CAPTAIN NOBLE AND ME. E. A. ABEL ON EIEED GUNPOWDEE. 
59 
products of combustion were entirely or partially confined, was, that the maximum 
pressure of fired gunpowder, of the usual gravimetric density, when unrelieved by 
expansion, did not greatly exceed 6100 atmospheres (40 tons to the square inch). 
Upon the same occasion a curve was exhibited, showing the relation between the 
tension and the density of the exploded products. These results have been confirmed by 
our present more extensive and exact investigations. 
Captain Noble also stated that, by means of a special apparatus, which was fully 
described at the time, he had not only determined the tension of the gases at various 
densities, but had exploded considerable charges filling entirely the chambers of close 
vessels, and had altogether retained and at pleasure discharged the gaseous and other 
products of combustion *. 
Berthelot f published, in 1872, a collection of theoretical papers upon the force of 
powder and other explosive substances. 
Berthelot does not attempt to evaluate the force of fired gunpowder, but evidently 
accepts as tolerably correct J the tensions assigned by Rumford and Piobert, and accounts 
for the discrepancy between their conclusions and those of the modern chemists by 
assuming that the laws of Mariotte and Gay-Lussac lose all physical significance for 
pressures so enormous as those developed in the combustion of gunpowder. 
Berthelot is disposed § to think that dissociation plays a considerable role during the 
expansion of the products in the bore of a gun. He supposes that the phenomena of 
dissociation do not exercise their influence only during the period of maximum effect, 
but that, during the expansion of the gases, a cooling effect is produced, by which a 
more complete combination is effected and more heat disengaged. 
Taking Bunsen and Schischkoff’s experiments as a basis, Berthelot expresses the 
decomposition experienced by gunpowder by the equation || 
I6KNO3+6S+ 13C=5K 2 S0 4 +2K 2 C0 3 +K 2 S+16N+11C0 2 , 
which he considers represents their results with sufficient exactness. 
In 1873 M. de Tromenec^J communicated to the Academy of Sciences a short memoir 
on the means of comparing the absolute force of varieties of powder. His method was 
based upon the principle that, when a body is exploded without producing mechanical 
effect, the “ force disponible ” is converted into heat, and that it is only necessary to 
explode a given weight in a close vessel and determine the heat produced. 
The apparatus used by De Tromenec was closed in much the same manner as was 
'* In the present paper, in Section K, the results of some of Capt. Noble’s earlier experiments are given. 
They accord, as will he seen, exceedingly well with the series we have discussed at length ; hut a few experi- 
ments made with a fine-grained powder are excluded, both because the powder, being sporting, was not com- 
parable with the fine-grain used in the present researches, and because the differences in their composition are 
unknown, the sporting-powder not having been analyzed. 
f Sur la Force de la Poudre. Paris, 1872. J Loc. cit. p. 80. § Loc. cit. p. 83. 
|| Loc. cit. p. 91. Comptes Rendus de l’Academie des Sciences, tom. lxxvii. p. 126. 
i 2 
