# My silver disappeared after dropping



## B1G JV (Jun 3, 2012)

I'm still new to this and after processing 1000g of silver I started my second batch of 1000g and then the silver that i dropped disappeared!? Which has thrown me slightly. 

Here's what I've done so far...... 

-Sterling silver melted down in a furnace and poured into shot.
-Shot placed in 5 liter beaker with a 50/50 mix of nitric and water and left to dissolve.
(after leaving this batch for a few hours after the silver had dissolved, white crystals grew in the bottom so the next day I gently heated the solution and stirred until all dissolved again).
-Rough filtered to remove the undissolved items (stainless springs and pins etc..)
-Suspended a copper bar in the liquid with aluminium wire and the silver started to form quickly, after 30 mins the was an inch of silver sludge in the bottom of the beaker and the solution was whizzing around with fury and silver particles dropping off the copper bar (I assume the warm solution was a faster reaction than my previous cold drop)
-Everything looked good and was going to plan, I went back n hour later to check on it and NO SLUDGE, all the sludge that had formed has returned to the solution, how can this happen, and how do I reverse it? there's still copper in there on the bar. 

Confused

JV


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## butcher (Jun 3, 2012)

My guess, excess nitric still in solution, something as simple as the sunshine warming the solution could redissolve it.


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## Westerngs (Jun 4, 2012)

Butcher is right. Excess nitric acid would quickly redissolve the silver that has cemented since it is a fine powder. An indication of excess nitric is your statement that the "solution was whizzing around with fury and silver particles dropping off the copper bar". This tells me the nitric acid was also dissolving the copper.

Leaving the copper in will eventually use up the excess nitric and then cement out the silver. You will need to wash the silver more than normal to remove the excess copper nitrate.


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## nickvc (Jun 4, 2012)

JV the guys are right you used far too much nitric to dissolve your silver, GSP has done the calculations many times for how much nitric is needed to dissolve values. You would be well served to add your acids in increments with heating to get the most from them and only add more as the reaction stops, over use of oxidisers is the main problem most newbies encounter, in reality your better off having some undissolved values left in your filters which can be added to the next batch.
The thing to remember is that nitric is very often hard to find and tends to be expensive for many members so be sparing with it's use, it will also give you more problems with fumes and with actually precipitating or cementing your values.


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## B1G JV (Jun 4, 2012)

Guys, I appreciate your responses very much, I had assumed it was possibly too much nitric but then thought it couldn't be, I have GSP's books on silver etc.. and also looked through this forum and concluded it was 1.17ml nitric to 1g silver. so for the 1022g of 'metal' I placed in the beaker I only actually added 1 liter of 70% nitric with 1 liter of water, with the assumption that I would be left with approx' 148g of silver, however none remained and only the junk was left in the filter. 

Now I know what happened to the cemented silver it's a relief, so easy enough to recover. However, some questions which I know have been discussed at length:

-Is the 1.17ml nitric based on 70% nitric solution?
-does the water quantity added to solution make a difference? (well the nitric was added to the water)
-does the 1.17ml include all metal weight? (i.e. 1.17ml nitric for 1g sterling, or 1g 50% coin, or should that have been 1.17ml nitric per 1g 'silver content' of the metal, as this may have been my mistake, 1 liter nitric for 1022g 'white metal' with about 900g silver content).

I know now to use less nitric and I will continue to learn and post my results after a few more batches and calculate empirically the quantity of nitric i needed.

Thanks again, JV


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## Geo (Jun 4, 2012)

just as when your making AR, add nitric in increments when dissolving. this helps when your a beginner. when you use a watch glass to cover your reaction, nitric acid is returned to the reaction by condensing on the glass and dripping back into the vessel.start with half the amount you think you will need and let the reaction proceed till all action stops. look to see if material remains, if so add a little more nitric in small increments and let the reaction stop before adding more. this serves two purposes, it conserves materials and lessens the amount of excess nitric in your solution.


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## B1G JV (Jun 4, 2012)

thanks for the tips Geo, I will add slowly in increments on the next batch, for now I've placed a sterling spoon in the solution to use up all the nitric rather than increase the copper content, then I'll cement out the silver with the copper. 

JV


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## Harold_V (Jun 5, 2012)

Westerngs said:


> Butcher is right. Excess nitric acid would quickly redissolve the silver that has cemented since it is a fine powder. An indication of excess nitric is your statement that the "solution was whizzing around with fury and silver particles dropping off the copper bar". This tells me the nitric acid was also dissolving the copper.
> 
> Leaving the copper in will eventually use up the excess nitric and then cement out the silver. You will need to wash the silver more than normal to remove the excess copper nitrate.


Something isn't making a lot of sense. 

On occasion, I used too much nitric and experienced dissolution of copper, accompanied by a generous amount of the familiar brown cloud that comes from the use of nitric. At no time, however, did I ever experience a complete dissolution of the silver (once cemented) when there was copper present, nor would I expect that if there was too much nitric present for all of the silver to be dissolved without considerable activity at the copper. Frankly, nothing is making much sense. I'd suggest adding more copper to see what happens. 

Harold


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## Harold_V (Jun 5, 2012)

B1G JV said:


> Guys, I appreciate your responses very much, I had assumed it was possibly too much nitric but then thought it couldn't be, I have GSP's books on silver etc.. and also looked through this forum and concluded it was 1.17ml nitric to 1g silver. so for the 1022g of 'metal' I placed in the beaker I only actually added 1 liter of 70% nitric with 1 liter of water, with the assumption that I would be left with approx' 148g of silver, however none remained and only the junk was left in the filter.


For years I made the electrolyte for my silver cell by adding a liter of 68% nitric to 30 ounces of silver crystals. All but a trace would be dissolved under heated to boiling conditions. I'm having a hard time coming to terms with the idea that you used too much nitric for the case in hand, considering the alloy would demand a greater amount of nitric. As I said in my other post, something isn't making much sense here. Do keep us informed of what you determine is happening. 

Harold


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## lazersteve (Jun 9, 2012)

For sterling silver and coin silver you will need more nitric acid since copper requires about four times as much nitric as silver does.

If you dissolved the silver under relux or are using a watch glass you can expect the reaction to require less nitric than the calculated amount due to the refluxing NOx and water vapor forming more nitric acid.

Steve


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## B1G JV (Jul 10, 2012)

Hi Guys, 

Apologies for the delay in responding to this, I've had little time what with work and family commitments to spend on my silver refining. 

Harold, I'm also concerned slightly by your comments, I will attempt to put into to words what happened after the last 'incident' after I placed in an additional silver spoon until it stopped dissolving into the solution, I placed a 4" x 1" x 1/2" solid copper bar into the solution, the silver started to cement out straight away and form nicely on the copper, dropping off and reforming. I left the copper in overnight and returned the next morning to find, as expected, a nice amount of silver cement in the bottom. After syphoning, washing and filtering then drying on heat I had 762g of silver cement. This is now waiting with my first batch of 340g silver cement to be melted down before going into a cell. (the first 'batch' I think I must have stopped the cementing process too early to harvest only 340g, I'll come to this next). 

So, after listening to the forum members I seem to have about the right amount of silver cement from that batch. 

Now........ another interesting thing I thought I would mention is what happened with all my waste solutions. I have kept all the solutions I have been working with, i.e. the copper nitrate, I also added the dilute 'washings' from the silver cement wash, which was a nice green/blue solution until it washed clear. So i ended up with a bucket full with about 6 litres of dilute copper nitrate, still with some of my silver in solution. So the other week I decided to just sit a 12" copper bar inside the bucket and leave it for a day. The next day I had the largest grey silver formation on the bar i've ever seen, I left it another week and it grew more. I have since harvested it and have what seems to be more silver cement than is possible, i.e. more than I dissolved. I'm yet to dry it and weigh it so I'll post the finding when I do. At first I thought maybe the copped is cemented out in there too but there's also too much to be the copper and silver. After once week of leaving the copper bar in solution it had reduced to about 1/4 it's original length. So I'm looking forward to drying the cement and weighing it, it was also a very spongy 'growth' I'll have to add some photos when I get a chance. 

JV


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## Harold_V (Jul 11, 2012)

The voluminous silver cement you recovered from the second operation is most likely due to the fact that there was very little silver present, resulting in a dilute solution. It appears that, by now, you had also lowered by a considerable amount, the volume of free nitric acid that had to be present in order for the silver to have been dissolved once again. I fully expect that when you wash and dry the silver that has been recovered that it will not be as much as you expect. For lack of a better description, if is very fluffy, and occupies a much greater space than it will once compressed, or melted. I experienced that very thing on numerous occasions. Please do provide a follow-up on your findings, to disclose if I'm wrong. I hope to not dispense erroneous information. 

A note to consider. It was my experience that the color of such a nitrate solution is a good indicator of its contents. The presence of silver tends to yield a blue/green solution, which shifts to blue as the silver is cemented. However, do not assume that to be the case, for a trace of platinum or palladium can also cause the same coloration. Be certain to test your solution with stannous chloride, as well as a drop sample, using either salt, or HCl, for the presence of silver. 

Harold


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## B1G JV (Jul 31, 2012)

Hi Harold, you're correct about the amount of silver recovered from the large 'spongy' growth. However it had put my mind at ease and I recovered approx' 700g of dried cement from this, all in all I totalled about 1820g of dried cement from the 2 x 1020ish grams of silver I placed in the 2 nitric batches. So from 2040g of sterling and some continental 800 silverware I have 1820g of cemented silver, which means the mix of silver averaged about 0.895 purity. Sounds about right to me (there was very little 800 in there) 

Another note is there was still a LOT of water left in the 'sponge' even after leaving it sitting in the filter/funnel for a few weeks. It dried out on a hotplate in a pan over a period of approx' 1 hour of stirring. 

My solutions were (after cementing): 

1st batch - green / blue and I yielded 340g cemented silver from this

2nd batch - very blue in comparison to the first solution (i had both side by side) and I yielded 760g cemented silver. 

mixture of all remaining solutions - lighter green tint to the blue, yielded about 700g in a huge sponge of a growth.

Now I need to perfect my melting techniques......... and get the silver cell up and running


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## MysticColby (Jul 31, 2012)

I find that my cemented silver, once dried on a hotplate, is a dense powder and easy to spoon into a crucible. I warn you now: I can tell you're going to be shocked by how much silver shrinks when it melts. I've had a liter of cemented silver shrink down to something like 10 5oz bars, which take up about 140 ml. So about 1/7 the volume. (This is of course dependent on the looseness of the silver as it's cementing) It's so dense!


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## B1G JV (Aug 1, 2012)

Hi MysticColby, Yes I realise the reduction from the cement to metallic, I did the melt at the weekend and poured into small 30 to 60g bars (hence my comment to brush up on my melting and pouring skills, they're shocking!) which will then go into the silver cell. 

Cheers
JV


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## Harold_V (Aug 1, 2012)

B1G JV said:


> Another note is there was still a LOT of water left in the 'sponge' even after leaving it sitting in the filter/funnel for a few weeks. It dried out on a hotplate in a pan over a period of approx' 1 hour of stirring.


You may wish to investigate the use of a Buchner funnel. My procedure was to fill mine (using a 24 cm filter) to the rim, then compact the silver, using the butt end of a pestle. Any large diameter piece of material would serve the purpose, however. The volume shrinks noticeably, but the real benefit is the ability to rinse the silver until the rinse water flows clean. You then allow the filter to run until there is no further discharge of effluent. Drying, then, is routine. I'd dump the Buchner in to a large evaporating dish and apply gentle heat. After driving off the remaining water, I heated somewhat longer, raising the temperature above the boiling point of water. Almost without fail, I'd drive off traces of nitric acid, in spite of careful washing. It manifested itself as the familiar brown fumes, so there was no mistaking the reaction. All of this could be accomplished in about a half hour. 

It was my normal procedure to melt my silver in a crucible. The anodes I cast weighed up to 200 ounces, so I'd melt a good amount of silver in a #8 bilge crucible. As it began melting, I'd then add a small amount of borax glass (or anhydrous borax) to the heat, which picked up a fair amount of contamination, plus caused the silver to flow nicely. Once molten, it was then poured to a cone mold, so the resulting slag could be easily separated from the button. Discoloration of the slag clearly indicated that this process was beneficial. While I am not a chemist, my observation indicated that there would be copper oxide in the heat, which colored the slag blue. It's good to eliminate it from the silver, so you get better mileage from the electrolyte. 

Once cleaned, I'd melt the resulting buttons, pouring my anodes. 

I'm not suggesting this is the only way to proceed, but it does offer distinct benefits. 

Harold


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## B1G JV (Aug 1, 2012)

Harold, 
again, many thanks. I considered purchasing a Buchner funnel due to the very slow process of trying to rinse large amounts of 20oz's plus (large for me but not the 200 oz's you were dealing with) so this is still on the cards. I did have copper nitrate left in the cemented silver after weeks of washing, this manifested itself in green 'burnt' deposits in the bottom of the drying pan which were scraped off. (only from the 'spongy batch' the other was ok and clean). 

I take on board the melting tips, I actually use a Flamefast CM350PB crucible furnace, which I'm beginning to think is too big for the tasks at hand. It uses an A10 crucible and I find that after pouring a few anodes to go in the titanium anode basket the silver cools and hardens and I need to reapply the heat, once molten again I repeat, then I end up with a load of BLACK slag looking silver in the bottom of the crucible which wont re-melt, almost like I've burned it!! I must admit I have not used any borax, I do have an amount of anhydrous borax so I should add this to the crucible when it starts to melt.


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## MysticColby (Aug 1, 2012)

harold, I like the idea of compressing the cemented silver. I've noticed before that it does help with transporting into a crucible (pick up a chunk rather than a scoop). I usually compress via vacuum filtration (Buchner funnel), but I bet pressing would produce an even denser pellet.
It amazes me the scale you were working with. 24 cm filter * usually the same in height = 10 L filter? My waste container is the only thing I use that's that big :lol:

BIG JV: you'll always have copper in cemented silver. I hear that at best you can hope for 99.4% pure silver, the rest being copper trapped within particles of silver. That's why electrorefining is necessary if you want 99.9+%
black stuff in crucible... I don't think that's silver. maybe copper oxide? loose graphite from crucible? Silver doesn't oxidize at high temp like other metals. actually, any silver oxide will decompose into oxygen and silver. However, molten silver will dissolve oxygen in it, which is released as it cools (try to have it cool slowly until solid).
borax is highly recommended when melting. It captures metal oxides that would otherwise contaminate / weaken the silver and lubricates the crucible so the silver flows over it like water over wax paper.


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## B1G JV (Aug 2, 2012)

Hi mysticcolby, it's definitely silver, as I placed 32oz of dried cemented silver into the crucible, poured about 25oz's or so, and the remaining black stuff is the rest of the silver. It seemed that with using such a large (A10) crucible for a small amount, each time I poured it would harden and form air pockets and also oxidize somewhat, so I'm left with a kind of honeycomb structure of 'slag' in the crucible. It's not graphite as that would be a minute amount and certainly not 7oz's worth. 
I'll have to try re-melting it and using some borax. I have for now just thrown it in a tub full of 100oz's of recently poured sterling silver shot which will undergo the next nitric treatment, I thought I might just return it to elemental silver, though that would be a waste of Nitric.


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## Harold_V (Aug 3, 2012)

MysticColby said:


> harold, I like the idea of compressing the cemented silver. I've noticed before that it does help with transporting into a crucible (pick up a chunk rather than a scoop). I usually compress via vacuum filtration (Buchner funnel), but I bet pressing would produce an even denser pellet.


I can't recall how much it compresses, but it's definitely worth doing. I'd say it was near a 50% reduction in volume, though. If nothing else, you wring out more water, but, yes, it makes it easier to handle. My problem came in drying, as I knew it would give up traces of nitric, I broke it up in the evaporating dish when drying, to facilitate the process. In the end I had various sizes of chunks. 

For melting, I'd fill a crucible while it was cold, tamp it down with the pestle, then dampen the surface with a wash bottle, to limit losses in the furnace. I found I could fill within about 3/4" of the top (#* bilge crucible) with no problems. The tamping proved to be very useful in that regard. I added flux only after the silver had pretty much fully melted, otherwise you risk combining particles of silver with the slag, a lesson I learned the hard way. I had to rerun a large batch of slag to recover silver that was lost in that fashion. I ran the slag with my waste materials, and got a full recovery, thanks to thinned slag and prolonged heating. 



> It amazes me the scale you were working with. 24 cm filter * usually the same in height = 10 L filter?


I used a Coors ceramic, one piece. It wasn't all that deep. Maybe three inches? It was a very good size (and volume) for the evaporating dish I'd use for drying. A perfect match, really. 

Harold


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