The key difference between aqua regia and aqua fortis is that aqua regia contains both nitric acid and hydrochloric acid, whereas aqua fortis is another name for nitric acid.
Aqua regia is an acidic and corrosive mixture of three parts of concentrated HCl and one part of concentrated HNO3. Aqua fortis, on the other hand, is an archaic term for nitric acid. It has the chemical formula HNO3, and it is a very corrosive and dangerous acid.
CONTENTS
1. Overview and Key Difference
2. What is Aqua Regia
3. What is Aqua Fortis
4. Aqua Regia vs Aqua Fortis in Tabular Form
5. Summary – Aqua Regia vs Aqua Fortis
What is Aqua Regia?
Aqua regia is an acidic and corrosive mixture of three parts of concentrated HCl and one part of concentrated HNO3. Therefore, the molar ratio of hydrochloric acid and nitric acid is 1:3. This mixture is highly oxidative. This acidic liquid is a fuming liquid, and when freshly prepared, it appears colorless. But it turns yellow, orange, or red within seconds. It can dissolve the noble metals gold and platinum. However, it cannot dissolve all metals.
Figure 01: Freshly Prepared Aqua Regia
Aqua regia is miscible with water. The density is around 1.10 g/cm3. Its melting point is very low, which is around -42 degrees Celsius, and the boiling point is somewhat high and lies around 108 degrees Celsius.
When considering the preparation of this acidic mixture, the mixing of concentrated HCl and HNO3 causes chemical reactions to occur and form nitrosyl chloride and chlorine gas. This is the cause of the yellow color and fuming nature of the mixture. These volatile products escape from the acid, so it loses its potential with time. Moreover, nitrosyl chloride further decomposes into nitric oxide and elemental chlorine.
What is Aqua Fortis?
Aqua fortis is an archaic name for nitric acid. It has the chemical formula HNO3, and it is a very corrosive and dangerous acid. Aqua fortis 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. There are two types of nitric acid: fuming nitric acid and concentrated nitric acid.
Figure 02: 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 by adding excessive nitrogen dioxide to nitric acid. It forms a colourless, 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 leads to its name, “fuming.” The chemical formula of this compound is HNO3-xNO2.
What is the Difference Between Aqua Regia and Aqua Fortis?
Aqua regia can be described as an acidic and corrosive mixture of three parts of concentrated HCl and one part of concentrated HNO3. Aqua fortis is an archaic term for nitric acid and is a very corrosive and dangerous acid. Therefore, the key difference between aqua regia and aqua fortis is that aqua regia contains both nitric acid and hydrochloric acid, whereas aqua fortis is nitric acid.
The following table summarizes the difference between aqua regia and aqua fortis in tabular form for side-by-side comparison.
Summary – Aqua Regia vs Aqua Fortis
The terms aqua regia and aqua fortis are specific terms for acidic liquids. The key difference between aqua regia and aqua fortis is that aqua regia contains both nitric acid and hydrochloric acid, whereas aqua fortis is nitric acid.
Reference:
1. “Nitric Acid.” Wikipedia, Wikimedia Foundation.
2. “Aqua regia.” Wikipedia, Wikimedia Foundation.
Image Courtesy:
1. “Aqua regia in Davenport Laboratories” By Thejohnnler (talk) – Own work (Original text: self-made) (Public Domain) via Commons Wikimedia
2. “Fuming nitric acid 40ml” By W. Oelen – (CC BY-SA 3.0) via Commons Wikimedia