CAPTAIN NOBLE AND ME. P. A. ABEL ON FIEED GUNPOWDEE. 
137 
7. The tension of the products of combustion, when the powder fills entirely the 
space in which it is fired, is about 6400 atmospheres, or about 42 tons per square inch. 
8. The tension varies with the mean density of the products of combustion accord- 
ing to the law given in equation (3). 
9. About 705 gramme-units of heat are developed by the decomposition of 1 gramme 
of powder such as we have used in our experiments. 
10. The temperature of explosion is about 2200° C. (about 4000° F.). 
(5) When powder is fired in the bore of a gun, the results at which we have arrived 
are as follow : — 
1. The products of explosion, at all events as far as regards the proportions of the 
solid and gaseous products, 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 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 im- 
pervious to heat is given by equation (34), and the temperature during expansion is 
given by equation (31). 
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 lb. of powder. 
With regard to one or two other points to which we specially directed our attention 
in these investigations, we consider that our results warrant us in stating that : — 
1. Very small-grain powder, such as F. G. and It. F. G., furnish decidedly smaller 
proportions of gaseous products than a large-grain powder (R. L. G.), while the latter 
again furnishes somewhat smaller proportions than a still larger powder (pebble), though 
the difference between the gaseous products of these two powders is comparatively 
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 variations in the conditions which 
attend the explosion of one and the same powder in different experiments as by decided 
differences in the composition 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, potassium carbonate, sulphate, hypo- 
sulphite, and sulphide, the proportion of carbonate being very much higher, and that 
of sulphate very much lower than stated by recent investigators. 
MDCCCLXXV. T 
