I. A. P. Barnard on the Explosive Force of Gunpowder. 251 
manner, if W, be the weight of the fixed residuum, expressed 
in grammes, the bulk of the residuum will be mi The space 
occupied by the gases will therefore be ut “ as = 050872 c.¢, 
As, at 0° C. and 0™™-760 of pressure, the same gases occupy 
193°1 c. c. per gramme weight of powder, the elastic force due 
to difference of volume only would be expressed by 
193-1 W 193°1 19371 
FSET ee iste Snes — 379: 
WwW, Ww. (if W,=1 gramme) — 06806 aie ee 58, 
Bi ine 1039°——«O5 
Thus, the pressure in atmospheres would be 379°58, if there 
were no elevation of temperature produced by the combustion. 
~_-=-96246 
1°039 
c.c., and the space originally filled by the gases being 0°50872 
c. ~ the relative original bulk of gas and powder will be 
50872 
"96246 
the foregoing formulz, when / is unity. 
e volume of the gases having been reduced to zero of tem- 
perature, the effect of an elevation by combustion of 3340° C., 
may be computed by assuming the absolute zero at —274° C., 
which is the latest determination as given by Rankine. Putting 
then p for the pressure, we shall have 
340 
pr Be 9:58(1 _ oa) = 50065 atmospheres. 
The original bulk of one gramme of powder being 
=0°52856, which is therefore the numerical value of @ in 
This value exceeds that found by the experimenters them- 
selves by 632°9 atmospheres. The difference is owing almost 
powder, and 1-039 for that of powder w 
obvious that, in a gun, we must sgh the higher value. There 
is also a slight difference between the determinations, aaa, 
a difference in the assumed place of the absolute zero. The 
coefficient of expansion employed by the experimenters is 
(1+0-00366 t), which corresponds a zero at —273°-225 C. 
Adopting their specific gravity with the zero at —274°, the pres- © 
sure would be 4364, or about ten atmospheres less than the de- 
termination of the experimenters. 
_ We are now in condition to apply the formulz above given, 
to the computation of the velocities which the initial pressure 
