Looking for pointers on how I attempted silver refining

[MacMasterMike]

Perhaps this belongs in the silver forum but this place gets more traffic. Attepted to do so some silver refining today using some metal i got my hands on. Its a copper silver mix with about it being 20% or so silver. I would of maybe been better to build a cell for this but I wanted to attempt the project this way. Have a 2L flask there and only had so much time to work with today. Started off adding 50/50 nitric at first as that didnt react so strongly. Then started adding the nitric at the full strength. Got a little warm but made sure the water was iced well. Added close to 750ml of acid total. It was slow going as there is alot of metal there. Also what was very slow going was trying to filter the stuff. Either lots of non disolved things in there due to me not cleaning it well enough or something. Also does the green color mean just a high copper content as I only ever seen it blue and didnt get that green color until i was done with adding acid. First time I only experimented with a few grams of dust. I'll be going in again monday to hopefully disolve as much as I can. I also tossed in some gold plated and 10k to the metal when i was melting it down for shot so there is some gold in there. When I build my own hood in my work shop I think this would be a great hobby to have as its something you need to take its time. Cant set it and forget it but certainly something else could be done while you wait for the acid to disolve the metal.

The setup

A nice little number of the reaction

The green

How I had to leave it.

Was wondering what was gumming up my filters so fast and if there was a faster way to get around it? Perhaps I'll have to wait till everything is disolved to solve that problem. Remaining optimistic that on monday I can get the rest of that disolved hopefully though I have a feeling it wont. Its all shot but still alot wieghing in at 6 or so pounds. Thanks for checking this out and any comments you may have. Hope this helps to give other begineers like me an idea of the process and how time consuming it is. Check back in a few days to see how I progress.

 

[darkelf2x1]

to speed it up you might want to consider a vacuum filter

or

just use a multiple series of filtering set ups

 

[AgAuPtRh]

Looks like you have quite a lot of metal in there Mike? How many ounces? How large are the pieces?

Did you dilute the solution before filtering?

Something I read a while back that helped me -- nitric acid can toughen up your filter -- preventing it from operating like you expect. I looked for the reference in Hokes book because that's where I read it. Can find it. She discussed thinning your chemicals before filtering.

I'd say you had way too much metal in the flask and very large pieces at that.

Steve K

 

[MacMasterMike]

yeah it looks like that because it the stuff I added last. Other wise its all tiny bee-bees of shot. As for filtration the watering down is a good idea I didnt think or read of that before. I do have a vac pump running on it and when first added to the bunchner funnel it flows fine but soon clogs up the paper with stuff that is caught. Like i said its about 6 pounds of metal.

 

[lazersteve]

Mike,

If the metal had tin in it then it's possible that the filter is clogging due to tin nitrate, a white waxy, gel like material.

Just a thought,

Steve

 

[goldsilverpro]

I agree with Steve. It sure sounds like tin. Sounds like you're doing silver solder. Actually, the slimy tin compound that's produced is called metastannic acid (acid tin oxide). If you had silver solder, you probably didn't need to shot it. The silver solder I've worked was in thin strips. You probably had more surface are before you shotted. Just cut it in pieces.

I never paid much attention but, I've read a few times that, when there is free nitric in the copper solution, the solution is blue. When there is no free acid, the color is green. To me, the green color indicates there is no nitric left in the solution and, therefore, there is probably some undissolved silver in the slime.

I would dilute the main silver solution 1 to 1 with distilled water, filter, and drop the silver with copper buss bar. The filtering is easier if you let it settle then pour, dip, or siphon off the top clear solution and filter it first. When it's finished, filter the bottoms.

You shouldn't have put any gold in with the silver. Now you have to pay the piper. Now it's mixed up with the metastannic acid and, it sounds like, some undissolved silver. Metastannic acid won't dissolve in any acid so, you'll have to dissolve the silver and gold, instead. There's a possibility it will dissolve in hot sodium hydroxide but, it's a waste of time since you'll still have to go though the procedures below in order to separate the silver and gold.

Here's how I would do it.

(1) Silver.

After filtering the slime, put it into a very small amount of 50/50 nitric, diluted with distilled water. Heat it until no more reaction. Add a little more if you need it. This dissolves the silver. Try to filter and rinse it as well as you can. Add the solution and rinses to the main silver solution.

(2) Gold.

a) Put the filtered slime, filter paper and all, into a heatable glass container. The paper will pulp up and will help in filtering (you can buy paper pulp filtering aids).

b) Barely cover with hydrochloric or muriatic acid (both are HCl) and heat until it is a little steamy.

c) Add the nitric acid, dropwise, until there is no more fizzing with an addition. Add the nitric in spurts, a few drops at a time, and allow each spurt to quit reacting before adding the next spurt. Stir before adding the next spurt.

d) Add a shot of HCl. If there is no reaction, you are finished.

e) If there is fizzing, do the nitric again.

f) Repeat until there is no fizzing with either acid. Sometimes, the acid additions will have to heat up a few seconds before the fizzing starts.

g) Dilute 3 times with tap water, filter and rinse well, and drop the gold with sodium metabisulfite.

If you did steps (c) thru (f) right, and kept out excess nitric, you won't need any urea.

Note on Glassware.

Just because something is Pyrex, it doesn't mean that you can use direct heat on it. I notice you are using a vacuum filtering flask on the hot plate. These are made too thick and uneven (wall thickness) for direct heating. They will exhibit thermal shock and break. It might not break today but it's going to break sometime. You need Pyrex (or, Kimax) containers designed for direct heating. These are coffee pots, beakers, erlenmeyer flasks, and other lab containers. Don't use Pyrex things like measuring cups, vacuum filtering flasks, or battery jars to heat with.

You can also use Corning Ware containers to dissolve in with a lot of direct heat. You can use either the white, flat-bottomed type or the amber, see-through ones.

 

[MacMasterMike]

I didnt notice any clear slime on any of the filter papers. I should of taken a picture of it but there was lots of black particles still floating around, which i think is some sort of dirt i had on these little watch links. The majority in there was a copper and silver mix from sterling silver ware. the only other things I tossed in there just for curiosity were those watch links 2 or 3 watch bezels, a sterling silver bracelet, and a silver plate spoon for the heck of it. Everything else was shot of that 6 or so pounds i had of that 'bronze'. Was no solder involved that i knew of. Thanks for the points on my filter flask. I figured the filter flask was the wrong thing to do this in. I wasnt using direct heat I was just using that thing as a base for what ever reason. Had to cool it off with water and ice otherwise it would of been even slower going. I have an erlenmyer but only in the 4L variety and couldnt bring it with me. I will however bring some spare white corning ware dishes with to perhaps move this along on monday.

 

[goldsilverpro]

Many bronzes have tin in them.

The more I look at your photos, the more curious I am. You started with 6#? Do you mean 6 ounces? Why do you only have 1 liter of solution? How much acid and metal did you start with? With 20% silver and the rest of copper, etc., it would take 2.6 gallons (plus, 2.6 gallons of distilled water) of nitric to dissolve 6# of this metal. One gallon of nitric dissolves 7# of silver or 2# of copper. These figures are pretty reliable.

If you only had one liter (1/4 gallon) of acid and tried to squeeze 6# into it, the crystals are what are clogging your filter. You would also have tons of undissolved copper. If you started with even 2 gallons of nitric, you would have the same problem but it wouldn't be as bad. The crystals are copper nitrate and silver nitrate. Heat it up in a hot tap water bath and add some distilled water. Stir it. Get the crystals dissolved, allow it to settle, and carefully pour off the solution and filter it. Look at the solid material and probe it a bit. If its solid, you need more nitric. If you have gold and silver in it, you will have to go through the process I outlined in my last post.

Here's the way I would have dissolved 6# of 20Ag/80Cu.

(1) Calculate the nitric acid needed. It came out to 2.6 gallons. This is approximate - maybe, a little short. You also need 2.6 gallons of distilled water.
(2) Divide the shot or the pieces, as-is, evenly (weigh it) among 3, 5 gallon plastic buckets. Put each bucket in a plastic tray, in case of foamover.
(3) Cover the material, in each bucket, with distilled water. Add an extra inch.
(4) Start adding the nitric. Add about 300mL - 500 mL of nitric to each bucket. It should start working quickly. It will start getting hot. When it settles down, give in a good slow stir and add another shot of nitric. Repeat until a small addition gives no reaction. You may have to add a little water now and then to keep it from crystallizing. Don't add too much or you'll cool it off. Don't cool it. Let it get hot. This whole thing will take about an hour.
(5) Add the required amount of distilled water. You will end up with about 1.7 gallons of solution in each bucket.
(6) Let it cool and settle overnight. Pour, dip, or siphon the solution off of the solids. Filter the solution first and then the solids. If you have a little metal left over, you can dissolve it in a little nitric and water or save it for next time.

I see your 5 pint bottle of reagent grade nitric sitting there. It would take 4 bottles to dissolve the 6# of metal. That's about $150 - $200 worth of reagent grade nitric. If you're going to use nitric in this quantity, you've got to find a source for technical grade. In 1 gallon containers, tech. grade would cost $30 to do this job. In 55 gallon containers, it would cost $6.50. Of course, they want a $750 deposit on the 55 gal. stainless drum.

 

[MacMasterMike]

Yeah having gone back again today I can certainly say I got ahead of myself here. Yeah that bottle of nitric all said and done after fees and taxes was 30$. You sure know your stuff. What got me today when I went back was I could get very little silver to precipitate from what I had. I'll explain what I ran into and tried to do. Firstly though the reason I went hog wild was I got great result from earlier runs but was using small amounts and it was granular.

Here I started off where I left off. Just tested for the heck of it if anything precipitated after clearning it up with hot water and a spalsh of nitric. Adding the water took a bit for it to clear up and even then it seemed to still have a precipitate. After that I added the nitric and like i said it cleared up.

What it looked like after adding some salt. like the other times Ive done this it was instant. However unlike other times all it did was change color like this. No clumpy silver cloride to speak of.

So after that I continued to spend the rest of my acid that I have. This time around I use two containers. Its not heated just sits up on the hot pad.

While the acid does its thing I try to filter some stuff from last time. Once again it clogs up even with suction. Here are pictures of filters from last time(first) and this time around.

So after all that I was spent on acid and had to check what i had for silver. Poured some out and tried to filter. Once again slow going even with the vac. This is different from the first test I did. Cleared up a small portion with water and nitric splash treatment and went to precipitate. I got nothing out of it. That was pretty wild as I would have not guessed there was no dissolved silver in there after all that acid. Only got the white milky precip twice out of the 5 times I did it from different samples of acid. The final go even from adding today acid resulted in no precip even after the treatment of clearing it up.

Now what of that silver? The other runs Ive done this I was using the same material but it was granular and I knew I had it all disolved when I attempted anything. So i know there is silver in the metal. This slime im getting is that just metal that isnt quite disolved yet?

Here is that precip I was talking about that was floating around.

I was somewhat discouraged after all this effort but still looking for ways to proceed. Since I will most likely avoid the chemical way I plan to build a cell. The material was sort of setup to do that to begin with but oh well. Reading up on cells in Ammens book and knowing a thing or two about cells from building a anodizing tank I could just use a pointer on what to make the electrolyte from for copper refining and collecting the sludge. Whats good for a sludge bag from homemade materials? Also that "waste" I'll call it I have there is there a way for testing it for silver other than what Ive tried? Clearing it up and adding salt didnt precip anything So i think its safe to assume its silver free? Thanks all onces again and hopfully someone out there can find this useful. Ive read a few texts on all this already to avoid "reinventing the wheel" like Harold and GSP always advise. Just a begineers mistake this time around.

 

[aflacglobal]

GSP,

Do tell me , if i we looking for a very large source of nitric in 55 gallon drums. Where would one look.

Ralph

 

[goldsilverpro]

Ralph,

Just look under chemicals in a city's yellow pages. The 55 gallon drums used for nitric must be stainless and requires about a $750 deposit.

MacMasterMike,

The standard acid copper plating solution runs about 28 ounces/gallon of copper sulfate and 7-8 oz/gal, by weight, of sulfuric acid. Pure copper is used as the anode and the parts to be plated are the cathode.

The formulas for most all plating systems are critical. When the ingredients get out of whack or, when impurities build up in the solution, the deposit at the cathode greatly suffers. With only a small amount of nickel, zinc, iron, etc., dissolving from the impure anode, the cathode deposit will be spongy and non-adherent. The plated copper will break loose and float (looks like floating turds) and will short out the electrodes. This makes the supposed copper cell worthless.

 

[aflacglobal]

Thanks, I figured that just didn't want to look to stupid.
I was looking at an on site storage system. Tank and containment field, all the good EPA crap. But they tell me i can store it in approved shipping containers. So i figure save the trouble and expense and just leave it that way. What's the best method of handling it or transferring it from drum to vessel.

Thanks,

Ralph

 

[goldsilverpro]

Ralph,

Here's a post I made on transferring nitric to 1 gallon jugs.
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=240

The simpliest way is to buy a special stainless "drum faucet" which fits in one of the two threaded openings on top of the drum. Use teflon tape on the threads. Get a "drum cradle". This is a dolly that allows the drum to sit horizontal.
http://www.bascousa.com/store/index.aspx?DEPARTMENT_ID=29

You can probably buy the faucet and cradle from the chemical supplier.

When using the faucet, crack open the other opening a bit to allow air in, so the acid won't gurgle as it comes out.

They also make stainless hand operated pumps that screw into the bung and are used with the drum upright.

 

[aflacglobal]

 

[goldsilverpro]

Are these coatings painted on or chopped on with a gun? I sure like the chopped on coatings.

There are also plastic containers available, for spills, that the drum cradles sit in. They hold 66 to 75 gallons - just in case. Check the bottom of the drum cradle link. This one also acts as a cradle.
http://www.bascousa.com/store/item.aspx?DEPARTMENT_ID=29&ITEM_ID=936

The link also has SS faucets, somewhere.

 

[aflacglobal]

 

[aflacglobal]