This is my first attempt at evaporating AR down to denox. Ive read to turn it into a syrup but how thick should this syrup be? Ive evaporated 8 cups down to 1 2/3 cup. When i swirl it sticks to the side of the container briefly. Should it be the consistency of hot syrup or cold syrup? Im evaporating at about 80C. Ive read if you take it to far crust will form and i dont want that. Thanks for any help.
-
Please join our new sister site dedicated to discussion of gold, silver, platinum, copper and palladium bar, coin, jewelry collecting/investing/storing/selling/buying. It would be greatly appreciated if you joined and help add a few new topics for new people to engage in.
Bullion.Forum
Non-Chemical Evaporation
- Thread starter Tylerb752
- Start date
Help Support Gold Refining Forum:
Reducing the volume of the dilute yellow solution through evaporation you will notice the solution turns to a reddish-orange gold chloride solution, of highly concentrated gold, you do not need to reduce it to salts, but concentrate the solution to a thicker solution, while the solution is still hot adding acid HCl to the solution will dilute it with the water involved in the acid, the acid will also reform nitric from any metal nitrate salts, which will decompose in the hot and concentrated solution to NOx gases (the deadly red cloud of gases), continuing heat to evaporate off the added acid (water) and reconcentrate the solution add acid again, evaporate and add acid for the third time and watch for gases as you heat the solution.
Normally by the third cycle of adding the acid and evaporation cycle, you will no longer see the red cloud of NOx gases.
sulfuric in the solution helps to precipitate lead, it also can help in the de-NOx-ing process to remove acids and gases that are more volatile than sulfuric acid is, it can also assist in helping you from cooking the metal salts too dry if you forget and evaporate the solution down too far...
Normally by the third cycle of adding the acid and evaporation cycle, you will no longer see the red cloud of NOx gases.
sulfuric in the solution helps to precipitate lead, it also can help in the de-NOx-ing process to remove acids and gases that are more volatile than sulfuric acid is, it can also assist in helping you from cooking the metal salts too dry if you forget and evaporate the solution down too far...
I am processing ic chips so my solution is not a gold color from remaining base metals left behind after my initial dikute nitric soak. I thought i had it all out but my solution was a green color. Testing it with stanous it does have gold. So my color change was from green to black. When i stir it the solution sticking to the sides of my evaporation container is a gold color.
My solution is definetly thicker then when i started but not the consistency of honey as ive read (i kept researching after i posted) it should be. However the sides of my container and my thermometer have a green coagulation on them.
I added sulfuric as per hokes specs.
At the consistency i have it at now when i add hcl no red fumes are released.
My solution is definetly thicker then when i started but not the consistency of honey as ive read (i kept researching after i posted) it should be. However the sides of my container and my thermometer have a green coagulation on them.
I added sulfuric as per hokes specs.
At the consistency i have it at now when i add hcl no red fumes are released.
The more base metals in solution the easier it would be to form salts when cooled...
But also with more base metals in solution with the gold the easier it is to form nitrate salts in solution...
All nitrate salts are decomposed by heat or strong acids, dilute H2SO4 to produce NOx gases, nitric oxide a colorless gas (that in moist air forms the reddish-brown fumes of nitrogen dioxide gas in the air), and the red NO2 gas nitrogen dioxide gas itself.
2Cu(NO3)2 (aq) + H2SO4 + Heat of evaporation --> 2CUO (aq) + 4NO2 (g) + O2
The more base metals like copper or other metals or ions such as sodium in solution along with your gold chloride solution, the easier it is for the nitric in solution to form nitrate salts, and the harder it will be to remove the nitric from solution as a gas. Metals like copper form nitrates or even sodium will form a nitrate salt, which can be evaporated to salts from a concentrated solution.
You can take a small sample of your concentrated salts in a test tube and test the sample with sulfuric over a heat source, to see if you get any red gases...
Working with a very small sample in the test tube will make evaporation and concentration on a small sample is easier in a test for the red gas, you could also use a spot plate and some a crystal of FeSO4 or some SMB, or use your stannous to verify the gold in the solution can be reduced with a reducing agent...
You can also try the brown ring test for nitrates in solution, when a freshly prepared solution of ferrous sulfate is added to a solution of nitrate ions, in the presence of concentrated sulfuric acid, a deep brown ring of iron in the +1 and +2 oxidized states will form. Even a small disturbance in the solution can disturb the complex formed, so for that reason, the acidified ferrous sulfate is added in dropwise with the drops rolling down the sides of the test tube so as not to disturb the solution as they mix at the surface and edge of the solution to form the complex of iron as a brown ring, although with gold precipitating as the brown powder the brown ring can be hard to distinguish, so you may not have much luck seeing it very well...
That and the fact that ferrous sulfate not only reduces the gold as a brown powder, it can help to de-NOx a solution as well, the brown in the test as a ring could be gold or the iron complex, so it will at least show you that you can reduce the gold...
But also with more base metals in solution with the gold the easier it is to form nitrate salts in solution...
All nitrate salts are decomposed by heat or strong acids, dilute H2SO4 to produce NOx gases, nitric oxide a colorless gas (that in moist air forms the reddish-brown fumes of nitrogen dioxide gas in the air), and the red NO2 gas nitrogen dioxide gas itself.
2Cu(NO3)2 (aq) + H2SO4 + Heat of evaporation --> 2CUO (aq) + 4NO2 (g) + O2
The more base metals like copper or other metals or ions such as sodium in solution along with your gold chloride solution, the easier it is for the nitric in solution to form nitrate salts, and the harder it will be to remove the nitric from solution as a gas. Metals like copper form nitrates or even sodium will form a nitrate salt, which can be evaporated to salts from a concentrated solution.
You can take a small sample of your concentrated salts in a test tube and test the sample with sulfuric over a heat source, to see if you get any red gases...
Working with a very small sample in the test tube will make evaporation and concentration on a small sample is easier in a test for the red gas, you could also use a spot plate and some a crystal of FeSO4 or some SMB, or use your stannous to verify the gold in the solution can be reduced with a reducing agent...
You can also try the brown ring test for nitrates in solution, when a freshly prepared solution of ferrous sulfate is added to a solution of nitrate ions, in the presence of concentrated sulfuric acid, a deep brown ring of iron in the +1 and +2 oxidized states will form. Even a small disturbance in the solution can disturb the complex formed, so for that reason, the acidified ferrous sulfate is added in dropwise with the drops rolling down the sides of the test tube so as not to disturb the solution as they mix at the surface and edge of the solution to form the complex of iron as a brown ring, although with gold precipitating as the brown powder the brown ring can be hard to distinguish, so you may not have much luck seeing it very well...
That and the fact that ferrous sulfate not only reduces the gold as a brown powder, it can help to de-NOx a solution as well, the brown in the test as a ring could be gold or the iron complex, so it will at least show you that you can reduce the gold...
Sulfamic acid will work very well to de-Nox a solution, it will also make H2SO4 in situ in solution adding to its benefits by helping to precipitate lead salts from the solution.
A trick we learned from Harold, adding a gold button and heat to De-NOx the solution, the gold adds nothing chemically to the solution but gold, and works very well to eliminate excess nitric acid, this is very similar to adding nitric in small increments while heating a solution to consume all of the added nitric acids before the next addition, and stopping adding nitric before all of the gold has gone into the solution and using heat to finish the process...
I will normally use a combination of all of the above methods we have discussed, for example using nitric cautiously, only adding it in small additions and using heat to consume the nitric, leaving some gold undissolved or adding gold were needed to consume the nitric, adding sulfamic acid, and using the heat of evaporation (with acid additions...
A trick we learned from Harold, adding a gold button and heat to De-NOx the solution, the gold adds nothing chemically to the solution but gold, and works very well to eliminate excess nitric acid, this is very similar to adding nitric in small increments while heating a solution to consume all of the added nitric acids before the next addition, and stopping adding nitric before all of the gold has gone into the solution and using heat to finish the process...
I will normally use a combination of all of the above methods we have discussed, for example using nitric cautiously, only adding it in small additions and using heat to consume the nitric, leaving some gold undissolved or adding gold were needed to consume the nitric, adding sulfamic acid, and using the heat of evaporation (with acid additions...
goldenchild
Well-known member
- Joined
- Aug 14, 2009
- Messages
- 1,810
Are you saying that you're evaporating your solutions that have base metals? You're not really supposed to do that. The evaporation technique is really for when you already have isolated your gold and digested it into gold chloride. The whole evaporation down to syrup and re hydrate with HCL to denox is antiquated however. I respect it because that's where it all started but there are far more efficient and faster ways to do it. Especially for larger quantities of solution. 8 cups down to less than 2 must have been painful.Urea or sulfamic acid are the way to go for denoxing. It's easy to see when you are totally denoxed and you can use it in both your base metal or gold solutions. Fast and easy.
Eight cups of gold chloride solution?
if you are using that much acid you must have a pound of gold in solution?
8cups x 8 fl oz/cup = 64 Fluid ounces of aqua regia.
When you can dissolve one toy ounce 31.103 grams of gold using only 5fl oz of aqua regia.
Here you are talking about easily having a pound of gold, 12 troy ounces, or 373.24 grams of gold dissolved in those 8 cups or 64 fluid ounces of liquid solution.
if you do not overuse acids there is no problem evaporating down the solution,.
8 tablespoons of HCL and 2 tablespoons of HNO3 will dissolve one troy ounce of gold.
120ml HCl and 30ml HNO3 (or 150 ml of aqua regia) will dissolve an ounce of gold.
One cup of a solution is about 240 ml of solution.
3.8ml HCl and 0,95ml HNO3(about 5ml of Agua Regia) will dissolve a gram of gold.
One US tablespoon full of aqua regia is about 14.7 ml of solution which you can easily dissolve more than two and a half grams of gold into this one spoonful of the solution, how long would it take to evaporate the excess nitric from a tablespoon of gold chloride holding over 2.5 grams of gold?
if you are using that much acid you must have a pound of gold in solution?
8cups x 8 fl oz/cup = 64 Fluid ounces of aqua regia.
When you can dissolve one toy ounce 31.103 grams of gold using only 5fl oz of aqua regia.
Here you are talking about easily having a pound of gold, 12 troy ounces, or 373.24 grams of gold dissolved in those 8 cups or 64 fluid ounces of liquid solution.
if you do not overuse acids there is no problem evaporating down the solution,.
8 tablespoons of HCL and 2 tablespoons of HNO3 will dissolve one troy ounce of gold.
120ml HCl and 30ml HNO3 (or 150 ml of aqua regia) will dissolve an ounce of gold.
One cup of a solution is about 240 ml of solution.
3.8ml HCl and 0,95ml HNO3(about 5ml of Agua Regia) will dissolve a gram of gold.
One US tablespoon full of aqua regia is about 14.7 ml of solution which you can easily dissolve more than two and a half grams of gold into this one spoonful of the solution, how long would it take to evaporate the excess nitric from a tablespoon of gold chloride holding over 2.5 grams of gold?
goldenchild
Well-known member
- Joined
- Aug 14, 2009
- Messages
- 1,810
"I am processing ic chips so my solution is not a gold color from remaining base metals left behind after my initial dikute nitric soak. I thought i had it all out but my solution was a green color. Testing it with stanous it does have gold. So my color change was from green to black."
I'm pretty sure he's talking about evaporating base metal solutions (with some gold in it). But we'll have to wait until he get's back on to confirm. Also, I was confused for a second until I realized you were talking about a troy pound. This is just for anyone that comes across this thread in the distant future. A pound is 453.59 grams. A TROY pound is 373.24 grams. 8)
I'm pretty sure he's talking about evaporating base metal solutions (with some gold in it). But we'll have to wait until he get's back on to confirm. Also, I was confused for a second until I realized you were talking about a troy pound. This is just for anyone that comes across this thread in the distant future. A pound is 453.59 grams. A TROY pound is 373.24 grams. 8)
