CAPTAIN NOBLE AND MB. E. A. ABEL ON EIRED GUNPOWDER. 
81 
above referred to were on the whole remarkably uniform, the composition of the solid 
residues exhibited comparatively great variations. Certain general results appear, 
however, to be well established by a number of the analyses. Excluding again those 
experiments conducted at the lowest pressure, the proportion of potassium sulphate 
produced in the several experiments, with the comparatively slow-burning pebble 
powder, was remarkably uniform at various pressures, being, as already pointed out, 
not more than one fourth the amount found in powder-residue by Bunsen and 
Schischkofe. The proportion of sulphur not actually entering into the principal 
reactions involved in the explosion of the powder was also, with two exceptions, very 
uniform, being about 35 per cent, of the total amount contained in the powder. The 
proportion of potassium carbonate obtained from pebble powder was somewhat less 
uniform, but did not differ greatly in the different experiments with the same powder 
exploded in different spaces, excepting at the highest pressure. With the more rapidly- 
exploding R. L. G. powder, the sulphate formed at the lower pressures was nearly double 
that obtained with pebble powder ; while at the highest pressures the amounts furnished 
by the two powders did not differ greatly, the amount of sulphur excluded from the 
chief reaction at those pressures, with R. L. G., being, however, more considerable 
than was the case with pebble powder under similar conditions. With regard to 
this part of the sulphur contained in the powder, which corresponds to what Bunsen 
and Schischkoff term free sulphur, some portion of it almost always exists, not in 
combination with potassium as polysulphide, but combined with iron, and is therefore 
discovered in the residue left undissolvecl, upon treatment with water, of the solid 
products removed from the chamber. This proportion of the sulphur is evidently at 
once fixed, at the instant of explosion, by union with parts of the metal surfaces 
presented by the interior of the vessel in which the operation is conducted. The 
extent to which sulphur is thus abstracted from the powder-constituents, and precluded 
from entering into the reactions which are established by the explosion, or follow 
immediately upon it, must depend in some degree upon accidental circumstances, such 
as variations in the mechanical condition (smoothness, brightness, &c.) of the metal 
surfaces, and also upon the temperature developed at the instant of the explosion. 
The circumstance that, in the statement of the results of Experiment 42, both potas- 
sium oxide and sulphur are separately included is therefore explained by the above 
fact. The larger proportion of the “ sulphur ” specified in the several analyses existed 
as potassium polysulphide, and may therefore be styled free sulphur, as it did not take 
part in the chief reactions. 
The carbonate , like the sulphate, differed decidedly in amount in the residues 
furnished by the R. L. G. powder exploded in the smaller and the larger spaces : in 
the former it was equal to the lowest result furnished by the pebble powder ; in the 
others its proportion was about 10 per cent, higher than in the pebble-residues, excepting 
in one of them produced at the highest pressure. In the products obtained by the 
explosion of the smallest-grain powder (F. G.) the variations in the proportions of 
MDCCCLXXV. M 
