how much gold is in cpu's?

[lazersteve]

I've checked the method you mentioned and have a few questions.

Break the cpus into a few pieces (no need to fully grind) before processing via Modified Poorman's AR.

1. Do you mean prior to removing the lids (1st step in MPAR method) or instead of or after?

The cpus usually break into a few pieces when you remove the lid. If they don't, break them into two or three pieces.

2. After crushing with which parts will MPAR take care of from the following:

i, surface gold in the exposed cores, wiring, and pins
ii, gold on the plated lids
iii, gold in the ceramic cores in the form of hair fine wires.
iv, gold in the gold alloy solder holding on the lids

I process the gold plated lids separately, everything else gets dissolved at the same time. This is clearly stated at the bottom of the original list.

3. Step 9 confuses me a bit:

9. If salts form pour off dark acid through tight filter and start at step 3 above. Filter may contain gold foils or powder.

This step is after you added soduim nitrate, so at this stage of the process there is already gold dissolved in the solution, why to pour it off?

This process is actually more like using small doses of nitric acid to dissolve the base metals than it is like AR at this point. The gold is pushed out of solution by the copper saturation. Always stannous chloride test to be sure there is no gold in solution at this stage. You pour off the solution as it is saturated (dark chocolate to black oil colored) with base metals and needs to be replenished with fresh acid. Let it cool to room temperature and white/gray crystals will form that will keep the gold powder at the bottom and none will end up in the filter or the solution at this stage. Rinse the crystals out of the gold powder before adding more HCl in the next cycle.

4. The same thing concerns me at step 13:

13. Repeat steps 9 and 10 two more times.

Why include step 9 to repeat? It is a decision making step and if there is salt at step 13, following your steps one would pour the dissolved Au. Am I missing something?

You missed the fact that solutions saturated with base metals will not dissolve gold. The controlled additions of nitrate release HNO3 into the solution very slowly and forms a mild nitric acid which attacks the base metals. The nitrate is quickly displaced by the abundant chlorine from HCl and works to dissolve the base metals into solution until it saturates.

5. The step 19 is the following:

19. Repeat steps 15 and 16 two more times.

But step 15 is:

15. Filter through packed funnel under vacuum until 100% free of sediment and suspended particles.

Why filter out the gold powder? At this stage of the process Au is in powder format. If I filtered it and added SMB to the remaining solution, I would dispose the bulk of the gold. Or did you mean: "Repeat steps 16 and 17" - that would make more sense to me, but I am complete noob here.

It's actually supposed to be 17 and 18, I fixed it. I also fixed the next loop below it. The problem occurred when I added a few extra steps at the top and did not correct the repeating steps at the bottom. Sorry for the typo.

6. Step 25 is:

25. Transfer incinerated powder to beaker and repeat process steps 3 to 21 on the brown powder.

Do we supposed to really do each step with the gold powder? Why to add Soduim Nitrate? SMB? We already have the gold in powder format, there is no solution to get more from!

This is called the second refining and is included to bring your gold purity up to 9995+. If you omit this step your gold powder will be of inferior quality and when you melt it, the gold will be discolored and/or form a black crust when it cools.

I hope I won't upset you with my questions, maybe other newbies can learn from your answers as well.

No biggie, I needed to fix a few of the repeating steps anyway obviously.

Steve