ME. ABEL’S EESEAECHES ON GUN-COTTON. 
227 
considerable change, the decomposition proceeded much more rapidly in that material 
than in the alkalized samples. 
The influence of the small proportion of alkaline carbonate in retarding the decom- 
position of the gun-cotton becomes still more evident when smaller quantities of the 
material are experimented with. It is well illustrated by the results of experiment 29 
(Table I.), and those furnished by an equal quantity of the same gun-cotton impregnated 
with 0 - 4 per cent, of sodic carbonate. The former exhibited the first indications of 
change in three hours, the latter in seven hours, after first exposure. The temperature 
of the ordinary gun-cotton afterwards rose much more rapidly and considerably, and 
the loss of weight sustained by it in three days’ exposure was nearly double that which 
the “ alkalized” sample suffered in four days’ treatment, and the alteration sustained by 
the latter specimen was comparatively slight. 
But the protective power exerted by small proportions of carbonates is even more 
strikingly demonstrated by a comparison of experiment 125 with experiments 126 
and 127. While the “alkalized” sample exhibited no signs of change until after the 
lapse of seven hours, equal quantities of the same sample, purified from carbonates by 
washing, exploded after exposure to 100° for T25 hour. Experiment 128, made with 
another description of gun-cotton, also impregnated with a small proportion of sodic 
carbonate, is similarly illustrative of this protective power when compared with experi- 
ment 28, Table I., and with experiments 129 and 130, conducted with equal quantities 
of the original gun-cotton and with the same material freed from carbonates by washing. 
The comparison of experiment 131 with 132, and of 134 with 135, affords proof that 
the small proportion of earthy carbonates ordinarily existing in gun-cotton exert a de- 
cided protective action, and experiment 133, conducted with a specimen from which 
these carbonates had been completely extracted by acid treatment, furnished further con- 
firmation of this point. 
In the experiments instituted at 90° C., Nos. 138-141, conducted with samples of 
“ alkalized ” gun-cotton, also afford important proof of the protective effect of small 
quantities of carbonates, upon comparing the results with those furnished by experi- 
ments 142 and 143. The first of these samples scarcely sustained any alteration by ex- 
posure for thirty-two to thirty-six hours to 90° C. during six days, while the specimens 
of ordinary gun-cotton were considerably altered by similar treatment; 
Experiments 136 and 137 afforded a very decided proof that the silicating process 
prescribed by Von Lenk exerts some amount of protective influence upon gun-cotton 
when exposed to heat, though this result is not due, as supposed by him, to the closing 
up of the fibre by an insoluble silicate, but simply to the deposition of a small quantity 
of earthy (and possibly of alkaline) carbonate upon the fibre when the silicate undergoes 
decomposition during the drying and the subsequent washing process. The amount of 
protection thus afforded to the gun-cotton is, however, obviously as liable to variation as 
that resulting from the deposition of calcic and magnesian carbonates upon the material 
during the long-continued immersion in flowing water. Numerous specimens of gun- 
