Nitroglycerin - one of the most famous explosives, the basis of the composition of dynamite. It has found wide application in many industries due to its characteristics, but so far one of the main problems associated with it is the issue of safety.
History
The history of nitroglycerin begins with the Italian chemist Ascanio Sobrero. He first synthesized this substance in 1846. It was originally given the name pyroglycerin. Already Sobrero discovered its great instability - nitroglycerin could explode even from weak concussions or blows.
The power of the explosion of nitroglycerin theoretically made it a promising reagent in the mining and construction industries - it was much more effective than the types of explosives that existed at that time. However, said instability posed too great a threat during its storage and transportation - so nitroglycerin was shelved.
Things moved a little with the appearance of Alfred Nobel and his family- father and sons began industrial production of this substance in 1862, despite all the dangers associated with it. However, something happened that should have happened sooner or later - an explosion occurred at the factory, and Nobel's younger brother died. The father, after suffering grief, retired, but Alfred managed to continue production. To improve safety, he mixed nitroglycerin with methanol - the mixture was more stable, but very flammable. It still wasn't final.
They became dynamite - nitroglycerin absorbed by diatomaceous earth (sedimentary rock). The explosiveness of the substance has decreased by several orders of magnitude. Later, the mixture was improved, diatomaceous earth was replaced with more effective stabilizers, but the essence remained the same - the liquid was absorbed and ceased to explode from the slightest shaking.
Physical and chemical properties
Nitroglycerin is a nitroester of nitric acid and glycerol. Under normal conditions, it is a yellowish, viscous oily liquid. Nitroglycerin is insoluble in water. Nobel used this property: in order to prepare nitroglycerin for use after transportation and free it from methanol, he washed the mixture with water - methyl alcohol dissolved in it and left, and nitroglycerin remained. The same property is used in the preparation of nitroglycerin: the synthesis product is washed with water to remove the remnants of the reagents.
Nitroglycerin hydrolyzes (to form glycerol and nitric acid) when heated. Withoutheating goes alkaline hydrolysis.
Explosive properties
As already mentioned, nitroglycerin is extremely unstable. However, here it is worth making an important remark: it is susceptible precisely to mechanical stress - it explodes from a concussion or impact. If you just set it on fire, the liquid will most likely burn quietly without an explosion.
Nitroglycerin stabilization. Dynamite
Nobel's first experience in stabilizing nitroglycerin was dynamite - kieselguhr completely absorbed the liquid, and the mixture was safe (until, of course, it was activated in a demolition bomb). The reason diatomaceous earth is used is because of the capillary effect. The presence of microtubules in this breed causes the effective absorption of liquid (nitroglycerin) and its retention there for a long time.
Laboratory Obtaining
The reaction for obtaining nitroglycerin in the laboratory is now the same as that used by Sobrero - esterification in the presence of sulfuric acid. First, a mixture of nitric and sulfuric acids is taken. Acids are needed concentrated, with a small amount of water. Further, glycerin is gradually added to the mixture in small portions with constant stirring. The temperature must be kept low, because in a hot solution, instead of esterification (ester formation), glycerol will be oxidized with nitric acid.
But since the reaction proceeds with the release of a large amount of heat, the mixture must be constantly cooled (usuallydone with ice). As a rule, it is kept around 0 ° C, exceeding the mark of 25 ° C can threaten with an explosion. The temperature is constantly monitored with a thermometer.
Nitroglycerin is heavier than water, but lighter than mineral (nitric and sulfuric) acids. Therefore, in the reaction mixture, the product will lie in a separate layer on the surface. After the end of the reaction, the vessel must be cooled down, wait until the maximum amount of nitroglycerin accumulates in the upper layer, and then drain it into another container with cold water. Then comes intensive washing in large volumes of water. This is necessary in order to purify nitroglycerin from all impurities as best as possible. This is important because, together with the remains of unreacted acids, the explosiveness of a substance increases several times.
Industrial production
In industry, the process of obtaining nitroglycerin has long been brought to automation. The system that is currently in use, in its main aspects, was invented back in 1935 by Biazzi (and is called the Biazzi installation). The main technical solutions in it are separators. The primary mixture of unwashed nitroglycerin is first separated in the separator under the action of centrifugal forces into two phases - the one with nitroglycerin is taken for further washing, and the acids remain in the separator.
The rest of the production steps are the same as the standard ones. That is, mixing glycerol and nitratingmixtures in the reactor (produced with the help of special pumps, mixed with a turbine agitator, cooling is more powerful - with freon), several washing stages (with water and slightly alkalized water), each of which is preceded by a stage with a separator.
The Biazzi plant is quite safe and has a fairly high performance compared to other technologies (however, usually a large amount of product is lost during washing).
Home conditions
Unfortunately, although rather fortunately, making nitroglycerin at home involves too many difficulties, which are mostly not worth the result.
The only possible way to synthesize at home is to obtain nitroglycerin from glycerol (as in the laboratory method). And here the main problem is sulfuric and nitric acids. The sale of these reagents is restricted to certain legal entities and is strictly controlled by the government.
The obvious solution is to synthesize them yourself. Jules Verne in his novel "The Mysterious Island", talking about the episode of the production of nitroglycerin by the main characters, omitted the final moment of the process, but described in great detail the process of obtaining sulfuric and nitric acids.
etc. Will the average addicted person have it? Unlikely. Therefore, homemade nitroglycerin in the vast majority of cases remains only a dream.
