Nitroglycerin is one of the most famous explosives, the basis of the composition of dynamite. It has found wide application in many areas of industry due to its characteristics, but so far one of the main problems associated with it is the issue of security.
History
The history of nitroglycerin begins with the Italian chemist Askanio Sobrero. He first synthesized this substance in 1846. Initially, he was given the name pyroglycerin. Already Sobrero discovered its great instability - nitroglycerin could explode even from weak tremors or shock.
The explosion power 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, the mentioned instability created too great a threat during its storage and transportation - therefore, nitroglycerin was put aside in a long box.
The case moved a little when Alfred Nobel and his family appeared - father and sons started the industrial production of this substance in 1862, despite all the dangers associated with it. However, what happened was to happen sooner or later - an explosion occurred at the factory, and Nobel's younger brother died. After suffering grief, his father retired, but Alfred managed to continue production. To increase safety, he mixed nitroglycerin with methanol - the mixture was more stable, but very flammable. This was still not the final decision.
It became dynamite - nitroglycerin absorbed by kieselguhr (sedimentary rock). The explosiveness of the substance decreased by several orders of magnitude. Later the mixture was improved, kieselguhr was replaced with more effective stabilizers, but the essence remained the same - the liquid was absorbed and ceased to explode from the slightest tremors.
Physical and chemical properties
Nitroglycerin is a nitro ester 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 and free it from methanol after transportation, he washed the mixture with water - methyl alcohol was dissolved in it and left, but nitroglycerin remained. The same property is used in the preparation of nitroglycerin: the synthesis product is washed with water from residual reagents.
Nitroglycerin is hydrolyzed (with the formation of glycerol and nitric acid) when heated. Without heating, alkaline hydrolysis occurs.
Explosive properties
As already mentioned, nitroglycerin is extremely unstable. However, an important remark is worth making here: it is susceptible to mechanical stress - it explodes from a concussion or shock. If you just set it on fire, the liquid will most likely burn quietly without an explosion.
Stabilization of nitroglycerin. Dynamite
The first experiment in stabilizing Nobel nitroglycerin was dynamite - kieselguhr completely absorbed the liquid, and the mixture was safe (until, of course, until it is activated in a subversive checker). The reason why kieselguhr is used is the capillary effect. The presence of microtubules in this rock determines the effective absorption of liquid (nitroglycerin) and its retention there for a long time.
Getting in the lab
The reaction of 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. Then glycerin is gradually added to the mixture in small portions with constant stirring. The temperature should be kept low, since in a hot solution, instead of esterification (ether 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 (usually this is done with the help of ice). As a rule, it is kept in the region of 0 ° , exceeding the mark of 25 ° may lead to an explosion. Temperature control is carried out constantly using 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 still be cooled, wait until the maximum amount of nitroglycerin accumulates in the upper layer, and then merge it into another container with cold water. Then there is intensive washing in large volumes of water. This is necessary in order to clean nitroglycerin from all impurities as best as possible. This is important because, together with the residues of unreacted acids, the explosiveness of the substance increases several times.
Industrial receipt
The industry has long brought automation to the process of producing nitroglycerin. The system that is currently used, in its main aspects, was invented in 1935 by Biazzi (and it 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 selected for further washing, and the acids remain in the separator.
The remaining stages of production coincide with the standard. That is, the mixing of glycerol and the nitrating mixture in the reactor (performed using special pumps, mixed with a turbine stirrer, more powerful cooling with freon), several washing stages (with water and slightly alkalized water), before each of which there is a stage with a separator.
The Biazzi installation is quite safe and has a sufficiently high performance compared to other technologies (however, usually a large amount of product is lost during washing).
Home conditions
Unfortunately, although, rather, fortunately, the synthesis of nitroglycerin at home is associated with too many difficulties, overcoming which is generally not worth the result.
The only possible synthesis method 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 permitted only to certain legal entities and is strictly controlled by the state.
There is an obvious solution - 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 detail the process for producing sulfuric and nitric acids.
Those who are really interested can look into the book (the first part, chapter seventeen), but here's the catch - the uninhabited island literally abounded with the necessary reagents, so the heroes had at their disposal sulfur pyrites, algae, a lot of coal (for roasting), potassium nitrate, and so on. Will it be for an average addicted person? Unlikely. Therefore, home nitroglycerin in the vast majority of cases remains only a dream.