232 CAPTAIN NOBLE AND MR. F. A. ABEL ON FIRED GUNPOWDER. 
That temperature may not improbably be taken at the high limit of the temperature 
of explosion for the Spanish pellet, which, as conjectured by us, has been proved to 
have developed a higher temperature than any other powder with which we have 
experimented. 
The complete fusion of the platinum with this powder, and with this alone, is thus 
shown not to be an isolated or accidental occurrence, but to depend on a real difference 
of temperature, and we are thus by two converging lines of reasoning brought to the 
conclusion that for pebble or R. L. G. powder the temperature of explosion may be 
taken as a little above the melting point of platinum, say about 2100° C., while the 
temperature of explosion of a powder like the Spanish pellet may be taken as occa¬ 
sionally ranging up to 2200° C. 
The data at our disposal are not sufficient to enable us to determine the temperature 
of explosion of the English mining powder with the same accuracy, but it is probable 
that 2000 ° C. and 1800° C. may be assigned as the limits between which the true 
temperature may be placed. 
After our remarks on the slight differences or accidents which appear to give rise 
to not inconsiderable variations in the products of decomposition of gunpowder, it is 
hardly necessary to point out that such differences in decomposition are nearly sure to 
give rise to corresponding variations in the temperature of explosion, and that therefore 
this temperature, even in one and the same powder, cannot be supposed to be always 
identical. * 
The relation between the tension of the gases developed by the explosion of gun¬ 
powder (when it is expanded in the bore of a gun with production of work) and the 
volume which these gases occupy is in our first memoirt expressed by the relation 
Cp+jSA. 
p_ [ PpCi-g) 
Po 1 v-uv 0 
where p is the tension of the permanent gases corresponding to volume v, C p the 
specific heat of the permanent gases at constant pressure, C„ the specific heat at 
constant volume, a the ratio which the volume of the non-gaseous products of explosion 
bears to the volume of the unexploded powder, /3 the ratio between the weights of the 
non-gaseous and gaseous portions of the products of explosion, X the specific heat of 
the non-gaseous products ; but in that memoir the values of the constants C /t> C r , and /3 
were calculated from a few of the analyses that were first made. The completion of 
the whole of our analyses has enabled us to recalculate these three constants, and their 
Cv +/3A 
(30) 
* It is by no means improbable that owing to the larger proportion of carbon which assumes the 
higher state of oxidation as the pressure under which the explosion takes place is increased, the tem¬ 
peratures at high tensions may be somewhat greater than those which occur when the powder is fired 
under low tensions. 
f Phil. Trans., 1875, Part I., p. 129. 
