504 
Proceedings of Societies. 
[July, 
that memoir. In discussing M. Berthelot’s views respecting the 
objections which the authors raise against the acceptance of any 
chemical equation as giving even a general idea of the meta- 
morphosis which a gunpowder of average composition may be 
considered to. undergo when exploded in a confined space, they 
disclaim having had any intention to convey the impression, 
which indeed they consider that their expressions were not cal- 
culated to convey, that it was impossible to put into some form 
of equation a representation of a variety of reactions which, if 
assumed to take place simultaneously, among different propor- 
tions of the powder-constituents, might give approximate ex- 
pression to the results obtained in any one particular experiment, 
and might, thus far, afford some approach to a theoretical repre- 
sentation of the metamorphosis of gunpowder. What they 
desired to point out and lay stress upon was the conclusive 
proof, which is afforded by the very great variations in compo- 
sition, of the solid portions more particularly, of the produces of 
explosion of samples of gunpowder presenting only small differ- 
ences of composition (and even of the products furnished at 
different times by one and the same sample), that the reactions 
which occur among the powder-constituents are susceptible of 
very considerable variations, regarding the causes of which it 
appears only possible to form conjectures, and that, consequently, 
“ no value whatever can be attached to any attempt to give a 
general chemical expression to the metamorphosis of gunpowder 
of normal composition.” An examination of the results of the 
author’s experiments on the heat generated by the combustion 
of gunpowder shows, first, that the heat thus generated is sub- 
ject to very wide variarions, dependent upon the particular nature 
of the powder employed (the Spanish powder, for example, gene- 
rates just 50 per cent more heat than the mining powder) ; and, 
secondly, that the heat evolved by the same description of 
powder varies in different experiments to a greater extent than 
is to be accounted for by errors of observation. The authors’ 
views on this head are confirmed by calorimetric determinations 
in their researches on gun-cotton. In these determinations, 
which have been carried on with precisely the same apparatus, 
no appreciable difference was found in the heat evolved in the 
various experiments. It is of high importance to observe that 
the volume of the permanent gases generated is in every case 
in inverse ratio to the units of heat evolved, as is shown by the 
following table . — 
Nature of Powder. 
Units of Heat Cub. centims. of 
per Gramme Gas per Gramme 
Spanish pellet powder ... 
Curtis and Harvey’s No. 6 
exploded. exploded, 
767*3 234-2 
W.A.F.G 
W.A.R.L.G 
W.A. Pebble 
Mining 
764-4 241*0 
738-3 263-1 
725-7 274-2 
721-4 278-3 
516-8 360-3 
