204 



Capt. Noble and F. A. Abel. 



[Mar. 4 r 



found, after the treatment of the particular residues used in the ex- 

 periments given in Table I, only amounts to 2*82 per cent, upon the 

 gunpowder (pebble powder) employed, which corresponds to about 

 14*5 per cent, of the average proportion of monosulphide existing in 

 the residue furnished by that powder. In observing this, it must 

 be borne in mind that the sulphide existing in powder residue is 

 always present, in part, and sometimes to a considerable extent, in 

 the form of polysulphide, also, that the experiments with the sul- 

 phides were conducted precisely according to the method pursued in 

 the treatment of the powder residues. It would appear, therefore, 

 as though the mixture of the sulphide with a very large proportion 

 of other salts in solution rendered it less prone to oxidation by the 

 copper oxide than when the undiluted sulphide is submitted to its 

 action. 



In comparing with the results furnished by the zinc chloride those 

 obtained by the copper oxide treatment, in the special experiments 

 given above, it is observed that, omitting one exceptional result 

 (No. 241) for which we do not attempt to account, the highest pro- 

 portions of hyposulphite are furnished by those residues which also 

 gave the highest with the zinc chloride, the differences between the 

 results furnished by the two treatments being likewise the highest in 

 these three cases ; so also the lowest proportions furnished by the copper 

 oxide treatment, correspond to the lowest obtained with the zinc 

 oxide, and the differences between the results furnished by the two 

 methods are in the same manner the lowest in these. It would almost 

 appear, therefore, as though the existence of a very appreciable pro- 

 portion of hyposulphite in the solution of the residue had some effect 

 in promoting the production of hyposulphite when the residue is sub- 

 mitted to treatment with copper oxide. 



In a recalculation of the results of our analyses of the powder 

 residues upon the assumption that the whole of the hyposulphite 

 obtained existed originally as monosulphide, it is found that, in 

 several instances in which the proportion of hyposulphite was high, 

 the analytical results are much less in accordance with each other 

 than when it is assumed that the hyposulphite found, or at any rate a 

 very large proportion of it, existed as such in the residue before 

 removal from the explosion vessel. Thus, taking the E.Gr. series, in 

 which the mean quantity of hyposulphite actually found is about double 

 of that obtained either from the pebble or R.L.Gr. powders, select- 

 ing from this series the three experiments which gave the highest 

 proportions of hyposulphite, and calculating in the manner described 

 in our first memoir the total quantities both of solid and gaseous pro- 

 ducts, first from the basis of the analysis of the solid products, secondly 

 from the basis of the analysis of the gaseous products, and further on 

 the assumption that the hyposulphite found existed as hyposulphite 



