GRAVIMETRIC DENSITY OF PRODUCTS OF EXPLOSION in. of water at this temperature weighs 62.35 lb, and therefore I lb of water bulks 1728+62.35=27.73 cub. in. 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. 30 30 28- ZB 28 26 Sometimes the factor 27.68 is employed, corresponding to a density of water of about 62.4 lb per cub. ft., and a temperature 12° C., or 54° 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 I 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-80v to v±ZAv, a change of volume of 27.73 AV cub. in., the, work done is 27.73 p w inch-tons, or (7) DE=2.31 pOv foot-tons; and the differences AE 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 o° 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 16X2240÷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 = 001273, which, with p=2440, v=5, p0-i, v0=700, makes T=4758, a temperature of 4485° C. or 8105 ° F.