which is equal to 14,317 kilogrammes per square centimetre. The pressure developed by 1 kilogramme of pure nitro-glycerine equals 18,533 atmospheres, equals 19,151 kilogrammes. Applying this formula to gun- cotton, and taking after Berthelot, Q = 1075, and after Vieille and Sarrau, V_{o} = 671 litres, and c as .2314, and the density of the nitro-cellulose as 1.5, we have (V = O)
P = 671(1 + 1075/(273 x .2314))/.666 = 18,135 atmospheres.
To convert this into pressure of kilogrammes per square centimetre, it is necessary to multiply it by the weight of a column of mercury 0.760 m. high, and 1 square centimetre in section, which is equal to increasing it by 1/30. It thus becomes
P^{k} = (1 + 1/30).
P^{k} = 18,135 x 1.033 = 18,733 kilogrammes.
The following tables, taken from Messrs William Macnab's and E. Ristori's paper (Proc. Roy. Soc., 56, 8-19), "Researches on Modern Explosives," are very interesting. They record the results of a large number of experiments made to determine the amount of heat evolved, and the quantity and composition of the gases produced when certain explosives and various smokeless powders were fired in a closed vessel from which the air had been previously exhausted. The explosions were carried out in a "calorimetric bomb" of Berthelot's pattern.[A]
[Footnote A: For description of "bomb," see "Explosives and their Power,"
Berthelot, trans. by Hake and Macnab, p. 150. (Murray.)]
Table Showing Quantity of Heat and Volume and Analysis of Gas Developed per Gramme with Different Sporting and Military Smokeless Powders Now In Use
______________________________________________________________________
| | | | |
Name of Explosive. | Calories | Permanent | Aqueous | Total Volume |
| per grm. | Gases. | Vapour. | of Gas at 0° |
| | | | and 760 mm. |
______________________|__________|___________|_________|______________|
| | cc/grm | cc/grm | cc/grm |
E.C. powder, English | 800 | 420 | 154 | 574 |
S.S. powder | 799 | 584 | 150 | 734 |
Troisdorf, German | 943 | 700 | 195 | 895 |
Rifleite, English | 864 | 766 | 159 | 925 |
B.N., French | 833 | 738 | 168 | 906 |
Cordite, English | 1253 | 647 | 235 | 882 |
Ballistite, German | 1291 | 591 | 231 | 822 |
Ballistite, Italian | 1317 | 58l | 245 | 826 |
and Spanish | | | | |
______________________|__________|___________|_________|______________|
The figures in column headed "Co-efficient of Potential Energy" serve as a measure of comparison of the power of the explosives, and are the products of the number of calories by the volume of gas, the last three figures being suppressed in order to simplify the results.