Need some help -first time refining-

[Anonymous]

Hey all.

Im a jeweler, and I'm looking to refine some of my scrap around the shop.

Just as a test sample I have 2 troy ounces of Au in various alloys. Have some white some yellow, and so on all mixed together. I know I can get the gold into solution by using a mix of HCl and HNO3 but that's the extent of my knowledge. Can anyone help with a simple method of getting to .99 Au so I can realloy it? Have some chem in college so im not scared of formulas Thanks in advance.

Best Regards
Phil

 

[lazersteve]

Phil,

Welcome to the forum.

Here's the 50,000 foot overview of the process:

Since your gold is likely a mix of 10 and 14 kt scraps and you are new to refining, you should inquart the scrap as demonstrated in my inquarting video on my website:

http://goldrecovery.us

After inquarting, dissolve the silver out of the 6kt alloy in hot 35% nitric acid as seen in my Separating Gold and Silver video on the same site.

After you get the silver out, dissolve the resulting gold (looks like a brown colored honeycomb/powder) in hot Aqua Reqia (4 parts HCl: 1 Part 70% HNO3 : 1 Part H2O).

You can brush up on the exact details by reading C.M. Hokes Refining Precious Metal Wastes available for download here on the forum. There are a lot of other things you will need, like beakers, burners, filters, testing solutions, etc. You can learn about them in the location listed below.

It wouldn't hurt to take the Guided Tour Link listed in my signature line below, just to get familiar with the terms, testing, and reactions we use here. If you have questions, check the forum search results first, then post a question if you are still not getting anywhere.

Have fun and be safe!

Steve

 

[butcher]

This is a journey, if followed you will learn alot, at the beginning it will look simple to get to the end, then you find the more you learn the more you will need to learn, but if you don't give up, it becomes an adventure.

 

[nickvc]

Phil this is the place to be to learn all and every way to process your wastes, start with C.M.Hokes book which is available as a free download and gives you the basics for refining, especially jewellery scraps,read that then use the search function to research just about any process known and if you get lost post a question and help is on hand.

 

[samuel-a]

hi Phil

wellcome to the no.1 source of info on the net.

may i ask, what ware you doing with your "waste" PM's up until now?
selling or just collecting?

 

[Anonymous]

So far just sending in for refining. I have some chem in college and I thought I'd give it a try for fun. Thanks for all the replies. Glad to know you guys are so accessible.

Best Regards
Phil

 

[4metals]

To recycle the gold back in to more jewelry, you really don't need 99.99 or 99.95 fine gold so inquarting and parting is all you will need to do.

Add silver, 3 times the estimated gold content weight and melt it together (and make sure it is well mixed) to produce a high silver low gold alloy. Pour the molten alloy into cold water to produce a large surface area metallic shot. The high surface area will make it dissolve easier.

Mix up some 50% nitric acid, using distilled water and nitric acid (add the acid to the water) and slowly add the shot to the acid, you will need about 300 to 400 ml of this mixture to dissolve all of the metal.(based on starting with 2 ounces of karat gold) Start with about 2/3 of the acid and when it is exhausted add more acid slowly until all of the metal stops reacting. Notice I said stops reacting and not until all of the metal is dissolved. A little heat will help here but only heat it after the majority of the reaction has quieted down. The bottom of your beaker will have brown flakes which resemble coffee grinds on the bottom of the beaker.

Allow the gold to settle out, it will do this quickly as it is heavy, and carefully pour off the acid being careful to not pour out any gold pieces. Rinse the solids with distilled water and pour off again until the rinse is clear. Save the acid you first poured off and the rinse waters (you can mix them together) for silver recovery.

Now add about 50 ml of distilled water and 100 ml of nitric acid to the beaker with the rinsed gold in it. Heat up the acid and allow it to simmer for about 20 minutes. This is cleaning up any silver which may still be in the gold. After the reaction stops (and there may only be a slight reaction) allow the gold to settle and decant and rinse again.

This good can be dried and re-used for jewelry manufacture, it is a minimum of 99.5 fine and the major contaminant is silver, which you will be adding more of to alloy anyway.

To recover your silver from the acid and rinses you saved, add a slab of copper metal. This will bring down the silver as metal along with any other PM's and produce a silver "cement" which is 99 % silver and can be recycled over and over again to inquart future lots. Just rinse the silver cement and melt it. Over time the weight of your silver will grow as it will also collect the 7 to 8 percent of silver usually present in the alloy you are purifying.

The fumes from the nitric are not the best thing you can breathe, you should do this in a hood or some other means to exhaust the red fumes you will generate in this process.

I have taught this method to many small jewelers who have used it to produce gold fine enough to recycle and cut out their refining expense.

 

[nickvc]

Thats an excellent method from 4metals that should sort out all your solids the only thing i would add to his advice is to avoid mixing any platinum scrap or heads in with the gold save these for separate recovery,this will also work for you lemel if you dont work on platinum.

 

[4metals]

Good point Nick, although he didn't list platinum, it is often used on prong settings. If it were mixed in with the gold some of it would part with the silver but some would remain with the gold.

It is best to remove any platinum before inquarting.

 

[Anonymous]

Great advice guys I will absolutely try that for my jewelry.

Also, on the acid do you mean 50% HNO3 as in {~12M}? Or 50% of a standard Molarity used on this forum?

Besides reusing gold for my own shop, I also buy gold from customers and when I get enough, I usually just sell it directly to a refiner. Is there a simple method for refining to .9999fine or .9995fine so I can make my own bars? I don't think I will ever make a bigger bar that 1kilo but still would like to know for fun.

Is there a method that doesn't involve inquarting, acid volumes aside?

Also, I wanted to thank you guys, I really loved chem in college but we never really got into anything practical. The forum is just great, lots of practical knowledge.

 

[nickvc]

The advice is to use 50% nitric 50% water and most grades will work but its pointless paying over the odds for high grade acids.The refining to higher purity of your gold will need to be through aqua regia as a secondary process but inquartation is still to be advised first.I think that some members who process very large volumes skip the inquartation process but they have assays done to check the silver contents first ,not to be advised until you really know your way round the tried and tested methods that work.Read Harold Vs posts on refining carat golds and you wont go wrong.

 

[Oz]

Typically most use 35% nitric to dissolve the silver from an inquartation of gold. This would also be the same as 50% distilled water and 50% nitric if you are using the standard 69-70% nitric. Many call that 50% nitric because of the portions mixed. It can be confusing how some express concentrations of acids, but you ask good concise questions.

There are many ways to refine gold other than inquartation but there is no better way to start with for karat gold in my opinion. After you have learned to do inquartation you can try other methods based on your starting materials. As you are probably aware being a jeweler there are platinum group metals in white golds and even some yellow golds. Inquartations allow those platinum group metals to go into nitric when alloyed with silver if they do not exceed about 5%. It is an inexpensive way to scavenge them so they can be recovered from the silver later instead of worrying about them when you are precipitating your gold.

You have been given good advice but you have just touched the edge of what can become a very complex subject depending on what your end goals are.

Welcome to the forum.