Abel's process for the manufacture of mili tary guncotton was as follows : The cotton used was what is known as °cop° or weaver's waste, which is the tangled clippings from the spinning room of a cotton mill ; the thready form of this material being preferred to the fluffy form of the unworked Cotton. This was first hand picked to remove the larger foreign bodies present and to open out after baling. It was then boiled in 200-pound lots in caustic soda solution to remove grease, oils and the in crusting substances on the fibres, then wrung out in a centrifugal wringer and dried in a heated closet. It was then put through a cot ton picker to open up the fibre and remove for eign bodies which had been overlooked in the hand-picking, and was then dried in a second closet at 225° F. until it contained not over one half per cent of moisture, when it was stored in small lots in hermetically sealed metal vessels to cool. It was then dipped in lots of one pound each in 150 pounds of acids, consisting of one part by weight of nitric acid, 1.5 specific gravity, to three parts by weight of sulphuric acid, 1.845 specific gravity, contained in large iron trough about which cold water cir culated so as to maintain a temperature of 70° F. throughout the dipping. The cotton was plunged rapidly under the acid, allowed to remain immersed for 10 minutes, removed to a shelf above the acid dipping trough, where it was squeezed to remove the excess of acid, and then at once transferred to a two-gallon crock made of acid-proof earthenware. As transferred to this digestion crock the cot ton carried with it from 10 to 12 pounds of the acid mixture, and by pressing the mass down in the crock with an iron tool, the cotton was forced to the bottom and covered with a layer of the acid mixture which was squeezed from it. The crock was then covered and placed in a wooden trough where it was partly surrounded with cool water, which was kept in constant circulation, and where it was allowed to remain, so that the cotton could °digest° the acid, for 24 hours. Then the contents were thrown into a steel centrifugal wringer by which the greater part of the acid was removed. The guncotton was then thrown into a tub holding 800 gallons of water through which a large stream of water was continually flowing and in which a large paddle-wheel was in revolution so as to very quickly briny the acid guncotton into con tact with so large a volume of cold water as to prevent its becoming heated. The guncotton was then boiled twice for eight hours each in a diluted solution of soda, wrung out and washed with fresh water and put in the pulper. This was an ordinary ubeater,° urag-engine,° or °Hollander,° such as is used in the paper making industry, and the guncotton, suspended in water, was subjected to the action of the machine for two days in charges of from 300 to 350 pounds, where, by the shearing action of the knives, the fibres were cut into short lengths and the guncotton was reduced to the fineness of cornmeal, and mixed into a pulp with the water present. This was drawn into a large tank, known as the poacher, where the powdered guncotton was allowed to settle and the supernatant water drawn off. Fresh water was added and, by means of a revolving paddle in the poacher, the guncotton was mixed with it and washed by it, and this washing was re peated six or seven times until the chemical test of a sample showed that the acid had been completely removed. Then It was treated with a solution of lime containing a small quantity of caustic soda and also of precipitated chalk, and the mass was ready for molding.
The pot nitration system devised by von Lenk and developed by Abel, as described above, has now been replaced (1) by the centri fugal method wherein the nitration is carried on in large iron centrifuges so that after the °digestion° has gone on for a sufficient time the major part of the °spent) acid is run off and the residue, down to 1% parts for every part of cotton, l's wrung out by the rotation of the centrifuge, and (2) by the Nathan and Thomson displacement process which makes use of shallow earthenware pans, set on pedestals, and provided with pipes through which to in troduce the nitrating acids and remove the spent acids. The bottoms of the pans are conical and
these bottoms are covered with removable per forated plates, the nitrating acid is then run in, the dried cotton dipped into it, and when the entire charge has been dipped it is covered with a perforated plate, whose upper surface is then slowly covered with cool water. °Diges tion* is then allowed to proceed for the desired length of time and when completed, the waste acid cocks below the pans are opened to drain off the aspene acid and cold water is at the same time run in through the top plates to dis place the last of the acid and wash the gun cotton.
As shown above the first use to which gun cotton was put was as a propellent in guns, and Abel devised means for making powder grains from the pulped guncotton, but he soon pointed out the advantages which it possessed, when compressed, or use in military and naval mines and torpedoes and for engineering operations in times of war, and these are the chief uses to which it has been put. To compress it the alka line solution from the poacher, containing the finely divided guncotton in suspension, was pumped up to a stuff-chest, which is a cylin drical tank containing a vertical shaft armed with paddle-blades which, by revolving, keeps the guncotton in suspension. From here, by means of a wagon, the pulp was run into a hydraulic press where it was subjected to a pressure of 100 pounds to the square inch and thereby molded into blocks. These blocks were then transferred to another press where they were subjected to a pressure of from 6,000 to 6,800 pounds to the square inch. As made at the United States naval torpedo stations the blocks from the molding press were prismatic, with the vertical edges chamfered, 2.8 inches in diameter by 5% to 5% inches high, with a cir cular hole % inch in diameter, produced by a mandrel in the press, running vertically through the centre of the prism. After final pressing the blocks were 2.9 inches in diameter by 2 inches high, the hole remaining practically unchanged, and they still contained from 12 to 16 per cent of water, though as sent out into the service as wet guncotton° they were soaked in water until they contained 35 per cent. In the final press by means of steel dies, inscriptions in letters and figures, such as the place and date of manufacture and factory lot, were placed upon each block.
In the fibrous condition guncotton appears like the cotton from which it is made, but it has a harsher feel and it becomes electrified by friction when dry. When dry if rubbed in the dark it becomes phosphorescent. Under the miscroscope by polarized light it exhibits colors, while cotton is Pure guncotton is without order or taste and is insoluble in water. The gravimetric density before pulping is 0.1, after pulping 0.3, and after compression from 1.0 to 1.3, but by excessive pressure it has been raised to 1.4. The real specific gravity of gun cotton is 1.5. When dry, compressed guncotton is detonated by inserting a detonator in the hole in the block and firing it. Wet guncotton is detonated by the detonation of a block of dry guncotton fired hi contact with it. The violence of the explosion of guncotton when thus de tonated is comnarable with, if not superior to, that of nitroglycerin. Dry guncotton may be set on fire and, when compressed, it burns so slowly in the open that the fire may be extin guished by pouring water upon it. Wet gun cotton, thoroughly saturated with water, can be shaped by a tool without taking fire or ex ploding. In forming the cylindrical and conical charges for the torpedoes thrown from the pneumatic guns of the United States steamship Vesuvius at Santiago, the prismatic blocks above described were sawn with a band saw, turned in a lathe and cut with chisels as wood is treated, but care was used to keep the blocks and dust wet throughout the process.