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topic 14035

Neutralizing nitric acid with sodium bicarbonate


 

Q. I want to neutralize 100 gallons of 5% nitric acid and water solution with sodium bicarbonate, how much sodium bicarbonate would I need?

John Keaser
- Englewood, Florida


 

A. Please pull out a chemistry book to check my recollection, but let's see. The reaction is probably:

HNO3 + NaHCO3 => NaNO3 + H2O + CO2

If this is correct then it takes one part of sodium bicarbonate to neutralize one part of nitric acid.

5 percent nitric is probably not a whole lot heavier than water, so 100 gallons equals 834 pounds of solution equals 42 pounds of nitric acid.

So the amount of bicarbonate you need is 42 pounds times the molecular weight of bicarbonate divided by the molecular weight of nitric acid. I figure about 56 pounds.

I assume that this is about double-checking the amount you calculated by scaling up from the beaker sized titration you did under a lab hood before you even began dreaming about working with 100 gallons of the stuff :-)

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


 

A. John,

The easiest way to answer your question would be to do a small scale experiment (1 gal, or so), then do the math.

Just a follow up point. I'm not sure what (if any) experience you've had at neutralizing. And, while 5% isn't extremely strong, be careful...slowly add the Sodium Bicarbonate to your nitric to see what, if any, reaction you are going to get.

Marc Green
Marc Green
anodizer - Boise, Idaho


 

A. Hi Marc,

Your colleague Randal Fowler would have a heart attack (or his dawg would) if he heard YOU saying 'add the bicarb to the acid'. Tut, tut! Mind you ,laws and regs, etc., are made to protect the illiterati ... isn't there a saying LAWS ARE TO BE BLINDLY OBEYED BY FOOLS BUT ACT AS A GUIDE TO WISE MEN?

However, because the nitric was so weak, I, too, would have thought of carefully adding the bicarb to neutralize it.

freeman newton portrait
Freeman Newton
White Rock, British Columbia, Canada

(It is our sad duty to
advise that Freeman passed away
April 21, 2012. R.I.P. old friend).




 

Q. We might be forced to passivate in place 80' of 4" SS tube in a dog food plant, may God forbid. We ain't qualified. But if it comes to pass l will have around 60 gallons of 25% nitric acid, 5% hydrofluoric acid to get rid of. Would the 1:1 sodium bicarbonate neutralization technique apply equally to this higher concentration as to the 5% solution originally queried above? What about the hydrofluoric - does it amount to a wild card?

I really hope we can get out of this..... we're just simple pipe welders, not chemists.

Mike F [last name deleted for privacy by Editor]
- St. Joseph, Missouri, USA



A. If you don't feel qualified don't do it! Nitric-hydrofluoric acid treatments carry risks and demand knowledge, skills, and protective equipment. Specialists can be contacted for on-site projects like this.

Calculations are only a guide to give you a ballpark estimate of how much chemical to buy. As Marc says, titrating a small volume and scaling up is the way to do it. But 25% nitric and 5% HF would mean you will need about six times as much neutralizer as for a 5 percent solution (I didn't do a real calculation, I just multiplied by 6).

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha



Does bicarbonate after nitric passivation do anything other than neutralize?

June 30, 2013

Q. Hi,
I would like to know if sodium bicarbonate has any other function other than neutralisation post Nitric Passivation.

I am wondering if the sodium bicarbonate has any positive effect in producing stain free parts post rinsing.

The process flow in the line is degrease-rinse-rinse-pickle-rinse-nitric-rinse-hot rinse

Alan Tobin
- Ireland


July 4, 2013

A. Hi Alan,

I would have thought that the best controls to prevent staining is the quality of the rinse water, especially the last two rinses. I would personally use distilled or demineralised water in the final rinses, including the hot rinse. I would control the water by conductivity, keeping the water below 150 microsiemens.

To me the bicarbonate is a neutraliser only and will not prevent staining.

Brian Terry
Aerospace - Yeovil, Somerset, UK



July 8, 2019

Q. Hi.
Our guys mixed nitric with HCl! We use nitric for chrome stripping, so we bought a new batch of chemicals and replaced old ones. After adding 30 ltr of nitric to it's bath, we accidentally added HCl into it. It was fuming; now it's stable, though it's very corrosive.
What's the use of this mixture and how can this be neutralised?
Thanks

Gurudip D [last name deleted for privacy by Editor]
Production - Karnataka India


July 2019

A. Hi Gurudip. Mixes that have been made accidentally like this have no use or value. After accidentally making a dangerous chemical, please don't try to now find a use for it. Neutralize it with baking soda under careful supervision -- which clearly means not having the people who created it attempt to neutralize it :-)

The neutralization process will gas and foam enormously, so a lot of time will be required. I hope management is carefully investigating this accident and installing at least two separate levels of checks to prevent it from happening again; it could have been a catastrophe. Good luck!

Regards,

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

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