Nitroglycerine decomposition temperature

R. Robertson [62] examined the decomposition of nitroglycerine at temperatures from 90 to 135°C, using a carbon dioxide stream to remove volatile decomposition products. The concentration of nitrogen oxides in the jet of carbon dioxide was established spectrographically. He found in this way that nitroglycerine decomposed in a manner similar to that of fairly well stabilized nitrocellulose, but more rapidly. In the temperature range of 95—125°C, every 5° elevation of temperature doubled the decomposition rate in these conditions. 

The reason why wet nitroglycerin starts the autocatalytic reaction later than dry nitroglycerin at the same temperature is not explainable herein. There may, however, exist some difference, in the mode of the decomposition reaction during the induction period of the autocatalytic reaction of nitrate esters, betw een the liquid water which may be present in wet nitroglycerin at temperatures near 55 °C and the aqueous vapor which may be present in wet collodion cotton at temperatures near 80 X. ... 

The heat resistance of glycerine dinitrate is better than nitroglycerine. In the Abel test, the decomposition phenomenon only can be observed at set temperature for 16 days. At 150 °C, brown nitrogen oxide can be released. Its explosive decomposition temperature is above 170 °C. 

The mixture of 0.3 g nitroglycerine and 5 % nitric acid in a closed glass tube at 42 °C for 6 h will explode. The plot of the decomposition temperature of nitroglycerine catalyzed by nitric acid versus time is shown in Fig. 5.14. 

The approach taken in the development of an analytical model for the combustion of double-base propellants has been based on the decomposition behavior of the two principal propellant ingredients, nitrocellulose and nitroglycerin. The results of several studies reviewed by Huggett (HI2) and Adams (Al) show that nitrocellulose undergoes exothermic decomposition between 90° and 175°C. In this temperature range, the rate of decomposition follows the simple first-order expression... 

Like nitrocellulose, nitroglycerin also undergoes a slow first-order exothermic decomposition at temperatures below 140°C. As the pressure is increased, this decomposition reaction is followed by a sudden explosive reaction. Evidence suggests that the explosive reaction is autocatalyzed by the accumulation of N02. The combined results of several studies indicate that... 

The calculated thermal effect in this reaction (ca. 1250kcal/kg) would fall between those of the explosive decomposition of nitroglycerine and guncotton, and the calculated temperature would be ca. 2500°C. 

The decomposition of powder at an elevated temperature does not differ greatly from that of the nitric esters themselves, i.e. nitrocellulose and nitroglycerine (the decomposition of nitrocellulose at various temperatures was discussed earlier in Vol. II, p. 310). The higher the temperature, the more actively the decomposition of the powder proceeds, with total loss of nitrogen, as NO and N02, and carbon as CO and C02. Hydrogen is evolved chiefly as water, the amount of water decreasing with increase in the temperature of decomposition of the powder (Sapozhnikov s investigations). 

In some countries, especially during World War I when nitroglycerine was in short supply, it was partly replaced by aromatic nitro compounds, e.g. liquid DNT (a liquid mixture of DNT and TNT isomers). Partial replacement of nitroglycerine by nitro compounds also reduced the erosive effect of the powder by lowering the heat of explosion and the flame temperature during explosive decomposition. 

On suitable initiation of a homogeneous liquid explosive, such as liquid nitroglycerine, the pressure, temperature, and density will all increase to form a detonation wave front. This will take place within a time interval of the order of magnitude of 10 12 s. Exothermic chemical reactions for the decomposition of liquid nitroglycerine will take place in the shockwave front. The shockwave will have an approximate thickness of 0.2 mm. Towards the end of the shockwave front the pressure will be about 220 kbar, the temperature will be above 3000 °C and the density of liquid nitroglycerine will be 30% higher than its original value. 

For every 10 °C increase in temperature, the rate of decomposition is approximately doubled, but may increase as much as 50 times if the explosive is in the molten state. The rates of decomposition depend on the condition of storage and the presence of impurities which may act as catalysts. For example, nitroglycerine and nitrocellulose decompose at an accelerated rate due to autocatalysis, whereas the decomposition rate of TNT, picric acid and tetryl can be reduced by removing the impurities which are usually less stable than the explosive itself. With many of the explosives the presence of moisture increases the rate of decomposition. 

Hydrolytic decomposition has already been discussed. A different type of decomposition of nitric esters occurs at elevated temperatures. More detailed information concerning this type of decomposition will be included in the descriptions of the individual esters properties, in particular those of nitroglycerine and nitrocellulose. 

It is known and has been demonstrated by several authors (by Sapozhnikov et al. [80] for nitrocellulose by Lukin [81] for nitroglycerine) that change of temperature alters the composition of the reaction products. As the result of numerous experiments, particular temperatures were chosen for definite nitric esters. Thus, owing to the greater ease of decomposition of nitroglycerine as compared with nitrocellulose the high temperature heat test for nitroglycerine is carried out at a temperature lower than that for nitrocellulose (120 and 132° C respectively). 

Nitroglycerine begins to boil at a temperature above 180°C. At the same time decomposition takes place accompanied by the evolution of nitric oxides and water vapour. In the distillate, dilute nitric acid and some nitroglycerine is present, probably carried over with the water vapour. The water is formed as a result of the partial decomposition of nitroglycerine which occurs when it is heated to high temperature (see. p. 47). 

Heating nitroglycerine (particularly moist samples) at a temperature of 75°C brings about an apparent decomposition within 3-4 days characterized by the development of acid products. After 6 days the presence of HNO3 is clearly distinguishable. If the volatile products of decomposition are removed, e.g. by blowing with air, as quickly as they are developed, then only very slow decomposition of the nitroglycerine takes place. 

The decomposition of nitroglycerine at higher temperatures was investigated by Snelling and Storm [64] who established that at a temperature of 135°C the decomposition is sharply distinct from the lower temperature decomposition and... 

Temperature of initiation of nitroglycerine is 200-205°C (bath temperature), the rate of the temperature increase being 20° per min. Above 180°C a distinct exothermic decomposition of the substance begins, and hence at the moment of explosion the temperature of the nitroglycerine is higher than that of the bath, i.e. 215-218°C (Snelling and Storm [64]). 

T. Urbanski, Malendowicz and Dybowicz [68] examined the behaviour of nitroglycerine (and of other nitric esters) exposed to ultra-violet rays and established that nitroglycerine irradiated once for a short period with a quartz lamp started to undergo slow decomposition which stopped only after an interval of 2-3 days. A sample of 3 g nitroglycerine was irradiated for 1 hr with rays from quartz lamp passing through a filter permeable to rays of 3200-4100 A whilst maintained at a temperature of 15°C. In order to test the decomposition of the specimen, from time to time 0.25-0.5 g sample of the substance were removed, shaken with water and the pH values determined. The following results have been obtained immediately after irradiation pH = 6.86 after 6, 24, 48 and 72 hr—6.12, 4.66,4.48 and 5.22 respectively. 

The chemical stability of dinitrochlorohydrin is higher than that of nitroglycerine. It withstands the Abel heat test at 72°C for 30 min. On heating at a temperature of 75°C, the first signs of decomposition and the development of acid fumes do not appear before 10-12 days. A small quantity of chlorohydrin dinitrate heated in a test tube undergoes decomposition with the evolution of oxides of nitrogen at temperature above 170°C. Complete decomposition takes place (without explosion at 180°C. Larger quantities of the substance decompose with a weak explosion, if heated rapidly to a temperature of about 190°C. 

The nitration process was performed in the usual equipment, controlling the temperature, which should not exceed 25°C, by cooling with a 35% sodium nitrate solution, the temperature of which was — 15°C. Under these conditions nitration lasted about 25 min. When the nitration was completed, the contents of the nitrator were cooled down to 15°C and transferred to a separator. The separation was accomplished within 7 min and the spent acid was immediately sent to the denitration unit. Special care had to be taken to ensure that no spent add remained in the tank, because decomposition of the residual dinitrodiethylene glycol may start within a few hours. None the less such decomposition is less hazardous than that of nitroglycerine, since dinitrodiethylene glycol produces a spontaneous explosion only in the instance when the tank is confined. 

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