# Nitric acid question



## Oz

First I should explain what I have done first. 

I started with the recipe for nitric acid of:
½ cup sodium nitrate dissolved in 16 oz hot distilled water, add 1 quart battery acid.

I then converted to the same units of volume and divided by a factor of 4 as below to make a small test batch.

½ cup = 4oz / 4 = 1oz or 6tsp or 2tbsp 15-0-0 nitrate of soda fertilizer
16oz / 4 = 4oz or ½ cup tap water (I did not have distilled)
32oz / 4 = 8oz or 1 cup new battery acid (assumed to be 35.5%)

I heated the half cup of water to boiling then stirred in the sodium nitrate until completely dissolved. I then poured the cup of battery acid into the still warm sodium nitrate solution. I stirred and let equalize for ½ hour. 

As a test I put a Ben Franklin half dollar ( .90% silver, .10% copper )into the solution which was now at 60F. There was no reaction for the first 10 minutes, after 1 hour there was a white precipitant around the edge of the coin. Upon stirring the precipitate dissolved and I noticed a faint chlorine smell. To give a better idea of the rate of reaction the coins pattern on the face was only vaguely legible at this 1 hour point.

My questions……

This seems weak to me do I have proper proportions for making my acid?

Is their too much NA in this solution since I am smelling chlorine?

Any input is appreciated! 

Thanks!


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## agpodt77339

You forgot the cooling and removing salt step. 

Here is a link to a post Steve wrote on how to make nitric.
http://tinyurl.com/34zajp


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## Lou

There is no chlorine you are smelling for there should be no chloride to be oxidized to chlorine.


Instead, you are smelling nitrogen dioxide. To the inexperienced, it smells like chlorine I suppose. 


Indeed, you need to cool your solution, dropping out sodium sulfate in the process.


Lou


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## Oz

agpodt77339,

Thanks for the link, that’s great! It makes sense that it is too high in Na since the slight chlorine smell. I have removed the coin (about a third gone) and all is cloudy with white precipitate. Any suggestions as to how to save the solution? Would the dissolved silver and copper precipitate out with the excess salt at this point in the freezer?


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## Absolutsecurity

Ypou need to stop disolving coins - they are worth more as coins usually! LOL!

Glynn


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## Oz

Absolutsecurity,

Not this one! Beat to death it was.


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## Absolutsecurity

OZ,

Good deal then

I would melt it first that would incinerate any oils or other contaminants that would inhibit it dissolution and pour it onto swirling ice water - that would make flakes - so it disolves easier.

Then you have to work on your nitric process better! Go to Steve's site - http://www.goldrecovery.us/ - He has a wealth of info that is 100% indispensible and I highly reccomend you browse his site and videos and then get and read Ammans or Hoke's books - its alot easier and you make less mistakes.

After you do some small batches and get the hang of it you will notice that it is second nature and almost calming to refine - at least thats my experience.

Glynn


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## Oz

When making nitric acid in this way what exactly is this white precipitate and is it worth saving for other refining procedures?

Thanks


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## peter i

Mixing a nitrate with sulphuric acid will liberate nitric acid and form the sulphate salt of the metal ion from the nitrate.

If you do not remove the sulphate ions, and start dissolving silver in the soup, your silver ions will precipitate as insoluble silver sulphate (the white stuff).

If you want clean nitric acid with that method, I guess you should distil the acid mixture. Surplus sulphuric acid and sodium sulphate will stay in the boiler, and nitric acid (and water) will boil off, condensing again in your condenser.
Any trace of sulphate ions will precipitate silver as silver sulphate from your solution.


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## Oz

If I understand what you are saying correctly then I will always get an insoluble silver sulphate using this method of making nitric acid, even if I place it in the freezer and decant off the acid leaving behind the excess salt. 

I had planned on dissolving my silver in this nitric acid and precipitating it out with copper as in Steve’s video. 

What am I not getting here?


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## peter i

I have not tried it, but I find it hard to believe that cooling should remove all the sulphate ions.


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## lazersteve

The cooling process if done correctly (cold enough, -5 C and long enough, 1 hour) should remove all but a small amount of the sodium sulfate. 

Look at the solubility curve for sodium sulfate and this will be clear. In 100 mL of H2O at -5C less than 3 grams of Na2SO4 will remain in the liquid. If you take the temperature lower you can force even more of the sodium salt out. These temperatures can be produced with very little effort using the techniques listed here:

Cooling Baths

As you can see from the chart, temperatures as low as -77 C can be reached using dry ice and acetone two very common compounds. Even salted ice can go down to -20 C.

At room temperature (~20C) 20 grams of the sodium sulfate remains in the liquid.

Distillation would remove the last of the sodium sulfate, but I have had good results with out doing so. 

The link below is a short video showing the addition of sodium sulfate to silver nitrate at STP. The results show no reaction.

NaSO4 +AgNO3 Video

The key to getting the nitric acid strong in the cold is careful control of the reaction conditions and accurate measure of the reactants. 

Remember that more is not always better in chemistry. Use your equipment (thermometer, graduated cylinders, accurate scale, etc.) to control every variable that you can and you will get good, consistent results.

Steve


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## Irons

That may be Silver Chloride precipitating out.

Test your Sodium Nitrate to see if it has any Sodium Chloride in it by dissolving some and adding a drop of silver nitrate solution to see if it precipitates out.

You will find that most agricultural Sodium Nitrate has a considerable amount of Sodium Chloride.


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## Never_Evil

For people that have made the poor mans nitric successfully, would anyone be interested in making a video showing all the steps?


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## Noxx

I did once... But my plastic bucket leaked and I lost all my nitric acid...

Sorry


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## Oz

Instead of trying to compensate with the small batch I tried at the top of this post I would like to try Steve’s method. However I only have 35% sulfuric acid available to me at this time and don’t have the means to distill yet. What would the proportions be using the weaker 35% sulfuric acid? Could the sodium nitrate be dissolved directly into the sulfuric acid to minimize water? Or is this a waste of time until I can distill my acid to a higher purity? 

I will have to try Irons suggestion to check how contaminated my sodium nitrate may be with sodium chloride but have not been able to find any silver nitrate in a small affordable amount yet.

Thanks again


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## Anonymous

read through the forum, you do not actually distill the acid you heat it in a glass container to drive of the water. It is fairly easy to do, you just have to be careful hot sulfuric is nasty.


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## Oz

James,

I took your advise and did a forum search with the “Distilling and sulfuric” I came up with 2, this thread plus 1 other. In the other thread it was touched on but predominantly dealt with cementing silver out of nitric acid. 

I do seem to remember reading somewhere about the temp and concentration being critical. That you could evaporate off water at just under 100 degrees but as the acid concentrated you had to keep lowering the temperature to keep from evaporating the acid. At some point in this the concentrating acid has a lower evaporation point than the water and even carefully controlling the temperature you start evaporating acid instead of water. This is just vague memory here which is why I’m asking the forum. If you know where in the forum I can look it would be appreciated.


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## banjags

sulfuric acid boils at a much high temp then water if I remember correctly so you wouldnt really need to worry about the acid boiling


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## Oz

Well I found a very good site for concentrating sulfuric acid http://www.amazingrust.com/Experiments/how_to/Concentrating_H2SO4.html that I thought others might like as well. 

I have some photo grade silver nitrate on the way in the mail now. If Irons is reading this I would like to do the test he suggested to see how pure my sodium nitrate is or if it is contaminated with sodium chloride. Some further instruction would be appreciated. Of course I understand dissolving my sodium nitrate in water, but wonder about adding the silver nitrate to see if it precipitates. Should the silver nitrate be in solution first, if so just distilled water? Proportions? 

Sorry if I’m asking stupid questions here but I hate making assumptions and want to try to remove as many variables as possible.

Thanks


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## peter i

Dissolve silver nitrate in distilled water, a 0.5 molar solution is what I use, in an eye dropper bottle.

Place a drop of the solution you want to test on a black glaced tile or similar* (a piece of glass on a piece of black paper will do the job too), then add a drop of the silver nitrate solution to it.

A white precipitate (drop becomes milky) is positive test for chloride (precipitate is silver chloride).

Edit: 
iodide and bromide will give a yellow precipitate and Sulphate will also precipitate white with silver in higher concentrations.
Silver halides will dissolve if you add a drop of ammonia, silver sulphate will not.

*IKEA sell a nice black dinner plate that is great for this test 8)
http://www.ikea.com/webapp/wcs/stores/servlet/IkeamsSearch?storeId=14&langId=-12&catalogId=11001&searchType=product&pageNumber=-1&orderBy=score&category=%23%7EProducts&query=sort+tallerken


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## Anonymous

I believe I read how to concentrate the sulfuric from battery acid in the tutorials. Look through them carefully the information is there because I learned it from this forum.

I will try and duplicate my initial searches to see if I come up with the right thread.


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## lazersteve

Here's the link:

Sulfuric Acid

Catfish won a forum contest with this tutorial.


Steve


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## Oz

I am just beginning in chemistry so if you could please indulge me, I would not know how to make a 0.5 molar solution. I do have the ability to weigh to a 10th of a gram accurately, as to volume sad to say I need burettes (sp.) as I am using a kitchen measure cup in ml currently.

As to iodide and bromide, it is nice to know the color indicators for this solution but are you suggesting I may have difficulty seeing the color difference? 

From what you are saying if I get a mixed precipitate I can re-dissolve the iodide and bromide (halides?) with ammonia (household concentrations?). If I then washed the remaining precipitate with distilled water I should only be left with silver chloride or silver sulfate? Suggestions as to how to tell if I have a silver chloride or silver sulfate left? 

Peter, Thanks for the tip on a black background!

Steve, Thanks for the link! It’s even more detailed than what I had found elsewhere.


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## lazersteve

Oz,

One mole of silver nitrate weighs 169.88 grams. So 0.5 moles is :

169.88 * 0.5 = 89.94 g

In chemical terms the upper case M stands for Molarity or Moles Per Liter.

So a 0.5 M solution of silver nitrate is 89.94 g of AgNO3 with water added to the 1 Liter mark (approximately 1000 mL - 19.6 mL = 980.4 mL). The 19.6 comes from the specific gravity (4.35 g/mL) of AgNO3 (89.94g / 4.35 g/mL =~ 19.6 mL)

Steve


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## peter i

Oz said:


> I am just beginning in chemistry so if you could please indulge me, I would not know how to make a 0.5 molar solution. I do have the ability to weigh to a 10th of a gram accurately, as to volume sad to say I need burettes (sp.) as I am using a kitchen measure cup in ml currently.



Steve gave the recipe, and I'm sorry that I did not. When it's daily routine I tend to forget that molar concentrations are not the usual measure.

No need to be exact, you are only testing qualitatively to see if it is there or not (another lab-habit: .5 M can be anything from 0.45 to 0.54M. 0.500 is on the other hand an exact concentration, or rather from 0.495 to 0.504 M)


> As to iodide and bromide, it is nice to know the color indicators for this solution but are you suggesting I may have difficulty seeing the color difference?


Yes, especially if it is in a green/blue/yellow solution or of unknown concentration.
But a positive test show that they are there (one or more of them, most likely chloride)



> From what you are saying if I get a mixed precipitate I can re-dissolve the iodide and bromide (halides?) with ammonia (household concentrations?). If I then washed the remaining precipitate with distilled water I should only be left with silver chloride or silver sulfate? Suggestions as to how to tell if I have a silver chloride or silver sulfate left?



silver chloride, -iodide, and bromide are all silver halides, and will dissolve in ammonia.
Silver sulphate will not.
This allows you to see if it is sulphate or halogen that cause the precipitation.



> Peter, Thanks for the tip on a black background!



My pleasure


And another tip:

When cementing silver with copper, test the solution for remaining silver in exactly the same way, but use a dilute hydrochloric acid as reactant. Any remaining trace of silver in the solution will give the same reaction (the silver chloride don't care where silver or chloride comes from. If both are present, they will precipitate)


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## Oz

By all means please don’t stop with the finer points. I don’t mind at all if you continue using moles, but please include the molar weight of the compound as well. I’m not just here for a recipe I love seeing the details. I’ll have to play around with some of this using the periodic table of elements as I wait for my silver nitrate to arrive. As money is tight right now for reference book buying does anyone know a good online source where I could find solubility charts for the different salts at varying temperatures. I had in mind trying to purify my sodium nitrate along the lines that Steve is using in his poor mans nitric acid recipe to remove the excess sodium and sulfide.

Thanks again


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## goldsilverpro

Some old downloadable Google books of Solubilities

http://books.google.com/books?hl=en&id=d1JMAAAAMAAJ&dq=solubilities&printsec=frontcover&source=web&ots=BSNxePB4lB&sig=Sy90gRGtSQshDPiIno_3Hx_urLQ

http://books.google.com/books?id=7L0MAAAAYAAJ&printsec=frontcover&dq=solubilities+inorganic&lr=


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## peter i

The molar mass can also be found on wikipedia for any common chemical (and the basic characteristics of the chemical. Use wiki-data with caution, but normally it's quite good)


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## Oz

Ok, I got my .995 silver nitrate today so went at the fertilizer. To keep it as precise as possible (with what I have at hand) I mixed up a solution of 1 cup distilled water and 2 tablespoons of Bonide brand 15-00-00 nitrate of soda and stirred until dissolved. I also made up a 0.5M solution of silver nitrate and distilled water using Steve and Peter’s directions. In a black plastic melon ball scoop I placed 5ml of the nitrate of soda solution and added to it 1.25ml of my silver nitrate solution. In order of reactions....

Bottom Pic: After adding silver nitrate, As you can see it curdled immediately.

2nd pic: After I added 5ml of household ammonia. It cleared in a blink of the eye.

Top pic: Here it is after 2 washes in ammonia (setting in 2nd wash)

Since I did not dry and weigh between steps I can only guess but it was pretty close to a 50% reduction of solids after the addition of ammonia. I did not notice any other colors through the process Peter. So it would seem in that I did indeed have 50% of my precipitate as a chloride. 

So I guess that leaves me with trying to separate the nitrate from this solution (perhaps in freezer) or distilling as Peter had originally suggested. Would the chloride cause a problem if I used distillation? 

I hope this comes out OK as it is the first time I have tried to attach pics.

Thanks,
Dave


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## Oz

Sorry about the goofy order, I should get it right next time. At least I found edit. By the way how worried do I need to be about this quote I found “Silver Nitrate is soluble in Ammonia (Forms explosive di-amine silver upon drying!)”


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## calgoldrecyclers

Dave,
are you thinking of silver nitride? or ammonical silver nitrate?
silver nitride will form over a period of two to three hours.
however, for the formation of silver nitride, you are missing a key ingredient. 
on a safety note: ammonia should never be added to oxidizers.


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## Oz

It was a caution I had read from a supplier when I was looking for the cheapest price on high purity silver nitrate. There are several procedures that are being done by members here that use ammonia as a wash to remove traces of silver salts from precipitated gold. What I just did for testing nitrate vs. chloride could have in theory made di-amine silver nitrate if I understand correctly. I do have everything in very small amounts and the nitrate portions very diluted with water and disposed of just to be sure. 
I used to have a bit of fun with ammonia and crystalline iodine soaking paper in this and letting dry. The warning I saw on the silver nitrate reminded me of this considering all the filtering that is done by members, leaving the filters to dry for later recovery by incineration. The ammonia iodine is something that you do not want to filter through paper and let dry and I would not even trust it in solution in a glass stoppered jar due to the possibility of crystallization near the lid, sensitivity is extreme. 
I am not a chemist but do know more than your average citizen about explosives as I had a research physicist as a father that specialized in inventing new explosives for our military. A lot of what is done with chemical refining of precious metals walks down a fine line with explosives manufacture and I want to keep everyone safe. I am hoping that someone here that is a chemist can provide some answers on this as I am not familiar with this compound. 
I am comfortable with heavy dilution but want to know if it is needed or if those that may be filtering this and letting dry may have a potential problem.


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## calgoldrecyclers

Dave,
i couldnt agree with your statement ' alot of what is done with chemical refining of precious metals walks down a fine line with explosives manufacture' more. it is a very slippery slope. nitric acid being one of the more dangerous of the acids. 
i read somewhere, a report of silver nitrate being mixed down with ammonia under heated conditions without reaction.
i will see if i can locate it and let you know. 
in the mean time, you may want to check out this site:
www.chem.leeds.ac.uk/ or www.lycoming.edu

good luck,
Ezra


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## Lou

Oz, Peter and I have written a thread about ammoniacal silver solutions.
Search up "Tollen's" by Lou and you should find it.

I have a couple pounds of ACS grade AgNO3 if you want it Oz. I only want 98% of the spot value of the silver metal in it.


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