Starting a new batch

[Gwar]

Hello everyone ! I am going to be starting a new batch, I plan on using about 140 Roosvelt pre 64' dimes, so that will yield about 10ozt, I am going to utilize my usual coffee pot, pan and hotplate with the exhaust hood, I will chronical all the steps here as I proceed for comments, my main question is how many ml of Nitric acid and Distilled water should I use to start with?

 

[Martijn]

A new batch.

Leaving the 'value difference of recognizable coins vs unidentified metal bar' discussion alone, how much did you use (write down) for your last batch?

...ml per gram of ...% Ag (92.5%?) used at ...degrees C in additions of....ml each time, starting with ...ml.

I would advise: start with 1ml per gram of Ag. And add slowly under heat at 60 to 80 degrees C, keeping brown fumes to a minimum. Keep track of what you're doing for future 'lessons learned' sessions.

In some counties it's a crime to destroy coins or paper money. You could get a big fine.

Martijn.

 

[Gwar]

Many thanks for the response Martijn, I did have some notes, but I believed I was using way too much of each, I am going to start a journal / spreadsheet of progress and pitfalls once I start this batch, again, Thanks !

 

[AMS-Pro]

Hey Gwar, did you get that new piece of equipment in yet?
Are you using 70% Nitric, or is diluted 50/50 with distilled water? You should use a 50/50 diluted mixture.

When dissolving silver into nitric, you don't want to dissolve everything. It is a good idea to have a little bit of your silver left at the bottom of your container so you know you do not have too much nitric acid. Use low to medium heat when making your mixture.

It takes 1.22 ml. of 70% Nitric to dissolve 1 gram of silver.
It takes 4.3 ml. of 70% Nitric to dissolve 1 gram of copper.

Start with these figures to dissolve your silver into Nitric and create Silver Nitrate.

For 1 gram of Sterling silver - 92.5/7.5, Ag/Cu:
(1.22 x .925) + (4.3 x .075) = 1.45 ml of 70% nitric or 2.9 ml of 50/50 nitric

For 1 gram of Coin silver - 90/10, Ag/Cu:
(1.22 x .90) + (4.3 x .10) = 1.53 ml of 70% nitric or 3.06 ml of 50/50 nitric

Once dissolved, with a little bit of material still left at the bottom, let cool, then filter out any solids.

Once filtered, dilute further with distilled water to get an electrolyte solution with a silver ratio of 150 grams/liter. Start with this ratio as your base line, and make adjustments as needed for your setup over time.

Edit* To reinforce what Martijn said. Have necessary PPE on to keep your body safe. When dissolving silver into the the acid, make sure it is under your fume hood, and fume hood is on. Add your acid mixture slowly to keep the fumes created to a minimum, there is no need to rush this process.. It is safe practice to do it this way, every time.

 

[Gwar]

Many thanks for the reply AMS-Pro, I will use the computations you have provided, as for the equipment it did arrive, I am going to be making a new Anode tonight or tomorrow and plan on crafting a better basket and using a bigger glass bowl to monitor growth, the Nitric I purchased from DUDA Energy LLC is high quality IMO, it was a fair price and shipped rather fast, and of course I use PPE and faithfully !!

 

[AMS-Pro]

Many thanks for the reply AMS-Pro, I will use the computations you have provided, as for the equipment it did arrive, I am going to be making a new Anode tonight or tomorrow and plan on crafting a better basket and using a bigger glass bowl to monitor growth, the Nitric I purchased from DUDA Energy LLC is high quality IMO, it was a fair price and shipped rather fast, and of course I use PPE and faithfully !!

You're welcome, and the computations should be an excellent base line for you to start at. Wonderful on the equipment, let the fine tuning begin. A new anode, and better basket are excellent goals, I'll be rooting for your success. Being able to watch the growth in real time is always beneficial, and exciting. The nitric will do well for you, remember not too use too much, only barely what you need to dissolve. As far as the PPE goes, I'm loving the gear, it looks like you're ready for the apocalypse.

 

[Gwar]

Safety First !

 

[Gwar]

I think part of the problem is I always rush things, I need to take my time and do it right..

 

[AMS-Pro]

I think part of the problem is I always rush things, I need to take my time and do it right..

Yes sir. Take your time, and do it right. Safer, better numbers, more accuracy, and better results.

 

[cejohnsonsr1]

Don’t forget to incinerate before you start. Removing as much grease, oils, dirt,etc… will make the rest of the process go better. You can figure roughly 2ml of Nitric per gr as a starting point. If you carefully weigh after incineration and keep track of how much Nitric you use, you’ll have a very precise record as a reference for future batches. As mentioned previously, don’t let it get too hot, add Nitric slowly in small increments and let it be completely consumed before adding more and, finally, stop before all the metal is dissolved. By my rough calculations you should have about 10.8 ozt raw weight, so you should be able to yield 10 ozt and leave enough to make sure all the Nitric is consumed. Good luck!

 

[Gwar]

cejohnsonsr1, Thanks for the tip, I have a small mixture of Muriatic acid and water I use in conjunction with a glass bowl and the hotplate to kind of boil the coins, it seems to clean them very well..

 

[jobinyt]

Gwar - I'm curious. Why do you use old silver coins as raw material from which to extract silver? The reason I ask is that my experience is that such coins sell at a premium to their intrinsic value' It seems, after your expenditure of time and process material, you end up with something worth less than you started with, so the net loss in value is significant.

 

[ludlow6]

A new batch.

Leaving the 'value difference of recognizable coins vs unidentified metal bar' discussion alone, how much did you use (write down) for your last batch?

...ml per gram of ...% Ag (92.5%?) used at ...degrees C in additions of....ml each time, starting with ...ml.

I would advise: start with 1ml per gram of Ag. And add slowly under heat at 60 to 80 degrees C, keeping brown fumes to a minimum. Keep track of what you're doing for future 'lessons learned' sessions.

In some counties it's a crime to destroy coins or paper money. You could get a big fine.

Martijn.

Its a crime our cents are made of zinc.

 

[orvi]

Many thanks for the reply AMS-Pro, I will use the computations you have provided, as for the equipment it did arrive, I am going to be making a new Anode tonight or tomorrow and plan on crafting a better basket and using a bigger glass bowl to monitor growth, the Nitric I purchased from DUDA Energy LLC is high quality IMO, it was a fair price and shipped rather fast, and of course I use PPE and faithfully !!

Nice gear. Respirator is fine to have, but be careful and do not rely on it too much - it has most of the times limited "capacity" for fumes we create in refining process.

Given numbers ( eg x mL of nitric for y grams of silver) should only give you perspective of how much you will probably need based on the equation we assume. But there are more pathways how silver can dissolve to the solution. Not only NO2 is evolved, but also NO (deeper reduction of nitric acid=less nitric used per gram of silver). Some of NO2 could reform nitric acid in solution, producing NO. Which in turn could react with oxygen from the air to reform NO2... etc

Always start with small doses of acid and add it in small increments. Observe the reaction. Heat the solution and observe if NOx gases arise from it. Continue with small doses until just a tiny bit of material is left in the beaker and no more fumes are formed. This assure you that reaction is complete and no excess nitric is present.

Also you can do it like this. Add 1/3 - 1/2 of calculated acid to the material. Let it react properly till no more NOx fumes are evolving. This tell you acid is spent. Decant the pregnant solution to another beaker and add another portion of fresh acid (obviously much smaller than previous one) to the solid residue which is left in the beaker. Repeat this sequence till you consume the material.

If you add few mL of nitric acid to say 0,5 L of silver solution, final strength of the acid will be very low = and this result in slow reaction of the metal. If you decant pregnant solution and add fresh 35% nitric, reaction will be much quicker and you will save some time.

Just go slowly and try not to overshoot

Good luck with refining

 

[AMS-Pro]

Without getting into a debate over the legal aspect of using coins, and just focusing on the monetary value of coins in the process.

so the net loss in value is significant

Unless it's some kind of coinage that is extremely rare, and extremely valuable.

This is debatable depending on the viewpoint. For the immediate future, there may be a loss monetarily wise, however, the value in knowledge of the process, and skills that get perfected to perform that process, will eventually outweigh the monetary loss. The moment he can prove a reliable process, with a spreadsheet, and hard data, is the moment he has the ability to provide a specialized service for a fee. A specialized service, which over time will net him more monetarily then anything he initially lost.

 

[AMS-Pro]

Given numbers ( eg x mL of nitric for y grams of silver) should only give you perspective of how much you will probably need based on the equation we assume.

I concur with this, with the variables in play, it is next to impossible, or entirely impossible to ever provide an exact number. The best that can be done is to give a base line, within a working range, that can be easily adjusted for the task at hand.

Always start with small doses of acid and add it in small increments. Observe the reaction. Heat the solution and observe if NOx gases arise from it. Continue with small doses until just a tiny bit of material is left in the beaker and no more fumes are formed. This assure you that reaction is complete and no excess nitric is present.

This is a must, and a great way to perform the process. Thank you for clarifying with a more detailed description to the OP.

Also you can do it like this. Add 1/3 - 1/2 of calculated acid to the material. Let it react properly till no more NOx fumes are evolving. This tell you acid is spent. Decant the pregnant solution to another beaker and add another portion of fresh acid (obviously much smaller than previous one) to the solid residue which is left in the beaker. Repeat this sequence till you consume the material.

If you add few mL of nitric acid to say 0,5 L of silver solution, final strength of the acid will be very low = and this result in slow reaction of the metal. If you decant pregnant solution and add fresh 35% nitric, reaction will be much quicker and you will save some time.

This is definitely a more advanced, faster way to do this process. I'm a fan of this method, just have to be careful, and not overshoot with the material you have available.

 

[orvi]

This is definitely a more advanced, faster way to do this process. I'm a fan of this method, just have to be careful, and not overshoot with the material you have available.

If you do it like this, you can hardly overshoot with first two additions. If it happen at next ones, bulk of silver is already properly dissolved - so you can save it for the next batch, precipitate with AgCl...
In the end, it does not interfere with your next steps very much. On the other hand, if you overshoot in the bulk solution (happen time to time to everyone ), you must deal with it in bulk = in very diluted conditions. This make spending the excess acid with more silver or copper more time consuming.

Using this method could be of great advantage if you need to shorten your processing time on batch. Anyway, there are plentiful methods how to do it, and not just one is the "right" one

 

[AMS-Pro]

If you do it like this, you can hardly overshoot with first two additions. If it happen at next ones, bulk of silver is already properly dissolved - so you can save it for the next batch, precipitate with AgCl...
In the end, it does not interfere with your next steps very much. On the other hand, if you overshoot in the bulk solution (happen time to time to everyone ), you must deal with it in bulk = in very diluted conditions. This make spending the excess acid with more silver or copper more time consuming.

Using this method could be of great advantage if you need to shorten your processing time on batch. Anyway, there are plentiful methods how to do it, and not just one is the "right" one

Exactly right, the overshoot would be on the last stage usually. When at the stage where your material to dissolve is low, I would say go back to adding a splash of nitric in the already pregnant solution until your material is almost nil.

As far as methods go, I personally like a modified version of this concept. I favor the flow system with a leach tank kind of setup.

 

[Gwar]

Great thread ! I had the opportunity to buy 208 Canadian dimes for the price of melt, I consider that very generous from my silver/coin shop, there are two date sets, 50% silver and 80%, I chose the latter and all are 80% or around 12.45 ounces of silver hopefully, but most likely a bit less will be gleaned, time to clean them up a bit..

 

[Zhazham]

In Europe, we have a lot of national coins from era before euro. Those coins can't be exchanged to euros anymore. Some are 0.300 silver and some have even more silver. These coins have no colletable value yet. Maybe later, when most of these coins are being refined.