Sulfamic acid

[kjavanb123]

All,

This is my first time encountering this, I have an AR solution whic I added solid sulfamic acid no fizzing, but when I add SMB it shows the brown fumes?

 

[arsenic123]

Please give more details regarding the material, type of scrap, what did you do, how much chemicals you added,etc. Then only anyone can help you here.

 

[nickvc]

If you have noxxing occurring you haven't got rid of all the nitric, the sulphamic I believe converts the free nitric to sulphuric which is good as it will precipitate any lead from your solution but it will need filtering before precipitating.

 

[kjavanb123]

I tried AR which I already done few times successfully on CPUs removed from telecomm boards, first I boiled the cermaic CPUs in hydrochloric acid, after most of the pins were dissolved I added nitric acid in 25 ml incriments, then I would add another 25 ml to a solution which has 3 lbs of cermaic CPUs, I stopped nitric addition until any visible gold was dissolved no more reaction when adding nitric, so I pour it off, add cold water to perticipate silver chloride filter, then dilute the solution to twice the volume, dropped a spoon of SMB and got this



So I went ahead and added a teaspoon of sulfmaic acid, and no reaction or fizzing occured, and now stannus test shows negative!!! I mean this is really annoying.

This is CPUs batch after AR leach was completed.



Any help is much apperciated.

Regards,
Kevin

 

[Pantherlikher]

Hey Kevin.
2009 you've been a member and this is your description of what you are doing?.

First, I would smash up the CPUs alittle better. Some gold wont get an acid bath unless you let sit in active acid for a long time, like a week, or alot of aggitation.

You soaked in HCL and then added Nitric? Hopefully you filtered off the HCL soak solution before adding fresh HCL + nitric.

It does not look like you rinsed what's left very well.
You added SMB before Sulfamic acid,(denoxing)?
How long did you allow dropping time?

Not to sound nasty or mean but it sounds like a newbie watched a few youtubegonnahurtyou videos, had some success before, but now nothing and want us to tell you how or what went wrong instead of learning the process and why.
A log step by step of what you are supposed to do would be helpful to get All the steps in order would help alot more then any of us can help.

B.S.
...I'm honest, not feelings sensitive...

 

[kjavanb123]

No hard feelings, here is the step by step of what I did;

1- Crushed the CPUs one by one and made sure all gold wires inside the silican wafer is accessble by acid

2- Dropped all crushed 3lbs of CPUs into a 2 liter beaker, then added hydrochloric acid and heat.

3- After half an hour or so in hydrochloric acid, and I assumed tin and lead are dissolved, without rinsing it out, I added first 25 mls of nitric acid, and reaction started.

4- Few more nitric acid addition and I didnt see any gold dissolving, so I let the solution sit over night, and returned to it this morning, unknowingly added some peroxide, 20 mls, then nitric, and kept adding nitric until all the visible gold was dissolved.

5- Stannous tested very positive at this stage, so filtered a liter of solution and added water, to dilute it, added SMB, and brown foams appered, so I went ahead and added sulfamic acid, no reaction, I dissolved 20 grams of sulfamic acid inside boiling water then added to the solution no reaction, then added SMB and still got brown foams

That is where I left it to find some solution.

Thanks
Kevin

 

[Anonymous]

If these were the CPUs from your other thread i.e. The telephony ceramics, then you could have popped the caps off with a heat gun first. Stored those separately for processing later. Then broken the ceramic up to expose the gold as you did (hey you got one bit right), and then processed the lot in AR.

As Panther said, I'm not sure why after 5 years as a member you have done it this way.

As much as I don't like saying this - read the basics dude.

 

[kjavanb123]

Yes they are from telecomm boards, I followed what I have read here, but I guess used excessive nitrics, I also read using sulfamic acid, which after more reading Steve mentioned he uses it solid added to hot solution until no fizzing, I added mine to room temprature, I will try to add it while solution is hot.

Please advise.

Regards
Kev

 

[Pantherlikher]

Much better a description.
Harold might help with more of a solution then just chastizing you because of a bad description.

You soaked in HCL + heat for alittle while but did not drain off the tin, lead, etc.? Why not? If there is tin in solution, wont it effect gold? No clue how much solder being in there it might be a problem. Should not be the only problem as you tested positive. So gold is there.

Mistaken peroxide for nitric is a lableing problem. But should not effect the process, I could be wrong but doubt it.

Maybe you added more nitric and not enough HCL? Always keep an eye on the 4-1 guide.
Allowed enough time between nitric additions? Could be why there's too much nitric in the first place. Maybe add heat before nitric.

You let sit overnight. Did you test solution before adding more nitric?
If negative at this point, I would have poured off for disposal and started fresh.
My thinking, rid the base metals before dissolving gold.

Did you let the Stannous test sit for a few minutes to see if it changed indication free nitric? Added heat to finish reaction, lead still hiding, start denoxing?

It appears to me, not well versed at the whole process, but seems you have alot of excess nitric causing the problem.

You added way to much SMB at once. Drop alittle in and watch would have dropped something or nothing. Caused a reaction which would indicate if ready to drop or not. oops, more nitric so add alittle sulfamic acid and heat and wait.

SMB will drop gold but if there is free nitric with HCL, it will redissolve gold. "Nothing happened but brown foams(fumes?) appeared."
I'm guessing... The bown foam is SMB dropping gold(brown) and nitric is redissolving just as fast. Brown "fumes" would be nitric acid fumes. Could have both here.

My solution would be to let sit on high heat but not a boil, all the way down like in "Hoke's book", not "Hook" as I've seen. If you have free nitric acid, you need to rid the solution of water before nitric will come out. Impatient? Add more gold and heat. Then test again with small amount in a test tube with SMB. See if anything drops or just foams.

I follow the process in my mind to see if I can find flaws or possible problems. Helps me learn as well as help.

Let us know as well as point out anything I'm wrong with.

B.S.

 

[Anonymous]

I would ask why bother with the HCl wash at the beginning?

Those are high grade ceramics, just put them straight in your AR. The chances of tin forming that sticky goo from this product is extremely slight if at all. I've certainly never had a problem with it when processing exactly the same product as this.

Don't go 4:1 at the beginning. With the bulk of these processors with the pins on, you'll have far too much Nitric in the solution if you cover with HCl then add Nitric to that ratio.

3lbs of ceramics like this aren't going to net you a huge amount of gold- personally I'd search on the forum for the calculator of how much nitric is required for 5g of gold and use that amount initially. Only adding more if the reaction comes to a dead stop with visible pins remaining. Your visual reading of when the reaction is finished is simple - nothing happening and all the pins and metal have disappeared. If there is metal left- then you haven't completed it.

Using little amounts of Nitric will save you a lot of grief until you learn from experience how much to be using, and this topic is covered on countless threads and posts all over GRF. Sulfamic and getting rid of the excess nitric is another post entirely and I would recommend you read up on but if you follow what I've said here then your problems with excess Nitric will be substantially lessened.

I hope this helps, and sorry if I seemed brusque earlier on, but you can imagine what would be said to a newbie on this forum who did it like this, let alone a 5 year vet.

Regards

Jon

 

[goldsilverpro]

A liter of AR will dissolve a little over 1/2 pound of base metals. 97g of sulfamic will neutralize about 63ml of 70% nitric.

The best indicator for completion of those particular parts is, after rinsing a few, to gently use a small plastic or metal probe and see if the chip pieces will slide around freely on the pad - after the gold braze is gone, the chips will hold to the pad by surface tension, but they will slide. Don't force the chips. The gold braze under the chip (or, piece of chip) will be the last thing to dissolve. If there is any remaining, the chip will not easily slide around.

For this reason, I like them broken up a bit so the chip is in 3 to 4 pieces. If you pulverize them, the sliding test won't really work and this makes it harder to tell if everything is dissolved. Sometimes, this takes all day under heat. It would probably be easy to break out the chip areas and do them separately.

A guy I knew ran about 40-50 pounds (whole, not broken up nor de-lided) at a time. He used a plastic tank and pre-mixed AR cut with about 40% tap water. He had done this enough to know approximately how much acids to use. I'm thinking he had a couple of immersion heaters. It didn't get real hot. Little less fumes. It took about 3-4 days. The guy then filtered and dropped the gold with SO2 gas. Sometimes it took awhile to start dropping, but it always dropped, all of it. Always needed re-refined, but that goes fast.

I have done tons of these (and Kovar TO5's, TO18's) in very hot dilute nitric first, using 304 SS containers. In my experience, Kovar will dissolve faster in a weaker hot nitric. I used to use about 40%, by volume. It might take 1 to 2, 8hr days. Then, after rinsing out most of the nitric, you just soak the parts in some warm AR (maybe dilute, even) to dissolve the gold - works fast. Less AR to deal with. Cleaner gold the first time. Essentially, little, or no more acid is used than when using AR direct. Time about the same, maybe a little more.

I don't mind if it takes 4 days, +/-. It doesn't take much labor and I have peace of mind that I get it all.

 

[Anonymous]

Dang- thanks GSP I forgot to factor in the base metals in the equation.

 

[kjavanb123]

All,

Thanks for your comments. To my surprise this morning as I was decanting the AR solution, I noticed a layer of light brownish residue under what seems like silver chloride, here is what it looks like;



I dissolved it in hydrochlroic acid, then add nitric and it turned out to be gold along with yellowish tint residue which was not dissolving, tested postitve with stannous chlroide, so I precipitated the gold powder added 7 grams of SMB before gold precipitates AR solution was so concentrated or hot? that gold crystals showed on top of solution.


So thanks again and will post updates
Kevin

 

[Anonymous]

I dissolved it in hydrochlroic acid, then add nitric and it turned out to be gold along with yellowish tint residue which was not dissolving, tested postitve with stannous chlroide, so I precipitated the gold powder added 7 grams of SMB before gold precipitates AR solution was so concentrated or hot? that gold crystals showed on top of solution.

Kevin

I know English isn't your first language Kevin so could you please explain this part step by step please?

 

[kjavanb123]

Sorry about that, but I was so excited to find the missing gold in my solution, after decanting the AR solution, I noticed a layer of white-yellowish precipitant, underneth of it the light brown powder seen in previous post, which I suspected to be the missing gold, I dissolved the whole thing, white powder and light brown powder in hot hydrochloric acid, then drop a few ml of nitric and reaction started and dissolved the brown powder and left the white powder untouched, filtered, checked the solution which obviously had the orange color, and turned positive for gold and very concentrated, As dropped with SMB, gold leaves appeared on the surface of solution as you can also see in the second photo of my last post.

Hope this explained it for you.

Regards
Kevin

 

[DANCER]

Sulfamic acid turns nitrites to nitrogen gas and nitric acid to N2O (laughing gas) but I believe that stable nitrates are slow to react with it at room temperatures and therefore heating is necessary to insure the complete reaction.