Separation of nitroglycerine from acid

Normal separation of phases should be complete in 20-30 min. However, under 

Much experimental work designed to accelerate the separation of nitroglycerine from spent add has been carried out. It has been established that the separation can be hastened in several ways  

In the second case it is possible to take advantage of the resulting hydrofluoric acid by addition of silica to produce further quantities of silicon fluoride. As reported in the patent, to a 150-200 kg charge of glycerine approaching the end of nitration, about 30 g of a mixture composed of sodium fluoride and silica are added. If the addition is made too soon its effect is lost, since the SiF4 is carried away by the air stream and removed from the system. 

Other proposals have also been published, e.g. the suggestion of Westphalisch-Anhaltische factory [13] to add 0.02-0.05% of talc. Another way of hastening the separation is found in a patent of Carbonit A.G. in Hamburg [14], wherein additions of about 1% urea, acetamide or dicyandiamide (calculated in relation to glycerine) to the mixed acid are recommended. In contact with acid these substances decompose to form gaseous products which hasten separation in the same way as silicon fluoride. 

The quantitative effect of various additives on the rate of separation of nitroglycerine from spent add has been determined by Moisak and Grigoryev [15]. They found that in the presence of 0.5% ferric sulphate or lead sulphate, the separation rate is halved. Further, they established that the separation rate is related to the composition of the spent acid. The maximum rate of separating was achieved by using add composed as follows  

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Separation of nitroglycerine from acid Purification of nitroglycerine Filtering nitroglycerine Transport of nitroglycerine Recovery of stabilizing water The spent acid... 

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