My first refine using a known PM percentage as a standard

[didit]

Hello All,

So after about 10 months or more of studying and building the required infrastructure (read Hoke, the forum, plenty of Sreetips videos, and built a fume hood and oxy/propane setup), I completed my very first refine! I bought this on ebay (paid a little too much for it I think) mainly because it is dental grade gold that has the precious metal contents of gold, silver, and palladium with the percentage of each PM listed. I figured it would be a good known standard to conduct an experiment and see how close I get to the listed percentages and the size was just about right for practice.

In the end I produced my first gold refined button of 4.81 grams!

Sadly, I missed my calculated yield of 5.727 grams by about 1 gram but I expected there to be some loss due to newbie mistakes. The bright side is that I suspect where the loss occurred and there is probably some yet to be reclaimed gold in the future from my gold waste jar and sweeps. Funny but I didn't realize until I was writing this post that the percentages listed on the packaging of the gold pills doesn't add up to 100%.

There is 46% gold, 6% palladium, and 39.5% percentage silver which equals 91.5%. Makes me think that maybe I didn't lose much after all but I'll have to think on that some more. I am curious now what was the remaining 8.5% metal content. Hmmm.

As for the palladium and silver I'll have to get to those another day as I don't have any DMG but when I get some I'll attempt to drop the palladium and then the silver. The silver percentage should still be able to be calculated since I know how much I added for inquartation.

So I'm fairly pleased with the result thus far and I learned a lot of things that you can only learn from hands-on experience. I have plenty of pictures but will only post a couple for now.

Cheers!

 

[nickvc]

Well done very nice.
To see if you did lose any gold have you got the starting weight , if it was around 10.5 grams you have it all if it was 12.5 grams you have some lose.

 

[didit]

Well done very nice.
To see if you did lose any gold have you got the starting weight , if it was around 10.5 grams you have it all if it was 12.5 grams you have some lose.

The starting weight was 12.45 grams. These are some process points that might have been where loss was the most but all are suspect so maybe you guys can enlighten me to the most likely culprit.

1. The point I think I lost the most was at the initial nitric baths removing the base metals because of the color of the solution. I kept it on heat too long and/or adding dilute acid/water because the solution was brown and it got syrupy. I had to add distilled water at one point because it was boiling off. I know now after going over Hoke and the forum that it was probably that color because of the palladium. I was just expecting a more blue green at the start but it wasn't at that point. In the end, my silver jar contents are a dark green (palladium and silver) which I think is right but correct me if I wrong. (picture below).

2. The second point I may have some loss is that I couldn't seem to wash down all of the yellow solution from the sides of the filters when filtering after AR. The second picture is of my AR result and the third picture is after I kept trying to wash the sides of the filter with water. Did however have a nice stannous test for gold. (pictures below).

3. My first attempt at dropping the gold with SMB didn't seem to react correctly. I think it was because I had a lot of wash water in the solution so after adding HCl it dropped the gold. The second gold drop after the 're-refine' of the gold powder went off perfectly though. (picture below is not as clear as the final product was but it was a tad murky).

4. One issue I had that I'm not sure about is that when draining off the clear solution after the gold drop there was a very fine film of brown particles floating at the top of the liquid. Stannous test showed no gold in solution. I couldn't seem to avoid the fine powder floating around being drained off. This solution is now in a separate bucket that will be my 'gold refining waste' bucket. (perhaps I didn't let it settle long enough after the drop?)

I'm sure there are plenty of newbie mistakes in here but that's kind of the point. I work in a laboratory environment but I am not a chemist by any means. Trial and error (lots of error sometimes) is natural. This is why I started with a fairly small sample. Practice makes perfect.

 

[Yggdrasil]

The starting weight was 12.45 grams. These are some process points that might have been where loss was the most but all are suspect so maybe you guys can enlighten me to the most likely culprit.

1. The point I think I lost the most was at the initial nitric baths removing the base metals because of the color of the solution. I kept it on heat too long and/or adding dilute acid/water because the solution was brown and it got syrupy. I had to add distilled water at one point because it was boiling off. I know now after going over Hoke and the forum that it was probably that color because of the palladium. I was just expecting a more blue green at the start but it wasn't at that point. In the end, my silver jar contents are a dark green (palladium and silver) which I think is right but correct me if I wrong. (picture below).
Heat will not create losses in a liquid by itself. Boiling will though, as small droplets containig values are trowed out of the beakers.

2. The second point I may have some loss is that I couldn't seem to wash down all of the yellow solution from the sides of the filters when filtering after AR. The second picture is of my AR result and the third picture is after I kept trying to wash the sides of the filter with water. Did however have a nice stannous test for gold. (pictures below).
Of course all the pregnant solution need to be collected and added before dropping the values .
This is not a major issue though as the values are still in the filters and will be "found" when the papers are processed.

3. My first attempt at dropping the gold with SMB didn't seem to react correctly. I think it was because I had a lot of wash water in the solution so after adding HCl it dropped the gold. The second gold drop after the 're-refine' of the gold powder went off perfectly though. (picture below is not as clear as the final product was but it was a tad murky).
One important thing to remember is that the solution pH should not get too high.
Keep it at not higher than 2-4

4. One issue I had that I'm not sure about is that when draining off the clear solution after the gold drop there was a very fine film of brown particles floating at the top of the liquid. Stannous test showed no gold in solution. I couldn't seem to avoid the fine powder floating around being drained off. This solution is now in a separate bucket that will be my 'gold refining waste' bucket. (perhaps I didn't let it settle long enough after the drop?)
This may or may not be fine Gold powder floating on a surface film, it should be collected simmered in dilute Sulfuric and it will drop.

I'm sure there are plenty of newbie mistakes in here but that's kind of the point. I work in a laboratory environment but I am not a chemist by any means. Trial and error (lots of error sometimes) is natural. This is why I started with a fairly small sample. Practice makes perfect.
Another thing is that if you have a small lot the amount of liquid used for testing will also cause a "loss"
Use a paper strip as you do, but add just add a small drop of pregnant solution and then a drop of Stannous next to it. This way your test will be as good but consume lass liquid. Remember to add the strips to the filter pile or a designated pile.

I'll comment inside the quote in Bold

 

[didit]

I'll comment inside the quote in Bold

Wow. Thanks for that advise.

I had a watch plate on the beaker during the nitric baths but it did get to a boil and that was probably a major issue as you pointed out.

I didn't know about the pH balance but I do have some litmus test strips so I'll make sure to check that next time.

Filters and also the stannous test strips are being collected in a dedicated pull out trash can I built into my fume hood table so that's covered although I will dip the test strips less into the solution for now on.

For your last point of advise I'm really interested now in trying to take the filtered gold wash solution and simmering it in dilute Sulfuric. That will be interesting. So two question for this point:

1. How much water to Sulfuric for dilution? 50/50?

2. After simmering in Sulfuric (regardless if gold drops or not) what to do with the liquid? Can it go back in the 'gold refining waste' bucket or should it just go in separate 'final' waste bucket?

 

[Yggdrasil]

Wow. Thanks for that advise.

I had a watch plate on the beaker during the nitric baths but it did get to a boil and that was probably a major issue as you pointed out.

I didn't know about the pH balance but I do have some litmus test strips so I'll make sure to check that next time.

Filters and also the stannous test strips are being collected in a dedicated pull out trash can I built into my fume hood table so that's covered although I will dip the test strips less into the solution for now on.

For your last point of advise I'm really interested now in trying to take the filtered gold wash solution and simmering it in dilute Sulfuric. That will be interesting. So two question for this point:

1. How much water to Sulfuric for dilution? 50/50?

2. After simmering in Sulfuric (regardless if gold drops or not) what to do with the liquid? Can it go back in the 'gold refining waste' bucket or should it just go in separate 'final' waste bucket?

Just some 10-20% Sulfuric.
The liquid goes into the stock pot, yes.

 

[didit]

Just some 10-20% Sulfuric.
The liquid goes into the stock pot, yes.

Awesome. Thanks. I'll give a try next weekend.