Nitrate
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In inorganic chemistry, a nitrate is a salt of nitric acid.
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Chemical properties
The nitrate ion is a polyatomic anion with the empirical formula NO3− and a molecular mass of 62.01 daltons; it consists of one central nitrogen atom surrounded by three identical oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a negative one formal charge and can be represented as a hybrid of the following resonance structures:
Image:Nitrate ion resonance structures.png
The nitrate ion is the conjugate base of nitric acid. A nitrate salt forms when a positively charged ion attaches to the negatively charged oxygen atoms of the ion, forming an ionic compound. Almost all nitrates are soluble in water at standard temperature and pressure.
Uses
Agriculture
Nitrates such as potassium nitrate (saltpeter) and ammonium nitrate are an important source of nitrogen in fertilizers. These nitrates must be used quickly by plants because they are easily lost through leaching or denitrification by bacteria. Nitrate pollution has become an environmental issue in rivers and oceans. According to the Black Hawk County Green Party, the Cedar River (Iowa) has the highest nitrate levels of any river in the world.
Explosives
Nitrates are also oxidizing agents. When mixed with hydrocarbons or carbohydrates, nitrates can form a flammable or even explosive mixture. For example, potassium nitrate is the oxidizing ingredient in black gunpowder.
Food
Nitrates are also used in curing meats.
Medicine
History
The first nitrate was discovered by Italian chemist Ascanio Sobrero in 1847. He was a chemistry professor at the University of Torino and worked under Théophile-Jules Pelouze who himself had worked on discovery of explosives.
Sobrero called the discovered compound pyroglycerin and surprisingly in private correspondence as well scientific papers advocated against its use considering it to dangerous to handle and use.
He described strong headache after putting nitroglycerin on the tongue.
In 1849 German Constantin Hering, tested nitroglycerin in healthy volunteers and he also observed headaches with its use. As a homeopath he thought a good remedy for headaches ('like cures like).
Later, in 1859 Frederick Guthrie worked with amyl nitrate and noticed that accidentary inhalation of it lead to face and neck flushing and heart palpitations. It was lined with vasodilatation. This inspired Lauder Brunton to used amyl nitrate in coronary heart disease. In 1867 he published in the Lancet a scientific paper On the Use of Nitrite of Amyl in Angina Pectoris. Another therapeutic observation was tolerance with repeated use.
Use
In medicine, organic nitrates such as glyceryl trinitrate, isosorbide mononitrate (ISMN) and isosorbide dinitrate (ISDN) are particularly useful for prevention and treatment of angina pectoris. However they can cause a dangerous reaction if taken within 24 hours of taking sildenafil citrate (Viagra) or similar drugs. A list is available at ATC_code_C01#C01DA_Organic_nitrates.
Nitrate poisoning (acquired methemoglobinemia) can be treated with Methylene blue.
Importance in World History
In the late decades of the nineteenth century and into the years of the First World War in the twentieth century, there was no means of chemical synthesis of nitrates. Chile was a major exporter, and European countries with burgeoning populations due to the industrial revolution were dependent on its nitrates for use as fertilizer to feed their people. They were needed for modern military explosives as well. These two critical uses proved to be crucial in world history -- almost. Had the Germans not devised the Haber process for producing nitrate, they would not have been able to feed their civilian population and armies, nor continued to make explosives. The First World War might have ended as a direct result of embargo of essential raw materials. With the aid of inorganic chemistry, however, the war continued.
Related materials
Nitrates should not be confused with nitrites, the salts of nitrous acid. Organic compounds containing the nitro functional group (which has the same formula and structure as the nitrate ion save that one of the O− atoms is replaced by the R group) are known as nitro compounds.
Effects on aquatic life
High levels of nitrate in water can potentially cause the death of fish. Over 30PPM of nitrate can inhibit growth, impair the immune system, cause stress, and reduce energy levels. The principal pathway of entering aquatic systems is through surface runoff from agriculatural or landscaped areas which have received excess nitrate fertilizer. After entering the receiving waters nitrates also can induce algal blooms and eutrophication, causing other ecosystem modification in addition to the mortality effects stated above.
Nitrate is often labelled as NO3 by Aquarists.
See also
External links
- Case Studies in Environmental Medicine - Nitrate/Nitrite Toxicity
- Computational Chemistry Wikics:Dusičnan
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