1909] on Guncotton and Nitroglycerine. 485 



means of a power-driven wooden paddle-wheel, and then allowed to 

 settle. The washing water containing the impurities is drawn off from 

 the surface of the guncotton by means of a large skimmer, in order 

 that not only impurities in solution may be removed, but also any 

 light solid impurities in suspension. 



The finally purified pulp is passed to a moulding machine, where 

 it is lightly compressed to remove the bulk of the water, and converted 

 into a form in which it can be easily handled. If intended for 

 use in mines or torpedoes, or for demolition purposes, the lightly 

 compressed shapes are submitted to heavy hydraulic pressure, con- 

 verting them into dense hard blocks. 



The other high explosive of which I am to speak, viz., nitro- 

 glycerine, enters into the composition of many modern propellants. 

 Nitroglycerine was discovered by So])rero in 1^47, but it remained 

 for a long time a chemical curiosity only. 



Alfred Nobel commenced its manufacture as a blasting agent, 

 about 186<S, for which purpose he absorbed nitroglycerine with an 

 infusorial earth, known as kieselguhr, and gave the compound the 

 name of dynamite. But, prior to this, nitroglycerine had been made 

 on a large scale in America, where it was frozen after manufacture, 

 for purposes of transport, and used for blasting. 



Nitroglycerine is a liquid, and is a much more violent explosive 

 than guncotton, and whereas the manufacture of guncotton is absolutely 

 safe throughout, that of nitroglycerine is dangerous. The risks at- 

 tendant on the manufacture of nitroglycerine are due to the facts that 

 the temperature resulting from the chemical reaction is not so easily 

 controlled, and that nitroglycerine, being a liquid insoluble in water, 

 the processes after nitration have to be carried out with a substance 

 not rendered inert, as guncotton is, by admixture with water. For 

 these reasons the nitration of glycerine in the early days of the pro- 

 duction of nitroglycerine on a manufacturing scale was carried out in 

 very small quantities. 



With the introduction of dynamite, the small pots used for the 

 nitration of glycerine, standing in vessels full of ice water, were 

 replaced by lead tanks in w^hich considerable quantities of glycerine, 

 amounting to several hundred pounds, were nitrated at one opera- 

 tion. In these vessels the temperature was controlled by means of 

 cold water circulating through lead coils fixed in the tank, and the 

 whole contents of the tank were kept in agitation during the nitra- 

 tion by means of mechanical stirrers, or by compressed air escaping 

 through small holes in lead pipes situated at the bottom of the 

 nitrating vessel. On completion of the nitration it was the practice 

 in the early days to drown the whole of the charge of nitroglycerine 

 and waste acid in a large bulk of water, from which the nitroglycerine 

 separated out and was removed for subsequent purification by 

 washing with alkaline solutions in lead tanks. This system entailed 

 the loss of the waste acid, and was superseded by a process in which 



