1867.] 



Presidenfs Address. 



173 



be counteracted by very simple means, which in no way interfere with the 

 essential qualities of the material. All ordinary products contain small 

 quantities of organic (azotized) impurities, which are comparatively unstable. 

 It is the presence of these impurities in ordinary gun-cotton which gives 

 rise to the development of free acid when the substance is exposed to a high 

 temperature ; and the acid thus generated may eventually exert a destruc- 

 tive action upon the pure portion of the mass (or true gun-cotton), and thus 

 establish a decomposition which is materially accelerated by heat. Mr. Abel 

 has, however, arrived at the important practical conclusion that this mis- 

 chief can be averted by neutralizing the acid as it is liberated ; and this is 

 readily effected by distributing through the finished gun-cotton a small 

 quantity, say one per cent., of carbonate of soda. By adopting this precau- 

 tion, damp gun-cotton may be stored, closely packed, in large quantities, 

 and may be exposed to a heat equal to 212'^ Fahrenheit in confined spaces 

 for long periods, without undergoing any alteration. The introduction into 

 the finished gun-cotton of one per cent, of carbonate of soda affords, there- 

 fore, security to the material against any destructive effects of the highest 

 temperature to which it is likely to be exposed, even under very exceptional 

 climatic conditions. 



Actual immersion in water is not necessary for the most perfect preser- 

 vation of gun-cotton. The material, if only damp to the touch, does not 

 sustain the smallest change even if closely packed in large quantities. If 

 as much water as possible be expelled from wet gun-cotton by the centri- 

 fugal extractor, the cotton is obtained in a condition which, though only 

 damp to the touch, is perfectly non-explosive. It is therefore in this con- 

 dition that all reserve stores of the substance should be preserved, and that 

 it should be transported to distant places. The proper proportion of the 

 carbonate of soda may be conveniently introduced by being dissolved in the 

 water by which the gun-cotton is wetted. 



It is in this immunity from danger in storage and in transport that pro- 

 perly prepared gun-cotton possesses so great an advantage over gunpowder. 



Mr. Abel has also elaborately investigated the efi'ects of various kinds of 

 defective preparation of gun-cotton, combined with systematically varied 

 circumstances of exposure to heat, moisture, and light of the products so 

 obtained. It is seen by these investigations that modifications in the pro- 

 cesses of conversion and purification, which appear at first sight of a very 

 trifling nature, exert most important influences on the composition and 

 purity, and consequently on the stability, of the product. It is shown by 

 Mr. Abel that to such causes are to be attributed the conclusions con- 

 demnatory of gun-cotton which had been drawn by foreign chemists of con- 

 siderable note. 



.The distrust, not unreasonably entertained at the time, of the stability of 

 the material, was a principal cause of the desire on the part of Her Majesty's 

 Government to refer the subject of gun-cotton to a Committee which should 

 include some scientific members taken from the Royal Society. This great 

 and primary question being now satisfactorily solved, the remaining secondary 



