[1] The composition of the cellulose nitrates was reviewed by G.
Lunge (_Jour. Amer. Chem. Soc._, 1901, 23, p. 527), who, assuming the
formula C24H40O20 for cellulose, showed how the nitrocelluloses
described by different chemists may be expressed by the formula
C24H_(46-x)O20(NO2)_x, where x has the values 4, 5, 6, ... 12.
[2] This formula is retained mainly on account of its simplicity. It
also expresses all that is necessary in this connexion.
[3] Air-dried guncotton will contain 2% or less of moisture.
GUNDULICH, IVAN (1588-1638), known also as Giovanni Gondola, Servian
poet, was born at Ragusa on the 8th of January 1588. His father, Franco
Gundulich, once the Ragusan envoy to Constantinople and councillor of
the republic, gave him an excellent education. He studied the
"humanities" with the Jesuit, Father Muzzi, and philosophy with Father
Ricasoli. After that he studied Roman law and jurisprudence in general.
He was member of the Lower Council and once served as the chief
magistrate of the republic. He died on the 8th of December 1638. A born
poet, he admired much the Italian poets of his time, from whom he made
many translations into Servian. It is believed that he so translated
Tasso's _Gerusalemme liberata_. He is known to have written eighteen
works, of which eleven were dramas, but of these only three have been
fully preserved, others having perished during the great earthquake and
fire in 1667. Most of those dramas were translations from the Italian,
and were played, seemingly with great success, by the amateurs furnished
by the noble families of Ragusa. But his greatest and justly celebrated
work is an epic, entitled _Osman_, in twenty cantos. It is the first
political epic on the Eastern Question, glorifying the victory of the
Poles over Turks and Tatars in the campaign of 1621, and encouraging a
league of the Christian nations, under the guidance of Vladislaus, the
king of Poland, for the purpose of driving away the Turks from Europe.
The fourteenth and fifteenth cantos are lost. It is generally believed
that the Ragusan government suppressed them from consideration for the
Sultan, the protector of the republic, those two cantos having been
violently anti-Turkish.
_Osman_ was printed for the first time in Ragusa in 1826, the two
missing cantos being replaced by songs written by Pietro Sorgo (or
Sorkochevich). From this edition the learned Italian, Francesco
Appendini, made an Italian translation published in 1827. Since that
time several other editions have been made. The best are considered to
be the edition of the South Slavonic Academy in Agram (1877) and the
edition published in Semlin (1889) by Professor Yovan Boshkovich. In
the edition of 1844 (Agram) the last cantos, fourteen and fifteen,
were replaced by very fine compositions of the Serbo-Croatian poet,
Mazhuranich (Mazuranic). The complete works of Gundulich have been
published in Agram, 1847, by V. Babukich and by the South Slavonic
Academy of Agram in 1889. (C. Mi.)
GUNG'L, JOSEF (1810-1889), Hungarian composer and conductor, was born on
the 1st of December 1810, at Zsambek, in Hungary. After starting life as
a school-teacher, and learning the elements of music from Ofen, the
school-choirmaster, he became first oboist at Graz, and, at twenty-five,
bandmaster of the 4th regiment of Austrian artillery. His first
composition, a Hungarian march, written in 1836, attracted some notice,
and in 1843 he was able to establish an orchestra in Berlin. With this
band he travelled far, even (in 1849) to America. It is worth recording
that Mendelssohn's complete _Midsummer Night's Dream_ music is said to
have been first played by Gung'l's band. In 1853 he became bandmaster to
the 23rd Infantry Regiment at Brunn, but in 1864 he lived at Munich, and
in 1876 at Frankfort, after (in 1873) having conducted with great
success a series of promenade concerts at Covent Garden, London. From
Frankfort Gung'l went to Weimar to live with his daughter, a well-known
German opera singer and local prima donna. There he died, on the 31st of
January 1889. Gung'l's dances number over 300, perhaps the most popular
being the "Amoretten," "Hydropaten," "Casino," "Dreams on the Ocean"
waltzes; "In Stiller Mitternacht" polka, and "Blue Violets" mazurka. His
Hungarian march was transcribed by Liszt. His music is characterized by
the same easy flowing melodies and well-marked rhythm that distinguish
the dances of Strauss, to whom alone he can be ranked second in this
kind of composition.
GUNNER, or MASTER GUNNER, in the navy, the warrant officer who has
charge of the ordnance and ammunition, and of the training of the men at
gun drill. His functions in this respect are of less relative importance
than they were in former times, when specially trained corps of seamen
gunners had not been formed.
GUNNING, PETER (1614-1684), English divine, was born at Hoo, in Kent,
and educated at the King's School, Canterbury, and Clare College,
Cambridge, where he became a fellow in 1633. Having taken orders, he
advocated the royalist cause from the pulpit with much eloquence. In
1644 he retired to Oxford, and held a chaplaincy at New College until
the city surrendered to the parliamentary forces in 1646. Subsequently
he was chaplain, first to the royalist Sir Robert Shirley of Eatington
(1629-1656), and then at the Exeter House chapel. After the Restoration
in 1660 he returned to Clare College as master, and was appointed Lady
Margaret professor of divinity. He also received the livings of
Cottesmore, Rutlandshire, and Stoke Bruerne, Northamptonshire. In 1661
he became head of St John's College, Cambridge, and was elected Regius
professor of divinity. He was consecrated bishop of Chichester in 1669,
and was translated to the see of Ely in 1674-1675. Holding moderate
religious views, he deprecated alike the extremes represented by
Puritanism and Roman Catholicism.
His works are chiefly reports of his disputations, such as that which
appears in the _Scisme Unmask't_ (Paris, 1658), in which the
definition of a schism is discussed with two Romanist opponents.
GUNNY, a sort of cloth, the name of which is supposed to be derived from
_ganga_ or _gania_ of Rumphius, or from _gonia_, a vernacular name of
the _Crotolaria juncea_--a plant common in Madras. One of the first
notices of the term itself is to be found in Knox's _Ceylon_, in which
he says: "The filaments at the bottom of the stem (coir from the
coco-nut husk, _Cocos nucifera_) may be made into a coarse cloth called
gunny, which is used for bags and similar purposes."
Warden, in _The Linen Trade_, says:
"A very large proportion of the jute grown in Bengal is made into
cloth in the districts where it is cultivated, and this industry forms
the grand domestic manufacture of all the populous eastern districts
of Bengal. It pervades all classes, and penetrates into every
household, almost every one, man, woman and child, being in some way
engaged in it. Boatmen, husbandmen, palankeen carriers, domestic
servants, everyone, in fact, being Hindu--for Mussulmans spin cotton
only--pass their leisure moments, distaff in hand, spinning gunny
twist. It is spun by the takur and dhara, the former being a kind of
spindle, which is turned upon the thigh or the sole of the foot, and
the latter a reel, on which the thread, when sufficiently twisted, is
wound up. Another kind of spinning machine, called a ghurghurea, is
occasionally used. A bunch of the raw material is hung up in every
farmer's house, or on the protruding stick of a thatched roof, and
every one who has leisure forms with these spindles some coarse
pack-thread, of which ropes are twisted for the use of the farm. The
lower Hindu castes, from this pack-thread, spin a finer thread for
being made into cloth, and, there being a loom in nearly every house,
very much of it is woven by the women of the lower class of people. It
is especially the employment of the Hindu widow, as it enables her to
earn her bread without being a burden on her family. The cloth thus
made is of various qualities, such as clothing for the family
(especially the women, a great proportion of whom on all the eastern
frontier wear almost nothing else), coarse fabrics, bedding, rice and
sugar bags, sacking, pack-sheet, &c. Much of it is woven into short
lengths and very narrow widths, two or three of which are sometimes
sewed into one piece before they are sold. That intended for rice and
sugar bags is made about 6 feet long, and from 24 to 27 inches wide,
and doubled. A considerable quantity of jute yarn is dyed and woven
into cloth for various local purposes, and some of it is also sent out
of the district. The principal places where chotee, or jute cloth for
gunny bags, is made are within a radius of perhaps 150 to 200 miles
around Dacca, and there both labour and land are remarkably cheap. The
short, staple, common jute is generally consumed in the local
manufacture, the finer and long stapled being reserved for the export
trade. These causes enable gunny cloth and bags to be sold almost as
cheaply as the raw material, which creates an immense demand for them
in nearly every market of the world."
Such appeared to be the definition of gunny cloth at the time the above
was written--between 1850 and 1860. Most of the Indian cloth for gunny
bags is now made by power, and within about 20 m. of Calcutta. In many
respects the term gunny cloth is still applied to all and sundry, but
there is no doubt that the original name was intended for cloth which
was similar to what is now known as "cotton bagging." This particular
type of cloth is still largely made in the hand loom, even in Dundee,
this method of manufacture being considered, for certain reasons, more
satisfactory than the power loom method (see JUTE and BAGGING).
GUNPOWDER, an explosive composed of saltpetre, charcoal and sulphur.
Very few substances have had a greater effect on civilization than
gunpowder. Its employment altered the whole art of war, and its
influence gradually and indirectly permeated and affected the whole
fabric of society. Its direct effect on the arts of peace was but
slight, and had but a limited range, which could not be compared to the
modern extended employment of high explosives for blasting in mining and
engineering work.
It is probably quite incorrect to speak of the _discovery_ of gunpowder.
From modern researches it seems more likely and more just to think of it
as a thing that has developed, passing through many stages--mainly of
improvement, but some undoubtedly retrograde. There really is not
sufficient solid evidence on which to pin down its invention to one man.
As Lieutenant-Colonel H. W. L. Hime (_Gunpowder and Ammunition_, 1904)
says, the invention of gunpowder was impossible until the properties of
nearly pure saltpetre had become known. The honour, however, has been
associated with two names in particular, Berthold Schwartz, a German
monk, and Friar Roger Bacon. Of the former Oscar Guttmann writes
(_Monumenta pulveris pyrii_, 1904, p. 6): "Berthold Schwartz was
generally considered to be the inventor of gunpowder, and only in
England has Roger Bacon's claim been upheld, though there are English
writers who have pleaded in favour of Schwartz. Most writers are agreed
that Schwartz invented the first firearms, and as nothing was known of
an inventor of gunpowder, it was perhaps considered justifiable to give
Schwartz the credit thereof. There is some ambiguity as to when Schwartz
lived. The year 1354 is sometimes mentioned as the date of his invention
of powder, and this is also to be inferred from an inscription on the
monument to him in Freiburg. But considering there can be no doubt as to
the manufacture in England of gunpowder and cannon in 1344, that we have
authentic information of guns in France in 1338 and in Florence in 1326,
and that the Oxford MS. _De officiis regum_ of 1325 gives an
illustration of a gun, Berthold Schwartz must have lived long before
1354 to have been the inventor of gunpowder or guns." In Germany also
there were powder-works at Augsburg in 1340, in Spandau in 1344, and
Liegnitz in 1348.
Roger Bacon, in his _De mirabili potestate artis et naturae_ (1242),
makes the most important communication on the history of gunpowder.
Reference is made to an explosive mixture as known before his time and
employed for "diversion, producing a noise like thunder and flashes like
lightning." In one passage Bacon speaks of saltpetre as a violent
explosive, but there is no doubt that he knew it was not a
self-explosive substance, but only so when mixed with other substances,
as appears from the statement in _De secretis operibus artis et
naturae_, printed at Hamburg in 1618, that "from saltpetre and other
ingredients we are able to make a fire that shall burn at any distance
we please." A great part of his three chapters, 9, 10, 11, long appeared
without meaning until the anagrammatic nature of the sentences was
realized. The words of this anagram are (chap. 11): "Item ponderis totum
30 sed tamen salis petrae _luru vopo vir can utri_[1] et sulphuris; et
sic facies tonitruum et coruscationem, si scias artificium. Videas tamen
utrum loquar aenigmate aut secundum veritatem." Hime, in his chapter on
the origin of gunpowder, discusses these chapters at length, and gives,
omitting the anagram, the translation: "Let the total weight of the
ingredients be 30, however, of saltpetre ... of sulphur; and with such a
mixture you will produce a bright flash and a thundering noise, if you
know the trick. You may find (by actual experiment) whether I am writing
riddles to you or the plain truth." The anagram reads, according to
Hime, "salis petrae r(ecipe) vii part(es), v nov(ellae) corul(i), v et
sulphuris" (take seven parts of saltpetre, five of young hazel-wood, and
five of sulphur). Hime then goes on to show that Bacon was in possession
of an explosive which was a considerable advance on mere incendiary
compositions. Bacon does not appear to have been aware of the projecting
power of gunpowder. He knew that it exploded and that perhaps people
might be blown up or frightened by it; more cannot be said. The
behaviour of small quantities of any explosive is hardly ever indicative
of its behaviour in large quantities and especially when under
confinement. Hime is of opinion that Bacon blundered upon gunpowder
whilst playing with some incendiary composition, such as those mentioned
by Marcus Graecus and others, in which he employed his comparatively
pure saltpetre instead of crude nitrum. It has been suggested that Bacon
derived his knowledge of these fiery mixtures from the MS. _Liber
ignium_, ascribed to Marcus Graecus, in the National Library in Paris
(Dutens, _Enquiry into Origin of Discoveries attributed to Moderns_).
Certainly this Marcus Graecus appears to have known of some incendiary
composition containing the gunpowder ingredients, but it was not
gunpowder. Hime seems to doubt the existence of any such person as
Marcus Graecus, as he says: "The _Liber ignium_ was written from first
to last in the period of literary forgeries and pseudographs ... and we
may reasonably conclude that Marcus Graecus is as unreal as the
imaginary Greek original of the tract which bears his name." Albertus
Magnus in the _De mirabilibus mundi_ repeats some of the receipts given
in Marcus Graecus, and several other writers give receipts for Greek
fire, rockets, &c. Dutens gives many passages in his work, above-named,
from old authors in support of his view that a composition of the nature
of gunpowder was not unknown to the ancients. Hime's elaborate arguments
go to show that these compositions could only have been of the
incendiary type and not real explosives. His arguments seem to hold good
as regards not only the Greeks but also the Arabs, Hindus and Chinese
(see also FIREWORKS).
There seems no doubt that incendiary compositions, some perhaps
containing nitre, mostly, however, simply combustible substances as
sulphur, naphtha, resins, &c., were employed and projected both for
defence and offence, but they were projected or blown by engines and not
by themselves. It is quite inconceivable that a real propelling
explosive should have been known in the time of Alexander or much later,
and not have immediately taken its proper place. In a chapter discussing
this question of explosives amongst the Hindus, Hime says: "It is
needless to enlarge the list of quotations: incendiaries pursued much
the same course in Upper India as in Greece and Arabia." No trustworthy
evidence of an explosive in India is to be found until the 21st of April
1526, the date of the decisive battle of Panipat, in which Ibrahim,
sultan of Delhi, was killed and his army routed by Baber the Mogul, who
possessed both great and small firearms.
As regards also the crusader period (1097-1291), so strange and deadly
an agent of destruction as gunpowder could not possibly have been
employed in the field without the full knowledge of both parties, yet no
historian, Christian or Moslem, alludes to an explosive of any kind,
while all of them carefully record the use of incendiaries. The
employment of rockets and "wildfire" incendiary composition seems
undoubtedly of very old date in India, but the names given to pieces of
artillery under the Mogul conqueror of Hindustan point to a European, or
at least to a Turkish origin, and it is quite certain that Europeans
were retained in the service of Akbar and Aurangzeb. The composition of
present day Chinese gunpowder is almost identical with that employed in
Europe, so that in all probability the knowledge of it was obtained from
Western sources.
In the writings of Bacon there is no mention of guns or the use of
powder as a propellant, but merely as an explosive and destructive
power. Owing perhaps to this obscurity hanging over the early history of
gunpowder, its employment as a propelling agent has been ascribed to the
Moors or Saracens. J. A. Conde (_Historia de la dominacion de los Arabes
en Espana_) states that Ismail Ben Firaz, king of Granada, who in 1325
besieged Boza, had among his machines "some that cast globes of fire,"
but there is not the least evidence that these were guns. The first
trustworthy document relative to the use of gunpowder in Europe, a
document still in existence, and bearing date February 11, 1326, gives
authority to the council of twelve of Florence and others to appoint
persons to superintend the manufacture of cannons of brass and iron
balls, for the defence of the territory, &c., of the republic. John
Barbour, archdeacon of Aberdeen, writing in 1375, states that cannons
(crakys of war) were employed in Edward III.'s invasion of Scotland in
1327. An indenture first published by Sir N. H. Nicolas in his _History
of the Royal Navy_ (London, 1846), and again by Lieutenant-Colonel H.
Brackenbury (_Proc. R.A. Inst._, 1865), stated to be 1338, contains
references to small cannon as among the stores of the Tower, and also
mentions "un petit barrell de gonpoudre le quart' plein." If authentic,
this is possibly the first mention of gunpowder as such in England, but
some doubts have been thrown upon the date of this MS. From a
contemporary document in the National Library in Paris it seems that in
the same year (1338) there existed in the marine arsenal at Rouen an
iron weapon called _pot de feu_, for propelling bolts, together with
some saltpetre and sulphur to make powder for the same. Preserved in the
Record Office in London are trustworthy accounts from the year 1345 of
the purchase of ingredients for making powder, and of the shipping of
cannon to France. In 1346 Edward III. appears to have ordered all
available saltpetre and sulphur to be bought up for him. In the first
year of Richard II. (1377) Thomas Norbury was ordered to buy, amongst
other munitions, sulphur, saltpetre and charcoal, to be sent to the
castle of Brest. In 1414 Henry V. ordered that no gunpowder should be
taken out of the kingdom without special licence, and in the same year
ordered twenty pipes of willow charcoal and other articles for the use
of the guns.
The manufacture of gunpowder seems to have been carried on as a crown
monopoly about the time of Elizabeth, and regulations respecting
gunpowder and nitre were made about 1623 (James I.). Powder-mills were
probably in existence at Waltham Abbey about the middle or towards the
end of the 16th century.
_Ingredients and their Action._--Roger Bacon in his anagram gives the
first real recipe for gunpowder, viz. (according to Hime, ch. xii.)
saltpetre 41.2, charcoal 29.4, sulphur 29.4. Dr John Arderne of
Newark, who began to practise about 1350 and was later surgeon to
Henry IV., gives a recipe (Sloane MSS. 335, 795), saltpetre 66.6,
charcoal 22.2, sulphur 11.1, "which are to be thoroughly mixed on a
marble and then sifted through a cloth." This powder is nominally of
the same composition as one given in a MS. of Marcus Graecus, but the
saltpetre of this formula by Marcus Graecus was undoubtedly answerable
for the difference in behaviour of the two compositions. Roger Bacon
had not only refined and obtained pure nitre, but had appreciated the
importance of thoroughly mixing the components of the powder. Most if
not all the early powder was a "loose" mixture of the three
ingredients, and the most important step in connexion with the
development of gunpowder was undoubtedly the introduction of wet
mixing or "incorporating." Whenever this was done, the improvement in
the product must have been immediately evident. In the damp or wetted
state pressure could be applied with comparative safety during the
mixing. The loose powder mixture came to be called "serpentine"; after
wet mixing it was more or less granulated or corned and was known as
"corned" powder. Corned powder seems to have been gradually
introduced. It is mentioned in the _Fire Book_ of Conrad von Schongau
(in 1429), and was used for hand-guns in England long before 1560. It
would seem that corned powder was used for hand-guns or small arms in
the 15th century, but cannon were not made strong enough to withstand
its explosion for quite another century (Hime). According to the same
writer, in the period 1250-1450, when serpentine only was used, one
powder could differ from another in the proportions of the
ingredients; in the modern period--say 1700-1886--the powders in use
(in each state) differed only as a general rule in the size of the
grain, whilst during the transition period--1450-1700--they generally
differed both in composition and size of grain.
Corned or grained powder was adopted in France in 1525, and in 1540
the French utilized an observation that large-grained powder was the
best for cannon, and restricted the manufacture to three sizes of
grain or corn, possibly of the same composition. Early in the 18th
century two or three sizes of grain and powder of one composition
appear to have become common. The composition of English powder seems
to have settled down to 75 nitre, 15 charcoal, and 10 sulphur,
somewhere about the middle of the 18th century.
The composition of gunpowders used in different countries at different
times is illustrated in the following tables:--
_English Powders (Hime)._
+-----------+------+------+------+------+------+------+--------+
| | 1250.| 1350.| 1560.| 1647.| 1670.| 1742.| 1781. |
+-----------+------+------+------+------+------+------+--------+
| Saltpetre | 41.2 | 66.6 | 50.0 | 66.6 | 71.4 | 75.0 | 75.0 |
| Charcoal | 29.4 | 22.2 | 33.3 | 16.6 | 14.3 | 12.5 | 15.0 |
| Sulphur | 29.4 | 11.1 | 16.6 | 16.6 | 14.3 | 12.5 | 10.0[2]|
+-----------+------+------+------+------+------+------+--------+
_Foreign Powders (Hime)._
+-----------+-------+-------+--------+--------+-------+-------+--------+
| |France.|Sweden.|Germany.|Denmark.|France.|Sweden.|Germany.|
+-----------+-------+-------+--------+--------+-------+-------+--------+
| | 1338. | 1560. | 1595. | 1608. | 1650. | 1697. | 1882. |
+-----------+-------+-------+--------+--------+-------+-------+--------+
| Saltpetre | 50 | 66.6 | 52.2 | 68.3 | 75.6 | 73 | 78 |
| Charcoal | ? | 16.6 | 26.1 | 23.2 | 13.6 | 17 | 19 |
| Sulphur | 25 | 16.6 | 21.7 | 8.5 | 10.8 | 10 | 3[3] |
+-----------+-------+-------+--------+--------+-------+-------+--------+
When reasonably pure, none of the ingredients of gunpowder absorbs any
material quantity of moisture from the atmosphere, and the nitre only
is a soluble substance. It seems extremely probable that for a long
period the three substances were simply mixed dry, indeed sometimes
kept separate and mixed just before being required; the consequence
must have been that, with every care as to weighing out, the
proportions of any given quantity would alter on carriage. Saltpetre
is considerably heavier than sulphur or charcoal, and would tend to
separate out towards the bottom of the containing vessel if subjected
to jolting or vibration. When pure there can only be one kind of
saltpetre or sulphur, because they are chemical individuals, but
charcoal is not. Its composition, rate of burning, &c., depend not
only on the nature of the woody material from which it is made, but
quite as much on the temperature and time of heating employed in the
making. The woods from which it is made contain carbon, hydrogen and
oxygen, and the two latter are never thoroughly expelled in
charcoal-making. If they were, the resulting substance would be of no
use for gunpowder. 1-3% of hydrogen and 8-15% of oxygen generally
remain in charcoals suitable for gunpowder. A good deal of the
fieriness and violence of explosion of a gunpowder depends on the mode
of burning of the charcoal as well as on the wood from which it is
made.
_Properties of Ingredients._--Charcoal is the chief combustible in
powder. It must burn freely, leaving as little ash or residue as
possible; it must be friable, and grind into a non-gritty powder. The
sources from which powder charcoal is made are dogwood (_Rhamnus
frangula_), willow (_Salix alba_), and alder (_Betula alnus_). Dogwood
is mainly used for small-arm powders. Powders made from dogwood
charcoal burn more rapidly than those from willow, &c. The wood after
cutting is stripped of bark and allowed to season for two or three
years. It is then picked to uniform size and charred in cylindrical
iron cases or slips, which can be introduced into slightly larger
cylinders set in a furnace. The slips are provided with openings for
the escape of gases. The rate of heating as well as the absolute
temperature attained have an effect on the product, a slow rate of
heating yielding more charcoal, and a high temperature reducing the
hydrogen and oxygen in the final product. When heated for seven hours
to about 800 deg. C. to 900 deg. C. the remaining hydrogen and oxygen
amount to about 2% and 12% respectively. The time of charring is as a
rule from 5 to 7 hours. The slips are then removed from the furnace
and placed in a larger iron vessel, where they are kept comparatively
air-tight until quite cold. The charcoal is then sorted, and stored
for some time before grinding. The charcoal is ground, and the powder
sifted on a rotating reel or cylinder of fine mesh copper-wire gauze.
The sifted powder is again stored for some time before use in closed
iron vessels.
Sicilian sulphur is most generally employed for gunpowder, and for
complete purification is first distilled and then melted and cast into
moulds. It is afterwards ground into a fine powder and sifted as in
the case of the charcoal.
Potassium nitrate is eminently suitable as an oxygen-provider, not
being deliquescent. Nitrates are continually being produced in surface
soils, &c., by the oxidation of nitrogenous substances. Nitric and
nitrous acids are also produced by electric discharges through the
atmosphere, and these are found eventually as nitrates in soils, &c.
Nitre is soluble in water, and much more so in hot than in cold. Crude
nitre, obtained from soils or other sources, is purified by
recrystallization. The crude material is dissolved almost to
saturation in boiling water: on filtering and then cooling this liquor
to about 30 deg. C. almost pure nitre crystallizes out, most of the
usual impurities still remaining in solution. By rapidly cooling and
agitating the nitre solution crystals are obtained of sufficient
fineness for the manufacture of powder without special grinding. Nitre
contains nearly 48% of oxygen by weight, five-sixths of which is
available for combustion purposes. Nearly all the gases of the powder
explosion are derived from the nitre. The specific gravity of nitre is
2.2 : 200 grams will therefore occupy about 100 cubic centimetres
volume. This quantity on its decomposition by heat alone yields 28
grams or 22,400 c.c. of nitrogen, and 80 grams or 56,000 c.c. of
oxygen as gases, and 94 grams of potassium oxide, a fusible solid
which vaporizes at a very high temperature.
_Incorporation._--The materials are weighed out separately, mixed by
passing through a sieve, and then uniformly moistened with a certain
quantity of water, whilst on the bed of the incorporating mill. This
consists of two heavy iron wheels mounted so as to run in a circular
bed. The incorporation requires about four hours. The mechanical
action of rollers on the powder paste is a double one: not only
crushing but mixing by pushing forwards and twisting sideways. The
pasty mass is deflected so that it repeatedly comes under first one
roller and then the next by scrapers, set at an angle to the bed,
which follow each wheel.
Although the charge is wet it is possible for it to be fired either by
the heat developed by the roller friction, by sparks from foreign
matters, as bits of stone, &c., or possibly by heat generated by
oxidation of the materials. The mills are provided with a drenching
apparatus so arranged that in case of one mill firing it and its
neighbours will be drowned by water from a cistern or tank immediately
above the mill. The product from the incorporation is termed
"mill-cake."
After this incorporation in the damp state the ingredients never
completely separate on drying, however much shaken, because each
particle of nitre is surrounded by a thin layer of water containing
nitre in solution in which the particles of charcoal and sulphur are
entangled and retained. After due incorporation, powders are pressed
to a certain extent whilst still moist. The density to which a powder
is pressed is an important matter in regard to the rate of burning.
The effect of high density is to slow down the initial rate of
burning. Less dense powders burn more rapidly from the first and tend
to put a great strain on the gun. Fouling is usually less with denser
powders; and, as would be expected, such powders bear transport better
and give less dust than light powders. Up to a certain pressure,
hardness, density, and size of grain of a powder have an effect on the
rate of burning and therefore on pressure. Glazing or polishing powder
grains, also exerts a slight retarding action on burning and enables
the powders to resist atmospheric moisture better. Excess of moisture
in gunpowder has a marked effect in reducing the explosiveness. All
powders are liable to absorb moisture, the quality and kind of
charcoal being the main determinant in this respect; hard burnt black
charcoal is least absorbent. The material employed in brown powders
absorbs moisture somewhat readily. Powder kept in a very damp
atmosphere, and especially in a changeable one, spoils rapidly, the
saltpetre coming to the surface in solution and then crystallizing
out. The pieces also break up owing to the formation of large crystals
of nitre in the mass. After the pressing of the incorporated powder
into a "press-cake," it is broken up or granulated by suitable
machines, and the resulting grains separated and sorted by sifting
through sieves of determined sizes of mesh. Some dust is formed in
this operation, which is sifted away and again worked up under the
rollers (for sizes of grains see fig. 1). These grains, cubes, &c.,
are then either polished by rotating in drums alone or with graphite,
which adheres to and coats the surfaces of the grains. This process is
generally followed with powders intended for small-arms or moderately
small ordnance.
_Shaped Powders._--Prisms or prismatic powder are made by breaking up
the press-cake into a moderately fine state, whilst still moist, and
pressing a certain quantity in a mould. The moulds generally employed
consist of a thick plate of bronze in which are a number of hexagonal
perforations. Accurately fitting plungers are so applied to these that
one can enter at the top and the other at the bottom. The lower
plunger being withdrawn to the bottom of the plate the hexagonal hole
is charged with the powder and the two plungers set in motion, thus
compressing the powder between them. After the desired pressure has
been applied the top plunger is withdrawn, and the lower one pushed
upward to eject the prism of powder. The axial perforations in prism
powders are made by small bronze rods which pass through the lower
plunger and fit into corresponding holes in the upper one. If these
prisms are made by a steadily applied pressure a density throughout of
about 1.78 may be obtained. Further to regulate the rate of burning so
that it shall be slow at first and more rapid as the powder is
consumed, another form of machine was devised, the cam press, in which
the pressure is applied very rapidly to the powder. It receives in
fact one blow, which compresses the powder to the same dimensions, but
the density of the outer layers of substance of the prism is much
greater than in the interior.
The leading idea in connexion with all shaped powder grains, and with
the very large sizes, was to regulate the rate of burning so as to
avoid extreme pressure when first ignited and to keep up the pressure
in the gun as more space was provided in the chamber or tube by the
movement of the shot towards the muzzle. In the perforated prismatic
powder the ignition is intended to proceed through the perforations;
since in a charge the faces of the prisms fit pretty closely together,
it was thought that this arrangement would prevent unburnt cores or
pieces of powder from being blown out. These larger grain powders
necessitated a lengthened bore to take advantage of the slower
production of gases and complete combustion of the powder. General T.
J. Rodman first suggested and employed the perforated cake cartridge
in 1860, the cake having nearly the diameter of the bore and a
thickness of 1 to 2 in. with perforations running parallel with the
gun axis. The burning would then start from the comparatively small
surfaces of the perforations, which would become larger as the powder
burnt away. Experiments bore out this theory perfectly. It was found
that small prisms were more convenient to make than large disks, and
as the prisms practically fit together into a disk the same result was
obtained. This effect of mechanical density on rate of burning is good
only up to a certain pressure, above which the gases are driven
through the densest form of granular material. After granulating or
pressing into shapes, all powders must be dried. This is done by
heating in specially ventilated rooms heated by steam pipes. As a rule
this drying is followed by the finishing or polishing process. Powders
are finally blended, i.e. products from different batches or "makes"
are mixed so that identical proof results are obtained.
_Sizes and Shapes of Powders._--In fig. 1, _a_ to _k_ show the
relative sizes and shapes of grain as formerly employed for military
purposes, except that the three largest powders, _e-f-g_ and _h_ are
figured half-size to save space, whereas the remainder indicate the
actual dimensions of the grains. _a_ is for small-arms, all the others
are for cannon of various sizes.
[Illustration: FIG. 1.]
_Proof of Powder._--In addition to chemical examination powder is
passed through certain mechanical tests:--