# Silver nitrate question



## mikeinkaty (Mar 1, 2013)

IF one disolves sterling in Nitric Acid to get a super-saturated solution then dropped the temperature of the solution, AgNo3 crystals will form. How pure are those crystals? Say I poured off any residual liquid and stored the crystals. If later I diluted the crystals back into solution and dropped the silver with copper, how pure would the silver be?

Also, I read somewhere on this forum that it was possible to get better than 990 using a copper drop. I had a couple of runs in my last batch that were very clean runs (went the way it was suppose to go) with a very fast and complete drop. I rinsed the cemented mud till the ammonia test showed clear. When I poured those batches to bars for the use in my cells, the bars behaved like they were much better than 990. For one, they formed that crystal pattern on top as have all my electrolysis crystals have when poured into a bar. And the bars seem softer than all my 990 bars poured previously. Just curious. 

Mike


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## nh6886 (Mar 2, 2013)

Mike,

I poured some bars much like you described. I check one with XRF at 99.8% Ag. I have seen some pictures of silver that laserSteve dropped that he said is 999, mine looked almost identical. Both of the above were cemented. I wish I knew the trick to doing it every time, I think for me its attention to detail more than anything else. 

All the best,
John


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## kadriver (Mar 2, 2013)

Mike,

I think it is a function of how you cement the silver with the copper.

When I first started refining silver, I would put a coil of copper wire in the silver nitrate to cement out the silver.

I watched it carefully and when the copper wire started to get thin I would pull it out and put in a fresh coil of copper wire.

By cementing the silver in this way there was very little (if any) copper in my cement silver.

Plus, since the platinum group metals tend to cement out toward the end of the cement action process, there was very little (if any) contamination of the silver with platinum group metals.

The cemented silver was so devoid of copper (due to cementing as described above) that the silver cell electrolyte would turn yellow with no traces of green or blue.

Even Harold made a comment one time at the lack of copper in my cells.

So, yes, you can get very close to three nines with cement silver, but the only way to be certain is by running it through the silver cell.

kadriver


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## kadriver (Mar 2, 2013)

Another possible way would be to dissolve the cemented silver in dilute nitric and convert the resulting silver nitrate to silver chloride.

Most of the copper and other metals would be removed during the first dissolution and cementing with copper.

Wash the silver chloride over and over with hot water, testing the wash water as you go with ammonia to check for copper contamination.

Once the silver chloride is squeaky clean and your certain that there is no dissolved copper, convert the silver chloride to silver oxide with sodium hydroxide.

Then do the classic conversion to pure elemental silver metal with karo syrup or with regular sugar.

If you wash this silver properly to remove all the sugar and left over NaOH, then you will be left with very pure silver metal that looks just like cement silver.

The positive to this is, you don't need an electrolytic silver cell.

The drawback is it creates a lot of waste and each step requires settling time in between rinses, plus it is difficult to get a complete conversion of the silver chloride to silver oxide with NaOH.

kadriver


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## mikeinkaty (Mar 2, 2013)

In my last batch of 66 ozt I started harvesting the cemented mud before the copper was entirely finished. Also, since the sterling was Gorham and similar plates and trays, this first harvested cement was pretty clean. I would let the harvested cement settle out and decant the liquid back into the vessel with the copper. I would then do one boiling water filter and also pour that water back into the vessel. Later rinses went into a different waste jug. All the secondary cement that was produced was held and combined into one bunch and processed later. I poured one 3 ozt bar from the cement and it's physical properties appeared to be identical to those produced from the cell crystals. It even had that crystal pattern on the top.

I'll take this opportunity to report on using my copper buss bar mold. I poured 22 bars (999+) using it. They all came out very nice looking. I held the buss bars together with a 6" Vice Grip clamp. I would soot the cavity very lightly with the torch. I would only heat the copper for maybe 5 seconds with my Oz/Ac torch just before the pour. Afterwards I would lay the mold up side down on a 2 qt pan full of tap water. The bar most usually dropped out within a few seconds or if not then with a few light taps on the side. After the bar was out I would blow out the cavity with my air compressor set at 120 psi. If you don't do this the soot will accumulate and prevent the bars from dropping out and the sides of the bars will not be smooth. The bottom of the bars were flat and the sides were smooth. There usually were some small spurs on the bottom edges of the bars that I would file off. These spurs were caused by the cracks where the copper bars joined. I think these cracks are what released the pressure in the bottom of the mold - hence giving each bar a flat bottom with no cavities. Sooting is important. Without it the bars will cool to fast and not look so good. (the soot acts as a thermal barrier) No bars got stuck in the mold or tried to adhere to the copper. The main thing is to use light soot and don't overheat the mold before the pour.

The thing I like about this mold is I can easily change the position of the end pieces to get different weights and/or thicknesses. These bars I made at 1" x 1.62" x about 1/4" thick (for 3 ozt). 1x1.62 are the dimensions of a "Golden Rectangle". Google it.

Mike


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## SilverNitrate (Mar 4, 2013)

What I would do is after you have had your blue AgNO3 allow those white crystals to form then seperate it possibly by rinsing the white crystal AgNO3 off in a filter. Put that blue liquid in with copper and cement out. to the white crystals put in a 'stoichiometrically abundant' amount of white sugar to it in a pot or something and set a match to it outdoors, allow that to burn. Afterwhich take that silver sponge and your cemented silver chop up in an old kitchen blender with aqueous ammonia then filter that away. Process may sound crude and unusual, but possible to achieve 999 after melting with flux.


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## mikeinkaty (Mar 5, 2013)

SilverNitrate said:


> What I would do is after you have had your blue AgNO3 allow those white crystals to form then seperate it possibly by rinsing the white crystal AgNO3 off in a filter. Put that blue liquid in with copper and cement out. to the white crystals put in a 'stoichiometrically abundant' amount of white sugar to it in a pot or something and set a match to it outdoors, allow that to burn. Afterwhich take that silver sponge and your cemented silver chop up in an old kitchen blender with aqueous ammonia then filter that away. Process may sound crude and unusual, but possible to achieve 999 after melting with flux.



I had one sterling/nitric disolve reaction that was pretty strong and it overflowed my jar into the plastic storage container. Probably not more than a 1/2+ cup of liquid. Several days later I revisited that container and silver nitrate crystals had formed in the bottom. I was suprised at how many crystals formed with that little liquid. I got a spoon, collected them, did a disolve and filter, and added the liquid to one of my cells. That got me to thinking about AgNo3 crystals. I have had other jars that were half crystals the next morning that had been left outside for the disolve.

Anyway, I was wondering if that would be a good way to store silver till one got around to doing the drop and melt. Storing like for months maybe. I may just make a super saturated solution someday then store in in the small fridge in my shop. After all the crystals have formed that will, then decant the remaining liquid and see how much silver I can recover from just the crystals. That would be an interesting project. That would give me the wt ratio of AgNo3 crystals to silver. One question - could the crystals when forming put enough pressure inside the jar to make it crack? I could use a SS container I guess. Once the wt ratio was known then one could use the crystals to replentish their cells. Like I said somewhere else, just curious. May not be anything practical here.

Mike


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## FrugalRefiner (Mar 6, 2013)

Mike,

The weight ratio is easy to determine by looking at a Periodic Table.

To calculate the molecular weight of AgNO3, you just have to add up the atomic weights of each of the components. Each molecule of AgNO3 consists of 1 atom of Silver, 1 atom of Nitrogen, and 3 atoms of Oxygen.

Atomic weights:
Ag 107.87
N 14.007
O 15.999

So 1 mole of AgNO3 will include 107.87 grams of Silver, 14.007 grams of Nitrogen, and 47.997 grams of Oxygen (15.999 * 3). The total weight is 169.874 grams per mole.

The ratio of Silver weight in AgNO3 is 107.87 divided by 169.874, which equals 63.50%. So in every 100 grams of AgNO3 there are 63.50 grams of Silver. Hope that helps.

I love chemistry!

Dave


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## SilverNitrate (Mar 6, 2013)

silvernitrate crystals won't crack a glass container 
Quick knowledge: water ice can crack the glass if formed because the liquid expands in volume to form a solid, thus why ice floats on water, silver nitrate forms from a aqueous solution then those solid crystal are denser than the liquid thus volume shrink and falls to the bottom. Yes silver nitrate is about 63% silver. 
There are tons of ways of getting the silver metal from the nitrate, but burning with sugar is the fastest and more direct. Sometimes its Best to go from a aqueous straight to the metal, which is better than to go from aqueous to precip to metal, or aqueous to precip to precip to metal.


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## mikeinkaty (Mar 6, 2013)

FrugalRefiner said:


> Mike,
> 
> The weight ratio is easy to determine by looking at a Periodic Table.
> 
> ...



Thanks Dave. I thought it would be something pretty simple. So if I put 1kg of AgNo3 crystals into a cell that would be roughly 635 grams of silver or roughly 20 ozt. Seems like it would be kind of handy to keep crystals around were one using cells a lot. Would save the time of doing a dissolve whenever a replenish was needed. Wouldn't it also keep some copper out if you otherwise had to disolve sterling to get the solution? Mike


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## mikeinkaty (Mar 11, 2013)

How I get better than 990 silver with a copper drop.

1) Start with good Sterling - name brand bowls, cups, serving trays, forks, spoons. No mixed jewelry (to many other metals and solder).
2) Clean and scrub the sterling with Bon-Ami before the nitric disolve, rinse and dry well. Cut it into small pieces and start the nitric disolve using good quality Nitric acid and distilled water.
3) Make sure there is a tad bit of sterling left in the nitric acid disolve after all reaction stops. This will insure all the nitric acid has been expended. You may need to warm up the solution to make sure reaction has stopped.
4) Filter the AgNo3. (I use coffee filters and now save the filters)
5) Dilute the AgNo3 with an equal amount of distilled water. Do the copper drop with thick clean pure copper (make it bright and shiny)
6) When you first see the copper reaction starting to slow down pull out the copper and harvest the cement. Filter this cement and do one boiling water rinse. Put this rinse water back in the dropping bucket and put the copper back in.
7) Rinse and filter this first harvested cement with boiling water until it does not show the presence of copper - use the household ammonia test 
8) Dry, melt using flux, and pour.
9) The last gathered cement probably will not make bars of the higher purity - at least it hasn't for me.

Whenever I do it this way the first batch of cement makes some darn fine looking bars! Also, with the higher purity, a silver cell (if you do go ahead and use electrolysis) will last longer before to much copper accumulates.

I'm saying this way has worked for me. There are other ways to achieve the same or better results that I have never tried (yet).

Mike


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## butcher (Mar 12, 2013)

Thanks mike that was well written and a good tip.


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## mikeinkaty (Mar 12, 2013)

butcher said:


> Thanks mike that was well written and a good tip.



Butcher - Why does the last cement appear to not be as high a quality as the first? What is happening in the reaction to cause this? Is there anything that could be added to the solution to keep the quality high? Is the Ph getting out of whack? Would a few drops of Nitric help? I have a Ph meter and could check I guess (If I remember!). There obvioulsy is more CuNo3 in the solution.

Mike


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## kjt124 (Mar 13, 2013)

I don't know much yet, but from what I understand a bit of Nitric will help - keep the pH around 3, but below 4 to avoid the metal hydroxides from precipitating. Other then that you simply get entrainment issues from the concentration of the copper nitrate in solution along with the smaller possibility of the (now roughed up) surface of the copper allowing small particles to break off and land with your silver cement. I know the pH part had a very noticeable impact on the quality of the dropped silver. I have no real way to check purity other than what it looks like when it melts, but it was night and day difference.

I wonder if washing 'dirty' silver cement with weak HCl would clean up any of the copper and/or metal hydroxides...

PS - I was never very good at giving citations in school and nothing has changed, but this knowledge is gleaned from amesametrita, kadriver, lou, and others.


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## mikeinkaty (Mar 14, 2013)

kjt124 said:


> I don't know much yet, but from what I understand a bit of Nitric will help - keep the pH around 3, but below 4 to avoid the metal hydroxides from precipitating. Other then that you simply get entrainment issues from the concentration of the copper nitrate in solution along with the smaller possibility of the (now roughed up) surface of the copper allowing small particles to break off and land with your silver cement. I know the pH part had a very noticeable impact on the quality of the dropped silver. I have no real way to check purity other than what it looks like when it melts, but it was night and day difference.
> 
> I wonder if washing 'dirty' silver cement with weak HCl would clean up any of the copper and/or metal hydroxides...
> 
> PS - I was never very good at giving citations in school and nothing has changed, but this knowledge is gleaned from amesametrita, kadriver, lou, and others.


I checked the Ph of an unused AgNo3 solution and it was 0.04. I had prepared it for use in my cell. Tonight I check the Ph of a spent solution from a copper drop and the Ph meter read 0.06. Hardly any change at all. This drop made pretty good looking cement of the desired color and consistency and had done it in 4 hrs (12 ozt). That was the time to my first harvest of the cement. So. I don't think Ph is a factor unless you think you have Palladium in the solution. I was told to use KOH in that event to get the Ph up to about 3.0. EDIT - READINGS WERE IN ERROR because of operator ignorance!

Weak HCL would creat AgCl. That could be a mess unless you only added it after the copper drop to get the last little bits of silver out. Of course adding salt or HCL to a new solution is another way to extract the silver. That follows with NAOH and sugar. Supposed to be a better way than a copper drop as far as quality of silver produced. I need to get the numbers for that method and try it.

Mike


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## kjt124 (Mar 14, 2013)

That is interesting that your pH was so low. I've done only a limited number of drops and only the last couple have I paid any attention to pH, but the last 2 I had to add nitric to get the pH down. My source of silver nitrate was actually from reagent crystals of it so that likely had a lot to do with it. When I get some more silver to digest I'll have to take a look at how pH behaves again. Perhaps it is just that even in careful nitric additions when dissolving the silver there will most likely be enough free nitric left over to keep the pH suppressed. I don't believe I've encountered a situation where I would have Pd present, but I have a bit of familiarity of when that might be the case (from browsing the forum, of course). If I run across that contingency I know I will have some studying to do in order to make sure I am not inadvertently losing values.

I am definitely familiar with the AgCl route and it is probably the usual love/hate relationship... I was referring more to the final 20% drop after harvesting and washing. I was curious if the HCl would do anything to sort of polish the cemented silver at all, but I was concerned if the HCl would actually start to react with the finely divided silver. I guess the silver cell is just the next logical step without trying to introduce a shortcut. I've been waiting to have a batch of any sort of volume to mess around with a cell just yet.

As far as the quality goes, the AgCl method (for me, at least) has not gone smoothly. It is very difficult (as others have pointed out) to completely react the Chloride with the NaOH. Of course it is ugly stuff to wash after the Karo as well. I think next time I try the caustic/sugar route I will try to melt the Ag2O directly as I have heard some have excellent results and it seems that it would likely be easier to wash - even though it looks like filtering it may pose some difficulty without a vacuum filter setup and nice fine filter paper. (have a long way to go in terms of equipment...)

Just as a quick aside... I know that some guys have suggested using mild nitric to remove the borax from a gold button/bar. Is there a favorite method to use on silver? Obviously nitric would be a silly idea.

Thanks,
Kevin


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## mikeinkaty (Mar 14, 2013)

kjt124 said:


> Just as a quick aside... I know that some guys have suggested using mild nitric to remove the borax from a gold button/bar. Is there a favorite method to use on silver? Obviously nitric would be a silly idea.
> 
> Thanks,
> Kevin



I went to the local Goodwill store and bought a used Crock Pot for $5. I mix 900 ml of distilled water and 100 ml of Liquid-Fire (98% H2So4). I put the silver bars in and turn the switch to the lowest heat setting and let them soak for a few hours or overnight. Liquid-Fire is availavle at most Ace Hardware stores. After a while you will get where you can pour the bars without getting getting the borax spots on them, most of the time. 

You can also clean dirty silica crucibles this way. Leave it in for 24 hrs then afterwards soak it in distilled water overnight then put it on top your hotplate for a few hours to dry out. Then re-glaze it with borax. Use that crucible a few time before using it to pour your high grade PM's. May take a few pours to get loose grains of silica out.

Mike


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## kjt124 (Mar 14, 2013)

Excellent. Thank you Mike.


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## mikeinkaty (Mar 15, 2013)

kjt124 said:


> Excellent. Thank you Mike.


Those Ph readings were no good. I need to learn how to operate my meter. It takes a long time at first to stablize. Mike


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