Aqua Regia method with 12-13% Ag _inquart_

[giahylxag]

I am testing my fume scrubber today!
I tested it by boiling tin in HCL to make stannous cloride.
Usually this reaction gives a lot of white smoke with nasty fume.
But sent though the scrubber only a little white smoke came out with barely any smell (I didn't try in inhale alot of it).
Then came to the question.
How can you test if the fume is safe to release?
I used a small litmus paper, gave it some humidity, turned green, raised it to the opening, and waited for how long for it to turn red.
It took me about 30 seconds to turn red. Is the fume safe to release?

 

[giahylxag]

@4metals @Yggdrasil
Any help would be really appreciated!
Sorry to botherboth of you

 

[Yggdrasil]

@4metals @Yggdrasil
Any help would be really appreciated!
Sorry to botherboth of you

Have some patience!
We do not sit here online all the time to answer any question served.
There should really not come any fumes from the outlet of the scrubber.
When that is said HCl is not a good tester, better use something else.
White fumes may also be water.
Can you specify how you made it and what liquid you are using for the scrubbing?

 

[Yggdrasil]

@4metals @Yggdrasil
Any help would be really appreciated!
Sorry to botherboth of you

To check, take a moist pH paper and hold it in the outlet for awhile and see if any acidic fumes escape.

 

[4metals]

The fume scrubber is a function of contact of the fume with retention time in the scrubber. For effective NOx scrubbing 8 seconds of retention time in the scrubber is required. So we need to know the internal area of the packed section of the tower and do the math based on the airflow of the blower you are using to pull the fume through the scrubber. If you have an 8 second retention time the chemistry has time to function properly. The caustic use is dependant on the fume the scrubber reacts with so usually a pH controller is used to dose the caustic as needed to maintain a pH of 10.

The effectiveness of a scrubber is typically judged by eye, red fumes in, and clean fume out, usually clear but it may be white if weather conditions cause condensation. condensing steam breaks up in a few seconds out of the stack.

My responses to this will be delayed because I am on vacation in the Virgin Islands and only responding on a smartphone. Expected return 2/13. I don't expect much sympathy.

 

[giahylxag]

Have some patience!
We do not sit here online all the time to answer any question served.
There should really not come any fumes from the outlet of the scrubber.
When that is said HCl is not a good tester, better use something else.
White fumes may also be water.
Can you specify how you made it and what liquid you are using for the scrubbing?

I will take a picture of my scrubber cell tomorrow.
Basically it is a 9cm wide and 100cm long pvc pipe packed with plastic bio balls. It is so cheap to make so I can readily make another scrubber cell in a day.
I have a NaOH (20%) shower on the top of the pipe and the fume also come from the top of the pipe.

We do not sit here online all the time to answer any question served.

Because different in time zone (I am in East Asia) so there are only 1 or 2 hours to ask you before I go to sleep.
Really sorry if that bother you.

 

[giahylxag]

To check, take a moist pH paper and hold it in the outlet for awhile and see if any acidic fumes escape.

It took me 30 sec for the pH paper to turn red so I assume there is still some acidic fume. But 30 sec is enough for the fume to escape into the outside environment i think.

 

[Yggdrasil]

It took me 30 sec for the pH paper to turn red so I assume there is still some acidic fume. But 30 sec is enough for the fume to escape into the outside environment i think.

That means the scrubber don't do a full job.
Slower fan or better misting on the top is necessary.

 

[Yggdrasil]

I will take a picture of my scrubber cell tomorrow.
Basically it is a 9cm wide and 100cm long pvc pipe packed with plastic bio balls. It is so cheap to make so I can readily make another scrubber cell in a day.
I have a NaOH (20%) shower on the top of the pipe and the fume also come from the top of the pipe.

Because different in time zone (I am in East Asia) so there are only 1 or 2 hours to ask you before I go to sleep.
Really sorry if that bother you.

That is no problem you just need to give us time to reply.
I'm in Europe so I'm 6-7 hours behind you.
Where in East Asia are you?

 

[giahylxag]

That is no problem you just need to give us time to reply.
I'm in Europe so I'm 6-7 hours behind you.
Where in East Asia are you?

I am in Vietnam so GMT+7, it is 0:00 am here now

 

[Yggdrasil]

I am in Vietnam so GMT+7, it is 0:00 am here now

I lived in the Philippines for two years, came back in 2022

 

[giahylxag]

I lived in the Philippines for two years, came back in 2022

There will be a big holiday here so another 2 weeks delay, i just don't want to wait so I have to bother both of you. I have to say sorry again.
I will make another scrubber cell tomorrow, I will eliminate all the acidic fume this time.

 

[Muratthechemist]

Thank you for such detail explanation. What is the cons of inquarting? Inquarting method seems much easier, faster?, and seems more economy to refine gold than AR method.
Given most fashion jewelry comes with low %Au and higher %Ag, why AR still widely used?
I opened this thread to ask about AR but this made me rethink my approach.

As 4metals explained before, pawn shop or jewelery busines, you should give them gold or money very fast. Some customer wants 99.99 gold to make grams maybe.
In that option speed and time is very important. I am making aqua regia all the time for starting gold materials. where i work with regular jewelery is not lower than 14K mostly.
So, 2.5 hours is enough for the reaction and same day we give gold to client. If i do inquartation i cannot reach 99.99 purity in fast way. because it needs second dissolution and process silver, much silver.
300-200g is ok but think there is 50 kg so you have no option to go inquartation method.

For topic answer;

Regular mixing tumbler in closed systems also small pieces of titanium can help to dissolve 10% silver.
Whatever you do small gold will acumulate with your silver.
If is less is good.

Granulation is the key here. Flaking must be applied to starting step. granules takes more time and surface area doesnt help with covering silver chloride.

 

[giahylxag]

I want to share with everyone here my acid fume scrubber.
-Fan-
I use a big air ventilator fan, it produces almost no sound, the output is 34mm pipes to slow the air down when it pass through the scrubbers.
There is a secondary fan, very small but powerful, it produces a lot of noise so I only turn it on when there is alot of acid fume
-Scrubber cell-
I use a 114mm pvc pipe scale down to 27mm pipe at the bottom with a valve to control the liquid
The pvc pipes have a T-section in the middle so that I can guide the fume to another cell
-packing material-
I use bio balls
-liquid-
I use 15% NaOH liquid

 

[giahylxag]

This is my setup inquarting is a very straighforward method, there is a Nitric bottle behind

My %Au is 61%, I use copper to inquart so you can see the blue color

After a couple of diluted nitric boil the liquid is clear and to gold sponge turns dark coffee brown

I proceed with 3 times distilled water washs, 1 HCL wash, an another 3 times water wash
And this is my result
XRF result came 99.71 way better than what I expected

 

[4metals]

XRF result came 99.71 way better than what I expected

We at GRF will take this as a compliment!

The impurities are copper and silver as expected. I see the gold is stuck together and holds together nicely. The gold at this point should crumble with little effort. If you were to break up the pieces to smaller chunks, you may get even better penetration with the second parting acid as the acid can penetrate easier. A solid glass rod will effectively break up smaller lots.

If you want the best purity for your efforts refine once in aqua regia and do not melt it before you digest it in AR. It should digest very quickly.

 

[4metals]

This is my setup inquarting is a very straighforward method,

Now that you can compare the inquatation method and the aqua regia method for your high silver alloy which method do you prefer?

 

[giahylxag]

Now that you can compare the inquatation method and the aqua regia method for your high silver alloy which method do you prefer?

Sure inquarting is the way to go
Even my friend convinced when he saw the result

 

[giahylxag]

We at GRF will take this as a compliment!

The impurities are copper and silver as expected. I see the gold is stuck together and holds together nicely. The gold at this point should crumble with little effort. If you were to break up the pieces to smaller chunks, you may get even better penetration with the second parting acid as the acid can penetrate easier. A solid glass rod will effectively break up smaller lots.

If you want the best purity for your efforts refine once in aqua regia and do not melt it before you digest it in AR. It should digest very quickly.

I am currently having problem with fume. Althought I believe most of the fume are treated. Some still leak somewhere. I can smell it, not too much to bear but (the smell indicates it) there is still acid fume floating around.
The next day I see my PH papers on my desk turn light pink, there is still acid fume floating around.

 

[Yggdrasil]

I am currently having problem with fume. Althought I believe most of the fume are treated. Some still leak somewhere. I can smell it, not too much to bear but (the smell indicates it) there is still acid fume floating around.
The next day I see my PH papers on my desk turn light pink, there is still acid fume floating around.

How good is your suction?
Where is your exhausts?
Are you sure they are clean and not sucked back inside?
Add a moist litmus paper on each joint.