new project

[joheleh]

hi guys, i have 18g of 18k scrap gold, is it necessary to inquart them? may i pass them trough nitric solution without inquarting? it's just a question, i don't wanna be "quick and stupid" but i've some difficulties in finding pure silver to use as the base metal.
So, what are the pros&cons about eviting inquartation with 18k scrap jewelry?
thanks to everybody who will help.

 

[resabed01]

Yes you must inquart. You don't need to use silver, copper will work too. Hoke states in her book you can use pretty much any base metal as long as it's attacked by the acid.

Edit: Also, you don't need pure silver to inquart, you can also inquart with sterling which is roughly 7.5% copper anyways. Sterling is easy to find and inquart with and using it has the added bonus of removing most of the copper when done.

 

[FrugalRefiner]

Whether or not you must inquart depends on the nature of the gold. If it's typical yellow or red/pink gold, and you can roll it thin or granulate it well, you may do fine without inquartation. If it's green gold, you'll likely have problems if you don't inquart. If it's white gold containing palladium, inquarting with silver can aid in the separation as the PGMs tend to follow, at least to some extent, the silver.

Hoke does a much better job of covering the pros and cons of inquartation in chapter VI than I can do in just a few lines here.

Dave

 

[goldsilverpro]

Nitric won't touch the base metals or silver in 18K gold - the gold percentage is way too high to allow the nitric to penetrate. About the highest karat nitric can be used on is some 10K. Even then, it is iffy. I have had luck on some 10K class rings but that is probably because they were actually under-karated and were only about 8K, or so.

Inquartation brings the gold to 6K. That will work with nitric in every case if the alloy is well blended during melting.

You can inquart with copper but it will take 3.4 times more nitric than silver does. It also seems to go much smoother with silver. The only times I have used copper is when I had no silver.

Edited.

_____________________

Depending on the silver content, you may or may not be able to totally dissolve the gold directly in aqua regia (AR). However, assuming you have yellow gold, the silver tends to run higher in 18K than in 14K or 10K- my books say usually from 10-20%. When the silver is 10% (some people say 8 or 9%), or more, the silver chloride will form a hard impervious crust on the surface and will prevent the AR from penetrating. Like Frugal said, you can first roll the gold very thin but, if the silver is on the high side, even that might not work too well.

I would inquart. If you do it right, it always works, it's easier in the long run, and you'll get all the gold.

 

[FrugalRefiner]

I stand corrected. I should have paid more attention to the 18K. I guess my brain skipped over it when I read 18g of 18k.

Thanks GSP.

Dave

 

[joheleh]

thanks guys, you're very helpfull, i'm going to use copper as base metal, i'll use copper pipes ( opened, flattened and reduced to a small pellets). I've calculated the amount of 37,5g (for 18.7grams of scrap 18k gold) to inquart my scraps, so i will use a ratio of 2,5ml HNO3/1g of base metal...maybe it's too much, maybe it's right, anyway i've read that ratio it's a good compromise. what do you think?

 

[goldsilverpro]

thanks guys, you're very helpfull, i'm going to use copper as base metal, i'll use copper pipes ( opened, flattened and reduced to a small pellets). I've calculated the amount of 37,5g (for 18.7grams of scrap 18k gold) to inquart my scraps, so i will use a ratio of 2,5ml HNO3/1g of base metal...maybe it's too much, maybe it's right, anyway i've read that ratio it's a good compromise. what do you think?

I came up with the same amount of copper that you did. However, it will probably take more nitric. For copper in an open top vessel, it takes about 4.15 ml of nitric per gram. However, if you cover the beaker, it can take less. You won't know exactly how much it will take until you do it. First cover with distilled water, heat it a little and add the nitric in increments. When the reaction slows down, add another increment. When an addition produces no reaction, stop adding. Although it's wasteful, it doesn't hurt to use a little too much nitric. Better too much than too little. After it's all dissolved make sure that you have at least as much distilled water as nitric before you allow the solution to cool. Otherwise, the copper nitrate can form crystals.

You can find this process in greater detail in many different threads on the forum. I've written it up many times and so has Harold_V (and, others). The gold will not be quite up to purity standards and, if you want it purer, rinse it well and use the aqua regia process. Here again, it's all on the forum, many, many times.

 

[joheleh]

I've another question. I've estimated 37.4g of base metal for 18.7g of 18k but....when i calculate the amount of nitric needed for dissolution i've to make it for more than 37,4g of base metal ( because the scrap gold before inquarting contain some more base metal into 18k alloy), right?
i.e.:
18.7g of 18k (14.025g of pure gold + 4.675g of base metal)
inquarted 56.61g of 6k (still 14.025g of pure gold + 42.075g of base metal)

so, when i'll calculate the volume of nitric i have to do it for 42.075g...and not for 37.4...am i wrong?
Maybe it's a silly question, but i wanna be sure to make a good job.

 

[goldsilverpro]

Don't worry about the exact amount. The amount you need depends mainly on your setup. You won't know until you actually do it. In general, if you add the nitric in increments and stop adding when there is no reaction after a small addition, you'll know.

Don't boil the solution. When you add nitric, you must be able to tell whether or not a reaction (fizzing and foaming) occurs. When you boil it, the boiling action looks similar to the fizzing, etc., and you can't tell what is actually going on.

The idea is to dissolve all the copper, silver, etc. away from the gold, even if it takes a little more or less nitric than you calculated.

Refining is more of an art than a science and actual experience in doing it is, by far, the best teacher.

 

[rickbb]

Refining is more of an art than a science and actual experience in doing it is, by far, the best teacher.

Second that, when I started I read and read for months and still screwed up my first 2 batches. Even after I was doing decent at gold, I still managed to screw up my first attempt at silver.

You need to know what and why it's doing what it does, but you still have to learn by seeing it happen a few times before it really sinks in.