"

The volume of permanent gases at 0 deg. and 760 mm. is constant, and assuming
the gramme as the unit of mass, is found to be 22.32 litres. Thus:--

Volume of 44 of CO_{2}, at 0 deg. and 760 mm. = 44/1.9712 = 22.32 litres.
18 " H_{2}O " " = 18/0.8044 = 22.32 "
28 " N_{2} " " = 28/1.2544 = 22.32 "
32 " O_{2} " " = 32/1.4366 = 22.32 "

Therefore

132 grms. of CO_{2} at 0 deg. C and 760 mm. = 22.32 x 3 = 66.96 litres.
45 " H_{2}O " " = 22.32 x 2-1/2 = 55.80 "
42 " N_{2} " " = 22.32 x 1-1/2 = 33.48 "
8 " O_{2} " " = 22.32 x 1/4 = 5.58 "
____________

161.82 "
Therefore 1 gram-molecule or 227 grms. of nitro-glycerine when exploded,
produces 161.82 litres of gas at 0 deg. C and 760 mm.

To determine the volume of gas at the temperature of explosion, we simply
apply the law of Charles.[A] Thus--

V : V' :: T : T' or V' = VT'/T

in which V represents the original volume.
V' " new volume.
T " original temperature on the absolute scale.
T' " new temperature of the same scale
In the present case T' = 6001 deg..

Therefore substituting, we have

V' = 161.82x6001/273 = 3557 litres

or at the temperature of explosion 1 gram-molecule of nitro-glycerine
produces 3,557 litres of permanent gas.

[Footnote A: According to the law of Charles, the volume of any gas varies
directly as its temperature on the absolute scale, provided the pressure
remains constant. Knowing the temperature on the centigrade scale, the
corresponding temperature on the absolute scale is obtained by adding 273
to the degrees centigrade.]

~Pressure or Crusher Gauge.~--There are many forms of this instrument. As
long ago as 1792 Count Rumford used a pressure gauge. The so-called
crusher gauge was, however, first used by Captain Sir Andrew Noble in his
researches on powder. Other forms are the Rodman[A] punch Uchatius
Eprouvette, and the crusher gauge of the English Commission on Explosives.
They are all based either upon the size of an indent made upon a copper
disc by a steel punch fitted to a piston, acted upon by the gases of the
explosive, or upon the crushing or flattening of copper o