CAPTAIN NOBLE AND MR. F. A. ABEL ON FIRED GUNPOWDER. 
223 
(3) A comparison between the weights of the elementary substances found in the 
products of combustion and the weights of the same elements found in the 
powder prior to ignition. 
(4) The weight of oxygen contained in the total quantity of hyposulphite found. 
An examination of this statement will show how closely accordant the various 
analyses are as a whole ; but in estimating the degree of accuracy attained, the following 
points must carefully be borne in mind. 
1. That in the very large quantity of powder used, slight variations in its composition 
(as indeed have been found) were sure to exist. 
2. That we have adopted as one of the data of our calculations the average quantity 
of gas found to be produced by the explosion. But, as we have elsewhere pointed out, 
our investigations seem to prove that exceedingly slight and inappreciable variations 
in the circumstances of explosion give rise to very notable changes in the products, 
and among others in the amount of gaseous products. Any change in this direction 
would of course affect the accordance of the analysis in which the abnormal decom¬ 
position occurred. 
A review of the comparison between the weight of oxygen originally in the powder, 
and the weight found in the products of explosion, appears to show that there is in the 
former, on the average, a very appreciable excess of oxygen. Hence it may pretty 
fairly be concluded that a portion of the hyposulphite found is due to the oxidation of 
the monosulphide after removal from the explosion-vessel. 
On the other hand, a reference to those analyses in which hyposulphite exists in large 
proportion, shows that were we to assume the whole of the hyposulphite as formed 
after the removal of the products from the cylinders, there would exist a deficiency 
in oxygen much larger than the existing excess. Hence we may equally fairly, from 
this line of argument, conclude that it is impossible to attribute to accidental causes 
the formation of the whole of the hyposulphite, and that a considerable proportion 
of it must be looked on either as a primary or secondary product. 
We now pass to the question of the amount of heat generated by the combustion of 
gunpowder, and in so doing we may remark that we were fully cognisant of the incon¬ 
veniences inseparable from the form of apparatus used by us for this purpose and 
described in our first memoir.* In fact, the errors likely to arise from its use were 
very exactly pointed out by ourselves,! and we were quite aware of the great advantages 
in regard to saving of time and labour, and to accuracy, that would result from the 
use of apparatus similar to that which we shall presently describe. 
But the apparatus, such as it was, was deliberately adopted, because at the time 
when these experiments were made we could not be sure that the decomposition 
experienced by gunpowder in its explosion when fired in considerable quantities and 
under tensions similar to those existing in the bores of guns was by any means the 
same as that occurring when it is fired in small quantities and under feeble tensions, 
* Phil. Trans. 1875, Part I., p. 63. f Loc. tit., same page. 
