GUN-COTTON 759 



acid, and recovers its original colour after brief exposure to air. If, after exposure to 

 light in open air for some days, the gun-cotton be placed in the dark, in cases which 

 are not air-tight, the odour becomes gradually fainter, and the effect upon litmus-paper 

 slighter ; if the packages containing the gun-cotton are air-tight, the odour and action 

 upon litmus do not increase during storage for several years (the actual experience 

 gained at Woolwich extends over nearly four years). 



If the gun-cotton be exposed for protracted periods to daylight with free access of 

 air, it speedily loses all odour and power of affecting litmus. If exposure to diffused 

 daylight in confined spaces be continued, the first results of the action of light are, of 

 course, retained ; but up to the present time no single indication of their increase has 

 boon observed ; indeed, the very faint acid reaction described, which was developed 

 nt first, has frequently disappeared, probably in consequence of the neutralising 

 action of small quantities of earthy carbonates contained in the gun-cotton. 



But if the material be exposed continuously in a perfectly confined space to the 

 action of sunlight or strong daylight, it furnishes, after a time much greater evidence 

 of change than that already described. The acidity gradually becomes more mani- 

 fest ; the odour increases, and becomes in time somewhat pungent, and indicative of 

 the presence of very small quantities of nitrous acid ; and litmus-paper, if confined 

 in a vessel with gun-cotton thus exposed, becomes entirely bleached after two or three 

 months. Although specimens of gun-cotton always undergo some spontaneous change 

 under these very special circumstances, the decomposition proceeds with extreme slow- 

 ness ; and the results of the observations are, therefore, in this respect quite at vari- 

 ance with those recently published by De Luca, who states that the specimens operated 

 upon by him decomposed upon exposure to sunlight, some on the first day of the 

 experiment, others after several days' exposure. 



The advantages arising from the reduction of gun-cotton fibre to a state of fine divi- 

 sion are thus explained by Mr. Abel : 



Abundant proofs have been obtained that the long-continued wasting and the treat- 

 ment with an alkaline liquid to which gun-cotton is submitted, do not completely 

 separate from it products of the partial oxidation of organic impurities retained by 

 the cotton up to the time of its conversion. This is unquestionably due in great mea- 

 sure to the tubular structure of the fibre. If the impurities were merely upon the 

 surface of the fibre, their perfect removal by the action of solvents should be accom- 

 plished without difficulty ; but it does not appear that even long-continued digestion 

 of gun-cotton in alcohol has the effect of completely freeing it of the impurities soluble 

 in that liquid which are locked within the fibre. The action of a warm or cold alkaline 

 liquid upon the material might perhaps eventually result in the complete removal of 

 these bodies ; but the loss of product and destructive effect upon the fibre, resulting 

 from any other than a brief digestion in a very dilute alkaline bath, are too consider- 

 able to admit of such a treatment. The following experiments may be quoted in 

 illustration of this : 



A quantity of gun-cotton, which had already been submitted to the usual purifica- 

 tion with water and a hot alkaline bath, was boiled for ten minutes in a solution of 

 potassic carbonate, of the strength usually employed (of specific gravity 1-02). By 

 this treatment the material sustained a loss of 3*7 per cent. ; the bath having as- 

 sumed an amber colour. Upon being again boiled for twenty" minutes in the same 

 alkaline bath, which thereby became considerably deepened in colour, the sample sus- 

 tained a further loss of 12-09 per cent. The strength of the fibre had been consider- 

 ably reduced by this treatment. 



6'5 grms. of gun-cotton and 0-4 grm. of sodic carbonate were placed together with 

 50 cubic centims. of water in a flask, to which a vertical condenser was attached, 

 and were heated to 100 for twelve hours. The alkali was then found to have become 

 nearly neutralised, and the dark brown liquid contained sodic nitrate in abundance. 

 The gun-cotton was washed and twice treated in the same manner, the alkali being 

 neutralised on each occasion, as in the first instance. 



But though it is evident that the treatment of gun-cotton with warm alkaline baths 

 cannot be advantageously extended, satisfactory proof has been obtained that the 

 stability of gun-cotton which has been purified as far as is possible by the present 

 system, may be importantly increased by submitting the material to a special process 

 of washing. 



In the experiments instituted upon the application of gun-cotton as a substitute for 

 gunpowder, some very advantageous results have attended the conversion of the 

 material into homogeneous masses of tfny desirable form or density by preparing it 

 according to the method commonly employed for converting rags into paper. In re- 

 ducing the material to a very fine state of division by means of the ordinary beating 

 and pulping machines, the capillary power of the fibres is nearly destroyed, and the 

 gun-cotton is for a considerable period very violently agitated in a large volume of 



