CAPTAIN NOBLE AND MR, F. A. ABEL ON FIRED GUNPOWDER. 
211 
odour of sulphuretted hydrogen, distinctly perceptible at the sealed surfaces of the 
mouths, indicated a slight imperfection in the sealing of the bottles. 
The difficulties in the way of reducing to a minimum the exposure to air of the 
residues during their detachment from the explosion-vessel were, however, very much 
greater. We pointed out in our first memoir that in almost all cases the residues 
were in the form of exceedingly hard and compact masses, which had to be cut out 
with steel chisels, and that, although portions of the mass were detached in the form 
of lumps, a considerable amount of it flew off before the chisel in fine dust. The 
utmost care was taken to avoid exposure of the detached residues to the air, but it 
was of course impossible to avoid their being more or less attacked by atmospheric 
oxygen during the period of their collection. There is no doubt, moreover, that the 
residues, which differed greatly from each other in structure and in their tendency to 
absorb moisture and to become heated upon exposure to air, were susceptible in very 
variable degree to atmospheric oxidation. We, therefore, are quite prepared to admit 
that, of the large amount of hyposulphite found in a number of the analyses, a pro¬ 
portion, and in some instances possibly a large one, may have been produced by the 
agency of atmospheric oxygen during the removal of the residue from the appa¬ 
ratus ; and the results of some special experiments, which we shall presently quote, 
appear to favour the conclusion that in those instances where no sulphide was dis¬ 
covered, its absence may have been ascribable to atmospheric oxidation. We regret 
having neglected to make any reference to this probable source of error in describing 
the results of our analyses, our belief being at the time that any important alteration 
of the residue by atmospheric action was sufficiently guarded against; at the same 
time, it is right we should point out that, in several instances in which the circum¬ 
stances attending the manipulation of the solid residue and its consequent mechanical 
condition were apparently most favourable to its accidental oxidation, the proportion 
of hyposulphite formed was comparatively moderate in amount. 
On the other hand, we cannot concur in M. Berthelot’s view that the existence of 
hyposulphite among our analytical results is also ascribable in part to accidental 
oxidation of potassium sulphide during the analytical manipulations. These were 
carried out with great uniformity so far as certain preliminary operations were con¬ 
cerned, which consisted, firstly, in dissolving the residue in water which had been 
carefully boiled to expel air, and, secondly, in filtering the solution in closed vessels— 
both of these being rapidly completed operations. The receiving vessel contained 
pure ignited cupric oxide, with which, as soon as the filtering operation was completed, 
the solution was agitated until it became colourless. 
The fact that in some of the analyses, all of which, we repeat, were uniformly 
conducted in regard to the above points, from 3 to 10 per cent, only of hyposulphite 
were found, while the proportion of monosulphide in these analyses ranged from 7 to 
19 per cent, (being above 9 per cent, in eight instances), appears to afford substantial 
proof that accidental atmospheric oxidation during the collection and analysis of the 
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