Freezing of nitroglycerine

The heat of crystallization (freezing) of nitroglycerine has been determined by many authors (Nauckhoff [18], Beckerhinn [44]). The most complete investigations were those performed by Hibbert and Fuller [46] who have established the following data ... 

The specific heat of nitroglycerine is 1.49 J/g. The specific heat of its crystal (stable form) is 0.315 cal/g. The specific heat of liquid nitroglycerine is 1.318 J/g. The crystallization heat (freezing) of nitroglycerine is listed in Table 5.42. 

From this table it is evident that the application of the curves derived for mixtures of the pure compounds to the interpretation of values obtained on Dynamite extractives would give results indicating a proportion of Nitroglycerin much higher than that actually present. It is also apparent that the oils, fats, and resins present in Dynamite extractives cannot be removed entirely by freezing, as was recommended by Marqueyrol Goutel... 

There are two modifications of nitroglycerine, differing in freezing point and crystalline forms. With respect to crystal structure the form melting at the lower temperature represents a labile form (Fig. 6) which can be transformed spontaneously into the higher melting stable form of nitroglycerine (Fig. 7). 

Freezing points for both variations of nitroglycerine, as published in different papers, are collected in Table 6. 

The freezing points of blends of nitroglycerine and nitroglycol have been investigated by Avogadro di Cerrione [30] who established experimentally that both substances can be dissolved in any quantitative ratio to form the following eutectic mixtures ... 

Temperatures below 12°C are not usually used, since crystallization of nitroglycerine could take place. Lower temperatures (e.g. 5-7°C) can be applied only when a mixture of glycerine with glycol or diglycerol is nitrated and if there exists no fear that the mixture of esters resulting from the reaction can freeze. In factory practice, nitration is performed mainly at temperatures of about 20-25°C or at 25-30°C. The temperature is measured by means of at least two thermometers, immersed in the vessel at different depths. 

The problem of lowering the freezing point of nitroglycerine has been solved in many ways. Most of these methods are now of historical interest only, since they involved the use of substances which either weakened the explosive power of the nitroglycerine significantly or increased the price of product appreciably. 

The explosion of this mixture which was proposed by Vender [22] as an additive to nitroglycerine in the manufacture low-freezing dynamites produces approximately 90% of the explosive power of nitroglycerine. 

This is another explosive suggested by Vender [22] for lowering the freezing point of nitroglycerine. 

Nitrostarcli manufactured by the Trojan Powder Co. German patent for use of glycol dinitrate to lower freezing point of nitroglycerine. 

Use and exposure Ethylene glycol dinitrate, also called nitroglycol, is a colorless to yellow, oily liquid. It reacts with acids and is used in the manufacturing of explosives to lower the freezing point of nitroglycerin, in order to produce dynamite for use in colder weather. 

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