0277] The result is plotted in figs. 8 and 9, in a curve showing
the relation between p and D the _gravimetric density_, which is the
specific gravity of the P lb of powder when filling the volume C, cub. in.,
in a state of gas; or between p and v, the reciprocal of D, which may be
called the _gravimetric volume_ (G.V.), being the ratio of the volume of
the gas to the volume of an equal weight of water.

[Illustration: FIG. 7. Explosion Vessel.]

The results are also embodied in the following Table;--

TABLE 1.
Pressure in Tons per sq. in.
G.D. G.V. Pebble Powder. Cordite.
0.05 20.00 0.855 3.00
6 16.66 1.00 3.80
8 12.50 1.36 5.40
0.10 10.00 1.76 7.10
12 8.33 2.06 8.70
14 7.14 2.53 10.50
15 6.66 2.73 11.36
16 6.25 2.96 12.30
18 5.55 3.33 14.20
20 5.00 3.77 16.00
22 4.54 4.26 17.90
24 4.17 4.66 19.80
25 4.00 4.88 20.63
26 3.84 5.10 21.75
30 3.33 6.07 26.00
35 2.85 7.35 31.00
40 2.50 8.73 36.53
45 2.22 10.23 42.20
50 2.00 11.25 48.66
55 1.81 13.62 55.86
60 1.66 15.55 63.33

The term _gravimetric density_ (G.D.) is peculiar to artillerists; it is
required to distinguish between the specific gravity (S.G.) of the powder
filling a given volume in a state of gas, and the specific gravity of the
separate solid grain or cord of powder.

Thus, for instance, a lump of solid lead of given S.G., when formed into a
charge of lead shot composed of equal spherules closely packed, will have a
G.D. such that

(4) G.D. of charge of lead shot
--------------------------- = 1/6 [pi] [sqrt]2 = 0.7403;
S.G. of lump of solid lead

while in the case of a bundle of cylindrical sticks of cordite,

(5) G.D. of charge of cordite
-------------------------- = 1/6 [pi] [sqrt]3 = 0.9067.