I did my first small scale gold recovery experiment over the weekend. Things went as planned so I was quite happy about that. I made a few pages of notes so I will try to summarize and include the important information.
I started with 3.08 grams of 10k jewelry. I bought 2 small melting dishes and glazed them with borax, without breaking them I might add
I inquarted with 2.01 grams of coin silver and poured the melt into water. It made 2 shot, a big one and a little one. Starting weight was 5.08g with expected gold content of 1.28g.
For the digestion I used a 50ml beaker with cover, hot plate, coffee pot with sand as a catch basin, distilled water, and 67% HNO3. Using a pipette I added 20ml water. More than I wanted but enough to cover the gold. Then 3ml HNO3. A dilute solution for sure but I figured 6 or 7 for digestion of the base metals so I started slow. I set everything up on the hot plate and turn to med-low. Over the next 2 hours the heat went to medium, I added 30ml water to keep everything covered. The reaction became vigorous after a slow start and the solution turned blue. I decanted and rinsed 3 times with water.
The second digestion consisted of 30ml water, 3ml HNO3, and heat. Over the next 2 hours I added 10ml water and 7ml HNO3 (3ml, 2ml, 2ml). The reaction was vigorous. Saw the red cloud in the covered beaker for the first time. Decanted and rinsed.
3rd digestion, 15ml water, 5ml HNO3, and heat. After 45 minutes the solution was just a very light blue, not deep blue like earlier. This told me the base metals were essentially gone. Decant into a separate container and rinse 3 times.
This morning the dry weight of the gold is 1.27g which is spot on expectations. I used 15ml of HNO3, double what I calculated. Is this because I need more water than expected to cover the material? The only other difficulty I had was determining when the bubbling observed was due to the acid or heat. I am still unsure.
Aqua Regia will be next but that will be for another post.
This site has a amazing volume of information but being the noob I am I can say the best piece of information is go slow. I would rather succeed with a small amount than blunder a large one. I would appreciate any comments. I think all the math is right. Are there any glaring examples of noob mistakes? :lol:
I started with 3.08 grams of 10k jewelry. I bought 2 small melting dishes and glazed them with borax, without breaking them I might add
I inquarted with 2.01 grams of coin silver and poured the melt into water. It made 2 shot, a big one and a little one. Starting weight was 5.08g with expected gold content of 1.28g.For the digestion I used a 50ml beaker with cover, hot plate, coffee pot with sand as a catch basin, distilled water, and 67% HNO3. Using a pipette I added 20ml water. More than I wanted but enough to cover the gold. Then 3ml HNO3. A dilute solution for sure but I figured 6 or 7 for digestion of the base metals so I started slow. I set everything up on the hot plate and turn to med-low. Over the next 2 hours the heat went to medium, I added 30ml water to keep everything covered. The reaction became vigorous after a slow start and the solution turned blue. I decanted and rinsed 3 times with water.
The second digestion consisted of 30ml water, 3ml HNO3, and heat. Over the next 2 hours I added 10ml water and 7ml HNO3 (3ml, 2ml, 2ml). The reaction was vigorous. Saw the red cloud in the covered beaker for the first time. Decanted and rinsed.
3rd digestion, 15ml water, 5ml HNO3, and heat. After 45 minutes the solution was just a very light blue, not deep blue like earlier. This told me the base metals were essentially gone. Decant into a separate container and rinse 3 times.
This morning the dry weight of the gold is 1.27g which is spot on expectations. I used 15ml of HNO3, double what I calculated. Is this because I need more water than expected to cover the material? The only other difficulty I had was determining when the bubbling observed was due to the acid or heat. I am still unsure.
Aqua Regia will be next but that will be for another post.
This site has a amazing volume of information but being the noob I am I can say the best piece of information is go slow. I would rather succeed with a small amount than blunder a large one. I would appreciate any comments. I think all the math is right. Are there any glaring examples of noob mistakes? :lol:
