Question on expelling nitric with HCl

[samuldacamul]

Again another question:
I have once again attempted the poor man's AR process. This time I removed cpu lids and put lids and cpus in the HCl, and proceeded to heat. Just before it started boiling I added the sodium nitrate. I added more when the reaction stopped. After these steps, I let the solution evaporate down to a "thick syrup" or about 1/5 of its original volume. My question is, how much HCl should I add at this point to "expel the nitric as brown vapors?" When I added it, the soltion turned from a dark color, to yellow, but I saw no brown vapors. I took a small sample of this solution to atempt an SMB drop. When I added the SMB, the solution turned brownish red, but it went back to yellow with very little precipitation, along with salts.
I don't understand how HCl would expel the nitric anyway. What would the chemical equation be?
Thank you guys for the help. Also, the solution did test positive for gold before and after the attempted drop.

 

[Barren Realms 007]

Add the same amount of HCL your volume of solution started with to evaporate again. The HCL as far as I know is not expelling the nitric. the nitric is evaportaing off. I wouldn't boild your solution because you can loose values with the boiling. Just raise the temp to where you start to get vapors coming off the solution. Just because you don't see brown fumes does not mean you are not expelling the nitric.

 

[samuldacamul]

ok thank you. So once I add the HCl I should evaporate again? Also, if I further evaporate the solution I already added the SMB to, if I am thinking correct, as the nitric avaporates off, the gold should drop. Also, can I just use urea instead of all this evaporating?

 

[Barren Realms 007]

Yes exaporate the solution down 3 times addind HCL each time ig get's to a thick consistancy. The So2 gas that was produced by the SMB was expelled during the first use so you will need to add more.

 

[samuldacamul]

Alright I will definitely try this. A couple more things now haha sorry.
When you add the SMB, does it have a single replacement reaction with chloride ions to precipitate the chlorine? Also, I would think that even if you didn't get rid of the excess nitrate ions, if you added enough SMB you could get the solution to a point where there would be no more chloride ions to re-dissolve the gold.

 

[Barren Realms 007]

When you add SMB any residue of chlorine or nitric will try to redissolve your gold. If you add a lot of SMB to percipitate your gold it can give you more problems and create residue from the excess SMB. It is best to remove the chlorines or nitric.

 

[samuldacamul]

Ok I see what you are saying. So does adding urea work with the poor man's method?

 

[Barren Realms 007]

Yes it can. Warm your solution up and add small amount's or urea till you get no more reaction and then add some more. Just because you get no reaction does not mean you have it all out.

 

[samuldacamul]

Sweet. I would think that would be a lot easier than the evaporation method. Are there any fertilizers that work so I don't have to buy any online?

 

[Barren Realms 007]

Urea, it is a fertalizer. However if you have started down a path with your solution continue down that path. Do not switch things in the middles of your process.

 

[nickvc]

Urea, it is a fertalizer. However if you have started down a path with your solution continue down that path. Do not switch things in the middles of your process.

Wise words indeed!

 

[lazersteve]

I did not see a reference to any filtering or siphoning in your process, nor did I see any separation of the gold foils/powder from the dirty solution before it was dissolved.

Here's the poorman's AR process with whole cpus (less the lids):

Modified Poorman's AR Notes

The lids are easily and cleanly processes in the sulfuric acid stripping cell.

The kovar lids are notoriously difficult to dissolve and produce a lot of iron and nickle in the solution. These should be separated from the gold before dissolving the gold.

You also mention colored salts, these should be removed from the solids with hot water washes before any attempt is made to precipitate the gold.

I use poorman's AR everyday and never have to evaporate or use urea. The key is to be patient and add the nitrate in controlled increments so that there is not an excess of NOx (nitrogen oxides) left in the solution after the scrap is dissolved.

Bottom line, follow through will all of the steps in process, and choose a process to suit the scrap you are processing.

The equations for the reactions are here:

Gold Reaction Equations
Steve

 

[Barren Realms 007]

I did not see a reference to any filtering or siphoning in your process, nor did I see any separation of the gold foils/powder from the dirty solution before it was dissolved.

Here's the poorman's AR process with whole cpus (less the lids):

Modified Poorman's AR Notes

The lids are easily and cleanly processes in the sulfuric acid stripping cell.

The kovar lids are notoriously difficult to dissolve and produce a lot of iron and nickle in the solution. These should be separated from the gold before dissolving the gold.

You also mention colored salts, these should be removed from the solids with hot water washes before any attempt is made to precipitate the gold.

I use poorman's AR everyday and never have to evaporate or use urea. The key is to be patient and add the nitrate in controlled increments so that there is not an excess of NOx (nitrogen oxides) left in the solution after the scrap is dissolved.

Bottom line, follow through will all of the steps in process, and choose a process to suit the scrap you are processing.

The equations for the reactions are here:

Gold Reaction Equations
Steve

Things change when it is 30F outside like it is here now so it helps to be able to heat your solution up.

 

[lazersteve]

It's 42F here today and raining on and off.

I know some of the members are dealing with several feet of ice and snow today.

Steve

 

[Barren Realms 007]

Our rain passed a couple of hours ago but it windy with a wind chill probaly in the single didget's. Keeps blowing the flame on my fish cooker out so I have to keep check on it. Miserable weather to work in... :evil:

 

[samuldacamul]

Thank you for those words, Steve. And yes I have filtered the solution of salts before evaporation. Although since its like 20 degrees here and I have a busy life, I had to leave the solution over night. I woke up with a TON of salts which I also filtered and then continued to evaporate. I am using a large pyrex pan to increase surface area. I have evaporated 3 times completely. Is that enough?

 

[Barren Realms 007]

Thank you for those words, Steve. And yes I have filtered the solution of salts before evaporation. Although since its like 20 degrees here and I have a busy life, I had to leave the solution over night. I woke up with a TON of salts which I also filtered and then continued to evaporate. I am using a large pyrex pan to increase surface area. I have evaporated 3 times completely. Is that enough?

If you see no more brown fumes coming off the solution you should have it all out. You might want to put a top on it for a little bit and see if the air inside the container turns brown.

 

[samuldacamul]

ok. I actually never saw any brown fumes to begin with but i have a high power fan for my ventilation so it could just be because the vapors were never concentrated enough. good idea with the stopper