Nitric acid, nitric acid

Nitric acid, nitric acid

What is nitric acid?
Nitric acid (HNO3) is a very corrosive mineral acid. This pure compound is colorless and turns yellow over time due to decomposition into nitrogen oxides and water. Most of the nitric acid available in the market has a concentration of about 68% by mass. When the concentration of HNO3 solution is more than 86%, it is called sooting nitric acid. Depending on the amount of nitric acid present in the aqueous solution of this substance, in concentrations of about 86% it is red sooting nitric acid and in concentrations above 95% it is white sooting nitric acid.

Nitric acid is an introduction that is usually used for nitration and addition of nitro functional group to organic molecule. Some nitro explosive compounds are sensitive to heat and shock, and these compounds are used in the production of explosives. However, other compounds of stable nitrogen substances are used as pigments in ink and paint. Nitric acid is usually used as a strong oxidizing agent.

Physical and chemical properties of nitric acid
In the market, nitric acid is available as an azeotrope solution of 68% HNO3 with water. This solution has a boiling point of 120.5 degrees Celsius at a pressure of 1 atmosphere. The resulting solution is known as "concentrated nitric acid". Pure concentrated nitric acid is a colorless liquid at room temperature. This substance is found in two aqueous states, monohydrate and trihydrate, which are shown below.

HNO3.H2O and HNO3.3H2O

Contamination of nitric acid with nitrogen dioxide
Nitric acid decomposes when exposed to heat and light and is therefore often stored in brown glass bottles. This substance turns into water, oxygen and nitro as a result of decomposition according to the following reaction.

4HNO3→2H2O 4NO2 O2

This reaction may lead to some non-negligible changes in the upper vapor pressure of the liquid as the nitrogen oxides produced partially or completely dissolve. Nitrogen dioxide (NO2) remains dissolved in nitric acid and turns it yellow or even red at a higher temperature. Pure nitric acid produces white fumes when exposed to air, while this acid produces red or brown fumes when dissolved in nitrogen dioxide. Nitrogen oxides (NOX) are soluble in nitric acid.

Sooting nitric acid
Commercial nitric acid contains about 98% nitric acid and a density of 1.5 grams per cubic centimeter. This solution is usually used in explosives production industries. This acid is volatile and non-corrosive.

Red Sooty Nitric Acid or RFNA
This material contains significant amounts of dissolved nitrogen dioxide (NO2), which is separated from the solution with a reddish brown color. Due to the dissolution of nitrogen dioxide in the nitric acid solution, the density of the sooting nitric acid is low and reaches about 1.490 g/cm3.

Inhibited sooting nitric acid (shown by the symbols IWFNA or IRFNA) can be made by adding 0.6 to 0.7 mass percent hydrogen fluoride (HF). This fluoride is used to resist corrosion