S.G. of stick of cordite

At the standard temperature of 62deg F. the volume of the gallon of 10 lb
of water is 277.3 cub. in.; or otherwise, 1 cub. ft. or 1728 cub. in. of
water at this temperature weighs 62.35 lb, and therefore 1 lb of water
bulks 1728 / 62.35 = 27.73 cub. in.

[Illustration: FIG. 8.]

Thus if a charge of P lb of powder is placed in a chamber of volume C cub.
in., the

(6) G.D.= 27.73P/C, G.V. = C/27.73 P.

Sometimes the factor 27.68 is employed, corresponding to a density of water
of about 62.4 lb per cub. ft., and a temperature 12deg C., or 54deg F.

With metric units, measuring P in kg., and C in litres, the G.D. = P/C,
G.V. = C/P, no factor being required.

From the Table I., or by quadrature of the curve in fig. 9, the work E in
foot-tons realized by the expansion of 1 lb of the powder from one
gravimetric volume to another is inferred; for if the average pressure is p
tons per sq. in., while the gravimetric volume changes from v - 1/2[Delta]v
to v + 1/2[Delta]v, a change of volume of 27.73[Delta]v cub. in., the work
done is 27.73p[Delta]v inch-tons, or

(7) [Delta]E = 2.31 p[Delta]v foot-tons;

and the differences [Delta]E being calculated from the observed values of
p, a summation, as in the ballistic tables, would give E in a tabular form,
and conversely from a table of E in terms of v, we can infer the value of
p.

On drawing off a little of the gas from the explosion vessel it was found
that a gramme of cordite-gas at 0deg C. and standard atmospheric pressure
occupied 700 ccs., while the same gas compressed into 5 ccs. at the
temperature of explosion had a pressure of 16 tons per sq. in., or 16 x
2240 / 14.7 = 2440 atmospheres, of 14.7 lb per sq. in.; one ton per sq. in.
being in round numbers 150 atmospheres.

The absolute centigrade temperature T is thence inferred from the gas
equation

(8) R = pv / T = p_0v_0/273,

which, with p = 2440, v = 5, p_0 = 1, v_0 = 700, makes T = 4758, a
temperature of 4485deg C. or 8105deg F.

[Illustration: FIG. 9.]

In the heading of the 6-in. range table we find the description of the
charge.

Charge: weight 13 lb 4 oz.; gravimetric density 55.01/0.504; nature,
cordite, size 30.

So that P = 13.25, the G.D. = 0.504, the upper figure 55.01 denoting the
specific volume of the charge measured in cubic inches per lb, filling the
chamber in a state of gas, the product of the two numbers 55.01 and 0.504
being 27.73; an