146 Bodies more or lefs difpofedto Ignition. [Book II. 



According to the different properties of bodies, 

 they are more or lefs difpofed to ignition. Iron is 

 ignited with great difficulty ; on the contrary, not 



only 



air, which takes place from the decompofition of the nitre. Nitre 

 is compofed of a fixed alkali and of nitrous acid, which is itfelf a 

 compound of the bafes of azote and oxygen. The ingredient firft 

 inflamed is the fulphur, which fets fire to the charcoal. The nitre 

 is equally difperfed among all the particles of combuftible matter, 

 and as its quantity is by much the greateft, each particle of fulphur 

 and charcoal is furrounded with nitre. When combuftion, there- 

 fore, is once excited in the mafs, the oxygen afforded by the nitre 

 carries it on with great rapidity. The oxygen, being withdrawn 

 from the azote, caufes it to aflame an aeriform ftate, and by being 

 attracted by the charcoal converts the latter into fixable air. The 

 fulphur alfo attracting fome of the oxygen, but not fufficient to 

 reduce it to the ftate of a fluid, is partly converted into volatile 

 vitriolic acid, the fmell of which is very perceptible. The gun- 

 powder, therefore, is in an inftant converted into three kinds of 

 air, which occupy the fpace of the folid matter. What remains 

 after combuftion is a liver of fulphur formed by the union of fome 

 portion of that fubftance with the fixed alkali of the nitre. 



The efte&s, however, of this mixture of nitre, fulphur, and coal, 

 are trifling, in companion with thofe of another preparation called 

 fulminating powder, This is made by triturating in a hot marble 

 mortar, with a wooden peftle, three ounces of nitre, two ounces of 

 very dry fixed fait of tartar, and one ounce of flowers of fulphur, 

 till the whole is very accurately mixed. If a drachm of this pow- 

 powder is expofed to a gentle heat, in an iron ladle, it melts, and 

 foon after produces a detonation as loud as the report of a cannon.' 

 * This phenomenon, which is fo much the more aftonifhing, be- 

 caufe its efteft is produced without inclofmg the powder in any in- 

 ftrument, as is done with gunpowder, may be explained, by ob- 

 fcrving, I. That it does not fucceed, but by gradually heating ths 

 mixture, fo as to melt it. 2. That if fulminating powder is 

 thrown on ignited charcoal, it only detonates like nitre, but with 

 very little ncife. 3. That a mixture of liver of fulphur with nitre, 

 in the proportion of one part of the former, and two of the lat- 

 ter, fulminates with more rapidity, and produces as loud a report 

 as the composition of fulphur, nitre, and alkali : hence it appears, 

 that when fulminating powder is heated, liver of fulphur is formed 

 * before 



