GUNPOWDER.— Materials. Charcoal.
185
1. Willow .—The particular species of willow whichfinds most favour at Waltham Abbey is the whiteDutch (Salix alba ). This is one of the softest andlightest of English woods. It is of very rapid growth,a section of the wood showing wide and well-markedrings of annual increase. The wood is nearly white,and has a tolerably large circular white pith. Themore rapidly the wood has been grown the less densewill it be, and the better for powder-making whenconverted into charcoal. For this reason woodgrown in England is preferred to that grown abroad,the foreign wood, both alder and willow, beingfound to be closer in the grain.
2. Alder .—The common alder (Alnus glutinosa ),though supposed to be of exactly equal merit withthe willow, is considerably harder and denser intexture, and is not of such rapid growth. Thecolour of the wood is reddish-yellow; the pith istriangular in section, resembling in shape the sectionof a bayonet.
3. The Blaclc Dogwood (for it has been so longknown to powder makers by this name that it maybe as well to adhere to it) is a handsome underwoodof very slow growth, and is found in thickets inmany parts of the south of England, and in Scot-land . The name dogwood has been derived fromits berries resembling those of some of the dogwoodsproper.
Though the Rhamnus has been misnamed, there isno confusion about the wood itself. It is undoubt-edly the Rhamnus frangula , which has found suchfavour with powder-makers both at home and abroad.Though the wood is found in many parts of GreatBritain , the main source of supply is the Continent.The wood is dense and tough, the annual rings being-very close together. The pith is circular and red-dish in colour, occasionally bright red. This colouris preserved even after the charcoal is burned.
Small wood of about ten years’ growth is in allcases preferred for powder making. Alder andwillow of this age is 4 or 5 inches in diameter, dog-wood about 1. Great stress is always laid on everytrace of bark being removed before conversion ofthe wood into charcoal. The wood is cut in thespring when the sap is rising. Wood cut later inthe year, or in winter, is perfectly as good; but theremoval of the bark is a much more difficult matter.To separate it the wood must be boiled, or if thatbe impracticable, the whole of the bark must beshaved off with a knife or spokeshave.
The temperature at which the charring of thewood is conducted, and its uniformity, are of thehio-hest importance for the chemical composition ofthe charcoal, and the temperature at which it willignite is undoubtedly affected by the temperature atwhich it has been charred. Charcoal prepared at alow temperature is softer, more inflammable, andcontains more gaseous elements than charcoal pre-pared at a greater heat, and the gunpowders madefrom these charcoals would be similarly affected. Itis hopeless, therefore, to attempt to obtain uniformresults in manufacturing powder unless means betaken to insure uniformity in the preparation of |
charcoal. At most foreign gunpowder manufac-tories pyrometers to ascertain the temperature ofthe cylinders are in use; but in England the pro-cess is intrusted to the experience and careful watch-ing of the foreman. Charcoal, if properly made,should be jet black in colour; its fracture shouldshow a clear, velvet-like surface, and it should belight and sonorous when dropped on a hard surface.Underbnrnt charcoal, that is, charcoal prepared ata very low temperature, is at once known by itsreddish-brown colour, overburnt charcoal by itshardness and density. Two considerations, there-fore, must not be overlooked in choosing a propercharcoal—namely, the nature of the wood, and themanner in which the carbonization of the same isconducted; and each demands the utmost circum-spection in the manufacturer who is desirous ofproducing an article which will yield the greatestpossible amount of force, and combine at the sametime the quality of inflaming readily, as well as thatof leaving the least quantity of residuary matter afterits ignition.
Underburnt charcoal has found favour amongstprivate makers in this country and in France forsome small-arm powders. It certainly renders thepowder more inflammable, and consequently quicker;but it has the disadvantage of being more hygroscopicthan denser charcoal. The powder is therefore moreliable to suffer damage from damp. Some experi-ments made at Waltham Abbey with two field-gunpowders, in all respects identical except the burningof the charcoal, showed that that made with under-burnt charcoal gave CO feet more velocity to a 12lbs. shot than that made with the ordinary blackcharcoal.
The following analyses of charcoals made at theRoyal Gunpowder Factory show that they do notvary much in chemical construction or physical
qualities: —
Ash.
Carbon.
Hydrogen.
Oxygen,with trace of
Per Cent.
Per Cent.
Per Cent.
Nitrogen.Per Cent.
Alder.
. 1-24
87-00
2-97
9*78
Willow,..
. 2-02
85-82
2-88
9*28
Dogwood, ....
. 1-71
83-80
3-28
11-21
The charcoals from three different specimens ofgunpowder (L.G., R.L.G., and Pellet) manu-factured at Waltham Abbey in different years, whenanalyzed showed a very close agreement in com-position
Oxygen,
Ash. Carbon. Hydrogen, with trace ofN itrogen.
Ter Cent. Per Cent. Per Cent. Per Cent.
L.G.,. 1-61 85-79 2-81 9-76
R.L.G.,. 2-02 85-82 2-88 9-28
Pellet. 2-14 85-80 2-96 9-1
Alder,.... 1-37
Willow,. 1-39
Dogwood,. 1-30
Two points are observable in the charcoal of dogwood,namely, the low density and the amount of gases it