# formula for dissolving silver in nitric.



## torscot

I've just spent a bunch of time trying to find the formula for dissolving silver in nitric. Honestly I'll write it down this time. How many ML of nitric per gram of silver to dissolve? I have seen it so many times here, but now that I need it I can't find it, I've spent too much time trying to find it. Please and thanks. I want to make up my silver nitrate so that I can start up a "stainless bowl" system. the system looks so simple I have to try it. I have everything else but that.


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## rusty

torscot said:


> I've just spent a bunch of time trying to find the formula for dissolving silver in nitric. Honestly I'll write it down this time. How many ML of nitric per gram of silver to dissolve? I have seen it so many times here, but now that I need it I can't find it, I've spent too much time trying to find it. Please and thanks. I want to make up my silver nitrate so that I can start up a "stainless bowl" system. the system looks so simple I have to try it. I have everything else but that.[/quote


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## goldsilverpro

Takes about 1.22ml of 70% nitric acid plus 1.22ml of distilled water to dissolve 1 gram of silver. This is not exact and will depend on your setup. For example, if the dissolving container is covered, it could take less.

200g/l of silver nitrate is about 127g/l of silver. That much could be used in a cell but only using 50-60% of that would work fine. I wouldn't worry about the exact nitric acid content in the cell. Just don't use an excess of nitric when dissolving the silver and you should be OK.


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## torscot

Thank you gentlemen. Those are the numbers I needed. and I have already printed them, Now it's my fault if I lose them again. There may be a few other questions as I learn my way through this. I have a good process for recovering my silver from scrap, learned from the posts on this forum, and after a year of tweeking and a few oop's, it now works very effectively. Now I need something else to try. I just got my DC power supply in the mail yesterday.


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## Lou

Less than 4.9 M:

3 Ag + 4 HNO3 --> 3 AgNO3 + 4 NO + 2 H2O

Over that it is:
Ag + 2 HNO3 --> AgNO3 + 2 NO2 + 2 H2O

As you can see, dilute nitric acid is more efficient for dissolving metals like silver and copper, insofar as consumption of reagent. Less NOx produced is also a benefit.


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## goldsilverpro

Thanks, Lou. I didn't know the exact cutoff. So, 4.9M is about 30/70, HNO3/distilled water.


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## SilverNitrate

An easy thing to remember is 1ml of conc. HNO3 for 1g Ag. 
If dissolving sterling silver, your acid will limit out and you will need to a bit more (about 15% more) to totally dissolve it.


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## solar_plasma

> 3 Ag + 4 HNO3 --> 3 AgNO3 + 4 NO + 2 H2O



But what is the formula for silver reaction, if H202 is involved? I have often used it, when I wanted to accelerate dissolving of Ag80-90/rest Cu, avoid NOx and didn't want to heat extended time - like "drop and forget". I always expected the extra O• radical(?) would oxidize NO to NO2, which dissolves to HNO3 (+HNO2, which maybe oxidizes to HNO3 as well?), so that 1mol Ag takes 1mol HNO3, if covered and ideally no NO2 escapes. Otherwise I read, that H2O2 can build two OH• radicals. The nature of H2O2 confuses me. Would be nice to learn something about it.

Edit: Is this the answer? http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=50&t=17374&start=20 Looks to simple, I guess, it is not that simple.

often is is said, that H2O2 works as a catalyst, but as far as I tell my pupils, a catalyst will not be changed in a reaction - H2O2 will be changed. Looks more like an additive to me, that gets the 
ball rolling.


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## butcher

Hydrogen peroxide is not that complicated to me, it is water with an extra oxygen.

Water now there is a strange solution, it can react as an acid or a base.


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## solar_plasma

> Water now there is a strange solution, it can react as an acid or a base.



...and also form ion clusters with itself like the reactant ions in the ion mobilization spectrometer I have mounted on "my" cbrn-exploration car, - very strange this H2O. Yes, you are right, in practice its just additional oxygen, but I wonder about it's chemistry. Maybe sometimes it's more exiting to me,why it works, than that it works :lol: ....sexy little H2O2 thing has catched my interest now.


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## torscot

It's getting a little over my head now, but, I got the info I needed and the nice part is after reading posts like this for a year I understand the formulas coming up now. The reason for this post was to set up one of the stainless bowl systems. I bought the bowl at Value Village (Canadian equivalent of Goodwill) $3.99. A variable power supply off ebay. Some scrap Plexiglas that was in my workshop, some rubber, the bottom off an old plastic ammonia bottle and today I poured five pretty little bars for 756 grams. You can see the silver crystalizing on the bottom of the bars. I had to stop the process as the bars I was using for anodes were a little more impure than I thought and I polluted the solution when I moved the bag and sent a cloud (lesson learned) of crap into my painstakingly filtered nitrate solution. Only time I was worried was when I went to remove the deposited silver from the inside of the bowl. A plastic scraper like the other post said to use didn't work! A screw driver just chiseled its way down the inside. So I got a chisel and decided I was in deep trouble. So I tapped the bowl on the outside a few time with the handle. Turned it upside down and tapped again. Out popped a perfect silver bowl. in one piece!

I collect metallic minerals. The silver that I am refining is coming straight out of the rock. My scrap material comes from cleaning and preparing my mineral specimens. Mother nature has provided us with dendritic silver. A form of native silver that is very uncommon to find. These are natural silver crystals formed over thousands of years, then encased in Safflorite (cobalt, arsenic CO AS2) then entombed in calcite. I have a slabbed (cut) specimen that has two crystals each 6" long. 
What would be the best setup to grow crystals for display? Yes, I know they are not strong, or durable. but cased and properly displayed, I think they could be quite marketable at mineral and gem shows, Especially with the silver specimens being self collected and self refined and from a Canadian local. 

Here's the question. How do I grow a decent sized silver crystal repeatedly ? one inch minimum, with a decent fan. good looking.


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## kadriver

goldsilverpro said:


> Takes about 1.22ml of 70% nitric acid plus 1.22ml of distilled water to dissolve 1 gram of silver. This is not exact and will depend on your setup. For example, if the dissolving container is covered, it could take less.



Chris, I have used this figure (1.22ml concentrated nitric acid) and it dissolved all the sterling in the batch completely.

But when I added copper to begin cementing, there was much free nitric acid still left and it consumed my copper and produced visible brown fumes. The solution became very hot. Also the silver began to float and it was re-dissolving as soon as it cemented. The resulting cement silver was very finely divided and hard to clean.

If I want to dissolve 500 grams of sterling I begin by incinerating the clean sterling and adding it to 500ml of distilled water in a suitable heat resistant container.

Then I begin adding concentrated nitric acid in 50ml increments on low heat, tapering off the amount added toward the end of the reaction and increasing the heat. As always, I cover my container with a saucer or lid or watch glass.

I know that the nitric acid has been nearly completely used when there are no more brown fumes in the heated reaction container, and there are a few bits of undissolved sterling left in the bottom of the container.

Sometimes I will overshoot and end up with no sterling bits left. If this happens, then I'll add a few more pieces of sterling to the hot liquid and wait until the acid is used completely.

With 500 grams of sterling as in this example, I have used as little as .7ml to as much as a little over 1ml of concentrated nitric acid to get the sterling dissolved as described above.

This procedure can consume the nitric acid so completely that the silver will not cement when the copper is added to the solution. Some free nitric is required to get the cementing reaction started. If this happens, then I can add a few drops of concentrated nitric acid and stirring to get the cementing reaction going.

While this process takes a little more time, it does cut down on the amount of nitric acid I use and the amount of waste created.

Not to impune what you have calculated or written, but to help the newcomer who may have spent much time painstakingly making their own nitric acid, or paid as much as $100 for a half liter of nitric (like I did when I first started refining).

Respectfully, kadriver


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