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'''Nitroglycerine''' (or nitroglycerin, also called trinitroglycerin) |
'''Nitroglycerine''' (or nitroglycerin, also called trinitroglycerin) is a [[chemical compound]] that is |
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used in making [[explosive]]s and medically as a [[vasodilator]] (under the trade names of [[Nitrospan]] and [[Nitrostat]]). It is a heavy yellow poisonous oily explosive liquid obtained by [[nitrogen|nitrating]] [[glycerol]]. |
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[[Liquid]] at normal temperature and pressures, it is used in [[construction]] and [[demolition]] and is a component of [[dynamite]]. |
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In its pure form, it is shock sensitive (i.e., physical shock can cause it to explode) and degrades over time to even more unstable forms. This makes it highly dangerous to transport or use in its pure form. |
In its pure form, it is shock sensitive (i.e., physical shock can cause it to explode) and degrades over time to even more unstable forms. This makes it highly dangerous to transport or use in its pure form. |
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An explosion is essentially very fast combustion, and combustion requires fuel and oxidant. Nitroglycerin, as can be seen from its composition and structure (below), essentially contains both these components. If it is detonated under pressure, it explodes to form thousands of times its original volume in hot gas. |
An explosion is essentially very fast combustion, and combustion requires fuel and oxidant. Nitroglycerin, as can be seen from its composition and structure (below), essentially contains both these components. If it is detonated under pressure, it explodes to form thousands of times its original volume in hot gas. |
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== Properties == |
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formula: CH<sub>2</sub>(ONO<sub>2</sub>)-CH(ONO<sub>2</sub>)-CH<sub>2</sub>(ONO<sub>2</sub>) <br> |
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colour: yellow but coulourless when pure<br> |
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aspect: slightly oily liquid<br> |
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density: 1.13 at 15°C<br> |
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melting point: 13.2°C<br> |
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very sensitive to friction, shock, elevation of temperature, and sparks. |
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It is used as an explosive in compositions called dynamite. Nitroglycerin is too sensitive to be used pure and needs other products to be stabilized. It is also used as a medicine for [[angina]] ([[ischaemic heart disease]]) in tablets, |
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ointment or solution for intravenous use. |
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== Preparation == |
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Nitroglycerin is prepared by nitration of glycerin. In the process, glycerin is slowly tipped into a mix of concentrated nitric and sulfuric acid. The solution is slowly mixed. The temperature should never exceed 30°C, otherwise there is a risk of explosion. |
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When the reaction is over, the mix is poured into a large amount of water. The nitroglycerin settles and is washed with water and sodium carbonate until it becomes neutral. |
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=== Manufacture === |
=== Manufacture === |
Revision as of 17:22, 22 January 2003
Nitroglycerine (or nitroglycerin, also called trinitroglycerin) is a chemical compound that is used in making explosives and medically as a vasodilator (under the trade names of Nitrospan and Nitrostat). It is a heavy yellow poisonous oily explosive liquid obtained by nitrating glycerol.
Liquid at normal temperature and pressures, it is used in construction and demolition and is a component of dynamite.
In its pure form, it is shock sensitive (i.e., physical shock can cause it to explode) and degrades over time to even more unstable forms. This makes it highly dangerous to transport or use in its pure form.
An explosion is essentially very fast combustion, and combustion requires fuel and oxidant. Nitroglycerin, as can be seen from its composition and structure (below), essentially contains both these components. If it is detonated under pressure, it explodes to form thousands of times its original volume in hot gas.
Properties
formula: CH2(ONO2)-CH(ONO2)-CH2(ONO2)
colour: yellow but coulourless when pure
aspect: slightly oily liquid
density: 1.13 at 15°C
melting point: 13.2°C
very sensitive to friction, shock, elevation of temperature, and sparks.
It is used as an explosive in compositions called dynamite. Nitroglycerin is too sensitive to be used pure and needs other products to be stabilized. It is also used as a medicine for angina (ischaemic heart disease) in tablets, ointment or solution for intravenous use.
Preparation
Nitroglycerin is prepared by nitration of glycerin. In the process, glycerin is slowly tipped into a mix of concentrated nitric and sulfuric acid. The solution is slowly mixed. The temperature should never exceed 30°C, otherwise there is a risk of explosion.
When the reaction is over, the mix is poured into a large amount of water. The nitroglycerin settles and is washed with water and sodium carbonate until it becomes neutral.
Manufacture
The making of nitroglycerin is obviously potentially very dangerous, because of the product's explosive nature. Do not attempt to make it yourself!
The industrial manufacturing process uses a 50:50 mixture of fuming sulphuric acid (fuming means it is very concentrated) and red fuming nitric acid. This produces nitronium ions in situ, which attack glycerin (also called glycerol) at its negatively charged oxygen atoms. The functional group NO2 is thus added, adding extra oxygen atoms to the flammable substance glycerin.
The use of strong acids almost always results in an exothermic reaction (i.e., heat is produced), and this case is no exception. However, if the mixture becomes too hot, it will explode. Thus, the acid mixture is added slowly to the reaction vessel containing the glycerin. The reaction vessel itself is cooled with ice-cold water or some other coolant mixture at about 0 °C. The vessel itself has an emergency trap door at its bottom, which hangs over a large pool of very cold water. If sensors in the mixture detect the temperature rising too rapidly, then the whole mixture can be dumped into the ice-cold water, which prevents an explosion if done in time.
In medicine, nitroglycerin is used as a heart medication. Another name for nitroglycerin, commonly used in a medical context is glyceryl trinitrate, which more accurately reflects the chemical structure of nitroglycerin:
CH2-NO2 | CH-NO2 | CH2NO2
The principal action of nitroglycerin is vasodilatation, that is,
widening of blood vessels. The main effects of nitroglycerin in episodes of angina pectoris are
- chest pain subsides
- blood pressure decreases
- heart rate increases
See also: nitric acid; physiology