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What happens if Nitric & Sulphuric acids are mixed?


Q. in my youth I worked in a chemical plant as a base mix operator. It consisted of combining oleum and nitric acid in a 140,000 lb. capacity tank. If I brought the two together too quickly the work platform would rumble and the temperature chart would rise sharply. What caused this reaction?

Jonas Moore
- Springdale Maryland
April 29, 2021

A. Hi Jonas. Oleum is strong sulfuric acid. Had it been the case that you mixed quite dilute nitric acid with quite dilute sulphuric acid, perhaps not much would happen ... you'd just get an acid with both NO3 and SO4 anions.

But when mixing very strong acids, additional actions can occur like the nitric acid reacting with excess sulfur in the sulfuric acid, the oleum 'stealing' water from the nitric acid, etc. Exactly what reaction was causing the heating and rumbling (boiling?) I'm not sure -- but I'd suspect that water in the nitric acid was being taken up by the sulfuric acid, diluting it and causing that exothermic reaction.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Q. I'm a freelance chemical engineering Consultant.
I have a mixture of 60% H2SO4,25% HNO3 and balance water. Can we recover HNO3 by vacuum distillation. Please advise... Regards

October 4, 2021 Seshagiri rao V V B

Closely related Q&A's, oldest first:


Q. What is the product of nitric acid and sulphuric acid?

Cat M [last name deleted for privacy by Editor]
student - East Yorkshire, England


A. There is no chemical reaction. H + NO3 and H2 + SO4 will give an equilibrium of the ions and the acid. Now, it is possible that if you add concentrated sulfuric acid to the nitric it can become hot enough to break the HNO3 into water and NO2 (gas). Has to do with heat, not a reaction between the two.

James Watts
- Navarre, Florida


A. Mixing of nitric and sulphuric acid ... fairly boring on its own. Now, if we consider this in the context of organic chemistry we have a nitrating mixture. When heated in the presence of organic materials we form the nitrating radical, used for nitrating a number of organic compounds such as phenol, toluene and benzene.

Brian Terry
Aerospace - Yeovil, Somerset, UK

Nitronium ion

October 16, 2014

Q. I want to about mechanism of formation of nitronium ion by the reaction between sulfuric acid (98%) and nitric acid (98%).

saurabh thanki
- jamnagar,gujarat,india

October 29, 2014

A. Hi Saurabh,

Nitronium ion (NO2+)is formed by below reaction:

2 H2SO4 + HNO3 => 2 HSO4(−) + NO2(+) + H3O(+)


David Shiu
David Shiu
- Singapore

June 18, 2022

Q. Sir please explain how this is occurred.

Archita Banerjee
Student - Tarakeswar, India

June 2022

A. Hi Archita. More words please :-)

Saurabh asked the mechanism for formation of nitronium, and David offered the chemical formula for how it happens. I'm not quite sure what you mean by "this". Thanks!

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey


How to make 2EHN

September 14, 2016

Q. Hi, I want to produce 2EHN. How can I do it?
I have mixed H2SO4 and HNO3(2:1 ratio)...
What should I do next?
Thank you

yashar Oroumieh
- Iran

Ed. note: Readers, here's a bit of info on 2EHN .

September 15, 2016

A. The fact that you have started mixing acids without knowing what to do next tells me that you have no idea what you are doing and how hazardous this process can be.
Nitrating organic materials is a job for a qualified organic chemist with facilities to prevent thermal runaway with possible explosive results.
I suggest that you get qualified and competent expert advice and never start a chemical process without clearly knowing everything about the reaction and adequate means to control it and to safely dispose of the waste products.

geoff smith
Geoff Smith
Hampshire, England

May 10, 2017

A. The mixture of nitric acid and sulphuric acid is known as aqua regia.

luchifer jakson
- new Zealand

May 2017

Hi luchifer. Actually, aqua regia is a mixture of nitric acid and hydrochloric acid, in about a 1:3 ratio.

I've always heard that organic chemistry was where the dreams of medical students die; Geoff reminds us that we should take that quite literally :-)


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

NO2 industrial Production Process

June 14, 2017

Q. Dear Teacher,

I need to produce NO2 for special reaction in industrial scale.
Actually I don't want to produce nitric acid but one of way which I considered can be Ostwald's process but finally I don't need nitric acid and just I need NO2.
Another way, also could be Nitric Acid decomposition on mid temperature, it means I can proceed ammonia decomposition on Pt catalyst to produce NO and then to NO2, if the reaction atmosphere has enough amount of H2O then I will have nitric acid and then by it's decomposition NO2 will be produced.
I would like to have your valuable comment on my uncooked concept to prove it to obtain cooked and feasible solution.
Thanks In advance

Amin Shahbazi
- Science & technology university of Iran- Tehran-Iran

Want 2:1 ratio of acids, but 1 Normality

January 18, 2018

Q. Mixture of H2SO4 and HNO3 (2:1 ratio) ... How is it prepared with 1 Normality?
Please specify.

Harshada Pandilwar
- Nagpur, Maharashtra, India

January 2018

A. Hi, Harshada. Sorry but I don't quite understand the question. If it's 2:1 in Normality, which one is supposed to be 1 Normal? If it's 2:1 by weight, I'm not understanding at all. Please explain your situation. Is this a hypothetical question for student homework, or are you actually trying to prepare a solution for some specific purpose? Thanks!


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

February 5, 2018

A. Hi Harshada,

2:1 ratio in acids is:

1) 2:1 in volume? Which concentration each?
2) 2:1 in weight? Of pure or diluted acids?
3) 2:1 molar?

Then, when you have the solution (Option 1a-b, 2a-b or 3), you count all your available protons (H+) and you must dilute your solution until you have 1 mol protons per liter (or, by definition 1 N Acid).

Your definition is diffuse in the first part, so clarify and then just add some water :)


Daniel Montañés
TEL - N FERRARIS - Cañuelas, Buenos Aires, Argentina

February 18, 2018

Q. Hello everybody
Can I use sulphuric acid instead of nitric acid to form an aqua regia?
I have hydrochloric acid and sulphuric acid only.


meso shamo
- alqaara, aseer, saudi arabia

February 2018

A. Hi Musfer. Warning: although you don't need to understand exactly how a watch works to safely use one, you do need to understand chemistry to safely mix and use acids.

Sulfuric acid cannot be substituted for nitric acid because aqua regia requires a strong oxidant, and sulfuric acid is not one; but sodium nitrate can often be used as a substitute for nitric acid. Good luck.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

February 18, 2018

thumbs up sign I appreciate your great advice.
Thanks a lot sir

meso shamo [returning]
- alqaara, aseer, albashaier

March 15, 2018

Q. How can I separate H2SO4 98% and HNO3 68%? We are using this formulation for fuming nitric acid production. We still can detect both acid in our product and waste.

kaki bangku
- Kulai, johor, malaysia

March 2018

? Hi Kaki. Please provide some details of your situation. Without any idea of the real-world restrictions you are faced with, just a hypothetical, it can be hard to offer practical solutions. Thanks!


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

November 17, 2019

Q. For my design project I'm designing a mixer and reactor for the production of Nitrobenzene, I understand that the mixing nitric acid, sulfuric acid and water is exothermic but I'm struggling to calculate the enthalpy of mixing this nitrating mixture (Currently assuming that there is no heat produced due to mixing). For context the composition of this nitrating mixture will be 65% wt sulfuric acid, 25% wt nitric acid and 15% wt Water.

Cian ODonovan
- United Kingdom

December 12, 2019

Q. Hi! I'm carrying out acid digestion of a mixed mineral - organic sediment sample. The aim is to remove the organic material, to leave me with just the non-organic component.

The process goes: 95% sulphuric acid is added and then heated. Once at simmering/boiling temperature, 65% nitric acid is intermittently added, which results in the release of orange steam, and also speeds up the process at which the organic material is dissolved.

Could anybody explain the chemistry going on here? Its a standard technique in my field, but nobody can actually explain what's going on chemically!


Freya Sykes
- Stockholm, Sweden

March 11, 2020

A. Hello Freya,

Sulfuric acid readily dissolves every inorganic not passive compound. As it is, there are some minerals as TiO2 that resist this acid attack by a passive layer of compact oxides.

As the organic compound, you get carbonization (dehydration) and slight oxidation with this acid. Sulfuric is very hydrophilic and literally burns most of the organic compounds into carbon.

With addition of nitric acid, you oxidize everything. Carbon into carbon dioxide, and minerals into metal ions. Almost no passive layer protects minerals from nitric acid. NO2 and N2O4 are released in this oxidation process, and NO2 is orange. That is the red/orange gas you see in the process.

I think you later measure ions in atomic emission/absorption spectrometer, as no solids survive the digestion process!

Hope it helps you understand what you are doing!

Best of luck :)

Daniel Montañés
N. Ferraris S.A. - Cañuelas, Buenos Aires, Argentina

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