760 GUN-COTTON 



water. It would bo very difficult to doviso a moro perfect cleansing process than that 

 to which the gun-cotton is thus submitted ; and the natural result of its application 

 is that the material thus additionally purified acquires considerably increased powers 

 of resisting the destructive effects of heat. Samples of tho pulped gun-cotton, even in 

 the most porous condition have been found to resist change perfectly upon long-con- 

 tinued exposure to temperatures, which developed marked symptoms of decomposition 

 in the gun-cotton purified only as usual. 



The pulping process applied to gun-cotton affords, therefore, important additional 

 means of purifying the material, the value of which may bo further enhanced by em- 

 ploying a slightly alkaline water in tho pulping machine. 



Shortly after tho discovery of gun-cotton in 1846, attempts were made to increase 

 the explosive force of that substance by impregnating it with a solid oxidising agent 

 such as saltpetre. The preparations of gun-cotton were saturated in a solution of tho 

 salt, and tho water was subsequently evaporated, but the quantity of the ' nitrate ' or 

 1 chlorate ' which could bo introduced by this, the only practical mode of treatment, 

 was so small as to bo of little value. The system of reducing gun-cotton to a lino 

 state of division by the pulping process has, however, afforded the means of readily 

 incorporating this substance with an agent sufficiently rich in oxygen to oxidise the 

 whole of the carbon in the gun-cotton preparation. This requires a comparatively 

 large proportion of saltpetre, or other analogous salt, and Mr. Abel succeeded in ob- 

 taining some very promising results in this direction. 



The general mode of producing nitrate' or 'chlorate* preparations of gun-cotton 

 may bo briefly described as follows : 



Tho requisite proportion of the oxidising agent, such as saltpetre, is reduced to a 

 very fine powder, and is then intimately mixed with the finely-divided or pulped gun- 

 cotton, by steeping the latter in a saturated solution of tho salt. The mixture is then 

 granulated or compressed into any desired form by tho usual method employed in tho 

 preparation of Abel's compressed gun-cotton. 



The products obtained in this way, especially in the disc or compressed state, possess 

 several important advantages over ordinary compressed gun-cotton. The nitrated 

 material forms very hard masses, which are much less liable to break up or give off 

 dust when roughly handled than the ordinary substance. This comparative hardness 

 is probably due to the particles of the mass becoming firmly cemented together by the 

 crystallisation of the salt on the evaporation of the water during tho process of drying. 

 Indeed, it has been found that the application of considerably less pressure than is 

 required to produce very compact cakes of ordinary gun-cotton suffices to furnish 

 masses decidedly superior both in hardness and compactness. Moreover, tho cakes, 

 or discs, of the nitrated preparation, when dry, are found to have become coated with 

 ft hard film of the salt, which acts as an additional protective against mechanical 

 injury and renders the surface less dusty, and thus less readily inflammable, than tho 

 ordinary kind. 



Again, it has been conclusively demonstrated by several experiments, continued for 

 considerable periods, that the nitrated preparation is more stable when exposed to tho 

 action of high temperatures than tho unimpregnated gun-cotton. 



So far, therefore, as concerns the question of storage and transport, tho nitrated 

 material possesses several important advantages over ordinary compressed gun-cotton, 

 but, on the other hand, it has two drawbacks. 



It has now been decided wisely, we think to store all large supplies of gun-cotton 

 in the wet state, in which condition the material is perfectly uninflammable by ordinary 

 heat. For this purpose the discs of gun-cotton are packed in large wooden waterproof 

 tanks, fitted with means of drainage. A tank holds a ton of gun-cotton discs, each 

 disc being three inches in diameter by about two inches in depth, and tho ordinary 

 material is wetted by simply filling the tank with water, and allowing tho latter to 

 drain off. 



With tho nitrated preparation, however, it is desirable that a weak solution of salt- 

 petre instead of pure water should be used in wetting tho gun-cotton. 



We do not urge this as a serious drawback ; but it is evident that the process of 

 wotting, and re-wetting when necessary, a store of ordinary gun-cotton is a compara- 

 tively simple process, whereas tho same operation might, in tho case of nit rat rd 

 gun-cotton, be attended with moro or less difficulty under certain circumstances of 

 storage. 



Again, the wet nitrated preparation does not dry so readily as the ordinary material ; 

 but, on tho other hand, this objection is almost negatived by tho fact that wet gun- 

 cotton, whether nitrated or not, can bo detonated, and made to produce equal, if not 

 superior, effects to the substance in the dry state. Gun-cotton has been detonated with 

 most destructive effect under water, by simply filling a bag not with discs, and explod- 

 ing them by means of one dry disc enclosed in a. waterproof envelope. The detonating 



