514 Learned Soctettes. 
only loosely deposited between the fibre, the proportion is 
liable to be diminished by any manipulation to which the 
gun-cotton may be subject. g. The introduction into the 
finished gun-cotton of 1 per cent. of carbonate of soda, 
affords to the material the power of resisting any serious 
change, even when exposed to such elevated temperature 
as would induce some decomposition in the perfectly pure 
cellulose products. That proportion affords, therefore, 
security to gun-cotton against any destructive effects of 
the highest temperatures to which it is likely to be exposed 
even under very exceptional climatic conditions. The only 
influences which the addition of that amount of carbonate 
to gun-cotton might exert upon its properties as an ex- 
plosive would consist in a trifling addition to the small 
amount of smoke attending its combustion, and in a slight 
retardation of its explosion, neither of which could be re- 
garded as results detrimental to the probable value of the 
material. io. Water acts as a most perfect protective to 
gun-cotton (except when it is exposed for long periods to 
sun-light), even under extremely severe conditions of ex- 
posure to heat. An atmosphere saturated with aqueous 
vapour suffices to protect it from change at elevated tempe- 
ratures, and wet or damp gun-cotton may be exposed for 
long periods in confined spaces to 100 deg. C. without sus- 
taining any change. Actual immersion in water is not 
necessary for the most perfect preservation of gun-cotton : 
the material, if only damp to the touch, sustains not the 
smallest change, even if closely packed in large quantities. 
The organic impurities, which doubtless give rise to the 
very slight development of acid observed when gun-cutton 
is closely packed in the dry condition, appear equally pro- 
tected by the water; for damp or wet gun-cotton, which 
has been preserved for three years, has not exhibited the 
faintest acidity. If as much water as possible be expelled 
from wet gun-cotton by the centrifugal extractor, it is ob- 
tained in a condition in which, though only damp to the 
touch, it is perfectly non-explosive; the water thus left in 
the material is sufficient to act as a perfect protection, and 
consequently also to guard against all risk of accident. It 
is, therefore, in this condition that all reserve-stores of the 
substance should be preserved, or that it should be trans- 
ported in large quantities to very distant places. If the 
proper proportion of carbonate of soda be dissolved in the 
water with which the gun-cotton is originally saturated, for ~ 
the purpose of obtaining it in this non-explosive form, the 
