GUN-COTTON, a detonating substance, invented by SchOnbein in 1846, and obtained in the following manner: One part of finely-carded cotton is immersed in 15 parts of a mixture of equal measures of strong nitric acid (sp. gr. 1.5) and sulphuric acid (sp. gr. 1.845). The cotton must be completely immersed in the mixture, otherwise it becomes so hot as to undergo immediate decomposition. After a few minutes' immer sion, it must be plunged into a large volume of cold water, and then washed till the moist mass ceases to show any acid reaction when placed on litmus paper. It is then to be carefully dried at a temperature not exceeding 170'.
Any substance containing cellulose, such as tow, linen, saw-dust, paper, etc., may be employed instead of cotton, and the change that takes place in the formation of the explosive compound seems, from the researches of Hadow, to be as follows: the com position of cellulose is represented by the formula C3,1130030. In the formation of gun cotton or pyro.ty/in (derived from pyr, fire, and ecylon, wood), nine equivalents of the hydrogen are replaced by an equal number of equivalents of peroxide of nitrogen (NO,), so that the formula for the new compound is The.tiber, in undergoing this change, increases about 70 per cent in weight, and acquires perfectly new properties. Although scarcely differing in appearance from unchanged cotton, it may be distinguished from it by its harshness, by the crepitating sound which it yields when pressed by the hand, by its having lost the property of depolarization which ordi nary cotton possesses, and by its electric condition. Iodine dissolved in a solution of iodide of potassium affords a certain means of distinguishing explosive from ordinary cotton. If the former is moistened with this iodine solution, and a little dilute snplin tie acid is subsequently added (one part of the acid to four of water), a yellow color is evolved; while ordinary cotton wool, when similarly treated, assumes a blue color. Its most remarkable property is, however, the facility with Nadal] it takes fire, and its rapid and complete combustion. The resnits of gen. von Lenk's improvements in the manu facture of gun-cotton, which, however, did not lead to its superseding gunpowder in any one direction, are given below. The more recent experiments of prof. Abel, which were carried on with elaborate care for a number of years at the Woolwich arsenal, have resulted in further improving the manufacture, and also in determining more accurately the properties of gun-eottor. Abel's proeeSs consists in cotton
waste in strong nitric and sulphuric acids at a low temperatdre:and afterwards wash lug it thoroughly. It is next reduced to a pulp in a common rag-engtne (sec PAPER), and then in the pulpy condition it is washed again in a large quantity of water to remove every trace of free acid. After that, it is pressed at a low power, and subse quently in a powerful hydraulic press, out of which it conies in so wet a state as to be uninflammable. Gun-cotton can tints be compressed into masses of any shape, as cylinders or cubes, and of any required density or hardness. It can also be converted into the form of paper, or into gun cotton grains for sporting purposes.
Gun-cotton can now be manufactured so as to keep, there is every reason to believe,. with perfect safety in a wet state, aq be as good as ever when dried again. The results of sonic experiments carried on a year or two ago by a government committee at Chat ham showed that when guncotton is firmly confined, it exerts a destructive effect equal to about five times that of gunpowder.
Prof. Abel has proved that the inure thoroughly gun-cotton is compressed, the more perfectly can its action be controlled, and it is now generally used in compact disks for mining purposes; that it is sympathetic, so that, if gently ignited by a spark, in the form of yarn, it smolders slowly away; if by a flame, it burns up rapidly; and if fired in the compressed state by a detonating fuse, it explodes with great violence, crew when unconfined. The most recent and striking discovery it, however, is, that although, as a rule, non-inflammable and non-explosive in the wet state, yet, when fired in this condition with the detonating substance fulminate of mercury, and a little dry gun-cotton or gunpowder, it explodes with as much violence as when it is dry.
While gunpowder does not explode at a lower temperature than 600° F., gun-cotton has been known to do so at 277' F., and cannot be heated to 400° F. without explosion. Gun-cotton produces neither smoke nor folding when fired, and does not heat the gun so much as gunpovtder, though, by the rapidity of its explosion, it strains the barrel snore.