CHEMICAL HISTORY AND APPLIANCES OF GUN-COTTON. 
75 
difficult to understand how the addition of one per cent, to the mineral matter, in the 
form chiefly of silicates of lime and magnesia (the bases being derived from the water 
used in the final washing), which are deposited upon and between the fibres in a pul¬ 
verulent form, can influence, to any material extent, either the rate of combustion or the 
keeping qualities of the product obtained by Leak’s system of manufacture. 
Gun-cotton, prepared according to the system just described, is exceedingly uniform 
in composition. The analyses of samples prepared both in Austria and at Waltham 
Abbey have furnished results corresponding accurately to those required by the for- 
f TT 1 
mula C, \ o v 7 n ^ ^s ordinary air-dry condition it contains, very uniformly, 
about two per cent, of moisture ; an amount which it absorbs again rapidly from the 
air, when it has been dried. The proportion of water existing in the purified air-dried 
cotton, before conversion, is generally about six per cent. "When pure gun-cotton is 
■exposed to a very moist atmosphere, or kept in a damp locality, it will absorb as much 
as from six to seven per cent.; but, t if it be then exposed to air of average dryness, it 
very speedily parts with all but the two per cent, of moisture which it contains in its 
normal condition. It may be preserved in a damp or wet state apparently for an inde¬ 
finite period without, injury, for if afterwards dried by exposure to air, it exhibits no 
signs of change. 
In these respects it possesses important advantages over gunpowder. The normal 
proportion of hygroscopic moisture in that substance varies between three-quarters and 
one per cent.; but if exposed in any way to the influence of a moist atmosphere, it 
continires to absorb water until, however firm the grains may have originally been, it 
becomes quite pasty. It need scarcely be stated that, when once gunpowder has be¬ 
come damp, it can no longer be restored to a serviceable condition, except by being 
again submitted to the processes of manufacture, starting almost from the commence¬ 
ment. 
Perhaps the most vital considerations bearing upon the possibility of applying gun¬ 
cotton to important practical purposes, are those which relate to the risk likely to be 
incurred in its manufacture and preservation in large quantities. The manufacture of 
gun-cotton is unquestionably much safer than that of gunpowder; in fact, there is no 
possibility of accident until the final drying process is reached, as in all the other 
stages, the material is always wet, and therefore harmless. With the adoption of a 
proper system of wanning and ventilation in the drying-chamber, the last operation 
is certainly not a more dangerous one than that of drying gunpowder. The question 
of the safe preservation of gun-cotton cannot as yet be so easily and satisfactorily dis¬ 
posed of. Specimens of gun-cotton exist, which were prepared according to Schonbein’s 
directions in 184G, and which have undergone no change whatever ; on the other hand, 
it is well known that gun-cotton, which was believed to have been perfectly purified, 
has become extremely acid, and has even undergone so complete a decomposition as to 
have become converted into oxalic acid and other organic products, when preserved in 
closed vessels, and especially when exposed continually, or occasionally, to light. This 
susceptibility to chemical change has been particularly observed in samples of gun¬ 
cotton known to consist chiefly, or to contain some proportion, of the less explosive or 
lower substitution-products (i. e. gun-cotton specially prepared for the manufacture of 
collodion). Hence, it is very possible that such instances, as are considered to have 
been well authenticated, of the spontaneous ignition of gun-cotton, when stored in con¬ 
siderable quantities, or during exposure to very moderate heat, may have arisen not 
simply from an imperfect purification of the material, but also from the more or less 
imperfect conversion of cotton into the most explosive and apparently most stable 
product. 
There is no doubt that the improvements effected in the system of manufacture of 
gun-cotton have been instrumental in rendering it far more stable in character than it 
was in the early days of its production upon a considerable scale. At the same time, 
although General von Lenk and its warmest partisans consider that its unchangeability 
can no longer be disputed, a greater amount of experience, combined with more search¬ 
ing investigations than have hitherto been instituted, upon the possibility of its under¬ 
going change when under the influence of moderate heat, alone or combined with that 
of moisture, and when preserved under a variety of other conditions, are unquestionabty 
indispensable before its claims to perfect permanence can be considered as properly 
