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ed in composition or properties by immersion or even boiling in salt water, insoluble in alcohol, oils, acetic acid, ammonia, weak acid and alkaline solutions-such as solution of carbonate of soda or of potash or lime water. When very well prepared it is entirely soluble in anhydrous sulphuric ether, and the solution when evaporated yields the glass-like paper. If the ether contains alcohol or water the paper is opaque and porous, like ordinary filtering paper.
The cotton thus prepared may be exploded over gun powder without igniting it. It explodes by a violent blow on an anvil with the sharp ring of percussion powder, but the explosion only affects the particles immediately struck, and does not ignite the rest, but if gun powder be mixed with it the whole is fired.
It does not explode by the electric spark, or by the discharge of a single Leyden jar.
It explodes on being heated to 375° of Fahrenheit.
It does not explode by friction between wooden or metallic surfaces till the temperature of these rises to 375°; neither does it explode by compression in powerful screw presses. On the contrary, compression exercises some singular effects on its explosiveness and combustibility. The very most explosive kind twisted into a tight cord burns like quick match, and a tight ligature of wire or twine round a portion of this intercepts the ignition. In the same way when compressed into the touch-hole of a cannon it is fired with the utmost difficulty, so that it cannot be used for priming; accordingly in the ordnance trials at DumDum the cotton charges have been always fired with quick match or powder priming.
Exploded in a loose heap its force appears to be exercised almost altogether in the lines of least resistance; thus on two occasions nearly two pounds weight while being dried on a water-bath exploded accidentally on a thin copper tray, which was not injured or displaced-and on both these occasions the plaster of the roof and the loose tiles of a shed within three feet of the cotton remained undisturbed. A man standing close to the tray was uninjured, and several test glasses ranged on a party wall within 4 feet of the explosion were not moved or broken or their contents spilled.
Regarding the results obtained by my first experiments, in connexion with the valuable properties ascribed by general rumour to the explo
sive cotton, to be of sufficient importance to warrant more extensive trials, I reported them officially to Government, and was immediately directed to prepare a sufficiently large quantity of this cotton for a series of ordnance trials at Dum-Dum. With the valuable assistance of Mr. Frewen of the Mint Assay office, I have accordingly had manufactured over 100 pounds of the explosive cotton, and the experience thus gained regarding its preparation and properties enables me to state such facts as may enable others to form a more correct estimate of the degree of practical value of this preparation, for Military proposes, than can be obtained from experiments on the manufacture and properties of a few ounces of the explosive.
In the experiments carried on at the mint, 100 tola weight (3 and 4th troy pounds) of cotton was operated on at a time, the cotton having been previously cleaned and loosened out by the native bowstring apparatus.
The acid mixture consists of equal measures (in all 336 fluid ounces) of sulphuric acid, Sp. gr. 1843, and nitric acid, Sp. gr. 1460. The sulphuric acid weighs 840 tolas to 21tbs av. and the nitric acid weighs tolas 651
to 17 av. lbs. fractions omitted. The mixture when cool is placed in a large shallow porcelain basin, so situated as to permit the fumes to be carried off by a current of air. The cotton is introduced with iron tongs in small portions at a time, pressed under the surface of the acid for about two minutes and moved to the opposite side of the pan. This is continued till 50 tola weight is introduced. When the last portion has been immersed for about three minutes, the cotton should be lifted out, by the tongs, quickly transferred to a screw-press of iron or stone and the excess of acid pressed out. This is continued till the 50 tola weight is pressed. The cake is then rapidly removed to a large vessel of common water, torn asunder by hand, washed and squeezed and thrown into a second vessel of water; again washed and squeezed, and the masses thrown into a vessel containing a solution of 1 pound of carbonate of soda in 20 gallons of water. Well washed here the mass is placed in a large screw-press-the pressed cake again washed with water. It is now fit for drying, which is best done by solar heat on a dry terrace over tarpaulin or sheets of iron, taking the utmost caution to avoid the possibility of explosion by accidental sparks.
Two days' exposure are sufficient in the month of February, to bring the cotton into as dry state as is required for its use with ordnance or small arms.
Steam or hot water heat may be used for the drying with perfect safety with suitable apparatus. But unless this be in every respect properly constructed, the danger of making a large quantity of cotton is too serious to be trifled with. I have also dried cotton successfully in vacus, and by the immediate contact of masses of quick-lime, but it is needless at present to occupy the pages of this Journal with descriptions of the arrangements, by which these facts can be practically applied.
When dry the cotton is next to be carded; or loosened out by the native bowstring apparatus.
The expressed acid may be used for the remaining 50 tolas of the 100. It will however be generally found that after 40 tolas have been immersed, the acid begins to corrode or pulp the cotton, producing a new series of compounds, chiefly oxalic acid, formic acid, and sugar.
The same series of operations above described is gone through with the second acid, and the resulting cotton kept apart.
After drying, it is found that the 100 tola weight of cotton has increased to 114 to 120, according to the care with which the process has been conducted.
The process thus performed affords two qualities of explosive cotton. The first 50 tolas may be designated 1st or best quality.
The product of the 2d expressed acid and the second 50 tolas of cotton should be marked 3d or worst quality.
If these be mechanically mixed by carding or the bow-string, the mixture may be called 2d quality.
The acid mixture which after cooling was Sp. gr. 1667 before use, after once having been used is of Sp. gr. 1687. Twice used its density is 1691. The acid once used measures 180 fluid ounces and by distillation yields its bulk of nitric acid, Sp. gr. 1480; the acid twice used yields 4th its bulk of nitric acid, Sp. gr. 1400. By prolonged boiling in platinum or glass vessels, the pulpy cotton in the mixture is decomposed with copious effervescence of carbonic acid and nitric oxyde gases; when this terminates and the acid in the boiler begins to blacken, the concentration has proceeded far enough, and on cooling the original sulphuric
acid is recovered with little diminution either of strength or quantity.
The washings in the several tubs being neutralized with carbonate of soda, yield on boiling down, a large quantity of mixed sulphate and nitrate of soda, which may be used for the economical manufacture of nitric acid, so as materially to diminish the cost of the process.
Reserving an account of the cost of manufacture, I proceed now to show the properties and effects of each of the three varieties of the cotton above described.
Best Quality, No. 1.
Snow white, explodes without leaving the least residuum or dampness -does not fire powder if ignited over it. Flashed on the hand causes no pain; is almost entirely soluble in sulphuric ether. One pound weight avoirdupois can easily and safely be compressed into the space of 128 cubic inches without diminishing its explosive power for ordnance or small arms.
Exposed to the air in a large room, protected from dust this quality of cotton (dried by solar heat for two days) fluctuates in weight according to the hygrometric state of the atmosphere-the maximum increase having been 1.34 per 100, as shown in the annexed Table of observations continued during 26 days.
At this maximum of absorption no diminution of projectile power was experienced in trials made with an eprouvette mandril gun, the invention of Colonel Forbes, especially suited to these experiments.+ But when the quantity of moisture designedly added exceeded three per 100, the explosive power fell rapidly, but was regained altogether by redrying the cotton.
With this quality of cotton trials were made at Dum Dum on the 19th and 25th of January, and 24th of February, with the results shown in the accompanying Table.
*The bulk of 4 pounds of ordnance gunpowder.
Of which I hope to be permitted to give a more minute account in a future number of the journal.
The ranges above exhibited are as nearly as possible four times as great as those given in the Woolwich tables of mortar practice in 1838, strength of powder from 21 to 227ths. With this powder an 8 inch mortar with 46 pound shot gave with 15 ounces a range of 700 yards
which was in all the above trials exceeded by 4 ounces of cotton.
In two trials made of some cotton prepared by Mr. Siddons, corresponding ranges were obtained with the 8 inch mortar and 6 pr. field gun.
Lastly a sample of cotton sent to me for trial by Mr. Scott of the H. Co.'s Dispensary tested by the mandril eprouvette gun gave a range of 110 feet against 111 of my first quality.
These experiments with cotton made with the utmost care by three different persons, show an extraordinary uniformity in the quality and
* Present_on_the 19th January-Lieut.-Col. Lawrenson, C. B., Capts. Whiteford, Broome, Douglas, and other officers of the Artillery Regiment.