48 



weak, or the temperature be allowed to rise, a second 

 product is formed to which the name " collodion cotton" has 

 been given. It has, as I show, a much less rapid ^rate of 

 ignition, and has comparatively feeble explosive properties, 

 but is of much use when dissolved in a mixture of Ether and 

 Alcohol (in which true gun-cotton is insoluble) for coating 

 glass plates, on which is afterwards deposited the film of 

 silver salts, sensitive to light, and used as photographic 

 plates. 



The cotton wool after treatment with acids, as shown, is 

 removed and washed with water until all traces of acid are 

 removed, an operation which is performed in the manu- 

 facture of gun cotton, with the greatest care, for reasons 

 stated immediately. 



The early history of the manufacture of gun cotton in 

 this country was most disastrous, numerous explosions 

 taking place, owing to the spontaneous decomposition of 

 the manufactured gun cotton. It is almost beyond doubt, 

 that these were occasioned by free acid being left behind in 

 the gun cotton — owing to imperfect washing — and under 

 these conditions, decomposition took place, and heat being 

 evolved in the centre of a mass of low conducting power, the 

 temperature rose until the mass was finally raised to the 

 point of ignition. 



These disastrous explosions checked for a time the 

 manufacture of gun cotton, but experiments were carried on 

 in Austria by Baron Von Lenk, chiefly with a view to 

 modify the rate of combustion of gun cotton, and thus 

 render it a safe substitute for powder. 



These experiments of Von Lenk, although apparently 

 unsuccessful, revived the subject in England, experiments 

 being made by Sir F. Abel, Chief Chemist at Woolwich, 

 resulting ultimately in the adoption of a method of manu- 

 facture, whereby a complete purification from free acid is 

 obtained, and the gun cotton is converted by pressure into 

 compact homogeneous masses. 



I will not enter into the details of manufacture observed 



