Muriatic acid vs Nitric acid

Martian

Member
May 17, 2020
15
Ecuador
Hi there,
I have Pentair EasyTouch, IntelliChem and IC20 chlorine generator.
The problem is IntelliChem is designed to work with muriatic acid but here in South America sales of this acid are controlled (looks like everyone use it to make drugs) so I cannot just go and get it.
People here using nitric acid to lower pH.

Is it safe to use nitric acid instead of muriatic one?

P.S. Right now my system is recently installed and my acid tank is still never used.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
18,094
Northern NJ
Welcome to TFP.

Handling muriatic acid is a lot safer.

From a @JoyfulNoise post in Handling of Muriatic Acid ...

Nitric acid (HNO3) is a powerful oxidizer and an acid. It causes skin burns because of the -OH group that the acid's structure has. The -OH group deprotonates (takes hydrogen atom away from) most organic compounds and leaves behind the NO2- group in it's place, that is called nitration (nitroglycerin is formed that way). So being a strong acid and a strong oxidizer makes nitric acid dangerous.
 

JamesW

TFP Expert
Mar 2, 2011
19,397
HNO3 + H2O --> H+ + NO3-

Nitric acid + water --> hydrogen ion + nitrate.

So, the nitric acid just completely dissociates into hydrogen ions (acid) and nitrates.

The problem is that you get a lot of nitrates in the water, which is not good.


In addition to the nitrate problem, the acid is dangerous and is not suitable for pools in my opinion.

 
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JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,959
Tucson, AZ
HNO3 + H2O --> H+ + NO3-

Nitric acid + water --> hydrogen ion + nitrate.

So, the nitric acid just completely dissociates into hydrogen ions (acid) and nitrates.

The problem is that you get a lot of nitrates in the water, which is not good.

Agreed on the acidity in aqueous solutions and the introduction of nitrates into the water (fertilizer for algae) but thats only half the story and it’s about as acidic (pKa) as muriatic acid.

Nitric acid is also a powerful oxidizer because of the structure, in simplest terms -

O
\\
N - O- H (hard to draw)
/
O

The hydrogen on the hydroxyl group will dissociated to create the acidity but, in contact with organics and some metals and non-metals, the entire OH group will strip hydrogen from substances or oxidize them to higher oxidation states. The prototypical reaction is with carbon -

Cs+ 4 HNO3 → CO2 + 4 NO2 + 2 H2O

The carbon goes from an oxidation state of zero to +4. This is what makes nitric acid so dangerous to skin and other organic tissues. The burns caused can be very serious and painful.

To the OP - please do not use nitric acid, it is too dangerous outside of a fume hood.
 
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Martian

Member
May 17, 2020
15
Ecuador
Thanks guys. Sounds really horrible.
Will continue trying to bypass that stupid restriction and get muriatic acid from some tuna plant.
And yes 30% nitric acid they sell here for the pools burns skin rapidly.
 

JamesW

TFP Expert
Mar 2, 2011
19,397
If you absolutely can't get muriatic acid, I would try to get sulfuric acid as a substitute instead of nitric acid.

Carbon dioxide might be an option as long as the TA (Total Alkalinity) is not too high.

Using an acidic source of chlorine, such as chlorine gas or trichlor, periodically can help manage pH rise.

What is the TA?

What is your source of chlorine?

In most pools, lowering the TA can significantly reduce pH rise.

However, be sure to maintain the CSI if the pool is plaster.
 
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