VOL. LXIX.] PHILOSOPHICAL TRANSACTIONS. 551 



As, in the foregoing experiment, the compound of inflammable and common 

 air was reduced above the half of its former bulk, it seems more than probable, 

 that the quantity of dephlogisticated and inflammable air extricated in the firing 

 of gunpowder must also undergo a similar diminution by its inflammation ; so, 

 that when there remains a mass of air, 250 times the bulk of the gunpowder, 

 the quantity of air extricated from die powder must have been in reality not less 

 than 500 times the bulk of the powder, which agrees nearly with the calculation 

 of Mr. John Bernouilli. Let us now see how far this computation agrees with 

 the analysis of gunpowder. Abbe Fontana, so advantageously known by his 

 important discoveries in natural philosophy, more especially by those he has made 

 on the various kinds of air, favoured me with the following result of his experi- 

 ments. An ounce of nitre, exposed to a great degree of heat for the purpose 

 of extracting its air in the usual way, yielded about 800 cubic inches of dephlo- 

 gisticated air. An ounce of charcoal, treated in the same way, gave about J 50 

 cubic inches of air, partly fixed, partly inflammable, mixed with some common 

 air. 



Let us now calculate, without however being too scrupulous about the accu- 

 racy of the result, what quantity of elastic permanent fluid a cubic inch of solid 

 gunpowder will give in the moment of deflagration : a cubic inch of solid gun- 

 powder contains in weight 442 grains (which is 38 grains short of an ounce 

 Troy weight) of which 331-l grains is nitre, 55^ charcoal, and as much sulphur ; 

 supposing the proportion of the ingredients of the powder to be 6 parts of nitre 

 to 1 of charcoal and 1 of sulphur; 33 li grains of nitre will give about 552 

 cubic inches of dephlogisticated air ; 55^- grains of charcoal will produce about 

 17 cubic inches of air, chiefly inflammable, according to the calculation of 

 Abbe Fontana. 



By this calculation, which will, perhaps, be found more accurate than the 

 former, one cubic inch of solid gunpowder will yield above 569 cubic inches of 

 permanent elastic fluid : I say, above 569 cubic inches, for I do not put into the 

 account the elastic fluid which is generated by the sulphur, nor that which char- 

 coal, consumed by the inflammation of the gunpowder, yields above the quantity 

 mentioned, which it gives when heated in a glass vessel, by which it is by no 

 means consumed, an ounce losing by this operation only 60 grains of its weight. 

 As this elastic fluid will increase to 4 times its bulk, it follows, that 1 cubic inch 

 of solid gunpowder will extricate in the moment of explosion above 2276 cubic 

 inches of elastic air. Which computation is not far from the result of my 

 former calculation, and that of Mr. Bernouilli. 



An accurate calculation of the expansion of gunpowder * would be a very 



* This is probably most accurately calculated in prob. 17, vol. Q, of Dr Hutton's Course of 

 Mathematics, p. 345, &c. 5th edition j as deduced by accurate and numerous military experiments. 

 The expansion there deduced, in the conclusion of that problem, p. 353 j is nearly 2000 times. 



