The key difference between fuming nitric acid and concentrated nitric acid is that the fuming nitric acid forms a colorless, yellowish or brownish fume whereas the concentrated nitric acid usually does not form a fume; but a very high concentration of this acid may give off-white colored fumes.
Nitric acid is a very corrosive and dangerous acid that has the chemical formula HNO3. Moreover, it can have either a dilute or concentrated chemical nature. Either way, it has nitric acid molecules dissolved in water. The reaction between nitrogen dioxide and water forms nitric acid. But in the preparation of fuming nitric acid, we can prepare it by adding excess nitrogen dioxide to nitric acid.
CONTENTS
1. Overview and Key Difference
2. What is Fuming Nitric Acid
3. What is Concentrated Nitric Acid
4. Side by Side Comparison – Fuming Nitric Acid vs Concentrated Nitric Acid in Tabular Form
5. Summary
What is Fuming Nitric Acid?
Fuming nitric acid is a commercial grade of nitric acid that has a very high concentration and a high density. It contains 90-99% HNO3. We can prepare this liquid via adding excessive nitrogen dioxide to nitric acid. It forms a colorless, yellowish or brownish fuming liquid that is highly corrosive. Therefore, this acid solution has gaseous molecules in combination with water; there is no water in it. The fume of this acid rises off the surface of the acid; this lead to its name, “fuming”. The chemical formula of this compound is HNO3-xNO2.
Furthermore, there are two major forms of this acid as white and red fuming nitric acid. Therefore, we consider the white fuming acid as the purest form of nitric acid having less than 2%; sometimes, no water at all. Thus, it is very close to anhydrous nitric acid, and it is available as 99% solution. It contains a maximum of 0.5% nitrogen dioxide. It is useful as a storable oxidizer and a rocket propellant.
Figure 01: White Fuming Nitric Acid
Red fuming nitric acid consists of 90% HNO3. It has a high nitrogen dioxide content, which makes the solution appears in reddish-brown. It has a density of less than 1.49 g/cm3. So, it also is useful as a storable oxidizer and a rocket propellant. To prepare this acid, we can use 84% nitric acid and 13% dinitrogen tetroxide with 2% water.
Uses:
- Red fuming nitric acid is a component of a monopropellant.
- Useful as a sole fuel in rockets.
- As storable oxidizers.
- White fuming nitric acid is used in the production of explosives. Ex: nitroglycerine.
What is Concentrated Nitric Acid?
Concentrated nitric acid is simply a solution containing more nitric acid in less water. This means the concentrated form of this acid contains a less amount of water compared to the amount of solutes in it. In commercial scale, 68% or upwards is considered as concentrated nitric acid.
Figure 02: 70% Nitric Acid
Moreover, the density of this solution is 1.35 g/cm3. This much concentration does not produce fumes, but the very high concentration of this acid may give off-white colored fumes. We can produce this liquid via reacting nitrogen dioxide with water.
What is the Difference Between Fuming Nitric Acid and Concentrated Nitric Acid?
Fuming nitric acid is a commercial grade of nitric acid that has a very high concentration and a high density. Moreover, it forms a colorless, yellowish or brownish fume. The lowest concentration of this acid is 90%. Concentrated nitric acid is simply a solution containing more nitric acid in less water. The lowest concentration of this acid is 68%. In addition to that, this acid usually does not form a fume; but the very high concentration of this acid may give off-white colored fumes. The following infographic presents more details on the difference between fuming nitric acid and concentrated nitric acid.
Summary – Fuming Nitric Acid vs Concentrated Nitric Acid
There are two forms of nitric acid with a high concentration of HNO3; they are fuming nitric acid and concentrated nitric acid. The key difference between fuming nitric acid and concentrated nitric acid is that the fuming nitric acid forms a colorless, yellowish or brownish fuming whereas the concentrated nitric acid usually does not form a fume; but a very high concentration of this acid may give off-white colored fumes.
Reference:
1. “Nitric Acid.” Wikipedia, Wikimedia Foundation, 31 July 2018. Available here
2. “Nitric Acid.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine. Available here
Image Courtesy:
1.’Nitric acid fuming’By W. Oelen (CC BY-SA 3.0) via Commons Wikimedia
2.’Nitric acid 70’By Aleksander Sobolewski via Wikimedia Commons, (CC BY-SA 4.0) via Commons Wikimedia