﻿40 Dr. L. Bleekrode on a curious Property of Gun-cotton. 



make the following quotation : — " These results indicate that 

 if, even for the briefest space of time, the gases resulting from 

 the first action of heat on gun-cotton upon its ignition in open 

 air are impeded from completely enveloping the burning extre- 

 mity of the gun-cotton twist, their ignition is prevented ; and 

 as it is the comparatively high temperature produced by their 

 combustion which effects the rapid and more complete combus- 

 tion of the gun-cotton, the momentary extinction of the gases, 

 and the continuous abstraction of heat by them as they escape 

 from the point of combustion, render it impossible for the gun- 

 cotton to continue to burn otherwise than in the slow and im- 

 perfect manner, undergoing a transformation similar in character 

 to destructive distillation." 



In the same paper are described numerous experiments to 

 prove the accuracy of this statement ; and these were made with 

 compact gun-cotton twist burning in the open air, in a vacuum, 

 or enclosed in narrow tubes ; I think that the combustion when 

 the cotton is moistened with CS 2 or any other volatile substance 

 proves it in a most direct and very satisfactory manner. By 

 enclosing a small quantity of the moistened substance in the 

 aperture of a glass tube open at both ends and then igniting it, 

 some of the gases resulting from the destructive distillation may 

 be collected, among which nitrous acid is easily detected by its 

 characteristic odour. 



It was also remarked by Professor Abel that gunpowder, 

 when ignited under the same conditions as gun-cotton, behaves 

 in a different way : for example, a piece of gunpowder weighing 

 14 grains was placed in an apparatus wherein the pressure of air 

 was equal to 0*65 inch of mercury; when in contact with a wire 

 heated to redness it emitted first vapours of sulphur, and after 

 the lapse of three minutes the powder deflagrated. The same 

 facts present themselves when gunpowder is spread on a disk 

 and moistened with CS 2 ; as it burns, the gunpowder does not 

 immediately explode, but some time afterwards; yet it is always 

 a true explosion, caused by the chemical action between the char- 

 coal and the fused saltpetre, whilst the sulphur is already sub- 

 limed*. 



The above-described experiments afford a striking illustration 

 of latent heat for the lecture-table; and I may add in this respect, 

 that when a small piece of phosphorus is placed in the moistened 

 mass of gun-cotton, during the combustion this substance is 

 melted, and even boils, but does not burn, as it is prevented from 

 contact with oxygen till all the gun-cotton has disappeared. 



And, to conclude, it may be perhaps of use to remark that, 

 by keeping gun-cotton in a flask under a layer of benzine or 

 * Professor Abel, he. cit. p. 212. 



