Acid nitric

The nitric acid or sometimes called nitric acid (not to be confused with the chemical usual name of the Nitric acid correspondent with $\ displaystyle {HN_3}$ ) is a chemical Composé very corrosive liquid. It is a Strong acid , generally used in aqueous solution, commonly called Eau-forte by the alchemists then the engravers on copper. If the concentration is higher than 86%, he is baptized acid nitric smoking . The nitric acid is also component acid rains. Its formula is $\ displaystyle {HNO_3}$ .

History

The nitric acid was synthesized for the first time at the end of the 8th century by the alchemist Jabir Ibn Hayyan which obtained it heating Salpêtre KNO₃ and presence of Copper sulfate (CuSO₄.5H₂O) and Alun (KAl (SO₄) ₂.12H₂O). At the 13th century, Albert Large the uses it to separate the Or and the money.

In the middle of the 17th century, Johann Rudolf Glauber obtains the nitric acid by Distillation of the sulphuric Salpêtre in the presence of Acid, proceeded used in laboratory until our time. During the 18th century, Antoine Lavoisier watch that the nitric acid contains at the same time Oxygène and Azote, the precise composition being later given by Henry Cavendish.

The industrial production of nitric acid takes its rise only during the 19th century, the Salpêtre and the sulphuric Acid being then good markets and available in great quantities. In 1838, Kuhlman discovers that it is possible to obtain it by Oxydation Ammoniac in the presence of Platine. However, the ammonia necessary remains of a cost too much high until the invention of the synthesis ammonia and of the Procédé of Haber by Fritz Haber and Carl Bosch in 1909. Wilhelm Ostwald then develops of “Ostwald process” of manufacture of the nitric acid by oxidation of the ammonia, which remains more nowadays used.

Physicochemical properties

The pure nitric acid is a colorless and odorless liquid; various impurities often color it in brown yellow. With room temperature, it releases from red or yellow smoke, because of its decomposition partial in nitrogen Dioxide under the effect of the light.

The nitric acid is a powerful oxidising agent; its reactions with compounds like the Cyanide S, Carbide S, and metal powders can be explosive.
The reactions of the nitric acid with much of organic compounds, like the Terpentine, are violent, the mixture being Hypergolique (i.e. car-flammable).

It is a strong acid of pKa = -2: in aqueous solution it dissociates completely in a Ion Nitrate NO - and a Proton hydrated. The salt S of the nitric acid (which contain the ion nitrates) are called nitrates. Almost the whole of them are very water soluble.
The nitric acid and its salts, the Nitrate S, should not be confused with the Nitrous acid and its salts, the Nitrite S.

physicochemical Properties of HNO₃ - H₂O
with 20 °C and 1,013 bar

Chemical reactions comprising the nitric acid

Action on metals

The nitric acid reacts differently of the other strong acids (

\ displaystyle {HCl, H_2SO_4}

) on metals, because of the oxidizing properties of the radical

\ displaystyle {NH_3}

.Ainsi,

\ displaystyle {HNO_3}

reacting on a metal never gives release of dihydrogene, which is the case for the majority of the other acids reacting on a metal. The following formula gives the equation of the total reaction for any chemical reaction between the nitric acid (

\ displaystyle {HNO_3}

) and a metal

\ displaystyle {M}

of valence

\ displaystyle {N \ not=4}

\ begin {matrix} & \ \ 8HNO_3 + \ frac {6} {N} M & \ overrightarrow {\ qquad} & \ frac {6} {N} M (NO_3) _n + 2NO^ \ nearrow + 4:00 _2O \ \ \ \ end {matrix}

\ forall N \ in \ {1,2,3 \}

Manufacture

The diluted nitric acid is obtained by mixing Dioxide nitrogen (NO) with water; the commercial solutions generally include/understand between 52% and 68% of nitric acid. More concentrated solutions are obtained by Distillation. The nitric acid forming an Azeotropic with water in a proportion of 68% from acid nitric and water 32%, obtaining very pure nitric acid forces to it to distill in the presence of Acid sulphuric. When the solution includes/understands more than 86% of nitric acid it is named smoking and exists in two varieties: white and red. The nitric acid smoking white, is also called 100% because almost (less than 2%) without water.

The commercial production of the nitric acid is made by the Procédé Ostwald according to Wilhelm Ostwald and is carried out in 3 stages starting from Ammoniac:

First stage: the Ammoniac is oxidized in the presence of a catalyst like the rhodium Platine , to form Oxyde nitric (NO) (stage strongly Exothermique):

$\ begin {matrix} & \ \ 4NH_3 + 5O_2 & \ overrightarrow {\ qquad} & 6:00 _2O + 4NO & {\ rm \ Delta \ H^0_ {298}} = - 905,5 {\ rm KJ/mole} \ \ \ end {matrix}$

Then the nitric oxyde is oxidized by the Oxygène (O₂) and is produced Dioxide nitrogen (NO₂):

$\ begin {matrix} & \ \ 2NO + O_2 & \ overrightarrow {\ qquad} & 2NO_2 & {\ rm \ Delta \ H^0_ {298}} = - 56,5 {\ rm KJ/mole} \ \ \ end {matrix}$

Finally the nitrogen dioxide east dissolves in water according to the reaction:

$\ begin {matrix} & \ \ 3NO_2 + H_2O & \ overrightarrow {\ qquad} & 2HNO_3 + NO \ \ \ end {matrix}$

to produce the diluted nitric acid. The produced nitric oxyde is recycled, and the nitric acid concentrated by Distillation until a maximum of 68% (Azéotrope of the nitric acid mixture - water). The higher concentrations are reached by treatment the Nitrate of magnesium Mg (NO₃) ₂. All in all, this process makes it possible to reach an output of 96%.

The nitric acid can also be obtained while making react Nitrate of potassium (KNO₃) and sulphuric Acid concentrated (H₂SO₄), then in distilling the mixture with 83°C until it does not remain any more in the medium but one crystallized white solid composed of KHSO₄). The nitric acid obtained is of Acid nitric smoking red. The nitric Acid smoking white can be obtained by eliminating the oxides from nitrogen dissolved by reducing the Pression to 1/3d' atmosphere approximately during 10-30 minutes. (The nitric Acid smoking red contains a considerable quantity of nitrogen oxides, from where its red color, while Acid nitric smoking white can contain only one maximum of 0,5% of NO₂).

The annual worldwide production of nitric acid is about 60 million tons.

Nomenclature

number CASE: 7697-37-2
number EINECS: 231-714-2

Uses

Commonly used like a Reactive of laboratory, in particular for made up reactions of Nitration of organics, it is used to manufacture by chemical synthesis of the Engrais like the Nitrate of ammonium and of the Explosif S like the Nitroglycérine and Trinitrotoluène. 75% of the nitric production of acid are used in the manufacture of nitrate fertilizers.

As it reacts with the majority of the metals (except the Or, the Iridium and the Platine), it is very much used in Métallurgie and Microélectronique. Mixed with the Hydrochloric acid it forms the Eau levels, one of the rare reagents able to dissolve the Or and the Platine.

It was one of the first Comburant S of the mixtures of Propergol S for the rocket engines, associated with the Kérosène, UDMH - Dimethylhydrazine asymmetrical ((CH₃) ₂NH-NH₂) - and with MMH - monométhylhydrazine (CH₃-NH-NH₂) - as Carburant. In this use, the very corrosive character of the nitric acid was a long time a problem, solved by the addition of 0,6% of Acid hydrofluoric which ensures a Passivation metal. It is replaced since the beginning of the years 1990 by nitrogen tétraoxyde (N₂O₄).

Safety

The nitric acid is a Strong acid , which can cause serious burns. The inhalation of the vapors can involve a pulmonary edema. In contact with concentrated acid nitric, the human Peau is tinted in yellow because of reactions with the Kératine. It is a moderately toxic compound with a lethal amount of 430 mg/kg. It is also a powerful Oxydant which reacts highly with the reducers and the combustible materials being able to cause explosions.

Sentences of risk and councils of prudence

R: 8 (Supports the ignition of the combustible materials)
R: 35 (Causes serious burns)
S: 1/2 (To preserve under key and out of reach children)
S: 23 (not to breathe smoke)
S: 26 (In the event of contact with the eyes, to immediately wash to consult an ophthalmologist)
S: 36 (To wear suitable protective clothing)
S: 45 (In the event of accident or Malayan to consult a doctor immediately and to show him packing or the label)

Reference UNO for the transport of the dangerous matters

Class: 8
number: 2031 (acid nitric other than the nitric acid smoking red)
number: 2032 (acid nitric smoking red)

See too

Ion Strong acid nitronium
Nitrate

External bonds

Certaines information of this article results from and of
international Fiche of safety
FT9 card-indexes toxicological [[INRS]: ]

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