Nitroglycerin

History

Nitroglycerin was discovered by Ascanio Sobrero in 1847, when he worked with Theophilus-Jules Pelouze at the university of Turin. The industrial manufacturing process was worked out by Alfred Nobel in the Années 1860. Its company exported a mixture of nitroglycerin and gunpowder called “detonating Swedish oil”, which was quickly interdict following catastrophic accidents. He also discovered in 1866 qu ' one could stabilize nitroglycerin by mixing it with a siliceous sand of natural origin: the Kieselguhr. Thereafter, that led to the development of the Dynamite and the similar mixtures ( dualine and lithofractor ), where one adds to the nitroglycerin of the inert compounds or the fuels absorbents (for example the Nitrocellulose to manufacture a yellow gel of color, the explosive gelatin ).

Manufacture

Nitroglycerin is manufactured in laboratory by the nitration of the glycerin (Glycérol) which is then mixed with the mixtures of sulphuric and nitric acid.

C₃H₅ (OH) ₃ + 3HNO₃ → C₃H₅ (NO₃) ₃ + 3:00 ₂O

The temperature should not exceed the 30°C during the reaction under risk of explosion. Nitroglycerin is stabilized and is washed by water and of the Sodium carbonate until it becomes neutral. This extremely dangerous chemical reaction is carried out by professionals in laboratories especially equipped. The brother of Alfred Nobel died about it tragically.

Properties

It is a matter very sensitive to the friction, the shocks, the rises in temperature and the sparks. Its sensitivity to the shock is however relative - and quite less than than the legend claims (conveyed by the cinema for its spectacular side, in particular in the film Wages of the fear ). Indeed, a nitroglycerin drop, released a height of approximately a meter fifty (i.e. size of the actor in quoted film), or even of several tens of meters (beyond that, its speed does not increase any more because of resistance of the air) is not likely any to explode, the energy of the shock being absorbed by its deformation. Tests showed that a bottle of glass filled with nitroglycerin, but completely free of any trace of product on its external wall, could be precipitated of a cliff and to break on the rocks without exploding. On the other hand, the same bottle, released a height of a few centimetres hardly on a hard ground (metal, stone), undoubtedly exploded if the bottle (or ground) were covered with a fine layer of nitroglycerin (at the time of the contact with the ground, the external nitroglycerin film undergoes a true percussion between two hard matters, which causes its detonation, then, by a phenomenon known as “of sympathy”, the explosion of the nitroglycerin contained in the bottle). Seepages on the walls of the containers used for its transport would be thus at the origin of accidents allotted wrongly to the great sensitivity of nitroglycerin. However, to type above with the hammer remains a very bad idea: subjected to an energetic and concentrated shock, it explodes according to a first mode of detonation, located at the neighborhoods of: 2000 m/s. If one starts it by means of a suitable detonator, its rate detonation exceeds them then: 7000 m/s. Without one being able to still explain the reason of it nor the mechanism, nitroglycerin is thus the only explosive known to have two modes of detonation. Many chemists amateurs died while trying to manufacture some or to store some.

Stability

In its pure form, nitroglycerin is stable and can be preserved unbounded of time (a sample prepared by Sobrero is thus always preserved at Turin, in the darkness). On the other hand, if it preserves traces of acid of its manufacture, it is degraded in a few days while becoming greenish (nitrous gas release) and then becomes extremely dangerous to handle.

One rather quickly realized that it could be “desensitized” by cooling it until the to solidify. Unfortunately, the process of warming necessary to then be able to make use of it was also risky. Another manner of desensitizing it is to dilute it using a Solvant, like the ethanol or the Acétone. Lastly, one can also make it absorb by inert matter (Kieselguhr, sawdust…) or active (alkaline Nitrates, Nitrocellulose, other explosives…): one thus obtains dynamites, respectively known as at inert or active base. Hundreds of formulations exist, which allow the preparation of dynamites with very precise characteristics.

Medical use

In medicine, the nitroglycerin, called in this case trinitrine (as well as other organic nitrates), can be used with small amounts in certain cardiac affections, like the Angina pectoris in the form of tablets, of pulverizations under the language ( sublingual way ), of continuous intravenous perfusion or stamps ( patch ) transdermic.

The principal effect is the vasodilatation, i.e. the widening of the blood-vessels, which makes it possible to decrease the blood Pressure. Nitroglycerin is transformed by the body into nitric Oxyde by the means of an enzyme, the Aldéhyde déshydrogénase mitochondriale (ALDH), which degrades it in the mitochondries. The nitric oxide produces then the effect Vasodilatateur. The effect of the ALDH was recently discovered (2002) by Jonathan Stamler and Zohiqiang Chen, of the Université Duke, with Durham, in North Carolina.

Anecdote: Alfred Nobel suffered from a Cardiopathie which is treated today with the molecule that it formerly used with any other knowledge; the trinitrine or nitroglycerin.

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