Silver Nitrate Recipe?

[bisjac]

i have 70% grade nitric acid, and .999 bullion.
what is a good acid to filtered water to silver bar ratio?


say i have 1TO bullions. easier to work with them grams as i dont have incrementals smaller then that.


this is for a cell electrode, for harvesting from sterling buttons.
i need a starter solution.

 

[philddreamer]

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=11281#p110212

Take care!

Phil

 

[goldsilverpro]

i have 70% grade nitric acid, and .999 bullion.
what is a good acid to filtered water to silver bar ratio?


say i have 1TO bullions. easier to work with them grams as i dont have incrementals smaller then that.


this is for a cell electrode, for harvesting from sterling buttons.
i need a starter solution.

Lets assume you're making a liter of solution. I would start a cell solution at about 2 TO of silver per liter. A troy oz of silver will dissolve in about 35-38 ml of 70% nitric acid and an equal amount of distilled water. Double this for the 2 oz. I would also add about 2g/l of pure copper (solid house wire). A gram of copper will dissolve in about 4ml of nitric plus an equal amount of distilled water. Double that for the 2 grams. After everything is dissolved, combine the silver and copper solutions and adjust the solution level to 1 liter.

 

[bisjac]

questions on this.

1) do i dissolve silver into the acid, then add the matching amount of water afterward?
or can i make the acid+water solution, then drop silver into it? (im unaware how/if acid reacts to silver the same once water is already added)

2) why would i dissolve the 1-2grams copper separately, to be added to the silver nitrate afterward? isnt the sterling buttons im using already going to foul my solution with copper over time? an effect we generally dislike?
(or does this have something to do with assisting the electro-conductivity up front, as copper is pretty conductive?)

just curious. i dont like to do what commonly works until i know why it works.

foresight;
is there a way to clean out the copper from a solution after its gotten way to used?
i notice how many users here save all junk solutions in a bin, so to cement some menial PM's later at mass. i only know how to receive silver cement lol.
i suspect i have nickel alloys in some buttons i have (no i wont necessarily be using my silver nitrate with it) likely look for other ways to recover non silver PMs

 

[butcher]

1) Do I dissolve silver into the acid, and then add the matching amount of water afterward?
Or can I make the acid and water solution, and then drop silver into it? (I am unaware how or if acid reacts to silver the same once water is already added)

Diluting the acid will dissolve silver better, mix the acid with the water to crate dilute nitric to dissolve the silver in, start cool, after reaction stops add heat.

2) Why would I dissolve the 1-2grams of copper separately, to be added to the silver nitrate afterward? Isn’t the sterling buttons im using already going to foul my solution with copper over time? An effect we generally dislike?
(Or does this have something to do with assisting the electro-conductivity up front, as copper is pretty conductive?)

In your first question you mentioned ,999 silver, not sterling silver, if you have some copper in your solution it is said to help in the form of silver crystals that form, too much copper in the silver-refining cell is a problem, GSP was giving a starting electrolyte solution assuming you had no copper in solution.

Too much copper in solution would contaminate the silver in the refining cell.

If too much copper in the electrolyte, the electrolyte would need replaced, the silver could be cemented from the electrolyte with copper, silver could then be recycled.

GSP and Harold as well as others have written enough information on silver cells to fill a book, searching for this information on the forum will give you the understanding your looking for.

I have not tried it yet but have read most of it.

 

[bisjac]

oh yeah my starter solution will be made from .999
but i will be using sterling buttons as anodes.

sry i didnt explain that well. but i do understand the need for a bit of copper to start with.

thx for all the help guys
lots of good reading, and the links you left.

 

[Geo]

from what i understand about the silver cell (the only experience i have is a very small one i experimented with) is sterling will cause the electrolyte to foul quicker. a better route to go would be to dissolve the silver in nitric acid and water and cement on copper and cast the powder into anodes. your starting with 99.5% and raising it to 99.99% with the cell.

 

[goldsilverpro]

If you ran a one liter silver cell, you would use about 2 amps and would produce about 8 grams of silver per hour, max, no matter whether you had sterling or 99% cemented silver in the cell. Assume you started the cell with 2 oz (65g) of silver. With sterling (assume an average of 91% with the remainder copper), the silver in the solution would be cut in about half (to about 32g/l) in 24 to 36 hours. Each gram of copper dissolved forces 3.4g of silver out of solution (there's only so much nitrate ion to go around). With the silver that low, you will soon start co-depositing copper if you continue running it. Therefore, you have to replenish the silver back up to it's starting point.

To replenish the silver, you have to bail out some solution and replace it with 32g of extra silver that you have dissolved separately. Another way to build the silver back up is to add a little nitric to the cell. It will dissolve some of the crystal that has already formed. For the 32g of silver needed, I would add about 32 x 1.22 = 39ml of concentrated nitric and gently stir it in. I usually add about 10-15% extra to make it a tad faster. If you use the add-nitric method, it will fume a little more for awhile.

However, during that time, you only added about 9.4 grams of copper to the solution. The limit of copper in the 1 liter solution, before it starts co-depositing, can be as high as 98g. Therefore, you can run about 10, 24 hour days, or more, before the copper becomes such a problem that the entire solution needs to be replaced. During that 10 days, you will have to replenish the silver about 8-10 times.

If you do as butcher says, the maintenance on the cell is cut to about 1/10 (or, 1/9) as much. You have about 1/10 as many replenishes to make and the solution will last about 10 times longer.

Whether you run sterling or dissolve first and run 99% cement, it will take exactly the same total amount of nitric acid, when all is said and done.

As far as starting the solution out with some copper is concerned. After daily controlling 12, 30gal silver cells for 5 years, I am convinced that copper is a desirable ingredient in the solution. With a little copper, the crystal is harder, denser, and shorter. This does several good things. It becomes more rinseable and, due to the greater bulk density, you can get more in a crucible. Also, you can go a bit longer before shorting becomes a danger. The pile of crystal is flatter in a Thum cell and, in a Moebius cell, the stringies are reduced and the crystal falls off better.

When you produce grayish, fluffy, stringy crystal, it's much harder to rinse and, therefore, harder to get pure. If you started with 8 grams of copper/l and ran 99% cement silver, you would get 90 days instead of 100 before the solution craps out. Big deal. To me, the better crystal is worth it. I'm not using the crystal for inquartation and I want it to be pure the first time.

Note: I did the math in my head and rounded stuff off. I just wanted to show the way things worked and wasn't too interested in 100% accuracy.

 

[bisjac]

My dilemma, is deciding if i would prefer just using sterling anodes, or 99% cemented anodes.
That was my concern, the usage of nitric, as it is quite expensive.

my first batch of scrap i have is just over exactly 100grams of sterling.
i intended to do a 1liter cell.
and i have plenty .999 bullion to use in assistance.

im just putting together an affordable plan.

 

[goldsilverpro]

Like I said, it will take the same amount of nitric in either case.

Once you decide, do you know how you're going to set up the cell? How are you going to melt? What are those sterling "button" anodes and what do they look like?"

There's lots on the forum about silver cells and quite a few good photos. You really should look it over.

In the 80s/90s, when I had my last refinery, I had one 30gal silver cell operating most of the time. I'm not big on sleeping with silver cells so I usually ran it about 12 hours.day. I probably averaged about 1000 oz/week, mainly from sterling, big contact points, and x-ray film. Most of my silver was cast into 10 and 100 oz bars and sold at a premium. When I first started the refinery, I ran the sterling straight through the cell. Replenishing the cell every couple of days got old fast. I soon switched over to dissolving the sterling and the points and cementing the silver out with copper.

The 2 processes are sort of, six of one, half dozen of another - same amount of acid, same amount of dissolving. In practice, though, semi-purifying the silver before putting it in the cell takes a lot less labor, when all is told, and it is easier.

 

[Harold_V]

With a little copper, the crystal is harder, denser, and shorter.

I'd fight you to my death over that comment. I processed WITHOUT the addition of copper and watched with each iteration as the silver crystals grew softer as copper accumulated. Never, once, did the absence of copper create soft crystals, and, in fact, it was the complete opposite. The first silver to be deposited was a sheet that was difficult to remove, followed by coarse crystals that adhered tightly to the cathode. As copper content rose, the crystals were much easier to dislodge, and as the copper content grew greater, thin threads of silver were the result. These results were consistent, time and again, as was my procedure. Had you made electrolyte without copper content, you, too, would have experienced much the same thing.

I'm not suggesting, not for a moment, that copper is the wrong approach---I witnessed the positive side of its use. I also witnessed the shorter electrolyte life, the result of copper accumulation.

I'm all for detailing the benefits of copper, but I'm not too keen on information I found to not be true. Copper does not make a harder deposit. It never did, not once, not for me. Do note that I also used a generous amount of silver in my electrolyte (30 ounces in about 2½ gallons).

Harold

Edit:
As an afterthought----can there be a connection between the industry standard for silver (999) and the process involved? The standard for electrolytic gold is 9999. I am of the opinion that the 999 standard for silver is due to the use of copper to improve conductivity, which also encourages co-deposition of copper. Thoughts?

H

 

[goldsilverpro]

With a little copper, the crystal is harder, denser, and shorter.

I'd fight you to my death over that comment. I processed WITHOUT the addition of copper and watched with each iteration as the silver crystals grew softer as copper accumulated. Never, once, did the absence of copper create soft crystals, and, in fact, it was the complete opposite. The first silver to be deposited was a sheet that was difficult to remove, followed by coarse crystals that adhered tightly to the cathode. As copper content rose, the crystals were much easier to dislodge, and as the copper content grew greater, thin threads of silver were the result. These results were consistent, time and again, as was my procedure. Had you made electrolyte without copper content, you, too, would have experienced much the same thing.

I'm not suggesting, not for a moment, that copper is the wrong approach---I witnessed the positive side of its use. I also witnessed the shorter electrolyte life, the result of copper accumulation.

I'm all for detailing the benefits of copper, but I'm not too keen on information I found to not be true. Copper does not make a harder deposit. It never did, not once, not for me. Do note that I also used a generous amount of silver in my electrolyte (30 ounces in about 2½ gallons).

Harold

Edit:
As an afterthought----can there be a connection between the industry standard for silver (999) and the process involved? The standard for electrolytic gold is 9999. I am of the opinion that the 999 standard for silver is due to the use of copper to improve conductivity, which also encourages co-deposition of copper. Thoughts?

H

I retract the word "harder" from my statement, mainly because I realize that you think of this term as related to such things as Vickers or DPH hardness. I shouldn't have used it. However, that doesn't change my basic argument.

A few of the quotes from T.K. Rose: "An electrolyte containing 60g Cu and 60g Ag per liter shows good conductivity and gives heavy, dense silver crystals." "Increase in silver content of the electrolytes causes the production of coarser crystals, while with the additions of copper the aggregates are more compact." "Mulligan(?) states that an increase in the copper content from 55 to 75gpl resulted in a better production of silver crystals." Whatever that means.

From Butts and Coxe. There is a chart which lists 5 large silver cell operations, including ASARCO and INCO, and the make up and operating conditions of each. The intentional copper concentration ranges from 7 to 80gpl in these facilities. In all cases, the anodes only contain Ag, Au, and Cu. In the anodes, the Ag ranges from 94% - 98.5%, the Cu from .3 to 1.2%, with the remainder Au. Quote: "The productions of the refineries described above range between 999.4 and 999.9 silver, with copper as the major impurity." It also says that - "The variations in silver and copper nitrate, and the ratio of one to the other, are based on obtaining certain objectives, such as:
(1) Efficient anode reaction
(2) Type of deposit desired for removal routine
(3) Consideration of anode impurities
(4) Maximum conductivity with minimum silver tie-up"

Harold, I've thought a lot about this. In looking at your cell, I think that, due to it's uniqueness, it is apples and oranges compared to the Moebius and Thum cells used in industry. The main difference I see (correct me if I'm wrong) is that the ratio of cathode area to anode area in your cell is much larger that the approx 1:1 in the Moebius cell and the approx. 1.5:1 in the Thum cell.

Besides the solution make-up, the factor that alters the deposit characteristics the most is the cathode current density, which (on average) is the total current divided by the area of the cathode. For the same amount of current, a larger cathode will have a lower current density than a smaller cathode. I don't know what your cathode area is, but if it's, say, 3 or 4 times greater than the anode area, the crystal characteristics could be appreciably different. If that is the case, I would think the data you've obtained would not necessarily be valid when applied to a traditional Moebius or Thum cell setup.

I'm not saying that your cell is good or bad and it obviously worked for your purposes. However, unless one has a SS cell exactly like yours, the results could be very different.

I usually started my solutions with 30gpl copper and got excellent crystal results. I had no way to determine whether or not I had 999.9 or not, but I always dissolved some well rinsed crystal, made a portion of this solution ammoniacal, and looked for any trace of blue against a white background. I never saw any blue unless my solution was completely out of whack, which was rare.

At one time there were probably 100s of 1000s of silver cells in existence. Silver cells are probably one of the most-studied piece of equipment ever. Everything was tried and the system was perfected - solution makeup, cathode/anode area ratio, electrode spacing, shape of the tank, anode and cathode current densities, etc. The closer you can come to these same parameters, the closer you come to achieving success, even with small systems. From all the patented systems, they ended up with only 2 types, the vertical Moebius and the horizontal Balbach-Thum.

In every case I've ever found, copper was intentionally added to the solution and the average amount they added was huge - 50-60gpl. Why would they do this if the added copper didn't produce benefits? After all, their solution wouldn't last as long. Or, would it? They probably kept the solution perfectly balanced by frequent removal and replacement of specific amounts of solution, based on knowing the material going in and, most probably, analysis. Also, Rose says the older the solution, the better it works. He says this is possibly due to the buildup of ammonium nitrate.

The more I study these cells, the more convinced I am that some added copper is very desirable. I would strongly recommend that anyone building a cell add some copper.

 

[Harold_V]

In keeping with some of your thoughts, not only did I have a large cathode to anode ratio, but I chose to run well under the recommended amperage. My memory has grown quite dim, but I believe I operated @ 25 amps/sq. ft of anode. I found it reduced bridging, which, to me, was quite valuable. I ran my cell 24/7, so by lowering production, I could sleep through the majority of the night without worrying about shorting. It also meant that I'd run the cell for a couple months at a time, because of the reduced production, but it was worth if considering my circumstances. To be clear, I did not part silver continually. I'd wait until I had several thousand ounces poured as anodes, then part until it was finished. Did that maybe twice a year.

That copper is needed in electrolyte there is no doubt. That's why I mentioned the typical production I experienced each time I changed electrolyte. The production at first, where there was no copper in solution, was less than desirable, forming sheets of silver. However, because copper was constantly being added, I took advantage of that fact and permitted the less than desirable growth. I used it, along with any strings that may grow towards the end, to produce the next round of electrolyte, so I had nice crystals (of high quality) to store. The sheet silver represented a low percentage of total production, so it was consumed, along with proper crystals, in making the next batch of electrolyte.

In my case, because my silver was always contaminated with platinum metals, primarily palladium, I wasn't afforded the luxury of changing portions of the electrolyte. I did wholesale changes, always. The buildup of palladium was so rapid that there were occasions where I had to rerun the crystals to eliminate palladium that had co-deposited. The lesson learned was to try to keep palladium at a low level, thus my cemented silver was never used for inquartation, for all that did was increase the level of concentration. I ran a lot of dental gold, as you might imagine.

Thanks for your comments, Chris. I think that you and I actually agree pretty much on all of this, and that I may have been at odds over the description of hardness of crystals. There was no question in my mind that copper played a role in how it grew---and especially how it made harvesting easier. There was a point where the crystals literally wiped off the cathode, almost effortlessly. However, that was very close to the point where the cell started growing long strings, which, for me, signaled the end of the useful life of my electrolyte.

In support of the use of copper---when you consider the huge volume of electrolyte that is used by major producers, it stands to reason that they'd use copper in place of silver, if for no other reason, economics. It does improve conductivity, and there's no question that it causes crystals to grow with less tenacity. I am also of the opinion that the industry standard for silver is reflected in the lower quality that is produced from the cell as compared to the potential. A small amount of copper is allowed to facilitate production, thus the 3n's instead of 4n's.

Harold

 

[bisjac]

An update to my cell.
I have completed the assembling, based off my studying of many topics in the forum here
(this is my first attempt at a cell, and I will be running it for the first time tomorrow morning)
this experiment is an educational run for me.i am aware that i am possibly using twice the size then necessarily, especially for my small amount of silver im beginning with. but i do intend on refining more at once in future cell-runs, and regularly.

have 70% nitric acid on hand.
have 106-gram sterling button prepped.
have 1TO bullions on hand.

As apposed to my considering running the sterling button through the cell;
I have decided to to instead go the route of dissolving the button, and cementing to 99% as an anode (as popularly suggested by many of you)

ill describe my cell;
-I have it within a 2000ml pyrex beaker.
-I am using lasersteve's graphite+wire cathode for my negative.
-I have a plastic basket, with holes drilled, with 1time use cloth within to catch.
-The basket is held up near the top by a horizontal graphite rod, that my positive wire is attached from the end sticking out from the side.
-The plan is to hang anode(s) of 99.0 silvers from a soldered on conducting hook, that will hang from the graphite rod from within the basket and within the solution.
-I am using a modified PC power supply that i have prepared wires for a 3.3v or a 5v attachment if needed (im still undecided whats best)

My plan? bare with me, this is where i may be doing things wrong or inefficient;
- I will prepare a solution. 70ml of 70% nitric acid + 70ml filtered water
- i will dissolve my 106gram sterling button in what im thinking is enough solution.
- cement out much as i can with clean copper
- re-pour a 99.0 anode bar(s)
--------------------------
- add 80ml nitric acid and 80ml filtered water to the left over copper nitrate solution
- dissolve 2TO silver bullion into solution
- pour the whole solution into the 2000ml cell, and add filtered water to fill to the 2000ml line.

*run cell



ok.
I dont have a starter solution to renew or upkeep. so at the start here i am assuming i need to prepare both my anodes and my electrolyte. and i am attempting to do so without waste.

any last minute (hours) advice from anyone? i welcome everything you guys have to say.

 

[publius]

Filtered water may contain Cl ions, filtering will not remove chlorides. It is best to use distilled water for all the operations involving dissolution of silver in Nitric Acid. Tap water is acceptable when washing silver chloride (AgCl).

 

[philddreamer]

Bisjac, I echo Publius' advised, "don't use filtered water"; distilled water is what you must use when digesting silver with nitric acid!
If you're precipitating silver Cl, you can use tap water after the digestion; but, if you plan to cement the silver with copper, you must use distilled water. For rinsing the silver after cementing, then you can use tap water.

Don't run into trouble from the get go by using other than distilled water.

Take care!

Phil