# Ag cement – Hmmm – what happened???



## kurt (Jul 2, 2011)

Ok this will be first time posting pics hope it works

Anyway – I got this white crystal sponge like stuff when I went to cement the Ag out of solution from some contact points I was working with

Recently bought 600 lb of contactors (magnetic disconnects, breakers, relays, timers, etc) for $180. One – which I called Big Bertha, was a 1600 amp disconnect that weighed in at 150 lb & had 38 lb copper & 202 grams de - soldered points in it

As with all the points I dissolve I started with 1 ml 52% nitric per gram of points. – Next day – most of points were un-dissolved – acid no longer reacting, but testing positive for Ag – so pulled solution off & set aside to settle.

Decided to try experiment. – Added some more nitric to points & put on hot plate bring nitric to a slow boil for about 3 hr which showed signs of braking points down but not really dissolving them so I stopped the experiment – pulled this acid off & added it to first batch of acid as it also tested positive for Ag.

Took filtered solution & dropped in my copper bar & it started cementing real nice so went to work on other things. – Came back about 45 min. later to check on cementing process to find a very vigorous reaction going on & though it was cementing silver it was also dropping out all this white spongy crystal stuff – So I pulled the copper bar out & stopped the cementing – knocked the 1/4 inch of cement off the bar into a jar & rinsed bar off into the jar & let everything settle over night.

Next day – the jar with the settled cement in it had this black ink like cloud in it hovering just above the cement. So I pulled this off & put in a jar as it is still testing positive for Ag. – Then I pulled the solution off the top of the white spongy crystal like stuff from the original cement jar (as it also still test positive for Ag) & added it to the jar with the ink cloud & now the ink cloud turned to a white spongy stuff that doesn’t really want to settle.

Hmmmmm --- any ideas of what all I got going here??????

Kurt


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## kurt (Jul 2, 2011)

The bottom pic in my first post didn't turn out so good so here is another pic of the stuff I am talking about. The blue color is because it still has solution from the cementing in it (meaning copper) but the spongy crystals are an off white (yellowish)

Kurt


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## micronationcreation (Jul 2, 2011)

If the white spongy stuff dissolves in hot water it may be lead.

Have you checked the part dissolved scrap for cemented silver?


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## kurt (Jul 2, 2011)

No I have not tried hot water mainly because I don't think it is lead - why to much of it & with this coming from a 1600 amp disconnect there would be little if any lead involved - even in the solder as the heat generated from the ark when throwing the switch would melt lead in a heart beat (points not actually soldered on but brazed on) --- And no - there is not any silver cement in the un-dissolved points.

I have had something simular to this happen in other cement batches - but in expermenting with it - it would dissolve along with Ag cement if I put nitric on it & even partly dissolve with room temp water

This stuff does not dissolve with room temp water, - nitric, - or HCL


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## micronationcreation (Jul 2, 2011)

I could be way off, but is it possible that your copper cementing bar is not pure and is contaminated with maybe tin? 

Hopefully a moderator can have a look at this...


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## Sodbuster (Jul 2, 2011)

Kurt :

" most of points were un-dissolved "

Sounds like the centered tungsten points to me. 

" ink like cloud "

That sounds like tungsten also.

Tungsten in solution will give you a dark cobalt blue color. 
Check your points first before going into solution. A centered tungsten point will be brittle and shatter if you tried to clip it in half. Also look for a crosshatch or a waffle like pattern on the back side.

" still testing positive for Ag "

They only have about 30% Ag, no need to dissolve the entire point. Fish them out and see if they crumble. If they do not crumble and remain in a solid chunk they still contain some possible silver and you will want to continue with the dissolution.

Afraid I can't help you with the " white spongy crystal stuff ", or the mug full of cloudy solution. It looks to me like you have allot of things in the mix. 
Are you using tap water in your solutions? That mite explain why so cloudy.

I'm sure the experts in here will shed some light on this. 

Ray


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## butcher (Jul 2, 2011)

I think Sodbuster is right on with his advice,

"looks like a lot of things in the mix"

looks like copper is also cementing from solution, base metals in solution can push it out of solution if acidity is low enough, I would wash well with boiling hot water till no color then redisolve (dilute and filter)and then recrystalize.

contact points can have a lot of different metals involved, several are very valuable, do not disgard without further testing of precipitants and solutions, some metals like tungsten are just trouble makers if not dealt with first. GSP and Harold have given great advive on these subjects, veiwing their posts will help in this project.
are we going to see silver bars in the near future?


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## Oz (Jul 2, 2011)

Now why in the world did you make a mess like this? 

Kidding aside, I do not know what your contaminate/contaminates are. I can tell you what I would do to clean it up though. 

I am starting on the premise that you do not have a salt that formed due to a solubility issue, as your digestions should have cooled as you combined your solutes then filtered them clear. So were your solutions at room temperature after filtering and yet staying translucent?

If so, then all of your solids from cementing on copper should be elemental metals. You mentioned that this stuff does not dissolve in room temperature water, nitric, or HCl. So it is probably something that just does not “readily” go into nitric, since it obviously did once when you were digesting the contacts.

I would filter everything you have from this very carefully, even letting it rest for 24 hours to be sure no solids will form. Then treat this filtrate with HCl to remove any silver you may have remaining in solution as silver chloride. There are only 3 metals that will dissolve in nitric but form a chloride when HCl is added, silver, lead, and mercury. Of those 3 only one of those chlorides will go into solution with ammonium hydroxide, and that is your silver chloride. 

So after removing everything from your nitric that will form a chloride, wash it well and remove a tablespoon sample or so and place it in a beaker and cover it with 10% or stronger ammonium hydroxide. Agitate it from time to time over a half hour. Decant off the solution and add HCl to it until no more silver chloride is produced. Keep repeating this step on your tablespoon sample until it is either all consumed by the ammonium hydroxide washes or the washes no longer produce silver chloride when HCl is added. If everything from your tablespoon sample is digested by ammonium hydroxide, it is safe to assume all you have is silver chloride and no mercury or lead. If not, then you will need to do this on your entire mixed chloride batch to remove your silver.

Back to the solids you still have from your cementation. I would digest them in very hot 50/50 nitric until nothing else is digested, let cool, filter, and set for 24 hours as before. Repeat the same procedure. I would also check the solids that are remaining after this digestion with some ammonium hydroxide to be sure there is no silver chloride in it just in case you had somehow accidently introduced a chloride. You will now be the proud owner of a pile of silver chloride. Not fun to reduce, but you will have all of your silver without contaminates.

Please note! Never leave ammonia hydroxide with silver in it setting around, always acidify it with HCl before you stop working with it.


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## goldsilverpro (Jul 2, 2011)

I would tend to agree with Ray and butcher. Sounds like and looks like tungsten to me. I would use more dilute nitric with heat.


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## Oz (Jul 2, 2011)

Chris,

I would agree that he likely has a tungsten problem in his original digestion. However having something other than silver cementing on copper from his filtrate is what I was looking at. I was rather certain that tungsten would not cement on copper in nitric. Does anyone know differently?


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## metatp (Jul 2, 2011)

Oz said:


> Chris,
> 
> I would agree that he likely has a tungsten problem in his original digestion. However having something other than silver cementing on copper from his filtrate is what I was looking at. I was rather certain that tungsten would not cement on copper in nitric. Does anyone know differently?


I don't think tungsten would cement, but something drags down when tungsten is present. When I add a little HCL to the cemented silver (usually a darker gray), the cemented silver lightens up and a dark blue solution forms. I then rinse with warm water until the solution is clear.


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## Oz (Jul 2, 2011)

Be aware that high end and high voltage silver contacts sometimes contain Pd and Pt. They will go into nitric with the silver and cement out of solution on copper, giving you a darker cement silver.


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## kurt (Jul 2, 2011)

Thanks guys

No silver bars yet – need to come up with a mold (it’s on the things to do SOON list) so just been pouring it off into water for now – there’s about 31 oz in the can

Tungsten is kinda what I figured on some of these points that have cross hatch pattern on the back & don’t dissolve. I’ve been dumping these into a jar to play with later. Need to come up with a way to crush or pulverize them so the acid can work more readily on them as I think they still contain Ag & maybe Pt or Pd

As far as Pt & Pd goes – I am getting some solutions that are showing slight indications of both these but so far have not recovered any. --- I will be asking some questions about that in the near future

Oz – thanks for the info – I will put your advice to work sometime this next week when I am done with a couple other solution I have going

Kurt


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## kurt (Jul 3, 2011)

I never use tap water because I live out in the country on 40 acres with a well & the well water has a heavy iron bacteria problem (common problem in this area) so have to use clorine tablets in the well to kill the iron bac. I run the water threw a filter in the house to remove most the clorine for drinking water but it doesn't get it all - so to avoid grabing the wrong water jug in the lab & getting clorine were I don't wont it (had that happen a couple times) I just don't use it in the lab

Kurt


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## Harold_V (Jul 3, 2011)

Oz said:


> Be aware that high end and high voltage silver contacts sometimes contain Pd and Pt. They will go into nitric with the silver and cement out of solution on copper, giving you a darker cement silver.


True, but the presence of either will shift the color of the solution to green. I see on signs of that in the posted picture---and I'm convinced the problem is nothing more than what is expected of dissolving high amperage contacts---which are typically tungsten. 

Sodbuster gave some excellent advice------way to go, Ray!

My procedure for handling tungsten contacts, of which I ran many---was to literally boil them in dilute nitric. It takes hours for a complete silver extraction---and some of the tungsten ends up in solution, eventually yielding that funny pale yellow material that may be confused with silver chloride. It's easy to tell when all of the silver has been leached from tungsten contacts. They break very easily. If, when they break, you find a dark strip inside, all of the silver has not been removed. 

I never filtered such solutions. No need, really. They were allowed to settle (doesn't take long when you're heating the solutions) after adding cold tap water (I wasn't concerned about the traces of silver chloride, which always ended up in my waste material to be recovered later by furnace). Once settled, the solution was poured off to a plastic bucket where silver was cemented on copper. Don't worry about the traces of tungsten that follow the operation. It will be removed when the cement silver is melted, assuming one fluxes, as they should. I should note that I did filter the very last of the material, when it was down to almost nothing but solids. That extracted the silver nitrate that was still present. 

Harold


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## Harold_V (Jul 3, 2011)

kurt said:


> I’ve been dumping these into a jar to play with later. Need to come up with a way to crush or pulverize them so the acid can work more readily on them as I think they still contain Ag & maybe Pt or Pd


It is doubtful you'll find either Pt or Pd mixed in tungsten contacts. I ran them for years and never once found any. (I was on very good terms with stannous chloride, unlike many of the readers here). 

Do read what I had to say about processing tungsten contacts. They require no crushing, and I advise you not try. All that will do is complicate the recovery process. 

Harold


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## kurt (Jul 4, 2011)

Thanks Harold for the advice - I will most certainly use it - my thought was that crushing them would help with the parting of the Ag from the tungsten but now that you mention it I can see how it could end in a mess

Kurt


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