134
GUNPOWDER.— Materials.
resulting from the chemical action producing thischange, will at once lead to the conclusion that allmatters incapable of undergoing such a modificationinjure or depreciate, in proportion to their quantity,the quality and efficacy of the product.
Matekials. —The ingredients for the manufactureof gunpowder, says Captain Smith, late assistantsuperintendent , are supplied to the Koyal Factoryat Waltham Abbey in the rough state, and arerefined and prepared for use there ; but in manyprivate factories it is the custom to purchase thesaltpetre and sulphur refined and ready for conver-sion into gunpowder, and charcoal ground or un-ground. A manufacturer who refines his ownsaltpetre and sulphur, and burns his own charcoal,has means of insuring the purity and uniformityof the ingredients which he makes use of, far superiorto that of any system of testing, however careful.The additional security against accidents in thecourse of manufacture, gained by careful exclusionof all foreign matters from the ingredients during theprocess of refining, is of even greater consequence.
The saltpetre used at Waltham Abbey is exclusivelythat imported from India . Various descriptions ofartificial saltpetre—that is, saltpetre made by chemicalprocesses, generally by the action of potassiumchloride on sodium nitrate—have been tried suc-cessfully ; but as there is no economy in employingthe latter, as the natural salt can be refined by asimple process, it has hitherto been preferred. Itcomes principally from Bengal and Oude. In thesecountries it occurs as a white incrustation on thesoil, being also mixed with it to a considerable depth.The earth is scraped up and boiled with water, andthe solution, after being concentrated by the heatof the sun and evaporated by artificial heat, yieldsimpure crystals of the salt, which are packed in bagsof course sacking. In this state the salt is known as“grough saltpetre.”
Before the salt is fit to be used for powder makingthe impurities must be eliminated. The amount ofimpurity present is reckoned per 112 lbs., and ingood samples does not amount to 5 per cent., andseldom exceeds 10. It is known as the “ refraction ’of the nitre, the term being derived from the oldprocess used to ascertain it, viz., by fusing a smallportion into a cake and examining the fracture; ithas nothing to do with the optical properties of thesalt. In the saltpetre market 5 per cent, is supposedto be the standard amount of impurity, all trans-actions taking place on that basis, but with theunderstanding that if the amount of impurity begreater, a reduction is to be made in favour of thebuyer, and vice versa.
The following is a copy of three analyses of speci-mens of grough saltpetre :—
Per Cent.
Ter Cent.
Per Cent.
Moisture, .
. 1-60 ....
1-69
... 1-74
Sand,.
. -10 ....
•21 .
... -25
Sulphate of soda,.. .
- ....
•78 .
... 3-21
Chloride of sodium, .
. voo ....
•37 .
... -85
Saltpetre,.
. 97-30 ....
97-05 .
.. 93-95
The process now generally employed for removingthese impurities is a very simple and effective one,
and was first introduced and practised in France. —See Potassium.
The principal saline impurity in saltpetre is sodiumchloride—common salt—which has a very injuriousaction on gunpowder, causing it to absorb moisture,whereby its power is soon considerably weakened.Saltpetre containing more than a P art
chlorides is rejected as unfit for use.
The sulphur used at Waltham Abbey is importedfrom Sicily . The finest quality, known as Sicarafirsts, is alone employed. As imported the sulphurcontains 3 or 4 per cent, of earthy impurities, havingalready undergone a rough purification by distilla-tion before it comes into the merchant’s hands. Itis finally and carefully purified by a second distilla-tion. Many private factories use the ordinary rollsulphur of commerce, which is simply sulphurmelted and cast into moulds.
Sulphur exists in several distinct conditions orforms, two of which require special notice whenspeaking of it as an ingredient of gunpowder, viz.,the soluble or electro-negative form, and the insolubleor electro-positive. Distilled sulphur consists almostentirely of the former; sublimed sulphur contains alarge proportion of the latter. Distilled sulphur, asused in the manufacture of gunpowder, consists ofmasses of clear yellow crystals in the form of rhom-bic octahedra, and is readily soluble in bisulphide ofcarbon. Sublimed sulphur (known as flowers ofsulphur ) is a pale yellow powder, composed of minuteparticles, which do not present a crystalline structure,but which are merely minute granules consisting ofinsoluble sulphur, inclosing a small portion of thesoluble variety. This latter form of sulphur is to agreat extent insoluble in the bisulphide.
It is generally stated that the reason flowers ofsulphur cannot be used for powder-making is because,having been deposited in a chamber containing aconsiderable amount of sulphurous and sulphuricacid, they are always found to present a decided acidreaction, which would be injurious on the finishedpowder; but Professor Bloxam points out that it ismuch more likely that the properties of the electro-positive or insoluble sulphur, of which they are in agreat measure composed, may exercise an injuriouseffect on the action of gunpowder.
Charcoal .—The woods from which charcoal is nowmanufactured for powder-making appear to havebeen in use from a very early period. Their adop-tion was no doubt decided empirically, but it is. noteasy even now to determine why particular woodsare better adapted for charcoal than others. It isstated that as early as 1414 King Henry V. orderedtwenty pipes of willow charcoal to be prepared foremployment in gunpowder-making.
The only woods now used in the Koyal Gun-powder Factory are the ivillow, the alder, and what ispopularly known as the black dogivood, but which isreally the alder buckthorn, or berry-bearing alder{Rhamnus firmgula). Though various other woodsare used by private makers for coarse blastingpowder, the three woods named are generally usedboth at home and abroad for the best gunpowders.