# 61% nitric acid



## Rogerwirecable (Feb 10, 2012)

I've found a supplier in my local area (upstate Ny) for Nitric, the best he can sell me is 61%. This should be acceptable for working.925 silver? I'm just confused concerning the amount of M/l per Gram it will take to desolve. If it takes 1.51m/l of 70% nitric per gram to desolve, would I increase the amount of the 61% solution by 9%, 151+9% to equal 1.64m/l per gram?


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## lazersteve (Feb 10, 2012)

Use the math you presented as a guide to determine the correct amount to use. When performing the reaction add the nitric in small increments allowing it time to react. Use only the amount required to dissolve the metal and nothing more. I do the math and add the calculated volume into a beaker. I make my small additions from this beaker.


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## Rogerwirecable (Feb 10, 2012)

Thank you


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## AztekShine (Feb 11, 2012)

Correct me but I think you can simmer any acid and raise the percent of acid .


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## niteliteone (Feb 11, 2012)

AztekShine said:


> Correct me but I think you can simmer any acid and raise the percent of acid .



Generally this is a true statement. With some exceptions. Others will need to elaborate on this.

But usually we work with diluted acid concentrations. Like for nitric acid we usually use a 50/50 mix of concentrated nitric plus water. We rarely use full strength 70% nitric (except for AR) so their is no need to concentrate the acid before we dilute it. Just add a little less water for the 61% concentration stuff.

Hope this helps
Tom C.


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## nickvc (Feb 11, 2012)

AztekShine said:


> Correct me but I think you can simmer any acid and raise the percent of acid .




It all depends on the concentration you start with, some will only reach a certain percentage as the solution is then saturated. With most of the processes we use acids for here on the forum so long as they are clean most percentages will work, just calculate the amount needed,and as nitric is expensive and in many cases hard to obtain I'd advise adding the necessary water or HCl and then add the nitric in increments until all reaction ceases.


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## AztekShine (Feb 11, 2012)

I see


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## nickvc (Feb 11, 2012)

Aztec this is a huge subject I doubt anyone on the forum doesn't learn something new nearly every week or in my case visit  
I'm always open to criticism as I'm quite accepting of the fact I'm still a novice compared to many of the members but reading the posts here gives me insights into areas that you would never find anywhere else and in a language that even I can usually understand...usually.


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## goldsilverpro (Feb 14, 2012)

Rogerwirecable said:


> I've found a supplier in my local area (upstate Ny) for Nitric, the best he can sell me is 61%. This should be acceptable for working.925 silver? I'm just confused concerning the amount of M/l per Gram it will take to desolve. If it takes 1.51m/l of 70% nitric per gram to desolve, would I increase the amount of the 61% solution by 9%, 151+9% to equal 1.64m/l per gram?



It's not quite that straightforward. A closer approximation would be (70/61)(1.51) = 1.73 ml. However, since this calculation assumes that the specific gravity (SG) of 61% and 70% are the same, which is untrue, it is still slightly in error.

By obtaining the SGs of both strengths from a chart and then using them in the calculations, greater accuracy can be obtained. I've shown how to do this several times, so I won't do it now. I will give the answer, though. It's 1.77 ml.
http://www.handymath.com/cgi-bin/nitrictble2.cgi?submit=Entry

You should also adjust the water. For a solution the same as that made 50/50 from 70% nitric and distilled water, you would use a ratio of 60/40 when using 61%.


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## Rogerwirecable (Feb 14, 2012)

Thank you, I should have paid better attention in High School 40 years ago rather than trying to pick up on my Lab Partner & going to see "Saturday Night Fever"


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## wywiwyg2000 (Feb 29, 2012)

Does your upstate supplier deliver out of state?


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## Rogerwirecable (Feb 29, 2012)

No sorry to say, this was a one time deal. I've been reading for days, On posts of making your own Nitric. Everything points at using LazerSteve's cold method of producing your own at 50%. At this point in time I would really have no need for anything stronger, If I do I should be able to evaporate the water and obtain a 68% or close to it. I've yet to do anything at this point just collecting material & scrap silver, currently at 4800 grams. I've still got 3 months yet of strict researching yet before I try anything. I'm not going to stay over here (AFG) for another year unless I get the 50% base pay raise I asked for.


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## Lobby (Mar 31, 2012)

AztekShine said:


> Correct me but I think you can simmer any acid and raise the percent of acid .



Nope. 

Off memory, HCl (muriatic acid) forms an azeotrope at about 21% wt, if I recall correctly. That means that if you start with 31% HCl and boil it, you'll actually boil off the HCl and decrease its concentration in the solution. 

(Man, I used to do this off the top of my head. Old age, I suppose)

I don't recall the nitric vapor liquid equilibria, but I think it too will boil off.


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## butcher (Mar 31, 2012)

Nitric Azeotropes at approximately 68%,

Heating a dilute nitric acid will rise it's concentration to 68% maximum. (Heating the acid not boiling it, you just want to heat it until the acid vapors off fumes, below a boil, it will vapor off mostly water at first.

Also different concentrations of nitric acid has different boiling points, (so as you concentrate a dilute acid its boiling point changes.

If you heated 80% nitric acid it would fume off 68% nitric acid in fumes, eventually doing this you would lower your acid in the vessel to 68%, and if you kept heating it, you would keep vaporizing off 68% nitric until your vessel was empty (or you were just left with a drop of 68% nitric acid).


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## Lobby (Apr 1, 2012)

butcher said:


> Nitric Azeotropes at approximately 68%,
> 
> Heating a dilute nitric acid will rise it's concentration to 68% maximum. (Heating the acid not boiling it, you just want to heat it until the acid vapors off fumes, below a boil, it will vapor off mostly water at first.
> 
> ...




Thanks, Butcher. It's been since the early 1980's since I worked on HNO3 vapor liquid equilibrium, and I just couldn't remember. After I typed it, I remembered, but then I got busy and didn't have time to edit my post.


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## rickbb (Sep 19, 2014)

Sorry to bring back such an old post, but...

I'm in the process of reducing a volume of Nitric acid at an approximate strength of 10%. I used this to dissolve some silver from glass, (plasma TV). I have it on a low heat, just enough to see vapors, no bubbles.

My question is, will I be losing some of the silver with the water vapor and will I be better off trying to get the silver out from the diluted strength without trying to reduce the volume. 

I want to reduce the volume because I'd rather deal with a smaller amount than 5 gallon buckets full. I'm not really interested in increasing the acid strength, but in just reducing the volume I have to work with.

(There may also be some magnesium in there as well as everything I've read on plasma glass has it as a top layer over the silver electrodes. What I understand is that the magnesium oxide coating is very soluble and should stay in solution. But wanted to mention that in case it may complicate things.)

I want to reduce the volume because I'd rather work with a smaller amount than 5 gallon buckets full. I'm not really interested in increasing the acid strength, but in just reducing the volume I have to work with.


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## Geo (Sep 19, 2014)

Silver will not escape in water vapor. If silver is in solution, you can evaporate the solution down to crystals of silver nitrate or with careful PH adjustment, crystals of elemental silver (and whatever was in solution).


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## rickbb (Sep 19, 2014)

Thanks Geo, I will continue with the evaporation. I don't think I will take it down to crystals due to the magnesium that may be present. Just a smaller volume to work with for the silver recovery.


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## g_axelsson (Sep 19, 2014)

Geo said:


> Silver will not escape in water vapor. If silver is in solution, you can evaporate the solution down to crystals of silver nitrate or with careful PH adjustment, crystals of elemental silver (and whatever was in solution).


I strongly question the second part. As far as I know just adjusting the pH does not reduce silver nitrate back to silver.

Göran


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## Geo (Sep 19, 2014)

I should have added "with heat". I'm sorry. 

According to wiki : Aqueous silver nitrate also decomposes when heated:
2 AgNO3(aq) → 2 Ag(s) + O2(g) + 2 NO2(g)
Most metal nitrates thermally decompose to the respective oxides, but silver oxide decomposes at a lower temperature than silver nitrate, so the decomposition of silver nitrate yields elemental silver instead.

http://en.wikipedia.org/wiki/Silver_nitrate Scroll down to reactions.


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## g_axelsson (Sep 20, 2014)

The text on wikipedia gives an incorrect picture... that an aqueous solution of silver nitrate would decompose didn't agree with my experience. That would make it almost impossible to dry silver nitrate crystals with heat and it would have presented problems with dissolving silver in nitric acid while heating the solution in the first place.

A bit of googling gave me the answer... (red text added for clarity) http://www.nist.gov/data/PDFfiles/jpcrd11.pdf


J. Phys. Chem. Ref. Data said:


> Qualitatively, decomposition is negligible in the solid state, but becomes appreciable 30-40° C above the melting point.


Silver nitrate melts at 209.7 °C (409.5 °F; 482.8 K) so it starts to decompose around 250° C and totally decompose at 440° C. I wouldn't call it an aqueous solution at those temperatures.

So, unless the solution is heated until dryness and well beyond there shouldn't be any noticeable amounts of silver precipitating.

Interesting reaction though... 8) 

Göran


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## Geo (Sep 20, 2014)

Wiki is flawed that way. If it says "when heated", it could mean "on the surface of the sun". Not really giving the temperature of decomposition really hurts the article. If I were expecting elemental metal from metal salts, the first thing to cross my mind would be calcining. That's the way I took it but that just shows my inexperience.

Perhaps since you caught that, maybe you can report it as flawed so that they can fix it.


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## g_axelsson (Sep 20, 2014)

Better up, it's a wiki and I'm going to fix it myself. 8) 

Göran


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