunderbuss of 1750, fig. 17 a flint-lock cavalry
carbine of about 1825 and fig. 18 a percussion carbine of 1830. All
these are drawn from arms in the museum of the Royal United Service
Institution, London.
_Modern Shot Guns._--The modern sporting breech-loaders may be said to
have originated with the invention of the cartridge-case containing its
own means of ignition. The breech-loading mechanism antedated the
cartridge by many years, the earliest breech-loading hand guns dating
back to 1537. Another distinct type of breech-loader was invented in
France about the middle of the 17th century. During the 17th and 18th
centuries breech-loading arms were very numerous and of considerable
variety. The original cartridge, a charge of powder and bullet in a
paper envelope, dates from 1586. These were used with muzzle-loaders,
the base of the cartridge being ripped or bitten off by the soldier
before placing in the barrel. It was only when the detonating cap came
into use that the paper cartridge answered well in breech-loaders. The
modern breech-loader has resulted from a gradual series of improvements,
and not from any one great invention. Its essential feature is the
prevention of all escape of gas at the breech when the gun is fired by
means of an expansive cartridge-case containing its own means of
ignition. The earlier breech-loaders were not gas-tight, because the
cartridge-cases were either consumable or the load was placed in a
strong non-expansive breech-plug. The earliest efficient modern
cartridge-case was the pin-fire, patented by Houiller, a Paris gunsmith,
in 1847, with a thin weak shell which expanded by the force of the
explosion, fitted perfectly in the barrel, and thus formed an efficient
gas check. Probably no invention connected with firearms has wrought
such changes in the principle of gun-construction as those effected by
the expansive cartridge-case. This invention has completely
revolutionized the art of gunmaking, has been successfully applied to
all descriptions of firearms, and has produced a new and important
industry--that of cartridge manufacture.
About 1836, C. Lefaucheux, a Paris gunsmith, improved the old Pauly
system of breech-loading, but its breech action was a crude mechanism,
with single grip worked by a bottom lever. The double grip for the
barrels was the subsequent invention of a Birmingham gunmaker. The
central-fire cartridge, practically as now in use, was introduced into
England in 1861 by Daw. It is said to have been the invention of Pottet,
of Paris, improved upon by Schneider, and gave rise to considerable
litigation in respect of its patent rights. Daw, who controlled the
English patents, was the only exhibitor of central-fire guns and
cartridges at the International Exhibition of 1862. In his system the
barrels work on a hinge joint, the bottom lever withdraws the
holding-down bolt; the cartridge is of the modern type, the cap being
detonated by a striker passing through the standing breech to the inner
face. The cartridge-case is withdrawn by a sliding extractor fitted to
the breech ends of the barrels. Daw was subsequently defeated in his
control of the patents by Eley Bros., owing to the patent not having
been kept in force in France. The modern breech-loading gun has been
gradually and steadily improved since 1860. Westley Richards adopted and
improved Matthews' top-lever mechanism. About 1866 the rebounding lock
was introduced, and improved in 1869. The treble wedge-fast mechanism
for holding down the barrels was originated by W. W. Greener in 1865,
and perfected in 1873. A very important improvement was the introduction
of the hammerless gun, in which the mechanism for firing is placed
entirely within the gun. This was made possible by the introduction of
the central-fire cartridge. In 1862 Daw, and in 1866 Green, introduced
hammerless guns in which the cocking was effected by the under lever.
These guns did not attain popularity. In 1871 T. Murcott patented a
hammerless gun, the first to obtain distinct success. This also was a
lever-cocking gun. About the same time Needham introduced the principle
of utilizing the weight of the barrels to assist in cocking. In 1875
Anson and Deeley utilized the fore-end attached to the barrels to cock
the locks. From this date hammerless guns became really popular.
Subsequently minor improvements were made by many other gun-makers,
including alternative movements introduced by Purdey and Rogers.
Improvements were also introduced by Westley Richards, Purdey and
others, including cocking by means of the mainspring. In 1874 J. Needham
introduced the ejector mechanism, by which each empty cartridge-case is
separately and automatically thrown out of the gun when the breech is
opened, the necessary force being provided by the mainspring of the
lock. W. W. Greener and some other gunmakers have since introduced minor
modifications and improvements of this mechanism. Next in turn came
Perks and other inventors, who separated the ejector mechanism from the
lock work. This very decided improvement is universal to-day. A later
innovation in the modern breech-loader is the single trigger mechanism
introduced by some of the leading English gun-makers, by which both
barrels can be fired in succession by a single trigger. This improvement
enables both barrels to be rapidly fired without altering the grip of
the right hand, but deprives the shooter of the power of selecting his
barrel.
Repeating or magazine shot-guns on the principle of the repeating rifle,
with a magazine below the single firing barrel, are also made by some
American and continental gun-makers, but as yet have not come into
general use, being comparatively cumbersome and not well balanced. The
difficulty of a shifting balance as each cartridge is fired has also yet
to be overcome. Several varieties of a combination rifle and shot-gun
are also made, for a description of which see RIFLE.
The chief purposes for which modern shot-guns are required are
game-shooting, trap-shooting at pigeons and wild-fowling. The game gun
may be any bore from 32 to 10 gauge. The usual standard bore is 12 gauge
unless it be for a boy, when it is 20 gauge. The usual weight of the
12-bore double-barrelled game gun is from 6 to 7 lb. with barrels 30 in.
long, there, however, being a present tendency to barrels of a shorter
length. These barrels are made of steel, as being a stronger and more
homogeneous material than the barrels formerly produced, which were
mostly of Damascus pattern, a mixture of iron and steel. Steel barrels,
drilled from the solid block, were originally produced by Whitworth.
To-day the makers of steel for this purpose are many. The standard
charge for the 12-bore is 42 grains of smokeless powder and 1 oz. to
1-1/8th oz. of shot. Powder of a lighter gravimetric density is
occasionally employed, when the weight of the charge is reduced to 33
grains. This charge of powder corresponds to the 3 drams of black powder
formerly used. The ordinary game gun should have a killing circle of 30
in. at 30 yds. with the first barrel and at 40 yds. with the second.
Improved materials and methods of manufacture, and what is known as
"choke" boring of the barrels, have enabled modern gun-makers to
regulate the shooting of guns to a nicety. Choke-boring is the
constriction of the diameter of the barrel near the muzzle, and was
known in America in the early part of the 19th century. In 1875 Pape of
Newcastle was awarded a prize for the invention of choke-boring, there
being no other claimant. The methods of choke-boring have since been
varied and improved by the leading English gun-makers. The pigeon gun is
usually heavier than the game gun and more choked. It generally weighs
from 7 to 8 lb. Its weight, by club rules, is frequently restricted to
7-1/2 lb. and its bore to 12 gauge. The standard wild-fowling gun is a
double 8-bore with 30-in. barrels weighing 15 lb. and firing a charge of
7 drams of powder and 2-3/4 to 3 oz. of shot. These guns are also made in
both smaller and larger varieties, including a single barrel 4-bore,
which is the largest gun that can be used from the shoulder, and single
barrel punt guns of 1-1/2-in. bore, weighing 100 lb. While no conspicuous
advance in improved gun-mechanism and invention has been made during the
last few years, the materials and methods of manufacture, and the
quality and exactitude of the gun-maker's work, have continued gradually
and steadily to improve. English, and particularly London-made, guns
stand pre-eminent all over the world. (H. S.-K.)
GUNA, a town and military station in Central India, in the state of
Gwalior. Pop. (1901) 11,452. After the Mutiny, it became the
headquarters of the Central India Horse, whose commanding officer acts
as ex-officio assistant to the resident of Gwalior; and its trade has
developed rapidly since the opening of a station on a branch of the
Great Indian Peninsula railway in 1899.
GUNCOTTON, an explosive substance produced by the action of strong
nitric acid on cellulose at the ordinary temperature; chemically it is a
nitrate of cellulose, or a mixture of nitrates, according to some
authorities. The first step in the history of guncotton was made by T.
J. Pelouze in 1838, who observed that when paper or cotton was immersed
in cold concentrated nitric acid the materials, though not altered in
physical appearance, became heavier, and after washing and drying were
possessed of self-explosive properties. At the time these products were
thought to be related to the nitrated starch obtained a little
previously by Henri Braconnot and called _xyloidin_; they are only
related in so far as they are nitrates. C. F. Schonbein of Basel
published his discovery of guncotton in 1846 (_Phil. Mag._ [3], 31, p.
7), and this was shortly after followed by investigations by R. R.
Bottger of Frankfort and Otto and Knop, all of whom added to our
knowledge of the subject, the last-named introducing the use of
sulphuric along with nitric acid in the nitration process. The chemical
composition and constitution of guncotton has been studied by a
considerable number of chemists and many divergent views have been put
forward on the subject. W. Crum was probably the first to recognize that
some hydrogen atoms of the cellulose had been replaced by an oxide of
nitrogen, and this view was supported more or less by other workers,
especially Hadow, who appears to have distinctly recognized that at
least three compounds were present, the most violently explosive of
which constituted the main bulk of the product commonly obtained and
known as guncotton. This particular product was insoluble in a mixture
of ether and alcohol, and its composition could be expressed by the term
tri-nitrocellulose. Other products were soluble in the ether-alcohol
mixture: they were less highly nitrated, and constituted the so-called
collodion guncotton.
The smallest empirical formula for cellulose (q.v.) may certainly be
written C6H10O5. How much of the hydrogen and oxygen are in the
hydroxylic (OH) form cannot be absolutely stated, but from the study of
the acetates at least three hydroxyl groups may be assumed. The oldest
and perhaps most reasonable idea represents guncotton as cellulose
trinitrate, but this has been much disputed, and various formulae, some
based on cellulose as C12H20O10, others on a still more complex
molecule, have been proposed. The constitution of guncotton is a
difficult matter to investigate, primarily on account of the very
insoluble nature of cellulose itself, and also from the fact that
comparatively slight variations in the concentration and temperature of
the acids used produce considerable differences in the products. The
nitrates are also very insoluble substances, all the so-called solvents
merely converting them into jelly. No method has yet been devised by
which the molecular weight can be ascertained.[1] The products of the
action of nitric acid on cellulose are not nitro compounds in the sense
that picric acid is, but are nitrates or nitric esters.
Guncotton is made by immersing cleaned and dried cotton waste in a
mixture of strong nitric and sulphuric acids. The relative amounts of
the acids in the mixture and the time of duration of treatment of the
cotton varies somewhat in different works, but the underlying idea is
the same, viz. employing such an excess of sulphuric over nitric that
the latter will be rendered anhydrous or concentrated and maintained as
such in solution in the sulphuric acid, and that the sulphuric acid
shall still be sufficiently strong to absorb and combine with the water
produced during the actual formation of the guncotton. In the recent
methods the cotton remains in contact with the acids for two to four
hours at the ordinary air temperature (15 deg. C.), in which time it is
almost fully nitrated, the main portion, say 90%, having a composition
represented by the formula[2] C6H7O2(NO3)3, the remainder consisting of
lower nitrated products, some oxidation products and traces of unchanged
cellulose and cellulose sulphates. The acid is then slowly run out by an
opening in the bottom of the pan in which the operation is conducted,
and water distributed carefully over its surface displaces it in the
interstices of the cotton, which is finally subjected to a course of
boiling and washing with water. This washing is a most important part of
the process. On its thoroughness depends the removal of small quantities
of products other than the nitrates, for instance, some sulphates and
products from impurities contained in the original cellulose. Cellulose
sulphates are one, and possibly the main, cause of instability in
guncotton, and it is highly desirable that they should be completely
hydrolysed and removed in the washing process. The nitrated product
retains the outward form of the original cellulose. In the course of the
washing, according to a method introduced by Sir F. Abel, the cotton is
ground into a pulp, a process which greatly facilitates the complete
removal of acids, &c. This pulp is finally drained, and is then either
compressed, while still moist, into slabs or blocks when required for
blasting purposes, or it is dried when required for the manufacture of
propellants. Sometimes a small quantity of an alkali (e.g. sodium
carbonate) is added to the final washing water, so that quantities of
this alkaline substance ranging from 0.5% to a little over 1% are
retained by the guncotton. The idea is that any traces of acid not
washed away by the washing process or produced later by a slow
decomposition of the substance will be thereby neutralized and rendered
harmless. Guncotton in an air-dry state, whether in the original form or
after grinding to pulp and compressing, burns with very great rapidity
but does not detonate unless confined.
Immediately after the discovery of guncotton Schonbein proposed its
employment as a substitute for gunpowder, and General von Lenk carried
out a lengthy and laborious series of experiments intending to adapt it
especially for artillery use. All these and many subsequent attempts to
utilize it, either loose or mechanically compressed in any way, signally
failed. However much compressed by mechanical means it is still a porous
mass, and when it is confined as in a gun the flame and hot gases from
the portion first ignited permeate the remainder, generally causing it
actually to detonate, or to burn so rapidly that its action approaches
detonation. The more closely it is confined the greater is the pressure
set up by a small part of the charge burning, and the more completely
will the explosion of the remainder assume the detonating form. The
employment of guncotton as a propellant was possible only after the
discovery that it could be gelatinized or made into a colloid by the
action of so-called solvents, e.g. ethylacetate and other esters,
acetone and a number of like substances (see CORDITE).
When quite dry guncotton is easily detonated by a blow on an anvil or
hard surface. If dry and warm it is much more sensitive to percussion
or friction, and also becomes electrified by friction under those
conditions. The amount of contained moisture exerts a considerable
effect on its sensitiveness. With about 2% of moisture it can still be
detonated on an anvil, but the action is generally confined to the
piece struck. As the quantity of contained water increases it becomes
difficult or even impossible to detonate by an ordinary blow.
Compressed dry guncotton is easily detonated by an initiative
detonator such as mercuric fulminate. Guncotton containing more than
15% of water is uninflammable, may be compressed or worked without
danger and is much more difficult to detonate by a fulminate
detonator than when dry.[3] A small charge of dry guncotton will,
however, detonate the wet material, and this peculiarity is made use
of in the employment of guncotton for blasting purposes. A charge of
compressed wet guncotton may be exploded, even under water, by the
detonation of a small primer of the dry and waterproofed material,
which in turn can be started by a small fulminate detonator. The
explosive wave from the dry guncotton primer is in fact better
responded to by the wet compressed material than the dry, and its
detonation is somewhat sharper than that of the dry. It is not
necessary for the blocks of wet guncotton to be actually in contact if
they be under water, and the peculiar explosive wave can also be
conveyed a little distance by a piece of metal such as a railway rail.
The more nearly the composition of guncotton approaches that
represented by C6H7O2(NO3)3, the more stable is it as regards storing
at ordinary temperatures, and the higher the igniting temperature.
Carefully prepared guncotton after washing with alcohol-ether until
nothing more dissolves may require to be heated to 180-185 deg. C.
before inflaming. Ordinary commercial guncottons, containing from 10
to 15% of lower nitrated products, will ignite as a rule some 20-25
deg. lower.
Assuming the above formula to represent guncotton, there is sufficient
oxygen for internal combustion without any carbon being left. The
gaseous mixture obtained by burning guncotton in a vacuum vessel
contains steam, carbon monoxide, carbon dioxide, nitrogen, nitric
oxide, and methane. When slowly heated in a vacuum vessel until
ignition takes place, some nitrogen dioxide, NO2, is also produced.
When kept for some weeks at a temperature of 100 deg. in steam, a
considerable number of fatty acids, some bases, and glucose-like
substances result. Under different pressures the relative amounts of
the combustion products vary considerably. Under very great pressures
carbon monoxide, steam and nitrogen are the main products, but nitric
oxide never quite disappears.
Dilute mineral acids have little or no action on guncotton. Strong
sulphuric acid in contact with it liberates first nitric acid and
later oxides of nitrogen, leaving a charred residue or a brown
solution according to the quantity of acid. It sometimes fires on
contact with strong sulphuric acid, especially when slightly warmed.
The alkali hydroxides (e.g. sodium hydroxide) will in a solid state
fire it on contact. Strong or weak solutions of these substances also
decompose it, producing some alkali nitrate and nitrite, the cellulose
molecule being only partially restored, some quantity undergoing
oxidation. Ammonia is also active, but not quite in the same manner as
the alkali hydroxides. Dry guncotton heated in ammonia gas detonates
at about 70 deg., and ammonium hydroxide solutions of all strengths
slowly decompose it, yielding somewhat complex products. Alkali
sulphohydrates reduce guncotton, or other nitrated celluloses,
completely to cellulose. The production of the so-called "artificial
silk" depends on this action.
A characteristic difference between guncotton and collodion cotton is
the insolubility of the former in ether or alcohol or a mixture of
these liquids. The so-called collodion cottons are nitrated
celluloses, but of a lower degree of nitration (as a rule) than
guncotton. They are sometimes spoken of as "lower" or "soluble"
cottons or nitrates. The solubility in ether-alcohol may be owing to a
lower degree of nitration, or to the temperature conditions under
which the process of manufacture has been carried on. If guncotton be
correctly represented by the formula C6H7O2(NO3)3, it should contain a
little more than 14% of nitrogen. Guncottons are examined for degree
of nitration by the nitrometer, in which apparatus they are decomposed
by sulphuric acid in contact with mercury, and all the nitrogen is
evolved as nitric oxide, NO, which is measured and the weight of its
contained nitrogen calculated. Ordinary guncottons seldom contain more
than 13% of nitrogen, and in most cases the amount does not exceed
12.5%. Generally speaking, the lower the nitrogen content of a
guncotton, as found by the nitrometer, the higher the percentage of
matters soluble in a mixture of ether-alcohol. These soluble matters
are usually considered as "lower" nitrates.
Guncottons are usually tested by the Abel heat test for stability (see
CORDITE). Another heat test, that of Will, consists in heating a
weighed quantity of the guncotton in a stream of carbon dioxide to
130 deg. C., passing the evolved gases over some red-hot copper, and
finally collecting them over a solution of potassium hydroxide which
retains the carbon dioxide and allows the nitrogen, arising from the
guncotton decomposition, to be measured. This is done at definite time
intervals so that the _rate_ of decomposition can be followed. The
relative stability is then judged by the amount of nitrogen gas
collected in a certain time. Several modifications of this and of the
Abel heat test are also in use. (See EXPLOSIVES.) (W. R. E. H.)