4?.4 Colonel Sir Fredprir L. Nathan [Jan. 29, 



cess. It consisted in snbjecting the guncotton, while still in the 

 waste form, to a series of steam boilings in large wooden vats. In 

 the early days of this process boilings of long duration were used 

 throughout. Later, a system was introduced in which a large 

 number of short boilings at the commencement, was followed by a 

 couple of final long boilings. With the introduction of t!ie displace- 

 ment process of nitration, a thorough investigation of the chemistry 

 of the boiling process w^as undertaken at Waltham Abbey, and as a 

 result it was ascertained that a more rapid purification was effected 

 by means of two long boilings, each of twelve hours duration, 

 followed by a series of very much shorter ones. 



It is very proljable that the displacement system of nitration is 

 itself responsil)le for the reduction in the amount of boiling required 

 to produce a stable guncotton. Although there is no appreciable 

 amount of mixing taking place between the displacing water and 

 the waste acid, still mixing at the surface of contact does occur to a 

 slight extent, sufficient to produce a distinct rise of temperature. 

 The zone of Avarm acid liquid produced passes very slowly through 

 the whole of the guncotton, removing in its course various impurities. 

 The purifying action of this liquid is no doubt due to the fact that 

 it possesses strong oxidising and solvent properties. 



The pulping process introduced by Abel is still universally em- 

 ployed, and although its value from a purification point of ^iew is no 

 longer of such great importance now that guncotton is boiled, as it 

 was in the early days of cold water washing, it is, undoubtedly, still 

 of use in effecting a final purification of the guncotton. 



In the beating engine, the mechanical process of reducing the 

 guncotton to a pulp is effected, but no actual removal of impurities 

 takes place, Ijecause the water is not changed during the operation. 

 The impurities still present in the guncotton at this stage are both 

 mechanical and chemical. The mechanical impurities consist chiefly 

 of particles of metal of various kinds, sand and fine grit, wood and 

 similar substances, introduced originally in the cotton waste and 

 during the processes of manufacture. The chemical impurities are 

 bodies produced by the action of the nitrating acid on bodies otlier 

 than cellulose ; they are not entirely removed in the boiling process, 

 but are set free in the pulping. To remove the mechanical impurities 

 the guncotton pulp in a large volume of water is at AValtham Abbey 

 run from the beaters over flannel laid on long shallow troughs, the 

 troughs having pockets with baffle plates at intervals. The rough 

 .surface of the flannel retains the fine particles of grit, etc., and the 

 larger particles settle in the pockets or grit-traps. In the last pocket 

 an electro-magnet is inserted to remove iron or steel particles, which 

 may have escaped retention in the grit-traps. 



The guncotton thus freed from mechanical impurities runs into 

 large oval iron tanks, called " poachers," where it receives several 

 cold water washings. The contents of the poacher are agitated by 



