samuel-a
Well-known member
- Joined
- Oct 7, 2009
- Messages
- 2,190
Sucho said:lead iodide :lol: :lol:
machiavelli976 said:Great !
Is there a hot plate beneath the sand ?
samuel-a said:step wise for Oxalic acid:
- Oxalic acid (dehydrate) used at 1:1 weight ratio for the expected gold from solution.
(I use a slight excess Oxalic)- Dissolve in D. water, water level should not exceed one 1/3 height of the beaker.
- Raise pH with ammonia solution/NaOH to about 6.
- Heat both gold solution and Oxalic solution to near boil.
- SLOWLY add gold solution to oxalic solution, by slow i mean a few drop at a time with a glass pipette. The more concentrated your gold solution is the more vigorous the reaction is. (cover the oxalic beaker almost completely with a watch glass while adding the gold to contain splattering)
- When done adding the gold, give it a good stir with glass rod and keep the reaction beaker 10 more minutes on the hotplate at near boil.
- Remove beaker from heat and allow it to settle over night.
- the following day, Solution should be clear and colorless (assuming it is a second refining), test with SnCl. If negative, filter the solution and discard, if slightly positive, decant the solution to another beaker, add some SMB and let is sit for few more hours or over night.
- Wash gold powder: 3x water, 3x HCL, 3x D. water.
- Dry gold powder
- Melt
goldenchild said:Also, what is the smell like compared to the dreaded SMB stench?
Balanced:samuel-a said:Here is the reaction of oxalic acid with Chloroauric acid:
HAuCl4 + H2C2O4 = Au + CO2 + HCl
goldenchild said:I see. So it's a little more involved. I honestly don't see any advantages in using this method over SMB but it's cool to experiment. Again. Nice work 8)
samuel-a said:Hi, no i don't have acsess to xrf at the moment. Ican only guesstimate it at 99.95 or above...
I decided to go with oxalic this time mainly from interest and not necessety... Since it was a re-refining job, base metals presence was at minimum, and when melted, no crust or film was present.
samuel-a said:Hi Mario
I attached the procedure as i described it in the link above:
samuel-a said:step wise for Oxalic acid:
- Oxalic acid (dehydrate) used at 1:1 weight ratio for the expected gold from solution.
(I use a slight excess Oxalic)- Dissolve in D. water, water level should not exceed one 1/3 height of the beaker.
- Raise pH with ammonia solution/NaOH to about 6.
- Heat both gold solution and Oxalic solution to near boil.
- SLOWLY add gold solution to oxalic solution, by slow i mean a few drop at a time with a glass pipette. The more concentrated your gold solution is the more vigorous the reaction is. (cover the oxalic beaker almost completely with a watch glass while adding the gold to contain splattering)
- When done adding the gold, give it a good stir with glass rod and keep the reaction beaker 10 more minutes on the hotplate at near boil.
- Remove beaker from heat and allow it to settle over night.
- the following day, Solution should be clear and colorless (assuming it is a second refining), test with SnCl. If negative, filter the solution and discard, if slightly positive, decant the solution to another beaker, add some SMB and let is sit for few more hours or over night.
- Wash gold powder: 3x water, 3x HCL, 3x D. water.
- Dry gold powder
- Melt
The only differnce in this latest batch is that the pH was more loosely controlled.
And the Oxalic solution was added to the gold (i found it to be less violent reaction).
goldenchild said:Also, what is the smell like compared to the dreaded SMB stench?Balanced:samuel-a said:Here is the reaction of oxalic acid with Chloroauric acid:
HAuCl4 + H2C2O4 = Au + CO2 + HCl
2 HAuCl4 + 3 H2C2O4 = 2 Au + 6 CO2 + 8 HCl
In essence, you're looking at CO2 gas and HCl fumes (from heating).
If it is a re-refining job you would expect nothing less then a colorless solution when you are done, if dirty, then expect the respective color of your contaminate chloride.
Oxalic procedure
Pro:
- exelent purity.
- easy to handle end product.
- its cool to look at.
con:
- expensive.
- time consuming and labor intensive.
- voluminous waste solution.
HAuCl4 said:Not sure what the reaction is exactly, but it isn't that one. The reaction is with ammonium oxalate which is what you get by raising pH to 6 with ammonia. fwiw.
I understand completely - I thought for a more descriptive word for several minutes - there just isn't one! You can see it was winter - After precipitation had begun, I would add a couple of handfuls of clean snow to settle - don't remember if I did this time or not.samuel-a said:Thanks for the oxalate tip, HAuCl4.
HAuCl4 said:Not sure what the reaction is exactly, but it isn't that one. The reaction is with ammonium oxalate which is what you get by raising pH to 6 with ammonia. fwiw.
Now i'm not sure either.
I'm just playing around now with these equations... maybe a chemist could advise?
HAuCl4 + Na2C2O4 = Au + CO2 + HCl + NaCl
HAuCl4 + C2H8N2O4 = Au + CO2 + HCl + NH4Cl
Nice dtectr, i haven't seen this video... i guess the keyword here is "hypnotic" :mrgreen:
It really is....
And you got this effect using SMB? Cool.
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