ery susceptible
to heat, and even when quite pure will not stand a temperature of 100 deg. C.
for a longer period than a few hours, without undergoing decomposition. Up
to a temperature of 45 deg. C., however, properly made and purified nitro-
glycerine will remain unchanged almost indefinitely. The percentage
composition of nitroglycerine is as follows:--

Found. Theory for C_{3}H_{5}(N0_{2})_{3}.

Carbon 15.62 15.86 per cent.
Hydrogen 2.40 2.20 "
Nitrogen 17.90 18.50 "
Oxygen ... 63.44 "

The above analysis is by Beckerheim. Sauer and Adou give the nitrogen as
18.35 to 10.54 per cent. by Dumas' method; but I have never found any
difficulty in obtaining percentages as high as 18.46 by the use of Lunge's
nitrometer. The decomposition products by explosion are shown by the
following equation--

2C_{3}H_{5}(NO_{3})_{3} = 6CO_{2} + 5H_{2}O + 6N + O;

that is, it contains an excess of 3.52 per cent. of oxygen above that
required for complete combustion; 100 grms. would be converted into--

Carbonic Acid (CO_{2}) 58.15 per cent.
Water 19.83 "
Oxygen 3.52 per cent.
Nitrogen 18.50 "

The volume of gases produced at 0 deg. and 760 mm., calculated from the above,
is 714 litres per kilo, the water being taken as gaseous. Nitro-glycerine
is decomposed differently if it is ignited as dynamite (i.e., kieselguhr
dynamite), and if the gases are allowed to escape freely under a pressure
nearly equal to that of the atmosphere. Sarrau and Vieille obtained under
these conditions, for 100 volumes of gas--

NO 48.2 per cent.
CO 35.9 "
CO_{2} 12.7 "
H 1.6 per cent.
N 1.3 "
CH_{4} 0.3 "

These conditions are similar to those under which a mining charge, simply
ignited by the cap, burns away slowly under a low pressure (i.e., a miss
fire). In a recent communication, P.F. Chalon (_Engineering and Mining
Journal_, 1892) says, that in practice nitro-glycerine vapour, carbon
monoxide, and nitrous oxide, are also produced as the result of
detonation, but he attributes their formation to the use of a too feeble
detonator.

Nitro-glycerine explodes very violently by concussion. It may be burned in
an open vessel, but if heated above 250 deg. C. it explodes. Professor C.E.
Munroe gives the firing point as 2O3 deg.-2O5 deg. C., and L. de Bruyn[A] states
its boiling po