Sulfamic Acid Reaction

[yellowfoil]

Dear friends,

I recently processed 75 gm of ceramic oscillators, which I was collecting
for years and it was my first refining attempt after long study, watching
YouTube clips and reading whatever I could about this subject.

First I decided to clean them in CuCl2 solution, because I am processing
gold plated fingers and have active solution readily available. Please don’t
comment on this decision, because I am aware of opinion some refiners
have about this step, unless it is connected to the problem. I ended up
with nice and clean oscillators free of steel and tin.

Then I poured about 150ml of HCl into glass vessel with oscillators
and carefully added HNO3 little by little, all together about 2 ml.
Didn’t see too much reaction so I heated it up on the burner. When
it got warm, liquid was turning yellow and everything was looking
normal. So after about an hour, I turned the burner off and left it to cool.
When I got back, I was surprised. Liquid turned cloudy and looked like
orange juice. After some filtering and decanting I got clear yellowish liquid
so I tried to denox it with sulfamic acid (purchased in Home Depot)
and to my surprise I didn’t see any reaction. Crystals of sulfamic acid didn’t
even dissolve at all. So I thought ok, no HNO3 left, there must be more gold
in oscillators and I will process them again. Then I filtered sulfamic acid
crystals out of the pregnant liquid and added smb. After some fizzling I
didn’t see any change so I added more smb and finally I saw some kind of
drop. I had to add more smb than I expected and didn’t see any NO2.

Second processing turned out even weirder than first. I used about 100ml
of HCl, then added about 2 ml of HNO3. After heating, liquid turned
yellowish again. Then decanting and sulfamic acid but no reaction to
sulfamic at all, so this time I was getting suspicious and started to add smb.
There was a lot of brown gas coming out but no drop. Obviously, there must
be a problem with sulfamic acid. I got upset and added a lot of smb. There
was a lot of NO2 coming out of liquid, it was losing yellow color, but no drop.
On the end the liquid looked like water. I think that there was no gold left
on oscillators and the yellow color was just some kind of chemical reaction.
Next day I mixed remaining liquids with intention to add it to waste pot
and two days later I noticed additional (not significant) sediment at the
bottom of the beaker. I think that the drop from first run was so fine that
it didn’t settle over night. Now the liquid looks really clear.

Now the question is, what is wrong with sulfamic acid I have. Crystals look
same as I purchase it few years back. Do you have any idea why sulfamic
acid wouldn’t work in this case? If additional info is needed, please let me
know. Thanks for any help or advise you may have, because I am afraid to
do any additional refining and I have un ounce of foils and two pounds of
concentrates with bonding wires to do. I didn't include pictures from the
second run. Picture with ruler and little gold bead has 1 mm divisions.


Cheers, Yellowfoil.

 

[nickvc]

Sulfamic reacts better when the solution is hot but beware if boil overs so add when warm and slowly.
If you want to test your sulphamic simply make a small amount of AR and then add your sulfamic, if you get no reaction it is not what you thought, wastes some acids but better than losing your gold.

 

[yellowfoil]

Thanks Nickvc for the reply.

I purchased this sulfamic acid I used at Home Depot. Big building supply
store. It was listed at the label of the container, so I would expect it to
be truth. There was plenty of HNO3 in the second run and this so called
sulfamic acid didn’t do absolutely nothing. Could there be another reason?
For sure I will revisit Home Depot once more to make sure that there is
what it says.

Any Idea what is that yellow precipitate?

 

[Geo]

You were using it incorrectly. The solution needs to be hot. Like Nick said, it will easily boil over so be careful.

 

[yellowfoil]

Thanks Geo.

I will try, but it will be a while before I will do any refining, because
I am away now. In the mean time, do you think that sulfamic acid will
not produce single bubble, when the solution is at room temperature?

Does anybody have any idea what is that yellow perticipation?

Thanks again.

 

[philddreamer]

Like Geo stated, hot solution is best...
but I've used the sulfamic acid when the solution was cold and it worked accordingly.

As to the yellow precipitate, it might be tungsten precipitation...
processed ceramic cpu

Take care!

Phil

 

[yellowfoil]

Thank you Philddreamer.

I had feeling that sulfamic acid was supposed to do at least something
when added to room temperature solution. So the corporate must be
the material, which is supposed to be sulfamic acid and probably is not.
It is very annoying for the first time refiner, after so much studying
(ten years) to encounter so basic problem. I am very aware of
limitation of my knowledge, but didn’t expect this. Is there a way
to test sulfamic acid somehow? I don’t want to buy something
which is not what it is suppose to be again.

The link you suggested was very helpful in an ocean of knowledge. The
sediment I got was first canary yellow and then it turned greenish, same
as in the link. As you mentioned, probably tungsten.

Thanks again, Yellowfoil.

 

[etack]

I've been doing a lot of Revers AR on a job lately. I have found the the sulfamic acid works best when your solution is cold as an aqueous solution.

Eric

 

[g_axelsson]

Nick described how you could test your sulfamic acid.

Göran

 

[yellowfoil]

Hi Goran.

I was away and was trying to get as much information as I could
in meantime. Now I am back so I will try it today. Theoretically,
it was already tested, when I was denoxing my first and second
solution, but it wasn’t pure. I will try as an aqueous solution with
pure AR. Good point, appreciate it.

I purchased another sulfamic acid few days back, but by the sound
of crystals, it is not too fresh eider.

Thanks, Yellwfoil.

 

[Topher_osAUrus]

I always dissolve my sulfamic in water, then its irrelevant whether the AR is hot or cold, the reaction will happen. It just happens less evidently when cold. -which isn't a bad thing, no brown cloud. I just let it sit a day or two then proceed.

The cloudy white stuff is tungston.

I do wonder though, where as the piezo electric disc gone? Is it attributing to some of the cloud? No clue! Some of those look like they have a die in the middle of them, so maybe they were txco's that were insanely high frequency overtone oscillators or something.. i dont know, just a curiosity thats making some gears turn and send smoke signals.

To be honest, I am shocked that you got that much gold from that little amount of oscillators. Its rather impressive, actually.
Nice work

 

[yellowfoil]

Thanks for your comment Topher, good info to consider.

Weight of my first little speck of gold is 0.27g, but the total
yield is more. In addition, I have another very fine drop on
the bottom of the bicker, after days of settling and few very
small specks of gold left in the melting dish (see photos).
Yellow sediment, after original digestion, I think was
tungsten and some gold could have been trapped there as
well. So the estimate is another 0.05 – 0.08g in addition
to the weight of the button I have. The yield is so good
because each steel lid is gold soldered to the base of
oscillator, in addition to gold plating and gold bonding
wires inside. Not bad for 72 gm of original material. I had
suspicion that these oscillators are reach.


Few days back I did experiment with sulfamic acid, to see
what is actually suppose to happen. I mixed 7ml of HCl and
2ml of HNO3 in little ceramic cup. Then I dropped in about
0.2g button melted from foils from gold plated fiberglass
bases I peeled off of bga chips. Button was about 35% copper.
After some heating, reaction started and when the gold
button was almost digested, I added little of sulfamic acid
dissolved in lukewarm water and reaction stopped almost
immediately. So I would assume that it neutralized HNO3.
To my surprise, I didn’t see any kind of reaction with
sulfamic acid. None. After that I added little SMB and nice
greenish liquid turned blue. Shortly after that there was
brownish sediment at the bottom. So it is working after all
but how should I know, how much acid to add, when I don’t
see any kind of reaction? Is it normal that there is no visible
reaction to sulfamic acid?

Thanks everyone for good advice, it was very helpful.

Yellowfoil.

 

[nickvc]

You get a much more vigorous reaction when you have a high excess of free nitric which with some materials is unavoidable, with careful use of nitric or nitrates you shouldn’t have too much of an excess so the reaction is almost invisible unless your solution is hot, be careful with the sulphamic as it creates sulphuric acid which can and do eat your filter papers especially if using vacuum filtering, don’t ask me how I know this :evil:

 

[Geo]

As a last resort, if you can't get the solution denoxxed correctly, drop all the metal with small pieces of aluminum foil. It's cheap, it's easy and pretty much fool-proof but I'm sure someone will prove me wrong. Tear small strips of aluminum foil in about half gram pieces. Don't ball or crumple. Add the aluminum one piece at a time while stirring. Only add two or three pieces at a time or it could boil over. It should only take a few grams to drop all of the metal depending on how much free nitric is in the solution. It is finished when the solution loses all color except for a slightly blueish tint. The last bit of blue color will not cement out of solution. It should be nickel and is only important in large quantities. Filter and redissolve the solids in AR using the least amount of nitric acid in the AR needed to dissolve the metal.

 

[yellowfoil]

Hi Geo. Good to know another way out of problematic situation. I watched YouTube video about refining these oscillators just recently and the yield was much better than I got. 0.7g from 50g of material, which makes much more sense just by looking at the oscillators after CUCl2 treatment. I think I lost about 0.6g of gold in a process I expected to be strait forward. Warm weather is coming, so I will try to refine all foils I collected after years of finger processing in CUCl2. Thanks for your kind advice.

 

[Geo]

As an aside and to give more information, nitric acid in solution decomposes at 250°F. The solution can be brought to a temperature greater than 250°F and the free nitric acid will decompose and leave the solution as red NO2. The solution alone with no material involve will make tiny bubbles that resembles a reaction where metal is dissolving. Once the temperature is obtained, leave the solution covered or uncovered. If left uncovered, be sure to keep checking it periodically to make sure the solution does not boil dry. Eventually, the reaction will stop producing bubbles and the solution will be hot but placid. The free nitric acid will have been driven out of solution. It takes time. Much more time than using sulfamic acid but it is sure to remove the free nitric acid.