# Processing jewellery



## LaurenceOs (Jul 20, 2009)

I've got a 9ct solid rose gold ring, its 5.5g in weight. I was wondering if this should be processed in AR straight away?

I've tried searching the forum for the info required but the search thing doesn't seem to work too well.


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## goldsilverpro (Jul 20, 2009)

Try first leaching it by covering it in nitric acid, about 60%, by volume. Heat the solution fairly hot but not boiling. I would guess that it will take about 30 ml, or so, of the 60% nitric to do the job. Nine karat is low enough that the nitric should dissolve all the base metals, leaving the gold. The ring will turn brown (gold) and will often stay in one piece. To tell if all the base metals have dissolved, probe it with a glass rod. If you feel any hard spots, keep leaching it until it completely collapses and no hard spots are evident. 

The gold won't be quite pure. You can then rinse and decant (carefully pour off the rinse water without losing any of the brown gold) several times with distilled water, and dissolve the brown residue in aqua regia. I would cover the gold residue with about 15 ml of muriatic acid, heat it until a little steam is seen, and then add concentrated nitric dropwise (I use an eyedropper) until the brown gold is dissolved. There may be some non-brown residue, silver chloride or dirt, that won't dissolve - don't try to dissolve this or you'll end up using two much nitric. Let the nitric work a bit between additions. It shouldn't take more than about 2 ml (about 40 drops with a standard straight glass eyedropper obtained from a drug store) of nitric acid - try very hard to not use an excess - be patient and let it work between additions. Remove from the heat and dilute with water to about 4 times the volume. Allow to cool and filter and rinse. Drop the gold with SMB dissolved in a minimum amount of water. If you haven't used too much nitric, it should take between 2 to 4 grams of SMB.


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## LaurenceOs (Jul 20, 2009)

Really? What will the ring look like when the nitric is done? i thought that the way it is alloyed it, may need all dissolving and precipitating off metals seperately before droping gold.

I have 1 bottle of 70% nitric that I searched for weeks and weeks for and ended up buying from someone on this forum.

Also how should i heat this? I assume you use a pyrex bowl, but these cant be used on a hob can they?

Thanks for your help!

Laurence.


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## goldsilverpro (Jul 20, 2009)

Pyrex bowls, measuring cups and other thick Pyrex containers won't take direct heat and will break. You need thinner Pyrex, such as a drip coffee pot or a beaker. Even these, however, can break if you put them directly on a hot plate. No matter what you use, I would put the dissolving vessel inside of a larger vessel that won't break and put the larger vessel on the hot plate. An ideal larger vessel is a Corning Ware dish.

Since you have such a small amount of gold (about 2 grams), the size of the dissolving vessel is important. If it's too large (wide), the small amount of acids I've recommended won't cover the ring. Ideally, you should should use a beaker not larger than 250 ml. I would also cover the beaker with a watch glass or a small heatproof ceramic saucer while heating, to prevent the acid from evaporating.

Thinking further, you may be able to get away with using a very small Pyrex dish inside of a Corning Ware dish. Heat it very slow to start with and you may not break it. If it does break, you will still catch everything inside of the Corning Ware dish.

The nitric leach method I've given will only work on karat golds of 10K, or less. If above 10K, the larger amount of gold will block the penetration of the acid. The alloying metals in karat golds are usually copper, silver, nickel, and zinc, all of which will dissolve in nitric acid. 

If the silver is over 10%, which it very well may be, you will not be able to dissolve all the alloy directly in aqua regia. The simplest way is to try nitric alone first.

The standard method on this forum is to melt enough silver with the karat gold to reduce the gold content to 25%. This is called inquartation. The base metals and silver are then dissolved in nitric acid, as in the method I gave you on my first post. Actually, my method of using nitric to treat 10K or less gold is identical to the inquartation method, except you don't have to go through the trouble of melting, adding silver, and shotting the alloy.

If the gold content is much more than the 9K marking (which is very unlikely) and my method doesn't work, you haven't lost anything. You can still use the inquartation method.

The method I gave for aqua regia avoids the need for urea or boiling down. The most important thing, however, is to use only enough nitric in the aqua regia to barely dissolve the gold. If you end up adding too much, you'll have to get rid of it by using Harold's standard method of boiling down.


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## LaurenceOs (Jul 20, 2009)

Utterly sound advice GSP!

Really appreciated!

Just for future reference, as i am still a bumbling newbie, how would you approach higher carat materials?

Thanks again!


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## goldsilverpro (Jul 20, 2009)

For the beginner, the most fool-proof method to do higher karat gold is to inquart with silver and then use nitric to dissolve everything but the gold. It still won't be pure and you'll still have to use aqua regia. If you do all this correctly, your final ingot of gold will likely be quite pure. I would follow Harold's method for inquartation. Search for inquartation, inquarting, or inquart. For each search, type in Harold_V where it says Search for Author. He has explained the inquartation method several times in great detail.

Unless the silver was too high, I usually dissolved higher karat golds directly in aqua regia. However, there are a lot of potential pitfalls in this method and you should have a lot of knowledge and experience to attempt it. It can be very tricky to get all the gold and to get a final product that is pure.

If you had had a mixture of karat gold items, including some 9K, that you wanted to run at the same time, I would have suggested inquarting the whole batch. However, you only have one 9K piece. For that reason, it's worth trying to dissolve the base metals directly in nitric, without going through the hassle of inquartation. If the gold is really 9K, it will work.


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## lazersteve (Jul 20, 2009)

I recently posted an inquarting video on my website.

Steve


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## Oz (Jul 20, 2009)

To add to GSP’s excellent advice save the nitric you used for dissolving your gold rings impurities. If you cement this on copper you will almost certainly recover some silver, possibly palladium, and platinum that can go into solution in the presence of silver as well. What you recover from your nitric depends on your rings alloy but almost all gold alloys contain some silver. Your rose gold may not contain much due to needing a greater quantity of copper for its color but it is worth doing and being in the habit. GSP can speak with more knowledge than I can as to the typical elements in a rose gold alloy.

Have fun!


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## goldsilverpro (Jul 20, 2009)

Oz is right on, on all points, as usual. 

I should have mentioned keeping the nitric solution for silver recovery.

According to this, 9K rose gold contains 20% silver. If that is true, this alloy would never dissolve in the normal aqua regia process. Depending on the shade desired, however, there are probably many different formulas. For the same karat gold, the lower the silver, the higher the copper. The higher the copper, the more red the alloy.
http://www.squidoo.com/rosegold


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## LaurenceOs (Jul 20, 2009)

Wow this forum really is the mutts nutts


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## goldsilverpro (Jul 20, 2009)

Ask, and Ye shall receive.


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## LaurenceOs (Jul 27, 2009)

GSP! Where could I find a suitable container for leaching?

Ta

Loz


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## goldsilverpro (Jul 27, 2009)

I covered the containers needed earlier on in this thread. Beakers are ideal, but to go cheap, a Pyrex drip coffee pot works great. Over here, I often see them in second hand stores, along with Corning Ware dishes.


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## LaurenceOs (Jul 27, 2009)

i just dont want anything thats gonna crack with the heat.

Cheers


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## wrecker45 (Apr 4, 2011)

could you put the container in a crock pot with water to heat it? or could it still crack?...Jim


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## seawolf (Apr 4, 2011)

To be sure the nitric acid is completely spent could putting in a piece of sterling silver be used? And the silver cemented out at a later time?
Mark


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## samuel-a (Apr 5, 2011)

seawolf said:


> To be sure the nitric acid is completely spent could putting in a piece of sterling silver be used? And the silver cemented out at a later time?
> Mark



Sure, that's one of many ways to hit two birds with one stone.
You will need heat to reach complete saturation.


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