Parting Method

D

Dave

New Member
#1
Hey Guys

I have just got more involved in the parting area in work and I am questioning the method that we use. Seems a bit overkill to the methods I have found on the Internet and in books.

We start it off in cold 1-7 nitric acid in porcelain crucibles on a hot plate @ 200oC. This is left to simmer until the reaction ceases. We then top up with 50% nitric and evaporate to half the volume.

Then we decant off the solution, wash with pure water and then put back on the hot plate in full 50%. Reduce volume to half again. Decant off and then wash 3 times.

Just wondering what method(s) everyone else uses?
 
fireguy

fireguy

Supermoderator
#2
Hey Guys

I have just got more involved in the parting area in work and I am questioning the method that we use. Seems a bit overkill to the methods I have found on the Internet and in books.

We start it off in cold 1-7 nitric acid in porcelain crucibles on a hot plate @ 200oC. This is left to simmer until the reaction ceases. We then top up with 50% nitric and evaporate to half the volume.

Then we decant off the solution, wash with pure water and then put back on the hot plate in full 50%. Reduce volume to half again. Decant off and then wash 3 times.

Just wondering what method(s) everyone else uses?
Dave:
What kind of samples are these? Routine assay samples? Bullion? High grade products?

That does seem a bit extreme. Was this method developed against any testing to show the benefit? Or (more likely) "just what was always done"?
 
D

Dave

New Member
#3
They are routine assay samples of varying materials, from high grade bullion to electronic scrap. I doubt the method was tested. It was probably the first method that was tried that worked and was never optimized.

I have just started testing the method of starting off in 1-7 until action ceases. Decanting off the silver nitrate and then (with out washing with water) putting back on in full 50% to make sure parting is complete. Then 3 washes before drying and annealing. This seems sufficient enough in my opinion. And much quicker.

Is this method similar to what you use?

I have read some methods that get the nitric acid hot and before dropping the beads in. I think this is to stop the gold from breaking. Is this true and does it work?
 
fireguy

fireguy

Supermoderator
#4
They are routine assay samples of varying materials, from high grade bullion to electronic scrap. I doubt the method was tested. It was probably the first method that was tried that worked and was never optimized.

I have just started testing the method of starting off in 1-7 until action ceases. Decanting off the silver nitrate and then (with out washing with water) putting back on in full 50% to make sure parting is complete. Then 3 washes before drying and annealing. This seems sufficient enough in my opinion. And much quicker.

Is this method similar to what you use?

I have read some methods that get the nitric acid hot and before dropping the beads in. I think this is to stop the gold from breaking. Is this true and does it work?
Dave: usually, breaking of the gold is caused by too much silver being present. We always added hot nitric. I think 1:7 is a little weak- maybe try 1:4. After the reaction stops I don't think you would need to add fresh acid- just leave it cooking a bit after the reaction stops and wash a couple of times with distilled water. Maybe do a couple of tests comparing this to your current method.
 
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