If you don't want to read the entire post, my questions are in bold.
I am hoping someone could shed some light on a few questions I have.
Quite a ways back, I tried to reclaim a little gold from gold plated copper items and other iron based metals that consisted of pins, fingers, CPUs, transistors, etc. I subjected the material to a severe case of smashing and crushing in an attempt to provide maximum surface area for the subsequent processes to act upon it.
Following the pulverization of the material, nitric acid was added and allowed to react until no further action was observed, when the liquid was decanted off and a bit more nitric was added to the solids. At that point, I added aqua regia (AR) to the solids and began dissolving the gold and other left over base metals. After it appeared that everything had dissolved, I tested the solution using my stannous chloride test solution, and it immediately turned a black color with the fringes of the test spot being purplish, indicating there was gold in solution. I noticed when I added a few more pins and fingers, the gold was still dissolving, so I added a whole bunch more material. Why? Not quite sure why I added a whole bunch more material.
That was a mistake, because I ran out of nitric acid in the solution and didn’t have anymore on my shelf. I ended up with a mess of half dissolved base metals, dark brown/green solution, thick sludge (like mud), plastic floaters, and on and on. When I tested the liquid, no gold was in solution anymore. I had just made the batch of testing solution earlier in the day, and although I didn’t have any standard solutions, per se, I had some auric chloride (unknown purity) that someone gave to me that I used to mess around with. So my testing solution was good. With my tail between my legs, I put the liquids and muck into a container labeled “screwed up AR batch” and forgot about it.
Later, I decided to reprocess the material and the first thing I did was decant off the liquids, since everything had settled nicely. Knowing I still had HCL in the solution, I figured I may as well dissolve the whole mess using AR, cement out the gold using copper and the refine the gold from there. Since I didn’t have any nitrate to make nitric, I used a some NaNO2 (sodium nitrite) to make NOx that I bubbled through two, 3+ feet long, 3-inch inner diameter PVC scrubbers I made. Each scrubber column contained just under 4 liters of water with some 35% peroxide added. Needless to say, my reactions are always done under pressure, so I can force the gases generated through the scrubbers at about 1 psi and a flow rate of 3 to 5 liters per minute.
Question: How much NOx can I dissolve into water at 1 psi at a temperature ranging from 0 C up to 20 C (32F – 68 F). I assume it is a linear relationship. I have been looking for this info, but can not seem to be able to figure out what maximum concentration nitric acid I could expect from using this method.
The reason I am asking this is that, apparently the resultant liquid in the scrubber, or as I call it, the “scrubbant” (a word made up by me), is much stronger than I thought it was.
So getting back to reprocessing, after I thought I had dissolved everything that would dissolve in the AR, I tested the solution and confirmed there was gold in it. I added some sulfuric acid to be able to drop-out the lead, filtered and decided to cement out the gold using copper. Upon slightly heating the solution with copper wire in it, the solution began to vigorously boil and fume and all of the copper wire dissolved. So I added more copper wire. Then suddenly, the reaction stopped and by now the solution was a dark green-blue with brown (not blue-green) color. When I say suddenly, I mean in under a minute. I let it sit with excess copper wire in it overnight. The next day, I had pulled out some of the copper wire and it was covered with light tan colored crystals. I put some of the crystal covered copper wire into a small container, added hot water, and shook it vigorously. The majority of the crystals fell off of the wire and settled at the bottom of the container and didn’t appear to dissolve. The decanted liquid did not show the presence of gold in it (using test solution).
I then added several drops of concentrated HCL, and heated it slightly and quite a bit of the light tan crystals dissolved, turning the solution a brown color. For the sake of completeness, I tested the resultant liquid; the spot went from brown to clear, but no gold.
A test of the main solution (dark green-blue solution) changed the green-blue spot to a light brown color that eventually dried to a yellow (with a slight hint of green) color. It did not appear to indicate the presence of gold.
Question: I thought that based on the reactivity series that copper would cement out any metal below it, Ag (although not in this case), Hg, Au, Pt, etc. With respect to the light tan crystals, what is it most likely? Tin?
Pouring off the main solution resulted in only light tan crystals at the bottom that I subsequently dissolved in HCL. Little, if any brown sediment remained. I assumed this was the gold, but have yet to do anything with the main solution, muck and sediment. Recently, I was thinking about throwing the whole mess, minus the very little brown sediment, back into one container and dropping everything with Al, and either trying again or recycling the copper et al dropped by the Al. Anyway, I thought I would tell an amusing story and see if anyone could answer my couple questions above.
I am sure many other questions will be asked of me, but the above is generally what I had in my notes that I kept.
I am hoping someone could shed some light on a few questions I have.
Quite a ways back, I tried to reclaim a little gold from gold plated copper items and other iron based metals that consisted of pins, fingers, CPUs, transistors, etc. I subjected the material to a severe case of smashing and crushing in an attempt to provide maximum surface area for the subsequent processes to act upon it.
Following the pulverization of the material, nitric acid was added and allowed to react until no further action was observed, when the liquid was decanted off and a bit more nitric was added to the solids. At that point, I added aqua regia (AR) to the solids and began dissolving the gold and other left over base metals. After it appeared that everything had dissolved, I tested the solution using my stannous chloride test solution, and it immediately turned a black color with the fringes of the test spot being purplish, indicating there was gold in solution. I noticed when I added a few more pins and fingers, the gold was still dissolving, so I added a whole bunch more material. Why? Not quite sure why I added a whole bunch more material.
That was a mistake, because I ran out of nitric acid in the solution and didn’t have anymore on my shelf. I ended up with a mess of half dissolved base metals, dark brown/green solution, thick sludge (like mud), plastic floaters, and on and on. When I tested the liquid, no gold was in solution anymore. I had just made the batch of testing solution earlier in the day, and although I didn’t have any standard solutions, per se, I had some auric chloride (unknown purity) that someone gave to me that I used to mess around with. So my testing solution was good. With my tail between my legs, I put the liquids and muck into a container labeled “screwed up AR batch” and forgot about it.
Later, I decided to reprocess the material and the first thing I did was decant off the liquids, since everything had settled nicely. Knowing I still had HCL in the solution, I figured I may as well dissolve the whole mess using AR, cement out the gold using copper and the refine the gold from there. Since I didn’t have any nitrate to make nitric, I used a some NaNO2 (sodium nitrite) to make NOx that I bubbled through two, 3+ feet long, 3-inch inner diameter PVC scrubbers I made. Each scrubber column contained just under 4 liters of water with some 35% peroxide added. Needless to say, my reactions are always done under pressure, so I can force the gases generated through the scrubbers at about 1 psi and a flow rate of 3 to 5 liters per minute.
Question: How much NOx can I dissolve into water at 1 psi at a temperature ranging from 0 C up to 20 C (32F – 68 F). I assume it is a linear relationship. I have been looking for this info, but can not seem to be able to figure out what maximum concentration nitric acid I could expect from using this method.
The reason I am asking this is that, apparently the resultant liquid in the scrubber, or as I call it, the “scrubbant” (a word made up by me), is much stronger than I thought it was.
So getting back to reprocessing, after I thought I had dissolved everything that would dissolve in the AR, I tested the solution and confirmed there was gold in it. I added some sulfuric acid to be able to drop-out the lead, filtered and decided to cement out the gold using copper. Upon slightly heating the solution with copper wire in it, the solution began to vigorously boil and fume and all of the copper wire dissolved. So I added more copper wire. Then suddenly, the reaction stopped and by now the solution was a dark green-blue with brown (not blue-green) color. When I say suddenly, I mean in under a minute. I let it sit with excess copper wire in it overnight. The next day, I had pulled out some of the copper wire and it was covered with light tan colored crystals. I put some of the crystal covered copper wire into a small container, added hot water, and shook it vigorously. The majority of the crystals fell off of the wire and settled at the bottom of the container and didn’t appear to dissolve. The decanted liquid did not show the presence of gold in it (using test solution).
I then added several drops of concentrated HCL, and heated it slightly and quite a bit of the light tan crystals dissolved, turning the solution a brown color. For the sake of completeness, I tested the resultant liquid; the spot went from brown to clear, but no gold.
A test of the main solution (dark green-blue solution) changed the green-blue spot to a light brown color that eventually dried to a yellow (with a slight hint of green) color. It did not appear to indicate the presence of gold.
Question: I thought that based on the reactivity series that copper would cement out any metal below it, Ag (although not in this case), Hg, Au, Pt, etc. With respect to the light tan crystals, what is it most likely? Tin?
Pouring off the main solution resulted in only light tan crystals at the bottom that I subsequently dissolved in HCL. Little, if any brown sediment remained. I assumed this was the gold, but have yet to do anything with the main solution, muck and sediment. Recently, I was thinking about throwing the whole mess, minus the very little brown sediment, back into one container and dropping everything with Al, and either trying again or recycling the copper et al dropped by the Al. Anyway, I thought I would tell an amusing story and see if anyone could answer my couple questions above.
I am sure many other questions will be asked of me, but the above is generally what I had in my notes that I kept.