100 
CAPTAIN NOBLE AND ME. E. A. ABEL ON FIEED GUNPOWDEB. 
grms. of water through 1° C. In experiment 48 the explosion of the same quantity of 
R. L. G. was equivalent to raising 172,569 grms. of water through 1° C., and in 
experiment 63 to raising 171,500 grms. through 1°C. ; or, expressing these results in 
a ditferent form, it appears that the combustion of a gramme of powder gave rise to 
quantities of heat represented by raising a gramme of water through 702°-80 C., 
700 C -69C., and 696°-50 C. respectively. 
In experiments 47 and 49 the charge used was 393-978 grms.; and it was found 
that in experiment 47 the heat generated by the explosion of the F. G. was sufficient 
to raise 277,994T grms. of water through 1° C. ; and in experiment 49 the explosion of 
the same quantity of R. L. G. generated heat represented by the raising of 278,185-5 
grms. through 1° C., — or, in the two experiments, 1 gramme of powder gave rise 
respectively to 705-61 and 706-09 gramme-units. 
The mean of the whole of these experiments gives 702-34 gramme-units of heat 
generated by the explosion of a gramme of powder, and we shall probably have a very 
close approximation to the truth in assuming it at 705 gramme-units. 
From this datum the temperature of explosion may be deduced, if we know the 
mean specific heat of the products of combustion. We have only to divide 705 by the 
specific heat, and the result is the required temperature. 
The specific heat of all the gaseous products of combustion are known ; and they 
have also been determined for the principal solid products at low temperatures, when 
they are [of course] in the solid form. 
Bunsen and Schischkoff, from their experiments, deduced the temperature of 
explosion on the assumption that the specific heats of the solid products remain in- 
variable over the great range of temperature through which they pass. 
With every deference to those distinguished chemists we think their assumption is 
quite untenable. Without, we believe, any known exception, the specific heat is 
largely increased in passing from the solid to the liquid state. In the case of water 
the specific heat is doubled ; the specific heats of bromine, phosphorus, sulphur, and 
lead are increased from 25 to 40 per cent., and those of the nitrates of potassium and 
sodium nearly 50 per cent., while it is more than probable that, even with liquids, the 
specific heat increases very considerably with the temperature. 
We shall, however, deduce from our experiments the temperature of explosion on 
Bunsen and Schischkoff’s hypothesis, both with the view of enabling our results to 
be compared with theirs, and for the purpose of fixing a high limit, to which it is 
certain the temperature of explosion cannot reach. We shall afterwards endeavour to 
estimate more accurately the true temperature. 
The data necessary for computing the specific heat of a gramme of exploded powder 
are given in the subjoined Table. 
