On the properties and uses of Gun-cotton. 109 



acid had any bleaching power separately : but, upon pouring a co- 

 loured liquid (indigo ?) into the mixture, the colour was discharged 

 as readily as if chlorine had been present. Again, the action of this 

 compound on sugar was widely different to that of either nitric or 

 sulphuric acid. Thus, by digestion in it, sugar became converted to 

 a kind of yellow resin : it was no longer soluble in water, but quite 

 soluble in alcohol, forming on evaporation a kind of varnish. It took 

 fire at a low temperature, and burnt like a resin, with a yellow 

 smoky name. Experiments were performed to illustrate these pro- 

 perties. The most remarkable effects were, however, produced when 

 any form of lignin or woody fibre was immersed in the mixture. 

 The chemical properties of the substance were entirely changed, 

 although, in appearance, it was but little altered. Tow, saw-dust, 

 linen, or paper, might be used ; but no substance was so well fitted 

 for the purpose as finely carded cotton wool. All that was required 

 was to soak the cotton wool, well pulled out, in a vessel containing a 

 large quantity of the acids, in the proportions above-mentioned. 

 When fully impregnated with the mixture, the cotton was to be 

 removed, or it would in time become dissolved : it should then be 

 transferred to water, and washed until no trace of acidity remained 

 about it. It should be dried at a gentle heat, and it was then fit for 

 use. [Some of the cotton was here prepared by the Professor.] 



It was difficult to give a satisfactory theory of the change produced 

 in the cotton. Lignin consisted of C12, H8, 08 : it was, no doubt, 

 oxidized during the process, but, whether by the action of a new 

 principle formed (ozone), or by the mere transference of the elements 

 of nitric acid to it, it was difficult to say. Nitrous acid might be 

 obtained from it by distillation. The cotton was considerably in- 

 creased in weight ; 100 parts of the wool yielding 160 parts of gun- 

 cotton. When well prepared, it was white and flocculent, and, to all 

 appearance, unchanged physically ; but the microscope showed a 

 peculiar difference ; for whereas the fibre of ordinary cotton, when 

 polarized in the microscope, had a certain lustre, the fibre of gun- 

 cotton appeared in the form of a black streak. 



The prepared cotton, when heated to about 350°, was entirely re- 

 solved into gaseous matter with flame ; and if confined, it exploded 

 with a loud report. It became inflamed at a temperature much 



