gold re-disolved after dropping?

[cnbarr]

Well here is what I have, I started with 525g broken up 486 ceramic cpu's. I removed the lids with mapp torch prior to smashing. I soaked the lids in warm 75ml 50/50 dilute and soaked the cpu's in 550ml 50/50 dilute nitric on warm for 4 hours. I let them sit over nite with heat off, then warmed them back up in the morning to soak for another 8 hours. After the fuming stopped I filtered, tested w/stannous, and rinsed 3 times with distilled water.

I then added the foils from the lids in with the cpu's, from there I mixed my AR as follows, 100ml distilled water, 200ml Hcl, 25ml HNO3, and heated to warm(at this point I realized not all base metals were dissolved in the nitric bath). An hour later the reaction had ceased so I added another 100ml Hcl, to help completely cover the cpu's, and added another 25ml HNO3. About 2 hours after that I added another 25ml HNO3 because there were still a few gold foils floating around. Now all values appeared to be dissolved, my determination for this was all the silicon chips had slipped off and were now in the bottom of the beaker. I shut the heat off and let the AR sit to cool over nite. Total soak time in AR approximately 17 hours.

In the morning I filtered and rinsed cpu's with distilled water, then tested with stannous got a nice deep purple. I then evaporated down to half volume refilling with Hcl 3 times and let cool to room temp. Then I dissolved 4.5g SMB in 75ml warm distilled water and proceeded to drop the gold. The solution didn't clear out (I assume because it was a slightly dirty solution) but I observed the cloud form and let settle over nite.

Here is the part I found peculiar, I checked the solution this morning and had a nice layer of mud in the bottom. I tested one more time with stannous and the result was negative, but I noticed what appeared to look like a little gold powder floating on top. So I thought if I warmed it up a bit it might break the surface tension enough to get it to settle. I pulled it off the heat to let it cool back down there was no powder on top, but I noticed there were small air bubbles coming from the powder in the bottom and 10 min. later it was all dissolved. I tested with stannous and sure enough it all went back into the solution.

Does anyone have an idea as to how it could drop the gold then redissolved it after addition of heat?
Thanks in advance for the help and I hope I've given enough detail.

 

[samuel-a]

Does anyone have an idea as to how it could drop the gold then redissolved it after addition of heat?

You still had some free nitric acid in the solution.
At very low concentration, you will be able to reduce the gold with no problem, though, over time or with heat, the gold may re-dissolve.

By adding a little excess SMB, you could avoid that.

But the first thing you should consider is adding your nitric incrementally, just enough to dissolve all metals and avoid the any excess.

 

[Photobacterium]

Does anyone have an idea as to how it could drop the gold then redissolved it after addition of heat?

You still had some free nitric acid in the solution.
At very low concentration, you will be able to reduce the gold with no problem, though, over time or with heat, the gold may re-dissolve.

By adding a little excess SMB, you could avoid that.

But the first thing you should consider is adding your nitric incrementally, just enough to dissolve all metals and avoid the any excess.

does this mean that you can sometimes use cold temperatures to "keep the gold precipitated" if you suspect the presence of nitric ?

 

[cnbarr]

does this mean that you can sometimes use cold temperatures to "keep the gold precipitated" if you suspect the presence of nitric ?

Samuel,
I was going to ask this same question. And would it be my understanding that one can precipitate, in a slight presence of nitric, from a cold solution.? And the same solution when heat is introduced would speed up the reactivity of the nitric thus redissolving the gold? So cooler temps hinder the reactivity of a slight presence of nitric and warmer temps enable the reactivity of nitric.

 

[samuel-a]

A very low concentration of free nitric in solution will not hinder precipitation while cold/room temp'.

If gold redissolves upon heating or long dutation, SMB could be added again to precipitate.


I'm dropping the gold at room temp' usually, later I'm boiling the solution & precipitated gold for 5-10 minutes. (this agglomorate the powder tightly and settling most of the colloid formed).
It rarely happens that i see gold re-dissolve in that boil. This is because i'm almost never adding excess nitric while dissolving the gold.


GSP had described that trick countless times before.

 

[cnbarr]

Thanks Samuel that makes perfect sense, I appreciate your knowledge and responses. Hopefully by tomorrow I will post a pic of my first button.

Thanks again and have a fantastic day everyone!

 

[Dr. Poe]

It's both recommended and a common practice in chemistry to add a little bit of the precipitating agent to the washes. Dr. Poe

 

[leondavids]

It's both recommended and a common practice in chemistry to add a little bit of the precipitating agent to the washes. Dr. Poe

Hello Dr Poe , i don`t totally grasp what you are saying here .Do you mean once you have filtered and washed ( x3 ) it would be good practice to 1) test washed solutions for values with stannous or ,(2) or test for values by adding a little bit of the precipitating agent .Could you be so kind as to educate me?

Thanks in advance.
Leon

 

[Dr. Poe]

It's both recommended and a common practice in chemistry to add a little bit of the precipitating agent to the washes. Dr. Poe

Hello Dr Poe , i don`t totally grasp what you are saying here .Do you mean once you have filtered and washed ( x3 ) it would be good practice to 1) test washed solutions for values with stannous or ,(2) or test for values by adding a little bit of the precipitating agent .Could you be so kind as to educate me?

Thanks in advance.
Leon

Like I said, it's a common practice of chemists. In all chemistry, reactions work both ways, forming an equilibrium.
When a gas escapes or a precipitate is formed, the reaction "swings to the right" and is non-reversible. Adding a drop of the precipitating reagent insures that tiny amounts do not redissolve. It's not just nitric or noxxes that cause resolution any other combination of oxides and halogens will cause problems. When gold is in a very fine (small) state, it is the most vulnerable to corrosion. When it's in nitric acid, even salt from a drop of sweat can complex it. Converting it to HAu(N03)3 (which decomposes at 70C or addition of hot water. So listen to these guys, resolution of gold usually is from remaining trace solvents. Addition of a tiny bit more of SMB defends against resolution and also in the wash waters. Dr. Poe

 

[leondavids]

It's both recommended and a common practice in chemistry to add a little bit of the precipitating agent to the washes. Dr. Poe

Hello Dr Poe , i don`t totally grasp what you are saying here .Do you mean once you have filtered and washed ( x3 ) it would be good practice to 1) test washed solutions for values with stannous or ,(2) or test for values by adding a little bit of the precipitating agent .Could you be so kind as to educate me?

Thanks in advance.
Leon

Like I said, it's a common practice of chemists. In all chemistry, reactions work both ways, forming an equilibrium.
When a gas escapes or a precipitate is formed, the reaction "swings to the right" and is non-reversible. Adding a drop of the precipitating reagent insures that tiny amounts do not redissolve. It's not just nitric or noxxes that cause resolution any other combination of oxides and halogens will cause problems. When gold is in a very fine (small) state, it is the most vulnerable to corrosion. When it's in nitric acid, even salt from a drop of sweat can complex it. Converting it to HAu(N03)3 (which decomposes at 70C or addition of hot water. So listen to these guys, resolution of gold usually is from remaining trace solvents. Addition of a tiny bit more of SMB defends against resolution and also in the wash waters. Dr. Poe

Thanks for the lesson.
Leon.

 

[cnbarr]

Just an update I followed Samuels words of wisdom and dropped my gold and washed and gave it a second refining and just dropped again. So hopefully I'll have a pic of my first button soon.

Addition of a tiny bit more of SMB defends against resolution and also in the wash waters. Dr. Poe

Correct me if I'm wrong but isn't the point of washing procedures to wash away the excess elements, chlorides, and chemicals, including SMB? It seems adding SMB to your washes would be counter intuitive. I'm still new, so anyone please feel free to educate me if I am mistaken on this.

 

[Dr. Poe]

Just an update I followed Samuels words of wisdom and dropped my gold and washed and gave it a second refining and just dropped again. So hopefully I'll have a pic of my first button soon.

Addition of a tiny bit more of SMB defends against resolution and also in the wash waters. Dr. Poe

Correct me if I'm wrong but isn't the point of washing procedures to wash away the excess elements, chlorides, and chemicals, including SMB? It seems adding SMB to your washes would be counter intuitive. I'm still new, so anyone please feel free to educate me if I am mistaken on this.

The tiny bit of reagents added to washes will leave in the wash water. Dr. Poe

 

[richardbal]

Hi Every body
well thanks guys for all the wunderfull informations on here.
well if u wana dream then dream big?????
i have a question about AP solution.
i put about 30 g plated pins in a 2 to 1 solution hcl and h2o2
all work nice and i see the gold swim around .to make quicker the reaction i put the solution on hot plat but just 80 degree
and i can see is no more gold on pins and in the solution the gold is verry small pices.and after heat for sometime i saw some white cristall ?????
so do some one have a idee what can be
thanks in advance for any help
richard

 

[Anonymous]

Give me one second guys,please.
Dr.Poe,
I want to publically apologize for the comments that I made towards you on that other thread.The way I feel towards you serves no purpose being aired publically.It won't happen again.
Ok that's all.

 

[cnbarr]

Rather then start a new thread I figured I would post here since the button came from the batch of cpu's pertaining to this post. So here it is 3.2g from 1.1lbs of 486 cpu's, I know I lost some values, but I feel I did pretty well even with my lack of experience.
I would like to thank everyone at the forum, it would not have been possible without all of you, so thank you, thank you all very much! (my emmy award speech :wink: )

And in light of my new scrap supplier I am going to run a contest (just trying to spread the love) as soon as I work out the logistic of it, but not until Barren's silver contest wraps up, so about the first of February, stay tuned!

Thanks again everyone, I hope to some day contribute some knowledge to the forum.

 

[cnbarr]

It didn't post the other pic. so here it is.

 

[jimdoc]

Nice! How many 486 cpu's was that?
And nice of you to keep the results of this thread all in one.

Jim

 

[cnbarr]

Nice! How many 486 cpu's was that?
And nice of you to keep the results of this thread all in one.

Jim

Thank you, it was approximately 22pcs, I had a couple of broken ones and compared their weight to hole ones, but it was 1.17 lbs total. I estimated about 19.5 486 cpu's per pound, and based off my research on the forum I estimated in between 2.5-3.0g per lbs. I know I lost some values, so with more experience, I feel I can recover upwards of 4g/lbs max.

I just started 2.5lbs or 52 pcs tonight, I am going to try and be much more meticulous with this batch to see if I can get a better average recovery rate w/486 cpu's, since I have access to more than 50-60lbs per month.

I am greatly pleased with my first button, so please feel free to critique it's quality, if there is room for improvement please let me know!

 

[samuel-a]

Well done cnbarr !

Yield seems fair too.

 

[Harold_V]

I am greatly pleased with my first button, so please feel free to critique it's quality, if there is room for improvement please let me know!

In my opinion, it looks quite good. I see traces of something on the surface, but just traces. In general, it's quite shiny, and the pipe and color look good. For a first venture, I'd say well done. It's certainly far better than my first button those many years ago.

Harold