1880.] 



Fired Gunpowder. 



203 



In reference to the foregoing numerical statements, we have to offer 

 the following observation : — 



1. Substituting zinc chloride for copper oxide as the precipitant 

 of the sulphur which existed in the form of sulphide in solutions of 

 powder residues to which air had not had access at all, until the time 

 of its treatment with the zinc chloride, the amount of hyposulphite 

 existing in solution after such treatment was found to range from 

 0*05 to 0'78 in 100 parts of gunpowder, while the treatment of por- 

 tions of the same solutions with copper oxide, in the precise manner 

 adopted in our series of experiments, yielded proportions ranging from 

 1*38 to 2"39 per 100 of powder used. Comparing the results furnished 

 by the two modes of treatment, it will be seen that in the case of the 

 parallel experiments (245), which exhibited the least considerable 

 difference in the amount of hyposulphite found, that existing after the 

 copper oxide treatment was about sixteen times greater, while in the 

 case of the highest difference (Experiment 241) it was about thirty- 

 four times greater than that found after the treatment with the zinc 

 chloride. 



2. It would appear from these results that, in four or five out of 

 seven experiments, no hyposulphite, or at any rate only minute 

 quantities, existed in the residues previous to their solution, and 

 although it would seem to have existed in very appreciable amount 

 in two out of seven residues, the highest proportion found after the 

 zinc chloride treatment was less than one-half the lowest proportion 

 found in our complete series of analyses in which the copper oxide 

 treatment was adopted. 



3. A comparison of the results among each other leads, therefore, to 

 the conclusion that potassium hyposulphite cannot be regarded as a 

 normal constituent of powder residue (obtained in experiments such 

 as those carried out by us), and that M. Berthelot is correct in re- 

 garding this salt as an accidental product, which, if existing occa- 

 sionally in appreciable amount in the solid matter previous to its 

 removal from the explosion vessel, is formed under exceptional con- 

 ditions, and then only in comparatively small proportions. 



While submitting this as the conclusion to be drawn from our most 

 recent experiments, we are of opinion that the following points 

 deserve consideration in connexion with the question whether hypo- 

 sulphite may not, after all, occasionally exist, as the result of a 

 secondary reaction, in comparatively large proportion in the explosion 

 vessel before the residue is removed. 



It will be observed that although the copper oxide treatment, when 

 applied to the sulphide in the pure condition (i.e., undiluted with the 

 other potassium compounds found in powder residue), gave rise 

 to the production of very large proportions of hyposulphite, when 

 polysulphides were used, the highest proportion of that substance 



