18 G
GUNPOWDER.— Materials. Charcoal.
contains. It is probably due to these two circum-stances that its combustion is more rapid.
The woods now used in most gunpowder factorieswere probably selected centuries ago from actualexperiment, .being found to make stronger powderthan any others. Even in the time of MagnusGrjecus, as already mentioned in the precedinghistorical notice, the charcoal of willow-wood waspreferred, and experience has fully proved that thecharcoal of the soft woods always produces the bestresults. The hard woods are invariably rejected.
Wood which contains carbonate of potassium orother deliquescent salts is unfit for the purpose, andfor obvious causes. This is the case in the oak, elm,fir, and other trees. But there is another reason forthe badness of these kinds of charcoal, which is notso obvious, although it is evidently connected withtheir hardness. It appears to depend on the smallproportion of hydrogen combined with the carbonin these charcoals, compared to that which exists inthe produce of the softer woods. Even these canbe reduced to the same state by subjecting them tohigher temperatures. Thus the hydrogen is dissi-pated, the charcoal becoming so hard as to scratchsteel; in which case, however obtained, it is unfitfor gunpowder.
To test the quality of charcoal J. Louis Proust uses the following simple means:—He makes amixture of 12 grains of the charcoal and 62 ofnitrate of potassium by careful grinding in a mortar,and then introduces it on a small tray into a coppertube 21 inches in length by 3 lines in diameter ; heprimes on the top of this with a little fowling powder,and when this is done, the lower part of the tube isfitted in a dish of cork, or other light material, whichis floated on the surface of water. It is evident fromthese arrangements, analogous as they are to thoseunder which the powder is inflamed, that the mixturewhich burns the more readily is that which is mostsuited to the manufacture. By experiments conductedin this way, and with all the precautions availableunder the circumstances, Proust obtained thefollowing results:—
Mixture of sixty-two Time of the Weight of
grains of Saltpetre and Combustion Residue in
From hemp or hemp hush,.... 10
“ stalks of asphodel,...... 10
“ vine branches,. 12
“ pea stalks,. 13
“ pine,. 17
“ boardaine,. 20
“ spindle-tree,. 21
“ hazel. 23
44 maize canes,. 25
“ chestnut-tree. 26
4 4 walnut-tree,. 29
44 maize,. 55
“ coal-coke,. 50
sugar,. 70
12
12
20
21
30
24
27
30
38
36
33
43
45
48
When submitted to the same operation, lie foundthat the charcoal produced from starch, wheat, rice,gall-nuts, indigo, gluten, gelatin, albumen, blood, andskin, and, in fact, those derived from all animalmatters, would not undergo combustion.
From the foregoing table it is evident that thosewhich precede the charcoal from hazelwood rise in
the scale of superior fitness, whilst those beneath thelatter evidently descend, and are not well adaptedfor the manufacture.
Other experiments upon the same subject, found-ing the comparison of the different charcoals uponthe volume of gas which they yielded when ignitedwith saltpetre, have been conducted by French andBritish chemists, and the results are tabulated below.In each case the proportions used by the former were60 grains of nitrate of potassium to 12 of charcoal; butin the latter the calculations are made to correspondwith the same standard:—
Charcoal.
Proportion of Gasiu Cubic Inches.
_ 62 .
Residueiu Grains.
... 12... 20
... 64 .
... 20
_ 62 .
... 21
66 .
... 28
_ 66 .
... 30
_ 66 .
... 86
66 .
... 33
_ 54 .
... 44
_ 54 .
... 45
“ filbert,.
.... 72 .
... 30
Much of the interest which might otherwise betaken in the foregoing results of the French chemistsis lost, on account of the subjects being not likelyever to enter practically, at least to any extent, intothe manufacture under consideration. Below aregiven results arrived at in England, by operatingupon the more frequently occurring woods:—•
Proportion of Gas.
Filbert,. 72
Oak,. 61-63
Mahogany,. 58
Elm,. 62
Alder,. 74-73
Dogwood —ffliamnus fravgula .. 80-82-84
Oak bark. 58
Animal charcoal,. 50-46-42-10
Coke,. 52-48
Lamp-black,. 54-52
Oak charcoal overheated,.:. 54-56
Willow charcoal overheated,.. 59-64-66
Tomlinson attributes much of the difference in thelatter table to the method in which the charcoal isprepared, rather than to the substance itself, since heconsiders that to overheat the matter in its carboniza-tion is injurious to its power of combustion. This isevidenced by the results which the modified charcoalfrom oak and willow afforded; and, in fact, severalresearches have led to the acknowledgment of thesame fact. Yiolette has shown that the most com-bustible charcoal loses this quality in proportion asthe heat applied in the carbonization is raised, tillultimately, when the charring is made at the fusingpoint of platinum, the product obtained is so incom-bustible as to be ignited with difficulty even whenthe heat is 2282°. During his researches upon thecarbonization of wood and the application of charcoal,he examined with considerable skill and acuteness thevarious products which most of the ordinary woodsafford by charring, in reference to their combusti-bility in air, and the temperature of their ignitionaccording to the heat applied in their manufacture,and also with regard to the same kind of charcoal