i909] on Guncotton and Nitroglycerine. 437 



ably, a separating house, on artificial mounds, has to be resorted to, 

 entaihng a very considerable expense. 



In the next place, owing to the corrosive nature of the mixture 

 of nitroglycerine and waste acid, and to the acid nature of the nitro- 

 glycerine even when separated from the waste acid, the only material 

 which can be used for the cocks necessary to allow of the nitroglycerine 

 -and acid to run from vessel to vessel, is earthenware. Tlie'use of 

 earthenware cocks is attended with considerable risk, owing to the fact 

 that there is friction in them between the key and the body of the 

 €ock, and there is always the risk in moderately cold weather of the 

 nitroglycerine freezing and fixing the key : force, if used under these 

 circumstances, would be very liable to cause accident. Again, the 

 necessity of storing the waste acid under observation for long periods 

 is a costly one, both as regards labour and plant required. 



It was to overcome these disadvantages that the whole system in 

 current use for the manufacture of nitroglycerine received very care- 

 ful consideration at the Royal Gunpowder Factory some years ago. 



The first step that was taken to improve matters, w^as to abolish 

 the use of earthenware cocks in the preliminary and final washing 

 tanks. As the nitroglycerine when it was ready to leave these tanks 

 was thoroughly free from acid, it was possible to get rid of the cocks 

 on these tanks, and to replace them by rubber tubes. During the 

 washing operations this tube is secured to a nozzle fixed to the outside 

 of the tank at a point above the level of the liquid. To run off the 

 nitroglycerine it is only necessary to slip the rubber tube off the 

 nozzle and direct it into another vessel or into a lead gutter used to 

 convey the nitroglycerine to the next operation. 



Rubber, however, could not be used in the case of the separator 

 or the nitrator, where either acid nitroglycerine, or a mixture of nitro- 

 glycerine and acid had to be drawn off. To overcome the difficulty 

 in this case an entirely new system was invented at Waltham Abbey. 

 Instead of running the nitroglycerine and waste acid on completion 

 of the nitration process into the separator, the separation is allowed to 

 take place in the nitrating vessel itself. Nitroglycerine as it separates 

 from the waste acid comes to the top, it being the lighter of the two 

 liquids, and to remove it from the nitrator all that is necessary is to 

 raise the liquid contents of the vessel gradually until the nitroglycerine 

 reaches the top of the nitrator, where a pipe or gutter is fixed to lead 

 the nitroglycerine away into the preliminary washing tank. This 

 raising of the charge is effected by introducing into the bottom of the 

 nitrator, through the same pipe by which the nitrating acid is admitted, 

 the waste acid from a previous charge. The rate of inflow of the 

 waste acid is regulated so that the nitroglycerine displaced is as free 

 as possible from acid in suspension. 



The waste acid has still to be dealt with. It was discovered that 

 the addition of a small percentage of water to this acid, after the 

 nitroglycerine has been separated from it in the nitrator-separator, 



