1874.] on Fired Gunpowder. 419 



portions of total solid and gaseous matters, are the same as in the case 

 of powder fired in a close vessel. 



2. The work on the projectile is effected by the elastic force due to 

 the permanent gases. 



3. The reduction of temperature and pressure due to the expansion of 

 the permanent gases is, in a great measure, compensated by the heat 

 stored up in the liquid residue. 



4. The law connecting the tension of the products of explosion with 

 the volume they occupy is stated in equation (30). 



5. The work that gunpowder is capable of performing in expanding in 

 a vessel impervious to heat is given by the equation 



pp Q> _ 



and the temperature during expansion by the equation 



- 



/-t _ /-i 



-o 



6. The total theoretic work of gunpowder, when indefinitely expanded, 

 is about 332,000 gramme-metres per gramme of powder, or 486 foot- 

 tons per Ib. of powder. 



With regard to one or two other points to which the authors specially 

 directed their attention, they consider that their results warrant them in 

 stating that : 



1. Very small-grain powders, such as F. G-. and B>. F. G-., furnish very 

 decidedly smaller proportions of gaseous products than a large-grain 

 powder (R. L. Gr.) ; while the latter, again, furnishes somewhat smaller 

 proportions than a still larger powder (pebble), though the difference 

 between the total gaseous products of these two powders is compara- 

 tively inconsiderable. 



2. The variations in the composition of the products of explosion 

 furnished, in close chambers, by one and the same powder under different 

 conditions as regards pressure, and by two powders of similar composition 

 under the same conditions as regards pressure, are so considerable that no 

 value whatever can be attached to any attempt to give a general chemical 

 expression to the metamorphosis of a gunpowder of normal composition. ' 



3. The proportions in which the several constituents of solid powder- 

 residue are formed are quite as much affected by slight accidental varia- 

 tions in the conditions which attend the explosion of one and the same 

 powder in different experiments, as by decided differences in the compo- 

 sition, as well as in the size of grain, of different powders. 



4. In all but very exceptional results, the solid residue furnished by 

 the explosion of gunpowder contains, as important constituents, potas- 

 sium carbonate, sulphate, hyposulphite, and sulphide, the proportion of 

 carbonate being very much higher, and that of sulphate very much lower, 

 than is stated by recent investigators. 



