214 
MR. ABEL’S RESEARCHES ON GUN-COTTON. 
same water-bath, in the manner already described, to 55° C. for six to seven -hours daily, 
during seventy days. After the first day’s heating, the column of mercury in each tube 
was slowly and uniformly depressed, the volume of gas evolved being somewhat greater 
from the second, smaller sample. At the conclusion of the seventy days’ treatment it 
was calculated, from the capacity of the tubes and the amount of total displacement, 
that the larger sample had evolved 172-88 cub. centims., and the other sample 189-1 
cub. centims. of gas ; as, however, a few small crystals of mercury-salt had been produced 
in each tube by the action of nitrous acid disengaged, those quantities are of course 
only proximate. Upon removal from the bulbs, the colour of both specimens was 
unchanged ; their odour was decidedly less pungent than that of the preceding speci- 
men ; both were acid to test-paper, the smaller sample being the most strongly so ; in 
neither instance was the strength of fibre impaired, the explosiveness diminished, or the 
solubility in ether and alcohol appreciably increased. The specimens were divided, 
put into stoppered bottles without any previous purification, and one bottle of each 
was preserved in the dark, the other being exposed to diffused light. None of the spe- 
cimens have up to the present time (a period of 3J years) undergone any further change. 
Experiment 104. — 13-8 grms. of gun-cotton were exposed in an exhausted bulb-tube, 
as already described, to 65° for six to seven hours daily, during a period of three months 
(eighty-four days). The depression of the mercury proceeded uniformly, but much 
more rapidly than in the preceding experiment. After several days’ exposure, a notable 
quantity of mercurous salt was deposited in crystals within the tube. At the termina- 
tion of the experiment the gun-cotton was not altered in colour and appearance, but 
upon removal from the bulb the fibre was found to be considerably weakened ; a pun- 
gent odour and strong acidity were exhibited by the specimen, its explosive properties 
were notably reduced, and it dissolved to a large extent in ether and alcohol, the solu- 
tion furnishing a collodion-film. A portion of the same gun-cotton enclosed in a smaller 
bulb-tube, sealed at both extremities, was exposed to heat for an equal period in the 
same water-bath. There was some pressure of gas upon opening the tube, ' and the gun- 
cotton exhibited the same appearance and properties as the sample heated over mercury. 
Both samples were placed in closed glass vessels, and have since been exposed to light 
for upwards of three years, without undergoing any further change. 
Experiments 105-108. — Four specimens of gun-cotton, each weighing 19-5 grms., 
taken from different samples, were introduced into bulb-tubes of almost the same capa- 
city and with stems of equal length. The bulbs were all enclosed in one water-bath, 
and the open extremities of the tubes were immersed in a mercury-bath, over which they 
were exhausted as in the preceding experiments. The water-bath was maintained at 
65° seven hours daily, the uniformity of the temperature being ensured by the employment 
of a self-acting gas-regulator. Before commencing the application of heat each morning, 
the extent of depression of the mercury in the tubes was noted ; and the volume of gas 
contained in each at stated periods was calculated from the observations made. The 
following Table shows the effects of uniform exposure to 65° upon these samples : — 
