# Regenerating Nitric



## Anonymous (Aug 6, 2008)

according to this link, if you add hcl to your silver nitrate, you will regenerate your nitric acid, and get silver chloride precip - could it really be this easy?

Jim

Oops, forgot to put the link in, http://www.madsci.org/posts/archives/1999-10/940019801.Ch.r.html


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## goldsilverpro (Aug 6, 2008)

I used to leach silver braze from jet engine parts, in large vats, using 50/50 nitric. When the silver built up to a desirable level, I accurately analyzed the silver content and added only enough HCl to precipitate about 90% of the silver. This process regenerated the nitric but, at the same time, it became more dilute, due to the large amount of water in the HCl. Also, the braze contained copper, which took up a lot of nitric space. Therefore, I could only do this a few times before it got too weak to efficiently dissolve the silver braze.

Had I removed all of the silver each time, instead of only 90%, I surely would have gotten a little chloride ion in the solution. This would cause problems in future dissolving cycles, as it would create AgCl which would coat the undissolved braze and make it more difficult to dissolve.


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## Noxx (Aug 6, 2008)

Bubbling HCl gas into the solution would work I suppose.


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## Anonymous (Aug 6, 2008)

Also, on that page they make phosphoric acid by adding sulfuric to calcium phosphate, why would it not work to make nitric adding sulfuric to calcium nitrate?


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## warrendya (Aug 6, 2008)

goldsilverpro said:


> This process regenerated the nitric but, at the same time, it became more dilute, due to the large amount of water in the HCl..



I suppose at this point you could distill the nitric if you were set up for that (difficult, from what I understand)


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## Anonymous (Aug 6, 2008)

or boil down the mother liquid to concentrate it, then it would dilute back to the concentration you wanted.


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## warrendya (Aug 6, 2008)

The boiling point of nitric acid is 83C, wouldn't the acid just boil off and be lost before enough water evaporated to concentrate the nitric?


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## goldsilverpro (Aug 6, 2008)

I didn't (and still wouldn't) worry myself about nitric. It only costs about $2.50 a gallon in 55 gal. drums. In California, an oil company picked up our acid wastes for free. For some reason, it seems they use acid wastes to flush out oil wells. In Texas, 4 years ago, the waste division of Van waters and Rogers picked up our avid wastes for less than $1/gallon. They picked up our cyanide wastes for $1.25/gallon. Waste of time and money to even think about distilling nitric. If I'm lying, I'm flying.


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## OMG (Aug 6, 2008)

Water and nitric acid make an azeotrope at about 60% concentration which boils enough below 100C (probably that 83C you mentioned) that you can distill it. Check out youtube and sciencemaddness, they have stuff on it.
And they say that using calcium nitrate is about the best nitrate to use to make nitric acid. (by adding sulfuric, and making nitric and calcium sulfate - calcium sulfate is a desiccant, so you can make stronger nitric)


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## Anonymous (Aug 6, 2008)

GSP, no one doubts you. For me however, nitric is a royal pain, and I wish I had enough stuff to use gallons. But, if I got a quart and could strech that out, it may last me for a very long time.

Other side, I live in farm country and calcium nitrate is easy as pie, now if I could mix sulfuric, battery acid with it, that would be great too. I am going to try this this weekend, then I will know for myself.

Jim


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## Noxx (Aug 7, 2008)

OMG said:


> Water and nitric acid make an azeotrope at about 60% concentration which boils enough below 100C (probably that 83C you mentioned) that you can distill it. Check out youtube and sciencemaddness, they have stuff on it.
> And they say that using calcium nitrate is about the best nitrate to use to make nitric acid. (by adding sulfuric, and making nitric and calcium sulfate - calcium sulfate is a desiccant, so you can make stronger nitric)



When I make my own nitric and distill it, it boils at around 120C, not 80C...

And personally, I would say that calcium nitrate is the worst nitrate to use to make nitric acid, even with distillation. You end up with a rock hard salt in your distilling flask that is impossible to break. (I learned it the hard way, my flask broke while I was trying to break the salt.)


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## Lou (Aug 7, 2008)

That's the truth.


Typically it's done with KNO3 or NaNO3. Ammonium nitrate can also be used, but it's probably in your best interests to vacuum distill that (otherwise there will be traces of ammonium nitrate in your acid).


I wonder how many gallons of this stuff I've distilled?


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## goldsilverpro (Aug 7, 2008)

James,

Sorry that I came across as a smarta**. I really didn't mean it. Since day one, I have never been able to mentally adapt to this refining as a hobby thing. I associate refining with earning a living and, when I think of nitric, I think of drum quantities. I'll try to be more considerate in the future.


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## Harold_V (Aug 7, 2008)

goldsilverpro said:


> I have never been to mentally adapt to this refining as a hobby thing. I associate refining with earning a living and, when I think of nitric, I think of drum quantities.



You are not alone. My first month or so on this board I felt I had nothing to offer. Having worked with commercially prepared acids as long as I refined (overall, more than 20 years), I struggled with many of the work-arounds that are promoted. Only when I cleared my mind did it start to make sense. The methods are often slow, but they work----and are a good solution for anyone that doesn't have ready access to commercial acids. My problem now is that I have no experience using them, so I can't advise anyone. We're fortunate to have LaserSteve on the board. 

Harold


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## warrendya (Aug 7, 2008)

Back to the nitric acid...I broke down and bought two gallons from the guy on ebay. Shipping for 2 gallons was only $2 more than for one gallon, so I'm inclined to think he's not using shipping as a profit center (especially after researching what you need to do to legally ship small quantities of nitric). Net cost including shipping was $63.43 per gallon or $15 per liter. I cannot make poor man's nitric any cheaper. I wish I had access to drums of it at $2.50 a gallon, but as GSP points out, that's a pro's price. I spent an afternoon figuring what it would take to buy this acid in a drum and legally ship it out in small quanties. You need documented and ongoing training and certified new packaging. At $15 a liter, the ebay seller is definitely NOT raping customers.

Dan


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## goldsilverpro (Aug 8, 2008)

If you're in So. Ca., try Tri-ess in Burbank. They used to repackage chemicals. I know they made some changes, but they might carry nitric.


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## warrendya (Aug 8, 2008)

GSP, I found the Tri-ess website and I'm sorry to say that the owner has passed away and the business was closed in July of 2005. However, their website was kind enough to post links to suggested suppliers. For chemicals, a company called Del Amo Chemical in Gardena was suggested. Their website doesn't list prices, but they do carry nitric and state no order is too small. I'm flying out of LAX next week and when I return I will stop in and check them out.

Thanks, Dan


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## warrendya (Aug 13, 2008)

Followup - I stopped by Del Amo today and purchased 7 pounds of nitric acid for $37.00. By eyeball this looks to be about 2.5 liters.

Not terribly cheap, but if you figure you get a nice media bottle (~$10) and a 5 gallon plastic bucket (~$5) as part of the deal, it comes pretty close to the $14.95 a quart the ebay guy charges, and I didn't have to pay shipping.


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## goldsilverpro (Aug 13, 2008)

Sounds like reagent grade price. A 2.5 liter - 5 pint - bottle? There has to be someone cheaper.


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## Harold_V (Aug 14, 2008)

goldsilverpro said:


> Sounds like reagent grade price. A 2.5 liter - 5 pint - bottle? There has to be someone cheaper.



The price is staggering! I used to buy a 55 gallon drum of tech grade for $207! 

Harold


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## goldsilverpro (Aug 14, 2008)

I bought a 55 drum about 4 years ago in Houston and it cost about $140 - about $2.50/gallon. I doubt if it's gone up much since then.


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## warrendya (Aug 14, 2008)

goldsilverpro said:


> Sounds like reagent grade price. A 2.5 liter - 5 pint - bottle? There has to be someone cheaper.



It's made by General Chemical, the label says:

Class 10 Certified low particle grade chemical
Meets SEMI Grade specifications
Filtered thruough 0.2 micron filters

and it has an expiration date !


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